Voltage spike protection circuit, protection method and application of wireless power transfer inverter

Abstract

This invention proposes a voltage spike protection circuit, protection method, and application for wireless power transfer inverters, belonging to the field of wireless power transfer technology. It addresses the problems of existing wireless power transfer systems easily generating voltage spikes under special operating conditions, leading to increased device stress, and the lack of voltage spike protection functionality in inverters. The protection circuit includes: a high-frequency differential sampling module, a high-speed comparison module, a physical reset button, an optocoupler isolation module, a high-speed digital controller, and a single-ended drive module. The proposed protection circuit can effectively detect voltage spikes and combines hardware and software triggering to achieve timely protection, ensuring equipment safety. The protection circuit has an implementation path composed of purely analog circuits, with a short overall response time and reliable triggering, filling a functional gap in inverters.

Description

Technical Field

[0001] This invention relates to voltage spike protection circuits, protection methods, and applications for wireless power transfer inverters, belonging to the field of wireless power transfer technology. Background Technology

[0002] Wireless Power Transfer (WPT) systems typically use an inverter to generate high-frequency alternating current, which excites electromagnetic interaction in a coupling mechanism to achieve contactless energy transfer. With advantages of safety and convenience, WPT systems are widely used in electric vehicles, industrial automation, smart mines, and other fields, and are developing towards higher frequencies, higher power, and higher efficiency.

[0003] In wireless power transmission systems, the primary function of high-frequency inverters is to convert direct current (DC) into high-frequency alternating current (AC), thus playing a crucial role in improving transmission power and efficiency. However, inverters face unique challenges in application, such as harsh operating environments involving high frequency, high voltage, high current, and resonant loads. These factors make further increases in inverter power and power density difficult. Existing power electronic devices have limitations in high-frequency applications, such as low withstand voltage and current capabilities at high frequencies, significant derating of withstand voltage and current capabilities with increasing frequency, and the high cost of large-capacity power transistors. These factors restrict performance improvements in wireless power transmission systems. Therefore, how to fully utilize the performance of switching devices while ensuring the stability and reliability of the converter has become a current research focus. This requires designing protection circuits with fast response, high reliability, and strong practicality to ensure that switching devices do not exceed their extreme operating conditions, maximizing their performance while guaranteeing the safe operation of the system.

[0004] The state of the inverter during switching also directly affects its performance. In soft-switching mode, the parasitic capacitance of the switching transistors can be fully charged and discharged, resulting in a smaller di / dt during switching, which helps reduce output voltage spikes and further enhances the performance of the switching transistors. However, as the depth of soft switching increases or when in hard-switching mode, the di / dt during switching increases, leading to larger output voltage spikes. Therefore, in a WPT system, the resonant cavity load is ideally weakly inductive. However, the resonant state of the resonant cavity load is highly sensitive, fluctuating with changes in temperature, relative position, and other factors, causing larger output voltage spikes and potentially leading to overvoltage breakdown of the inverter. Simultaneously, the high-frequency operating environment can cause varying degrees of interference to the low-voltage circuits, increasing the difficulty of protection circuits and further affecting the normal operation of the WPT system, even posing a danger.

[0005] To address these issues, existing technologies typically employ additional series and parallel connections and derating of switching devices to increase system margin and ensure normal operation. To further control costs and fully utilize the performance of switching transistors, protection measures based on inferring peak magnitudes from the inverter's output voltage plateau have emerged. While this method expands the usability of switching transistors to some extent, its sampling circuit suffers from poor waveform reproduction and is prone to losing high-frequency peaks. All these methods reduce the utilization rate of switching transistors to some extent, thereby limiting the increase in inverter power and power density, and hindering the further development of high-power wireless power transfer technology. Summary of the Invention

[0006] This invention addresses the problems of voltage spikes in existing wireless power transfer systems under special operating conditions, which can lead to increased stress on devices and the lack of voltage spike protection in inverters. It proposes a voltage spike protection circuit, protection method, and application for wireless power transfer inverters.

[0007] The technical solution adopted by this invention to solve the above problems is as follows: The wireless power transfer inverter voltage spike protection circuit proposed in this invention includes:

[0008] High-frequency differential sampling module, high-speed comparison module, physical reset button, optocoupler isolation module, high-speed digital controller and single-ended drive module;

[0009] The frequency differential sampling module is used to proportionally convert the inverter's output voltages Vin+ and Vin- into a low-voltage, high-frequency signal V. out The low-voltage high-frequency signal after proportional conversion is output as signal ①.

[0010] The high-speed comparator module has a self-locking function, which uses a comparator to connect signal ① and reference voltage V. set Logical discrimination is performed, and the discrimination information is transmitted to the optocoupler isolation module as signal ②. The discrimination result is transmitted to the high-speed digital controller as signal ⑤. Signal ② includes low-level and high-level states.

[0011] The physical reset button transmits the high-speed comparator module reset information as signal ④ to the high-speed comparator module for reset operation;

[0012] The optocoupler isolation module is used to remove the influence of signal ② on the drive circuit in the single-ended drive module and output signal ③;

[0013] The high-speed digital controller reads the judgment result of the high-speed comparison module by receiving signal ⑤, and transmits signal ⑥ to the high-speed comparison module to control the reset function of the high-speed comparison module after self-locking. At the same time, it transmits signal ⑦ to the single-ended drive module according to the judgment result read to realize the detection and control of the single-ended drive module, ensuring that the information of signal ⑤ is accurately reflected.

[0014] The single-ended drive module controls the switching state of the switching transistor by detecting the state of signal ③, thereby completing circuit protection.

[0015] Preferably, the high-frequency differential sampling module includes resistors R1-R19, capacitors C1-C10, diodes D1-D4, and a first active voltage follower circuit, a second active voltage follower circuit, and a third active voltage follower circuit. The high-speed comparison module is connected to resistor R20.

[0016] A resistor R22 is provided on the connection circuit between the physical reset button and the high-speed digital controller;

[0017] The high-speed digital controller includes resistors R22 and R21, which are connected to the emitter of an NPN transistor and a physical reset button. The base is connected to the DSP via a current-limiting resistor R21 and to a high-speed comparator module via a switch.

[0018] Preferably, resistor R3 is a pull-up resistor, resistor R15 is a pull-down resistor, and resistor R21 is a current-limiting resistor.

[0019] Methods for voltage spike protection in wireless power transfer inverters include:

[0020] Step 1: Input the inverter output voltages Vin+ and Vin- into the high-frequency differential sampling module to divide them into Vin1 and Vin2. Vin1 and Vin2 are then combined into a third active voltage follower circuit after passing through the first and second active voltage follower circuits respectively. Based on the target protection value and the low-voltage power supply range, the inverter output voltage is proportionally divided to determine V. out1 V out1 As signal ①, it is transmitted to the high-speed comparison module;

[0021] Step 2: Adjust the capacitors C1-C10 of the passive component voltage divider according to the voltage division ratio and the frequency f of the inverter output voltage spike to keep the waveform of the inverter internal circuit consistent before and after sampling.

[0022] Step 3: Adjust resistors R3 and R15 and capacitors C2-C7 to eliminate the differences in the chips of the active voltage follower circuit provided by the DC power supply;

[0023] Step 4: Based on the required time, select the appropriate high-speed comparator module with self-locking power supply, wherein the input voltage of the high-speed comparator meets the following requirements.

[0024] Step 5: Set the reference voltage V set The high-speed comparison module compares signal ① with reference voltage V. setPerform logical discrimination, and transmit the discrimination information as signal ② to the optocoupler isolation module, and transmit the discrimination result as signal ⑤ to the high-speed digital controller.

[0025] Step 6: Connect the high-speed digital controller and the high-speed comparator module through a switch, and connect the emitter of the NPN transistor and the physical reset button. Connect the base to the DSP through the current-limiting resistor R21. Set the resistor R20 and the hysteresis time by looking up the table.

[0026] Step 7: The physical reset button transmits signal ④ to reset the high-speed comparison module after self-locking. The high-speed digital controller transmits signal ⑦ to the single-ended drive module according to the judgment result of reading the physical reset button to realize the detection and control of the single-ended drive module.

[0027] Step 8: Isolate signals ② and ③ using an optocoupler isolation module, and output signal ③ to drive a single-ended driver module to complete circuit protection;

[0028] V out1 The calculation formula is:

[0029]

[0030] In formula (1), passive device voltage divider specifically refers to the sum of the resistors in the passive device voltage divider module;

[0031] The formula for calculating the reference voltage is:

[0032]

[0033] Applications of voltage spike protection circuits in wireless power transfer inverters include:

[0034] The DC power supply, inverter, transmitting coil, receiving coil, rectifier, DC converter, and load are connected in sequence.

[0035] The DC power supply is used to provide active voltage to the inverter;

[0036] The inverter uses a voltage spike protection circuit to perform voltage inversion, converting active current into alternating current. When the spike in the inverter's output voltage exceeds the limit, the internal circuit is triggered to switch the switching transistor, thus completing the circuit protection.

[0037] The AC power is transmitted through the transmitting coil after passing through the compensation topology, and the receiving coil receives the compensated AC power, which is then received by the DC power unit through the compensation topology.

[0038] The DC converter converts the received AC power into AC power.

[0039] A DC-DC converter is used to convert high-voltage AC power into low-voltage AC power and transmit it to the load.

[0040] The beneficial effects of this invention are:

[0041] 1. The voltage spike protection circuit proposed in this invention can effectively detect voltage spikes and combines hardware triggering and software triggering to achieve timely protection and ensure equipment safety. At the same time, the voltage divider circuit in this invention has high fidelity at high frequencies and the waveform is not distorted. The protection circuit has an implementation path composed of pure analog circuits, with short overall response time and reliable triggering, filling the gap in inverter functions.

[0042] 2. Based on the accurate sampling and fast response of the protection circuit in this invention, the switching frequency and voltage and current levels can be improved, which is conducive to further improving the power level, power density and system efficiency of wireless power transmission systems.

[0043] 3. This invention is based on analog circuit detection, and combines hardware triggering with software triggering for composite protection, which has higher reliability.

[0044] 4. The voltage spike protection method of this invention, based on system indicators and device selection, is feasible and universal. Attached Figure Description

[0045] Figure 1 The present invention provides an inverter application circuit diagram with voltage spike protection function;

[0046] Figure 2 The present invention provides a circuit diagram for voltage spike protection of a wireless power transfer inverter.

[0047] Figure 3 A schematic flowchart of the wireless power transfer inverter voltage spike protection method provided by the present invention;

[0048] Figure 4 A specific internal circuit diagram of the inverter provided for this invention;

[0049] Figure 5 The experimental test waveform diagram of the high-frequency sampling module circuit provided by this invention is shown below. Figure 5 In the image, (a) shows the test waveform, and (b) shows a detailed view of the test waveform.

[0050] Figure 6 The protection circuit trigger waveform diagram provided by the present invention. Detailed Implementation

[0051] Combination Figures 1-6 This embodiment will be described as follows: Figure 1 and Figure 2As shown, the structure of the wireless power transfer inverter voltage spike protection circuit described in this embodiment includes: a high-frequency differential sampling module, a high-speed comparison module, a physical reset button, an optocoupler isolation module, a high-speed digital controller, and a single-ended drive module;

[0052] The high-frequency differential sampling module is used to proportionally convert the inverter's output voltages Vin+ and Vin- into a low-voltage, high-frequency signal V. out The low-voltage high-frequency signal after proportional conversion is output as signal ①.

[0053] The high-speed comparator module has a self-locking function, which uses a comparator to connect signal ① and reference voltage V. set Logical discrimination is performed, and the discrimination information is transmitted to the optocoupler isolation module as signal ②. The discrimination result is transmitted to the high-speed digital controller as signal ⑤. Signal ② includes low-level and high-level states.

[0054] The physical reset button transmits the high-speed comparator module reset information as signal ④ to the high-speed comparator module for reset operation;

[0055] The optocoupler isolation module is used to remove the influence of signal ② on the drive circuit in the single-ended drive module and output signal ③;

[0056] The high-speed digital controller reads the judgment result of the high-speed comparison module by receiving signal ⑤, and transmits signal ⑥ to the high-speed comparison module to control the reset function of the high-speed comparison module after self-locking. At the same time, it transmits signal ⑦ to the single-ended drive module according to the judgment result read to realize the detection and control of the single-ended drive module, ensuring that the information of signal ⑤ is accurately reflected.

[0057] The single-ended drive module controls the switching state of the switching transistor by detecting the state of signal ③, thereby completing circuit protection.

[0058] The AC power is transmitted through the transmitting coil after passing through the compensation topology, and the receiving coil receives the compensated AC power, which is then received by the DC power unit through the compensation topology.

[0059] The DC converter converts the received AC power into AC power.

[0060] A DC-DC converter is used to convert high-voltage AC power into low-voltage AC power and transmit it to the load.

[0061] The high-frequency differential sampling module includes resistors R1-R19, capacitors C1-C10, diodes D1-D4, and a first active voltage follower circuit, a second active voltage follower circuit, and a third active voltage follower circuit. The high-speed comparison module is connected to resistor R20, where resistor R3 is a pull-up resistor and resistor R15 is a pull-down resistor.

[0062] A resistor R22 is provided on the connection circuit between the physical reset button and the high-speed digital controller;

[0063] The high-speed digital controller includes resistor R22 and current-limiting resistor R21, which are connected to the emitter of an NPN transistor and a physical reset button. The base is connected to the DSP through current-limiting resistor R21 and connected to a high-speed comparator module through a switch.

[0064] Furthermore, the specific application of the wireless power transfer inverter voltage spike protection circuit designed in this embodiment in the circuit is as follows: Figure 1 As shown, the application circuit includes a DC power supply, an inverter, a transmitting coil, a receiving coil, a rectifier, a DC converter, and a load connected in sequence.

[0065] The DC power supply is used to provide the active voltage for the inverter;

[0066] Inverters are used to perform voltage inversion, converting active current into alternating current. When the peak of the inverter's output voltage exceeds the limit, the internal circuit is triggered to switch the switching transistors, thus completing circuit protection.

[0067] The AC power is transmitted through the transmitting coil after passing through the compensation topology, and the receiving coil receives the compensated AC power, which is then received by the DC power unit through the compensation topology.

[0068] The DC converter converts the received AC power into AC power.

[0069] A DC-DC converter is used to convert high-voltage AC power into low-voltage AC power and transmit it to the load.

[0070] In summary, this implementation method completes the circuit topology. The following section will describe how to use a wireless power transfer inverter voltage spike protection method to set parameters for the internal circuit components of the inverter. The specific steps are as follows: Figure 3 As shown, it includes:

[0071] Step 1: Input the inverter output voltages Vin+ and Vin- into the high-frequency differential sampling module to divide them into Vin1 and Vin2. Vin1 and Vin2 are then combined into a third active voltage follower circuit after passing through the first and second active voltage follower circuits respectively. Based on the target protection value and the low-voltage power supply range, the inverter output voltage is proportionally divided to determine V. out1 , V out1 As signal ①, it is transmitted to the high-speed comparison module. Here, the passive component voltage divider specifically refers to the sum of the resistors in the passive component voltage divider module.

[0072] Step 2: Adjust the capacitors C1-C10 of the passive component voltage divider according to the voltage division ratio and the frequency f of the inverter output voltage spike to keep the waveform of the inverter internal circuit consistent before and after sampling.

[0073] Step 3: Adjust resistors R3 and R15 and capacitors C2-C7 to eliminate the differences in the chips of the active voltage follower circuit provided by the DC power supply;

[0074] Step 4: Based on the required time, select the appropriate high-speed comparator module with self-locking power supply, wherein the input voltage of the high-speed comparator meets the following requirements.

[0075] Step 5: Set the reference voltage V set， The high-speed comparison module compares signal ① with reference voltage V. set Perform logical discrimination, and transmit the discrimination information as signal ② to the optocoupler isolation module, and transmit the discrimination result as signal ⑤ to the high-speed digital controller.

[0076] Step 6: Connect the high-speed digital controller and the high-speed comparator module through a switch, and connect the emitter of the NPN transistor and the physical reset button. Connect the base to the DSP through the current-limiting resistor R21. Set the resistor R20 and the hysteresis time by looking up the table.

[0077] Step 7: The physical reset button transmits signal ④ to reset the high-speed comparison module after self-locking. The high-speed digital controller transmits signal ⑦ to the single-ended drive module according to the judgment result of reading the physical reset button to realize the detection and control of the single-ended drive module.

[0078] Step 8: Isolate signals ② and ③ using an optocoupler isolation module, and output signal ③ to drive a single-ended driver module to complete circuit protection;

[0079] Based on the above, this implementation method constructs as follows: Figure 4 The specific inverter voltage spike protection circuit shown is illustrated in Table 1, where the component parameters of the high-frequency differential sampling module are listed.

[0080] Table 1

[0081]

[0082] The internal component parameters of the high-speed comparator module, physical reset button, optocoupler isolation module, high-speed digital controller, and single-ended drive module are shown in Table 2.

[0083] Table 2

[0084]

[0085] To verify the technical effect of the present invention, this embodiment performs simulation verification on the high-frequency sampling module circuit. The simulation verification results of the high-frequency sampling module circuit are as follows: Figure 5 (a) and Figure 5As shown in (b) Figure 5 (a) and Figure 5 (b) Channel 1 shows the voltages at the Vin1 and Vin2 ports, and Channel 2 shows the voltage at the Vout1 port. The proportional circuit is 2 / 1000, and the inverter protection circuit trigger waveform is as follows. Figure 6 As shown in the diagram, channel 1 represents the inverter output voltage, channel 2 represents the inverter output current, and channel 3 represents the operating level, which changes from low to high during operation. It is clearly visible in the diagram that when the spike exceeds a certain value, the circuit immediately triggers, completing the protection process.

[0086] In summary, the voltage spike protection circuit proposed in this invention can effectively detect voltage spikes and combines hardware and software triggering to achieve timely protection and ensure equipment safety. Furthermore, the voltage divider circuit in this invention exhibits high fidelity at high frequencies with undistorted waveforms. The protection circuit has an implementation path composed of purely analog circuits, resulting in a short overall response time and reliable triggering, filling a gap in inverter functionality. Moreover, the protection circuit in this invention can achieve accurate sampling and rapid response, which can improve switching frequency and voltage / current levels, thus contributing to further improvements in the power level, power density, and system efficiency of wireless power transmission systems.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A voltage spike protection circuit for a wireless power transfer inverter, characterized in that, The voltage spike protection circuit for the wireless power transfer inverter includes: a high-frequency differential sampling module, a high-speed comparison module, a physical reset button, an optocoupler isolation module, a high-speed digital controller, and a single-ended drive module; The high-frequency differential sampling module is used to convert the inverter's output voltages Vin+ and Vin- proportionally into a low-voltage high-frequency signal V. out The low-voltage high-frequency signal after proportional conversion is output as signal ①. The high-speed comparison module has a self-locking function, which uses a comparator to connect signal ① and reference voltage V. set Logical discrimination is performed, and the discrimination information is transmitted to the optocoupler isolation module as signal ②. The discrimination result is transmitted to the high-speed digital controller as signal ⑤. Signal ② includes low-level and high-level states. The physical reset button transmits the high-speed comparison module reset information as signal ④ to the high-speed comparison module for reset operation; The optocoupler isolation module is used to remove the influence of signal ② on the drive circuit in the single-ended drive module and output signal ③; The high-speed digital controller reads the discrimination result of the high-speed comparison module by receiving signal ⑤, and transmits signal ⑥ to the high-speed comparison module to control the reset function of the high-speed comparison module after self-locking. At the same time, it transmits signal ⑦ to the single-ended drive module according to the read discrimination result to realize the detection and control of the single-ended drive module, ensuring that the information of signal ⑤ is accurately reflected. The single-ended drive module controls the switching state of the switching transistor by detecting the state of signal ③, thereby completing circuit protection.

2. The voltage spike protection circuit for a wireless power transfer inverter according to claim 1, characterized in that, The high-frequency differential sampling module includes resistors R1-R19, capacitors C1-C10, diodes D1-D4, and a first active voltage follower circuit, a second active voltage follower circuit, and a third active voltage follower circuit. The high-speed comparison module is connected to resistor R20. A resistor R22 is provided on the connection circuit between the physical reset button and the high-speed digital controller; The high-speed digital controller includes resistors R22 and R21, which are connected to the emitter of an NPN transistor and a physical reset button. The base is connected to the DSP via a current-limiting resistor R21 and to a high-speed comparator module via a switch.

3. The voltage spike protection circuit for a wireless power transfer inverter according to claim 2, characterized in that, Resistor R3 is a pull-up resistor, resistor R15 is a pull-down resistor, and resistor R21 is a current-limiting resistor.

4. A method for voltage spike protection of a wireless power transfer inverter, applied to the voltage spike protection circuit of the wireless power transfer inverter as described in any one of claims 1-3, characterized in that, include: Step 1: Input the inverter output voltages Vin+ and Vin- into the high-frequency differential sampling module to divide them into Vin1 and Vin2. Vin1 and Vin2 are then combined into a third active voltage follower circuit after passing through the first and second active voltage follower circuits respectively. Based on the target protection value and the low-voltage power supply range, the inverter output voltage is proportionally divided to determine V. out1 V out1 As signal ①, it is transmitted to the high-speed comparison module; Step 2: Adjust the capacitors C1-C10 of the passive component voltage divider according to the voltage division ratio and the frequency f of the inverter output voltage spike to keep the waveform of the inverter internal circuit consistent before and after sampling. Step 3: Adjust resistors R3 and R15 and capacitors C2-C7 to eliminate the differences in the chips of the active voltage follower circuit provided by the DC power supply; Step 4: Based on the required time, select the appropriate high-speed comparator module with self-locking power supply, wherein the input voltage of the high-speed comparator meets the following requirements. ; Step 5: Set the reference voltage V set The high-speed comparison module compares signal ① with reference voltage V. set Logical discrimination is performed, and the discrimination information is transmitted as signal ② to the optocoupler isolation module. The discrimination result is transmitted as signal ⑤ to the high-speed digital controller. Step 6: Connect the high-speed digital controller and the high-speed comparator module through a switch, and connect the emitter of the NPN transistor and the physical reset button. Connect the base to the DSP through the current-limiting resistor R21. Set the resistor R20 and the hysteresis time by looking up the table. Step 7: The physical reset button transmits signal ④ to reset the high-speed comparison module after self-locking. The high-speed digital controller transmits signal ⑦ to the single-ended drive module according to the judgment result of reading the physical reset button to realize the detection and control of the single-ended drive module. Step 8: Isolate signals ② and ③ using an optocoupler isolation module, and output signal ③ to drive a single-ended driver module to complete circuit protection; V out1 The calculation formula is: （1）； In formula (1), passive device voltage divider specifically refers to the sum of the resistors in the passive device voltage divider module; The formula for calculating the reference voltage is: （2）。 5. Application of a voltage spike protection circuit for a wireless power transfer inverter, applied to the voltage spike protection circuit for a wireless power transfer inverter as described in any one of claims 1-3, characterized in that, include: The DC power supply, inverter, transmitting coil, receiving coil, rectifier, DC converter, and load are connected in sequence. The DC power supply is used to provide active voltage to the inverter; The inverter uses a voltage spike protection circuit to perform voltage inversion, converting active current into alternating current. When the spike in the inverter's output voltage exceeds the limit, the internal circuit is triggered to switch the switching transistor, thus completing the circuit protection. The AC power is transmitted through the transmitting coil after passing through the compensation topology, and the receiving coil receives the compensated AC power, which is then received by the DC power unit through the compensation topology. The DC converter converts the received AC power into AC power. A DC-DC converter is used to convert high-voltage AC power into low-voltage AC power and transmit it to the load.

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