Power device driving power supply circuit for voltage-sensitive-capacitor hybrid power taking

Abstract

The invention belongs to the technical field of power semiconductor driving, and discloses a voltage-sensitive-capacitor hybrid power-taking power device driving power supply circuit, which comprises a voltage-sensitive resistor MOV branch circuit and a capacitor power-taking branch circuit which are connected in parallel between a high-voltage bus and a driving ground, the energy storage element is connected to a common node; the anti-reverse diode is used for preventing energy from flowing backwards; the gate driver IC uses the energy storage element as the sole power supply. Once the voltage of the energy storage element is charged above the steady-state threshold of the piezoresistor branch circuit, the voltage difference between the two ends of the piezoresistor branch circuit is lower than the threshold for maintaining conduction of the piezoresistor branch circuit, so that work is automatically quitted, and subsequent energy is completely supplied by the capacitor branch circuit. According to the design, the piezoresistor only acts at necessary transient moments, the service life problem of the piezoresistor under continuous work is fundamentally solved, meanwhile, an independent isolation power supply and a surge protection device are omitted, and integration of structure simplification, reliability improvement and common-mode interference suppression of driving power supply is achieved. In a half-bridge, full-bridge or multi-level topology, each bridge arm power tube is respectively configured with symmetrical self-energy-taking units, and each unit is integrated with a voltage-sensitive power-taking branch and a capacitance power-taking branch.

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 power device driving power supply circuit that uses a varistor-capacitor hybrid power source. Background Technology

[0002] Existing self-driven circuits, such as CN206117536U, utilize capacitive coupling to achieve synchronous rectification and passive power supply. However, they are only designed for low-to-medium voltage applications and lack surge protection. When the bus voltage rises to 600V, transient overvoltage can directly damage the driving components. CN106374739B uses a charge pump and Boost to accelerate capacitor charging, but it still relies on low-voltage input and cannot be directly connected to a 600V bus. Furthermore, it does not address the issue of accelerated aging of power-harvesting components due to long-term high-voltage stress. All of the above solutions belong to a "single capacitor power harvesting + no protection" architecture, revealing two common defects in high-voltage applications: ① lacking the transient surge absorption capability required by a 600V bus; ② the power-harvesting components are continuously exposed to a high-voltage electric field, leading to rapid degradation in lifespan and reliability. This invention addresses these core issues by integrating high-voltage surge protection while completely resolving the lifespan and reliability bottlenecks of power-harvesting components under continuous operating conditions, achieving a unified approach of "protection, power harvesting, and long lifespan." Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention provides a power device driving power supply circuit that uses a hybrid varistor-capacitor power source.

[0004] This invention is implemented as follows: a power device driving power supply circuit with hybrid varistor-capacitor power extraction, comprising:

[0005] High-voltage capacitor C3 is connected at one end to the high-voltage terminal of the power device and at the other end to C2;

[0006] Low-voltage capacitor C2 is connected to C3 at one end and to Vdrivergnd at the other end, forming a capacitor power supply branch;

[0007] Diode D2 is connected in parallel across C2;

[0008] The first NPN transistor Q1 has its collector connected to the common node of C3 and C2, its emitter connected to the anode of D3, and connected to one end of the positive terminal of C1 through D3. Its base is connected to the common node of C3 and C2 through resistor R1.

[0009] The emitter of the second NPN transistor Q2 is connected to the driving ground Vdrivergnd via the Zener diode D1, and the collector is connected to the base of Q1. The base is connected to C1 via a series resistor network R3R4.

[0010] Zener diode D1, with its cathode connected to the emitter of Q2 and its anode connected to drive ground, is used to provide a fixed reference potential for the emitter of Q2;

[0011] The reverse protection diode D3 has its anode connected to the emitter of Q1 and its cathode connected to the positive terminal of the energy storage capacitor C1, which is used to prevent the current of C1 from flowing back into the varistor branch;

[0012] The current-limiting resistor R5 is connected at one end to the positive terminal of C1 and at the other end to the cathode of D1.

[0013] R3 and R4 are connected in series, with their two ends connected to the two ends of C1, forming a voltage divider network to provide voltage to the base of Q2;

[0014] Zener diode D5 has its cathode connected to the emitter of Q4 and its anode connected to the drive ground, and is used to provide a fixed reference potential for the emitter of Q4;

[0015] The first varistor MOV1 is used to connect one end to the high-voltage bus HV;

[0016] The second varistor MOV2 is connected at one end to the other end of MOV1, and at the other end to the drive ground Vdrivergnd.

[0017] The third NPN transistor Q3 has its collector connected to the common node of MOV1 and MOV2, its emitter connected to the anode of D4, and its base connected to one end of the positive terminal of C1 through D4.

[0018] The fourth NPN transistor Q4 has its emitter connected to the driver ground Vdrivergnd via Zener diode D5, and its collector connected to the base of Q3. The base is connected to C1 via a series resistor network R6R7.

[0019] The anti-reverse diode D4 has its anode connected to the emitter of Q3 and its cathode connected to the positive terminal of the energy storage capacitor C1, which is used to prevent the current of C1 from flowing back into the varistor branch;

[0020] The current-limiting resistor R8 is connected at one end to the positive terminal of C1 and at the other end to the cathode of D5.

[0021] R6 and R7 are connected in series, with their two ends connected to the two ends of C1, forming a voltage divider network to provide voltage to the base of Q4;

[0022] The energy storage capacitor C1 is connected to the cathode of D3 at its positive terminal and to Vdrivergnd at the other end, serving as the sole DC power supply for the gate driver IC.

[0023] Among them, the varistor power supply closed-loop voltage VMOV is lower than the capacitor power supply closed-loop voltage VCAP; when the voltage of C1 rises to VMOV, the varistor branch is cut off, and the system switches to the C3 branch to continue to supply power, so that MOV is in a zero-stress resting state under long-term continuous switching.

[0024] Furthermore, the expansion scheme of this half-bridge circuit includes: an upper bridge arm power supply unit, connected between the positive terminal DC+ of the DC bus and the midpoint of the half-bridge, used to provide power to the upper transistor driver; and a lower bridge arm power supply unit, connected between the midpoint of the half-bridge and the negative terminal DC- of the DC bus, used to provide power to the lower transistor driver; both the upper and lower bridge arm power supply units adopt a dual-branch hybrid structure of varistor power supply and capacitor power supply, and the circuit topology of the two units is symmetrical.

[0025] Furthermore, by selecting the varistor voltages of MOV1 and MOV2 and the capacitance value of C3, VMOV is made lower than VCAP, ensuring that the varistor branch automatically exits after startup.

[0026] Furthermore, the anti-reverse diode D3 is a low forward voltage drop fast turn-off diode to achieve rapid switching and reduce current loss.

[0027] Furthermore, C3 is a pF-level high-voltage capacitor and C2 is an nF-level capacitor, used to optimize transient overshoot suppression.

[0028] Furthermore, there is no electrical connection between the driving ground Vdrivergnd and the primary power ground PGND, which naturally cuts off the dv / dt common-mode current path.

[0029] Furthermore, the power device is any one of Si / SiC MOSFET, GaNFET, or IGBT.

[0030] Furthermore, in half-bridge, full-bridge, or multi-level topologies, the self-powered units of MOV1-MOV2, C3, C2, D1-D4, Q1-Q4, R1-R8, C1, and IC are all driven by isolated units.

[0031] Furthermore, the connection relationship of each component inside the upper and lower bridge arm power supply unit is the same as that of the single tube power supply unit structure described in claim 1;

[0032] Furthermore, the half-bridge circuit has a start-up control logic with asynchronous cut-off and switch-assisted energy replenishment: In the initial stage, the DC bus voltage is applied across DC+ and DC-, and the current flows through the series loop formed by the MOV1 / MOV2 varistor branch of the upper arm and the MOV3 / MOV4 varistor branch of the lower arm, while charging the energy storage capacitors C1 and C4. Due to component differences, one of the energy storage capacitors reaches the set MOV closed-loop voltage VMOV first, triggering the conduction of the corresponding fourth NPN transistor Q4 or the eighth NPN transistor Q8, resulting in the cut-off of the corresponding charging transistor Q3 or Q7, thus causing asynchronous pre-charge cut-off of the overall series charging path. Subsequently, the power tube that has reached the VMOV potential is controlled to conduct through an external signal, causing a potential jump at the half-bridge midpoint. The power supply unit on the side that is not fully charged directly bears the bus voltage difference and quickly replenishes the energy to VMOV through its varistor branch. When the power tube enters the continuous switching state and generates du / dt, the C3 / C2 capacitor energy extraction branch of the upper arm and the C6 / C5 capacitor energy extraction branch of the lower arm take over the power supply. The energy storage capacitors that were originally at the VMOV potential and the energy storage capacitors on the other side are further charged and finally stabilized at the set capacitor power-taking closed-loop voltage VCAP.

[0033] Furthermore, the varistor voltage setting of the varistor satisfies: VMOV1 + VMOV3 < Vdc, where Vdc is the DC bus voltage, to ensure that the loop can conduct in series and perform initial charging during the start-up phase; VMOV1 + VMOV2 > Vdc and VMOV3 + VMOV4 > Vdc.

[0034] Combined with the above technical solutions and the solved technical problems, the advantages and positive effects of the technical solution to be protected by the present invention are as follows:

[0035] First of all, by sharing the same energy storage capacitor C1 for the varistor power-taking branch and the capacitor power-taking branch, the present invention realizes the organic unity of the start-up power-taking and steady-state power supply paths, avoiding the problem of additionally configuring an isolated power supply module for the drive circuit in the traditional scheme. This structure can complete the drive power supply without adding a transformer, optocoupler, or independent isolated DC / DC, greatly reducing the system volume, cost, and design complexity, and improving the overall reliability and consistency.

[0036] Secondly, by respectively setting anti-reverse diodes D3 and D4 in the varistor branch and the capacitor branch, the reverse energy backflow paths between different branches and from the energy storage capacitor to the main power circuit are effectively blocked, ensuring that the current direction during the branch switching process is always controlled, and realizing the natural transition of the power-taking paths in the start-up phase and the steady-state phase. This switching process does not rely on mechanical or logic switching devices, avoiding switching losses and control lag problems.

[0037] Furthermore, by leveraging the pull-up effect of R1 and R2 on the gates of Q1 and Q3, the relevant switching devices can quickly enter the expected conduction state during the initial power-up phase, before the lower transistor has established a stable drive power supply. This ensures that the varistor power-supply branch participates in the operation first. This design ensures the determinism and repeatability of power supply during the startup phase, avoiding startup failures caused by uncertain initial conditions.

[0038] Furthermore, this invention establishes a dual-detection mechanism using Q2 and Q4 to accurately determine the operating state of the varistor voltage VMOV. When VMOV reaches a preset threshold, the varistor power-drawing branch can promptly exit the power-drawing process, preventing the varistor from experiencing continuous current stress during the steady-state phase. Thus, the varistor only participates in operation briefly during the startup phase and remains in a near-zero-stress state after fulfilling its function, significantly extending its service life.

[0039] This invention provides an effective solution to the long-standing problem of "MOV continuous conduction aging" in the field. Traditional MOV power extraction methods require milliampere-level continuous current, which easily causes ZnO grain heating, resulting in a sharp reduction in device lifespan from the designed ten-year level to the thousand-hour level. This invention, however, fundamentally avoids the long-standing technical problem of short MOV lifespan by utilizing varistor power extraction only during the startup phase and achieving zero-stress shutdown during the steady-state phase.

[0040] Furthermore, this invention overcomes the technical prejudice that "MOVs can only clamp in parallel and cannot extract energy." By satisfying the voltage relationship of "VMOV1 < Vds and VMOV1 + VMOV2 > Vds", it realizes series voltage division energy extraction of MOVs and automatically exits in the steady state stage, so that the energy originally used for clamping surges is converted into the energy required for driving power supply, thus expanding the engineering application boundaries of MOVs.

[0041] Finally, by eliminating the electrical connection between the driver ground VdriverGND and the primary ground PGND, this invention naturally cuts off the conduction path of dv / dt common-mode interference, achieving high anti-interference capability without the need for any isolation transformers or optocouplers. This technical solution can be flexibly applied to half-bridge, full-bridge, and multi-level topologies, and supports independent power supply configuration for each power transistor, making the system architecture simple, reliable, and possessing good versatility and engineering promotion value. Attached Figure Description

[0042] Figure 1 These are schematic diagrams of the traditional drive power supply structure and common-mode current path provided in the embodiments of the present invention; a: traditional scheme; b: self-powered scheme;

[0043] Figure 2This is a schematic diagram of a single-transistor circuit provided in an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of a half-bridge circuit provided in an embodiment of the present invention;

[0045] Figure 4 Simulation waveforms of the voltage-sensitive power extraction branch and the capacitor power extraction branch working together in a half-bridge topology. Detailed Implementation

[0046] 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.

[0047] This invention provides a power device driving power supply circuit with a hybrid varistor-capacitor power source, comprising:

[0048] High-voltage capacitor C3 is connected at one end to the high-voltage terminal of the power device and at the other end to C2;

[0049] Low-voltage capacitor C2 is connected to C3 at one end and to Vdrivergnd at the other end, forming a capacitor power supply branch;

[0050] Diode D2 is connected in parallel across C2;

[0051] The first NPN transistor Q1 has its collector connected to the common node of C3 and C2, its emitter connected to the anode of D3, and connected to one end of the positive terminal of C1 through D3. Its base is connected to the common node of C3 and C2 through resistor R1.

[0052] The emitter of the second NPN transistor Q2 is connected to the driving ground Vdrivergnd via the Zener diode D1, and the collector is connected to the base of Q1. The base is connected to C1 via a series resistor network R3R4.

[0053] Zener diode D1, with its cathode connected to the emitter of Q2 and its anode connected to drive ground, is used to provide a fixed reference potential for the emitter of Q2;

[0054] The reverse protection diode D3 has its anode connected to the emitter of Q1 and its cathode connected to the positive terminal of the energy storage capacitor C1, which is used to prevent the current of C1 from flowing back into the varistor branch;

[0055] The current-limiting resistor R5 is connected at one end to the positive terminal of C1 and at the other end to the cathode of D1.

[0056] R3 and R4 are connected in series, with their two ends connected to the two ends of C1, forming a voltage divider network to provide voltage to the base of Q2;

[0057] Zener diode D5 has its cathode connected to the emitter of Q4 and its anode connected to the drive ground, and is used to provide a fixed reference potential for the emitter of Q4;

[0058] The first varistor MOV1 is used to connect one end to the high-voltage bus HV;

[0059] The second varistor MOV2 is connected at one end to the other end of MOV1, and at the other end to the drive ground Vdrivergnd.

[0060] The third NPN transistor Q3 has its collector connected to the common node of MOV1 and MOV2, its emitter connected to the anode of D4, and its base connected to one end of the positive terminal of C1 through D4.

[0061] The fourth NPN transistor Q4 has its emitter connected to the driver ground Vdrivergnd via Zener diode D5, and its collector connected to the base of Q3. The base is connected to C1 via a series resistor network R6R7.

[0062] The anti-reverse diode D4 has its anode connected to the emitter of Q3 and its cathode connected to the positive terminal of the energy storage capacitor C1, which is used to prevent the current of C1 from flowing back into the varistor branch;

[0063] The current-limiting resistor R8 is connected at one end to the positive terminal of C1 and at the other end to the cathode of D5.

[0064] R6 and R7 are connected in series, with their two ends connected to the two ends of C1, forming a voltage divider network to provide voltage to the base of Q4;

[0065] The energy storage capacitor C1 is connected to the cathode of D3 at its positive terminal and to Vdrivergnd at the other end, serving as the sole DC power supply for the gate driver IC.

[0066] Among them, the varistor power supply closed-loop voltage VMOV is lower than the capacitor power supply closed-loop voltage VCAP; when the voltage of C1 rises to VMOV, the varistor branch is cut off, and the system switches to the C3 branch to continue to supply power, so that MOV is in a zero-stress resting state under long-term continuous switching.

[0067] The expansion scheme of this half-bridge circuit includes: an upper bridge arm power supply unit, connected between the positive terminal DC+ of the DC bus and the midpoint of the half-bridge, used to provide power to the upper transistor driver; and a lower bridge arm power supply unit, connected between the midpoint of the half-bridge and the negative terminal DC- of the DC bus, used to provide power to the lower transistor driver; both the upper and lower bridge arm power supply units adopt a dual-branch hybrid structure of varistor power supply and capacitor power supply, and the circuit topology of the two units is symmetrical.

[0068] By selecting the varistor voltages of MOV1 and MOV2 and the capacitance value of C3, VMOV is made lower than VCAP, ensuring that the varistor branch automatically exits after startup.

[0069] The anti-reverse diode D3 is a low forward voltage drop fast turn-off diode to achieve rapid switching and reduce current loss.

[0070] C3 is a high-voltage capacitor in the pF level, and C2 is a capacitor in the nF level, which is used to optimize transient overshoot suppression.

[0071] There is no electrical connection between the driving ground Vdrivergnd and the primary-side power ground PGND, which naturally cuts off the dv / dt common-mode current path.

[0072] The power device is any one of Si / SiC MOSFET, GaN FET or IGBT.

[0073] In a half-bridge, full-bridge or multilevel topology, the self-powered units of MOV1-MOV2, C3, C2, D1-D4, Q1-Q4, R1-R8, C1 and IC, and the driving grounds of each unit are isolated from each other.

[0074] The connection relationship of each component inside the upper and lower bridge arm power supply units is the same as the structure of the single-tube power supply unit described in claim 1;

[0075] As Figure 3 As shown, the half-bridge circuit has a startup control logic of asynchronous cutoff and switch-assisted energy replenishment: In the initial stage, the DC bus voltage is applied to both ends of DC+ and DC-, and the current flows through the series loop formed by the MOV1 / MOV2 varistor branch of the upper bridge arm and the MOV3 / MOV4 varistor branch of the lower bridge arm, while charging the energy storage capacitors C1 and C4; due to component differences, one of the energy storage capacitors reaches the set varistor closed-loop voltage VMOV first, and triggers the conduction of the corresponding fourth NPN transistor Q4 or the eighth NPN transistor Q8 on that side, resulting in the cutoff of the corresponding charging transistor Q3 or Q7, so that the overall series charging path has an asynchronous first charge cutoff; Subsequently, the power transistor that has reached the VMOV potential is controlled to conduct through an external signal, causing a potential jump at the midpoint of the half-bridge. The power supply unit on the side that is not fully charged directly bears the bus voltage difference and quickly replenishes the energy to VMOV through its varistor branch; when the power transistor enters the continuous switching state and generates du / dt, the C3 / C2 capacitor energy extraction branch of the upper bridge arm and the C6 / C5 capacitor energy extraction branch of the lower bridge arm take over the power supply. The energy storage capacitors that were originally at the VMOV potential and the energy storage capacitors on the other side are further charged and finally stabilized at the set capacitor power-taking closed-loop voltage VCAP. <00​​​​​​As shown, it consists of sub-figures a and b, used to compare the structural differences and common-mode interference paths between traditional isolated power supply and the self-powered solution of the present invention in high-voltage SiC / GaN applications.

[0078] (a) In the traditional approach, the primary-side control circuit supplies power to the secondary-side driver via an optocoupler or an isolated DC-DC module. Parasitic capacitance exists between the secondary-side driver ground (PGND) and the primary-side ground (AGND). During high-speed switching of power devices, the extremely high dv / dt forms a common-mode current through the parasitic capacitance, directly coupling to the primary-side control side, causing EMI, signal mis-triggers, and stress on the isolation devices. Furthermore, traditional isolated power supplies cannot absorb bus surges, requiring an additional parallel TVS / MOV, resulting in a complex, large-volume, and high-failure-rate drive power supply path.

[0079] b (Self-Powered Scheme) adopts a self-powered drive + optical isolation architecture, completely disconnecting the drive ground (Vdrivergnd) from the primary ground and cutting off the common mode circuit shown in Figure a; thus achieving high-voltage side self-powered supply without isolation power supply or additional protection devices.

[0080] Core parameters and dual closed-loop voltage targets

[0081] High-voltage bus voltage: 600VDC;

[0082] V_M: 13V (Q2 conduction threshold, triggering the varistor branch to cut off);

[0083] Capacitor-driven closed-loop voltage V_C: 15V (IC rated operating voltage, final stable output).

[0084] like Figure 2 As shown, the selection and functional description of key components for a single tube.

[0085] (a) Varistors MOV1 and MOV2 (model 07D221K and 561K combination)

[0086] 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).

[0087] Selection criteria: 600V bus series voltage division, MOV1 bears about 200V and MOV2 bears about 400V, both lower than their respective maximum clamping voltages. Normally high resistance, series clamping of 1100V during surge, lower than 1200V SiC MOSFET withstand voltage, can safely absorb transient overvoltages of the bus.

[0088] Core functions: series voltage divider for energy extraction, charging C1 during startup, low-resistance discharge during surges, and automatic exit after protection is completed.

[0089] (ii) Anti-reverse diode (PMEG4010CEH Schottky diode)

[0090] Limits: VR≤40V, IF≤1A (55℃), repetitive peak forward current IFRM=7A (tp≤1ms, δ≤0.25), 8ms square wave non-repetitive surge IFSM=9A;

[0091] Electrical characteristics: Typical VF=490mV at 1A, maximum 570mV; reverse leakage current IR≤50μA (40V, 25℃);

[0092] Core functions: Blocks reverse backflow of C1 to the varistor branch; 0.5V-level low voltage drop reduces branch switching losses; 7A pulse capability is sufficient to absorb high-frequency switching spikes, ensuring that energy does not flow back to the dual branches.

[0093] Capacitor power supply branch design

[0094] High-voltage capacitor C3 (small capacitance design in the pF range)

[0095] Design rationale: To adapt to the working environment of high-voltage busbars, the high dv / dt electric field coupling effect generated by the turn-off transient of SiC MOSFET is utilized to quickly capture transient energy and transfer it to the energy storage capacitor C1; the pF-level small capacitance design can balance coupling efficiency and response speed, avoid energy lag caused by excessive capacitance, and ensure that the voltage of C1 does not drop significantly during the switching process;

[0096] Core function: Dynamically replenishes transient energy for C1, maintains the stability of the closed-loop voltage of the capacitor power supply, and is suitable for high-frequency switching scenarios.

[0097] Low-voltage capacitor C2 (nF level)

[0098] C2 and C3 are connected in series between the high-voltage bus and the drive ground. The capacitance of C3 is much smaller than that of C2. At the moment of turn-off, most of the high voltage falls on C3, while C2 only receives a safe low voltage and is not easily broken down. At the same time, the nF-level C2 presents low resistance to high-frequency glitches, directly short-circuiting the switching noise to ground, thus filtering high-frequency signals.

[0099] Core parameter calculation and branch switching verification

[0100] (a) Charging and switching logic of varistor branch

[0101] 1. Series voltage divider: After MOV1 and MOV2 are connected in series, MOV1 carries about 200V and MOV2 carries about 400V. At this time, the varistor is in a dynamic high resistance state, which can quickly charge C1.

[0102] 2. Switching condition: When the voltage of C1 rises above 13V (the closed-loop voltage of varistor power extraction), the voltage difference between the base and emitter of Q2 reaches the conduction condition, Q4 conducts, Q3 turns off, the varistor branch automatically exits the operation, and switches to the capacitor power extraction branch.

[0103] (II) Verification of the power supply capacity of the capacitor branch

[0104] 1. Transient energy supplement current: At the moment when the SiC MOSFET turns off, C3 couples high-frequency energy to the energy storage capacitor using the steep dV / dt, and the short-term energy supplement current is sufficient to cover the consumption of the IC.

[0105] 2. Voltage stability: After C1 is charged to 15V, when the IC consumes energy, C3 quickly supplements energy to maintain a stable output of 15V.

[0106] Complete working process:

[0107] Power-on startup stage: After the high-voltage bus HV is applied, MOV1 and MOV2 are connected in series for voltage division to provide an initial charging current to C1, and the voltage of C1 gradually rises from 0V.

[0108] Branch switching stage: When the voltage of C1 rises above 13V, Q3 turns off, the varistor branch exits, the anti-reverse diode is cut off, and the capacitor power extraction branch takes over the power supply.

[0109] Steady-state power supply stage: C3 captures transient energy to supplement C1, and the voltage of C1 continues to rise to 15V.

[0110] Dynamic adjustment stage: When the IC consumes energy, C3 quickly supplements energy to maintain a stable output of 15V, ensuring reliable switching of the power devices.

[0111] Selection and function description of key components in the bridge

[0112] MOV1~MOV4 in the varistor branch: MOV1 on the upper bridge arm and MOV3 on the lower bridge arm select varistors with a varistor voltage of 220V of 07D221K, MOV2 on the upper bridge arm and MOV4 on the lower bridge arm select varistors with a varistor voltage of 560V of 561K. The total varistor voltage of a single arm is 780V. The normal high-resistance leakage current is <5μA. The maximum clamping voltage during bus surge is approximately 1100V, which is lower than the device's withstand voltage of 1200V, effectively preventing breakdown.

[0113] C3C2 and C6C5 in the capacitor power extraction branch: The high-voltage coupling capacitors C3C6 use high-voltage ceramics in pF level, and the low-voltage capacitors C2C5 use nF level. The steep du / dt electric field coupling is used to capture the transient displacement current of the SiC MOSFET turn-off. C3 << C2 makes the high voltage mainly drop on C3 to ensure the safety of the low-voltage side.

[0114] Anti-reverse diodes D3D4D8D9: Select PMEG40100CEH Schottky diode, VF≈0.49V, to reduce switching losses and block energy backflow from the energy storage capacitor.

[0115] Bridge working logic

[0116] Series start-up and asynchronous cut-off: When Vdc is powered on, the upper and lower transistors are initially turned off. The current charges C1 and C4 simultaneously through the series circuit of MOV1, Q3, MOV3, and Q7. If C1 reaches 13V first, Q4 will saturate and conduct, pulling down the base of Q3 to cut it off, thus interrupting the series path.

[0117] Switch-assisted power replenishment: The upper transistor driver of SS, which has already obtained 13V, controls the MOSFET to turn on, pulls the midpoint of the half-bridge to DC+, and the lower bridge arm unit directly crosses the 600V bus, quickly replenishing C4 to 13V through the varistor branch.

[0118] Steady-state operation and zero-stress switching: After the power transistors switch at high frequency, the dv / dt coupling energy is taken over by the C3C6 branch. Due to the continuous energy replenishment of the 15V threshold, C1C4 is raised from 13V to 15V. When the 13V threshold is exceeded, Q4Q8 remains on, Q3Q7 is permanently cut off, and MOV1~MOV4 rests with zero stress, avoiding high-frequency pulse life degradation.

[0119] Extended applications:

[0120] In a half-bridge / full-bridge / multi-level topology, each power device replicates a set of MOV1-MOV2, C3, C2, D1-D4, Q1-Q4, R1-R8, C1, and IC, with independent driving grounds, naturally cutting off the system-level common-mode interference path.

[0121] Example 1: Single-transistor self-starting power supply embodiment based on varistor priority activation

[0122] This embodiment provides a self-powered supply method for driving a single power device. During the initial power-on phase, the DC bus voltage is applied between the high-voltage terminal and the drive ground. Since the power device has not yet entered the switching state, there is no effective voltage change at the high-voltage terminal, and the capacitor-driven power supply branch composed of the high-voltage and low-voltage capacitors cannot form an effective energy transfer. At this time, the first and second varistors, connected in series, enter the conducting state, forming a stable startup power supply channel under their varistor characteristics to charge the energy storage capacitor.

[0123] As the voltage of the energy storage capacitor gradually increases, the voltage divider network samples the voltage. When the sampled voltage reaches the preset varistor closed-loop voltage, the control transistor corresponding to the varistor power extraction branch flips its state under the reference of the voltage regulator unit, thus cutting off the varistor power extraction branch. This process requires no external control signal and is entirely triggered by the energy storage capacitor voltage state, achieving automatic disconnection of the varistor branch.

[0124] This embodiment solves the problem that the driver cannot obtain initial power when the power device is not switched on, while avoiding the varistor from being subjected to long-term stress in steady state, thus demonstrating the essential difference between startup and steady-state power harvesting mechanisms.

[0125] Example 2: Steady-state continuous power supply based on capacitor-driven closed-loop system

[0126] After startup in Example 1, the power device enters a continuous switching state under the control of the drive signal, causing periodic changes in the high-voltage terminal potential. The high-voltage capacitor couples this voltage change, which is then converted by the low-voltage capacitor to form an energy channel released to the drive ground, thus activating the capacitor's power supply branch.

[0127] The energy harvested by the capacitor-driven power supply branch is transferred to the energy storage capacitor through the anti-reverse unit for further charging. When the energy storage capacitor voltage exceeds the varistor closed-loop voltage, the varistor power supply branch remains in the off state, and only the capacitor-driven power supply branch provides the power. By setting the reference voltage of the second control unit, the energy storage capacitor voltage is stabilized within the preset capacitor-driven power supply closed-loop voltage range.

[0128] This embodiment demonstrates that the system no longer relies on varistor devices in the steady-state phase, and the power supply process is entirely based on the voltage changes generated by the switching of the power devices themselves, thus avoiding additional losses and reliability risks.

[0129] Example 3: Seamless transition between varistor and capacitor power supply

[0130] This embodiment focuses on describing the switching process between varistor power supply and capacitor power supply. At the end of the startup phase, when the energy storage capacitor voltage approaches the varistor closed-loop voltage threshold, the varistor power supply branch gradually enters the critical cutoff state. At this time, the power device has begun to exhibit initial switching action, and a voltage change of limited amplitude is generated at the high-voltage end.

[0131] Thanks to the unidirectional conduction characteristic of the anti-reverse unit, the varistor power extraction branch and the capacitor power extraction branch are allowed to coexist briefly, but the energy transmission direction always points towards the energy storage capacitor to avoid mutual interference. When the energy storage capacitor voltage exceeds the varistor closed-loop voltage, the varistor power extraction branch is completely cut off, and the capacitor power extraction branch naturally takes over the power supply task.

[0132] This embodiment demonstrates the hierarchical coordination relationship between the two power supply methods in the voltage dimension, achieving a smooth switching without abrupt changes or control signals.

[0133] Example 4: Asynchronous Start-up and Auxiliary Power Supply Example under Half-Bridge Structure

[0134] This embodiment applies to a half-bridge topology. After the DC bus voltage is applied, the varistor power supply branches of the upper and lower bridge arm power supply units form a series circuit, simultaneously charging their respective energy storage capacitors. Due to differences in device parameters, one side's energy storage capacitor reaches the varistor closed-loop voltage first, triggering the corresponding control unit to operate, causing that side's varistor power supply branch to shut down prematurely, thus disrupting the series circuit.

[0135] Subsequently, the power devices on the side that have completed startup are turned on by an external control signal, and the midpoint potential of the half-bridge transitions. The power supply unit on the side that has not completed charging directly bears the bus voltage difference, and its varistor power extraction branch re-forms an independent power extraction channel, enabling the corresponding energy storage capacitor to quickly replenish energy and reach the varistor closed-loop voltage.

[0136] This embodiment avoids the limitation that the upper and lower drive power supplies must start synchronously in traditional half-bridge systems, thus improving the startup reliability of the system under actual device discrete conditions.

[0137] Example 5: Common-mode current suppression under drive-ground isolation conditions

[0138] In this embodiment, no DC or AC connection path is provided between the drive ground and the power side ground. The driver power supply relies entirely on the energy transferred to the energy storage capacitor by the varistor power supply branch and the capacitor power supply branch. Since there is no physical connection path, the potential changes generated by the power device under high voltage change rate conditions will not form a common-mode current loop in the drive ground.

[0139] This embodiment effectively reduces interference current in the drive power supply circuit and reduces the risk of false triggering in high-frequency, high-voltage-rate-change applications. At the same time, it does not introduce additional structures such as isolation transformers or optocouplers, demonstrating the synergistic advantages of the energy harvesting structure and the electromagnetic compatibility characteristics of the system.

[0140] Example 6: Universal Adaptation Example under Different Power Device Conditions

[0141] This embodiment applies the above power supply structure to different types of power devices. For devices with high voltage change rates, the capacitance ratio of the high-voltage capacitor to the low-voltage capacitor is adjusted to ensure that the capacitor power supply branch obtains sufficient energy during the steady-state phase. For applications with low switching frequencies or long startup times, the varistor voltage is adjusted to ensure that the varistor power supply branch provides sufficient energy support during the startup phase.

[0142] Under different application conditions, the varistor closed-loop voltage is always lower than the capacitor power supply closed-loop voltage, so that the varistor power supply branch only undertakes the start-up function, while the capacitor power supply branch undertakes the steady-state function, thus ensuring the consistency of system behavior.

[0143] like Figure 4The figure shows the simulation results of key node voltages and branch currents in a half-bridge topology according to an embodiment of the present invention, which are used to demonstrate the technical effects of the power extraction scheme described in the present invention during the startup and steady-state operation phases. In the figure, V(3,2) represents the drain-source voltage drop change of the lower MOSFET in the on-state, I(D6) represents the current change of the anti-reverse diode in the voltage-sensitive power extraction branch, and I(D4) represents the current change of the anti-reverse diode in the capacitor power extraction branch.

[0144] Simulation results show that during the initial startup phase, the capacitor-based power supply branch is uncharged because a stable voltage has not yet been established at the output terminal. At this time, the voltage-sensitive power supply branch conducts first and assumes the power supply function, with its branch current I(D6) rapidly rising and stabilizing at approximately 1.4A. This current is primarily used to quickly charge the energy storage capacitor, thus providing the energy required for the startup of the subsequent control and drive units. Therefore, the voltage-sensitive power supply branch can reliably complete energy injection during the startup phase, avoiding the problem of the control system failing to start due to the lack of an established output voltage.

[0145] As the output voltage gradually rises and reaches the threshold condition set by the closed-loop control of the voltage-sensitive power-taking branch, the power-taking process of the voltage-sensitive power-taking branch is effectively suppressed. Its branch current I(D6) gradually decreases and approaches zero, avoiding additional losses to the main power circuit during steady-state operation. At the same time, the capacitor power-taking branch begins to gradually participate in the power-taking process, as shown by I(D4) in the figure. Its current gradually increases and undertakes the task of continuously charging the energy storage capacitor.

[0146] When the voltage of the energy storage capacitor reaches the set value of the closed-loop control of the capacitor power supply branch, the output voltage enters the stable operating range, and the overall circuit operation tends to be balanced. At this time, the voltage-sensitive power supply branch and the capacitor power supply branch work independently according to their respective control conditions, and operate in parallel in a coordinated manner, realizing a natural switching between the power supply path in the startup phase and the steady-state phase. Thus, by introducing mutually independent power supply units, this invention keeps the power supply process of the upper and lower transistors consistent, ensuring startup reliability and reducing steady-state power consumption, verifying the significant technical effects of this invention in terms of stability, efficiency, and engineering applicability.

[0147] 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 device driving power supply system using a hybrid varistor-capacitor power extraction method, characterized in that, It includes a varistor power supply branch, a capacitor power supply branch, an energy storage branch, and a voltage closed-loop control branch; in, The varistor power supply branch includes a first varistor and a second varistor connected in series, with their two ends used to connect to the DC bus and the drive ground, respectively. The capacitor power extraction branch includes a capacitor energy extraction structure formed by a high-voltage capacitor and a low-voltage capacitor connected in series. The high-voltage capacitor is used to couple the voltage change at the high-voltage end of the power device, and the low-voltage capacitor is used to release energy to the drive ground. The energy storage branch includes an energy storage capacitor, which serves as the DC power supply for the driver. The voltage closed-loop control branch includes a first control unit and a second control unit respectively corresponding to the varistor power supply branch and the capacitor power supply branch. The first control unit is used to cut off the varistor power supply branch when the voltage of the energy storage capacitor reaches the preset varistor closed-loop voltage. The second control unit is used to maintain the continuous power supply of the capacitor power supply branch after the power device enters the continuous switching state. The varistor closed-loop voltage is lower than the capacitor power supply closed-loop voltage, so that the varistor power supply branch only participates in power supply during the startup phase and stops working during the steady-state phase.

2. The system according to claim 1, characterized in that, The first control unit includes a first switching transistor, a first voltage regulator unit, and a first voltage divider network. The first voltage divider network samples the voltage of the energy storage capacitor. When the sampled voltage reaches the varistor closed-loop voltage, the first switching transistor enters the cut-off state to cut off the varistor power supply branch.

3. The system according to claim 1, characterized in that, In the capacitor power supply branch, the high-voltage capacitor is a picofarad-level capacitor and the low-voltage capacitor is a nanofarad-level capacitor, which is used to limit transient voltage and smoothly transfer energy to the energy storage capacitor during the switching process of power devices.

4. A half-bridge drive power supply system applying the varistor-capacitor hybrid power extraction mechanism of claim 1, characterized in that, Including the upper arm power supply unit and the lower arm power supply unit; The upper bridge arm power supply unit is connected between the positive terminal of the DC bus and the midpoint of the half-bridge, and the lower bridge arm power supply unit is connected between the midpoint of the half-bridge and the negative terminal of the DC bus. Both the upper arm power supply unit and the lower arm power supply unit include a varistor power extraction branch, a capacitor power extraction branch, an energy storage branch, and a corresponding voltage closed-loop control branch. During the startup phase, the varistor power supply branch of the upper bridge arm power supply unit and the lower bridge arm power supply unit form a series charging circuit to charge their respective energy storage capacitors. When the voltage of one of the energy storage capacitors reaches the closed-loop voltage of the varistor first, the corresponding varistor power extraction branch is cut off, causing the series circuit to be asynchronously cut off. Subsequently, the power devices are turned on to generate a potential change at the midpoint of the half-bridge, so that the power supply unit on the side that has not reached the varistor closed-loop voltage can bear the bus voltage alone and complete the power replenishment. During the continuous switching phase, the capacitor power supply branches of the upper and lower bridge arms respectively take over the power supply and raise their respective energy storage capacitors to the capacitor power supply closed-loop voltage.

5. The system according to claim 4, characterized in that, The upper bridge arm power supply unit and the lower bridge arm power supply unit are symmetrical in circuit structure.

6. The system according to claim 4, characterized in that, During the startup phase, the sum of the first-side varistor closed-loop voltage and the second-side varistor closed-loop voltage must be less than the DC bus voltage.

7. An isolated drive power supply system based on a varistor-capacitor hybrid power source, characterized in that, There is no DC connection between the drive ground and the power side ground, so that the voltage changes generated by the switching of the power device do not form a common-mode current loop. The system provides energy to the energy storage capacitor through the energy harvesting branch without introducing a common-mode coupling path.

8. The system according to claim 7, characterized in that, The power device is a metal-oxide-semiconductor field-effect transistor, a silicon carbide field-effect transistor, a gallium nitride field-effect transistor, or an insulated-gate bipolar transistor.

9. A power device driving power supply method based on varistor-capacitor hybrid power extraction, characterized in that, Includes the following steps: After the DC bus voltage is applied, the energy storage capacitor is started and charged through the varistor power extraction branch; The voltage of the energy storage capacitor is detected, and when the voltage of the energy storage capacitor reaches the preset closed-loop voltage of the varistor, the varistor power extraction branch is cut off. After the power device starts switching, energy is obtained from the voltage change at the high voltage end of the power device using the capacitor power supply branch; The voltage of the energy storage capacitor is increased and stabilized at a voltage higher than the voltage of the varistor closed-loop voltage, which is the capacitor power-taking closed-loop voltage.

10. The method according to claim 9, characterized in that, In a half-bridge structure, the power supply unit on one side first reaches the varistor closed-loop voltage and enters the cutoff state, so that the power supply unit on the other side can complete the power replenishment under the action of the midpoint potential change of the half-bridge.

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