High-frequency electric field wireless energy transfer system based on voltage doubler rectifier

Abstract

The invention relates to the technical field of electric field wireless energy transfer, in particular to a high-frequency electric field wireless energy transfer system based on a voltage-doubler rectifier, which comprises a direct-current power supply, a primary high-frequency inverter, an electric energy transmitting end resonance network, a coupling mechanism, an electric energy receiving end resonance network, the voltage-doubler rectifier, a filter capacitor and a load which are connected in sequence, the voltage doubling rectifier comprises a plurality of D-type resonant rectifiers with capacitance isolation. The voltage doubling rectifier is formed by connecting a plurality of D-type resonant rectifiers with capacitor isolation in series or in parallel, the D-type resonant rectifiers with capacitor isolation are driven by single alternating current voltage in parallel, output series operation is achieved, and the power density of the system is improved. The voltage-doubler rectifier can be realized only by a common SiC diode and a capacitor, so that the design difficulty and cost are greatly reduced. The device has the advantages of high efficiency, fast transient response and high power density, and can provide high-voltage isolation output with low voltage input.

Description

Technical Field

[0001] The present invention relates to the technical field of electric field wireless energy transmission, and in particular to a high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier. Background Art

[0002] Traditional power supply methods typically rely on connecting electrical devices to power sources via wires to transmit electrical energy. However, with the development of society, the increase in the number of electrical devices, and the diversification of electricity demands, this traditional power supply method has gradually exposed some difficult-to-ignore problems, such as aging lines, lack of flexibility, sparking during plugging and unplugging, and limited application in special environments such as underwater mines. This series of issues has led to the search for solutions, and wireless power transfer (WPT) technology has emerged. Electric-field coupled wireless power transfer (EC-WPT) technology is a typical WPT technology. EC-WPT systems use metal plates as coupling mechanisms and high-frequency electric fields as energy carriers. They offer many advantages, including lightweight structure, no eddy current losses in surrounding conductors, and good electromagnetic compatibility. With the development of society and the increase in electrical devices, people's demand for electricity is becoming increasingly diversified. Therefore, research on high-frequency electric-field coupled wireless power transfer technology can meet future electricity needs and support sustainable social development.

[0003] As a part that is directly connected to the load, the safety and harmonic content of the rectifier have a certain impact on whether the load can operate stably. There are many types of topological structures of rectifiers used in wireless power transmission systems. Among them, the representative ones are half-wave rectifiers, bridge rectifiers, Class E rectifiers, Class F rectifiers, and composite rectifiers such as Class D rectifiers and Class EF rectifiers. However, whether it is a bridge rectifier or a half-wave rectifier, they all have the problem of large switching losses. These two types of rectifiers are "hard switches" in actual operation, and the switching losses under high-frequency operating conditions are very high, which seriously affects the energy transfer efficiency of the rectifier. Bridge rectifiers are generally suitable for occasions below 1MHz, and are no longer applicable to higher frequency coupled resonance occasions. The reason why the Class E topology is often used in high-frequency wireless power transmission systems is mainly because the output inductor L r and parallel capacitor C r Generating resonance can achieve ZVS and reduce switching losses. Theoretically, the loss of a Class E rectifier is zero, but in actual circuits, the presence of component parasitic parameters causes some loss, so its parameters need to be optimized to minimize the rectifier's energy loss.

[0004] Electric field wireless charging utilizes capacitive coupling between the transmitter and receiver to transfer energy between them via a high-frequency electric field. The electrodes at the receiver couple to the high-frequency electric field at the transmitter, thereby receiving a low-frequency, low-voltage AC signal. Typically, this signal has a low voltage and cannot directly power the device, so a voltage multiplier circuit is required to convert it to a higher DC voltage. Currently, rectifiers commonly used for high frequencies, such as Class-E, Class-Φ2, and Class-D rectifiers, cannot output voltages higher than the rated value of the diodes within the rectifier, resulting in a low output voltage. However, traditional series-type high-voltage converter topologies (such as the Crockroft-Walton multiplier), while simple in structure and offering high voltage gain, suffer from severe efficiency losses at high frequencies. Summary of the Invention

[0005] To address the existing problem of how to provide high-voltage isolated output with a lower voltage input in the output rectifier part of the system, the present invention provides a high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier. The specific technical solution is as follows:

[0006] A high-frequency electric field wireless energy transmission system based on a voltage-doubling rectifier comprises a DC power supply, a primary high-frequency inverter, a power transmitting end resonant network, a coupling mechanism, a power receiving end resonant network, a voltage-doubling rectifier, a filter capacitor, and a load connected in sequence;

[0007] The voltage doubler rectifier includes a plurality of class D resonant rectifiers with capacitor isolation.

[0008] Preferably, several class-D resonant rectifiers with capacitor isolation are driven in parallel by a single AC voltage, and their outputs operate independently, in parallel, or in series.

[0009] Preferably, the class D resonant rectifier with capacitor isolation includes a first capacitor, a second capacitor, a first diode, and a second diode;

[0010] One end of the first capacitor and one end of the second capacitor are respectively connected to two output ends of the power receiving end resonant network;

[0011] The other end of the first capacitor is connected to the negative end of the first diode and the positive end of the second diode, the positive end of the first diode is connected to the other end of the second capacitor, and the negative end of the second diode is connected to one end of the filter capacitor or the positive end of the first diode of the previous class D resonant rectifier with capacitor isolation;

[0012] The positive terminal of the first diode is connected to the negative terminal of the second diode of the next class D resonant rectifier with capacitor isolation or the other end of the filter capacitor.

[0013] Preferably, when the outputs of several class D resonant rectifiers with capacitor isolation are connected in series, the output voltage of the voltage doubler rectifier is:

[0014] V=nV ac-amp ;

[0015] Among them, V ac-amp V ac Peak voltage, V ac represents the input voltage of the voltage doubler rectifier, and n represents the number of class D resonant rectifiers with capacitor isolation connected in series.

[0016] Preferably, the primary high-frequency inverter is a full-bridge inverter, including MOS transistors S1 to S4.

[0017] Preferably, the power transmitting end resonant network adopts an LC compensation network, including an inductor L1 and a capacitor C ex1 .

[0018] Preferably, the coupling mechanism comprises two sets of emitter plates and two sets of receiver plates;

[0019] The two groups of emitter plates are respectively connected to the two output ends of the power transmitting end resonant network, the two groups of receiving plates are respectively connected to the two input ends of the power receiving end resonant network, and the two groups of emitter plates are respectively arranged opposite to the two groups of receiving plates.

[0020] Preferably, the power receiving end resonant network adopts an LC compensation network, including an inductor L2 and a capacitor C ex2 .

[0021] Preferably, the filter capacitor is of μF level.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The wireless energy transmission system of the present invention includes a DC power supply, a primary high-frequency inverter, a power transmitting end resonant network, a coupling mechanism, a power receiving end resonant network, a voltage doubler rectifier, a filter capacitor and a load connected in sequence; the voltage doubler rectifier includes a plurality of class D resonant rectifiers with capacitor isolation. The present invention uses a multi-stage stacking method to design an isolated resonant voltage doubler rectifier, which is composed of a plurality of class D resonant rectifiers with capacitor isolation connected in series or in parallel. The plurality of class D resonant rectifiers with capacitor isolation are driven in parallel by a single AC voltage, and the outputs are operated in series, thereby improving the power density of the system. The voltage doubler rectifier only requires ordinary SiC diodes and capacitors to be implemented, which greatly reduces the design difficulty and cost. The present invention has the advantages of high efficiency, fast transient response and high power density, and can provide high-voltage isolated output with a lower voltage input. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0025] Figure 1 This is an overall framework diagram of a typical EC-WPT system provided by an embodiment of the present invention;

[0026] Figure 2 is a circuit diagram of a Cockcroft-Walton (CW) voltage multiplier provided by an embodiment of the present invention;

[0027] Figure 3 1 is a circuit diagram of a class-D resonant rectifier with capacitor isolation provided by an embodiment of the present invention;

[0028] Figure 4 This is a circuit diagram of a high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier provided in an embodiment of the present invention;

[0029] Figure 5 1 is a waveform diagram of input voltage and output voltage of a voltage doubler rectifier provided in an embodiment of the present invention;

[0030] Figure 6 1 is a diagram of voltage and current output by a load provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0033] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0034] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0035] like Figure 1 As shown, this embodiment provides a high-frequency electric field wireless energy transmission system based on a voltage-doubling rectifier, comprising a DC power supply, a primary high-frequency inverter, a power transmitter resonant network, a coupling mechanism, a power receiver resonant network, a voltage-doubling rectifier, a filter capacitor, and a load, all connected in sequence. The voltage-doubling rectifier includes several Class-D resonant rectifiers with capacitive isolation. Each of the Class-D resonant rectifiers with capacitive isolation is driven in parallel by a single AC voltage, and their outputs operate independently, in parallel, or in series.

[0036] Figure 1 This is a typical EC-WPT system structure, consisting of a grid power supply, a primary high-frequency inverter, a resonant network at the power transmitter, a coupling mechanism, a resonant network at the power receiver, a secondary rectifier, and a load. The coupling mechanism consists of an emitter plate and a receiver plate, forming a coupling electric field between them for power transmission. The EC-WPT system can be powered by AC mains power after rectification and filtering, or directly from a DC power source. The high-frequency inverter converts DC power into high-frequency AC power for the resonant network, while the resonant network at the power transmitter provides high-frequency, high-voltage excitation for the coupling mechanism. This high-frequency, high-voltage AC excitation generates a "displacement current" in the coupling mechanism, transferring power from the system's transmitter to the receiver. The resonant network at the receiver converts the received power into the required output voltage / current. The rectifier filter converts the AC power into DC power for the load.

[0037] In electric field wireless power transmission, in order to achieve voltage regulation and high-efficiency operation of the system while avoiding the addition of additional DC-DC conversion circuits, the present invention designs a voltage doubler rectifier for the output rectification part of the high-frequency electric field wireless power transmission system.

[0038] Electric field wireless charging utilizes capacitive coupling between the transmitter and receiver, transferring energy between them via a high-frequency electric field. The electrodes at the receiver couple to the transmitter's high-frequency electric field, receiving a low-frequency, low-voltage AC signal. Typically, this signal has a low voltage and cannot directly power a device, so a voltage multiplier circuit is required to convert it to a higher DC voltage.

[0039] The Cockcroft-Walton (CW) voltage multiplier is a commonly used voltage multiplier, such as Figure 2As shown, it uses multiple rectifiers in series because it can be used effectively because it has low voltage stress on diodes and capacitors while boosting high voltage, high cost-effectiveness, and high power density. Its output voltage is:

[0040] V=nV ac-amp ;

[0041] Among them, V ac-amp V ac Peak voltage, V ac represents the input voltage of the voltage multiplier, and n represents the number of rectifiers in series.

[0042] The rectifier stage converts the AC output of the previous stage into a DC output for the load. For AC-DC power converters operating in the MHz range, to ensure efficient and reliable operation, the rectifier diodes must operate in a soft-switching state. Parasitic parameters in the rectifier stage must be absorbed and utilized by the resonant parameters, ensuring that the equivalent impedance of the rectifier stage is purely resistive or slightly inductive. Traditional diode rectifier circuits exhibit reverse recovery losses, which are particularly pronounced at high frequencies. Therefore, the rectifier stage of high-frequency power converters often utilizes a resonant circuit, leveraging the resonance of capacitors and inductors to achieve zero-current switching (ZCS) of the diodes and address the reverse recovery loss issue. Furthermore, the capacitors absorb the diode junction capacitance, minimizing the impact of parasitic parameters on the resonant operation of the rectifier stage. Currently, Class-E, Class-Φ2, and Class-D rectifiers are widely used in MHz-range applications due to their simple topology, ability to achieve zero-current switching (ZCS), and ability to absorb and utilize diode junction capacitance.

[0043] Class-Φ2 and Class-D rectifiers reduce the voltage stress across the diodes, allowing for higher output voltages than other resonant topologies, such as Class E. An advantage of Class-D rectifiers is that, for a given output power and voltage, the rectifier's equivalent resistance is lower than that of both Class-E and Class-Φ2, thus reducing network sensitivity. Class-D rectifiers reduce device voltage stress and simplify impedance matching, resulting in greater voltage gain and higher output voltages.

[0044] However, the above design still has a basic limitation, that is, the output voltage cannot be higher than the rated value of the diode in the rectifier stage. Therefore, the isolated output is achieved by using capacitive isolation in the rectifier stage of the AC-DC converter. Isolation can be achieved by splitting the DC blocking capacitor into two series capacitors C R and C B , and place one of them in the return path to implement it, such as Figure 3 As shown, an isolation capacitor C is added in the return path BIn addition to isolating the output, the benefits of this approach include: 1) reducing or eliminating the quality factor of the resonant network and associated losses, 2) achieving higher voltage gain, 3) a voltage output greater than the diode rating, and 4) having higher power density. Therefore, the class D resonant rectifier with capacitor isolation is an AC-DC converter with high efficiency, high power density, and fast transient response. Diode D R and D B The parallel connection of capacitors is used to improve the purity of the signal and prevent unwanted signals from passing through the junction capacitance of the diode and causing malfunction of the circuit. in and V o Represent the input AC voltage and output DC voltage respectively.

[0045] In this embodiment, the coupling mechanism includes two groups of emitter plates and two groups of receiving plates; the two groups of emitter plates are respectively connected to the two output ends of the resonant network at the power transmitting end, and the two groups of receiving plates are respectively connected to the two input ends of the resonant network at the power receiving end, and the two groups of emitter plates are respectively arranged opposite to the two groups of receiving plates.

[0046] Therefore, the topology network of the system of the present invention is as follows Figure 4 As shown, it specifically includes a DC power supply E dc , the primary high-frequency inverter (a full-bridge inverter composed of MOS tubes S1 to S4), the power transmitter resonant network (using an LC compensation network, including inductor L1 and capacitor C ex1 ), coupling mechanism (including emitter plate P T1 、P T2 , receiving plate P R1 、P R2 ), the power receiving end resonant network (using LC compensation network, including inductor L2 and capacitor C ex2 ), voltage doubler rectifier, filter capacitor C f and load R L .

[0047] To reduce losses and increase the electric field alternating frequency, the primary inverter adopts a full-bridge structure. This structure features a simple control strategy and high power density. Combined with soft-switching technology, it effectively reduces switching losses in the inverter network and increases the electric field alternating frequency. Furthermore, both the primary and secondary sides utilize a relatively easy-to-implement and stable double-sided LC second-order resonant network, which minimizes the weight burden on the receiver while providing excellent filtering. The voltage-doubling rectifier utilizes a stack of multiple Class-D resonant rectifiers with capacitor isolation. Each Class-D resonant rectifier is driven in parallel by a single AC voltage, and its outputs can operate independently, in parallel, or in series. This design utilizes a series output for higher voltage gain and employs Class-D resonant rectifiers with capacitor isolation to improve overall efficiency. A filter capacitor is then connected in parallel across the load to enhance system output stability.

[0048] Each stage of the class D resonant rectifier with capacitor isolation includes a first capacitor, a second capacitor, a first diode, and a second diode; one end of the first capacitor and one end of the second capacitor are respectively connected to the two output ends of the resonant network at the power receiving end; the other end of the first capacitor is connected to the negative end of the first diode and the positive end of the second diode, the positive end of the first diode is connected to the other end of the second capacitor, and the negative end of the second diode is connected to the filter capacitor C f One end of the D-type resonant rectifier or the positive end of the first diode of the previous D-type resonant rectifier with capacitor isolation; the positive end of the first diode is connected to the negative end of the second diode of the next D-type resonant rectifier with capacitor isolation or the filter capacitor C f The other end of the filter capacitor C f It is μF level.

[0049] Figure 4 Three class D resonant rectifiers are superimposed, with the inputs connected in parallel and the outputs connected in series to obtain a higher voltage gain. The number and connection method of the class D resonant rectifiers set here are only examples and can be adjusted according to specific voltage requirements.

[0050] Since electric field coupling has the advantages of simple structure, small size, light weight and low cost, electric field coupling wireless charging technology has shown broad application prospects in the field of drone charging. In small systems, it is challenging to achieve a large voltage gain because the auxiliary power supply is usually larger than the system itself, resulting in an increase in the system volume and weight. Taking into account the lightweight design of the drone, the system topology network of the present invention is compactly designed, and both the primary and secondary sides use a bilateral LC type second-order resonant network, which does not impose a large weight burden on the receiving end and can also produce a relatively excellent filtering effect. The rectifier adopts a multi-stage stacking method, and multiple rectifiers are driven in parallel by a single AC voltage, and the outputs are operated in series, which improves the power density of the system.

[0051] High-frequency rectifier circuits typically require high-performance electronic devices such as bidirectional conductive transistors, triodes, and reverse nanosecond diodes, making them more expensive than conventional rectifier circuits. However, this design requires only common SiC diodes and capacitors, significantly reducing design difficulty and cost.

[0052] This invention uses wireless power transmission, avoiding issues such as line aging and sparking at the plug-in / plug-out points that plague traditional power supply methods, reducing environmental pollution and potential safety hazards. Furthermore, due to the system's high efficiency and low energy consumption, it also reduces energy consumption and carbon emissions, significantly impacting environmental protection.

[0053] Simulation analysis:

[0054] The present invention adopts a double-sided LC resonant topology, and the coupling capacitance C corresponding to the coupling mechanism is determined based on experience. in1 (equivalent capacitance of the LC resonant circuit connected to the transmitter), C in2 (equivalent capacitance connected to the LC resonant circuit at the receiving end), C M (Connected in C in1 and C in2 The equivalent capacitance between the two, the coupling mechanism is equivalent to C in1 、C M 、C in2 The values ​​of the three-capacitor model (using a T-type connection) can also be calculated. Therefore, the values ​​of L1 and L2 in the LC resonant network can be determined through tuning. The load-side filter capacitor can be set in the μF range. The system operating frequency f is 1 MHz, and the system parameters are shown in Table 1.

[0055] Table 1 System parameters

[0056] parameter Numerical parameter Numerical <![CDATA[U in / V]]> 50 <![CDATA[L1 / uH]]> 15.91 f / MHz 1 <![CDATA[L2 / uH]]> 16.04 <![CDATA[C M / pF]]> 83.37 <![CDATA[C ex1 / pF]]> 1500 <![CDATA[C in1 / pF]]> 96.30 <![CDATA[C ex2 / pF]]> 1500 <![CDATA[C in2 / pF]]> 83.87 <![CDATA[R L / Oh]]> 20

[0057] The equivalent circuit of the electric field wireless power transmission system mentioned in the present invention is simulated by Matlab / Simulink, and the input voltage and output voltage waveforms of the high-frequency voltage doubler rectifier are obtained as follows: Figure 5 As shown. Through simulation, the load output voltage and output current waveforms are shown as follows Figure 6 As shown. Figure 5 、 Figure 6 Analysis shows that the system response time is fast and the tracking error is small. The output fluctuates slightly before leveling off. Compared to traditional uncontrolled full-bridge rectification, the series-connected isolated resonant rectifier stage increases system efficiency from 80.51% to 89.34%, while also reducing displacement current and switching stress.

[0058] This demonstrates that the present invention effectively improves system transmission efficiency by designing a novel high-frequency electric field-coupled wireless energy transmission circuit based on a voltage-doubling rectifier. Compared to traditional rectifiers, the voltage-doubling rectifier achieves higher voltage gain. Furthermore, the use of a Class-D resonant rectifier with capacitive isolation further reduces switching losses, boosting system efficiency from the traditional 80.51% to 89.34%.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier, characterized in that: It includes a DC power supply, a primary high-frequency inverter, a power transmitting end resonant network, a coupling mechanism, a power receiving end resonant network, a voltage doubling rectifier, a filter capacitor and a load connected in sequence; The voltage doubler rectifier includes a plurality of class D resonant rectifiers with capacitor isolation.

2. The high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier according to claim 1, characterized in that: Several class D resonant rectifiers with capacitor isolation are driven in parallel by a single AC voltage, and their outputs operate independently, in parallel, or in series.

3. The high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier according to claim 1, characterized in that: The class D resonant rectifier with capacitor isolation includes a first capacitor, a second capacitor, a first diode, and a second diode; One end of the first capacitor and one end of the second capacitor are respectively connected to two output ends of the power receiving end resonant network; The other end of the first capacitor is connected to the negative end of the first diode and the positive end of the second diode, the positive end of the first diode is connected to the other end of the second capacitor, and the negative end of the second diode is connected to one end of the filter capacitor or the positive end of the first diode of the previous class D resonant rectifier with capacitor isolation; The positive terminal of the first diode is connected to the negative terminal of the second diode of the next class D resonant rectifier with capacitor isolation or the other end of the filter capacitor.

4. The high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier according to claim 2, characterized in that: When the outputs of several class D resonant rectifiers with capacitor isolation are connected in series, the output voltage of the voltage doubler rectifier is: V=nV ac-amp ; Among them, V ac-amp V ac Peak voltage, V ac represents the input voltage of the voltage doubler rectifier, and n represents the number of class D resonant rectifiers with capacitor isolation connected in series.

5. The high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier according to claim 1, characterized in that: The primary high-frequency inverter is a full-bridge inverter, including MOS tubes S1 to S4.

6. The high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier according to claim 1, characterized in that: The power transmitter resonant network uses an LC compensation network, including an inductor L1 and a capacitor C ex1 .

7. The high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier according to claim 1, characterized in that: The coupling mechanism includes two sets of emitter plates and two sets of receiver plates; The two groups of emitter plates are respectively connected to the two output ends of the power transmitting end resonant network, the two groups of receiving plates are respectively connected to the two input ends of the power receiving end resonant network, and the two groups of emitter plates are respectively arranged opposite to the two groups of receiving plates.

8. The high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier according to claim 1, characterized in that: The power receiving end resonant network adopts an LC compensation network, including inductor L2 and capacitor C ex2 .

9. The high-frequency electric field wireless energy transmission system based on a voltage doubler rectifier according to claim 1, characterized in that: The filter capacitor is in μF level.

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