Hydrogen generating system

Abstract

The system (1) for generating hydrogen gas comprises a reaction vessel (101) containing an aqueous solution (102), and a cathode (105) and an anode (107) disposed at least partially within the reaction vessel (101). The system (1) also comprises first and second ultrasonic transducers (215-220) that emit ultrasonic waves in the directions of the cathode (105) and the anode (107), respectively. Each ultrasonic transducer (215-220) is driven by a respective transducer driver (202) to optimize operation of the system (1) for generating hydrogen gas by ultrasonic electrolysis.

Description

[Technical Field]

[0001] The present invention relates to a system for producing hydrogen, and more particularly to a system for generating hydrogen from non-carbon-containing sources using electrolysis of aqueous solutions in combination with ultrasound. [Background technology]

[0002] Today, most hydrogen production in the United States (and other countries) uses natural gas reforming, which contributes to both CO2 and methane emissions, and almost all hydrogen use is in industrial settings. The U.S. Department of Energy's Hydrogen Shot™ initiative is addressing the challenge of clean hydrogen production, seeking to reduce the cost of clean hydrogen by 80%, to $1 per kilogram over 10 years. Clean hydrogen is critical to reaching net zero by 2050. However, achieving this goal requires further research and development in the field of clean hydrogen.

[0003] With the current trend of using environmentally friendly energy to reduce carbon dioxide emissions in all power-consuming industries, the transition to green energy production is a focus of various energy production industries, academic institutions, and even governments. However, renewable green energy production comes with its own set of challenges. The innovative and educational ideas presented herein are potential solutions to some of these challenges in the energy industry.

[0004] Currently, the world relies heavily on fossil fuels to meet its energy needs, and reducing carbon dioxide emissions requires the use of alternative energy sources to these fossil fuels.

[0005] One alternative to fossil fuels is hydrogen, but its production, storage, transportation, and consumption present various challenges.

[0006] Hydrogen can be produced by splitting water molecules into hydrogen and oxygen, which are collected on separate electrodes using the process of electrolysis. Electrolysis is a process that involves passing an electric current through an aqueous solution to create a chemical reaction that either separates the solution into its components or produces a desired chemical product.

[0007] Two electrodes are immersed in an aqueous solution, such as an electrolyte solution (a solution containing a conductive substance). The electrodes are usually made of an inert material (such as graphite, platinum, or stainless steel) that is connected to a power source, such as a DC current source. The elements in the solution are split into positive and negative ions that can be collected by the electrodes. Positive ions collect at the negative electrode (cathode) and negative ions collect at the positive electrode (anode). Electrolysis of water results in a decomposition reaction in which individual water molecules break down into hydrogen and oxygen ions.

[0008] At the anode, an oxidation reaction occurs. The oxidation "half-reaction" is:

[0009] [ka]

[0010] A reduction reaction occurs at the cathode. The reduction "half-reaction" is:

[0011] [ka]

[0012] Therefore, the reaction for the electrolysis of water is as follows:

[0013] [ka]

[0014] Hydrogen ions (H+) collect at the cathode (-) and hydroxide ions (OH-) collect at the anode (+). Thus, electrolysis of water (HO) produces hydrogen gas (H2) and oxygen gas (O2). An ionic solution (electrolyte) is preferably, but not necessarily, dissolved in the water to facilitate the electrolysis reaction. An electrolyte is a solution that is electrically conductive and contains ions. The composition of the electrolyte depends on the specific application of the electrolysis process.

[0015] In conventional aqueous electrolysis, the electrolyte used is a solution of salt or acid dissolved in water. In conventional water electrolysis, the electrolyte can be either a dilute solution of sulfuric acid (H2SO4) or sodium hydroxide (NaOH) in water.

[0016] The anode is connected to the positive terminal of the power supply, so it is positively charged. Conversely, the cathode is connected to the negative terminal of the power supply, so it is negatively charged. An electric field is formed between the anode and the cathode in the direction from the anode to the cathode.

[0017] In an electric field, positive charges experience an accelerating force in the direction of the field, and negative charges experience an accelerating force in the opposite direction to the field. These forces cause ions in the aqueous solution to flow toward the anode and cathode, essentially accelerating the electrolytic reaction.

[0018] For example, in a sodium hydroxide (NaOH) solution, positively charged sodium ions (Na + ) experiences a force that accelerates positive ions toward the cathode, while hydroxide (OH - ) negative ions are accelerated towards the anode. When the hydroxide ions come into contact with the anode, they are oxidized by releasing an extra electron, which flows through an external circuit, resulting in the production and release of oxygen gas (O2) at the anode. At the cathode, H+ ions are converted into Na + H+ ions discharge more easily than sodium (Na + ) instead of discharging. Therefore, the reduction of water molecules is the more favorable reaction, and H+ ions are reduced to hydrogen gas (H2).

[0019] Within a water molecule, covalent bonds are formed by the sharing of electrons between atoms. Each water molecule consists of two hydrogen atoms individually covalently bonded to an oxygen atom. These covalent bonds involve the sharing of electrons between the oxygen and hydrogen atoms, creating a stable molecular structure. The polar covalent bond between the oxygen and hydrogen atoms in each water molecule is shown by the solid line in Figure 1 of the accompanying drawings.

[0020] The energy stored within a covalent bond, known as the bond dissociation energy, represents the amount of energy required to break the bond and separate the atoms. For a water molecule, the bond dissociation energy for each O-H covalent bond is approximately 460 kilojoules per mole (kJ / mol), which indicates the strength of the bond and the energy required to weaken / break it.

[0021] To break a water molecule (HO) into its components, the bond dissociation energy is approximately 460 kJ / mol for each O-H bond. Because water has two O-H bonds, the total energy required to break one water molecule into hydrogen and oxygen is approximately 920 kJ / mol. One mole of water weighs 18 grams.

[0022] On the other hand, hydrogen bonds form between a partially positive hydrogen atom of one water molecule and a partially negative oxygen atom of an adjacent water molecule. Due to the high electronegativity of oxygen, the oxygen atom attracts the shared electrons of the O-H bond, creating a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atom. This polarity allows the water molecules to form high surface tension and cohesion. The hydrogen bonds between water molecules are shown by dotted lines in Figure 1.

[0023] The energy required to break a hydrogen bond in water can range from 5 kJ / mol to 30 kJ / mol. This energy requirement is significantly lower than the approximately 460 kJ / mol required to break the covalent O-H bond within a water molecule.

[0024] While the conventional production of hydrogen gas is a simple theoretical process, in the past it has been slow and energy-intensive, making the product (hydrogen gas), despite being a clean-burning fuel, expensive and unsustainable as an economically viable alternative to fossil fuels. Conventional electrolysis processes consume large amounts of energy in splitting water into hydrogen and oxygen ions. To achieve sustainable and consistent availability of hydrogen as a fuel, methods to reduce energy consumption are needed.

[0025] In some electrolysis applications, ultrasound can be used to enhance the process. This is known as ultrasonic electrolysis or ultrasound-assisted electrolysis. While ultrasound improves the efficiency of electrolysis, conventional systems that use ultrasound are often not optimized to take into account the different temperatures and properties of aqueous solutions.

[0026] Furthermore, the electrodes used in the water electrolysis process deteriorate as the reaction proceeds, necessitating downtime between electrode replacements and resulting in frequent replacement of metal electrodes. This increases the overall running costs of the process, making it economically unfeasible. The deterioration of electrode materials also results in an increase in the energy consumed to produce a similar amount of hydrogen gas compared to using fresh electrodes.

[0027] Therefore, to reduce the cost and energy required to achieve a sustainable and consistent supply of hydrogen as a fuel, improvements in materials for components used in the electrolysis process to obtain hydrogen are needed with respect to their durability to withstand the harsh electrolysis conditions.

[0028] Therefore, there is a need in the art for a more environmentally friendly hydrogen gas generation system that seeks to address at least some of the problems described herein. Summary of the Invention

[0029] The present invention provides systems as claimed in claims 1, 2 and 19. The present invention also provides preferred embodiments as claimed in the dependent claims.

[0030] Example systems of the present disclosure have significant environmental benefits by reducing the energy required to generate hydrogen gas, thereby reducing the cost of producing hydrogen gas.

[0031] A further advantage of the example systems of the present disclosure is that the systems can directly use wastewater or seawater as an aqueous solution without the need to desalinate the seawater, which avoids the need for energy-intensive and costly desalination. [Brief explanation of the drawings]

[0032] In order that the present disclosure may be more readily understood, preferred embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 illustrates the bonds within and between water molecules in an aqueous solution. [Figure 2] 1 is a schematic diagram of some example systems of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of a reaction vessel and components of some example systems of the present disclosure. [Figure 4] FIG. 1 is a schematic diagram of a reaction vessel and components of some example systems of the present disclosure. [Figure 5] FIG. 1 is a schematic diagram of a reaction vessel and components of some example systems of the present disclosure. [Figure 6] FIG. 1 is a schematic diagram of a reaction vessel and components of some example systems of the present disclosure. [Figure 7] 1 is a schematic diagram of the placement of ultrasound transducers around electrodes in some example systems of the present disclosure. [Figure 8] 1 is a schematic diagram of the placement of ultrasound transducers around electrodes in some example systems of the present disclosure. [Figure 9]1 is a schematic diagram of a transducer holder and an ultrasound transducer of some example systems of the present disclosure. [Figure 10] FIG. 1 is a schematic diagram of a reaction vessel and components of some example systems of the present disclosure. [Figure 11] 1 shows a table of relationships between dimensions of components of several example systems of the present disclosure. [Figure 12] FIG. 2 is a schematic diagram of a membrane electrode assembly of some example systems of the present disclosure. [Figure 13] 1 is a schematic perspective view of some example systems of the present disclosure. FIG. [Figure 14] FIG. 14 is a schematic side view of the system of FIG. 13. [Figure 15] FIG. 14 is a cross-sectional side view of the system of FIG. 13. [Figure 16] FIG. 14 is a cross-sectional view of the system of FIG. 13. [Figure 17] FIG. 1 is a schematic perspective view of an array system according to some examples of the present disclosure. [Figure 18] 1 is a schematic diagram of an integrated circuit configuration of the present disclosure. [Figure 19] 1 is a schematic diagram of an integrated circuit of the present disclosure. [Figure 20] FIG. 1 is a schematic diagram of a pulse width modulation generator of the present disclosure. [Figure 21] FIG. 1 is a timing diagram of an example of the present disclosure. [Figure 22] FIG. 1 is a timing diagram of an example of the present disclosure. [Figure 23] 1 is a table illustrating example port functions of the present disclosure. [Figure 24] 1 is a schematic diagram of an integrated circuit of the present disclosure. [Figure 25] FIG. 1 is a circuit diagram of an example H-bridge of the present disclosure. [Figure 26] FIG. 1 is a circuit diagram of an example current sensing configuration of the present disclosure. [Figure 27] FIG. 1 is a circuit diagram of an example H-bridge of the present disclosure. [Figure 28] 26 is a graph showing voltages during phases of operation of the H-bridge of FIG. 25. [Figure 29]26 is a graph showing voltages during phases of operation of the H-bridge of FIG. 25. [Figure 30] 26 is a graph showing the voltage and current at the terminals of an ultrasonic transducer while the ultrasonic transducer is driven by the H-bridge of FIG. 25. [Figure 31] FIG. 1 is a schematic diagram illustrating connections between integrated circuits of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0033] Aspects of the present disclosure are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, according to standard practice in the industry, various features have not been drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or decreased for clarity of illustration.

[0034] The following disclosure provides many different embodiments or examples for implementing different features of the provided subject matter. To simplify the disclosure, specific examples of components, concentrations, applications, and configurations are described below. Of course, these are merely examples and are not intended to be limiting. For example, the attachment of a first feature and a second feature in the following description may include embodiments in which the first feature and the second feature are attached in direct contact, or may also include embodiments in which an additional feature may be disposed between the first feature and the second feature such that the first feature and the second feature do not need to be in direct contact. Additionally, the present disclosure may repeat reference numerals and / or letters in various examples. This repetition is for purposes of brevity and clarity and does not, in itself, dictate a relationship between the various embodiments and / or configurations discussed.

[0035] The following disclosure describes representative examples, each of which may be considered an embodiment, and any reference to "example" may be changed to "embodiment" in this disclosure.

[0036] 2 of the accompanying drawings, a system 1 for producing hydrogen gas comprises a main controller 2. The main controller 2 coordinates the operation of components within the system 1 to optimize the operation of the system 1 for producing hydrogen gas. In some examples, the main controller 2 comprises a computing device having a processor and non-transitory memory for executing instructions.

[0037] Referring to FIG. 3 of the accompanying drawings, an example system 1 of the present disclosure includes a reaction vessel 101 containing an aqueous solution 102 .

[0038] In some examples of the present disclosure, the aqueous solution 102 is water. In other examples of the present disclosure, the aqueous solution 102 is an electrolyte solution containing an electrolyte, such as sodium hydroxide. In further examples of the present disclosure, the aqueous solution 102 is wastewater or seawater. If seawater is used, the seawater does not need to be desalinated for use in the systems of the examples of the present disclosure. However, if seawater is used as an electrolyte in the electrolysis process, other chemicals may be added to accelerate the rate of hydrogen production, depending on the properties of the seawater.

[0039] In some instances, sodium hydroxide (NaOH) may be added to increase the pH of the seawater, which promotes the formation of hydroxide ions and enhances the extraction of hydrogen gas during electrolysis. In other instances, optional additives such as sodium hydroxide or other chemicals are omitted.

[0040] In this example, reaction vessel 101 is cylindrical and includes curved sidewalls 103, although other shapes and configurations of reaction vessels suitable for the intended purpose are contemplated and within the scope of the present invention. Reaction vessel 101 includes a flat or planar base 104. In this example, base 104 is circular and has a diameter equal to or substantially equal to the height of sidewalls 103. Thus, in this example, reaction vessel 101 has a height-to-diameter ratio of 1:1.

[0041] The shape of the reaction vessel 101 in this example promotes the formation and collapse of cavitation bubbles during electrolysis while effectively mixing the aqueous solution 102 .

[0042] The shape of the reaction vessel 101 affects the efficiency and effectiveness of the system in performing electrolysis. The optimal shape of the reaction vessel 101 depends on various factors, the properties of the aqueous solution 102, and the geometry of the electrodes. In some examples, the optimal shape of the reaction vessel 101 is a cylinder with a diameter to height ratio of 1:1.

[0043] The advantages of using a cylindrical reaction vessel with a 1:1 diameter to height ratio include:

[0044] Reduction of current path length: In a cylindrical reactor with a diameter-to-height ratio of 1:1, the distance between the electrodes is minimized. This shorter current path length reduces the resistance that ions encounter while migrating toward the electrodes, improving mass transport efficiency and electrolysis rate.

[0045] Efficient bubble release: The cylindrical shape facilitates the release and removal of bubbles generated during electrolysis. The vertical orientation of the cylinder allows the bubbles to naturally rise to the top, minimizing the possibility of bubble buildup and blockage near the electrodes. This promotes continuous electrolysis and helps maintain stable and efficient operation.

[0046] Scalability: Cylindrical vessels with a 1:1 ratio are relatively easy to manufacture. Cylindrical vessels can be easily implemented in a variety of sizes to accommodate larger electrolysis setups. Furthermore, the cylindrical shape simplifies the design and construction of the support structure, ensuring practicality and ease of operation.

[0047] The reaction vessel 101 includes a cathode 105 disposed at least partially within the reaction vessel 101. A portion of the cathode 105 has an exterior surface 106 immersed in and in electrical contact with the aqueous solution 102 to provide an interface for a reduction reaction to reduce H+ ions to produce hydrogen gas at the cathode 105.

[0048] The reaction vessel 101 includes an anode 107 at least partially disposed within the reaction vessel 101. A portion of the anode 107 has an exterior surface 108 immersed in and in electrical contact with the aqueous solution 102 to provide an interface for an oxidation reaction to oxidize OH − ions to produce oxygen gas at the anode 107.

[0049] The cathode 105 and the anode 107 are disposed within the reaction vessel 101 spaced apart from each other and from the sidewall 103. In this example, the cathode 105 and the anode 107 are parallel or generally parallel to the sidewall 103 so that the cathode 105 and the anode 107 stand vertically within the reaction vessel 101.

[0050] Cathode 105 and anode 107 are configured to receive power from a power source (not shown). In this example, cathode 105 is electrically coupled to the negative terminal of the power source, such as a DC power source. Anode 107 is electrically coupled to the positive terminal of the power source. In this example, the power source is a battery, but in other examples, the power source is a different type of DC power source, such as an AC-to-DC power adapter.

[0051] Electrons flow from the negative terminal of the power supply to the cathode 105. The electrons then flow through the aqueous solution 102 to the anode 107 and from the anode 107 to the positive terminal of the power supply.

[0052] During electrolysis, water undergoes: 1. A reduction reaction at the cathode in which H+ ions are reduced (accept electrons) to form hydrogen gas (H2) which is released. 2. An oxidation reaction at the anode, in which OH- ions donate their extra electrons to the anode and gas (O2) is produced and released.

[0053] In some embodiments, the example system 1 includes a polymer electrolyte membrane (PEM) 109 disposed between the cathode 105 and the anode 107 to separate H+ and OH- ions in the aqueous solution 102 to create divided regions 110, 111 in the reactor 101. The aqueous solution 102 in the divided region 110 adjacent to the cathode 105 has a higher concentration of H+ ions than OH- ions.

[0054] The PEM 109 is a proton exchange membrane, preferably made of a perfluorosulfonic acid-based material or similar proton-conducting polymer. An example of a PEM is commercially available from The Chemours Company FC, LLC. (Wilmington, Delaware, USA) under the trademark Nafion™. The PEM 109 conducts protons (H+ ions) and blocks the passage of electrons. To take advantage of this property of the polymer, the PEM 109 separates the cathode 105 and anode 107 and is positioned to facilitate the splitting of water into hydrogen and oxygen.

[0055] An advantage of incorporating a PEM is that the PEM allows system 1 to operate at relatively low temperatures, while accelerating hydrogen production through separation of ions within aqueous solution 102 for faster reduction at cathode 105. Separating H+ and O− ions also prevents the ions from recombining within aqueous solution 102, which further increases the efficiency of system 1 in producing hydrogen gas.

[0056] Polymer electrolyte membrane water electrolysis (PEMWE) utilizes a sulfonated polymer membrane as the electrolyte. Typically, PEM water electrolysis is performed at lower temperatures (30-80°C) and higher current densities (1-2 A / cm). 2 ) and produces gases of exceptional purity (99.999%), namely hydrogen and oxygen.

[0057] PEM electrolysis does not require caustic electrolyte, occupies minimal space, and is safer than traditional alkaline electrolysis.

[0058] In a PEMWE, the oxygen produced is removed from the surface of the anode 107, while the remaining protons (H+) cross the proton-conducting membrane toward the cathode 105. Simultaneously, electrons travel through an external circuit to reach the cathode 105. At the cathode 105, the protons and electrons recombine to generate hydrogen gas.

[0059] To further increase the rate of hydrogen gas production, in some examples, the system 1 may include a polymer electrolyte membrane (PEM) and multiple ultrasonic transducers positioned at optimal locations within the aqueous solution 102. For example, the ultrasonic transducers may be positioned near the anode 107 and / or cathode 105, while leaving enough space for the aqueous solution 102 to easily flow around the anode 107 and / or cathode 105. Alternatively, or in addition, the ultrasonic transducers may be positioned near the edge of the reaction vessel 101 to agitate the aqueous solution 102 and move ions toward the anode 107 and / or cathode 105.

[0060] However, the PEM 109 is optional, not required, and may be omitted in other examples of the present disclosure. For example, Figure 4 of the accompanying drawings shows the system 1 without the optional PEM 109.

[0061] 3, in the example described above, the electrodes 105, 107 are rod electrodes of circular cross section. The electrodes 105, 107 are inserted into the aqueous solution 102 through the top wall 112 of the reaction vessel 101.

[0062] In some examples, electrodes 105, 107 are each flat rectangular electrodes positioned parallel to and spaced apart from each other within reaction vessel 101.

[0063] In some cases, the electrodes (anode / cathode) may have different electrode geometries depending on the intended application. For example, the electrodes may be flat, elongated plates. This geometry also disrupts any steady laminar flow within the electrolyte, creating turbulent vortices and increasing interactions between water molecules and the electrodes.

[0064] Other electrode geometries for the electrodes (anode / cathode) of some examples of the present disclosure include, but are not limited to, M-shaped electrodes (increases surface area) (similar to a heat sink), mesh electrodes (increases surface area), or porous electrodes (improves gas diffusion, mass transport).

[0065] In another example, electrodes 105, 107 are each mesh or screen electrodes comprised of a mesh or screen structure made of a conductive material. These mesh or screen electrodes may be positioned vertically on the inner surface of reaction vessel 101. It is understood that various configurations and shapes of electrodes suitable for the intended purpose of electrolysis are contemplated and within the scope of the present invention. Some examples include, but are not limited to, planar and coil-shaped electrodes.

[0066] The electrodes 105, 107 may be affected by chemicals in the aqueous solution 102. The choice of electrode material depends on various factors, such as the chemical reaction to be carried out, the properties of the aqueous solution, and the desired durability and efficiency of the electrodes.

[0067] In some examples, the cathode 105 and the anode 107 are made of graphite, platinum, or preferably stainless steel. In some examples, the cathode 105 and the anode 107 are solid electrodes, while in other examples, the cathode 105 and the anode 107 are each open (tubular) or porous. The structure of the cathode 105 and the anode 107 is selected according to the required application and operating parameters of the system 1. Platinum electrodes are generally corrosion-resistant and durable, and are less likely to degrade during water electrolysis. However, platinum electrodes degrade over time and / or under harsh conditions, such as when exposed to high current densities. To minimize or prevent degradation of the cathode 105 and the anode 107 during electrolysis, the cathode 105 and the anode 107 may be coated with a material that promotes better performance and lifespan.

[0068] In some examples, the cathode 105 and the anode 107 are coated with graphene to minimize or prevent degradation of the cathode 105 and the anode 107. This coating not only prevents degradation of the cathode 105 and the anode 107, but also improves the electrical performance of the cathode 105 and the anode 107.

[0069] Graphene, a two-dimensional material, is a single layer of carbon atoms arranged in a hexagonal lattice structure, and its chemical stability makes it resistant to corrosion. Furthermore, graphene's high electrical conductivity improves the overall efficiency of the cathode 105 and anode 107 during the electrolysis process. The electrical conductivity is improved due to the availability of free electrons within the graphene lattice, which has a hexagonal crystal structure. The presence of a Dirac cone in graphene's electronic band structure indicates the quality of its electrical properties.

[0070] The electronic structure of graphene contains two conical energy bands that intersect at two distinct points (Dirac cones / Dirac points) that represent the electron energy dispersion relation. This energy dispersion relation is the product of the reduced Planck constant, the Fermi velocity, and the electron momentum. The linear relationship between energy and momentum allows electrons to move with high mobility, demonstrating the material's excellent electrical conductivity and resulting in higher current densities that can be handled without degradation to the electrode.

[0071] Coating the cathode 105 and anode 107 with graphene increases the lifespan of the cathode 105 and anode 107 due to graphene's strong resistance to corrosion in harsh chemical and electrical environments. The graphene coating also increases the electrical conductivity properties of the cathode 105 and anode 107 for more efficient operation of the system in electrolyzing water to generate hydrogen gas.

[0072] Another example of a coating material is gold nanoparticles, a two-dimensional material consisting of a single layer of gold atoms. Gold nanoparticles offer similar advantages to graphene. Additionally, gold nanoparticle-based plasmonic photocatalysts, driven by localized surface plasmon resonance excitation of gold nanoparticles (Au NPs), can be efficient solar-to-chemical converters due to their broad spectral response, making them useful in plasmonic water splitting and the synthesis of H2O2 from water and oxygen (O2).

[0073] A hydrogen gas collector 113 extends through the top wall 112 of the reaction vessel 101 and is positioned above the cathode 105 to collect hydrogen gas produced during electrolysis. An oxygen gas collector 114 extends through the top wall 112 of the reaction vessel 101 and is positioned above the anode 107 to collect oxygen gas evolved during electrolysis. In this example, the hydrogen gas collector 113 and the oxygen gas collector 114 are identical or substantially identical to one another, and for simplicity, only the elements of the hydrogen gas collector 113 will be described below. In other examples, the hydrogen gas collector 113 and the oxygen gas collector 114 may be different sizes and / or shapes suitable for the intended purpose of collecting the respective gases.

[0074] The hydrogen gas collector 113 is generally elongated and has a closed end 115 and an open end 116. The hydrogen gas collector 113 preferably includes an inner chamber 117.

[0075] The cathode 105 is partially inserted through the open end 116 of the hydrogen gas collector 113 so that hydrogen gas evolved from around the cathode 105 during electrolysis rises within the hydrogen gas collector 113 and enters the inner chamber 117. Thus, the hydrogen gas is collected by the hydrogen gas collector 113.

[0076] Conversely, the oxygen gas collector 114 collects oxygen gas released from the surroundings of the anode 107 .

[0077] The hydrogen gas collector 113 includes a hydrogen gas outlet 118 that allows hydrogen gas to exit the hydrogen gas collector 113 for use or storage. In some examples, the hydrogen gas outlet 118 communicates the hydrogen gas to a storage tank so that the hydrogen gas can be stored for later use. In other examples, the hydrogen gas outlet 118 communicates the hydrogen gas to a fuel cell or alternatively a burner so that the produced hydrogen gas can be utilized in real time or near real time, minimizing or avoiding the need to store significant amounts of the produced hydrogen gas.

[0078] The oxygen gas collector 114 includes an oxygen gas outlet 119 that allows oxygen gas to exit the oxygen gas collector 114 for use or storage. In some examples, the oxygen gas outlet 119 communicates the oxygen gas to a storage tank so that the oxygen gas can be stored for later use. In other examples, the oxygen gas outlet 119 communicates the oxygen gas to additional systems so that the produced oxygen gas can be utilized in real time or near real time, minimizing or avoiding the need to store large amounts of the produced oxygen gas.

[0079] The hydrogen gas collector 113 preferably includes a pressure sensor 120 in the flow path from the hydrogen gas collector 113 for sensing the pressure of the hydrogen gas exiting through the hydrogen gas outlet 118. The hydrogen gas pressure sensor 120 generates a hydrogen gas pressure signal and communicates the hydrogen gas pressure signal to the main controller 2. The main controller 2 uses the hydrogen gas pressure signal to calculate the volume and rate of hydrogen gas produced by the system 1. The hydrogen gas pressure signal therefore forms part of a feedback loop within the system 1 that enables the main controller 2 to monitor the output of hydrogen gas and determine the operating efficiency of the system 1.

[0080] In this example, the configuration of the oxygen gas collector 114 is the same as that of the hydrogen gas collector 113, but the oxygen gas collector 114 collects oxygen gas released from around the anode 107 during electrolysis.

[0081] In this example, an oxygen gas pressure sensor 121 is provided in the flow path from the oxygen gas collector 114 and senses the pressure of the oxygen gas exiting through the oxygen gas outlet 119. The oxygen gas pressure sensor 121 generates an oxygen gas pressure signal and communicates the oxygen gas pressure signal to the main controller 2. The main controller 2 uses the oxygen gas pressure signal to calculate the volume and rate of oxygen gas produced by the system 1. The oxygen gas pressure signal therefore forms part of a feedback loop within the system 1 that enables the main controller 2 to monitor the output of oxygen gas and determine the operating efficiency of the system 1.

[0082] Gas pressure sensors 120, 121 provide useful feedback to main controller 2, although one or both of hydrogen gas pressure sensor 120 and / or oxygen gas pressure sensor 121 may be omitted in other examples of the present disclosure.

[0083] The system 1 is positioned at a predetermined distance S from the cathode 105. t-eThe cathode 105 includes an ultrasonic transducer 215 disposed on the outer surface 106 of the cathode 105. The ultrasonic transducer 215 is oriented such that the ultrasonic transducer 215 emits ultrasonic waves at least partially toward the outer surface 106 of the cathode 105 to agitate the aqueous solution 102 adjacent to the outer surface 106 of the cathode 105, remove hydrogen gas bubbles formed on the outer surface 106 of the cathode 105, and expose the outer surface 106 of the cathode 105 to additional H ions to generate hydrogen gas. In some examples, the ultrasonic transducer 215 emits ultrasonic waves that induce cavitation within the aqueous solution 102 adjacent to the outer surface 106 of the cathode 105.

[0084] In this example, the system 1 is positioned at a predetermined distance S from the cathode 105. t-e The cathode 105 includes a plurality of additional ultrasonic transducers 216, 217 disposed at positions adjacent to the outer surface 106 of the cathode 105. In this example, there are two additional ultrasonic transducers 216, 217. The plurality of additional ultrasonic transducers 216, 217 are oriented such that the plurality of additional ultrasonic transducers 216, 217 emit ultrasonic waves at least partially toward the outer surface 106 of the cathode 105 to agitate the aqueous solution 102 adjacent to the outer surface 106 of the cathode 105, remove hydrogen gas bubbles formed on the outer surface 106 of the cathode 105, and expose the outer surface 106 of the cathode 105 to additional H ions to generate hydrogen gas. In some examples, the ultrasonic transducers 216, 217 emit ultrasonic waves that induce cavitation in the aqueous solution 102 adjacent to the outer surface 106 of the cathode 105.

[0085] In other examples, the plurality of further ultrasonic transducers 216, 217 are omitted. In further examples, the system 1 comprises more than the two further ultrasonic transducers 216, 217 shown in FIG.

[0086] In another example, the ultrasonic transducers 215-217 on the cathode side of the reaction vessel 101 are completely omitted, for example as shown in FIG.

[0087] In this example, the system 1 is positioned at a predetermined distance S from the anode 107.t-e The anode 107 includes at least one or more anode ultrasonic transducers 218-220, each disposed at a location on the anode 107. In this example, there are three anode ultrasonic transducers 218-220. The anode ultrasonic transducers 218-220 are oriented so that the anode ultrasonic transducers 218-220 emit ultrasonic waves at least partially toward the outer surface 108 of the anode 107, causing cavitation in the aqueous solution 102 adjacent to the outer surface 108 of the anode 107. The cavitation weakens the hydrogen bonds between water molecules in the aqueous solution 102, separating individual water molecules available for interaction with the anode 107, and undergoes an oxidation reaction at the anode 107, oxidizing OH ions and forming oxygen gas at the anode 107.

[0088] In some examples, the system 1 includes more or fewer anode ultrasonic transducers than the three anode ultrasonic transducers 218-220 shown in Figure 3. In other examples, the anode ultrasonic transducers 218-220 are omitted entirely, as shown in Figure 6, for example.

[0089] For simplicity, the following description will refer to one ultrasonic transducer 215 and how that ultrasonic transducer 215 is driven by the transducer driver 202. However, the description applies equally to any other ultrasonic transducer that operates similarly to the ultrasonic transducer 215 to create cavitation in the aqueous solution 102.

[0090] During electrolysis, the introduction of ultrasound into the aqueous solution 102 agitates the solution and increases the collision rate between H+ and the cathode 105. Ultrasound is transmitted through the aqueous solution 102, creating agitation and cavitation bubbles. The efficiency of the electrolysis process that uses water to produce hydrogen gas can be improved by the addition of ultrasound.

[0091] In examples of the present disclosure, at least one ultrasonic transducer is preferably driven at a frequency within the frequency range of 20 kHz to 40 kHz to induce convection and agitation within the aqueous solution 102. In other examples of the present disclosure, the ultrasonic transducer is driven at different frequencies depending on the desired result.

[0092] The advantages of transmitting ultrasound through the aqueous solution 102 include: 1. Ultrasound creates a stirring effect, increasing the reaction rate and therefore the mass flow rate to the anode 105 and / or cathode 107. This also ensures homogeneous mixing of all components of the aqueous solution 102 in the reaction vessel 101. 2. The stirring effect also regulates the temperature of the entire aqueous solution 102, facilitating lower operating temperatures. 3. Removal / release of air bubbles that may adhere to the anode and / or cathode. Air bubbles that remain on the anode and / or cathode reduce the exposed surface area of ​​the anode / cathode, slowing down the reaction rate. 4. The formation and collapse of cavitation bubbles generates localized shock waves with energies ranging from 500 to several thousand joules, which further increase the reaction rate by weakening / breaking hydrogen bonds between adjacent water molecules.

[0093] The ultrasound induces localized cavitation bubbles near the exterior surface of the cathode / anode, which, upon implosion, release energy in the form of microjets into the aqueous solution 102. In addition to agitating the aqueous solution 102, the microjets from the cavitation weaken or break hydrogen bonds in the water molecules in the aqueous solution 102. This facilitates the rapid decomposition of the water molecules into H and OH ions, which contact the cathode / anode and are reduced and oxidized to produce hydrogen and oxygen gases at the cathode 105 and anode 107, respectively.

[0094] Increased contact of the H+ ions with the cathode 105 accelerates the rate of the electrolysis process, producing a greater amount of hydrogen gas per unit time (while consuming less power for the same amount of hydrogen production compared to conventional methods). Furthermore, optimal placement of the vessel geometry and cathode 105 to maximize contact with the H+ ions in the aqueous solution 102 also increases the output of hydrogen gas produced.

[0095] In other examples of the present disclosure, the system 1 drives at least one ultrasonic transducer in the aqueous solution 102 at a higher frequency, for example, 3 MHz to 20 MHz, preferably 10 MHz. The at least one ultrasonic transducer is preferably positioned near the top surface of the aqueous solution 102 to facilitate sonolysis of water molecules in the aqueous solution 102. At higher frequencies in the range of 3 MHz to 20 MHz or higher, the ultrasound emitted from each ultrasonic transducer performs sonolysis, breaking down water molecules in the aqueous solution and generating hydrogen gas directly from the water. In these examples, the sonolysis performed by each ultrasonic transducer may be performed instead of or in addition to electrolysis to maximize the yield of hydrogen gas.

[0096] In some examples, the ultrasonic transducer is positioned concentrically or nearly concentrically with the open end 116 of the hydrogen gas collector 113. The ultrasonic transducer is positioned to emit ultrasonic waves in a direction toward the cathode 105. In this example, the direction of the ultrasonic waves emitted by the ultrasonic transducer 215 is aligned with the longitudinal length of the cathode 105.

[0097] In some examples, the ultrasonic transducer 215 is an ultrasonic horn (sonotrode), which can deliver high frequency and high intensity ultrasonic waves for use in industrial systems for generating hydrogen.

[0098] In some examples, the ultrasonic horn is a Barbell Horn™. Barbell Horns™ can amplify ultrasonic amplitude while maintaining a large output diameter and radiating area. Examples of Barbell Horns™ are disclosed in U.S. Patent No. 1,325,094, which is incorporated herein by reference.

[0099] In some examples, the ultrasonic horn is a rod horn, which includes a solid metal rod having a circular cross section and a longitudinal cross section of variable shape, hi other examples, the ultrasonic horn is a block horn, which includes a rectangular cross section and a longitudinal cross section of variable shape.

[0100] The main controller 2 is electrically connected to a power controller (not shown) that controls the power (electrode potential difference) applied between the cathode 105 and the anode 107 during electrolysis. The main controller 2 operates the power controller to supply power to the cathode 105 and the anode 107 to initiate the electrolysis reaction, and controls the level of power to vary the rate of the electrolysis reaction.

[0101] The main controller 2 also stops the power controller to stop the electrolysis reaction.

[0102] The main controller 2 is also electrically coupled to the transducer driver 202 to initiate and control operation of the transducer driver 202. The transducer driver 202 is electrically coupled to the ultrasonic transducer 215 to drive the ultrasonic transducer 215 to generate ultrasonic waves. In examples where the system includes multiple ultrasonic transducers, the system 1 includes multiple transducer drivers 202, each electrically coupled to control a respective one of the ultrasonic transducers. In further examples, the system includes a transducer driver incorporating multiple outputs electrically coupled to the multiple ultrasonic transducers to respectively drive the ultrasonic transducers to generate ultrasonic waves. For simplicity, the following description will refer to only one transducer driver 202 coupled to only one ultrasonic transducer 215.

[0103] The main controller 2 coordinates the level of power delivered to the cathode 106 and anode 107 with the operation of the transducer driver 202 to optimize the operation of the system 1 to produce hydrogen gas.

[0104] The placement of ultrasonic transducer 215 (and similarly other ultrasonic transducers 216-220) is an important factor in controlling the rate of the electrolytic reaction. Transducers placed closer to the cathode / anode increase the efficiency of mechanical agitation around the cathode / anode, increasing the reaction rate.

[0105] Furthermore, the transducer placement also determines the region of cavitation bubble formation and collapse. Cavitation bubble implosion generates a localized shock wave adjacent to the cathode / anode, facilitating efficient and accelerated bubble ejection from the cathode / anode surface. Consistent agitation and convection also ensure that there is no stagnation in the aqueous solution and that all molecules / ions flow to the cathode / anode.

[0106] Each ultrasonic transducer is positioned according to where it will create a region of active cavitation bubble formation and collapse, with the goal being to ensure that the cavitation bubble formation region is in close proximity to the surface of the cathode / anode.

[0107] Cavitation bubbles usually form in the rarefied regions of ultrasound (longitudinal mechanical waves). In the rarefied regions, particles / layers of the medium (electrolyte) are stretched apart, creating voids (cavitation bubbles). With each wave pass, the cavitation bubbles in the rarefied regions grow to a size that is no longer sustainable due to the pressure difference between the outside and inside of the bubble.

[0108] This enormous pressure difference then causes the bubble to instantly implode, creating localized conditions of up to 200 atmospheres and 5000°K (since these conditions are on an infinitesimal scale, the dissipation rate is 10 -4 °Ks -1 The violent implosion of the cavitation bubbles also releases shock waves that travel through the medium (water) and induce microjets. These microjets shake the bubbles off the electrode, continuously maximizing the exposed surface area for increased reaction rates.

[0109] Ultrasonic intensity (Wcm -2 The distance (measured in Hz) decreases by a factor of two on average as the electrode moves away from the transducer. Thus, in some instances, the spacing between the transducer and electrode is maintained close to one wavelength of ultrasound. In other instances, the spacing between the transducer and electrode is maintained close to a multiple of one wavelength of ultrasound.

[0110] To determine the wavelength of ultrasound, the following formula is used:

[0111]

number

[0112] To determine the velocity of ultrasound in water (an electrolyte), the following equation is used:

[0113]

number

[0114] The preferred range for ultrasound transmission in system 1 is set to 20 kHz to 40 kHz, so the range of wavelengths can be found by calculating the minimum and maximum wavelength values.

[0115]

number

[0116] Therefore, for a frequency range of 20 kHz to 40 kHz, the one wavelength placement distance between the anode / cathode and the transducer is 37 mm to 74 mm.

[0117] In other examples, each transducer is spaced farther than one wavelength from the anode / cathode. In some examples, such as but not limited to, for use in industrial environments, each transducer is spaced farther from the anode / cathode by a distance equal to or substantially equal to multiple wavelengths of the ultrasonic waves emitted by the ultrasonic transducer.

[0118] The wavelength is related to the frequency of the ultrasound. Each ultrasound transducer may be spaced from the anode / cathode by one or two ultrasound wavelengths depending on the ultrasound intensity (input power). If the ultrasound transducer is operated at a higher power, the ultrasound intensity will be higher and the positional distance of the ultrasound transducer relative to the anode / cathode may be 2x, 3x, or even more than the wavelength.

[0119] The introduction of multiple transducers at the cathode / anode, especially in close proximity to the cathode, causes more agitation and causes numerous cavitation bubbles to collapse along the length of the cathode / anode.

[0120] 3-6, a plurality of ultrasonic transducers 215-220 are disposed at set positions within the aqueous solution 102. In these examples, the ultrasonic transducers 215-220 are attached to the sidewall 103 of the reaction vessel 101. However, in other examples, the ultrasonic transducers 215-220 are spaced apart from the sidewall 103 of the reaction vessel 101.

[0121] In some examples, with all ultrasonic transducers 215-217 aligned in the same direction and facing the cathode 105, collective agitation is increased, resulting in H+ ions interacting with the surface of the cathode 105 and increasing the reaction rate (hydrogen gas production). The arrangement of multiple ultrasonic transducers 218-220 also increases the number of cavitation bubble collapse regions adjacent to the anode 107, further weakening the hydrogen bonds between water molecules and separating them, facilitating individual water molecules' interaction with the anode 107, again increasing the reaction rate.

[0122] Referring now to FIG. 7 of the accompanying drawings, in other examples, the system 1 includes a plurality of ultrasonic transducers 221-223 arranged at least partially around the cathode 105. In these examples, the ultrasonic transducers 221-223 emit ultrasonic waves that impinge on the cathode 105 from a plurality of angles. In the example shown in FIG. 7, three ultrasonic transducers 221-223 are equally spaced around the cathode 105 at angles of 120° or thereabouts. In other examples, there are more or fewer ultrasonic transducers arranged around the cathode 105 at the same or different spacing and angles than shown in FIG. 7. For example, in the case of four ultrasonic transducers, the ultrasonic transducers may be equally spaced around the cathode 105 at angles of 90° or thereabouts.

[0123] 8 of the accompanying drawings, in some examples, the ultrasonic transducers 221-223 are offset relative to one another along the length of the cathode 105 and are positioned at least partially around the cathode 105. In these examples, the ultrasonic transducers 221-223 are positioned on or approximately on a helical path 224 (shown by the dotted line in FIG. 8) that extends along the circumference of a portion of the cathode 105. The purpose of this ultrasonic transducer arrangement is also to impinge ultrasonic waves on the cathode 105 from multiple directions or from all directions to enhance the reduction reaction at the cathode 105.

[0124] In some examples, the ultrasonic transducers are arranged around the anode 107 in the same or similar configuration as the ultrasonic transducers 221-223 arranged around the cathode 105, as described above and shown in Figures 7 and 8. In the case of the anode 107, the purpose of this ultrasonic transducer arrangement is to cause individual water molecules to impinge on the anode 107 from multiple directions or all directions to increase the oxidation reaction at the anode 107. In some examples, the ultrasonic transducers are arranged around the anode 107 but not around the cathode 105, or vice versa.

[0125] Introducing ultrasonic transducers into systems incorporating PEM109 increases the overall yield of hydrogen gas produced. This also increases the reaction rate while reducing the need for expensive precious metal electrode coatings used as catalysts.

[0126] The distance between the anode 107 and the ultrasonic transducers 218-220 is approximately 1 λ (wavelength) of the ultrasonic waves generated by each ultrasonic transducer 218-220. The region of low pressure (rarefaction) causes cavitation bubbles to form in close proximity to the anode 107, which, upon collapse, release high-energy shock waves in the localized area, breaking the hydrogen bonds between water molecules and promoting an increased number of free water molecules that collide with the anode 107 and then decompose into oxygen atoms (which combine together to form oxygen molecules / gas) and hydrogen (H+) ions. The hydrogen ions travel through the PEM 109 and, at the cathode 105, receive electrons that traveled through the power source. This results in hydrogen atoms being collected around the cathode 105 by the hydrogen gas collector 113. The hydrogen atoms covalently bond to form hydrogen gas (H2). The process continues as it would without the ultrasonic transducer, albeit at a higher reaction rate, producing a greater amount of "green hydrogen" in the same duration due to the improved efficiency resulting from the use of ultrasound.

[0127] Multiple ultrasonic transducers are controlled to operate at precise parameters based on their positioning around each other. This ensures that the ultrasonic transmission from each ultrasonic transducer has optimal effect on the cathode / anode and is not reduced by waves from adjacent ultrasonic transducers. In some instances, the transducers are controlled using a single driver IC with multi-channel transducer control outputs to drive single or multiple transducers simultaneously.

[0128] As described below, each transducer driver 202 drives a respective ultrasonic transducer 215 to maximize the delivery of power by the ultrasonic waves emitted from the ultrasonic transducer 215 regardless of the temperature and / or properties of the aqueous solution 102.

[0129] The transducer driver 202 includes an H-bridge circuit connected to the ultrasonic transducer 215. The H-bridge circuit generates an AC drive signal to drive the ultrasonic transducer 215 to generate and transmit ultrasonic waves. A microchip is connected to the H-bridge circuit to control the H-bridge circuit and generate the AC drive signal.

[0130] The microchip is described in detail below. In summary, the microchip comprises an oscillator that generates a main clock signal and a first phase clock signal that goes high a first time during a positive half-period of the main clock signal and goes low during a negative half-period of the main clock signal. The oscillator generates a second phase clock signal that goes high a second time during a negative half-period of the main clock signal and goes low during a positive half-period of the main clock signal. The phases of the first phase clock signal and the second phase clock signal are center-aligned.

[0131] The transducer driver 202 includes a pulse width modulation (PWM) signal generator subsystem, described in detail below, that includes a delay-locked loop that uses the first phase clock signal and the second phase clock signal to generate a double frequency clock signal that is twice the frequency of the main clock signal.

[0132] The delay-locked loop synchronizes the first and second phase clock signals and adjusts the frequency and duty cycle of the first and second phase clock signals in response to the driver control signal to generate first and second phase output signals, which are configured to drive an H-bridge circuit to generate an AC drive signal for driving the ultrasonic transducer 215.

[0133] The first phase output signal terminal outputs a first phase output signal to the H-bridge circuit. The second phase output signal terminal outputs a second phase output signal to the H-bridge circuit. The feedback input terminal receives a feedback signal from the H-bridge circuit, the feedback signal indicating the operation of the H-bridge circuit or a parameter of the AC drive signal when the H-bridge circuit is driving the ultrasonic transducer 215 with the AC drive signal.

[0134] The transducer driver 202 includes an analog-to-digital converter (ADC) subsystem having at least one ADC input terminal for receiving an analog signal. The ADC input terminal is connected to the feedback input terminal such that the ADC subsystem receives a feedback signal from the H-bridge circuit. The ADC subsystem samples the analog signal received at the ADC input terminal at a sampling frequency proportional to the frequency of the main clock signal, and the ADC subsystem generates an ADC digital signal using the sampled analog signal.

[0135] The transducer driver 202 includes a digital processor subsystem that receives the ADC digital signals from the ADC subsystem and processes the ADC digital signals to generate driver control signals. The digital processor subsystem communicates the driver control signals to the PWM signal generator subsystem to control the PWM signal generator subsystem. The transducer driver 202 further includes a digital-to-analog converter (DAC) subsystem that converts the digital control signals generated by the digital processor subsystem into analog voltage control signals to control a voltage regulator circuit that generates a voltage for modulation by the H-bridge circuit.

[0136] The DAC output terminal outputs an analog voltage control signal to control a voltage regulator circuit to generate a predetermined voltage for modulation by an H-bridge circuit to drive the ultrasonic transducer 215 to control cavitation in the aqueous solution in response to a feedback signal indicative of the operation of the ultrasonic transducer. The intensity of the ultrasonic waves emitted by the ultrasonic transducer 215 is controlled by the level of the predetermined voltage.

[0137] The ultrasonic transducer 215 improves the efficiency of the electrolysis process by agitating the aqueous solution 102 with ultrasound waves emitted by the ultrasonic transducer 215 and by using energy generated from cavitation in the aqueous solution 102, which weakens or breaks hydrogen bonds in water molecules. In some examples, the ultrasonic transducer 215 generates ultrasound waves at a frequency of 20 kHz to 40 kHz, preferably 26 kHz, which agitates the aqueous solution 102 by causing numerous localized cavitation implosions (the formation and collapse of small gas bubbles in the solution). This cavitation creates localized regions of high pressure and temperature within the aqueous solution 102, thus increasing the rate of the electrolysis reaction.

[0138] In other examples, the transducer driver 202 drives the ultrasonic transducer 215 at a higher frequency of 2 MHz to 5 MHz or 3 MHz ±200 kHz.

[0139] In another example of the present disclosure, the transducer driver 202 drives the ultrasonic transducer 215 at a frequency ranging from 20 kHz to 5 MHz.

[0140] The intensity of ultrasound required for ultrasonic electrolysis of water depends on various factors, such as the size and shape of the reaction vessel, the properties of the aqueous solution, and the desired effect of ultrasound on the electrolysis process. In some examples, the system 100 uses high-intensity ultrasound for water electrolysis where cavitation is desired.

[0141] In some examples of the present disclosure, the driver device 202 may be configured to provide a power rating of 0.05 Wcm -2 ~0.5Wcm -2 , or preferably 0.1 Wcm -2 However, other intensity values ​​and ranges are contemplated, and one skilled in the art will understand that an intensity value or range will be selected in other examples based on the use and application of the system. For example, a higher ultrasound intensity, e.g., 0.5 Wcm -2 ~5Wcm -2 It will be appreciated that may be required to generate hydrogen gas in industrial applications.

[0142] The intensity of the ultrasound emitted by the ultrasonic transducer 215 is controlled by an algorithm implemented in the transducer driver 202. The algorithm works in harmony with an integrated circuit within the transducer driver 202 and uses a feedback loop to continuously adjust the intensity and frequency of the ultrasound generated by the ultrasonic transducer 215 to ensure optimal hydrogen gas production.

[0143] The transducer driver 202 uses the continuous monitoring of the volume of hydrogen gas produced to adjust the frequency and / or intensity of the ultrasound waves emitted by the ultrasonic transducer 215. A gas pressure sensor 117 in the hydrogen gas collector 112 records the increase in gas pressure over time to determine the gas production rate. This information is relayed to the transducer driver 202 in the form of a gas pressure signal. The transducer driver 202 then adjusts the frequency and / or intensity of the ultrasound waves emitted by the ultrasonic transducer 215 to increase and maintain the rate of hydrogen gas production. This forms a feedback loop between the initial parameters (frequency and intensity) and the adjusted parameters (frequency and intensity).

[0144] In examples of the present disclosure using high-frequency ultrasound (approximately 3 MHz±200 kHz), high-frequency ultrasound can result in more efficient cavitation (the formation and collapse of small bubbles in an aqueous solution). As the bubbles collapse, they create localized regions of high temperature and pressure at the cavitation bubbles for a very short period of time, which enhances the reaction rate and facilitates the extraction of hydrogen gas. High-frequency ultrasound results in small, stable cavitation bubbles, which result in more efficient energy transfer and more effective mixing of the aqueous solution.

[0145] Direct Ultrasonic Electrolysis Seawater can be used as an electrolyte in electrolysis applications. Seawater is a naturally occurring electrolyte solution containing a variety of dissolved salts and ions, such as sodium, chloride, magnesium, and calcium ions.

[0146] Conventional systems for producing hydrogen from seawater first desalinate the seawater to remove dissolved salts, and then electrolyze the resulting purified water to produce hydrogen gas. However, by using ultrasound and incorporating frequency and / or intensity adjustments made by transducer driver 202, system 100 can directly electrolyze seawater to produce hydrogen gas. The expensive and time-consuming process of desalination is eliminated by some example systems of the present disclosure.

[0147] When the system 100 is operating, ultrasonic waves emitted by the ultrasonic transducer 215 are applied to the seawater, thereby inducing cavitation (the formation and collapse of gas bubbles). This phenomenon creates localized regions of high pressure and temperature at the cavitation bubbles in the seawater for a very short period of time, resulting in increased mass and heat transfer rates. The energy from the cavitation weakens or breaks the hydrogen bonds between water molecules.

[0148] The ultrasonic waves emitted by the ultrasonic transducer 215 displace solutes present in the seawater, promoting electrolysis adjacent the surface of the cathode 105 .

[0149] The improved mass transfer enhances the mixing and movement of reactants near the electrodes 105, 106 and improves the distribution of ions in the aqueous solution 102 (seawater), where ions are free to move within the aqueous solution 102 (seawater), just as they are in seawater desalinated in a conventional electrolysis process.

[0150] The example systems of the present disclosure allow for precise control of the frequency and intensity of the ultrasound emitted from the ultrasonic transducer to precisely control the system and respond to changes in reaction conditions within the reaction vessel. The ultrasound reduces the formation of fouling on the electrodes and promotes the formation of a more uniform and well-defined electrode surface, which improves the efficiency and durability of the electrodes over time.

[0151] In some examples, the ultrasonic transducers are positioned to emit ultrasonic waves upward in a direction generally aligned with the longitudinal length of the hydrogen gas collector 113 or the oxygen gas collector 114. The ultrasonic waves emitted by the ultrasonic transducers control the distribution of hydrogen gas bubbles in the aqueous solution 102. Having at least one ultrasonic transducer as an ultrasonic source at the base of each anode / cathode ensures efficient stirring of the aqueous solution 102. The stirring effect exposes more ions to the surface of the anode / cathode, increasing gas production.

[0152] Each of the ultrasonic transducers described above is electrically coupled to one or more transducer drivers, such as transducer driver 202.

[0153] The placement of each ultrasonic transducer relative to its respective anode 107 or cathode 105 depends on the particular application and properties of the aqueous solution 102. Ideally, the transducers are placed in close proximity to the outer surfaces 106, 18 of the anode / cathode (either below or to the side of the anode / cathode) to promote the formation of cavitation bubbles and improve the efficiency of the electrolysis process.

[0154] The placement of the ultrasonic transducers within the reaction vessel 101 depends on the size and geometry of the reaction vessel 101 as well as the properties of the aqueous solution 102 .

[0155] The size of the reaction vessel 101 affects the rate of electrolysis due to the following considerations.

[0156] Mass transport: The speed at which ions reach the cathode 105 and anode 107 is affected by the distance the ions must travel to contact the cathode 105 and anode 107. In smaller reaction vessels, this distance is shorter, shortening the path for ions to reach the electrodes and resulting in faster gas generation.

[0157] Electrode surface area: A larger reaction vessel allows for larger or multiple electrodes, increasing the total surface area available for ions to contact, which increases the volume of gas produced (increased production rate). In some examples of the present disclosure, the system 100 includes more electrodes than the cathode 105 and anode 107 of the example above.

[0158] The geometry of the reaction vessel affects the rate of the electrolysis process for the following reasons:

[0159] Electrode Position: The positions of the cathode / anode are selected based on the geometry of the reaction vessel. The spacing between the cathode 105 and the anode 107 is also selected based on the geometry of the reaction vessel 101. The distance between the cathode 105 and the anode 107 and their relative positioning affect the amount of ions that contact them, which affects the reaction rate.

[0160] Ion density around the electrode: The shape of the reaction vessel affects the distribution of electrolyte (ion density) around the cathode 105 and anode 107. Uniform electrolyte distribution around the cathode 105 and anode 107 promotes efficient ion transport and increases the reaction rate.

[0161] Optimization of reactor size requires consideration of a balance between the ion transport distance to the electrode and the available surface area of ​​the electrode for ion contact.

[0162] Scalability: In some instances, the reactor shape is selected for industrial scale use, meaning that the reactor shape is adapted to the desired hydrogen gas production capacity and is easy to maintain and operate.

[0163] The size and geometry of the reaction vessel are parameters that affect the performance, efficiency, and speed of the electrolysis process. The introduction and placement of at least one ultrasonic transducer in the reaction vessel are determined by the size and geometry of the reaction vessel, which also determines the type of ultrasonic transducer to be placed in the electrolyte.

[0164] 9 of the accompanying drawings, some example ultrasonic transducer arrays 122 include three ultrasonic transducers 215-217 held by a transducer holder 123. Each of the ultrasonic transducers 215-217 has a diameter D T The center of each of the ultrasonic transducers 215 to 217 is spaced a distance S from the center of an adjacent one of the ultrasonic transducers 215 to 217.T The distances are spaced apart by 1 / 2.

[0165] Figure 10 of the accompanying drawings shows an example system with several relevant dimensions labeled. The relationships between these dimensions for this example system are summarized in the table shown in Figure 11. The relationships between component dimensions and parameters are specific to this illustrated example. The present disclosure is not limited to the specific dimensions and relationships disclosed herein, and other dimensions and relationships are contemplated. For example, one skilled in the art will understand that the dimensions and relationships can be modified to scale up the system, for example, for industrial production of hydrogen gas.

[0166] In the example shown in FIG. 10, the reaction vessel 101 has a 1:1 diameter (D v ) versus height (h v ) ratio. Other examples of the present disclosure contemplate reaction vessels of different shapes. In some examples, the reaction vessel is rectangular (cuboid) shaped. In some examples, the reaction vessel is a variable depth vessel with a non-planar base for controlling mass flow rate within the reaction vessel.

[0167] In this example, the anode and cathode are each 110% * h v ≦l e ≦120% * h v The length of the range (l e ) and has a length (l e ) is immersed in the aqueous solution.

[0168] The immersion length of the anode / cathode is l i In this example, the diameter of each electrode (D e ) is 7%≦D v ≦20%.

[0169] In this example, each transducer has a diameter D TThe transducer diameter may be 2 cm to 5 cm. However, other transducer diameters are contemplated, and the transducer diameter selected will depend on the intended use and functionality of the system for generating hydrogen gas. The relative dimensions described herein may be scaled up for larger systems for producing hydrogen gas.

[0170] In some examples, the ultrasonic transducer functions to generate ultrasonic waves using thickness mode vibrations, with the thickness of the ultrasonic transducer being a determining factor in its resonant frequency, although other types of ultrasonic transducers are also contemplated.

[0171] In this example, the spacing between the ultrasonic transducers is S T and 1 / 2 * D T is set as

[0172] In this example, the volume of the aqueous solution is set to a maximum filling height (h e However, other aqueous solution volumes are contemplated, and one of ordinary skill in the art will understand how to calculate the aqueous solution fill volume based on the parameters of the reaction vessel configured for the intended purpose.

[0173] In this example, the anode or cathode E s The arrangement of the distance from the center of the anode / cathode to the center of the cylindrical reactor vessel (D v +1 / 2 * D e 25% to 30% of the total.

[0174] In some examples, different shapes of disk-shaped transducers and ultrasonic horns (sonotrodes) are selected to transmit ultrasonic waves throughout the electrolyte 102 in the reaction vessel 101 .

[0175] 12 of the accompanying drawings, some example systems 124 include a membrane electrode assembly (MEA) 125 for the electrolysis of water. The MEA 125 includes a polymer electrolyte membrane (PEM) 126 disposed or sandwiched between an anode 127 and a cathode 128.

[0176] The PEM 126 is a proton exchange membrane, preferably made of a perfluorosulfonic acid-based material or similar proton-conducting polymer. An example of a PEM is commercially available from The Chemours Company FC, LLC. (Wilmington, Delaware, USA) under the trademark Nafion™. The PEM 126 conducts protons (H+ ions) and blocks the passage of electrons. To take advantage of this property of the polymer, the PEM 126 separates the cathode 128 and anode 127 and is positioned to facilitate the splitting of water into hydrogen and oxygen.

[0177] PEM electrolysis does not require caustic electrolyte, occupies minimal space, and is safer than traditional alkaline electrolysis.

[0178] In a PEMWE, the oxygen produced is removed from the surface of the anode 127, while the remaining protons (H+) cross the proton-conducting membrane toward the cathode 128. Simultaneously, electrons travel through an external circuit to reach the cathode 128. At the cathode 128, the protons and electrons recombine to generate hydrogen gas.

[0179] In these examples, the anode 127 and the cathode 128 are each planar or substantially planar electrodes. In these examples, the anode 127 and the cathode 128 are each provided with a respective gas diffusion layer (GDL). In these examples, the anode 127 and the cathode 128 are each gas diffusion electrodes (GDEs) preferably made of a porous, electrically conductive material. The anode 127 and the cathode 128 are each preferably coated with at least one catalyst to facilitate the electrochemical reaction.

[0180] In the MEA 125, the anode 127 and the cathode 128 are preferably noble metal electrodes, and the oxide of the noble metal is the electrocatalyst (e.g., but not limited to, platinum, iridium, iridium dioxide (IrO2), rhodium, rhodium oxide (RhO2)).

[0181] In some examples, the anode 127 and cathode 128 are each porous, containing interconnected pores or channels throughout their structure. This porosity serves as an increased surface area for the catalyst to interact with water molecules, increasing the efficiency of the electrochemical reaction and proton (H+) diffusion to the cathode side.

[0182] 13-16 of the accompanying drawings, in some examples, MEA 125 is disposed within housing 129, which is preferably a sealed container configured to allow reactants and products to flow. Seals and gaskets resist gas and / or liquid pressure within housing 129, ensuring a tight and secure enclosure that prevents leaks.

[0183] In some examples, the housing 129 comprises a first housing portion 130 and a second housing portion 131 coupled together along a sealing interface 132 .

[0184] In some examples, first housing portion 130 includes a sidewall 133 coupled to an end wall 134. A first interior chamber 135 is formed between at least a portion of sidewall 133 and end wall 134. An anode 127 of MEA 125 is disposed on an opposite side of first housing portion 130 from end wall 134. Preferably, an airtight or substantially airtight seal is provided between anode 127 and sidewall 133.

[0185] An inlet port 136 is provided in the first housing portion 130. In this example, the inlet port 136 is located on the end wall 134. The inlet port 136 provides a water flow path that allows water to flow from a water source into the first interior chamber 135.

[0186] An outlet port 137 is provided in first housing portion 130. In this example, outlet port 137 is located on end wall 134 and is spaced apart from inlet port 136 on an opposite corner of end wall 134 relative to inlet port 136. Outlet port 137 provides an oxygen gas and water flow path to allow oxygen gas and water to exit first interior chamber 135 for storage or use.

[0187] In some examples, the first housing portion 130 includes an anode connector 138 that allows the anode 127 to be connected to a power source, such as a DC power source 139 as shown in FIG.

[0188] 15 and 16 of the accompanying drawings, in some examples, the system 124 includes at least one ultrasonic transducer 140-146 disposed within the first internal chamber 135. In this example, the system 124 includes nine ultrasonic transducers 140-146 held in three separate transducer holders 147-149, respectively, coupled to the first housing portion 130.

[0189] Each ultrasonic transducer 140 - 146 is driven by a respective transducer driver 202 as described herein with respect to ultrasonic transducer 215 .

[0190] In this example, ultrasonic transducers 140-146 emit ultrasonic waves at least partially toward anode 127 to induce cavitation in water 150 in first internal chamber 135 proximate the surface of anode 127. Cavitation weakens hydrogen bonds between water molecules, separating individual water molecules available for interaction with anode 127, where they undergo an oxidation reaction, oxidizing OH ions to form oxygen gas and H ions at anode 127. The H ions pass through PEM 126 to reach cathode 128.

[0191] 13-15 of the accompanying drawings, in some examples, second housing portion 131 includes a sidewall 151 coupled to an end wall 152. A second interior chamber 153 is formed between at least a portion of sidewall 151 and end wall 152. Cathode 128 of MEA 125 is positioned on the opposite side of second housing portion 131 from end wall 152. Preferably, an airtight or substantially airtight seal is provided between cathode 128 and sidewall 151.

[0192] At least one hydrogen outlet port 154, 155 is provided in the second housing portion 131. In this example, two hydrogen outlet ports 154, 155 are provided in the second housing portion 131. In this example, the hydrogen outlet ports 154, 155 are located on the end wall 152. Each hydrogen outlet port 154, 155 provides a flow path that allows hydrogen gas to flow from the second internal chamber 153 for storage or use.

[0193] In some examples, the second housing portion 131 includes a cathode connector 156 to allow the cathode 128 to be connected to a power source, such as the DC power source 139 shown in FIG.

[0194] In some examples, the cathode 128 is a cathode ultrasonic transducer that is driven to vibrate by a transducer driver 202 or oscillator. In these examples, the vibrations in the cathode 128 help remove any hydrogen gas that has formed on the surface of the cathode 128 and expose the surface of the cathode 128 to additional H+ ions for the generation of hydrogen gas.

[0195] Referring now to FIG. 17 of the accompanying drawings, a system 157 in some examples of the present disclosure includes a plurality of hydrogen generation cells 158 .

[0196] Each hydrogen production cell 158 is a PEM system the same as or similar to the above-described system 128. The hydrogen production cells 158 are preferably coupled together in an array to produce hydrogen gas from water pumped through the hydrogen production cells 158.

[0197] The operation of the hydrogen generation cells 158 is controlled by the main controller 2, which coordinates the operation of each hydrogen generation cell 158 so that the array produces hydrogen gas at a desired rate. In some examples, the main controller 2 activates all or a subset of the hydrogen generation cells 158 to produce hydrogen gas based on the desired hydrogen gas production rate. If the main controller 2 detects that the hydrogen gas production rate of the array is higher than a threshold, the main controller 2 shuts down one or more of the hydrogen generation cells 158. Conversely, if the main controller 2 detects that the hydrogen gas production rate of the array is lower than a threshold, the main controller 2 activates one or more of the hydrogen generation cells 158. In this way, the main controller 2 can control the hydrogen gas production rate to a safe level for the intended storage volume or application.

[0198] The main controller 2 coordinates the activation and deactivation of each hydrogen generation cell 158, while simultaneously optimizing the operation of each activated hydrogen generation cell 158. Thus, the main controller 2 maximizes the flexibility and efficiency of the system 157 to efficiently produce hydrogen gas at a desired rate.

[0199] 18 of the accompanying drawings, the transducer driver 202 comprises a microchip referred to herein as a power management integrated circuit or PMIC 300. The PMIC 300 is a microchip for driving the ultrasonic transducer 215.

[0200] The transducer driver 202 provides precise control to ensure that each ultrasonic transducer is operating at its optimum frequency (resonance) to maximize ultrasonic displacement (amplitude / intensity) with the lowest possible power input. This is achieved by using a feedback loop function in the transducer driver 202, whereby the transducer driver 202 senses the current flowing through the ultrasonic transducer 215 and adjusts the drive frequency of the ultrasonic transducer 215 to maximize the effective power consumed by the ultrasonic transducer 215. The feedback loop therefore ensures that the transducer driver 202 drives the ultrasonic transducer 215 at or near its resonant (optimal) frequency. The feedback loop in the transducer driver 202 is described in more detail below.

[0201] In some examples, multiple ultrasound transducers are controlled to operate at precise parameters based on their positioning around one another, ensuring that the ultrasound transmission effect of each transducer on the electrode is maximized and not diminished by waves from adjacent transducers.

[0202] In some examples, the transducers are controlled using a single transducer driver 202 with multi-channel transducer control outputs to drive single or multiple transducers simultaneously.

[0203] In this disclosure, the terms chip, microchip, and integrated circuit are interchangeable. A microchip or integrated circuit is a single unit that comprises multiple interconnected embedded components and subsystems. A microchip is, for example, at least partially a semiconductor, such as silicon, and is fabricated using semiconductor fabrication techniques.

[0204] The transducer driver 202 comprises a second microchip, referred to herein as a bridge integrated circuit or bridge IC 301, electrically connected to the PMIC 300. The bridge IC 301 is a microchip for driving a piezoelectric transducer, such as the ultrasound transducer 215. The bridge IC 301 is a single unit comprising multiple interconnected embedded components and subsystems.

[0205] In this example, the PMIC 300 and the bridge IC 301 are mounted on the same PCB of the transducer driver 202 .

[0206] The ultrasonic transducer 215 is electrically connected to the bridge IC 301 so that the ultrasonic transducer 215 can be driven by an AC drive signal generated by the bridge IC 301 during operation of the system 100 .

[0207] The transducer driver 202 comprises a processor in the form of a microcontroller 303 electrically coupled for communication with a communication bus 302. The microcontroller 303 receives power from a low dropout regulator (LDO) 304 that is driven by a power supply (not shown). The LDO 304 provides a stable regulated voltage to the microcontroller 303, allowing the microcontroller 303 to operate reliably even when the voltage of the power supply fluctuates.

[0208] The transducer driver 202 includes a voltage regulator in the form of a DC-DC boost converter 305 that is powered by a power supply. The boost converter 305 increases the voltage of the power supply to a programmable voltage VBOOST. The programmable voltage VBOOST is set by the boost converter 305 in response to a voltage control signal VCTL from the PMIC 300. As will be explained in more detail below, the boost converter 305 outputs the voltage VBOOST to the bridge IC 301. In another example, the voltage regulator is a buck converter or another type of voltage regulator that outputs a selectable voltage.

[0209] The voltage control signal VCTL is generated by a digital-to-analog converter (DAC) that is implemented in this example within the PMIC 300. Because the DAC is integrated within the PMIC 300, the DAC is not visible in FIG. 18. The DAC and the technical benefits of integrating the DAC within the PMIC 300 are described in detail below.

[0210] In this example, the PMIC 300 is connected to a power connector 306 so that the PMIC 300 can receive power from a power source.

[0211] The microcontroller 303 acts as the master device on the communication bus 302, and the PMIC 300 is the first slave device. The communication bus 302 allows the microcontroller 303 to control the following functions within the transducer driver 202: 1. All functions of the PMIC are highly configurable by the microcontroller 303. 2. The current flowing through the ultrasonic transducer 215 is sensed at a high common-mode voltage (the high side of the bridge) by a high-bandwidth sensing and rectifying circuit. The sensed current is converted to a voltage proportional to the rms current and provided as a buffered voltage at the current sense output pin 309 of the bridge IC 301. This voltage is provided to the PMIC 300 where it is sampled and made available as a digital representation via an I2C request. Sensing the current flowing through the ultrasonic transducer 215 forms part of the resonant frequency tracking function. As described herein, the device's ability to enable this function within the bridge IC 301 provides a significant technical advantage. 3. A DAC (not shown in FIG. 18) integrated within the PMIC 300 allows the DC-DC boost converter voltage VBOOST to be programmed to be between 10V and 20V.

[0212] 19 of the accompanying drawings, PMIC 300, in this example, is a self-contained chip or integrated circuit that includes an integrated subsystem and a number of pins that provide electrical inputs and outputs to PMIC 300. References to integrated circuits or chips in this disclosure are interchangeable, and either term encompasses semiconductor devices that may be made of, for example, silicon.

[0213] The PMIC 300 comprises an analog core 310 that comprises analog components including a reference block (BG) 311 , an LDO 312 , a current sensor 313 , a temperature sensor 314 , and an oscillator 315 .

[0214] As described in more detail below, oscillator 315 is coupled to a delay-locked loop (DLL) that outputs pulse-width modulation (PWM) phases A and B. Oscillator 315 and the DLL generate a two-phase center-aligned PWM output that drives an H-bridge within bridge IC 301.

[0215] The DLL comprises multiple delay lines connected end-to-end, with the total delay of the delay lines equal to the period of the main clock signal clk_m. In this example, the DLL is implemented in a digital processor subsystem, referred to herein as digital core 316, of PMIC 300, which receives a clock signal from oscillator 315 and a regulated power supply voltage from LDO 312. The DLL is implemented in a large number (e.g., on the order of millions) of delay gates connected end-to-end in digital core 316.

[0216] The implementation of the oscillator 315 and DLL within the same integrated circuit of the PMIC 300 to generate a two-phase center-aligned PWM signal is unique as there are currently no signal generator components on the integrated circuit market that include this implementation.

[0217] As described herein, PWM is part of the functionality that allows the transducer driver 202 to accurately track the resonant frequency of the ultrasonic transducer 215 to maintain efficient transfer of electrical energy to kinetic energy to optimize the production of hydrogen gas generation.

[0218] The PMIC 300 includes an integrated power switch VSYS that configures the PMIC 300 to power the analog core 310 with power from a power supply.

[0219] The PMIC 300 includes an embedded analog-to-digital converter (ADC) subsystem 318. Implementing the ADC 318 along with the oscillator 315 within the same integrated circuit is unique in itself, as there are no other integrated circuits on the integrated circuit market that include an oscillator and an ADC implemented as sub-blocks within the integrated circuit. In conventional devices, the ADC is typically provided as a separate component from the oscillator, and the separate ADC and oscillator are mounted on the same PCB. A problem with this conventional configuration is that the two separate components, the ADC and the oscillator, unnecessarily occupy space on the PCB. A further problem is that conventional ADCs and oscillators are typically connected to each other by a serial data communication bus, such as an I2C bus, which has a limited communication speed of only up to 400 kHz. In contrast to conventional devices, the PMIC 300 has the ADC 318 and oscillator 315 integrated within the same integrated circuit, which eliminates any delay in communication between the ADC 318 and oscillator 315, meaning that the ADC 318 and oscillator 315 can communicate with each other at high speeds, such as the speed of the oscillator 315 (e.g., 20 MHz to 40 kHz).

[0220] In this example PMIC 300, oscillator 315 operates at 26 kHz and generates a 26 kHz clock signal SYS CLOCK. However, in other examples, oscillator 315 generates a clock signal at a frequency between 20 kHz and 40 kHz, preferably 26 kHz. All integrated circuits described herein are configured to operate at the high frequency of oscillator 315.

[0221] The ADC 318 has a plurality of feedback input terminals or analog inputs 319 with a plurality of GPIO inputs (IF_GPIO1-3).

[0222] At least one of the feedback input terminals or analog inputs 319 receives the gas pressure signal from the pressure sensor 117 .

[0223] At least one of the feedback input terminals or analog inputs 319 receives a feedback signal from the H-bridge circuit within bridge IC 301, the feedback signal indicative of a parameter of the operation of the H-bridge circuit or AC drive signal as it drives the ultrasonic transducer 215 with the AC drive signal. As described below, the GPIO input is used to receive a current sense signal from bridge IC 301 indicative of the root-mean-square (rms) current reported by bridge IC 301. In this example, one of the GPIO inputs is a feedback input terminal that receives a feedback signal from the H-bridge within bridge IC 301.

[0224] The ADC subsystem 318 samples the analog signals received at a plurality of ADC input terminals 319 at a sampling frequency proportional to the frequency of the main clock signal. The ADC subsystem 318 then generates ADC digital signals using the sampled analog signals.

[0225] In this example, the ADC 318 built into the PMIC 300 samples not only the RMS current through the H-bridge 334 and the ultrasonic transducer 215, but also voltages available in the system (such as VBOOST), the temperature of the PMIC 300, and the GPIO inputs (IF_GPIO1-3).

[0226] The digital core 316 receives the ADC-generated digital signal from the ADC subsystem and processes the ADC digital signal to generate the driver control signal, which the digital core 316 communicates to the PWM signal generator subsystem (DLL 332) to control the PWM signal generator subsystem.

[0227] Rectifier circuits on the market today have very limited bandwidth. The PMIC 300's oscillator 315 can operate over a wide range, from 20 kHz to 5 MHz, allowing the PMIC 300 to implement a high-bandwidth rectifier circuit. As described below, sensing the RMS current in the H-bridge of the bridge IC 301 forms part of a feedback loop that enables the transducer driver 202 to drive the ultrasonic transducer 215 with high precision. The feedback loop is a game-changer in the ultrasonic transducer driving industry because it accounts for any process variations in piezoelectric transducer manufacturing (variations in resonant frequency) and compensates for temperature effects on the resonant frequency. This is achieved, in part, by implementing the present invention, which integrates the ADC 318, oscillator 315, and DLL within the same integrated circuit of the PMIC 300. The integration allows these subsystems to communicate with each other at high speeds (e.g., clock frequencies up to 20 kHz or 5 MHz).

[0228] The ADC 318 includes voltage monitoring inputs VMON and VRTH, as well as a temperature monitoring input TEMP, which receives a temperature signal from a temperature sensor 314 embedded within the PMIC 300. This allows the PMIC 300 to accurately sense the actual temperature within the PMIC 300, allowing the PMIC 300 to detect any faults within the PMIC 300, as well as faults to other components on the printed circuit board that affect the temperature of the PMIC 300. In order to maintain system safety, the PMIC 300 can control the bridge IC 301 to prevent excitation of the ultrasonic transducer 215 in the event of a fault.

[0229] The PMIC 300, in this example, includes an LED driver 320 that receives digital drive signals from the digital core 316 and provides LED drive output signals to six LEDs 321-326 that are configured to be coupled to output pins of the PMIC 300. Thus, the LED driver 320 can drive and dim the LEDs 321-326 on up to six independent channels.

[0230] The PMIC 300 includes a first digital-to-analog converter (DAC) 327 that converts digital signals within the PMIC 300 into an analog voltage control signal that is output from the PMIC 300 via output pin VDAC0. The first DAC 327 converts the digital control signal generated by the digital core 316 into an analog voltage control signal that is output via output pin VDAC0 to control a voltage regulator circuit, such as boost converter 305. Thus, the voltage control signal, in response to a feedback signal indicative of operation of the ultrasonic transducer 215, controls the voltage regulator circuit to generate a predetermined voltage for modulation by the H-bridge circuit to drive the ultrasonic transducer 215.

[0231] In this example, the PMIC 300 includes a second DAC 328 that converts the digital signal within the PMIC 300 to an analog signal that is output from the PMIC 300 via a second analog output pin VDAC1.

[0232] Embedding the DAC 327 or DACs 327, 328 on the same microchip as other subsystems of the PMIC 300 allows the DACs 327, 328 to communicate with the digital core 316 and other components within the PMIC 300 at high speeds with minimal or no communication delays. The DACs 327, 328 provide analog outputs that control external feedback loops. For example, the first DAC 327 provides a control signal VCTL to the boost converter 305 to control the operation of the boost converter 305. In another example, the DACs 327, 328 are configured to provide drive signals to a DC-DC buck converter instead of or in addition to the boost converter 305. Integrating two independent DAC channels into the PMIC 300 allows the PMIC 300 to operate the feedback loop of any regulator used in the transducer driver 202, allowing the transducer driver 202 to adjust the ultrasonic processing power of the ultrasonic transducer 215 or set analog thresholds for the absolute maximum current and temperature settings of the ultrasonic transducer 215.

[0233] The PMIC 300 includes a serial communication interface, which in this example is an I2C interface incorporating an external I2C address that is set via pins.

[0234] The PMIC 300 also includes various functional blocks, including a functionally similar to a digital machine (FSM), for implementing the functionality of the microchip, which are described in more detail below.

[0235] 20 of the accompanying drawings, a pulse width modulation (PWM) signal generator subsystem 329 is embedded within the PMIC 300. The PWM generator system 329 comprises an oscillator 315, a frequency divider 330, a multiplexer 331, and a delay locked loop (DLL) 332. As described below, the PWM generator system 329 is a two-phase center-matched PWM generator.

[0236] Frequency divider 330 , multiplexer 331 , and DLL 332 are implemented in digital logic components (eg, transistors, logic gates, etc.) within digital core 316 .

[0237] In the examples of the present disclosure, the frequency ranges covered by the oscillator 315 and the PWM generator system 329 are 20 kHz to 5 MHz or 20 kHz to 40 kHz, respectively, and preferably 26 kHz. The frequency accuracy of the PWM generator system 329 is ±1% and the temperature spread is ±1%. There are no ICs on the IC market today with built-in oscillators and two-phase center-matched PWM generators that can provide a frequency range of 20 kHz to 5 MHz. In fact, some example ICs of the present disclosure can provide a frequency range of 20 kHz to 105 MHz.

[0238] Oscillator 315 generates a main clock signal (clk_m) having a frequency between 20 kHz and 5 MHz or between 20 kHz and 40 kHz, preferably 26 kHz. Main clock clk_m is input to frequency divider 330, which divides the frequency of main clock clk_m by one or more predetermined divisor amounts. In this example, frequency divider 330 divides the frequency of main clock clk_m by 2, 4, 8, and 16 and provides the divided frequency clocks as outputs to multiplexer 331. Multiplexer 331 multiplexes the divided frequency clocks and provides the divided frequency output to DLL 332. This signal passed to DLL 332 is a frequency reference signal that controls DLL 332 to output a signal at the desired frequency. In other examples, frequency divider 330 and multiplexer 331 are omitted.

[0239] The oscillator 315 also generates two phases, a first phase clock signal Phase 1 and a second phase clock signal Phase 2. The phases of the first phase clock signal and the second phase clock signal are center aligned. As shown in FIG. The first phase clock signal, phase 1, is high for a variable amount of time during the positive half-period of clk_m and low during the negative half-period of clk_m. The second phase clock signal, phase 2, is high for a variable amount of time during the negative half-period of clk_m and low during the positive half-period of clk_m.

[0240] Phase 1 and Phase 2 are then sent to DLL 332, which uses first phase clock signal Phase 1 and second phase clock signal Phase 2 to generate a double frequency clock signal. The double frequency clock signal is twice the frequency of the main clock signal clk_m. In this example, an "OR" gate within DLL 332 uses first phase clock signal Phase 1 and second phase clock signal Phase 2 to generate the double frequency clock signal. This double frequency clock, or divided frequency coming from frequency divider 330, is selected based on the selected target frequency and is then used as a reference for DLL 332.

[0241] In DLL 332, the signal hereafter referred to as "clock" represents the doubled main clock clk_m, and the signal hereafter referred to as "clock_del" is a replica of clock delayed by one period of frequency. Clock and clock_del pass through a phase frequency detector. Node Vc is then charged or discharged by a charge pump based on the phase error polarity. A control voltage is directly supplied to control the delay of every single delay unit in DLL 332 until the total delay of DLL 332 is exactly one period.

[0242] The DLL 332 controls the first phase clock signal, Phase 1, and the second phase clock signal, Phase 2, so that the rising edges of these signals are synchronized with the rising edges of the double frequency clock signal. The DLL 332 adjusts the frequency and duty cycle of the first phase clock signal, Phase 1, and the second phase clock signal, Phase 2, in response to the respective frequency reference signal and duty cycle control signal to generate the first phase output signal, Phase A, and the second phase output signal, Phase B, which drive an H-bridge or inverter to generate an AC drive signal for driving the ultrasonic transducer.

[0243] The PMIC 300 includes a first phase output signal terminal Phase_A that outputs a first phase output signal Phase A to the H-bridge circuit, and a second phase output signal terminal Phase_B that outputs a second phase output signal Phase B to the H-bridge circuit.

[0244] In this example, DLL 332 adjusts the duty cycle of first phase clock signal Phase 1 and second phase clock signal Phase 2 in response to the duty cycle control signal by varying the delay of each delay line within DLL 332 in response to the duty cycle control signal.

[0245] The clock is used at twice its frequency to ensure better accuracy. As shown in FIG. 22, for illustration purposes, if the frequency of the main clock clk_m is used (not used in the examples of this disclosure), phase A is synchronized with the rising edge R of the clock, and phase B is synchronized with the falling edge F of the clock. Because the delay line of DLL 332 controls the rising edge R, for the falling edge F, PWM generator system 329 must rely on perfect matching of the delay units of DLL 332, which may be imperfect. However, to eliminate this error, PWM generator system 329 uses a double-frequency clock such that both phase A and phase B are synchronized with the rising edge R of the double-frequency clock.

[0246] To implement a duty cycle from 20% to 50% with a 2% step size, the delay line of DLL 332 includes 25 delay units, with the output of each respective delay unit representing a phase n. Ultimately, the phase of the output of the last delay unit corresponds to the input clock. Considering that all delays are approximately the same, a particular duty cycle can be obtained using the output of a particular delay unit with simple logic in digital core 316.

[0247] It is important to handle the start-up of DLL 332 because DLL 332 can lock onto two or more periods rather than one delay period, potentially putting DLL 332 in a non-convergence zone. To avoid this problem, a start-up circuit is implemented in PWM generator system 329 that allows DLL 332 to start from a known deterministic condition. The start-up circuit also allows DLL 332 to start with a minimum delay.

[0248] In the example of the present disclosure, the frequency range covered by PWM generator system 329 is extended, and therefore the delay unit in DLL 332 can provide delays from 4 ns (for a 5 MHz oscillator frequency) to 400 ns (for a 50 kHz oscillator frequency). To accommodate these different delays, capacitors Cb are included in PWM generator system 329, with the capacitor values ​​selected to provide the required delays.

[0249] Phase A and Phase B are output from DLL 332 and passed to bridge IC 301 via digital IO so that Phase A and Phase B can be used to control the operation of bridge IC 301.

[0250] We now describe in more detail the analog-to-digital converter (ADC) 318. The inventors had to overcome significant technical challenges to integrate the ADC 318 with the high-speed oscillator 315 within the PMIC 300. Furthermore, integrating the ADC 318 within the PMIC 300 runs counter to conventional approaches in the art, which rely on using one of the many separate ADC devices available on the IC market.

[0251] In this example, ADC 318 samples at least one parameter within the ultrasound transducer driver chip (PMIC 300) at a sampling rate equal to the frequency of the main clock signal clk_m. In this example, ADC 318 is a 10-bit analog-to-digital converter that can offload digital sampling from microprocessor 303 to conserve microprocessor 303 resources. Integrating ADC 318 within PMIC 300 also avoids the need to use an I2C bus, which would otherwise slow down the ADC's sampling capability (traditional devices rely on an I2C bus to communicate data between a dedicated, separate ADC and a microcontroller, typically at a limited clock speed of up to 400 kHz).

[0252] In the example of the present disclosure, one or more of the following parameters may be sampled sequentially by the ADC 318: i. The rms current signal received at the ultrasonic transducer driver chip (PMIC 300) from the external inverter circuit driving the ultrasonic transducer. In this example, this parameter is the root-mean-square (rms) current reported by the bridge IC 301. Sensing the rms current is important for implementing the feedback loop used to drive the ultrasonic transducer 215. Because the ADC 318 does not rely on this information being transmitted over the I2C bus, the ADC 318 can sense the rms current directly from the bridge IC 301 via a signal with minimal or no delay. This provides significant speed and accuracy benefits over conventional devices that are constrained by the relatively slow speed of the I2C bus. ii. The voltage of the power supply connected to the PMIC300. iii. A temperature signal, such as a temperature signal indicating the PMIC 300 chip temperature. As mentioned above, this temperature can be measured very accurately because the temperature sensor 314 is embedded in the same IC as the oscillator 315. For example, if the temperature of the PMIC 300 increases, the current, frequency, and PWM are adjusted by the PMIC 300 to control the transducer oscillation, which in turn controls the temperature. iv. Two external pins. v. An external NTC temperature sensor to monitor the temperature in the vicinity of the system.

[0253] In some examples, the ADC 318 samples one or more of the above sources sequentially, for example, in a round-robin manner. The ADC 318 samples the sources at a high rate, such as the rate of the oscillator 315, which may be between 20 kHz and 5 MHz.

[0254] In some examples, device 202 is configured to allow the device user or manufacturer to specify how many samples should be taken from each source for averaging. For example, a user may configure the system to take 512 samples from the rms current input, 64 samples from the battery voltage, 64 samples from the charger input voltage, 32 samples from the external pin, and 8 samples from the NTC pin. Additionally, the user may specify whether one of the above sources should be skipped.

[0255] In some examples, for each source, the user can specify two digital thresholds that divide the total range into multiple zones, such as three zones. The user can then configure the system to release an interrupt when the sampled value changes zone, for example, from zone 2 to zone 3.

[0256] Conventional ICs available on the market today are unable to implement the above features of the PMIC 300. Such flexible and granular sampling is of paramount importance when driving the ultrasonic transducer 215.

[0257] In this example, the PMIC 300 has 8-bit general-purpose digital input / output ports (GPIOs). Each port can be configured as a digital input and a digital output. Some of the ports also have analog input capabilities, as shown in the table in Figure 23.

[0258] The GPIO7-GPIO5 ports of the PMIC 300 can be used to set the address of a device on the communication (I2C) bus 302. Eight identical devices can then be used on the same I2C bus. This is a unique feature in the IC industry because it allows eight identical devices to be used on the same I2C bus without conflicting addresses. This is implemented by each device reading the state of GPIO7-GPIO5 during the first 100 μs after the PMIC 300 powers up and storing that portion of the address internally in the PMIC 300. After the PMIC 300 powers up, the GPIOs can be used for any other purpose.

[0259] As described above, the PMIC 300 includes a 6-channel LED driver 320. In this example, the LED driver 320 includes a 5V-tolerant N-channel metal-oxide semiconductor (NMOS) current source. The LED driver 320 is configured to set the LED current to four separate levels: 5 mA, 10 mA, 15 mA, and 20 mA. The LED driver 320 is configured to dim each LED channel with a 12-bit PWM signal, with or without gamma correction. The LED driver 320 is configured to vary the PWM frequency from 300 Hz to 1.5 kHz.

[0260] In this example, the PMIC 300 includes two independent 6-bit digital-to-analog converters (DACs) 327, 328 that are integrated into the PMIC 300. The purpose of the DACs 327, 328 is to output an analog voltage to operate the feedback path of an external regulator (e.g., a DC-DC boost converter 305, a buck converter, or an LDO). Additionally, in some examples, the DACs 327, 328 may also be used to dynamically adjust the overcurrent shutdown level of the bridge IC 301, as described below.

[0261] The output voltage of each DAC 327, 328 is programmable between 0V and 1.5V or between 0V and V_battery (Vbat). In this example, control of the DAC output voltage is via I2C commands. Having two DACs built into the PMIC 300 is unique and allows for dynamic monitoring and control of current. If either of the DACs 327, 328 were external chips, the speed would be subject to the same speed limitations imposed by the I2C protocol. The active power monitoring architecture of the device 202 operates at optimal efficiency when all these embedded features are within the PMIC. If they are external components, the active power monitoring architecture would be overall inefficient.

[0262] 24 of the accompanying drawings, the bridge IC 301 is a microchip with embedded power switching circuitry 333. In this example, the power switching circuitry 333 is an H-bridge 334 shown in FIG. 25 and described in detail below. However, it should be understood that other example bridge ICs 301 may incorporate alternative power switching circuits for the H-bridge 334, provided that the power switching circuitry performs an equivalent function for generating an AC drive signal to drive the ultrasonic transducer 215.

[0263] Bridge IC 301 includes a first phase terminal Phase A that receives a first phase output signal Phase A from the PWM signal generator subsystem of PMIC 300. Bridge IC 301 also includes a second phase terminal Phase B that receives a second phase output signal Phase B from the PWM signal generator subsystem of PMIC 300.

[0264] Bridge IC 301 includes a current sense circuit 335 that directly senses the current in H-bridge 334 and provides an RMS current output signal via the RMS_CURR pin of bridge IC 301. Current sense circuit 335 is configured for overcurrent monitoring and detects when the current through H-bridge 334 exceeds a predetermined threshold. The integration of power switching circuit 333 with H-bridge 334 and current sense circuit 335 all within the same embedded circuit of bridge IC 301 is a unique combination in the IC market. Currently, no other integrated circuit on the IC market includes an H-bridge with embedded circuitry for sensing the RMS current through the H-bridge.

[0265] Bridge IC 301 includes a temperature sensor 336 that includes over-temperature monitoring. Temperature sensor 336 is configured to shut down bridge IC 301 or disable at least a portion of bridge IC 301 if temperature sensor 336 detects that bridge IC 301 is operating at a temperature above a predetermined threshold. Temperature sensor 336 thus provides an integrated safety feature that prevents damage to bridge IC 301 or other components within transducer driver 202 if bridge IC 301 operates at an excessively high temperature.

[0266] Bridge IC 301 includes a digital state machine 337 integrally connected to power switching circuit 333. Digital state machine 337 receives Phase A and Phase B signals from PMIC 300 and an ENABLE signal from, for example, microcontroller 303. Digital state machine 337 generates timing signals based on the first phase output signal Phase A and the second phase output signal Phase B.

[0267] The digital state machine 337 outputs timing signals corresponding to the Phase A and Phase B signals, as well as a BRIDGE PR signal and a BRIDGE EN signal, to the power switching circuit 333 to control the power switching circuit 333. Thus, the digital state machine 337 outputs timing signals to the switches T1-T4 of the H-bridge circuit 334 to control the switches T1-T4 to turn on and off in sequence so that the H-bridge circuit outputs an AC drive signal to drive the ultrasonic transducer 215.

[0268] As described in more detail below, the switching sequence includes a free-floating period during which the first switch T1 and the second switch T1 are turned off and the third switch T3 and the fourth switch T4 are turned on to dissipate energy stored by the ultrasonic transducer 215.

[0269] Bridge IC 301 includes a test controller 338 that allows bridge IC 301 to be tested to determine whether embedded components within bridge IC 301 are operating correctly. Test controller 338 is coupled to the TEST_DATA, TEST_CLK, and TEST_LOAD pins so that bridge IC 301 can be connected to an external control device that feeds data into and out of bridge IC 301 to test the operation of bridge IC 301. Bridge IC 301 also includes a TEST BUS that allows the digital communication bus within bridge IC 301 to be tested via the TST_PAD pin.

[0270] Bridge IC 301 includes a power-on reset circuit (POR) 339 that controls the start-up operation of bridge IC 301. POR 339 ensures that bridge IC 301 starts up properly only if the supply voltage is within a predetermined range. If the power supply voltage is outside the predetermined range, for example, if the power supply voltage is too high, POR 339 delays the start-up of bridge IC 301 until the power supply voltage is within the predetermined range.

[0271] Bridge IC 301 includes a reference block (BG) 340 that provides a precise reference voltage for use by other subsystems of bridge IC 301.

[0272] Bridge IC 301 includes a current reference 341 that provides accurate current to other subsystems within bridge IC 301 , such as power switching circuit 333 and / or current sensor 335 .

[0273] Temperature sensor 336 continuously monitors the temperature of the silicon in bridge IC 301. If the temperature exceeds a predetermined temperature threshold, power switching circuit 333 is automatically switched off. Additionally, over-temperature can be reported to an external host to notify the external host that an over-temperature event has occurred.

[0274] A digital state machine (FSM) 337 generates timing signals for the power switching circuit 333 , which in this example are timing signals for controlling the H-bridge 334 .

[0275] Bridge IC 301 includes comparators 342, 343 that compare signals from various subsystems of bridge IC 301 with voltage and current references 340, 341 and provide reference output signals via pins of bridge IC 301.

[0276] Referring again to Figure 25 of the accompanying drawings, the H-bridge 334 in this example comprises four switches in the form of NMOS field effect transistor (FET) switches on either side of the H-bridge 334. The H-bridge 334 comprises four switches or transistors T1-T4 connected in an H-bridge configuration, with each transistor T1-T4 driven by a respective logic input A-D. The transistors T1-T4 are configured to be driven by a bootstrap voltage generated internally by two external capacitors Cb connected as shown in Figure 25.

[0277] H-bridge 334 has various power inputs and outputs that are connected to respective pins of bridge IC 301. H-bridge 334 receives the programmable voltage VBOOST output from boost converter 305 via a first power supply terminal labeled VBOOST in FIG. 25. H-bridge 334 has a second power supply terminal labeled VSS_P in FIG. 25.

[0278] The H-bridge 334 has outputs OUTP, OUTN configured to connect to respective terminals of the ultrasonic transducer 215 so that the AC drive signal output from the H-bridge 334 can drive the ultrasonic transducer 215.

[0279] The switching of the four switches or transistors T1-T4 is controlled by switching signals from digital state machine 337 via logic inputs A-D. While Figure 25 shows four transistors T1-T4, it should be understood that in other examples, H-bridge 334 incorporates a greater number of transistors or other switching components to implement the functionality of the H-bridge.

[0280] In this example, the H-bridge 334 operates at a switching power of 22 W to 50 W to provide an AC drive signal with enough power to optimally drive the ultrasonic transducer 215 at or near the resonant frequency of the ultrasonic transducer 215. The voltage switched by the H-bridge 334 in this example is ±15 V. In another example, the voltage is ±20 V.

[0281] Other voltage and power ratings for H-bridge 334 are contemplated and selected based on the intended purpose. In some examples, the voltage switched by H-bridge 334 in this example is between 100V and 500V with a power output of 200W to 2500W.

[0282] In this example, H-bridge 334 switches at a frequency between 20 kHz and 40 kHz, preferably 26 kHz. Apart from the bridge IC 301 described herein, conventional integrated circuit H-bridges available on the IC market cannot operate at a power of 22 V to 50 V in the frequency range of 26 kHz to 5 MHz.

[0283] Referring now to FIG. 26 of the accompanying drawings, the current sensor 335 comprises positive and negative current sensing resistors RshuntP, RshuntN connected in series with the respective high and low sides of the H-bridge 334, as shown in FIG. 25. The current sensing resistors RshuntP, RshuntN are low value resistors, in this example 0.1 Ω. The current sensor 335 comprises a first voltage sensor in the form of a first operational amplifier 344 that measures the voltage drop across the first current sensor resistor RshuntP, and a second voltage sensor in the form of a second operational amplifier 345 that measures the voltage drop across the second current sensor resistor RshuntN. In this example, the gain of each operational amplifier 344, 345 is 2 V / V. The output of each operational amplifier 344, 345 is, in this example, 1 mA / V. The current sensor 335 comprises a pull-down resistor Rcs, which in this example is 2 kΩ. The outputs of operational amplifiers 344, 345 provide an output CSout that passes through a low pass filter 346 that removes transients in the signal CSout. The output Vout of low pass filter 346 is the output signal of current sensor 335.

[0284] Thus, current sensor 335 measures the AC current flowing through H-bridge 334 and ultrasonic transducer 215, respectively. Current sensor 335 converts the AC current into an equivalent RMS output voltage (Vout) relative to ground. Current sensor 335 has high bandwidth capability because H-bridge 334 can operate at frequencies between 26 kHz and 5 MHz, preferably between 20 kHz and 40 kHz, preferably 26 kHz. The output Vout of current sensor 335 reports a positive voltage equal to the measured AC rms current flowing through ultrasonic transducer 215. The output voltage Vout of current sensor 335 is fed back to control circuitry within bridge IC 301, in this example, enabling bridge IC 301 to shut down H-bridge 334 if the current flowing through H-bridge 334, and therefore transducer 215, exceeds a predetermined threshold. Additionally, the overcurrent threshold event is reported to a first comparator 342 within bridge IC 301 so that bridge IC 301 can report the overcurrent event via the OVC_TRIGG pin of bridge IC 301.

[0285] Referring now to Figure 27 of the accompanying drawings, control of the H-bridge 334 will now be described, also with reference to an equivalent piezo model of the ultrasonic transducer 215.

[0286] To generate a positive voltage across the outputs OUTP, OUTN of the H-bridge 334 (note the direction of the arrows), as indicated by V_out in FIG. 27, the switching sequence of transistors T1-T4 via inputs A-D is as follows: 1. Positive output voltage across ultrasonic transducer 215: A-ON, B-OFF, C-OFF, D-ON. 2. Transition from positive output voltage to 0: A-OFF, B-OFF, C-OFF, D-ON. During this transition, if there is a switching error or delay in A, C is switched off first to minimize or avoid power loss by minimizing or avoiding current flowing through A and C. 3. Zero output voltage: A-OFF, B-OFF, C-ON, D-ON. During this zero output voltage phase, the output terminals OUTP, OUTN of the H-bridge 334 are grounded by the C and D switches, which remain on. This dissipates the energy stored by the capacitors in the equivalent circuit of the ultrasonic transducer and minimizes voltage overshoot in the switching waveform voltage applied to the ultrasonic transducer. 4. Transition from 0 to negative output voltage: A-OFF, B-OFF, C-ON, D-OFF. 5. Negative output voltage across ultrasonic transducer 215: A-OFF, B-ON, C-ON, D-OFF.

[0287] It will be appreciated that at high frequencies of 2 MHz to 5 MHz, the duration of each part of the switching sequence is very short, on the order of nanoseconds or picoseconds.

[0288] A graph showing the output voltages OUTP, OUTN of the H-bridge 334 according to the above switching sequence is shown in Figure 28 of the accompanying drawings. The zero output voltage portion of the switching sequence is included to accommodate energy stored by the ultrasonic transducer 215 (e.g., energy stored by a capacitor in the equivalent circuit of the ultrasonic transducer). As mentioned above, this minimizes voltage overshoot in the switching waveform voltage applied to the ultrasonic transducer, and therefore minimizes unnecessary power dissipation and heating in the ultrasonic transducer.

[0289] Minimizing or eliminating voltage overshoot also reduces the risk of damage to the transistors in the bridge IC 301 by preventing the transistors from experiencing voltages above their rated voltage. Furthermore, minimizing or eliminating voltage overshoot allows the bridge IC 301 to accurately drive the ultrasonic transducer in a manner that minimizes disruptions to the current-sensing feedback loop described herein. This allows the bridge IC 301 to drive the ultrasonic transducer with power ranging from 22 W to 50 W or 70 W. In some examples, the bridge IC 301 can drive the ultrasonic transducer at frequencies ranging from 20 kHz to 5 MHz. In other examples, the bridge IC 301 can drive the ultrasonic transducer at frequencies ranging from 20 kHz to 40 kHz.

[0290] The bridge IC 301 in this example is configured to be controlled by the PMIC 300 to operate in two different modes, referred to herein as forced mode and natural frequency mode. These two modes of operation are novel with respect to existing bridge ICs. In particular, the natural frequency mode is a key innovation that provides substantial benefits in the accuracy and efficiency of driving ultrasonic transducers compared to conventional devices.

[0291] Forced Frequency Mode (FFM) In forced frequency mode, the H-bridge 334 is controlled in the sequence described above, but at a user-selectable frequency. As a result, the H-bridge transistors T1-T4 are forcibly controlled to switch the output voltage across the ultrasonic transducer 215 regardless of the natural resonant frequency of the ultrasonic transducer 215. Thus, forced frequency mode allows the H-bridge 334 to drive an ultrasonic transducer 215 having a resonant frequency f1 at a different frequency f2.

[0292] Driving an ultrasonic transducer at a frequency different from its resonant frequency may be appropriate to adapt the operation to different applications. For example, it may be appropriate to drive an ultrasonic transducer at a frequency slightly off its resonant frequency (for mechanical reasons to prevent mechanical damage to the transducer). Alternatively, it may be appropriate to drive an ultrasonic transducer at a low frequency, but the ultrasonic transducer, due to its size, has a different natural resonant frequency.

[0293] The transducer driver 202 controls the bridge IC 301 to drive the ultrasonic transducer 215 in a forced frequency mode in response to the configuration of the transducer driver 202 for a particular application or a particular ultrasonic transducer.

[0294] Natural Frequency Mode (NFM) The following natural frequency operating mode is a significant development, offering benefits in improved accuracy and efficiency over conventional ultrasonic drivers available on the IC market today.

[0295] The natural frequency operating mode follows the same switching sequence described above, but the timing of the zero output portion of the sequence is adjusted to minimize or avoid problems that can arise due to current spikes in forced frequency mode operation. These current spikes occur when the voltage across the ultrasonic transducer 215 is switched to its opposite voltage polarity. Ultrasonic transducers that include piezo crystals have an electrical equivalent circuit that incorporates parallel-connected capacitors (see, for example, the piezo model in FIG. 27). When the voltage across the ultrasonic transducer is hard-switched from a positive voltage to a negative voltage, a high dV / dt can cause large currents to flow as the energy stored in the capacitor dissipates.

[0296] The natural frequency mode avoids hard switching the voltage across the ultrasonic transducer 215 from a positive voltage to a negative voltage (and vice versa). Instead, before applying the reverse voltage, the ultrasonic transducer 215 (piezo crystal) is left free-floating with zero voltage applied across its terminals for a free-floating period. The PMIC 300 sets the drive frequency of the bridge IC 301 such that the bridge 334 sets the free-floating period, so that current flow in the ultrasonic transducer 215 (due to energy stored in the piezo crystal) reverses the voltage across the terminals of the ultrasonic transducer 215 during the free-floating period.

[0297] As a result, when the H-bridge 334 applies a negative voltage to the terminals of the ultrasonic transducer 215, the ultrasonic transducer 215 (the capacitor in the equivalent circuit) is already back-charged and there is no high dV / dt, so no current spike occurs.

[0298] However, it should be understood that when the ultrasonic transducer 215 is first activated, it takes time for the charge in the ultrasonic transducer 215 (piezo crystal) to accumulate. Therefore, the ideal situation in which the energy in the ultrasonic transducer 215 reverses the voltage during the free-floating period occurs only after oscillations in the ultrasonic transducer 215 have accumulated charge. To accommodate this, when the bridge IC 301 first activates the ultrasonic transducer 215, the PMIC 300 controls the power delivered to the ultrasonic transducer 215 through the H-bridge 334 to a first value, which is a low value (e.g., 5 V). The PMIC 300 then controls the power delivered to the ultrasonic transducer 215 through the H-bridge 334 to increase to a second value (e.g., 15 V) higher than the first value over a period of time to accumulate the energy stored in the ultrasonic transducer 215. A current spike still occurs during this ramp of oscillation until the current in the ultrasonic transducer 215 is fully developed. However, by using a low first voltage at start-up, these current spikes are kept low enough to minimize their impact on the operation of the ultrasonic transducer 215.

[0299] To implement the natural frequency mode, the transducer driver 202 precisely controls the frequency of the oscillator 315 and the duty cycle (ratio of on time to free-floating time) of the AC drive signal output from the H-bridge 334. In this example, the transducer driver 202 implements three control loops to adjust the oscillator frequency and duty cycle so that the voltage reversal at the terminals of the ultrasonic transducer 215 is as precise as possible and current spikes are minimized or avoided whenever possible. The precise control of the oscillator and duty cycle using control loops is a significant advancement in the field of IC ultrasonic drivers.

[0300] During the natural frequency operating mode, the current sensor 335 senses the current through the ultrasonic transducer 215 during the free-floating period. The digital state machine 337 adapts the timing signals to switch on either the first switch T1 or the second switch T2 when the current sensor 335 senses that the current flowing through the ultrasonic transducer 215 is zero during the free-floating period.

[0301] 29 of the accompanying drawings shows oscillator voltage waveform 347 (V(osc)), switching waveform 348 resulting from the on and off of left high switch T1 of H-bridge 334, and switching waveform 349 resulting from the on and off of right high switch T2 of H-bridge 334. During the intervening free-floating period 350, both high switches T1, T2 of H-bridge 334 are turned off (free-floating phase). The duration of free-floating period 350 is controlled by the magnitude of free-floating control voltage 351 (Vphioff).

[0302] Figure 30 of the accompanying drawings shows the voltage waveform 352 at a first terminal of the ultrasonic transducer 215 (the voltage waveform is inverted at a second terminal of the ultrasonic transducer 215) and the piezo current 353 flowing through the ultrasonic transducer 215. The piezo current 353 represents an (almost) ideal sinusoidal waveform (which is never possible in forced frequency mode or with any bridge on the IC market).

[0303] Before the sine wave of the piezoelectric current 353 reaches zero, the left high switch T1 of the H-bridge 334 is turned off (here, switch T1 is turned off when the piezoelectric current 353 is approximately 6 A). The remaining piezoelectric current 353 flowing in the ultrasonic transducer 215 due to the energy stored in the ultrasonic transducer 215 (the capacitor of the piezoelectric equivalent circuit) is responsible for the voltage reversal during the free-floating period 350. The piezoelectric current 353 decays to zero during the free-floating period 350 and then decays into a negative current flow domain. The terminal voltage at the ultrasonic transducer 215 drops from the supply voltage (19 V in this case) to less than 2 V, and this drop stops when the piezoelectric current 353 reaches zero. This is the perfect time to turn on the low-side switch T3 of the H-bridge 334 to minimize or avoid current spikes.

[0304] Compared to the forced frequency mode described above, the natural frequency mode has at least three advantages. 1. Current spikes associated with hard switching of package capacitors are significantly reduced or avoided entirely. 2. Power losses due to hard switching are almost eliminated. 3. The frequency is regulated by a control loop to keep it close to the resonance of the piezo crystal (i.e., the natural resonant frequency of the piezo crystal).

[0305] For frequency regulation by a control loop (benefit 3 above), the PMIC 300 starts by controlling the bridge IC 301 to drive the ultrasonic transducer 215 at a frequency above the resonance of the piezo crystal. The PMIC 300 then controls the bridge IC 301 to attenuate / reduce the frequency of the AC drive signal during startup. As soon as the frequency approaches the resonant frequency of the piezo crystal, a piezo current is rapidly generated / increased. Once the piezo current is high enough to cause the desired voltage reversal, the frequency attenuation / reduction is stopped by the PMIC 300. The control loop in the PMIC 300 then takes over regulating the frequency and duty cycle of the AC drive signal.

[0306] In forced frequency mode, the power delivered to the ultrasonic transducer 215 is controlled through duty cycle and / or frequency shifting and / or by varying the supply voltage. However, in this example, in natural frequency mode, the power delivered to the ultrasonic transducer 215 is controlled only by the supply voltage.

[0307] In this example, during the setup phase of the transducer driver's operation, bridge IC 301 is configured to measure the length of time it takes for the current through ultrasonic transducer 215 to fall to zero when first switch T1 and second switch T2 are turned off and third switch T3 and fourth switch T4 are turned on. Bridge IC 301 then sets the length of time of the free-floating period to be equal to the measured length of time.

[0308] 31 of the accompanying drawings, the PMIC 300 and bridge IC 301 in this example are designed to work together as a companion chip set. The PMIC 300 and bridge IC 301 are electrically connected to each other for communication with each other. In this example, there are interconnections between the PMIC 300 and bridge IC 301 that enable two categories of communication: 1. Control Signal 2. Feedback signal

[0309] The connections between the Phase_A and Phase_B pins of PMIC 300 and bridge IC 301 carry the PWM modulated control signals that drive H-bridge 334. The connection between the EN_BR pin of PMIC 300 and bridge IC 301 carries the EN_BR control signal that triggers the opening of H-bridge 334. The timing between the Phase_A, Phase_B, and EN_BR control signals is critical and is handled by the digital bridge control of PMIC 300.

[0310] The connections between the CS, OC, and OT pins of the PMIC 300 and the bridge IC 301 carry the CS (current sense), OC (overcurrent), and OT (overtemperature) feedback signals from the bridge IC 301 back to the PMIC 300. Most notably, the CS (current sense) feedback signal comprises a voltage equal to the rms current through the ultrasonic transducer 215, as measured by the current sensor 335 of the bridge IC 301.

[0311] The OC (overcurrent) and OT (overtemperature) feedback signals are digital signals that indicate either an overcurrent or overvoltage event has been detected by bridge IC 301. In this example, the overcurrent and overtemperature thresholds are set by external resistors. Alternatively, the thresholds can also be dynamically set in response to a signal passed from one of two DAC channels VDAC0, VDAC1 from PMIC 300 to the OC_REF pin of bridge IC 301.

[0312] In this example, the design of PMIC 300 and bridge IC 301 allows the pins of these two integrated circuits to be directly connected to each other (e.g., via copper tracks on a PCB), thereby minimizing or eliminating delays in the communication of signals between PMIC 300 and bridge IC 301. This provides a significant speed advantage over traditional bridges on the IC market, which are typically controlled by signals over a digital communication bus. For example, a standard I2C bus is clocked at 400 kHz, which is too slow to communicate data sampled at high-speed clocks of 2 MHz to 5 MHz.

[0313] While examples of the present disclosure are described above with respect to microchip hardware, it should be understood that other examples of the present disclosure include methods of operating each microchip's components and subsystems to perform the functions described herein, such as operating the PMIC 300 and bridge IC 301 in either forced frequency mode or natural frequency mode.

[0314] We now describe some example operations of the system 1. More specifically, to optimize the yield of hydrogen gas produced by the system 1, the following process sequences are performed by the system 1: 1. The system is started and the main controller coordinates the electrolysis reaction and control of the transducer driver 202. 2. Each transducer driver 202 sequentially drives its respective ultrasonic transducer 215 at multiple drive frequencies to find the optimal (resonant) frequency at which the ultrasonic transducer 215 most efficiently converts electrical power into kinetic energy. At resonance, the maximum available electrical power is converted into kinetic energy by the ultrasonic transducer 215. The transducer driver 202 then drives the ultrasonic transducer 215 at the optimal (resonant) frequency for efficiency to emit ultrasonic waves that cause agitation and / or cavitation in the aqueous solution 102. 3. The main controller 2 monitors the hydrogen gas pressure signal and / or the oxygen gas pressure to detect the volume or rate of hydrogen gas and / or oxygen gas produced by the system 1. 4. If the volume or rate of hydrogen gas and / or oxygen gas produced by system 1 is less than expected or optimal, main controller 2 controls the power controller to increase the power (potential difference) between cathode 105 and anode 107. Otherwise, the power (potential difference) between cathode 105 and anode 107 is maintained. 5. The main controller 2 controls the power controller to increase the power (potential difference) between the cathode 105 and the anode 107, and if there is no change in the rate of production of hydrogen gas and / or oxygen gas, controls each transducer controller 202 to increase the power of the drive signal to the ultrasonic transducer to increase the intensity of the ultrasonic waves in the reaction vessel 101. 6. If the production rate of hydrogen gas and / or oxygen gas increases, the new parameters (power across the anode / cathode and power of the ultrasonic transducer drive signal) are maintained; if not, steps 4 and 5 are repeated until the expected or optimal production rate of hydrogen gas and / or oxygen gas is achieved. 7. If after x iterations of step 6 there is no increase in the rate of production of hydrogen gas and / or oxygen gas, the last set of parameters is maintained. 8. If the rate of production of hydrogen gas and / or oxygen gas begins to decrease along with the maximum power input (across the anode / cathode and / or in the ultrasonic transducer drive signal), the main controller 2 controls the power controller and each transducer driver 202 to gradually reduce the power of the system 1. 9. Production ends.

[0315] The volume of hydrogen produced by some example systems of the present disclosure can be calculated as follows:

[0316] Stoichiometry of water electrolysis:

[0317] [ka]

[0318] For every two moles of water, two moles of hydrogen are produced.

[0319] One mole of water weighs 18g (18mL). One mole of hydrogen weighs 4g (4mL).

[0320] For an inlet water flow rate of 10 L / h, the output hydrogen gas at 70% efficiency is:

[0321]

number

[0322] The rate of hydrogen gas production is a function of the input water flow rate (taking into account the efficiency of the system).

[0323] The output flow rate equation can be derived from the following equation:

[0324]

number

[0325] The example systems of the present disclosure do not require desalination of seawater prior to electrolysis. Seawater can be used directly as the electrolyte. The transducer driver and feedback loop configuration determine and implement the optimal balance between the frequency and intensity of the ultrasound waves flowing through the electrolyte solution to maximize hydrogen production. In some examples, a frequency of 20 kHz to 40 kHz is set by the transducer driver to create the optimal balance for high electrolysis reaction rates. In some examples, 0.1 Wcm -2 ±0.02Wcm -2 The frequency of the intensity is set by the transducer driver to produce the optimum balance for high electrolysis reaction rates.

[0326] The foregoing outlines features of several examples or embodiments to enable those skilled in the art to better understand various aspects of the present disclosure. Those skilled in the art will appreciate that they may readily use this disclosure as a basis for designing or modifying other processes and structures to carry out the same purposes and / or achieve the same advantages of the various examples or embodiments presented herein. Those skilled in the art should also appreciate that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the present disclosure.

[0327] Although the subject matter has been described in language specific to structural features or methodological acts, it is to be understood that the appended claimed subject matter is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing at least some of the claims.

[0328] Various operations of example or embodiment are provided herein. The order in which some or all of the operations are described should not be construed as implying that these operations are necessarily order dependent. It will be understood that alternative orderings may have the benefit of this description. Furthermore, it will be understood that not all operations are necessarily present in each embodiment provided herein. It will also be understood that not all operations are required in some example or embodiment.

[0329] Furthermore, "exemplary" is used herein to mean serving as an example, instance, illustration, or the like, and is not necessarily advantageous. When used in this application, "or" is intended to mean an inclusive "or" rather than an exclusive "or." Furthermore, "a" and "an," as used in this application and the appended claims, are generally construed to mean "one or more" unless otherwise specified or unless it is clear from the context that the singular form is intended. Also, at least one of A and B, etc., generally refers to A or B, or both A and B. Furthermore, to the extent that "includes," "having," "has," "with," or variations thereof are used, such terms are intended to be inclusive in the same manner as the term "comprising." Also, unless otherwise specified, "first," "second," etc. are not intended to imply any temporal or spatial aspect, order, or the like; such terms are merely used as identifiers, names, or the like for features, elements, items, etc. For example, a first element and a second element generally correspond to element A and element B, or two different or two identical or the same element.

[0330] Also, while the present disclosure has been shown and described with respect to one or more implementations, equivalent changes and modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. The present disclosure includes all such modifications and variations and is limited only by the scope of the following claims. In particular, with respect to the various functions performed by the above-described features (e.g., elements, resources, etc.), the terms used to describe such features are intended, unless otherwise specified, to correspond to any feature that is not structurally equivalent to the disclosed structure but performs the specified function (e.g., functionally equivalent) of the described feature. In addition, while a particular feature of the present disclosure may be disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of other implementations, as may be desired or advantageous for any given or particular application.

[0331] Examples or embodiments of the subject matter and functional operations described herein can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, or in combinations of one or more of them, including the structures disclosed herein and their structural equivalents.

[0332] Some examples or embodiments are implemented using one or more modules of computer program instructions encoded on a computer-readable medium for execution by or to control the operation of a data processing apparatus. The computer-readable medium may be an article of manufacture, such as a hard drive in a computer system or an embedded system. The computer-readable medium may be obtained separately and later encoded with one or more modules of computer program instructions, such as by delivery of one or more modules of computer program instructions over a wired or wireless network. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, or a combination of one or more thereof.

[0333] The terms "computing device" and "data processing apparatus" encompass all apparatus, devices, and machines for processing data, including, by way of example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, an apparatus can include code that creates an execution environment for the computer program in question, such as code that constitutes processor firmware, a protocol stack, a database management system, an operating system, a runtime environment, or one or more combinations thereof. Additionally, an apparatus can employ a variety of different computing model infrastructures, such as web services, distributed computing, and grid computing infrastructures.

[0334] The processes and logic flows described herein may be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output.

[0335] Processors suitable for executing a computer program include, by way of example, both general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor receives instructions and data from a read-only memory or a random-access memory, or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer also includes one or more mass storage devices, such as magnetic, magneto-optical, or optical disks, for storing data, or is operatively coupled to receive data from them, transfer data to them, or both. However, a computer need not have such devices. Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices.

[0336] As used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. These terms are not to be interpreted as excluding the presence of other features, steps or components.

[0337] The present invention may also broadly reside in any and all combinations of two or more of the parts, elements, steps, examples, and / or features referred to or indicated herein, individually or collectively. In particular, one or more features in any of the embodiments described herein may be combined with one or more features from any other embodiment(s) described herein.

[0338] Protection may be sought for any feature disclosed in any one or more of the publications referenced herein in connection with this disclosure.

[0339] Although specific exemplary embodiments of the present invention have been described, the appended claims are not intended to be limited to only these embodiments. The claims are to be interpreted literally, intentionally, and / or to encompass equivalents.

[0340] Typical features Representative features are described in the following clauses, which may be combined independently or in any combination with one or more features disclosed in the text and / or drawings of this specification. 1. A system for producing hydrogen gas, the system comprising: a reaction vessel containing an aqueous solution; a cathode at least partially disposed within the reaction vessel, a portion of the cathode having an outer surface immersed in and in electrical contact with the aqueous solution to form an interface for a reduction reaction to reduce H ions to produce hydrogen gas at the cathode; an anode at least partially disposed within the reaction vessel, a portion of the anode immersed in and in electrical contact with the aqueous solution to form an interface for an oxidation reaction to oxidize OH ions at the anode to produce oxygen gas, the cathode and anode configured to receive power from a power source; a polymer electrolyte membrane (PEM) disposed between the cathode and the anode to separate H+ and OH- ions in an aqueous solution to form partitioned regions within the reactor, the PEM having a higher concentration of H+ ions than OH- ions in the aqueous solution adjacent the cathode; a first ultrasonic transducer at least partially disposed within the reaction vessel, the first ultrasonic transducer positioned a predetermined distance from the cathode and oriented to emit ultrasonic waves at least partially toward an outer surface of the cathode to agitate the aqueous solution proximate the outer surface of the cathode and remove hydrogen gas bubbles formed on the outer surface of the cathode to expose the outer surface of the cathode to additional H ions to generate hydrogen gas; a second ultrasonic transducer disposed at least partially within the reactor, the second ultrasonic transducer positioned a predetermined distance from the anode and oriented to emit ultrasonic waves at least partially toward an outer surface of the anode to cause cavitation in an aqueous solution proximate the outer surface of the anode, the cavitation weakening hydrogen bonds between water molecules in the aqueous solution to separate individual water molecules available for interaction with the anode and undergoing an oxidation reaction at the anode to oxidize OH ions at the anode to form oxygen gas; a plurality of transducer drivers each electrically coupled to a respective one of the first ultrasonic transducer or the second ultrasonic transducer to drive the ultrasonic transducer to generate ultrasonic waves, wherein the transducer drivers include: an H-bridge circuit connected to the ultrasonic transducer, the H-bridge circuit generating an AC drive signal to drive the ultrasonic transducer to generate and transmit ultrasonic waves; A microchip connected to an H-bridge circuit and controlling the H-bridge circuit to generate an AC drive signal, the microchip comprising: 1. An oscillator, comprising: A main clock signal; a first phase clock signal that is initially high during a positive half-cycle of the main clock signal and low during a negative half-cycle of the main clock signal; a second phase clock signal that is high a second time during the negative half-period of the main clock signal and low during the positive half-period of the main clock signal, wherein the phases of the first phase clock signal and the second phase clock signal are center-aligned; and a pulse width modulation (PWM) signal generator subsystem, comprising: a delay locked loop that uses a first phase clock signal and a second phase clock signal to generate a double frequency clock signal that is twice the frequency of the main clock signal, the delay locked loop synchronizing the first phase clock signal and the second phase clock signal, the delay locked loop adjusting the frequency and duty cycle of the first phase clock signal and the second phase clock signal in response to a driver control signal to generate a first phase output signal and a second phase output signal, the first phase output signal and the second phase output signal being configured to drive an H-bridge circuit to generate an AC drive signal for driving an ultrasonic transducer; a first phase output signal terminal for outputting a first phase output signal to an H-bridge circuit; a second phase output signal terminal for outputting a second phase output signal to the H-bridge circuit; a PWM signal generator subsystem including: a feedback input terminal for receiving a feedback signal from the H-bridge circuit, the feedback signal being indicative of the operation of the H-bridge circuit or a parameter of the AC drive signal when the H-bridge circuit is driving the ultrasonic transducer with the AC drive signal; an analog-to-digital converter (ADC) subsystem, comprising: at least one ADC input terminal for receiving an analog signal, the ADC input terminal being connected to the feedback input terminal such that the ADC subsystem receives the feedback signal from the H-bridge circuit, the ADC subsystem sampling the analog signal received at the ADC input terminal at a sampling frequency proportional to the frequency of the main clock signal, and the ADC subsystem generating an ADC digital signal using the sampled analog signal; an ADC subsystem comprising: a digital processor subsystem that receives an ADC digital signal from the ADC subsystem and processes the ADC digital signal to generate a driver control signal, the digital processor subsystem communicating the driver control signal to the PWM signal generator subsystem to control the PWM signal generator subsystem; 1. A digital-to-analog converter (DAC) subsystem comprising: a digital-to-analog converter (DAC) that converts the digital control signals generated by the digital processor subsystem into analog voltage control signals to control a voltage regulator circuit that generates a voltage for modulation by the H-bridge circuit; and a DAC output terminal that outputs an analog voltage control signal to control a voltage regulator circuit to generate a predetermined voltage for modulation by an H-bridge circuit to drive an ultrasonic transducer to control cavitation in an aqueous solution in response to a feedback signal indicative of operation of the ultrasonic transducer. 2. A system for producing hydrogen gas, the system comprising: a reaction vessel containing an aqueous solution; a cathode at least partially disposed within the reaction vessel, a portion of the cathode having an outer surface immersed in and in electrical contact with the aqueous solution to form an interface for a reduction reaction to reduce H ions to produce hydrogen gas at the cathode; an anode at least partially disposed within the reaction vessel, a portion of the anode immersed in and in electrical contact with the aqueous solution to form an interface for an oxidation reaction to oxidize OH ions at the anode to produce oxygen gas, the cathode and anode configured to receive power from a power source; a plurality of first ultrasonic transducers disposed at least partially within the reaction vessel, each first ultrasonic transducer positioned a predetermined distance from the cathode and oriented such that each first ultrasonic transducer emits and conducts ultrasonic waves at least partially through the aqueous solution toward an outer surface of the cathode to agitate the aqueous solution proximate the outer surface of the cathode and remove hydrogen gas bubbles formed on the outer surface of the cathode to expose the outer surface of the cathode to additional H ions to generate hydrogen gas; a plurality of second ultrasonic transducers disposed at least partially within the reaction vessel, the second ultrasonic transducers being positioned a predetermined distance from the anode and oriented to emit ultrasonic waves at least partially toward an outer surface of the anode to cause cavitation in an aqueous solution proximate the outer surface of the anode, the cavitation weakening hydrogen bonds between water molecules in the aqueous solution to separate individual water molecules available for interaction with the anode and undergoing an oxidation reaction at the anode to oxidize OH ions at the anode to form oxygen gas; a plurality of transducer drivers each electrically coupled to a respective one of the ultrasonic transducers to drive the ultrasonic transducers to generate ultrasonic waves, each transducer driver comprising: an H-bridge circuit connected to each one of the ultrasonic transducers, the H-bridge circuit generating an AC drive signal for driving the ultrasonic transducer to generate and transmit ultrasonic waves; A microchip connected to an H-bridge circuit and controlling the H-bridge circuit to generate an AC drive signal, the microchip comprising: 1. An oscillator, comprising: A main clock signal; a first phase clock signal that is initially high during a positive half-cycle of the main clock signal and low during a negative half-cycle of the main clock signal; a second phase clock signal that is high a second time during the negative half-period of the main clock signal and low during the positive half-period of the main clock signal, wherein the phases of the first phase clock signal and the second phase clock signal are center-aligned; and a pulse width modulation (PWM) signal generator subsystem, comprising: a delay locked loop that uses a first phase clock signal and a second phase clock signal to generate a double frequency clock signal that is twice the frequency of the main clock signal, the delay locked loop synchronizing the first phase clock signal and the second phase clock signal, the delay locked loop adjusting the frequency and duty cycle of the first phase clock signal and the second phase clock signal in response to a driver control signal to generate a first phase output signal and a second phase output signal, the first phase output signal and the second phase output signal being configured to drive an H-bridge circuit to generate an AC drive signal for driving an ultrasonic transducer; a first phase output signal terminal for outputting a first phase output signal to an H-bridge circuit; a second phase output signal terminal for outputting a second phase output signal to the H-bridge circuit; a PWM signal generator subsystem comprising: a feedback input terminal for receiving a feedback signal from the H-bridge circuit, the feedback signal being indicative of the operation of the H-bridge circuit or a parameter of the AC drive signal when the H-bridge circuit is driving a respective one of the ultrasonic transducers with the AC drive signal; an analog-to-digital converter (ADC) subsystem, comprising: at least one ADC input terminal for receiving an analog signal, the ADC input terminal being connected to the feedback input terminal such that the ADC subsystem receives the feedback signal from the H-bridge circuit, the ADC subsystem sampling the analog signal received at the ADC input terminal at a sampling frequency proportional to the frequency of the main clock signal, and the ADC subsystem generating an ADC digital signal using the sampled analog signal; an ADC subsystem comprising: a digital processor subsystem that receives an ADC digital signal from the ADC subsystem and processes the ADC digital signal to generate a driver control signal, the digital processor subsystem communicating the driver control signal to the PWM signal generator subsystem to control the PWM signal generator subsystem; 1. A digital-to-analog converter (DAC) subsystem comprising: a digital-to-analog converter (DAC) that converts the digital control signals generated by the digital processor subsystem into analog voltage control signals to control a voltage regulator circuit that generates a voltage for modulation by the H-bridge circuit; and a DAC output terminal that outputs an analog voltage control signal to control a voltage regulator circuit to generate a predetermined voltage for modulation by an H-bridge circuit to drive a respective one of the ultrasonic transducers to control cavitation in the aqueous solution in response to a feedback signal indicative of operation of the respective one of the ultrasonic transducers. 3. The system is 3. The system of claim 2, further comprising a polymer electrolyte membrane (PEM) disposed within the reactor between the cathode and the anode to separate H+ ions and OH- ions in the aqueous solution to form a partition region within the reactor, the aqueous solution in the partition region adjacent the cathode having a higher concentration of H+ ions than OH- ions. 4. A system described in any one of clauses 1 to 3, wherein the transducer driver drives the ultrasonic transducer at a frequency of 20 kHz to 40 kHz. 5. A system described in any one of clauses 1 to 4, wherein each first ultrasonic transducer is positioned at a distance from the outer surface of the cathode equal to one wavelength of the ultrasonic waves emitted by the ultrasonic transducer. 6. A system described in any one of clauses 1 to 4, wherein each first ultrasonic transducer is positioned at a distance from the outer surface of the cathode equal to a multiple of the wavelengths of the ultrasonic waves emitted by the ultrasonic transducer. 7. A system described in any one of clauses 1 to 6, wherein each second ultrasonic transducer is positioned at a distance from the outer surface of the anode equal to one wavelength of the ultrasonic waves emitted by the ultrasonic transducer. 8. A system described in any one of clauses 1 to 7, wherein each second ultrasonic transducer is positioned at a distance from the outer surface of the anode equal to a multiple of the wavelengths of the ultrasonic waves emitted by the ultrasonic transducer. 9. A system described in any one of clauses 1 to 8, wherein each first ultrasonic transducer is oriented to emit ultrasonic waves in a direction transverse to the longitudinal length of the cathode. 10. A system described in any one of clauses 1 to 9, wherein each second ultrasonic transducer is oriented to emit ultrasonic waves in a direction transverse to the longitudinal length of the anode. 11. The system 11. The system of any one of clauses 1 to 10, comprising a main controller that controls the power applied between the anode and the cathode, the main controller being coupled to each transducer driver to control the operation of each transducer driver to optimize the efficiency of hydrogen gas generation. 12. The system a hydrogen gas collector disposed at least partially within the reaction vessel for collecting hydrogen gas produced within the reaction vessel; 12. The system of claim 11, comprising: a hydrogen gas pressure sensor that senses the pressure of hydrogen gas in the hydrogen gas collector, the hydrogen gas pressure sensor being electrically coupled to the main controller and providing a hydrogen gas pressure signal to the main controller in a feedback loop. 13. The system an oxygen gas collector disposed at least partially within the reaction vessel to collect oxygen gas produced within the reaction vessel; 13. The system of claim 11 or 12, comprising: an oxygen gas pressure sensor that senses the pressure of oxygen gas in the oxygen gas collector, the oxygen gas pressure sensor being electrically coupled to the main controller and providing an oxygen gas pressure signal to the main controller in a feedback loop. 14. The transducer driver 14. The system of any one of clauses 1 to 13, comprising a frequency divider connected to the oscillator to receive a main clock signal from the oscillator, dividing the main clock signal by a predetermined divisor amount, and outputting a frequency reference signal to the delay locked loop. 15. The system of clause 14, wherein the delay locked loop comprises a plurality of delay lines connected end to end, the total delay of the delay lines being equal to the period of the main clock signal. 16. The system of clause 15, wherein the delay-locked loop adjusts the duty cycle of the first phase clock signal and the second phase clock signal in response to the driver control signal by varying the delay of each delay line in the delay-locked loop. 17. A system as described in any one of clauses 1 to 16, wherein the feedback input terminal receives a feedback signal from the H-bridge circuit in the form of a voltage indicative of the rms current of the AC drive signal driving the ultrasonic transducer. 18. A system as described in any one of clauses 1 to 17, wherein the ADC subsystem comprises at least one further ADC input terminal for receiving a feedback signal indicative of at least one of the voltage of a battery connected to the system or the voltage of a battery charger connected to the system. 19. A system for producing hydrogen gas, comprising: a housing including a first internal chamber and a second internal chamber; an anode at least partially disposed within the first internal chamber, a portion of the anode in electrical contact with water in the first internal chamber to form an interface for an oxidation reaction that oxidizes OH ions to produce oxygen gas at the anode, the anode being porous; a cathode at least partially disposed within the second internal chamber, the cathode being porous, and the cathode and the anode being configured to receive power from a power source; a polymer electrolyte membrane (PEM) disposed between the cathode and the anode, the PEM allowing H+ ions to migrate from the anode to the cathode and the PEM preventing OH- ions from migrating from the anode to the cathode; an ultrasonic transducer disposed at least partially within the first internal chamber, the ultrasonic transducer positioned a predetermined distance from the anode and oriented to emit ultrasonic waves at least partially toward a surface of the anode to create cavitation in the water adjacent to the exterior surface of the anode, the cavitation weakening hydrogen bonds between water molecules to separate individual water molecules available for interaction with the anode and undergoing an oxidation reaction at the anode to oxidize OH ions at the anode to form oxygen gas; a transducer driver electrically coupled to the ultrasonic transducer and configured to drive the ultrasonic transducer to generate ultrasonic waves; a hydrogen gas outlet that allows hydrogen gas to be produced in the second internal chamber when H+ ions are reduced at the cathode to produce hydrogen gas. 20. The system is a transducer driver coupled to the ultrasonic transducer, the transducer driver comprising: an H-bridge circuit connected to the ultrasonic transducer, the H-bridge circuit generating an AC drive signal to drive the ultrasonic transducer to generate and transmit ultrasonic waves; A microchip connected to an H-bridge circuit and controlling the H-bridge circuit to generate an AC drive signal, the microchip comprising: 1. An oscillator, comprising: A main clock signal; a first phase clock signal that is initially high during a positive half-cycle of the main clock signal and low during a negative half-cycle of the main clock signal; a second phase clock signal that is high a second time during the negative half-period of the main clock signal and low during the positive half-period of the main clock signal, wherein the phases of the first phase clock signal and the second phase clock signal are center-aligned; and a pulse width modulation (PWM) signal generator subsystem, comprising: a delay locked loop that uses a first phase clock signal and a second phase clock signal to generate a double frequency clock signal that is twice the frequency of the main clock signal, the delay locked loop synchronizing the first phase clock signal and the second phase clock signal, the delay locked loop adjusting the frequency and duty cycle of the first phase clock signal and the second phase clock signal in response to a driver control signal to generate a first phase output signal and a second phase output signal, the first phase output signal and the second phase output signal being configured to drive an H-bridge circuit to generate an AC drive signal for driving an ultrasonic transducer; a first phase output signal terminal for outputting a first phase output signal to an H-bridge circuit; a second phase output signal terminal for outputting a second phase output signal to the H-bridge circuit; a PWM signal generator subsystem including: a feedback input terminal for receiving a feedback signal from the H-bridge circuit, the feedback signal being indicative of the operation of the H-bridge circuit or a parameter of the AC drive signal when the H-bridge circuit is driving the ultrasonic transducer with the AC drive signal; an analog-to-digital converter (ADC) subsystem, comprising: at least one ADC input terminal for receiving an analog signal, the ADC input terminal being connected to the feedback input terminal such that the ADC subsystem receives the feedback signal from the H-bridge circuit, the ADC subsystem sampling the analog signal received at the ADC input terminal at a sampling frequency proportional to the frequency of the main clock signal, and the ADC subsystem generating an ADC digital signal using the sampled analog signal; an ADC subsystem comprising: a digital processor subsystem that receives an ADC digital signal from the ADC subsystem and processes the ADC digital signal to generate a driver control signal, the digital processor subsystem communicating the driver control signal to the PWM signal generator subsystem to control the PWM signal generator subsystem; 1. A digital-to-analog converter (DAC) subsystem comprising: a digital-to-analog converter (DAC) that converts the digital control signals generated by the digital processor subsystem into analog voltage control signals to control a voltage regulator circuit that generates a voltage for modulation by the H-bridge circuit; 20. The system of claim 19, further comprising a DAC subsystem comprising a DAC output terminal that outputs an analog voltage control signal to control a voltage regulator circuit to generate a predetermined voltage for modulation by an H-bridge circuit to drive an ultrasonic transducer to control cavitation in an aqueous solution in response to a feedback signal indicative of operation of the ultrasonic transducer. 21. A system for producing hydrogen, comprising: a reaction vessel containing an aqueous solution; a first electrode disposed at least partially within the reaction vessel; a second electrode disposed at least partially within the reaction vessel, the first electrode and the second electrode configured to receive power from a DC power source; a first gas collector disposed at least partially within the reaction vessel for collecting hydrogen gas produced at the first electrode due to the electrolysis reaction at the first electrode; an ultrasonic transducer located a predetermined distance from the first electrode and oriented to emit ultrasonic waves at least partially toward the first electrode; a driver device electrically coupled to the ultrasonic transducer for driving the ultrasonic transducer at a frequency that generates ultrasonic waves that cause cavitation in the electrolyte solution, the cavitation increasing the rate of the electrolysis reaction and increasing the volume of hydrogen gas produced at the first electrode. 22. A system for producing hydrogen gas, comprising: a reaction vessel containing an aqueous solution; a cathode at least partially disposed within the reaction vessel, a portion of the cathode having an outer surface immersed in and in electrical contact with the aqueous solution to form an interface for a reduction reaction to reduce H ions to produce hydrogen gas at the cathode; an anode at least partially disposed within the reaction vessel, a portion of the anode immersed in and in electrical contact with the aqueous solution to form an interface for an oxidation reaction to oxidize OH ions at the anode to produce oxygen gas, the cathode and anode configured to receive power from a power source; a polymer electrolyte membrane (PEM) disposed between the cathode and the anode to separate H+ and OH- ions in an aqueous solution to form partitioned regions within the reactor, the PEM having a higher concentration of H+ ions than OH- ions in the aqueous solution adjacent the cathode; a first ultrasonic transducer at least partially disposed within the reaction vessel, the first ultrasonic transducer positioned a predetermined distance from the cathode and oriented so that the first ultrasonic transducer emits ultrasonic waves at least partially toward an outer surface of the cathode to agitate the aqueous solution proximate to the outer surface of the cathode and remove hydrogen gas bubbles formed on the outer surface of the cathode, exposing the outer surface of the cathode to additional H ions to generate hydrogen gas; and a second ultrasonic transducer disposed at least partially within the reaction vessel, the second ultrasonic transducer positioned a predetermined distance from the anode and oriented to emit ultrasonic waves at least partially toward an outer surface of the anode to create cavitation in an aqueous solution proximate to the outer surface of the anode, the cavitation weakening hydrogen bonds between water molecules in the aqueous solution to separate individual water molecules available for interaction with the anode and undergoing an oxidation reaction at the anode to oxidize OH ions at the anode to form oxygen gas. 23. A system for producing hydrogen gas, comprising: a reaction vessel containing an aqueous solution; a cathode at least partially disposed within the reaction vessel, a portion of the cathode having an outer surface immersed in and in electrical contact with the aqueous solution to form an interface for a reduction reaction to reduce H ions to produce hydrogen gas at the cathode; an anode at least partially disposed within the reaction vessel, a portion of the anode immersed in and in electrical contact with the aqueous solution to form an interface for an oxidation reaction to oxidize OH ions at the anode to produce oxygen gas, the cathode and anode configured to receive power from a power source; at least one first ultrasonic transducer disposed at least partially within the reaction vessel, each first ultrasonic transducer positioned a predetermined distance from the cathode and oriented such that each first ultrasonic transducer emits and conducts ultrasonic waves at least partially through the aqueous solution toward an outer surface of the cathode to agitate the aqueous solution proximate the outer surface of the cathode and remove hydrogen gas bubbles formed on the outer surface of the cathode to expose the outer surface of the cathode to additional H ions to generate hydrogen gas; and at least one second ultrasonic transducer disposed at least partially within the reaction vessel, each second ultrasonic transducer positioned a predetermined distance from the anode and oriented such that each second ultrasonic transducer emits ultrasonic waves at least partially toward an outer surface of the anode to induce cavitation in an aqueous solution proximate to the outer surface of the anode, the cavitation weakening hydrogen bonds between water molecules in the aqueous solution to separate individual water molecules available for interaction with the anode and undergoing an oxidation reaction at the anode to oxidize OH ions at the anode to form oxygen gas.

Claims

1. 1. A system for producing hydrogen gas, the system comprising: a reaction vessel containing an aqueous solution; a cathode at least partially disposed within the reaction vessel, a portion of the cathode having an outer surface immersed in and in electrical contact with the aqueous solution to form an interface for a reduction reaction to reduce H+ ions to produce hydrogen gas at the cathode; an anode at least partially disposed within the reaction vessel, a portion of the anode immersed in and in electrical contact with the aqueous solution to form an interface for an oxidation reaction at the anode to oxidize OH ions to produce oxygen gas, the cathode and the anode configured to receive power from a power source; a polymer electrolyte membrane (PEM) disposed between the cathode and the anode, the PEM separating the H+ ions and the OH− ions in the aqueous solution to form partition regions within the reactor, the aqueous solution in the partition region adjacent the cathode having a higher concentration of H+ ions than OH− ions; a first ultrasonic transducer at least partially disposed within the reaction vessel, the first ultrasonic transducer positioned a predetermined distance from the cathode, the first ultrasonic transducer oriented to emit ultrasonic waves at least partially toward the outer surface of the cathode to agitate the aqueous solution proximate the outer surface of the cathode and remove the hydrogen gas bubbles formed on the outer surface of the cathode to expose the outer surface of the cathode to additional H ions to generate hydrogen gas; a second ultrasonic transducer disposed at least partially within the reactor, the second ultrasonic transducer being positioned a predetermined distance from the anode and oriented to emit ultrasonic waves at least partially toward the outer surface of the anode to induce cavitation in the aqueous solution proximate the outer surface of the anode, the cavitation weakening hydrogen bonds between water molecules in the aqueous solution to separate individual water molecules available for interaction with the anode, and undergoing the oxidation reaction at the anode to oxidize the OH− ions at the anode to form oxygen gas; a plurality of transducer drivers each electrically coupled to a respective one of the first ultrasonic transducer or the second ultrasonic transducer to drive the ultrasonic transducer to generate the ultrasonic waves, wherein the transducer drivers an H-bridge circuit connected to the ultrasonic transducer, the H-bridge circuit generating an AC drive signal to drive the ultrasonic transducer to generate and transmit the ultrasonic waves; a microchip connected to the H-bridge circuit and controlling the H-bridge circuit to generate the AC drive signal, the microchip comprising:

1. An oscillator, comprising: A main clock signal; a first phase clock signal that is initially high during a positive half-period of the main clock signal and low during a negative half-period of the main clock signal; an oscillator configured to generate a second phase clock signal that is high a second time during a negative half-period of the main clock signal and low during a positive half-period of the main clock signal, wherein the phases of the first phase clock signal and the second phase clock signal are center-aligned; a pulse width modulation (PWM) signal generator subsystem, comprising: a delay locked loop that uses the first phase clock signal and the second phase clock signal to generate a double frequency clock signal that is twice the frequency of the main clock signal, the delay locked loop synchronizing the first phase clock signal and the second phase clock signal, the delay locked loop adjusting the frequency and the duty cycle of the first phase clock signal and the second phase clock signal in response to a driver control signal to generate a first phase output signal and a second phase output signal, the first phase output signal and the second phase output signal being configured to drive the H-bridge circuit to generate the AC drive signal for driving the ultrasonic transducer; a first phase output signal terminal for outputting the first phase output signal to the H-bridge circuit; a second phase output signal terminal for outputting the second phase output signal to the H-bridge circuit; a feedback input terminal for receiving a feedback signal from the H-bridge circuit, the feedback signal being indicative of the operation of the H-bridge circuit or a parameter of the AC drive signal when the H-bridge circuit is driving the ultrasonic transducer with the AC drive signal; and an analog-to-digital converter (ADC) subsystem, comprising: at least one ADC input terminal for receiving an analog signal, the ADC input terminal being connected to the feedback input terminal such that the ADC subsystem receives the feedback signal from the H-bridge circuit, the ADC subsystem sampling the analog signal received at the ADC input terminal at a sampling frequency proportional to the frequency of the main clock signal, and the ADC subsystem generating an ADC digital signal using the sampled analog signal; an ADC subsystem comprising: a digital processor subsystem that receives the ADC digital signal from the ADC subsystem, processes the ADC digital signal to generate the driver control signal, and communicates the driver control signal to the PWM signal generator subsystem to control the PWM signal generator subsystem; 1. A digital-to-analog converter (DAC) subsystem comprising: a digital-to-analog converter (DAC) that converts the digital control signals generated by the digital processor subsystem into analog voltage control signals to control a voltage regulator circuit that generates voltages for modulation by the H-bridge circuit; a DAC output terminal that outputs the analog voltage control signal to control the voltage regulator circuit to generate a predetermined voltage for modulation by the H-bridge circuit to drive the ultrasonic transducer to control the cavitation in the aqueous solution in response to a feedback signal indicative of the operation of the ultrasonic transducer.

2. 1. A system for producing hydrogen gas, the system comprising: a reaction vessel containing an aqueous solution; a cathode at least partially disposed within the reaction vessel, a portion of the cathode having an outer surface immersed in and in electrical contact with the aqueous solution to form an interface for a reduction reaction to reduce H+ ions to produce hydrogen gas at the cathode; an anode at least partially disposed within the reaction vessel, a portion of the anode immersed in and in electrical contact with the aqueous solution to form an interface for an oxidation reaction at the anode to oxidize OH ions to produce oxygen gas, the cathode and the anode configured to receive power from a power source; a plurality of first ultrasonic transducers disposed at least partially within the reaction vessel, each first ultrasonic transducer positioned a predetermined distance from the cathode and oriented such that each first ultrasonic transducer emits and conducts ultrasonic waves at least partially through the aqueous solution toward the outer surface of the cathode to agitate the aqueous solution proximate the outer surface of the cathode and remove bubbles of hydrogen gas formed on the outer surface of the cathode to expose the outer surface of the cathode to additional H ions to generate hydrogen gas; a plurality of second ultrasonic transducers disposed at least partially within the reaction vessel, the second ultrasonic transducers being positioned a predetermined distance from the anode and oriented to emit ultrasonic waves at least partially toward the outer surface of the anode to cause cavitation in the aqueous solution proximate the outer surface of the anode, the cavitation weakening hydrogen bonds between water molecules in the aqueous solution to separate individual water molecules available for interaction with the anode, and undergoing the oxidation reaction at the anode to oxidize OH- ions at the anode to form oxygen gas; a plurality of transducer drivers each electrically coupled to a respective one of the ultrasonic transducers to drive the ultrasonic transducers to generate the ultrasonic waves, each transducer driver comprising: an H-bridge circuit connected to each one of the ultrasonic transducers, the H-bridge circuit generating an AC drive signal for driving the ultrasonic transducer to generate and transmit the ultrasonic waves; a microchip connected to the H-bridge circuit and controlling the H-bridge circuit to generate the AC drive signal, the microchip comprising:

1. An oscillator, comprising: A main clock signal; a first phase clock signal that is initially high during a positive half-period of the main clock signal and low during a negative half-period of the main clock signal; a second phase clock signal that is high a second time during a negative half-period of the main clock signal and low during a positive half-period of the main clock signal, wherein the phases of the first phase clock signal and the second phase clock signal are center-aligned; and a pulse width modulation (PWM) signal generator subsystem, comprising: a delay locked loop that uses the first phase clock signal and the second phase clock signal to generate a double frequency clock signal that is twice the frequency of the main clock signal, the delay locked loop synchronizing the first phase clock signal and the second phase clock signal, the delay locked loop adjusting the frequency and the duty cycle of the first phase clock signal and the second phase clock signal in response to a driver control signal to generate a first phase output signal and a second phase output signal, the first phase output signal and the second phase output signal being configured to drive the H-bridge circuit to generate the AC drive signal for driving the ultrasonic transducer; a first phase output signal terminal for outputting the first phase output signal to the H-bridge circuit; a second phase output signal terminal for outputting the second phase output signal to the H-bridge circuit; a feedback input terminal for receiving a feedback signal from the H-bridge circuit, the feedback signal being indicative of the operation of the H-bridge circuit or a parameter of the AC drive signal when the H-bridge circuit is driving a respective one of the ultrasonic transducers with the AC drive signal; an analog-to-digital converter (ADC) subsystem, comprising: at least one ADC input terminal for receiving an analog signal, the ADC input terminal being connected to the feedback input terminal such that the ADC subsystem receives the feedback signal from the H-bridge circuit, the ADC subsystem sampling the analog signal received at the ADC input terminal at a sampling frequency proportional to the frequency of the main clock signal, and the ADC subsystem generating an ADC digital signal using the sampled analog signal; an ADC subsystem comprising: a digital processor subsystem that receives the ADC digital signal from the ADC subsystem, processes the ADC digital signal to generate the driver control signal, and communicates the driver control signal to the PWM signal generator subsystem to control the PWM signal generator subsystem; 1. A digital-to-analog converter (DAC) subsystem comprising: a digital-to-analog converter (DAC) that converts the digital control signals generated by the digital processor subsystem into analog voltage control signals to control a voltage regulator circuit that generates voltages for modulation by the H-bridge circuit; a DAC output terminal that outputs the analog voltage control signal to control the voltage regulator circuit to generate a predetermined voltage for modulation by the H-bridge circuit to drive the respective one of the ultrasonic transducers to control the cavitation in the aqueous solution in response to the feedback signal indicative of operation of the respective one of the ultrasonic transducers.

3. The system comprises:

3. The system of claim 2, further comprising: a polymer electrolyte membrane (PEM) disposed within the reactor between the cathode and the anode, the PEM separating the H+ ions and the OH− ions in the aqueous solution to form a partition region within the reactor, the aqueous solution in the partition region proximate the cathode having a higher concentration of H+ ions than OH− ions.

4. The system of any one of claims 1 to 3, wherein the transducer driver drives the ultrasonic transducer at a frequency between 20 kHz and 40 kHz.

5. The system according to any one of claims 1 to 4, wherein each first ultrasonic transducer is positioned at a distance from the outer surface of the cathode equal to one wavelength of the ultrasonic waves emitted by the ultrasonic transducer.

6. The system of any one of claims 1 to 4, wherein each first ultrasonic transducer is positioned at a distance from the outer surface of the cathode equal to a plurality of wavelengths of the ultrasonic waves emitted by the ultrasonic transducer.

7. 7. The system of claim 1, wherein each second ultrasonic transducer is positioned at a distance from the outer surface of the anode equal to one wavelength of the ultrasonic waves emitted by the ultrasonic transducer.

8. 8. The system of claim 1, wherein each second ultrasonic transducer is positioned at a distance from the outer surface of the anode equal to a multiple of the wavelengths of the ultrasonic waves emitted by the ultrasonic transducer.

9. The system of any preceding claim, wherein each first ultrasonic transducer is oriented to emit ultrasonic waves in a direction transverse to the longitudinal length of the cathode.

10. The system of any preceding claim, wherein each second ultrasonic transducer is oriented to emit ultrasonic waves in a direction transverse to the longitudinal length of the anode.

11. The system comprises:

11. The system of claim 1, comprising a main controller that controls the power applied between the anode and the cathode, the main controller coupled to each transducer driver to control the operation of each transducer driver to optimize efficiency of hydrogen gas generation.

12. The system comprises: a hydrogen gas collector disposed at least partially within the reaction vessel for collecting hydrogen gas produced within the reaction vessel; 12. The system of claim 11, comprising: a hydrogen gas pressure sensor that senses the pressure of hydrogen gas in the hydrogen gas collector, the hydrogen gas pressure sensor being electrically coupled to the main controller to provide a hydrogen gas pressure signal to the main controller in a feedback loop.

13. The system comprises: an oxygen gas collector disposed at least partially within the reaction vessel to collect oxygen gas produced within the reaction vessel; 13. The system of claim 11 or 12, further comprising: an oxygen gas pressure sensor that senses the pressure of oxygen gas in the oxygen gas collector, the oxygen gas pressure sensor being electrically coupled to the main controller to provide an oxygen gas pressure signal to the main controller in a feedback loop.

14. The transducer driver includes:

14. The system of claim 1, further comprising a frequency divider connected to the oscillator to receive the main clock signal from the oscillator, the frequency divider dividing the main clock signal by a predetermined divisor amount and outputting the frequency reference signal to the delay locked loop.

15. 15. The system of claim 14, wherein the delay locked loop comprises a plurality of delay lines connected end to end, the total delay of the delay lines being equal to the period of the main clock signal.

16. 16. The system of claim 15, wherein the delay locked loop adjusts the duty cycle of the first phase clock signal and the second phase clock signal in response to the driver control signal by varying the delay of each delay line within the delay locked loop.

17. 17. The system of claim 1, wherein the feedback input terminal receives a feedback signal from the H-bridge circuit in the form of a voltage indicative of the rms current of the AC drive signal driving the ultrasonic transducer.

18. 18. The system of any one of claims 1 to 17, wherein the ADC subsystem comprises at least one further ADC input terminal for receiving a feedback signal indicative of at least one of the voltage of a battery connected to the system or the voltage of a battery charger connected to the system.

19. 1. A system for producing hydrogen gas, the system comprising: a housing including a first interior chamber and a second interior chamber; an anode at least partially disposed within the first internal chamber, a portion of the anode in electrical contact with water in the first internal chamber to form an interface for an oxidation reaction that oxidizes OH ions to produce oxygen gas at the anode, the anode being porous; a cathode at least partially disposed within the second internal chamber, the cathode being porous, and the cathode and the anode being configured to receive power from a power source; and a polymer electrolyte membrane (PEM) disposed between the cathode and the anode, the PEM allowing H+ ions to migrate from the anode to the cathode and the PEM preventing OH− ions from migrating from the anode to the cathode; an ultrasonic transducer disposed at least partially within the first internal chamber, the ultrasonic transducer positioned a predetermined distance from the anode and oriented to emit ultrasonic waves at least partially toward a surface of the anode to create cavitation in the water adjacent the exterior surface of the anode, the cavitation weakening hydrogen bonds between water molecules to separate individual water molecules available for interaction with the anode and undergoing the oxidation reaction at the anode to oxidize OH- ions at the anode to form oxygen gas; a transducer driver electrically coupled to the ultrasonic transducer and configured to drive the ultrasonic transducer to generate the ultrasonic waves; a hydrogen gas outlet that allows hydrogen gas to be produced within the second internal chamber when the H+ ions are reduced at the cathode to produce the hydrogen gas.

20. The system comprises: a transducer driver coupled to the ultrasonic transducer, the transducer driver comprising: an H-bridge circuit connected to the ultrasonic transducer, the H-bridge circuit generating an AC drive signal to drive the ultrasonic transducer to generate and transmit the ultrasonic waves; a microchip connected to the H-bridge circuit and controlling the H-bridge circuit to generate the AC drive signal, the microchip comprising:

1. An oscillator, comprising: A main clock signal; a first phase clock signal that is initially high during a positive half-period of the main clock signal and low during a negative half-period of the main clock signal; a second phase clock signal that is high a second time during a negative half-period of the main clock signal and low during a positive half-period of the main clock signal, wherein the phases of the first phase clock signal and the second phase clock signal are center-aligned; and a pulse width modulation (PWM) signal generator subsystem, comprising: a delay locked loop that uses the first phase clock signal and the second phase clock signal to generate a double frequency clock signal that is twice the frequency of the main clock signal, the delay locked loop synchronizing the first phase clock signal and the second phase clock signal, the delay locked loop adjusting the frequency and the duty cycle of the first phase clock signal and the second phase clock signal in response to a driver control signal to generate a first phase output signal and a second phase output signal, the first phase output signal and the second phase output signal being configured to drive the H-bridge circuit to generate the AC drive signal for driving the ultrasonic transducer; a first phase output signal terminal for outputting the first phase output signal to the H-bridge circuit; a second phase output signal terminal for outputting the second phase output signal to the H-bridge circuit; a feedback input terminal for receiving a feedback signal from the H-bridge circuit, the feedback signal being indicative of the operation of the H-bridge circuit or a parameter of the AC drive signal when the H-bridge circuit is driving the ultrasonic transducer with the AC drive signal; and an analog-to-digital converter (ADC) subsystem, comprising: at least one ADC input terminal for receiving an analog signal, the ADC input terminal being connected to the feedback input terminal such that the ADC subsystem receives the feedback signal from the H-bridge circuit, the ADC subsystem sampling the analog signal received at the ADC input terminal at a sampling frequency proportional to the frequency of the main clock signal, and the ADC subsystem generating an ADC digital signal using the sampled analog signal; an ADC subsystem comprising: a digital processor subsystem that receives the ADC digital signal from the ADC subsystem, processes the ADC digital signal to generate the driver control signal, and communicates the driver control signal to the PWM signal generator subsystem to control the PWM signal generator subsystem; 1. A digital-to-analog converter (DAC) subsystem comprising: a digital-to-analog converter (DAC) that converts the digital control signals generated by the digital processor subsystem into analog voltage control signals to control a voltage regulator circuit that generates voltages for modulation by the H-bridge circuit; 20. The system of claim 19, further comprising a DAC subsystem comprising: a DAC output terminal that outputs the analog voltage control signal to control the voltage regulator circuit to generate a predetermined voltage for modulation by the H-bridge circuit to drive the ultrasonic transducer to control the cavitation in the aqueous solution in response to a feedback signal indicative of the operation of the ultrasonic transducer.

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