Method and device for driving piezoelectric device

Abstract

To provide a device capable of aerosolizing or atomizing liquid, especially liquid whose viscosity is higher than that of water without involving intentional heating of the liquid.SOLUTION: There are presented a method for driving a piezoelectric device, an atomizer for atomizing fluid, and an atomization method for fluid using the piezoelectric device. The atomizer adopts the piezoelectric device and a circuit using switching voltage applied to the piezoelectric device at an operation frequency, detects a detection voltage corresponding to a phase of the piezoelectric device, and changes the operation frequency provided to the piezoelectric device in response to whether the detection voltage is in-phase or of different phase with respect to the switching voltage, the change being one of increasing the operation frequency by a first value and decreasing the operation frequency by a second value.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] Claiming priority This application claims the benefit of U.S. Provisional Application No. 62907428, filed September 27, 2019. This application is a continuation-in-part of U.S. Provisional Application No. 15004920, filed January 23, 2016. This application is also related to U.S. Provisional Application No. 62314380, filed March 28, 2016, U.S. Provisional Application No. 62343086, filed May 30, 2016, U.S. Provisional Application No. 62 / 106,852, filed January 23, 2015, and U.S. Provisional Application No. 62 / 142,464, filed April 2, 2015. All applications listed are incorporated herein by reference in their entirety.

[0002] TECHNICAL FIELD The present disclosure relates to piezoelectric devices, and in particular to devices for driving piezoelectric devices. [Background technology]

[0003] Atomization is useful for delivering drugs or substances directly to the human respiratory system. Piezoelectric transducers are used to agitate the liquid so that cavitation can occur and droplets or microdroplets of the liquid can be formed. It has been observed that when the liquid is oily or has a higher viscosity than water, conventional piezoelectric transducers may not function as desired. In some cases, the drug liquid is made into a dilute aqueous suspension to allow delivery by a nebulizer operating with a conventional piezoelectric transducer. In some cases, the liquid is intentionally heated to allow its vaporization. As can be appreciated, such an approach may have a detrimental effect on the quality or efficacy of the liquid or drug. Summary of the Invention [Problem to be solved by the invention]

[0004] Thus, a need remains for a device that can aerosolize or atomize liquids, especially liquids that are more viscous than water, preferably without intentional heating of the liquid. [Means for solving the problem]

[0005] In one aspect, the present disclosure provides a method of driving a piezoelectric device, the method including providing a switching voltage across the piezoelectric device at an operating frequency, sensing a sense voltage corresponding to a phase of the piezoelectric device, and varying the operating frequency provided to the piezoelectric device in response to the sense voltage being in phase or out of phase with respect to the switching voltage, the varying being one of increasing the operating frequency by a first value and decreasing the operating frequency by a second value.

[0006] In one embodiment, the method further includes converting the switching voltage into a switching voltage digital signal having at least one transition between two states, and using the at least one transition to trigger sensing of the sense voltage. In another embodiment, the method further includes converting the sense voltage into a sense voltage digital signal, and comparing the switching voltage digital signal to the sense voltage digital signal to determine whether the sense voltage is in phase or out of phase with respect to the switching voltage. The method may further include periodically sensing the sense voltage at a sampling frequency. Furthermore, when the sense voltage digital signal is in a first state, the sense voltage may be in phase with the switching voltage, and when the sense voltage digital signal is in a second state, the sense voltage is out of phase with the switching voltage. Optionally, the sense voltage is across a resistive element operably coupled to the piezoelectric device. Alternatively, the sense voltage is in phase with a current through the piezoelectric device. The method may further include periodically sensing the sense voltage at a sampling frequency. In another embodiment of the method, the operating frequency varies about a variable midpoint at a frequency corresponding to the sampling frequency, the variable midpoint being dependent on a target frequency characterizing the piezoelectric device. The upper bound of the operating frequency may be less than or equal to the target frequency. The lower bound of the operating frequency may be greater than or equal to the target frequency. Optionally, the target frequency is a resonant frequency of the piezoelectric device. In yet another embodiment, the method further includes decreasing the operating frequency of the switching voltage when the sense voltage is in phase with the switching voltage, and increasing the operating frequency of the switching voltage when the sense voltage is out of phase with the switching voltage. Additionally, the method may further include providing the switching voltage at an initial operating frequency upon turning on the piezoelectric device, the initial operating frequency being lower than a target frequency associated with the piezoelectric device.

[0007] In another embodiment, the method further includes increasing an operating frequency of the switching voltage when the sense voltage is in phase with the switching voltage, and decreasing an operating frequency of the switching voltage when the sense voltage is out of phase with the switching voltage. The method can further include providing the switching voltage at an initial operating frequency upon turning on the piezoelectric device, the initial operating frequency being higher than a target frequency associated with the piezoelectric device.

[0008] In an embodiment of the method, the first value is a predetermined value and the second value is a predetermined value. Optionally, the first value is less than or equal to a target frequency band of the piezoelectric device. Alternatively, the second value is less than or equal to a target frequency band of the piezoelectric device. Optionally, the target frequency band is a resonant frequency band.

[0009] In another aspect, a device for driving a piezoelectric device includes an alternator coupled to the piezoelectric device, the alternator configured to provide a switching voltage to drive the piezoelectric device, a controller coupled to the alternator, the controller configured to control an operating frequency of the switching voltage, and a sensing load operably coupled to the piezoelectric device, where the sensing voltage across the sensing load is configured to correspond to a phase of the piezoelectric device, and the controller configured to vary the operating frequency in response to the sensing voltage.

[0010] The device may further comprise a logic device configured to cause the controller to change the operating frequency by a predetermined amount in response to the sense voltage being in phase or out of phase with the switching voltage.

[0011] The device may be configured such that the sense load is a resistive element. The device may be configured such that the sense voltage is in phase with the current through the piezoelectric device. The device may be configured such that the piezoelectric device comprises a transformer coupled to the piezoelectric element, the transformer configured to step up a switching voltage to drive the piezoelectric element. The device may further include an analog-to-digital converter, the analog-to-digital converter coupled to the logic device to convert the switching voltage to a switching voltage digital signal, the switching voltage signal having at least one transition between two states. The device may be configured such that the analog-to-digital converter is configured to convert the sense voltage to a sense voltage digital signal, the sensed digital voltage signal having at least one transition between two states. The device may be configured such that the analog-to-digital converter is an op-amp comparator.

[0012] In one embodiment, the controller is configured to vary the operating frequency at a sampling frequency corresponding to the operating frequency. In one embodiment, the logic device is a digital flip-flop configured to receive as inputs the switching voltage and the sensed voltage. In one embodiment, the sensed voltage is sensed at a transition of the switching voltage. The sensed voltage may be sensed at a positive transition of the switching voltage. The sensed voltage may be sensed at multiple positive transitions of the switching voltage. In another embodiment, the sensed voltage may be sensed at a negative transition of the switching voltage. The sensed voltage may be sensed at multiple negative transitions of the switching voltage. The first value may be equal to the second value. The first value may be below a target frequency band of the piezoelectric device. The second value may be below a target frequency band of the piezoelectric device. The alternator may be a full bridge configured to generate a switching voltage corresponding to a square wave. The alternator may be in a push-pull configuration configured to generate a switching voltage corresponding to a square wave. The alternator may be couplable to a battery.

[0013] According to one aspect, an atomizer for atomizing a fluid includes a piezoelectric device operable with a switching voltage, a sense load operably coupled to the piezoelectric device such that a sense voltage across the sense load corresponds to a phase of the piezoelectric device, and a controller coupled to the piezoelectric device and the sense load, the controller configured to sense the sense voltage and vary an operating frequency in response to the sense voltage. According to another aspect, an atomizer for atomizing a fluid, the atomizer configured to provide a switching voltage across the piezoelectric device at an operating frequency, sense a sense voltage corresponding to a phase of the piezoelectric device, and vary an operating frequency of the switching voltage in response to the sense voltage. According to any of these aspects, the atomizer may be configured to provide a non-intermittent flow of atomized fluid over an operating period, the operating frequency varying by a predetermined amount over the operating period. The atomizer may be configured to vary the operating frequency over a time interval. The atomizer may be configured to sense the sense voltage at a sensing frequency corresponding to the time interval. The atomizer may be configured such that the change in the operating frequency is below a target frequency band. The operating frequency may be intermittent within a target frequency band of the piezoelectric device.

[0014] According to one aspect, a device for atomizing a fluid using a piezoelectric device is configured to provide a switching voltage to the piezoelectric device and vary an operating frequency of the switching voltage by an amount that results in an operating frequency within a target frequency band of the piezoelectric device and an operating frequency of the switching voltage by an amount that moves the operating frequency out of the target frequency band. The amount of change in the operating frequency may be less than or equal to the range of the target frequency band. The device may be configured such that when the operating frequency is within the target frequency band of the piezoelectric device, the operating frequency corresponds to the piezoelectric device being resonant. The device may be further configured to repeatedly alternately vary the operating frequency of the switching voltage into the target frequency band and vary the operating frequency out of the target frequency band.

[0015] In the above atomizer, the fluid has a viscosity of at least 5 centipoise.

[0016] These and other features and advantages of the invention will be described hereinafter with reference to exemplary embodiments as illustrated in the accompanying drawings. [Brief description of the drawings]

[0017] [Figure 1] 1 is an amplitude-frequency plot illustrating the relationship between the amplitude of vibration of a piezoelectric element and its operating frequency. [Diagram 2] FIG. 1 is a schematic diagram illustrating an apparatus according to one embodiment of the present disclosure. [Figure 3A] 1 is an amplitude-time plot showing the switching voltage preceding the current driving a piezoelectric device. [Figure 3B] 1 is an amplitude versus time plot showing switching voltage lagging behind the current driving a piezoelectric device. [Figure 3C] 1 is an amplitude-time plot showing the switching voltage in phase with the current driving the piezoelectric device. [Figure 4A] FIG. 2 is a schematic diagram illustrating an atomizer according to one embodiment. [Figure 4B] FIG. 2 is a schematic diagram illustrating a device for driving a piezoelectric device according to one embodiment. [Diagram 5] FIG. 4 is a schematic diagram illustrating a device for driving a piezoelectric device according to another embodiment. [Figure 6A] FIG. 6 is a schematic diagram showing current flow through a device according to the embodiment of FIG. 5. [Figure 6B] 6B is a schematic diagram showing current flow in another direction through a device according to the embodiment of FIG. 6A. [Figure 7] FIG. 4 is a schematic diagram illustrating a device for driving a piezoelectric device according to another embodiment. [Figure 8A] FIG. 11 is a schematic diagram illustrating the current flow through a piezoelectric device for driving the device according to another embodiment. [Figure 8B]8B is a schematic diagram showing current flow in another direction through a device according to the embodiment of FIG. 8A. [Figure 9] FIG. 4 is a schematic diagram illustrating a device for driving a piezoelectric device according to another embodiment. [Figure 10] FIG. 10A illustrates an example of a switching voltage according to one embodiment, and FIG. 10B illustrates a digitized example of the switching voltage according to FIG. 10A. [Figure 11] FIG. 11A illustrates an example of a sensed voltage according to one embodiment, and FIG. 11B illustrates a digitized example of the sensed voltage according to FIG. 10A. [Figure 12] 4A to 4C are diagrams illustrating an example of a switching voltage, a detection voltage out of phase with the switching voltage, and a detection voltage in phase with the switching voltage; [Figure 13] FIG. 4 illustrates an example of sampling of a sense voltage at a positive transition of a corresponding switching voltage according to one embodiment. [Figure 14] FIG. 13 illustrates an example of sampling of a sense voltage at a negative transition of a corresponding switching voltage according to another embodiment. [Figure 15] FIG. 13 illustrates an example of sampling of a sense voltage at every third positive transition of a corresponding switching voltage according to yet another embodiment. [Figure 16] FIG. 4 illustrates an example of a sampling interval during sampling of a sense voltage according to one embodiment. [Figure 17] FIG. 1 illustrates an initial operating frequency that is lower than a target frequency for a piezoelectric device according to an embodiment. [Figure 18] 18 is a process flow diagram of a logic table according to the embodiment of FIG. 17. [Figure 19] 18 illustrates the drift of the target frequency of the piezoelectric device and the corresponding operating frequency of the switching voltage according to the embodiment of FIG. 17. [Figure 20] 18 illustrates another drift in the target frequency of the piezoelectric device and the corresponding operating frequency of the switching voltage according to the embodiment of FIG. 17. [Figure 21]18 illustrates an example of adjusting a switching voltage and a corresponding sense voltage according to the embodiment of FIG. 17. [Figure 22] FIG. 1 illustrates an example of adjusting a target frequency band of a switching voltage and a sense voltage according to one embodiment. [Figure 23] FIG. 2 illustrates an embodiment of increasing and decreasing an operating frequency, according to one embodiment. [Figure 24] FIG. 13 illustrates an initial operating frequency that is higher than a target frequency for a piezoelectric device according to one embodiment. [Diagram 25] 25 is a process flow diagram of a logic table according to the embodiment of FIG. 24. [Figure 26] 25 illustrates the drift of the target frequency of the piezoelectric device and the corresponding operating frequency of the switching voltage according to the embodiment of FIG. 24. [Figure 27] FIG. 13 illustrates another embodiment of increasing and decreasing the operating frequency, according to one embodiment. [Figure 28] 25 illustrates an example of adjusting a switching voltage and a corresponding sense voltage according to the embodiment of FIG. 24. [Figure 29A] 1 is a plot of the current drawn by a piezoelectric device for atomizing a fluid according to one embodiment. [Figure 29B] 1 is a plot of the current drawn by a piezoelectric device for atomizing a fluid according to one embodiment. [Diagram 30] 1 is a flowchart of a method for driving a piezoelectric device. [Diagram 31] FIG. 1 shows one embodiment of the atomizer invention, comprising a power supply 50, a circuit board 100, a piezoelectric component 60, and a reservoir 98 for holding a liquid 95 or substance to be atomized or vaporized 96. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Parts List: Device or atomizer 40 Power supply, battery or DC power supply 50 Piezoelectric Device 60 Transformer 62 Piezoelectric element 64 Center Tap Transformer 66 Target frequency or plot 70 Target frequency band 70a Upper limit 70b and Lower limit 70c Operating frequency 72 Increased operating frequency 72a Decreasing the operating frequency 72b Ideal target frequency 74 Alternating current (AC) switching voltage or switching voltage 80 Current 80a, 80b Switching Voltage Digital Signal 85 High Voltage 87 Low Voltage 89 Detection voltage 90, 94 Detected voltage digital signal 95 Low Voltage Condition 99 Driving Device 100 Alternator 110 Controller 120 Detection load 130 Logical Device 140 Driving Device 200 Full Bridge 210 (H-Bridge) Switch 212 / 214 / 216 / 218 Controller 220 Detection load 230 Logical Device 240 Analog-to-Digital Converter (ADC) 262 / 264 Driving Device 300 Opamp Comparator 362 / 364 Driving Device 400 Half Bridge 410 Switch 412 / 414 Controller 420 Detection load 430 Driving Device 500 Full Bridge 510 Microcontroller Unit (MCU) 520 Detection load 530 Method 700 for driving a piezoelectric device Operating frequency(710) Phase of Piezoelectric Devices (720) Varying the operating frequency provided to the piezoelectric device (730) Switching Voltage Digital Signals(740) Detected voltage digital signal (750) Detected voltage digital signal (760) Sampling frequency(770) Voltage 810a / 810b / 810c Current 820a / 820b / 820c Current in a piezoelectric device driven by another device 840 Periodic drop 840a and Return 840b Transition 850 Positive (rising) transition 850a of the switching voltage digital signal 85 Negative (falling) transition 850b of switching voltage digital signal 85 Positive transition 852a / 852b / 852c Positive transition 854a / 854b Positive transition 856a / 856b / 856c Sampling interval (hours) 950

[0019] In the present disclosure, a piezoelectric device refers to a device configured to exhibit piezoelectric behavior in which mechanical stress / deformation occurs in response to the application of an electric field. According to an embodiment of the present disclosure, a piezoelectric device may include one or more elements and / or materials configured to exhibit piezoelectric behavior. It may be understood that a piezoelectric device according to an embodiment of the present disclosure may be used in a variety of applications, including, but not limited to, an atomizer, a nebulizer, an ultrasonic device, and the like. For brevity, one or more elements and / or materials capable of exhibiting piezoelectric behavior are hereinafter referred to as a piezoelectric element. In one exemplary application, a piezoelectric device according to an embodiment of the present disclosure is configured as an atomizer suitable for use with a fluid. The fluid may be in the form of a single compound or may be in the form of a solution, suspension, mixture, and the like, of two or more chemicals. The piezoelectric device is configured to induce vibration of the piezoelectric element when the piezoelectric element is in contact with the fluid or when the piezoelectric element is configured to transfer energy to the fluid.

[0020] FIG. 1 is an example of an amplitude-frequency plot showing the relationship between the amplitude of vibration of a piezoelectric element and the operating frequency of an electric field applied to the piezoelectric element. 3 It can be seen that when driven at an operating frequency close to 100 Hz, or at its resonant frequency, the piezoelectric element exhibits vibration at a peak amplitude. If the operating frequency deviates from the resonant frequency 70, the amplitude of vibration drops off rapidly from the peak amplitude, resulting in a significant decrease in the efficiency of the device. The piezoelectric element may be subject to various operating conditions, such as changes in temperature, internal heating, etc., such that the resonant frequency of the piezoelectric element tends to drift from the initial resonant frequency 70. When the piezoelectric element is operating, it is difficult to set the operating frequency to the resonant frequency, since the resonant frequency varies nonlinearly over any period of time. It is observed that when the piezoelectric element is part of a piezoelectric device, the relationship between the amplitude of vibration and the operating frequency is even more unpredictable.

[0021] FIG. 2 illustrates an exemplary schematic circuit of an apparatus 40 configured to operate on power received from a power source 50, where the apparatus 40 includes a piezoelectric device 60 and a driving device 100, according to one embodiment of the present disclosure.

[0022] The piezoelectric device 60 includes at least one piezoelectric element. The driving device 100 is configured to operate or drive the piezoelectric device 60 by providing an alternating electric field at an operating frequency. The driving device 100 can be said to operate or drive the piezoelectric device by providing a voltage across the piezoelectric device.

[0023] According to an embodiment of the present disclosure, the apparatus of FIG. 2 may be configured such that FIGS. 3A, 3B, and 3C are amplitude-time plots showing the relationship between the voltage 810a / 810b / 810c across the piezoelectric device 60 and the current 820a / 820b / 820c drawn by the piezoelectric device 60. FIG. 3A illustrates the situation where the operating frequency is lower than the target frequency, and the voltage 810a leads the current 820a. FIG. 3B illustrates the situation where the operating frequency is higher than the target frequency, and the voltage 810b lags the current 820b. In both of these cases, the voltage 810a / 810b across the piezoelectric device and the current 820a / 820b drawn are said to be out of phase. The apparatus is configured to drive the piezoelectric device at or near the target frequency. The resulting voltage 810c and current 820c waveforms are said to be in phase, or in other words, synchronous, as illustrated by FIG. 3C.

[0024] FIG. 4A illustrates, by way of a schematic block diagram, an embodiment of an atomizer 40 that may be used to atomize a fluid, such as a viscous fluid. The atomizer 40 includes a piezoelectric device 60 and a driving device 100. The driving device 100 is configured to drive the piezoelectric device 60. The driving device 100 is configured to provide a switching voltage for driving the piezoelectric device 60. The driving device is configured to control an operating frequency of the switching voltage. A power source 50 may be coupled to the driving device 100 to enable operation of the atomizer 40. In one example, the power source 50 includes a direct current (DC) power source, such as a battery. The atomizer 40 may be configured as a portable and / or handheld device, and the driving device 100 may be configured to convert the DC power source into an alternating current (AC) switching voltage 80 suitable for driving the piezoelectric device 60 to perform atomization of the viscous fluid. The driving device 100 may be configured to provide the switching voltage 80 at an operating frequency that enables the piezoelectric device 60 to be driven at or near a target frequency. In another example, the power source 50 is configured as an AC power source. The atomizer 40 may include a driving device 100 configured to convert an AC power source into an alternating current (AC) switching voltage 80 suitable for driving the piezoelectric device 60 to effect atomization of the viscous fluid. The driving device 100 may be configured to provide the switching voltage 80 at an operating frequency that enables the piezoelectric device 60 to be driven at or near a target frequency.

[0025] According to one exemplary embodiment, the atomizer 40 is configured to atomize a viscous fluid, such as a fluid having a viscosity of 5 centipoise (cp) or greater. In another example, the atomizer 40 is configured to atomize water, an aqueous solution, an oil, an oil-based solution, or a mixture thereof.

[0026] One embodiment of the driving device 100 is shown in FIG. 4B. The driving device 100 includes an alternator 110, a controller 120 coupled to the alternator 110, a sense load 130 coupled to the piezoelectric device 60, and a logic device 140 coupled between the controller and the sense load 130. The alternator 110 is configured to convert power from a power source 50 into a switching voltage 80. The switching voltage 80 may be provided to drive the piezoelectric device 60. As an example, a direct current (DC) voltage from the power source 50 is converted and supplied to the piezoelectric device 60 as an alternating current (AC) switching voltage 80. By controlling the alternator 110, the controller 120 is configured to control an operating frequency of the switching voltage 80. Furthermore, when the switching voltage 80 is supplied to the piezoelectric device 60, a sense voltage 90 across the sense load 130 may be sensed. The logic device 140 may be configured to sense or sample the sense voltage 90, and in response to the sense voltage 90, the logic device 140 may be configured to instruct the controller 120 to vary the operating frequency. The sense voltage 90 may be considered to correspond to a phase or state of the piezoelectric device 60. As an example, the sense voltage 90 may be taken to be in phase with a corresponding current through the piezoelectric device 60, i.e., the sense voltage 90 may be considered to reflect a state of the piezoelectric device 60. Alternatively, the sense voltage 90 may be considered to correspond to an operating state of the piezoelectric device 60, such as a vibration state of the piezoelectric device 60.

[0027] For example, logic device 140 may be configured to instruct controller 120 to increase or decrease the operating frequency provided to the piezoelectric device in response to whether sense voltage 90 is in phase or out of phase with switching voltage 80. Further optionally, logic device 140 may be configured to receive switching voltage 80 as an input. Logic device 140 may be configured to receive inputs from both switching voltage 80 and sense voltage 90 and determine, based on logic rules, whether to increase or decrease the operating frequency. As an example, logic device 140 may be configured to instruct controller 120 to decrease the operating frequency when sense voltage 90 is in phase with switching voltage 80. Logic device 140 may be configured to instruct controller 120 to increase the operating frequency when sense voltage 90 is out of phase with switching voltage 80.

[0028] 5 illustrates a schematic diagram of a driving device 200 according to another embodiment of the present disclosure. The driving device 200 may be coupled to a power source 50 and a piezoelectric device 60. The piezoelectric device 60 includes one or more piezoelectric elements 64. Optionally, the piezoelectric device 60 may include a transformer 62. The transformer 62 may be configured to step up the switching voltage 80 to a voltage suitable for driving the piezoelectric elements 64. In this embodiment, the driving device 200 includes an alternator, which includes a full bridge 210 (H-bridge) formed from switches 212 / 214 / 216 / 218. The full bridge 210 is operably coupled to and controllable by a controller 220. A logic device 240 is coupled to the controller 220. The switches 212 / 214 / 216 / 218 may include metal oxide semiconductor field effect transistors (MOSFETs) or other suitable electronic switching devices such as bipolar transistors, IGBTs, SCRs, TRIACs, DIACs, etc., or a combination of devices selected therefrom. In one example, the alternator includes a plurality of MOSFETs. In one example, the alternator is configured with low voltage devices such as MOSFETs such that the drive device can operate with a conventional battery acting as a power source while still allowing sufficient vibration of the piezoelectric elements. The controller 220 is configured to control the opening and closing of the switches 212 / 214 / 216 / 218, thereby converting a direct current (DC) voltage from the power source 50 into an alternating current (AC) switching voltage 80 that is provided to drive the piezoelectric device 60.

[0029] 6A and 6B show the driving device of FIG. 5 in operation. Referring to FIG. 6A, in a first mode of operation, the switches 212 and 218 are closed and the switches 214 and 216 are open. The current 80a due to the switching voltage 80 is in a first direction through / within the transformer 62. In a second mode of operation, as shown in FIG. 6B, the switches 212 and 218 are open and the switches 214 and 216 are closed. The current 80b due to the switching voltage 80 is in a second direction through / within the transformer 62, the second direction being opposite to the first direction. The driving device is configured to alternate between the first and second modes of operation, thereby providing a switching voltage 80 across the piezoelectric device, the switching voltage 80 being an AC voltage. An example of a switching voltage 80 that may be provided is shown in FIG. 10A. In one example, the switching voltage 80 may be a square wave or may approximate a square wave. In one example, by controlling the switches 212 / 214 / 216 / 218, the controller 220 can convert a DC voltage from the power source 50 into an AC switching voltage 80 across the piezoelectric device 60. Additionally, the controller 220 may be configured to vary an operating frequency of the switching voltage 80. The controller 220 may be configured to controllably vary a frequency of switching between a first mode of operation and a second mode of operation, the frequency corresponding to the operating frequency of the switching voltage 80. The controller 220 may be configured to controllably vary a speed of opening and closing of the switches 212 / 214 / 216 / 218, thereby varying the operating frequency of the switching voltage 80.

[0030] 5, the driving device 200 may further include one or more analog-to-digital converters (ADCs) 262 / 264. The ADCs may be coupled to the full bridge 210 to provide a digital signal 85 based on the switching voltage 80, as shown by FIGS. 10A and 10B. The ADCs may be coupled to a sense load 230, which is coupled to the piezoelectric device 60. The sense load 230 is configured to determine a sense voltage 90 across the sense load 130. The ADCs may be coupled to the sense load 230 to provide a digital signal 95 based on the sense voltage 90, as shown by FIGS. 11A and 11B. The driving device 200 may be configured such that the sense voltage 90 corresponds to a phase of the piezoelectric device 60. As an example, the sense load 230 includes a purely resistive element. As shown in FIGS. 6A and 6B, the driving device may be configured such that the currents 80a / 80b pass through the sense load 230 in the same direction regardless of whether the driving device or the bridge is operating in a first or second mode of operation. 11A, as an example of a sense voltage 90 across the sense load 230, the sense voltage 90 across the sense load 230 may be configured to be generally positive with a negative portion of the sense voltage 94 corresponding to the full-bridge dead time. ADC 262 and ADC 264 are configured to convert the switching voltage 80 and the sense voltage 90, respectively, into corresponding digital waveforms.

[0031] FIG. 10A illustrates an example of a switching voltage 80, and FIG. 10B illustrates an example of a corresponding switching voltage digital signal 85 transitioning between two states. In this example, the drive device includes a circuit configured to derive a switching voltage digital signal 85 from the switching voltage 80, such as by converting the switching voltage 80 to a digitized signal. For example, a positive portion of the switching voltage 82 may be digitized to a high voltage 87, i.e., 5V (volts), while a negative portion of the switching voltage 84 may be digitized to a low voltage 89, i.e., 0V. In another example, the circuit is configured to convert the switching voltage signal 80 to a signal 85 characterized by a square wave. The square wave 85 may be described with respect to a high voltage state 87 and a low voltage state 89, where it may be understood that the high voltage state is characterized by a higher voltage value than the low voltage state. The voltage values ​​shown in FIG. 10B are for illustrative purposes only. The voltage value associated with the low voltage state need not be 0V, and the voltage value associated with the high voltage state need not be 5V. It may further be appreciated that the switching voltage digital signal 85 corresponds to the switching voltage 80. In one example, the switching voltage digital signal 85 is characterized by a waveform that provides rising edges at a frequency corresponding to the frequency of the switching voltage 80. In another example, the switching voltage digital signal 85 is characterized by a waveform that provides falling edges at a frequency corresponding to the frequency of the switching voltage 80.

[0032] FIG. 11A illustrates an example of a sense voltage 90, and FIG. 11B illustrates a sense voltage digital signal 95 corresponding to the sense voltage 90. In this example, the drive device includes a circuit configured to derive a sense voltage digital signal 95 from the sense voltage 90, such as by converting the sense voltage 90 to a digitized signal. For example, the positive portion of the sense voltage 92 is digitized to a high voltage 97, i.e., 5V, while the negative portion of the sense voltage 94 is digitized to a low voltage 99, i.e., 0V. These digital signals 85 / 95 serve as inputs to the logic device 240. In another example, the circuit is configured to convert the sense voltage signal 90 to a signal 95 characterized by a square wave. The square wave 95 can be described with respect to a high voltage state 87 and a low voltage state 89, where it can be understood that the high voltage state is characterized by a higher voltage value than the low voltage state. The voltage values ​​illustrated in FIG. 11B are for illustrative purposes only. The voltage value associated with the low voltage state need not be 0V, and the voltage value associated with the high voltage state need not be 5V. It may further be seen that the sense voltage digital signal 95 corresponds to the sense voltage 90. In one example, the sense voltage digital signal 95 is characterized by a waveform that provides voltage states 99 at a frequency that corresponds to the frequency of the sense voltage 90. In another example, the sense voltage digital signal 95 is characterized by a waveform that provides voltage states 99, where the voltage states 99 correspond to a portion of the sense voltage that is below a threshold voltage. In the example shown by Figures 11A and 11B, the circuit is configured such that the threshold voltage is 0V, and the sense voltage digital signal 95 includes a low voltage state 99 that corresponds to the negative portion 94 of the sense voltage 90. In another example, the sense voltage digital signal 95 includes a series of signal pulses, successive signal pulses spaced apart by an interval, each of the intervals being coincident (in time) with a sense voltage that is below the threshold voltage.

[0033] Referring to FIG. 7, in another embodiment of the driving device 300, one or both of the ADCs may be configured in the form of an op-amp comparator 362 / 364. The op-amp comparator is configured such that the positive part of the voltage is amplified and converted to the upper saturation voltage of the op-amp comparator, while the negative part of the voltage is amplified and converted to the lower saturation voltage of the op-amp comparator. As an example, FIGS. 10A and 10B show the provision of an op-amp comparator 362 with an upper saturation voltage of 5V and a lower saturation voltage of 0V configured to convert the switching voltage 80 to the switching voltage digital signal 85. In another example, FIGS. 11A and 11B show the provision of an op-amp comparator 364 with an upper saturation voltage of 5V and a lower saturation voltage of 0V for converting the sensed voltage 80 to the sensed voltage digital signal 95.

[0034] 8A and 8B, the driving device 400 includes a half bridge 410, such as formed from switches 412 / 414. A controller 420 is configured to control the opening and closing of the switches 412 / 414, thereby converting a direct current (DC) voltage from a power source 50 into an alternating current (AC) switching voltage 80, which is provided to a piezoelectric device 60. In this embodiment, the power source 50 may be a battery power source, and the piezoelectric device 60 includes a center tapped transformer 66 and a piezoelectric element 64.

[0035] 8A, when switch 412 is closed and switch 414 is open, current 80a due to the switching voltage flows in a first direction to a first portion of center-tapped transformer 66. Conversely, as shown in FIG 8B, when switch 412 is open and switch 414 is closed, current 80b flows in a second direction opposite to the first direction to a second portion of center-tapped transformer 66. By controlling switches 412 and 414, controller 420 can convert a DC voltage from power source 50 to an AC switching voltage across the center-tapped transformer.

[0036] In addition, the controller 420 controls the speed at which the switches 412 / 414 open and close, thereby varying the operating frequency of the switching voltage. The drive device is configured such that, during operation, current flows through the sense load 430 in the same direction, regardless of the direction of current flow in the transformer.

[0037] From the above examples, it can be seen that there are various ways of implementing the embodiments of the present disclosure. For example, the driving device may be configured to provide digital signals 85 / 95 to the logic device 240, the digital signals including a switching voltage digital signal and a sense voltage digital signal, the switching voltage digital signal corresponding to the switching voltage provided to drive the piezoelectric device, and the sense voltage digital signal corresponding to the sense voltage. The driving device may be further configured to use the output from the ADC 262 / 264 as an input to the logic device 240. The logic device 240 may be configured such that, in response to the received input, the logic device 240 instructs the controller 220 to vary the operating frequency of the switching voltage 80. FIG. 9 illustrates an alternative embodiment in which the driving device 500 includes a microcontroller unit (MCU) 520. The microcontroller unit may be coupled to an alternator, such as a full bridge 510 and a sense load 530. In this embodiment, the microcontroller unit 520 is configured to sense the sense voltage across the sense load and control the operating frequency of the switching voltage driving the piezoelectric device. The microcontroller unit 520 may be configured such that in response to the sensed voltage, the microcontroller unit 520 varies its operating frequency.

[0038] FIG. 12 illustrates voltage signals applicable to any of the above-mentioned embodiments. In FIG. 12, an example of a switching voltage digital signal 85, a sense voltage digital signal 95a in phase with the switching voltage digital signal, and a sense voltage digital signal 95b out of phase with the switching voltage digital signal are illustrated on a common time axis. A driving device according to an embodiment of the present disclosure is configured such that for each transition 850 of the switching voltage digital signal 85, the driving device can determine whether the sense voltage and the switching voltage are in phase or out of phase with each other. For example, in FIG. 12, when the transition 850 of the switching voltage digital signal 85 is found to correspond to (match) a low voltage state of the sense voltage digital signal 95a, the sense voltage can be considered to be in phase with the switching voltage. Alternatively, for example, in FIG. 12, when the transition 850 of the switching voltage digital signal 85 is found to correspond to (match) a high voltage state of the sense voltage digital signal 95b, the sense voltage can be considered to be out of phase with the switching voltage. Thus, by sensing or sampling the amplitude of the sensed voltage digital signal 95 at a time corresponding to a transition 850 of the switching voltage digital signal 85, the drive device can determine whether the sensed voltage is in phase with the switching voltage. Sampling the amplitude or value of the sensed voltage digital signal 95 may occur at a rising transition of the switching voltage digital signal or at a falling transition of the switching voltage digital signal. The drive device is further configured to determine whether the piezoelectric device is at or near the target frequency based on whether the sensed voltage and the switching voltage are determined to be in phase or out of phase with respect to one another. Alternative embodiments include methods performed on non-digital signals where the sensed voltage is sampled at one or more transitions of the switching voltage in determining whether the piezoelectric device is operating as desired or not.

[0039] Considering the above applicable to embodiments such as the atomizer 40 or the driving device 100 / 200 / 300 / 400 / 500, the respective logic device may be configured to sense or sample the sensed voltage 90 and / or the sensed voltage digital signal 95 at transitions 850 of the switching voltage 80 and / or the switching voltage digital signal 85. According to embodiments of the present disclosure, the obtained samples may be used in determining whether the piezoelectric device is operating at the target frequency. In one embodiment as shown in FIG. 13, the sensing or sampling of the sensed voltage digital signal 95 may be triggered or performed periodically at selected positive (rising) transitions 850a of the switching voltage digital signal 85. In another embodiment as shown in FIG. 14, the sensing or sampling of the sensed voltage digital signal 95 may be triggered or performed periodically at selected negative (falling) transitions 850b of the switching voltage digital signal 85. In yet another embodiment as shown in FIG. 15, the sensing or sampling of the sensed voltage digital signal 95 may be triggered or performed at selected discontinuous transitions 850c of the switching voltage digital signal 85. In one embodiment shown in FIG. 16, the logic device may be configured to sense or sample the sensed voltage digital signal 95 multiple times within a sampling interval 950 and then determine an average of the multiple sensed values.

[0040] Alternatively, one or more of the above methods may be performed based on a non-digital signal, where the sensed voltage is compared against a logic rule, such as the polarity of the sensed voltage. Additionally, sensing or sampling of the sensed voltage or sensed voltage digital signal may be performed at either periodic or non-periodic time intervals, depending on the purpose and / or operating conditions of the application.

[0041] In one embodiment, the logic device may be a digital flip-flop, configured to sense or sample the sense voltage digital signal 95 when triggered by a transition of the switching voltage digital signal 85. Thus, upon a transition of the switching voltage digital signal 85, the sense voltage digital signal 95 is sensed or sampled by the digital flip-flop. According to the logic rules embodied by the digital flip-flop, the digital flip-flop provides an output Q to the controller, which serves as an instruction to increase or decrease the operating frequency of the switching voltage. Optionally, the digital flip-flop may also be configured to receive an input of the switching voltage digital signal 85.

[0042] 17-21 illustrate an exemplary embodiment of the above-described drive device in operation. In the exemplary embodiment as shown in FIG. 17, when the drive device is turned on, the drive device operates at a target frequency 70 (in this example, 10 3 18, when the output Q is equal to a first state (e.g., equal to "1") corresponding to a sense voltage that is out of phase with the switching voltage, the controller is configured to increase the operating frequency of the switching voltage. Conversely, when the output Q is equal to a second state (e.g., not equal to "1") corresponding to a sense voltage that is in phase with the switching voltage, the controller is configured to decrease the operating frequency of the switching voltage.

[0043] 19 and 20 show plots of frequency versus time, superimposed and exaggerated for ease of understanding. Plot 74 represents an ideal target frequency 74 of a piezoelectric device. In an ideal, hypothetical case, the ideal target frequency would remain constant throughout the operation of the piezoelectric device, such that efficient operation of the piezoelectric device could be easily achieved by setting the operating frequency to the same frequency as the ideal target frequency. However, in actual operation of a piezoelectric device, due to self-heating, environmental factors, and / or other influences, the piezoelectric device may exhibit a target frequency 70 whose value varies over the course of operation of the piezoelectric device. Plot 70 represents one possible behavior of the target frequency, where the target frequency "drifts" or increases over the course of operation of the piezoelectric device. Plot 70 in FIG. 20 shows another possible example where the target frequency does not vary linearly with time. It is also conceivable that the target frequency may increase for a period of time after the piezoelectric device is turned on and then decrease. For example, it may be useful to know the target frequency at any point in time, so that the operating frequency can be set to the same frequency value and the piezoelectric device operates at a desired level of efficiency. However, in practical applications, the target frequency is often not known. Without knowing the target frequency, it can be difficult to determine the appropriate operating frequency of the piezoelectric device at any given time.

[0044] Embodiments of the present disclosure address this and other problems by providing a drive device configured to drive a piezoelectric device at an operating frequency 72 configured to track a target frequency 70. As shown in Figures 19 and 20, the operating frequency can be said to track the target frequency over a period of time when the difference between the operating frequency and the target frequency is less than a predetermined value at any time within the period of time. The operating frequency can be said to track the target frequency over a period of time when the operating frequency is at or near the target frequency for the period of time. As the target frequency increases, the operating frequency also increases. As the target frequency decreases, the operating frequency also decreases. The drive device is configured to maintain the operating frequency 72 tracking the target frequency 70 without the preliminary step of determining the value of the target frequency.

[0045] According to one embodiment, the drive device is configured to execute a method for increasing the operating frequency 72 from a first operating frequency to a second operating frequency. This may be performed repeatedly until the second operating frequency is at or near the target frequency. The second operating frequency may be considered to be at or near the target frequency when it is within a target frequency band. The target frequency band may be predefined as a range of frequencies, which includes at least one resonant frequency (or harmonic) of the piezoelectric device. The drive device is configured to determine whether the second operating frequency is within the target frequency band and vary the operating frequency accordingly. If the second operating frequency is below a lower bound of the target frequency band, the operating frequency is increased and this is repeated until the operating frequency reaches / enters the target frequency band. The drive device is configured such that once it is determined that the operating frequency is within the target frequency band, the operating frequency is maintained within or near the target frequency band. The operating frequency may be said to track the target frequency when the operating frequency is within or near the target frequency band.

[0046] According to one embodiment, the drive device is configured to execute a method including alternatingly increasing 72a and decreasing 72b the operating frequency by a predetermined value. According to one embodiment, the drive device is configured to execute a method including repeatedly increasing or decreasing the operating frequency by a predetermined value once it is determined that the operating frequency is within or near the target frequency band. Counterintuitively, the operating frequency 72 continues to repeatedly "move" toward and / or away from the target frequency 70 even if the operating frequency is already at or near the target frequency. Thus, according to one embodiment, it can be seen that when the operating frequency is tracked to the target frequency, tracking may involve occasionally increasing the difference between the operating frequency and the target frequency and occasionally decreasing the difference between the operating frequency and the target frequency. The method may involve periodically varying the operating frequency by a predetermined value. If the target frequency 70 drifts during operation, the change in the target frequency can also contribute to an increase or decrease in the difference between the operating frequency and the target frequency. In this manner, or in a similar manner, of increasing or decreasing the operating frequency, tracking with the operating frequency can be implemented to address issues associated with piezoelectric resonant frequency drift. In this embodiment, following a flow chart logic such as that shown in Figure 18, the target frequency 70 can represent a possible upper bound for the operating frequency 72. The target frequency 70 can also represent a possible upper limit for the target frequency band.

[0047] FIG. 21 shows an example of an exaggerated digital signal showing the change of the operating frequency upon sensing or sampling at successive positive transitions 852a / 852b / 852c. According to one embodiment, the drive device is configured to determine a sense voltage digital signal 95 at a first positive transition 852a of the switching voltage digital signal. In this case, the sense voltage digital signal is found to be in a low voltage state corresponding to a sense voltage that is in phase with the switching voltage. In response, the operating frequency (of the switching voltage) is decreased. At a second positive transition 852b, the sense voltage digital signal 95 is found to be in a high voltage state. This can be considered to correspond to a sense voltage that is out of phase with the switching voltage. In response, the operating frequency (of the switching voltage) is increased. At a third positive transition 852c, the sense voltage digital signal 95 is found to correspond to a sense voltage that is in phase with the switching voltage, which will trigger a decrease (downward adjustment) of the operating frequency.

[0048] In another embodiment as shown in FIG. 22, the piezoelectric device may define a target frequency band 70a having an upper limit 70b and a lower limit 70c. When the operating frequency 72 of the switching voltage is within the target frequency band 70a, i.e., between the upper limit 70b and the lower limit 70c, the piezoelectric device exhibits a peak or near-peak vibration amplitude and efficiency. When the operating frequency 72 is within the target frequency band 70a (which may include one or both of the upper and lower limits), the piezoelectric device may be observed to operate efficiently enough for its intended purpose, e.g., the resulting piezoelectric vibration is sufficient to atomize a viscous fluid. As an example, the target frequency band may be a resonant frequency band, or a range of frequency values ​​near a resonant (harmonic) frequency. As an example, the target frequency band may be about + / - 100 Hz (Hertz) near a target frequency of about 500 kHz (Kilohertz). In another example, the target frequency band may be 100 Hz (Hertz), and the target frequency may vary between 100 kHz and 120 kHz at the time the piezoelectric device begins to operate. In yet another example, the target frequency band may be 2 kHz. These examples are provided merely to aid in understanding.

[0049] Optionally, the resolution or size of each change made to the operating frequency may be varied to control how accurately the operating frequency tracks the target frequency. For example, if each change is small enough relative to the target frequency 70, or small relative to the target frequency band 70a, the operating frequency will track the actual target frequency 70 or target frequency band 70a more accurately. This causes the piezoelectric device to appear to continuously drive at or near the target frequency.

[0050] An example of an exaggerated digital signal showing the change in operating frequency 72 upon sensing or sampling at successive positive transitions 854a / 854b is shown in Figure 22. At the first positive transition 854a, the sensed voltage digital signal 95 corresponds to a sensed voltage that is out of phase with the switching voltage. Based on this, the piezoelectric device is detected as operating outside of the target frequency band 70a.

[0051] In response, the operating frequency 72 of the switching voltage is increased by a predetermined value. At the second positive transition 854b, the sensed voltage digital signal 95 corresponds to a sensed voltage that is in phase with the switching voltage. Based on this, the piezoelectric device is sensed to be operating within the target frequency band 70a. The operating frequency 72 of the switching voltage is decreased by a predetermined value. The upper limit 70b of the target frequency band 70a serves as an upper bound (upper limit) of the operating frequency 72. The predetermined value is equal to or less than the target frequency band 70a. The target frequency band may be defined by the difference between the upper limit 70b and the lower limit 70c. It may be understood that the operating frequency does not exceed the upper limit 70b. Although the operating frequency 72 is either within or outside the target frequency band 70a in the course of operation over a period of time, in an actual implementation, it may be observed that the piezoelectric device continuously functions as desired over a period of time. For example, an atomizer according to one embodiment of the present disclosure may provide a continuous delivery of atomized viscous fluid over a period of operation, but over the same period, the operating frequency may repeatedly move in and out of a target frequency band. For the avoidance of doubt, for the purposes of this disclosure, this is an example of an operating frequency that tracks a target frequency band or target frequency.

[0052] As shown in FIG. 23, in one embodiment, over a period of time 950, there may be multiple instances when the sensed voltage is sensed and a corresponding adjustment is made to the operating frequency. Each adjustment to the operating frequency may be an increase or a decrease. As shown, the size of each decrease 72b in the operating frequency may be smaller than the size of each increase 72a in the operating frequency. In this way, the operating frequency remains within the target frequency band 70a for a longer period of time during operation of the piezoelectric device while intermittently straying from the target frequency band 70a. Alternatively, the decrease 72b in the operating frequency 72 may be set to a value equal to the increase 72a in the operating frequency 72.

[0053] 24-26 illustrate one exemplary embodiment of the above-described drive device in operation. In the exemplary embodiment as shown in FIG. 24, when the drive device is turned on, the drive device operates at a target frequency 70 (in this example, 10 3 25, when the output Q is equal to a first state (e.g., equal to "1") corresponding to a sense voltage that is out of phase with the switching voltage, the controller is configured to decrease the operating frequency of the switching voltage. Conversely, when the output Q is equal to a second state (e.g., not equal to "1") corresponding to a sense voltage that is in phase with the switching voltage, the controller is configured to increase the operating frequency of the switching voltage.

[0054] FIG. 26 shows a plot of frequency versus time, superimposed and exaggerated for ease of understanding. Plot 74 represents an ideal target frequency 74 of a piezoelectric device. In an ideal, hypothetical case, the ideal target frequency would remain constant throughout operation of the piezoelectric device, such that efficient operation of the piezoelectric device could be easily achieved by setting the operating frequency to the same frequency as the ideal target frequency. However, in actual operation of a piezoelectric device, due to self-heating, environmental factors, and / or other influences, the piezoelectric device may exhibit a target frequency 70 whose value varies over the course of operation of the piezoelectric device. Plot 70 represents one possible behavior of the target frequency, where the target frequency "drifts" or increases over the course of operation of the piezoelectric device. It is also conceivable that the target frequency may increase for a period of time after the piezoelectric device is turned on and then decrease. For example, it may be useful to know the target frequency at any time such that the operating frequency can be set to the same frequency value and the piezoelectric device operates at a desired level of efficiency. However, in practical applications, the target frequency is often not known. Without knowing the target frequency, it may be difficult to determine the appropriate operating frequency of the piezoelectric device at any time.

[0055] Embodiments of the present disclosure address this and other problems by providing a drive device configured to drive a piezoelectric device at an operating frequency 72 configured to track a target frequency 70. As shown in FIG. 26, the operating frequency can be said to track the target frequency over a period of time when the difference between the operating frequency and the target frequency is less than a predetermined value at any time within the period of time. The operating frequency can be said to track the target frequency over a period of time when the operating frequency is at or near the target frequency for the period of time. As the target frequency increases, the operating frequency also increases. As the target frequency decreases, the operating frequency also decreases. The drive device is configured to maintain the operating frequency 72 tracking the target frequency 70 without the preliminary step of determining the value of the target frequency.

[0056] According to one embodiment, the drive device is configured to perform a method of decreasing the operating frequency 72 from a first operating frequency to a second operating frequency. This may be performed repeatedly until the second operating frequency is at or near the target frequency. The second operating frequency may be considered to be at or near the target frequency when it is within a target frequency band. The target frequency band may be predefined as a range of frequencies, which includes at least one resonant frequency (or harmonic) of the piezoelectric device. The drive device is configured to determine whether the second operating frequency is within the target frequency band or not, and vary the operating frequency accordingly. If the second frequency is higher than an upper bound of the target frequency band, the operating frequency is decreased and this is repeated until the operating frequency reaches / enters the target frequency band. The drive device is configured such that once it is determined that the operating frequency is within the target frequency band, the operating frequency is maintained at or near the target frequency band. The operating frequency can be said to track the target frequency when the operating frequency is within or near the target frequency band.

[0057] According to one embodiment, the drive device is configured to execute a method including alternatingly increasing 72a and decreasing 72b the operating frequency by a predetermined value. According to one embodiment, the drive device is configured to execute a method including repeatedly increasing or decreasing the operating frequency by a predetermined value once it is determined that the operating frequency is within or near the target frequency band. Counterintuitively, the operating frequency 72 continues to repeatedly "move" toward and / or away from the target frequency 70 even if the operating frequency is already at or near the target frequency. Thus, according to one embodiment, it can be seen that when the operating frequency is tracked to the target frequency, tracking may involve occasionally increasing the difference between the operating frequency and the target frequency and occasionally decreasing the difference between the operating frequency and the target frequency. The method may involve periodically varying the operating frequency by a predetermined value. If the target frequency 70 drifts during operation, the change in the target frequency can also contribute to an increase or decrease in the difference between the operating frequency and the target frequency. In this manner, or in a similar manner, of increasing or decreasing the operating frequency, tracking with the operating frequency can be implemented to address issues associated with piezoelectric resonant frequency drift. In this embodiment, following a flow chart logic such as that shown in Figure 25, the target frequency 70 can represent a possible lower bound for the operating frequency 72. The target frequency 70 can also represent a possible lower limit for the target frequency band.

[0058] 28 shows an example of an exaggerated digital signal showing the change in operating frequency upon sensing or sampling at successive positive transitions 856a / 856b / 856c. According to one embodiment, the drive device is configured to determine a sense voltage digital signal 95 at a first positive transition 856a of the switching voltage digital signal. In this case, the sense voltage digital signal is found to be in a low voltage state corresponding to a sense voltage that is in phase with the switching voltage. In response, the operating frequency (of the switching voltage) is increased.

[0059] At the second positive transition 856b, the sense voltage digital signal 95 is seen to be in a high voltage state, which can be seen to correspond to a sense voltage that is out of phase with the switching voltage. In response, the operating frequency (of the switching voltage) is decreased. At the third positive transition 856c, the sense voltage digital signal 95 is seen to correspond to a sense voltage that is in phase with the switching voltage, which will trigger an increase (upward adjustment) of the operating frequency.

[0060] Optionally, the resolution or size of each change made to the operating frequency may be varied to control how accurately the operating frequency tracks the target frequency. For example, if each change is small enough relative to the target frequency 70, or small relative to the target frequency band 70a, the operating frequency will track the actual target frequency 70 or target frequency band 70a more accurately. This causes the piezoelectric device to appear to continuously drive at or near the target frequency.

[0061] An example continues below in which the driving device provides an initial operating frequency 72a that is higher than the target frequency 70 associated with the piezoelectric device. Upon a first trigger, the sensed voltage digital signal corresponds to a sensed voltage that is out of phase with the switching voltage. Based on this, the piezoelectric device is detected as operating outside the target frequency band. In response, the operating frequency of the switching voltage is decreased by a predetermined value. Upon a second trigger, the sensed voltage digital signal corresponds to a sensed voltage that is in phase with the switching voltage. Based on this, the piezoelectric device is detected as operating within the target frequency band. The operating frequency of the switching voltage is increased by a predetermined value. The lower limit of the target frequency band serves as a lower bound (lower limit) of the operating frequency. The predetermined value is equal to or less than the target frequency band. The target frequency band may be defined by the difference between the upper limit and the lower limit. It may be understood that the operating frequency does not fall below the lower limit in this example. Although the operating frequency is either within or outside the target frequency band in the course of operation over a period of time, in an actual implementation, the piezoelectric device may be observed to function continuously as desired over a period of time. For example, an atomizer according to one embodiment of the present disclosure may provide a continuous delivery of atomized viscous fluid over a period of operation, but over the same period, the operating frequency may repeatedly move in and out of a target frequency band. For the avoidance of doubt, for the purposes of this disclosure, this is an example of an operating frequency that tracks a target frequency band or target frequency.

[0062] In one embodiment, there may be multiple instances over a period of time when the sensed voltage is sensed, and a corresponding adjustment is made to the operating frequency. Each adjustment to the operating frequency may be an increase or a decrease. The size of each decrease in the operating frequency may be less than the size of each decrease in the operating frequency, such that the operating frequency remains within the target frequency band for a longer period of time during operation of the piezoelectric device while intermittently straying from the target frequency band. Alternatively, the decrease in the operating frequency may be set to a value equal to the increase in the operating frequency.

[0063] Referring to FIG. 29A, an example of a current 830 drawn by a piezoelectric device driven by a piezoelectric device or driving device 100 / 200 / 300 / 400 / 500 as described in the atomizer 40 is shown. It can be seen that when the atomizer 40 or driving device 100 / 200 / 300 / 400 / 500 is turned on, the current drawn by the piezoelectric device increases, and then the current always remains at a high value as the operating frequency driving the piezoelectric device approaches or reaches the target frequency. Although the target frequency will drift over time due to self-heating, environmental changes, etc., the operating frequency will follow the drift accordingly, and thus the current drawn by the piezoelectric device can be kept high and relatively constant. This allows for a consistent high amplitude of vibration output from the piezoelectric device, and therefore constant atomization of the viscous fluid. Conversely, FIG. 29B shows a current 840 drawn by a piezoelectric device driven by another device, which causes the device to periodically scan or sweep the change in the target frequency and then adjust the operating frequency accordingly. Thus, the current drawn 840 experiences periodic dips 840a and returns 840b, resulting in inconsistent amplitude of oscillations and therefore atomization of the fluid.

[0064] In one embodiment, an atomizer having a piezoelectric device has an operating frequency that is adjustable in steps to increase or decrease the operating frequency, the amount by which it is adjusted in each step being predetermined, where the operating frequency increases when the piezoelectric device is in phase with the operating frequency and decreases when the piezoelectric device is out of phase with the operating frequency. The operating frequency is adjustable by discrete amounts to increase or decrease the operating frequency, where the size of the discrete amounts is predetermined. The size of the discrete amounts is independent of the difference between the operating frequency and a target frequency. The size of the discrete amounts is independent of the difference between the operating frequency and a target frequency band. The size of the discrete amounts is independent of the difference between the operating frequency and an upper limit of the target frequency band. The size of the discrete amounts is independent of the difference between the operating frequency and a lower limit of the target frequency band.

[0065] FIG. 30 illustrates a method 700 of driving a piezoelectric device. The method includes providing (710) a switching voltage across the piezoelectric device at an operating frequency, sensing (720) a sense voltage corresponding to the phase of the piezoelectric device, and varying (730) the operating frequency provided to the piezoelectric device in response to whether the sense voltage is in phase or out of phase with the switching voltage. The change in operating frequency is selected from one of: (a) increasing the operating frequency by a first value, and (b) decreasing the operating frequency by a second value. The amount (quantum or absolute value) of the change to the operating frequency is predetermined or independent of whether the sense voltage is in phase or out of phase with the switching voltage. The change to the operating frequency is made regardless of whether the sense voltage is in phase or out of phase with the switching voltage.

[0066] Optionally and additionally, the method may include converting (740) the switching voltage into a switching voltage digital signal having at least one transition between two states, and using the at least one transition to trigger sensing of the sensed voltage. The method may further include converting (750) the sensed voltage into a sensed voltage digital signal.

[0067] The method may further include comparing 760 the switching voltage digital signal to the sense voltage digital signal to determine whether the sense voltage is in phase or out of phase with the switching voltage. The method may further include periodically repeating 770 at the sampling frequency. The resulting operating frequency tracks a target frequency band to provide desired performance of the piezoelectric device.

[0068] An atomizer for liquids comprising: a housing; a power source; a piezoelectric device operable with a switching voltage; and a circuit including a sense load, the sense load being operatively coupled to the piezoelectric device such that a sense voltage across the sense load has a phase corresponding to a phase of the piezoelectric device, the circuit being configured to: determine whether the sense voltage is in phase or out of phase with the switching voltage; and in response to the sense voltage being in phase with the switching voltage when the switching voltage is provided at the operating frequency, modify the operating frequency by a predetermined first value; and in response to the sense voltage being out of phase with the switching voltage when the switching voltage is provided at the operating frequency, modify the operating frequency by a predetermined second value, where if the predetermined first value corresponds to an increase in the value of the operating frequency, the predetermined second value corresponds to a decrease in the value of the operating frequency, and if the predetermined first value corresponds to a decrease in the value of the operating frequency, the predetermined second value corresponds to an increase in the value of the operating frequency, and the circuit is configured to: determine whether the sense voltage is in phase or out of phase with the switching voltage; and modify the operating frequency by one of the predetermined first value and the predetermined second value. the sampling frequency being defined by a selected transition of a switching voltage; and the circuit further comprises an alternator coupled to the piezoelectric device, the alternator configured to provide a switching voltage for driving the piezoelectric device; an analog-to-digital converter configured to convert the switching voltage into a switching voltage digital signal; and a logic device configured such that a selected transition between two states of the switching voltage digital signal triggers sensing of a sensed voltage and a corresponding change to the operating frequency by one of a first predetermined value and a second predetermined value; the alternator comprising a full bridge configured to generate a switching voltage in the form of a square wave.

[0069] The alternator may be configured in a push-pull configuration such that the switching voltage is a square wave, the sense load being a resistive element, and the circuitry is further configured to determine a first occurrence when the operating frequency is within a target frequency band, the target frequency band being a predefined range of frequencies that includes at least one resonant frequency of the piezoelectric device, and in response to the first occurrence, iteratively determine whether the sense voltage is in phase or out of phase with respect to the switching voltage and make a corresponding change to the operating frequency by one of a first predetermined value and a second predetermined value, and the circuitry is further configured to determine a first occurrence when the operating frequency is within a target frequency band, the target frequency band being a predefined range of frequencies that includes at least one resonant frequency of the piezoelectric device, The atomizer is configured to make a corresponding change to the operating frequency so as to vary within the target frequency band, the corresponding change to the operating frequency being made at a time corresponding to a selected transition of the switching voltage, each of the predetermined first value and the predetermined second value being smaller than the range of the target frequency band, each of the predetermined first value and the predetermined second value being independent of a difference in value between the operating frequency and one of an upper limit of the target frequency band and a lower limit of the target frequency band, and each of the predetermined first value and the predetermined second value being independent of a difference in value between the operating frequency and at least one resonant frequency during operation of the atomizer.

[0070] The atomizer may also have a source of liquid or fluid, and the piezoelectric device in operation is configured to transmit energy to provide a non-intermittent flow of atomized fluid over an operating period, and the operating frequency is varied over the operating period.

[0071] The circuit of the atomizer can be further configured to repeatedly determine the first occurrence when the operating frequency is within a target frequency band, the target frequency band being a predefined range of frequencies that includes at least one resonant frequency of the piezoelectric device, and in response to the first occurrence, determine whether the sensed voltage is in phase or out of phase with the switching voltage, and make a corresponding change to the operating frequency by one of a first predetermined value and a second predetermined value, and the circuit can be configured to make the corresponding change to the operating frequency such that the operating frequency varies within the target frequency band, and the corresponding change to the operating frequency can be made at a time corresponding to a selected transition of the switching voltage, and each of the first predetermined value and the second predetermined value is smaller than the range of the target frequency band. During operation of the atomizer, each of the first predetermined value and the second predetermined value can be independent of a difference in value between the operating frequency and one of an upper limit of the target frequency band and a lower limit of the target frequency band, and during operation of the atomizer, each of the first predetermined value and the second predetermined value can be independent of a difference in value between the operating frequency and at least one resonant frequency. The atomizer is configured to atomize a liquid, and the piezoelectric device in operation is configured to transfer energy to the liquid to provide a non-intermittent flow of atomized liquid over an operating period, and the operating frequency is varied over the operating period.

[0072] Detailed embodiments of the present invention are disclosed. However, the disclosed embodiments are merely exemplary of the present invention, which may be embodied in various forms. The specific structural and functional details disclosed should not be interpreted as limitations, but merely as a basis for the claims and as a representative basis for teaching those skilled in the art to variously employ the present invention in substantially any appropriately detailed structure. The titles, headings, terms, and phrases used are not intended to limit the subject matter or scope, but rather to provide an understandable description of the present invention. The present invention is composed of several subparts that independently perform part of the overall function of the present invention and contribute to a system level function when combined with other parts of the present invention. The terms "a" or "an" are defined as one or more than one. The term "plurality" is defined as two or more than two. The term "another" is defined as at least a second or more. The terms "comprise" and / or "have" are defined as comprising (i.e., open language). The term "coupled" is defined as connected, not necessarily directly, and not necessarily mechanically.

[0073] Any element of a claim that does not expressly recite a "means" for performing a particular function or a "step" for performing a particular function is not to be construed as a "means" or "step" clause as defined in 35 U.S.C. 35 U.S.C. 112, paragraph 6. In particular, the use of "step" in the claims herein is not intended to invoke the provisions of 35 U.S.C. 35 U.S.C. 112, paragraph 6.

[0074] INCORPORATION BY REFERENCE: All publications, patents, patent applications, and internet website addresses mentioned in this specification are incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated by reference. U.S. Patent No. 9,149,588; U.S. Patent No. 4,689,515; U.S. Patent No. 4,715,353; U.S. Patent Application No. 20200060337; U.S. Patent No. 7,855,606; U.S. Patent Application No. 20090295455; U.S. Patent Application No. 10603683; China Patent No. 102526848; U.S. Patent No. 5,113,116; U.S. Patent No. 7,119,475; U.S. Patent No. 7,034,800; U.S. Patent Application No. 20090099485. [Explanation of symbols]

[0075] 40 device, atomizer, 50 battery, DC power supply, 60 piezoelectric device, 62 transformer, 64 piezoelectric element, 66 center tap transformer, 70 target frequency, plot, 70a target frequency band, 70b upper limit, 70c lower limit, 72 operating frequency, 72a increasing operating frequency, 72b decreasing operating frequency, 74 ideal target frequency, 80 alternating current (AC) switching voltage, 80a current, 80b current, 85 switching voltage digital signal, 87 high voltage, 89 low voltage, 90 sensed voltage, 94 sensed voltage, 95 sensed voltage digital signal, 95a sensed voltage digital signal, 95b sensed voltage digital signal, 98 reservoir, 99 low voltage condition, 100 driving device, circuit board, 110 alternator, 120 controller, 130 sensed load, 140 logic device, 200 driving device, 210 full bridge, 212 switch, 214 switch, 216 switch, 218 switch, 220 controller, 230 sense load, 240 logic device, 262 analog-to-digital converter (ADC), 264 ADC, 300 driving device, 362 op-amp comparator, 364 op-amp comparator, 400 driving device, 410 half bridge, 412 switch, 414 switch, 420 controller, 430 sense load, 500 driving device, 510 full bridge, 520 microcontroller unit (MCU), 530 sense load, 700 method, 810a voltage, 810b voltage, 810c voltage, 820a current, 820b current, 820c current, 840 current of piezoelectric device driven by another device, 840a periodic sag, 840b recovery, 850 transition, 850a positive (rising) transition, 850b negative (falling) transition, 852a positive transition, 852b positive transition, 852c positive transition, 854a positive transition, 854b positive transition, 856a positive transition, 856b positive transition, 856c positive transition, 950 Sampling Interval (hours)

Claims

1. 1. An atomizer for a liquid, comprising: a piezoelectric device having a resonant frequency; A circuit including a sense load operatively coupled to the piezoelectric device such that a sense voltage across the sense load has a phase corresponding to a phase of the piezoelectric device, the circuit configured to provide a switching voltage at an operating frequency to drive the piezoelectric device, the circuit configured to iteratively determine whether the sense voltage is in phase or out of phase with respect to the switching voltage and make a corresponding change to the operating frequency, the circuit comprising: (i) increasing the operating frequency by a first predetermined value in response to the sense voltage being in phase with the switching voltage, and decreasing the operating frequency by a second predetermined value in response to the sense voltage being out of phase with the switching voltage; (ii) increasing the operating frequency by a first predetermined value in response to the sense voltage being out of phase with respect to the switching voltage, and decreasing the operating frequency by a second predetermined value in response to the sense voltage being in phase with respect to the switching voltage; (iii) decreasing the operating frequency by a first predetermined value in response to the sense voltage being in phase with the switching voltage, and increasing the operating frequency by a second predetermined value in response to the sense voltage being out of phase with the switching voltage; (iv) decreasing the operating frequency by a first predetermined value in response to the sense voltage being out of phase with respect to the switching voltage, and increasing the operating frequency by a second predetermined value in response to the sense voltage being in phase with respect to the switching voltage; a circuit configured according to any one of The atomizer includes:

2. 2. The atomizer of claim 1, wherein the operating frequency is configured to be close to or within a target frequency band, the target frequency band being a predefined range of frequencies that includes at least the resonant frequency.

3. 3. The atomizer of claim 2, wherein the circuitry is configured to make the corresponding change to the operating frequency periodically according to a sampling frequency such that the operating frequency varies within the target frequency band.

4. The atomizer of claim 3 , wherein the sampling frequency is defined by a selected transition of the switching voltage.

5. The circuit comprises: an alternator coupled to the piezoelectric device, the alternator configured to provide the switching voltage to drive the piezoelectric device; an analog-to-digital converter configured to convert the switching voltage into a switching voltage digital signal; a logic device configured such that the selected transition between two states of the switching voltage digital signal triggers sensing of the sense voltage and the corresponding change to the operating frequency by one of the first predetermined value and the second predetermined value; The atomizer of claim 4 further comprising:

6. 6. The atomizer of claim 5, wherein the alternator comprises a full bridge configured to generate the switching voltage in the form of a square wave.

7. 6. The atomizer of claim 5, wherein the alternator is configured in a push-pull configuration such that the switching voltage is a square wave.

8. 8. The atomizer of claim 7, wherein the sensing load is a resistive element.

9. The circuit comprises: - determining a first occurrence when the operating frequency is within a target frequency band, the target frequency band being a predefined range of frequencies that includes at least one resonant frequency of the piezoelectric device; in response to said initial occurrence, determining whether the sense voltage is in phase or out of phase with respect to the switching voltage; and - repeatedly making a corresponding change to the operating frequency by one of the first predetermined value and the second predetermined value; The atomizer of claim 1 further configured as follows:

10. 10. The atomizer of claim 9, wherein the circuitry is configured to make the corresponding change to the operating frequency such that the operating frequency varies within the target frequency band.

11. 11. The atomizer of claim 10, wherein the corresponding change to the operating frequency occurs at a time corresponding to a selected transition of the switching voltage.

12. 12. The atomizer of claim 11, wherein each of the first predetermined value and the second predetermined value is less than a range of the target frequency band.

13. 13. The atomizer of claim 12, wherein during operation of the atomizer, each of the predetermined first value and the predetermined second value is independent of a difference in value between the operating frequency and either one of an upper limit of the target frequency band and a lower limit of the target frequency band.

14. 13. The atomizer of claim 12, wherein during operation of the atomizer, each of the first predetermined value and the second predetermined value is independent of a difference in value between the operating frequency and at least one of the resonant frequencies.

15. 2. The atomizer of claim 1, wherein the atomizer is configured to atomize a liquid, and wherein the piezoelectric device in operation is configured to transfer energy to the liquid to provide a non-intermittent flow of atomized liquid over an operating period, and wherein the operating frequency varies over the operating period.

Images