Self-energy-taking power device driving power supply circuit based on piezoresistor

Abstract

The invention belongs to the technical field of power semiconductor driving, and discloses a power device driving power supply circuit based on a piezoresistor, and the circuit comprises an MOV1 and an MOV2 which are connected in series between the high-voltage end of a power device and a driving ground Vdriving gnd; one end of the energy storage capacitor C1 is connected with the emitting electrode of the Q1, and the other end of the energy storage capacitor C1 is connected with the driving ground Vdriver gnd; the base electrode is connected with the common node through the R1, the collector electrode is connected with the common node of the MOV1-MOV2, and the emitter electrode is connected with the Q1 of the C1; a base electrode of the Q2 is connected with the C1 through an R2 and an R3, and an emitting electrode of the Q2 is connected with a driving ground Vdriver gnd through a voltage stabilizing diode D1; a gate driver IC using C1 as a unique power source; and the driving ground Vdriving gnd is not electrically connected with the primary side ground. VMOV1 is set to be smaller than Vds, VMOV1 + VMOV2 is set to be larger than Vds, after the voltage of C1 reaches a set value, Q2 is switched on, Q1 is switched off, and self-energy-taking and self-switching-off are achieved; the circuit omits an isolation power supply and is simple in structure. In a half-bridge, full-bridge or multi-level topology, each bridge arm self-power-taking unit is independently configured, the number of system-level devices and the number of common-mode paths are reduced at the same time, and the reliability is improved.

Description

Technical Field

[0001] This invention belongs to, but is not limited to, the field of power semiconductor driving technology, and particularly relates to a self-powered power device driving power supply circuit based on a varistor. Background Technology

[0002] The gate power supply of high-voltage power devices faces a triple coupling contradiction of "isolation-power supply-protection": traditional resistor power supply generates Joule heat due to the continuous conduction of the high-voltage arm, and the resistance value drifts or even burns out at high temperatures, and it has no ability to suppress surges; the secondary power supply of traditional isolated DC-DC solutions cannot absorb bus surges itself, and additional TVS / MOV (Transient Voltage Suppressor / Metal Oxide Varistor) needs to be configured, which is large in size, has high parasitic capacitance, and the dv / dt common mode current is directly coupled to the signal side, which is prone to false triggering; a single MOV is only used for parallel clamping, and the energy is wasted, which can neither be converted into driving energy nor provide electrical isolation.

[0003] While the CN204634101U employs multiple varistors in a distributed layout in its 220V AC LED driver to reduce differential-mode and common-mode surges, its topology operates in the low-voltage AC domain, lacking energy storage and a "fully charged self-stop" mechanism. When the bus voltage rises to 600V DC and the load becomes a power semiconductor, the defects of continuous leakage current, lack of isolation, and lack of power extraction are amplified exponentially and cannot be directly transferred. Therefore, existing technologies have failed to efficiently and reliably address the three interrelated yet contradictory core requirements of high-voltage isolation, continuous power extraction, and surge suppression. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a self-powered power device driving power supply circuit based on a varistor.

[0005] This invention is implemented as follows: the purpose of this invention is to provide a self-powered drive circuit based on a varistor, using only... Figure 2 Figure 3 The component shown can complete energy acquisition and automatic charging termination on the high-voltage side, and naturally cut off the common-mode interference path.

[0006] The core concept of this invention is:

[0007] Utilizing the nonlinear volt-ampere characteristics of MOV1 and MOV2, we set VMOV1 < Vds and VMOV1 + VMOV2 > Vds.

[0008] With the emitter of Q1 as the charging outlet, C1 is charged directly. The voltage of C1 is mapped to the base of Q2 by the voltage divider of R2 and R3. When the voltage divider value is higher than the reference potential of the emitter of Q2, Q2 is turned on, pulling down the base of Q1 and the charging stops automatically.

[0009] When applied to a half-bridge topology, the core principle lies in using varistor-based power harvesting modules symmetrically arranged in the upper and lower bridge arms to achieve self-powered operation via the voltage difference across the power devices. Its operating logic is divided into single-transistor charging logic and half-bridge startup control logic. The single-transistor self-powered charging logic has already been explained. The half-bridge startup control logic utilizes the symmetrical structure of the half-bridge circuit and a "non-synchronous cutoff" startup mechanism.

[0010] Initial series charging: At the moment the bus voltage is applied, the upper and lower transistors are in the off state, and the current flows through the series path formed by the two units to replenish the charge of the upper and lower capacitors.

[0011] Asynchronous Cutoff: Due to the inherent differences in component parameters, the two capacitors will not be fully charged synchronously. The capacitor that is fully charged first will trigger its internal cutoff mechanism, causing the entire series path to be interrupted. At this time, the control system drives the power transistor on the first-charged side to turn on, forcibly pulling the midpoint of the half-bridge to a high potential (DC+) or a low potential (DC-), so that the uncharged cells on the other side are momentarily subjected to a voltage close to the full voltage of the DC bus, thereby quickly replenishing the drive energy.

[0012] To achieve the above objectives, the present invention adopts the following technical solution.

[0013] The first varistor MOV1 has its first terminal connected to the high-voltage terminal of the power device.

[0014] The second varistor MOV2 has its first end connected to the second end of MOV1, and its second end connected to the drive ground Vdrivergnd.

[0015] One end of the energy storage capacitor C1 is connected to the emitter of Q1, and the other end is connected to the drive ground Vdrivergnd;

[0016] The first NPN transistor Q1 has its collector connected to the common node of MOV1-MOV2, its emitter connected to C1, and its base connected to the common node via R1.

[0017] The emitter of the second NPN transistor Q2 is connected to the driver ground Vdrivergnd via the Zener diode D1, and the collector is connected to the base of Q1. The base is connected to C1 via the series R2R3 network.

[0018] Zener diode D1 has its cathode connected to the emitter of Q2 and its anode connected to the drive ground Vdrivergnd, serving as a fixed reference potential for the emitter of Q2.

[0019] The current-limiting resistor R4 is connected at one end to the positive terminal of C1 and at the other end to the cathode of D1.

[0020] The gate driver IC has its power supply terminal connected to C1, its ground terminal connected to the drive ground Vdrivergnd, and its output terminal connected to the gate of the power device.

[0021] The driving ground Vdrivergnd has no electrical connection to the primary ground.

[0022] The stable voltage value of C1 can be changed by adjusting the voltage division ratio of R2 and R3 and the voltage regulation value of the Zener diode.

[0023] When used in a half-bridge topology, this circuit includes an upper bridge arm power supply unit located at both ends of the upper bridge arm power transistor, and a lower bridge arm power supply unit located at both ends of the lower bridge arm power transistor. The two units have the same structure, and the circuit connection method is the same as the single-transistor connection method described above. The charging and startup control logic of the half-bridge, namely "series start-up - asynchronous cut-off - switch-assisted full charge," differs from that of the single-transistor topology.

[0024] 1. Series Start-up Stage: Upon initial power-up of the DC bus Vdc, both the upper and lower transistors are turned off. Current flows along the series circuit: DC+ → MOV1H → Q1H → C1H → midpoint of the half-bridge → MOV1L → Q1L → C1L → DC-. C1H and C1L begin charging simultaneously. 2. Asynchronous Cut-off Stage: Due to component tolerances, the two capacitors will not charge synchronously. When either capacitor (e.g., the upper bridge arm) reaches the set value (e.g., 15V) first, the voltage divider R2H and R3H causes Q2H to conduct and pull down the base of Q1H, causing Q1H to cut off. The series circuit is interrupted, and the other capacitor stops charging. 3. Switch-Assisted Charging Stage: A control signal is sent to the upper transistor to control its switch. When the upper transistor is turned on, the midpoint of the half-bridge is pulled to DC+. The uncharged power supply unit is directly connected across the bus Vdc, resuming charging until C1L's energy is fully built up.

[0025] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0026] First, this invention eliminates the secondary-side isolation power supply structure commonly used in traditional half-bridge drive circuits. It eliminates the need for isolation transformers, optocouplers, or dedicated isolated DC / DC modules, relying solely on the voltage conditions of the half-bridge itself to establish the drive power supply. The overall number of components is minimal, and the circuit structure is highly simplified, which helps reduce system cost, size, and improve engineering reliability. Furthermore, MOV1 and MOV2 are not merely used as conventional surge absorption components; they also participate in the power supply extraction process. During startup, they provide energy to the self-powered circuit, and during steady-state operation, they effectively clamp the bus surge voltage, achieving multi-functional integration. Simultaneously, the coordinated operation of Q1 and Q2 constitutes a "self-stop" mechanism without additional power consumption. Once the drive power supply voltage reaches a set stable state, it automatically cuts off the startup power extraction path, avoiding unnecessary energy loss and voltage overshoot, thereby improving overall system efficiency.

[0027] Secondly, from the perspective of system anti-interference performance, this invention naturally cuts off the propagation path of common-mode current by eliminating the direct electrical connection between the drive ground VdriverGND and the primary ground. Even in a high dv / dt half-bridge switching environment, it can effectively suppress the impact of common-mode interference on the drive circuit, significantly improve the stability and noise immunity of the drive signal, without the need to introduce any additional isolation devices.

[0028] The technical solution of this invention fills a gap in the existing technology in terms of functional combination. By combining the varistor overvoltage protection and startup power harvesting function into one, the varistor device can simultaneously perform the function of 600V bus overvoltage protection and serve as the sole energy harvesting branch during the startup phase. This achieves an integrated design of "overvoltage protection + startup power harvesting" without the need for an external TVS, auxiliary resistor, or startup power supply. Simultaneously, in the half-bridge structure, self-powering paths consisting of MOVH–MOVL and Q1H–Q2H, C1H–C1L are constructed for the upper and lower bridge arms respectively. This allows the circuit to complete a three-stage self-powering process of "series startup, asynchronous cutoff, and switch-assisted full charging" without adding any new functional components, demonstrating a high degree of structural self-consistency.

[0029] Finally, this invention overcomes long-standing technical biases in the field. On the one hand, addressing the traditional perception that "varistors can only be connected in parallel for clamping and not for energy extraction," this invention, through a reasonable voltage relationship design, effectively converts the energy released during clamping into driving power energy, achieving high-voltage self-powering without adding any components. On the other hand, addressing the inherent notion that "high-voltage driving must rely on isolated power supplies," this invention, through an electrical isolation layout between the driving ground and the primary ground, fundamentally cuts off the common-mode coupling path, achieving safe and reliable high-voltage driving without the need for isolation transformers or optocouplers, demonstrating significant inventiveness and engineering application value. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the traditional drive power supply structure and common-mode current path; a: traditional scheme; b: self-powered scheme;

[0031] Figure 2 Schematic diagram of the single-transistor circuit of this invention;

[0032] Figure 3 The schematic diagram of the half-bridge circuit of this invention.

[0033] Figure 4 The simulation waveforms of the self-powered startup and steady-state process of the half-bridge circuit are shown.

[0034] Figure 5 The simulation waveform diagram shows the dynamic charging and discharging characteristics of the output voltage of the half-bridge self-powered circuit. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] This invention provides a self-powered power device driving circuit based on a varistor, characterized in that the circuit includes:

[0037] The first varistor MOV1 has its first terminal connected to the positive DC bus DC+.

[0038] The second metal oxide varistor MOV2, whose first end is connected to the second end of the first metal oxide varistor MOV1, and whose second end is connected to the drive ground Vdrivergnd; the first NPN transistor Q1, whose collector is connected to the common node of the first metal oxide varistor MOV1 and the second metal oxide varistor MOV2, whose emitter is connected to the positive electrode end of the energy storage capacitor C1, and whose base is connected to the common node of the first metal oxide varistor MOV1 and the second metal oxide varistor MOV2 via the first resistor R1; the second NPN transistor Q2, whose collector is connected to the base of the first NPN transistor Q1, whose emitter is connected to the cathode of the zener diode D1, and whose base is connected to the common voltage dividing point of the second resistor R2 and the third resistor R3; the voltage dividing resistor network is composed of the second resistor R2 and the third resistor R3 in series and is connected in parallel across the energy storage capacitor C1; the energy storage capacitor C1, whose negative electrode is connected to the drive ground Vdrivergnd; the zener diode D1, whose anode is connected to the drive ground VdriverHgnd; the current limiting resistor R4, one end of which is connected to the positive electrode of the energy storage capacitor C1 and the other end of which is connected to the cathode of the zener diode D1;

[0039] Among them, the varistor voltage relationship is set as VMOV1 < Vds and VMOV1 + VMOV2 > Vds; at the initial stage, the voltage of C1 is zero, the base potential of Q1 is higher than its emitter potential and it conducts, the equivalent resistance of MOV1 decreases, and C1 is charged through Q1; when the voltage of C1 rises to the set value, the voltage division of R2 and R3 makes the base potential of Q2 higher than its emitter reference potential, Q2 conducts and pulls down the base of Q1, Q1 cuts off, and the charging stops, and the voltage of C1 stabilizes at the adjustable drive voltage value.

[0040] Figure 1 Used to compare the structural differences and common-mode interference paths between the traditional isolated power supply and the self-powered scheme of the present invention in high-voltage SiC / GaN applications.

[0041] a (traditional scheme)

[0042] The primary control circuit supplies power to the secondary driver through an optocoupler or an isolated DC-DC module; there is a parasitic capacitance between the secondary drive ground (PGND) and the primary ground (AGND). When the power device switches at high speed, an extremely high dv / dt forms a common-mode current through the parasitic capacitance, which is directly coupled to the primary control side, causing EMI, signal mis-triggering, and stress problems of the isolation device; in addition, the traditional isolated power supply itself cannot absorb the bus surge, and an additional parallel TVS / MOV is required, resulting in a complex drive power supply path, large volume, and high failure rate.

[0043] b (self-powered scheme)

[0044] Adopt a drive self-powered + optical isolation architecture to completely disconnect the drive ground Vdrivergnd from the primary ground and cut off Figure 1The common-mode circuit shown in diagram a enables high-voltage side self-sufficiency power supply without isolation power supply or additional protection devices.

[0045] Operating conditions and core parameter settings

[0046] The high-voltage bus voltage HV = 600VDC; the energy storage capacitor C1 is a low-ESR ceramic capacitor with a capacitance of 1μF and an ESR ≤ 10mΩ; the Zener diode reference is 1.3V; the pull-up resistor R1 = 10kΩ; the SiC MOSFET model is GC3M0075120D.

[0047] Single-tube MOV selection analysis and parameter verification

[0048] Varistors MOV1 and MOV2 (model 07D221K and 561K combination)

[0049] Key parameters: MOV1 (221K) varistor voltage 220V, MOV2 (561K) varistor voltage 560V; total varistor voltage after series connection 780V, maximum clamping voltage approximately 1100V, leakage current <5μA (25℃, 80% of rated voltage).

[0050] Selection criteria: The 600V bus is connected in series for voltage division. MOV1 bears about 200V and MOV2 bears about 400V, both of which are lower than their respective maximum clamping voltages. The normal resistance is high, and the series clamping voltage during surges is 1100V, which is lower than the 1200V withstand voltage of the SiCMOSFET, and can safely absorb transient overvoltages on the bus.

[0051] Core functions: series voltage divider for energy extraction, charging C1 during startup, low-resistance discharge during surges, and automatic exit after protection is completed.

[0052] Energy balance analysis

[0053] Single switching energy: The SiC MOSFET model is GC3M0075120D, with a gate charge of 54nC and E_switch=54nC×15V=0.81μJ.

[0054] C1 can release energy: allowing a drop of 1V, E_cap=0.5×1μF×(15²-14²)=14.5μJ.

[0055] Number of consecutive switching cycles: N = 14.5 μJ / 0.81 μJ ≈ 18 times.

[0056] Conclusion: At a switching frequency of 10kHz, C1 can maintain continuous switching for 1.8ms; the MOV leakage current intermittently replenishes energy, and the high impedance rests most of the time, thus extending its lifespan.

[0057] Charging process analysis

[0058] Initial stage: HV rises from 0V to 600V, the high-resistance leakage current of MOV1 charges C1 through the emitter of Q1, and V_C1 gradually increases.

[0059] Threshold triggering stage: V_C1 rises, and the voltage division of R2 and R3 causes the base potential of Q2 to rise. When the difference between Q2 and the Zener diode reaches 0.7V, Q2 turns on.

[0060] During the charging cutoff phase: After Q2 is turned on, the base of Q1 is pulled down, Q1 is turned off, and the voltage of C1 stabilizes at the set value of 15V.

[0061] During steady-state power supply: C1 suppresses ripple with low ESR and outputs a stable 15V voltage to the IC.

[0062] Bridge-type MOV Selection Analysis and Parameter Verification

[0063] For MOV1L / 1H, select 221K; for MOV2L / 2H, select 561K.

[0064] Selection criteria: 600V busbar series voltage division.

[0065] VMOV1H+VMOV1L=220V+220V=440V<600V,

[0066] VMOV1H+VMOV2H=220V+560V=780V>600V,

[0067] VMOV1L + VMOV2L = 220V + 560V = 780V > 600V (Satisfied)

[0068] Startup control logic analysis:

[0069] 1. Series start-up stage: When the DC bus Vdc is initially powered on, both the upper and lower tubes are turned off. The current flows along the series circuit DC+→MOV1H→Q1H→C1H→midpoint of the half bridge→MOV1L→Q1L→C1L→DC-. C1H and C1L start charging simultaneously.

[0070] 2. Asynchronous cutoff stage: Due to component tolerances, the two capacitors will not be fully charged synchronously; when the voltage of either channel (such as the upper bridge arm) reaches the set value (such as 15V) first, the voltage divider of R2H and R3H turns on Q2H and pulls down the base of Q1H, Q1H is cut off, the series circuit is interrupted, and the other channel stops charging.

[0071] 3. Switch-assisted full charge stage: The control signal is sent to the upper tube to control its switch. When the upper tube is turned on, the midpoint of the half bridge is pulled to DC+. The power supply unit on the uncharged side is directly connected to the bus Vdc to resume charging until the C1L energy is established.

[0072] In half-bridge, full-bridge, or multi-level topologies, each power device is independently configured with a power supply unit consisting of MOV1-MOV2, C1, Zener diode, IC, Zener diode, and R1, achieving system-level common-mode rejection and structural simplification.

[0073] Example 1: Varistor Self-Powered Driven Power Supply Circuit with Single-Transistor Structure

[0074] In this embodiment, the positive terminal of the DC bus is connected to the drive power supply unit via a first varistor and a second varistor connected in series, with their common node serving as the self-powered node. The initial voltage of the energy storage capacitor is zero. The control terminal of the first transistor is connected to this self-powered node via a pull-up resistor, forming a charging circuit with the energy storage capacitor. Upon power-up, due to the low voltage of the energy storage capacitor, the first transistor is in a conducting state, and the self-powered node charges the energy storage capacitor through the transistor. When the voltage of the energy storage capacitor rises to a preset value, the voltage detection and feedback unit outputs a control signal, causing the second transistor to conduct and pull down the potential of the control terminal of the first transistor, turning off the first transistor and automatically disconnecting the charging circuit. This process requires no external auxiliary power supply, achieving a synergistic effect of self-powered operation and self-regulation based on the nonlinear characteristics of the varistor.

[0075] Example 2: Self-powered supply method with adjustable drive voltage

[0076] Building upon Example 1, this example modifies the ratio of the two voltage-dividing resistors in the voltage divider detection unit and adjusts the voltage regulation threshold of the voltage regulator to allow the stable voltage of the energy storage capacitor to vary between different set values. The voltage detection and feedback unit still directly acts on the control terminal of the first transistor, ensuring reliable cutoff control under different set voltages. This example demonstrates that the adjustment of the driving voltage is not achieved by adding an independent voltage regulator chip or auxiliary power supply module, but rather by relying on the existing detection and feedback path, reflecting the technological advancements brought about by structural simplification and functional reuse.

[0077] Example 3: Coordination of piezoresistive clamping and energy harvesting under high pressure conditions

[0078] In this embodiment, the clamping voltage of the first varistor is selected to be lower than the drain-source withstand voltage of the power device. The total clamping voltage of the first and second varistors connected in series is higher than the highest surge voltage that may occur on the DC bus. During normal operation, the varistor is in a high-resistance state, providing only the small current required for power extraction. When a transient overvoltage occurs on the bus, the series-connected varistors enter the clamping region together, limiting the node voltage amplitude. This configuration enables the power extraction path to simultaneously possess both surge suppression and energy harvesting functions, avoiding the structural redundancy caused by the independent operation of surge protection and power supply modules in traditional solutions.

[0079] Example 4: Independent self-powered upper and lower bridge arms in a half-bridge structure

[0080] This embodiment applies to a half-bridge power conversion structure. The upper bridge arm self-powered unit is connected between the positive terminal of the DC bus and the midpoint of the bridge arm, while the lower bridge arm self-powered unit is connected between the midpoint of the bridge arm and the negative terminal of the DC bus. The internal structures of the upper and lower bridge arm power supply units are identical, both employing varistors for energy harvesting, energy storage capacitors, and feedback cutoff mechanisms. Because the potential at the midpoint of the bridge arm changes with the switching state, each power supply unit can still stably establish a drive voltage at its respective reference point, avoiding the dependence of traditional bootstrap power supply on duty cycle and timing, and significantly improving the system's applicability.

[0081] Example 5: Common-mode interference suppression under drive-ground isolation conditions

[0082] In this embodiment, there is no DC electrical connection between the drive ground and the power side ground, and the self-powered unit is completely suspended on the power side. The varistor obtains energy only through transient changes in the bus voltage and does not form a continuous conduction path. This structure effectively cuts off the conduction path of common-mode interference, significantly reducing drive power supply noise. Compared to solutions that rely on isolation transformers or isolation power modules, this embodiment achieves equivalent anti-interference effects without adding isolation devices.

[0083] Example 6: Modular self-powered application in multi-device systems

[0084] In this embodiment, the self-powered supply structure is applied to a multi-level power conversion system, where each power device is independently configured with a varistor-based energy harvesting and storage feedback unit. These units operate independently, each establishing a stable drive voltage based on its corresponding node potential. When an abnormal voltage fluctuation occurs in the branch containing any power device, only the corresponding power supply unit is affected, while the remaining units continue to operate normally. This embodiment demonstrates the system-level scalability and fault tolerance of this technical solution, further highlighting its engineering application value.

[0085] Figure 4 The waveform diagram is for "Simulation of self-powered startup and steady-state process of half-bridge circuit".

[0086] Where V(5,4) represents the drain-source voltage (DS voltage) waveform of the upper MOSFET, V(3,2) represents the drain-source voltage waveform of the lower MOSFET, V(Vout1.1,4) represents the output voltage waveform of the upper MOSFET's self-powered circuit, and V(Vout1,2) represents the output voltage waveform of the lower MOSFET's self-powered circuit. From the experiment... Figure 4It can be clearly seen that before the alternating conduction control signal is applied to the MOSFETs, the half-bridge circuit is in an initial static state, with the upper MOSFET in the on state and the lower MOSFET in the off state. Since the lower MOSFET is off, its corresponding self-powered circuit can operate normally using the voltage conditions formed by the upper MOSFET being on, thus enabling the lower MOSFET self-powered circuit to establish a stable power supply level first.

[0087] After the control signal is activated, the upper and lower MOSFETs begin to alternately turn on and off according to the predetermined drive logic. At this time, it can be observed that the upper MOSFET's self-powered circuit begins to operate and can complete the energy acquisition and voltage establishment process in a very short time. As the alternating conduction state enters a steady state, the self-powered output voltages of both the upper and lower MOSFETs quickly converge and stabilize within the preset level range, without any prolonged undervoltage or abnormal oscillation. This indicates that the half-bridge self-powered structure proposed in this invention can achieve reliable switching during the startup phase and ensure the rapid establishment and stable operation of the upper and lower MOSFET drive power supplies.

[0088] Figure 5 The simulation waveform diagram of the dynamic charging and discharging characteristics of the output voltage of the half-bridge self-powered circuit is shown.

[0089] Combination Figure 5 The waveform shown can be further analyzed to understand the voltage change mechanism of the self-powered circuit during dynamic operation. When the corresponding MOSFET is turned on, the energy consumption of the self-powered output terminal by the drive and control circuits is temporarily interrupted, resulting in a certain degree of voltage drop in the output voltage. This drop is characterized by continuous and controllable voltage decay, without any sudden changes or instability.

[0090] When the corresponding MOSFET switches from the on state to the off state, the self-powered circuit regains the charging conditions, and the output capacitor can be replenished with energy again, allowing the output voltage to gradually recover and return to its original stable level. As a result, the self-powered output voltage exhibits periodic small fluctuations during the MOSFET's on and off cycles, but overall remains within the safe operating range allowed by the drive circuit.

[0091] Through experiments Figure 4 With experiment Figure 5 It can be verified that the self-powered half-bridge scheme proposed in this invention can not only quickly establish the driving power supply of the upper and lower transistors during the startup phase, but also, during normal alternating conduction operation, the self-powered output voltage only produces controllable and periodic ripple changes, which will not adversely affect the reliability of the MOS transistor drive and the system stability, thus demonstrating good engineering applicability and technical effect.

[0092] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A power supply circuit for driving a self-powered device based on a varistor, characterized in that, include: A first varistor and a second varistor are connected in series. The first end of the first varistor is connected to the positive terminal of the DC bus, and the second end of the second varistor is connected to the drive ground. The first transistor has its control terminal connected to the common node of the first and second varistors, and its controlled terminal connected to the charging circuit of the energy storage capacitor, which is used to conduct and form a charging path when the voltage of the energy storage capacitor is lower than a set value. A voltage detection and feedback unit is connected across the energy storage capacitor and is used to generate a control signal when the voltage of the energy storage capacitor reaches a set value. The second transistor has a control terminal that receives the control signal and a controlled terminal that is connected to the control terminal of the first transistor, and is used to turn off the first transistor under the action of the control signal. The first and second varistors form a self-powered voltage source under the action of the DC bus voltage, which charges the energy storage capacitor without external auxiliary power supply, and automatically stops charging after the energy storage capacitor voltage reaches a set value.

2. The self-powered power device drive power supply circuit according to claim 1, characterized in that: The clamping voltage of the first varistor is lower than the drain-source withstand voltage of the power device, and the total clamping voltage of the first varistor and the second varistor connected in series is higher than the maximum surge voltage of the DC bus.

3. The self-powered power device drive power supply circuit according to claim 1, characterized in that: The voltage detection and feedback unit includes a first voltage divider resistor and a second voltage divider resistor connected in series, as well as a voltage regulator. The stable voltage of the energy storage capacitor is changed by adjusting the voltage division ratio and the voltage regulation value.

4. A power conversion drive power supply system based on varistor self-powered operation, characterized in that, include: At least one bridge power conversion unit, the bridge power conversion unit including an upper bridge arm power device and a lower bridge arm power device; Self-powered drive power supply units are respectively provided corresponding to the upper bridge arm power device and the lower bridge arm power device; Each of the self-powered drive power supply units includes an energy harvesting branch composed of series varistors, an energy storage capacitor, and a semiconductor device for controlling charging and cutting off. Each of them independently obtains energy from the DC bus or bridge arm node of the bridge power conversion unit and supplies power to the corresponding power device driver.

5. The drive power supply system according to claim 4, characterized in that: The upper arm self-powered drive power supply unit is connected between the positive terminal of the DC bus and the midpoint of the arm, and the lower arm self-powered drive power supply unit is connected between the midpoint of the arm and the negative terminal of the DC bus.

6. The drive power supply system according to claim 4, characterized in that: The respective power supply units are electrically isolated from each other, and there is no DC conduction path between the drive ground and the power side ground.

7. A method for driving and supplying power to a self-powered device based on a varistor, characterized in that, Includes the following steps: Under the influence of DC bus voltage, the energy harvesting voltage is obtained through a series-connected varistor; When the voltage of the energy storage capacitor is lower than the set value, the first switching device is turned on to charge the energy storage capacitor; The voltage of the energy storage capacitor is detected, and a control signal is generated when the voltage reaches a set value; Based on the control signal, the first switching device is turned off, blocking the charging path and maintaining the voltage of the energy storage capacitor within the set range; The method does not rely on an external auxiliary power source throughout the entire process.

8. The method according to claim 7, characterized in that: The set voltage can be adjusted by changing the voltage divider detection ratio or the voltage regulation threshold to adapt to the driving voltage requirements of different power devices.

9. The method according to claim 7, characterized in that: The parameters of the varistor are configured such that the clamping voltage of a single varistor is lower than the withstand voltage of the power device, and the total clamping voltage of the series varistors is higher than the highest transient voltage of the DC bus.

10. The method according to claim 7, characterized in that: In a half-bridge, full-bridge, or multi-level power conversion structure, the self-powered drive supply method is executed independently for each power device.

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