Power supply device and power supply system

Abstract

The invention provides power supply equipment and a power supply system, and belongs to the technical field of circuits. Grid electrodes of two synchronous rectification switch tubes which are connected in parallel in the power supply equipment are respectively connected with a voltage limiting circuit and a current limiting circuit. Wherein the voltage limiting circuit can limit the grid voltage when the grid voltage of the synchronous rectification switch tube connected with the voltage limiting circuit is too high, so that the grid voltage is lower than the withstand voltage upper limit of the grid of the other synchronous rectification switch tube. And the current limiting circuit can limit the current flowing into the output end of the gate driving circuit from the gate of the synchronous rectification switch tube connected with the current limiting circuit. On the basis, when any synchronous rectification switch tube is short-circuited and fails to cause overhigh grid voltage, the protection circuit can effectively lower the voltage of the output end of the grid driving circuit through voltage limiting and current limiting operations. Therefore, passive short-circuit failure of other synchronous rectification switch tubes connected in parallel with the synchronous rectification switch tube with short-circuit failure can be avoided.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and in particular to a power supply device and power supply system. Background Technology

[0002] Power supply equipment (also known as power modules) typically includes alternating current / direct current (AC / DC) conversion circuits and DC / DC conversion circuits.

[0003] A typical DC / DC converter circuit includes a transformer, a primary circuit connected to the primary winding of the transformer, and a secondary circuit connected to the secondary winding of the transformer. The secondary circuit typically includes multiple synchronous rectifier switches connected in parallel. These multiple synchronous rectifier switches are driven by a single gate driver in the power supply unit; that is, the gates of the multiple synchronous rectifier switches are connected to the output of the same gate driver.

[0004] When any synchronous rectifier switch in the secondary circuit fails due to a short circuit, the high voltage between its drain and source will flow through the gate to the output of the gate driver. Since this output is also connected to the gates of other synchronous rectifier switches, it can cause the gates of other synchronous rectifier switches to be mis-conducted or over-voltaged, thereby causing the other synchronous rectifier switches to also fail due to a short circuit. Summary of the Invention

[0005] This application provides a power supply device and power supply system that can solve the technical problem that when a synchronous rectifier switch in a power supply device fails due to a short circuit, other synchronous rectifier switches connected in parallel with it will also fail due to a short circuit.

[0006] In a first aspect, a power supply device is provided, comprising: a DC / DC converter circuit, a gate drive circuit, and a protection circuit. The DC / DC converter circuit includes: a first synchronous rectifier switch and a second synchronous rectifier switch connected in parallel. The protection circuit includes: a first voltage limiting circuit, a second voltage limiting circuit, a first current limiting circuit, and a second current limiting circuit. One end of the first voltage limiting circuit is connected to the gate of the first synchronous rectifier switch, and the other end is grounded. The first voltage limiting circuit limits the gate voltage of the first synchronous rectifier switch when its gate voltage exceeds a first threshold voltage, so that the gate voltage of the first synchronous rectifier switch is lower than the upper withstand voltage limit of the gate of the second synchronous rectifier switch. One end of the second voltage limiting circuit is connected to the gate of the second synchronous rectifier switch, and the other end is grounded. The second voltage limiting circuit limits the gate voltage of the second synchronous rectifier switch when its gate voltage exceeds a second threshold voltage, so that the gate voltage of the second synchronous rectifier switch is lower than the upper withstand voltage limit of the gate of the first synchronous rectifier switch. One end of the first current-limiting circuit is connected to one end of the first voltage-limiting circuit, and the other end of the first current-limiting circuit is connected to the output terminal of the gate drive circuit. The first current-limiting circuit is used to limit the current flowing into the output terminal. One end of the second current-limiting circuit is connected to one end of the second voltage-limiting circuit, and the other end of the second current-limiting circuit is connected to the output terminal of the gate drive circuit. The second current-limiting circuit is used to limit the current flowing into the output terminal.

[0007] Based on the solution provided in this application, when any synchronous rectifier switch in the DC / DC converter circuit fails due to a short circuit, resulting in an excessively high gate voltage, the protection circuit in the power supply can effectively lower the output voltage of the gate drive circuit through voltage limiting and current limiting operations. This prevents other synchronous rectifier switches connected in parallel with the short-circuited switch from also experiencing passive short-circuit failure.

[0008] In one embodiment, the first threshold is higher than the driving voltage of the first synchronous rectifier switch, ensuring that the first voltage limiting circuit does not limit the gate voltage of the first synchronous rectifier switch when the gate driving circuit is driving it normally. This avoids affecting the normal driving of the first synchronous rectifier switch. Furthermore, the first threshold is lower than the upper withstand voltage limit of the gate of the second synchronous rectifier switch, ensuring that the first voltage limiting circuit can limit the gate voltage of the first synchronous rectifier switch in time before the gate voltage reaches this upper withstand voltage limit. This voltage limiting operation ensures that the voltage at the output of the gate driving circuit does not exceed the upper withstand voltage limit of the gate of the second synchronous rectifier switch, thus preventing the second synchronous rectifier switch from failing due to gate overvoltage and achieving effective protection for the second synchronous rectifier switch.

[0009] Similarly, the second threshold is higher than the driving voltage of the second synchronous rectifier switch to ensure that the second voltage limiting circuit will not limit the gate voltage of the second synchronous rectifier switch when the gate drive circuit is driving it normally. This avoids affecting the normal driving of the second synchronous rectifier switch. Furthermore, the second threshold is lower than the upper withstand voltage limit of the gate of the first synchronous rectifier switch to ensure that the second voltage limiting circuit can limit the gate voltage of the second synchronous rectifier switch in time before the gate voltage reaches this upper withstand voltage limit. This voltage limiting operation ensures that the voltage at the output of the gate drive circuit will not exceed the upper withstand voltage limit of the gate of the first synchronous rectifier switch, thus preventing the first synchronous rectifier switch from failing due to gate overvoltage and achieving effective protection for the first synchronous rectifier switch.

[0010] In one embodiment, the protection circuit further includes a third current-limiting circuit and a fourth current-limiting circuit. One end of the first voltage-limiting circuit is connected to the gate of the first synchronous rectifier switch via the third current-limiting circuit, which limits the current flowing into the first voltage-limiting circuit. One end of the second voltage-limiting circuit is connected to the gate of the second synchronous rectifier switch via the fourth current-limiting circuit, which limits the current flowing into the second voltage-limiting circuit.

[0011] The third current-limiting circuit prevents excessive current from flowing through the first voltage-limiting circuit, thus preventing the first voltage-limiting circuit from failing due to excessive power. This ensures effective protection of the output terminal of the gate drive circuit by the first voltage-limiting circuit. The fourth current-limiting circuit prevents excessive current from flowing through the second voltage-limiting circuit, thus preventing the second voltage-limiting circuit from failing due to excessive power. This ensures effective protection of the output terminal of the gate drive circuit by the second voltage-limiting circuit.

[0012] In one embodiment, each of the first, second, third, and fourth current-limiting circuits includes one or more resistors connected in series. Furthermore, the total resistance of the resistors in the third current-limiting circuit is less than the total resistance of the resistors in the first current-limiting circuit, and the total resistance of the resistors in the fourth current-limiting circuit is less than the total resistance of the resistors in the second current-limiting circuit.

[0013] Because resistors have a simple structure and low cost, using them as current-limiting circuits can effectively avoid increasing the cost and structural complexity of power supply equipment. Furthermore, it is understood that the presence of the aforementioned third and fourth current-limiting circuits will cause some loss in the drive voltage output from the gate drive circuit to the gate of the synchronous rectifier switch. Therefore, by designing the total resistance values ​​in both the third and fourth current-limiting circuits to be relatively small, the impact on the drive voltage output of the gate drive circuit can be minimized while effectively protecting the voltage-limiting circuit. In addition, by designing the total resistance values ​​in both the first and second current-limiting circuits to be relatively large, effective current limiting of the current flowing into the gate drive circuit can be achieved. This ensures that, within the current-sinking capability of the gate drive circuit, the output voltage of the gate drive circuit is effectively pulled down below the gate turn-on threshold voltage of the synchronous rectifier switch.

[0014] In one embodiment, the protection circuit further includes a unidirectional conduction circuit and a current sinking circuit. The other ends of the first and second current limiting circuits are connected to the output of the gate driving circuit via the unidirectional conduction circuit, and the conduction direction of the unidirectional conduction circuit is from the output of the gate driving circuit to the first and second current limiting circuits. One end of the current sinking circuit is connected to the other ends of the first and second current limiting circuits, and the other end of the current sinking circuit is grounded. The current sinking circuit is used to discharge the current flowing from the first current limiting circuit or the current flowing from the second current limiting circuit.

[0015] Based on the conduction direction of the aforementioned unidirectional conduction circuit, it is known that this unidirectional conduction circuit can prevent the current flowing from the first current limiting circuit or the second current limiting circuit from flowing into the output terminal of the gate drive circuit. This ensures that the current flowing from both the first and second current limiting circuits can be discharged through the current sinking circuit. Therefore, it can effectively lower the voltage at the output terminal of the gate drive circuit (i.e., it enhances the current sinking capability of the gate drive circuit), thereby effectively reducing the probability of short-circuit failure of the synchronous rectifier switch.

[0016] In one embodiment, the current sinking circuit includes a switching transistor. One end of the switching transistor is connected to the other end of a first current-limiting circuit and the other end of a second current-limiting circuit. The other end of the switching transistor is grounded, and the control terminal of the switching transistor is connected to a gate driving circuit. The gate driving circuit is used to output a signal to turn on the switching transistor when a signal is output to turn off the first and second synchronous rectifier switching transistors. When the switching transistor is turned on, a current discharge path is formed between the other end of the first and second current-limiting circuits and the ground terminal to discharge the current flowing from the first or second current-limiting circuit.

[0017] It is understandable that when the gate drive circuit controls multiple synchronous rectifier switches to be turned off, if none of these synchronous rectifier switches fail due to short circuit, the current discharge path formed by the switches in the current sink circuit will not affect the synchronous rectifier switches. If any synchronous rectifier switch fails due to short circuit, the switch in the current sink circuit can discharge the large short-circuit current. Therefore, by connecting the control terminal (i.e., the gate) of the switch in the current sink circuit to the gate drive circuit and making it controlled by the gate drive circuit, the control complexity of the current sink circuit can be effectively simplified without affecting the normal driving of the synchronous rectifier switches, thereby reducing the design difficulty of the power supply equipment.

[0018] In one embodiment, the switching transistor is a P-type transistor, such as a PNP transistor. Both the first and second synchronous rectifier switches are N-type switches. Furthermore, the signal output by the gate drive circuit to turn off the first and second synchronous rectifier switches is the same signal output by the gate drive circuit to turn on the switches. That is, the gate drive circuit can simultaneously control the on / off state of the first and second synchronous rectifier switches and the switches in the current sinking circuit through a single drive signal; the switches in the current sinking circuit can reuse the drive signals of the first and second synchronous rectifier switches. This further reduces the control complexity of the switches in the current sinking circuit, thereby reducing the design difficulty of the power supply device.

[0019] In one embodiment, the unidirectional conduction circuit includes a diode. The anode of the diode is connected to the output terminal of the gate drive circuit, and the cathode of the diode is connected to the other end of the first current limiting circuit and the other end of the second current limiting circuit.

[0020] The aforementioned connection method based on diodes enables unidirectional current conduction. Furthermore, due to the simple structure and low cost of diodes, it effectively avoids increasing the cost and structural complexity of power supply equipment.

[0021] In one embodiment, each of the first and second voltage limiting circuits includes a transient voltage suppressor (TVS) diode, a Zener diode, or a clamping circuit.

[0022] Using TVS diodes or Zener diodes as voltage limiting circuits ensures a simpler structure, thus avoiding increased cost and structural complexity of the power supply equipment. This clamping circuit, also known as a voltage clamping circuit, can be composed of active devices such as switching transistors, allowing it to withstand higher power and providing better protection.

[0023] In a second aspect, a power supply system is provided, comprising: a plurality of power supply devices as provided in the first aspect above, wherein the output terminals of the plurality of power supply devices are connected in parallel to a DC bus.

[0024] In summary, this application provides a power supply device and a power supply system. The DC / DC conversion circuit in the power supply device includes two synchronous rectifier switches connected in parallel. The protection circuit in the power supply device includes two voltage limiting circuits and two current limiting circuits. Each voltage limiting circuit is connected to the gate of one of the synchronous rectifier switches and can limit the gate voltage of the connected synchronous rectifier switch to be lower than the upper limit of the gate voltage of the other synchronous rectifier switch when the gate voltage of the connected synchronous rectifier switch is too high. Each current limiting circuit is connected to the output terminal of both the voltage limiting circuit and the gate drive circuit, and can limit the current flowing into the output terminal of the gate drive circuit. Therefore, when any synchronous rectifier switch fails due to a short circuit, causing its gate voltage to be too high, the protection circuit can effectively lower the voltage at the output terminal of the gate drive circuit through voltage limiting and current limiting operations. This prevents other synchronous rectifier switches connected in parallel with the short-circuited synchronous rectifier switch from also passively failing due to a short circuit. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a power supply system provided in an embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the structure of a DC / DC conversion circuit provided in an embodiment of this application;

[0027] Figure 3 This is a schematic diagram of a group failure of multiple synchronous rectifier switches in a DC / DC conversion circuit provided in an embodiment of this application;

[0028] Figure 4 This is a schematic diagram of the structure of a power supply device provided in an embodiment of this application;

[0029] Figure 5 This is a schematic diagram of another power supply device provided in an embodiment of this application;

[0030] Figure 6 This is a schematic diagram of the structure of another power supply device provided in the embodiments of this application;

[0031] Figure 7 This is a schematic diagram of another power supply device provided in the embodiments of this application;

[0032] Figure 8 This is a schematic diagram of another power supply device provided in the embodiments of this application;

[0033] Figure 9This is a schematic diagram of another power supply device provided in the embodiments of this application. Detailed Implementation

[0034] The power supply equipment and power supply system provided in the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic diagram of a power supply system provided in an embodiment of this application. For example... Figure 1 As shown, the power system can include multiple power supply devices, the outputs of which can be connected in parallel to a DC bus. The DC bus can also be connected to at least one load, allowing the multiple power supply devices to supply power to that load. By connecting the outputs of multiple power supply devices in parallel to the DC bus, the size of the power system can be effectively reduced, while power density and reliability can be improved. The power supply devices, also called power modules, can be power supply units (PSUs) or uninterruptible power supplies (UPSs), etc. A PSU is also called a rectifier.

[0036] refer to Figure 1 It can be seen that each power supply device may include at least a DC / DC conversion circuit. The output of this DC / DC conversion circuit is connected to a DC bus. The DC / DC conversion circuit is used to isolate and convert the DC power, and then output the converted DC power to the DC bus. Based on Figure 1 As can be seen, the output terminal of a power supply device refers to the output terminal of a DC / DC conversion circuit.

[0037] In one embodiment, such as Figure 1 As shown, each power supply device may also include an AC / DC conversion circuit. The input terminal of this AC / DC conversion circuit is connected to the power grid, and its output terminal is connected to the input terminal of the DC / DC conversion circuit. The AC / DC conversion circuit converts the alternating current (AC) from the power grid into direct current (DC) and outputs it to the DC / DC conversion circuit.

[0038] In power systems, short circuits at the output terminals of power supply equipment, leading to DC bus short circuits, frequently occur due to aging or other reasons. If short circuit faults cannot be quickly isolated, service interruptions can occur; for example, if the load includes communication equipment, communication outages may result. To address short circuit faults in individual power supply units, measures must be implemented to disconnect the faulty device (the one experiencing the short circuit) from the power system to prevent the spread of faults caused by prolonged short circuits.

[0039] Figure 2 This is a schematic diagram of a DC / DC conversion circuit provided in an embodiment of this application. Figure 2As shown, the DC / DC conversion circuit may include a primary-side circuit, a transformer T0, and a secondary-side circuit. The primary-side circuit is connected to the primary side of the transformer T0, and this primary-side circuit may be a half-bridge resonant circuit. For example... Figure 2 As shown, the primary-side circuit can be a half-bridge LLC resonant circuit, where L represents inductance and C represents capacitance. The secondary-side circuit is connected to the secondary side of transformer T0, and can include two sets of switching transistors. Each set of switching transistors includes multiple (e.g., two) synchronous rectification (SR) switching transistors connected in parallel. Each synchronous rectification switching transistor can be a metal-oxide-semiconductor field-effect transistor (MOSFET), or simply a MOS transistor.

[0040] A short circuit at the output of a power supply device is typically caused by a short-circuit failure of the synchronous rectifier MOSFET in the DC / DC converter circuit. To achieve rapid fault isolation, in some embodiments, a power device can be connected in series between the output of the DC / DC converter circuit and the load (i.e., the DC bus). For example, see reference... Figure 2 A reverse polarity protection (ORing) circuit can be connected in series between the output of the DC / DC converter circuit and the load. When the output of the DC / DC converter circuit is short-circuited, the power MOSFET in the ORing circuit can disconnect the output of the DC / DC converter circuit from the load, thus achieving fault isolation. However, connecting power devices in series (such as in an ORing circuit) increases the hardware cost of the power supply equipment. Furthermore, under normal operating conditions, the power devices connected in series in the power loop (such as the power MOSFET in the ORing circuit) will generate significant losses due to their on-resistance, which will reduce the efficiency of the power system and increase heat dissipation costs, impacting the capital expenditure (CPEX) and operating expense (OPEX) of a single site.

[0041] To avoid the increased cost and reduced efficiency caused by connecting power devices in series, in some embodiments, the power supply device can achieve fault isolation through software control. In this software control method, when the power supply device in the power system detects a short circuit on the DC bus, it can expand the current, i.e., output a large instantaneous current. This large instantaneous current is also called the short-circuit output current. If the sum of the short-circuit output currents of other power supply devices connected in parallel with the faulty device in the power system is large enough, the short circuit point in the faulty device can be broken, i.e., the short circuit point is disconnected. Here, the short circuit point in the faulty device can refer to the pin of the short-circuited synchronous rectifier MOSFET in the faulty device. After the short circuit point of the faulty device is broken, the faulty device is isolated from the power system, the short circuit fault of the power system is eliminated, and it can continue to operate normally.

[0042] Furthermore, the short-circuit failure of one synchronous rectifier MOSFET in a power supply device typically leads to the passive short-circuit failure of other synchronous rectifier MOSFETs, resulting in a cluster of short-circuit failures of synchronous rectifier MOSFETs in the power supply device. For example, refer to... Figure 3 Q1 and Q2 are two synchronous rectifier MOSFETs connected in parallel in the power supply. The gates of these two MOSFETs are connected to and driven by the same gate driver circuit. This gate driver circuit is also called a gate driver or power driver. When both Q1 and Q2 are off, after Q1 fails due to a short circuit, the high voltage from Q1's drain-source (DS) flows through the drain-gate (DG) into Q1's gate, and then into the output of the gate driver circuit. Since the gate driver circuit has limited current sinking capability, typically 4 amperes (A) to 5 A, the output voltage of the gate driver circuit will exceed the gate turn-on threshold voltage of Q2. This can cause Q2 to mis-turn on or even experience gate overvoltage, resulting in a passive short-circuit failure of Q2.

[0043] Based on device design and experimental verification, the parallel pins of multiple synchronous rectifier MOSFETs have a high current withstand capability. Therefore, if a group of synchronous rectifier MOSFETs fail in a power supply device, and the number of other power supply devices connected in parallel to the failed device is small, the combined external current from these other power supply devices may not be sufficient to break the parallel pins of the failed synchronous rectifier MOSFETs, thus failing to achieve fault isolation.

[0044] This application provides a power supply device that can protect other parallel synchronous rectifier MOSFETs after a single synchronous rectifier MOSFET fails due to a short circuit, thus preventing other synchronous rectifier MOSFETs from passively failing due to short circuits. In other words, this power supply device can effectively prevent multiple synchronous rectifier MOSFETs from failing in clusters. Therefore, it can be ensured that when a short circuit occurs in one power supply device in the power system, the combined external current from other power supply devices can break the pins of the short-circuited synchronous rectifier MOSFET in the faulty device, achieving rapid fault isolation.

[0045] like Figure 4 As shown, the power supply device provided in this embodiment includes: a DC / DC converter circuit 10, a gate drive circuit 20, and a protection circuit 30. The DC / DC converter circuit 10 includes: a first synchronous rectifier switch Q1 and a second synchronous rectifier switch Q2 connected in parallel. The protection circuit 30 includes: a first voltage limiting circuit 301, a second voltage limiting circuit 302, a first current limiting circuit 303, and a second current limiting circuit 304.

[0046] In this circuit, one end of the first voltage limiting circuit 301 is connected to the gate of the first synchronous rectifier switch Q1, and the other end is grounded to GND. The first voltage limiting circuit 301 limits the gate voltage of the first synchronous rectifier switch Q1 when its gate voltage exceeds a first threshold, ensuring that the gate voltage of Q1 is below the upper limit of the gate withstand voltage of the second synchronous rectifier switch Q2. This prevents the second synchronous rectifier switch Q2 from failing due to gate overvoltage, thus effectively protecting it.

[0047] One end of the second voltage limiting circuit 302 is connected to the gate of the second synchronous rectifier switch Q2, and the other end is grounded to GND. This second voltage limiting circuit 302 is used to limit the gate voltage of the second synchronous rectifier switch Q2 when its gate voltage exceeds a second threshold, so that the gate voltage of the second synchronous rectifier switch Q2 is lower than the upper withstand voltage limit of the gate of the first synchronous rectifier switch Q1. This prevents the first synchronous rectifier switch Q1 from failing due to gate overvoltage, thus effectively protecting the first synchronous rectifier switch Q1.

[0048] One end of the first current limiting circuit 303 is connected to one end of the first voltage limiting circuit 301, and the other end of the first current limiting circuit 303 is connected to the output terminal of the gate driving circuit 20. The first current limiting circuit 303 is used to limit the current flowing into the output terminal, thereby pulling down the voltage of the output terminal of the gate driving circuit 20.

[0049] One end of the second current limiting circuit 304 is connected to one end of the second voltage limiting circuit 302, and the other end of the second current limiting circuit 304 is connected to the output terminal of the gate driving circuit 20. The second current limiting circuit 304 is used to limit the current flowing into the output terminal, thereby pulling down the voltage of the output terminal of the gate driving circuit 20.

[0050] Understandably, in the scenario where the first synchronous rectifier switch Q1 fails due to a short circuit, causing its gate voltage to be higher than the output voltage of the gate drive circuit 20, the first current limiting circuit 303 limits the current flowing into the output of the gate drive circuit 20, thereby lowering the output voltage of the gate drive circuit 20. For example, it can make the output voltage of the gate drive circuit 20 lower than the gate turn-on threshold voltage of the second synchronous rectifier switch Q2. This prevents the second synchronous rectifier switch Q2 from failing due to mis-turn-on.

[0051] In the scenario where the second synchronous rectifier switch Q2 fails due to a short circuit, causing its gate voltage to exceed the output voltage of the gate drive circuit 20, the second current limiting circuit 304 limits the current flowing into the output of the gate drive circuit 20, thereby lowering the output voltage. For example, it can make the output voltage of the gate drive circuit 20 lower than the turn-on threshold voltage of the gate of the first synchronous rectifier switch Q1. This prevents the first synchronous rectifier switch Q1 from failing due to mis-turn-on.

[0052] Specifically, the upper limit of the gate withstand voltage of the first synchronous rectifier switch Q1 can be equal to the upper limit of the gate withstand voltage of the second synchronous rectifier switch Q2, and the turn-on threshold voltage of the gate of the first synchronous rectifier switch Q1 can be equal to the turn-on threshold voltage of the gate of the second synchronous rectifier switch Q2. That is, the upper limit of the gate withstand voltage of multiple synchronous rectifier switches connected in parallel can be equal, and the turn-on threshold voltage of their gates can be equal.

[0053] Of course, the upper limit of the gate withstand voltage of the multiple parallel synchronous rectifier switches can be different, and the turn-on threshold voltage of the gates of the multiple parallel switches can also be different. For example, considering the device tolerance, the turn-on threshold voltage of the gates of the multiple parallel synchronous rectifier switches can not be exactly the same, but they are all within a certain voltage range. For example, this voltage range can be 2.5V to 3.5V.

[0054] In this embodiment, when any synchronous rectifier switch fails due to a short circuit, resulting in high voltage being injected into its gate, the voltage limiting circuit connected to it limits its gate voltage to ensure that the gate voltage is less than the upper limit of the gate withstand voltage of the other synchronous rectifier switch. This effectively prevents overvoltage breakdown of the gate of the other synchronous rectifier switch connected in parallel with the short-circuited synchronous rectifier switch. Therefore, the probability of the other synchronous rectifier switch in parallel experiencing a passive short circuit failure can be effectively reduced. In other words, the probability of multiple synchronous rectifier switches in parallel failing together due to a single synchronous rectifier switch short-circuiting can be effectively reduced.

[0055] Understandably, after the first voltage limiting circuit 301 limits the gate voltage of the first synchronous rectifier switch Q1, the gate voltage of the first synchronous rectifier switch Q1 can be higher than the normal drive voltage of the second synchronous rectifier switch Q2. Furthermore, after the second voltage limiting circuit 302 limits the gate voltage of the second synchronous rectifier switch Q2, the gate voltage of the second synchronous rectifier switch Q2 will be higher than the normal drive voltage of the first synchronous rectifier switch Q1. Therefore, the voltage limiting operations of the first voltage limiting circuit 301 and the second voltage limiting circuit 302 can be prevented from affecting the normal driving of the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2 by the gate drive circuit 20.

[0056] It can also be understood that the first current limiting circuit 303 and the second current limiting circuit 304 mentioned above can be current limiting circuits of the gate driving circuit 20. These two current limiting circuits can effectively reduce the current flowing through the gate driving circuit 20 by limiting the current flowing into the output terminal of the gate driving circuit 20. Consequently, the voltage at the output terminal of the gate driving circuit 20 can be effectively reduced. Thus, it can be ensured that after any synchronous rectifier switch fails due to a short circuit, the voltage at the output terminal of the gate driving circuit 20 can be much lower than the gate voltage of the short-circuited synchronous rectifier switch. Alternatively, it can be understood that the first current limiting circuit 303 and the second current limiting circuit 304 can further reduce the voltage at the output terminal of the gate driving circuit 20 within the current sinking capability of the gate driving circuit 20, ensuring that the voltage at its output terminal is much lower than the turn-on threshold voltage of the gate of the other synchronous rectifier switch connected in parallel with the short-circuited synchronous rectifier switch. Therefore, after any synchronous rectifier switch fails due to a short circuit, it can effectively prevent the other synchronous rectifier switch connected in parallel with the short-circuited synchronous rectifier switch from being mistakenly turned on, thereby preventing the other synchronous rectifier switch connected in parallel from being passively short-circuited due to mistakenly turned on.

[0057] Based on the above analysis, in the DC / DC conversion circuit 10 of the power supply device, if a single synchronous rectification switch tube fails due to a short circuit, the above protection circuit 30 can effectively reduce the voltage at the output end of the gate drive circuit 20 by means of voltage limiting and current limiting, thereby effectively preventing other synchronous rectification switch tubes connected in parallel with the short-circuited and failed synchronous rectification switch tube from being passively short-circuited and failed. For example, it can prevent other synchronous rectification switch tubes connected in parallel from being passively short-circuited and failed due to overvoltage or mis-conduction of the gate. Correspondingly, other power supply devices connected in parallel on the DC bus can flush off the pins of the short-circuited and failed synchronous rectification switch tube by means of jointly expanding the current externally, so as to achieve fault isolation.

[0058] For example, Figure 4 As shown, when both the first synchronous rectification switch tube Q1 and the second synchronous rectification switch tube Q2 are turned off, if the first synchronous rectification switch tube Q1 fails due to a short circuit, the high voltage V1 (greater than the first threshold) between the drain and source of the first synchronous rectification switch tube Q1 is poured into the gate of the first synchronous rectification switch tube Q1 through the drain and gate. The first voltage limiting circuit 301 can limit the gate voltage of the first synchronous rectification switch tube Q1 to V2, where V2 << V1. Moreover, V2 is less than the upper limit of the withstand voltage of the gate of the second synchronous rectification switch tube Q2 and higher than the normal drive voltage of the second synchronous rectification switch tube Q2. The first current limiting circuit 303 can limit the current flowing from the gate of the first synchronous rectification switch tube Q1 to the output end of the gate drive circuit 20, and pull down the voltage at the output end of the gate drive circuit 20 to V3, where V3 << V2 and V3 is much lower than the gate turn-on threshold voltage of the second synchronous rectification switch tube Q2. Thus, it can effectively prevent the second synchronous rectification switch tube Q2 from being passively short-circuited and failed due to overvoltage or mis-conduction of the gate.

[0059] It can be understood that the above voltages V1, V2, and V3 can be designed according to the selection of the synchronous rectification switch tube. For example, assume that the upper limit of the withstand voltage of the gate of the synchronous rectification switch tube is 20V, the normal drive voltage of the gate is 10V, and the gate turn-on threshold voltage Vth is 2.5V. Then the above high voltage V1 may be higher than 80V. The first voltage limiting circuit 301 can limit the gate voltage of the first synchronous rectification switch tube Q1 to V2, where V2 can be less than 15V and higher than 10V. The first current limiting circuit 303 can pull down the voltage at the output end of the gate drive circuit 20 to V3, where V3 can be less than 1V.

[0060] In summary, this application provides a power supply device whose DC / DC conversion circuit includes two synchronous rectifier switches connected in parallel. The protection circuit in the power supply device includes two voltage limiting circuits and two current limiting circuits. Each voltage limiting circuit is connected to the gate of one synchronous rectifier switch and can limit the gate voltage of the connected synchronous rectifier switch to be lower than the upper limit of the gate voltage of the other synchronous rectifier switch when the gate voltage is too high. Each current limiting circuit is connected to the output of both the voltage limiting circuit and the gate drive circuit and can limit the current flowing into the output of the gate drive circuit. Therefore, when any synchronous rectifier switch fails due to a short circuit, resulting in an excessively high gate voltage, the protection circuit can effectively lower the voltage at the output of the gate drive circuit through voltage and current limiting operations. This prevents other synchronous rectifier switches connected in parallel with the short-circuited synchronous rectifier switch from also experiencing passive short-circuit failure.

[0061] Furthermore, since the protection circuit in the power supply equipment can effectively prevent multiple synchronous rectifier switches connected in parallel in the DC / DC conversion circuit from short-circuiting and failing in a group, even if the number of other power supply equipment connected in parallel on the DC bus is small (for example, only one other power supply equipment is connected in parallel), the other power supply equipment connected in parallel can also break the pin of the short-circuited synchronous rectifier switch by expanding the current to achieve fault isolation.

[0062] In one embodiment, the first threshold can be higher than the driving voltage of the first synchronous rectifier switch Q1 to ensure that the first voltage limiting circuit 301 does not limit the gate voltage of the first synchronous rectifier switch Q1 when the gate driving circuit 20 is driving it normally. This avoids affecting the normal driving of the first synchronous rectifier switch Q1. Furthermore, the first threshold can be lower than the upper withstand voltage limit of the gate of the second synchronous rectifier switch Q2 to ensure that the first voltage limiting circuit 301 can limit the gate voltage of the first synchronous rectifier switch Q1 in time before the gate voltage reaches this upper withstand voltage limit. This voltage limiting operation ensures that the voltage at the output of the gate driving circuit 20 does not exceed the upper withstand voltage limit of the gate of the second synchronous rectifier switch Q2, thereby preventing the second synchronous rectifier switch Q2 from failing due to gate overvoltage and achieving effective protection for the second synchronous rectifier switch Q2.

[0063] Similarly, the second threshold can be higher than the driving voltage of the second synchronous rectifier switch Q2 to ensure that the second voltage limiting circuit 302 will not limit the gate voltage of the second synchronous rectifier switch Q2 when the gate driving circuit 20 is driving the second synchronous rectifier switch Q2 normally. This avoids affecting the normal driving of the second synchronous rectifier switch Q2. Furthermore, the second threshold can be lower than the upper withstand voltage limit of the gate of the first synchronous rectifier switch Q1 to ensure that the second voltage limiting circuit 302 can limit the gate voltage of the second synchronous rectifier switch Q2 in time before the gate voltage reaches this upper withstand voltage limit. This voltage limiting operation ensures that the voltage at the output of the gate driving circuit 20 will not exceed the upper withstand voltage limit of the gate of the first synchronous rectifier switch Q1, thereby preventing the first synchronous rectifier switch Q1 from failing due to gate overvoltage and achieving effective protection for the first synchronous rectifier switch Q1.

[0064] It is understood that the aforementioned first threshold can also be referred to as the operating voltage or clamping voltage of the first voltage limiting circuit 301, and the aforementioned second threshold can also be referred to as the operating voltage or clamping voltage of the second voltage limiting circuit 302. The operating voltage of the voltage limiting circuit can refer to the voltage that can trigger the voltage limiting circuit to perform voltage limiting operation.

[0065] In one embodiment, such as Figure 5 As shown, the protection circuit 30 may further include a third current-limiting circuit 305 and a fourth current-limiting circuit 306. One end of the first voltage-limiting circuit 301 is connected to the gate of the first synchronous rectifier switch Q1 via the third current-limiting circuit 305. The third current-limiting circuit 305 is used to limit the current flowing into the first voltage-limiting circuit 301, that is, to limit the current between the gate of the first synchronous rectifier switch Q1 and the first node P1. Figure 4 and Figure 5 As shown, the first node P1 is the connection node between one end of the first voltage limiting circuit 301 and one end of the first current limiting circuit 303.

[0066] One end of the second voltage limiting circuit 302 is connected to the gate of the second synchronous rectifier switch Q2 through the fourth current limiting circuit 306. The fourth current limiting circuit 306 is used to limit the current flowing into the second voltage limiting circuit 302, that is, to limit the current between the gate of the second synchronous rectifier switch Q2 and the second node P2. Figure 4 and Figure 5 As shown, the second node P2 is the connection node between one end of the second voltage limiting circuit 302 and one end of the second current limiting circuit 304.

[0067] It is understandable that the third current limiting circuit 305 can be a current limiting circuit of the first voltage limiting circuit 301. By limiting the current between the gate of the first synchronous rectifier switch Q1 and the first node P1, it can prevent the current flowing through the first voltage limiting circuit 301 from being too large. Therefore, it can prevent the first voltage limiting circuit 301 from failing due to excessive power, and thus ensure the effective protection of the output terminal of the gate drive circuit 20 by the first voltage limiting circuit 301. The fourth current limiting circuit 306 can be a current limiting circuit of the second voltage limiting circuit 302. By limiting the current between the gate of the second synchronous rectifier switch Q2 and the second node P2, it can prevent the current flowing through the second voltage limiting circuit 302 from being too large, and thus prevent the second voltage limiting circuit 302 from failing due to excessive power. Therefore, it can ensure the effective protection of the output terminal of the gate drive circuit 20 by the second voltage limiting circuit 302.

[0068] Furthermore, if the current flowing through the third current limiting circuit 305 is too large after the first synchronous rectifier switch Q1 fails due to a short circuit, causing the third current limiting circuit 305 to experience overpower, then the third current limiting circuit 305 will fail open-circuit. After the third current limiting circuit 305 fails open-circuit, it isolates the short-circuited first synchronous rectifier switch Q1 from the output terminal of the gate drive circuit 20 and from other synchronous rectifier switches, and effectively prevents the first voltage limiting circuit 301 from failing open-circuit due to overpower. Similarly, if the current flowing through the fourth current limiting circuit 306 is too large after the second synchronous rectifier switch Q2 fails due to a short circuit, causing the fourth current limiting circuit 306 to experience overpower, then the fourth current limiting circuit 306 will fail open-circuit. After the fourth current limiting circuit 306 fails to open, it can isolate the short-circuited second synchronous rectifier switch Q2 from the output terminal of the gate drive circuit 20 and from other synchronous rectifier switches, and can effectively prevent the second voltage limiting circuit 302 from failing to open due to overpower.

[0069] Figure 6 This is a schematic diagram of another power supply device provided in an embodiment of this application. For example... Figure 6 As shown, the first voltage limiting circuit 301 may include a first TVS diode D1. The second voltage limiting circuit 302 may include a second TVS diode D2.

[0070] refer to Figure 6As can be seen, the anodes of both the first TVS diode D1 and the second TVS diode D2 are grounded. The cathode of the first TVS diode D1 is connected to the first node P1, and the cathode of the second TVS diode D2 is connected to the second node P2. The breakdown voltage of the first TVS diode is the operating voltage of the first voltage limiting circuit 301, i.e., the first threshold voltage. The breakdown voltage of the second TVS diode is the operating voltage of the second voltage limiting circuit 302, i.e., the second threshold voltage. Therefore, the breakdown voltage of the first TVS diode D1 can be higher than the normal gate drive voltage of the first synchronous rectifier switch Q1, and lower than the upper limit of the gate withstand voltage of the second synchronous rectifier switch Q2. Similarly, the breakdown voltage of the second TVS diode D2 can be higher than the normal gate drive voltage of the second synchronous rectifier switch Q2, and lower than the upper limit of the gate withstand voltage of the first synchronous rectifier switch Q1.

[0071] Based on the above design, it can be ensured that when the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2 are operating normally, both the first TVS diode D1 and the second TVS diode D2 are in the off state, thus avoiding affecting the normal operation of the two synchronous rectifier switches. When the first synchronous rectifier switch Q1 fails due to a short circuit and a high voltage is injected into its gate, if this high voltage is higher than the breakdown voltage of the first TVS diode D1, the first TVS diode D1 will undergo avalanche breakdown, pulling down the voltage at the first node P1. This effectively protects the second synchronous rectifier switch Q2. Similarly, when the second synchronous rectifier switch Q2 fails due to a short circuit and a high voltage is injected into its gate, if this high voltage is higher than the breakdown voltage of the second TVS diode D2, the second TVS diode D2 will undergo avalanche breakdown, pulling down the voltage at the second node P2. This effectively protects the first synchronous rectifier switch Q1.

[0072] In one embodiment, the first voltage limiting circuit 301 can be implemented using a TVS diode or other passive devices (such as Zener diodes). Since passive devices have simple structures and low costs, this effectively avoids increasing the structural complexity and cost of the power supply equipment. Alternatively, the first voltage limiting circuit 301 may include a clamping circuit (also called a voltage clamping circuit). This clamping circuit can be an active clamping circuit composed of active devices such as MOSFETs, which can withstand higher power and provides better protection.

[0073] Similarly, the second voltage limiting circuit 302 can be implemented using a TVS diode or other passive devices (such as a Zener diode). Alternatively, the second voltage limiting circuit 302 may include a clamping circuit, which can be an active clamping circuit composed of active devices such as MOSFETs.

[0074] In one embodiment, each of the first current limiting circuit 303, the second current limiting circuit 304, the third current limiting circuit 305, and the fourth current limiting circuit 306 may include a resistor or multiple resistors connected in series.

[0075] For example, refer to Figure 6 The third current limiting circuit 305 may include a first resistor R1. The first resistor R1 is connected in series between the gate of the first synchronous rectifier switch Q1 and the first node P1, and is used to limit the current between the gate of the first synchronous rectifier switch Q1 and the first node P1. The fourth current limiting circuit 306 may include a second resistor R2. The second resistor R2 is connected in series between the gate of the second synchronous rectifier switch Q2 and the second node P2, and is used to limit the current between the gate of the second synchronous rectifier switch Q2 and the second node P2.

[0076] The first current-limiting circuit 303 may include a third resistor R3. The third resistor R3 is connected in series between the first node P1 and the output terminal of the gate driving circuit 20, and is used to limit the current between the first node P1 and the output terminal of the gate driving circuit 20. The second current-limiting circuit 304 may include a fourth resistor R4. The fourth resistor R4 is connected in series between the second node P2 and the output terminal of the gate driving circuit 20, and is used to limit the current between the second node P2 and the output terminal of the gate driving circuit 20.

[0077] Using resistors to form each current-limiting circuit can effectively avoid increasing the structural complexity and cost of the power supply equipment. Furthermore, it is understood that each of the aforementioned first current-limiting circuit 303, second current-limiting circuit 304, third current-limiting circuit 305, and fourth current-limiting circuit 306 can also be implemented in other ways; for example, each current-limiting circuit can also include multiple resistors connected in parallel.

[0078] In one embodiment, the total resistance of the resistors included in the third current limiting circuit 305 may be less than the total resistance of the resistors included in the first current limiting circuit 303. Furthermore, the total resistance of the resistors included in the fourth current limiting circuit 306 is less than the total resistance of the resistors included in the second current limiting circuit 304.

[0079] For example, in Figure 6 In the structure shown, the resistance of the first resistor R1 is less than the resistance of the third resistor R3, and the resistance of the second resistor R2 is less than the resistance of the fourth resistor R4. The resistances of the first resistor R1 and the second resistor R2 can be equal, for example, both less than 5 ohms, or both 1 ohm. The resistances of the third resistor R3 and the fourth resistor R4 can be equal, for example, both tens of ohms.

[0080] It is understandable that the presence of the first resistor R1 and the second resistor R2 will cause some loss in the drive voltage output from the gate drive circuit 20 to the gate of the synchronous rectifier switch. Therefore, by designing the resistance values ​​of the first resistor R1 and the second resistor R2 to be relatively small, the impact on the drive voltage can be minimized while effectively protecting the voltage limiting circuit.

[0081] Furthermore, by designing the resistance values ​​of the third resistor R3 and the fourth resistor R4 to be relatively large, effective current limiting can be achieved for the current flowing into the gate drive circuit 20. This ensures that, within the current sinking capability of the gate drive circuit 20, the voltage at the output of the gate drive circuit 20 is effectively pulled down below the gate turn-on threshold voltage of the synchronous rectifier switch.

[0082] The above description uses the example of a DC / DC converter circuit 10 containing two synchronous rectifier switches (Q1 and Q2) connected in parallel. It can also be understood that the number n of synchronous rectifier switches connected in parallel in the DC / DC converter circuit 10 can be greater than 2. For example, n can be 3, meaning the DC / DC converter circuit 10 can also include another synchronous rectifier switch connected in parallel with Q1 and Q2. Correspondingly, the protection circuit 30 can include n first-type current-limiting circuits (such as the third current-limiting circuit 305 and the fourth current-limiting circuit 306) corresponding one-to-one with the n synchronous rectifier switches, each first-type current-limiting circuit connected in series between the gate of a corresponding synchronous rectifier switch and a corresponding node. The protection circuit 30 can also include n voltage-limiting circuits corresponding one-to-one with the n synchronous rectifier switches, each voltage-limiting circuit connected between a corresponding node and ground. The protection circuit 30 may also include n second-type current limiting circuits (such as the first current limiting circuit 303 and the second current limiting circuit 302) corresponding one-to-one with the n synchronous rectifier switches, with each second-type current limiting circuit connected in series between a corresponding node and the output terminal of the gate drive circuit 20.

[0083] Based on the above design, it can be ensured that if any one of the n parallel synchronous rectifier switches fails due to a short circuit, the other n-1 synchronous rectifier switches can be effectively protected, thus preventing the n parallel synchronous rectifier switches from failing in a group.

[0084] Figure 7 This is a schematic diagram of another power supply device provided in an embodiment of this application. For example... Figure 7As shown, in one embodiment, the protection circuit 30 may further include a unidirectional conduction circuit 307 and a current sinking circuit 308. The other end of the first current limiting circuit 303 and the other end of the second current limiting circuit 304 are connected to the output terminal of the gate driving circuit 20 via the unidirectional conduction circuit 307, and the conduction direction of the unidirectional conduction circuit 307 is from the output terminal of the gate driving circuit 20 to the first current limiting circuit 303 and the second current limiting circuit 304.

[0085] like Figure 7 As shown, assuming the connection node between the other end of the first current limiting circuit 303 and the other end of the second current limiting circuit 304 is the third node P3, then the unidirectional conduction circuit 307 is connected between the output terminal of the gate driving circuit 20 and the third node P3. Furthermore, the conduction direction of the unidirectional conduction circuit 307 is from the output terminal to the third node P3. That is, the unidirectional conduction circuit 307 only allows current to flow from the output terminal of the first gate driving circuit 20 to the third node P3, and does not allow current to flow from the third node P3 to the output terminal of the first gate driving circuit 20.

[0086] One end of the current sinking circuit 308 is connected to the other end of the first current limiting circuit 303 and the other end of the second current limiting circuit 304, and the other end of the current sinking circuit 308 is grounded. The current sinking circuit 308 is used to discharge the current flowing out of the first current limiting circuit 303 or the current flowing out of the second current limiting circuit 304. That is, the current sinking circuit 308 is connected between the third node P3 and the ground terminal GND, and can discharge the current at the third node P3.

[0087] In one embodiment, the current sinking circuit 308 can form a current discharge path between the third node P3 and the ground terminal when both the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2 are turned off, to discharge the current flowing from the first current limiting circuit 303 or the second current limiting circuit 304 to the third node P3. Alternatively, the current sinking circuit 308 can form a current discharge path between the third node P3 and the ground terminal when either synchronous rectifier switch fails due to a short circuit (e.g., when the gate voltage of either synchronous rectifier switch is higher than a threshold), to discharge the current flowing from the first current limiting circuit 303 or the second current limiting circuit 304 to the third node P3.

[0088] Furthermore, when both the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2 are normally turned on, the current sinking circuit 308 is in an open circuit state. That is, the current sinking circuit 308 will not form a current discharge path between the third node P3 and the ground terminal, so as to avoid affecting the normal operation of the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2.

[0089] Understandably, based on the unidirectional conduction characteristic of the unidirectional conduction circuit 307, the current flowing from the gate of the synchronous rectifier switch through the first current limiting circuit 303 or the second current limiting circuit 304 (i.e., the current at the third node P3) can be prevented from flowing into the output terminal of the gate drive circuit 20. Furthermore, this ensures that the current at the third node P3 can be discharged through the current sinking circuit 308. This effectively improves the current sinking capability of the gate drive circuit 20, thereby effectively reducing the resistance values ​​selected in the first current limiting circuit 303 and the second current limiting circuit 304, and thus reducing the impact on the turn-on and turn-off drive of the synchronous rectifier switch.

[0090] It is also understandable that if the resistance values ​​in the first current limiting circuit 303 and the second current limiting circuit 304 are too large, then because the resistors in the first current limiting circuit 303 and the third current limiting circuit 305 are connected in series to the gate of the first synchronous rectifier switch Q1, and the resistors in the second current limiting circuit 304 and the fourth current limiting circuit 306 are connected in series to the gate of the second synchronous rectifier switch Q2, the gate-source capacitance between the gate and source of each of the two synchronous rectifier switches will be large. The process of the gate driving circuit 20 driving the synchronous rectifier switch to conduct is equivalent to charging this gate-source capacitance; the process of the gate driving circuit 20 driving the synchronous rectifier switch to turn off is equivalent to discharging this gate-source capacitance. An excessively large gate-source capacitance of the synchronous rectifier switch will lead to an increase in both the turn-on delay and the turn-off delay of the synchronous rectifier switch. Based on the above analysis, it can be seen that by adding the current sinking circuit 308 and reducing the resistance values ​​of the resistors in the first current limiting circuit 303 and the second current limiting circuit 304, the impact on the driving delay of the synchronous rectifier switching transistor can be effectively reduced.

[0091] In one embodiment, such as Figure 7 As shown, the current sinking circuit 308 can also be connected to the output terminal of the gate drive circuit 20 and can be controlled by the gate drive circuit 20. For example, the gate drive circuit 20 can be used to output a signal that activates the current sinking circuit 308 when it outputs a signal that turns off the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2. The activation of the current sinking circuit 308 can mean that a current discharge path is formed between the third node P3 and the ground terminal GND. That is, the gate drive circuit 20 can synchronously control the activation of the current sinking circuit 308 when all the parallel synchronous rectifier switches are turned off. Therefore, it can be ensured that when any synchronous rectifier switch fails due to a short circuit, the large short-circuit current flowing from the gate of the failed synchronous rectifier switch through the first current limiting circuit 303 or the second current limiting circuit 304 can be discharged through the activated current sinking circuit 308.

[0092] Furthermore, when the gate drive circuit 20 outputs a signal that turns on both the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2, the gate drive circuit 20 can control the current sinking circuit 308 to not take effect, that is, control the current sinking circuit 308 to not form a current discharge path between the third node P3 and the ground terminal.

[0093] In one embodiment, Figure 8 This is a schematic diagram of another power supply device provided in an embodiment of this application. For example... Figure 8 As shown, the current sinking circuit 308 may include a switching transistor T1. One end of the switching transistor T1 is connected to the other end of the first current limiting circuit 303 and the other end of the second current limiting circuit 304, that is, one end of the switching transistor T1 is connected to the third node P3, and the other end of the switching transistor T1 is grounded. Furthermore, the control terminal of the switching transistor T1 is connected to the gate drive circuit 20. The gate drive circuit 20 is used to output a signal to turn on the switching transistor T1 when it outputs a signal to turn off the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2. It can be understood that after the switching transistor T1 is turned on, a current discharge path is formed between the third node P3 and the ground terminal, thereby discharging the current flowing from the first current limiting circuit 303 or the second current limiting circuit 304.

[0094] For example, such as Figure 8 As shown, the switching transistor T1 in the current sinking circuit 308 can be a transistor. The base of the transistor T1 is connected to the output terminal of the gate drive circuit 20, the emitter of the transistor T1 is connected to the third node P3, and the collector of the transistor T1 is connected to the ground terminal GND. Of course, besides a transistor, the switching transistor T1 in the current sinking circuit 308 can also be implemented using other similar devices, for example, a MOSFET (such as a P-type MOSFET).

[0095] It is understandable that when the gate drive circuit 20 outputs a signal that turns off multiple synchronous rectifier switches, if none of the synchronous rectifier switches fail due to short circuit, the conduction of switch T1 will not affect the synchronous rectifier switches. If any synchronous rectifier switch fails due to short circuit, the conducting switch T1 can discharge the large short-circuit current. Therefore, by connecting the control terminal (i.e., the gate) of the switch in the current sinking circuit 308 to the gate drive circuit 20 and making it controllable by the gate drive circuit 20, the control complexity of the current sinking circuit 308 can be effectively simplified without affecting the normal driving of the synchronous rectifier switches, thereby reducing the design difficulty of the power supply equipment.

[0096] Furthermore, after outputting a signal to turn on all the synchronous rectifier switches, if the gate drive circuit 20 detects a short-circuit failure in any of the synchronous rectifier switches, it can output a signal to turn off all the synchronous rectifier switches, thereby controlling the multiple synchronous rectifier switches to turn off. Correspondingly, the gate drive circuit 20 can output a signal to turn on switch T1, thereby turning on switch T1 and discharging the large short-circuit current.

[0097] In one embodiment, the switching transistor T1 in the current sinking circuit 308 can be a P-type switching transistor, such as a PNP transistor. The first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2 are both N-type switching transistors, such as N-type MOSFETs. Furthermore, the signal output by the gate drive circuit 20 that turns off the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2 is the same signal output by the gate drive circuit 20 that turns the switching transistors on.

[0098] Since the type of switch T1 is different from that of the synchronous rectifier switch (also known as the opposite polarity), the signal output by the gate drive circuit 20 for turning off the synchronous rectifier switch (e.g., a low-level signal) can control the switch T1 to turn on. Conversely, the signal output by the gate drive circuit 20 for turning on the synchronous rectifier switch (e.g., a high-level signal) can control the switch T1 to turn off. Based on this, the gate drive circuit 20 can simultaneously control the on / off states of the first synchronous rectifier switch Q1, the second synchronous rectifier switch Q2, and the switch T1 in the current sink circuit 308 through a single drive signal. That is, the switch T1 in the current sink circuit 308 can reuse the drive signals of the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2. Therefore, without affecting the normal driving of the synchronous rectifier switch, the control complexity of the switch T1 in the current sink circuit 308 can be further reduced, thereby reducing the design difficulty of the power supply equipment.

[0099] Furthermore, as mentioned above, the current sinking circuit 308 can also activate when any synchronous rectifier switch fails due to a short circuit. That is, the current sinking circuit 308 can operate independently of the gate drive circuit 20, and its activation state is unrelated to the on / off state of the synchronous rectifier switch. It can also be understood that the current limiting circuits in the protection circuit 30 (such as the first current limiting circuit 303 to the fourth current limiting circuit 306) can remain active when the synchronous rectifier switch is on and off, i.e., they all perform current limiting operations. The first voltage limiting circuit 301 and the second voltage limiting circuit 302 can activate when the gate voltage of the synchronous rectifier switch they are connected to is higher than a threshold, i.e., they perform voltage limiting operations on the gate voltage that exceeds the threshold. Based on the above analysis, it can be seen that the activation states of the current limiting circuit and the voltage limiting circuit in the protection circuit 30 are both independent of the on / off state of the synchronous rectifier switch.

[0100] In one embodiment, such as Figure 8 As shown, the unidirectional conduction circuit 307 may include a diode D3. The anode of the diode D3 is connected to the output terminal of the gate drive circuit 20, and the cathode of the diode D3 is connected to the other end of the first current limiting circuit 303 and the other end of the second current limiting circuit 304, that is, the cathode of the diode D3 is connected to the third node P3.

[0101] Based on the above connection method of diode D3, current can be prevented from flowing from the first current limiting circuit 303 to the output terminal of the gate drive circuit 20, thereby ensuring that the current flowing out of the first current limiting circuit 303 can be discharged through the current sinking circuit 308. Furthermore, using diode D3 as the unidirectional conduction circuit 307 can effectively avoid increasing the structural complexity of the power supply equipment and avoid increasing the cost of the power supply equipment.

[0102] In one embodiment, such as Figure 2 As shown, the DC / DC conversion circuit 10 in the power supply device may further include: a transformer T0, and a third synchronous rectifier switch Q3 and a fourth synchronous rectifier switch Q4 connected in parallel.

[0103] Among them, the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2 are connected in parallel to one end of the secondary winding of transformer T0, and the third synchronous rectifier switch Q3 and the fourth synchronous rectifier switch Q4 are connected in parallel to the other end of the secondary winding of transformer T0.

[0104] Correspondingly, such as Figure 9 As shown, the power supply device may further include: another gate drive circuit for driving the third synchronous rectifier switch Q3 and the fourth synchronous rectifier switch Q4, and another protection circuit for protecting the third synchronous rectifier switch Q3 and the fourth synchronous rectifier switch Q4. For ease of distinction, refer to... Figure 9 In this embodiment, the gate driving circuit for driving the first synchronous rectifier switch Q1 and the second synchronous rectifier switch Q2 is referred to as the first gate driving circuit 20, and the corresponding protection circuit is referred to as the first protection circuit 30. The gate driving circuit for driving the third synchronous rectifier switch Q3 and the fourth synchronous rectifier switch Q4 is referred to as the second gate driving circuit 40, and the corresponding protection circuit is referred to as the second protection circuit 50. The second protection circuit 50 is connected to the output terminal of the second gate driving circuit 40, the gate of the third synchronous rectifier switch Q3, and the gate of the fourth synchronous rectifier switch Q4, respectively, and the structure of the second protection circuit 50 is the same as that of the first protection circuit 30.

[0105] like Figure 9As shown, the second protection circuit 50 may include a first voltage limiting circuit 501, a second voltage limiting circuit 502, a first current limiting circuit 503, and a second current limiting circuit 504. One end of the first voltage limiting circuit 501 is connected to the gate of the third synchronous rectifier switch Q3, and the other end is grounded to GND. The first voltage limiting circuit 501 limits the gate voltage of the third synchronous rectifier switch Q3 when its gate voltage exceeds a third threshold voltage, ensuring that the gate voltage of Q3 is below the upper limit of the gate withstand voltage of the fourth synchronous rectifier switch Q4. This prevents the fourth synchronous rectifier switch Q4 from failing due to gate overvoltage, thus effectively protecting the fourth synchronous rectifier switch Q4.

[0106] One end of the second voltage limiting circuit 502 is connected to the gate of the fourth synchronous rectifier switch Q4, and the other end is grounded to GND. This second voltage limiting circuit 502 is used to limit the gate voltage of the fourth synchronous rectifier switch Q4 when its gate voltage exceeds a fourth threshold voltage, so that the gate voltage of the fourth synchronous rectifier switch Q4 is lower than the upper withstand voltage limit of the gate of the third synchronous rectifier switch Q3. This prevents the third synchronous rectifier switch Q3 from failing due to gate overvoltage, thus effectively protecting the third synchronous rectifier switch Q3.

[0107] One end of the first current limiting circuit 503 is connected to one end of the first voltage limiting circuit 501, and the other end of the first current limiting circuit 503 is connected to the output terminal of the second gate driving circuit 40. The first current limiting circuit 503 is used to limit the current flowing into the output terminal, thereby pulling down the voltage of the output terminal of the second gate driving circuit 40.

[0108] One end of the second current limiting circuit 504 is connected to one end of the second voltage limiting circuit 502, and the other end of the second current limiting circuit 504 is connected to the output terminal of the second gate driving circuit 40. The second current limiting circuit 504 is used to limit the current flowing into the output terminal, thereby lowering the voltage of the output terminal of the second gate driving circuit 40.

[0109] It is understandable that the aforementioned third threshold can be higher than the normal drive voltage of the third synchronous rectifier switch Q3 to avoid affecting the normal operation of the third synchronous rectifier switch Q3. Furthermore, the third threshold can be lower than the upper limit of the gate withstand voltage of the fourth synchronous rectifier switch Q4 to effectively protect the fourth synchronous rectifier switch Q4. Similarly, the aforementioned fourth threshold can be higher than the normal drive voltage of the fourth synchronous rectifier switch Q4 to avoid affecting the normal operation of the fourth synchronous rectifier switch Q4. Furthermore, the fourth threshold can be lower than the upper limit of the gate withstand voltage of the third synchronous rectifier switch Q3 to effectively protect the third synchronous rectifier switch Q3.

[0110] It is also understandable that, in the scenario where the third synchronous rectifier switch Q3 fails due to a short circuit, causing its gate voltage to be higher than the output voltage of the second gate drive circuit 40, the first current limiting circuit 503 limits the current flowing into the output of the second gate drive circuit 40, thereby lowering the output voltage of the second gate drive circuit 40. For example, it can make the output voltage of the second gate drive circuit 40 lower than the gate turn-on threshold voltage of the fourth synchronous rectifier switch Q4. This prevents the fourth synchronous rectifier switch Q4 from failing due to mis-turn-on.

[0111] In the scenario where the fourth synchronous rectifier switch Q4 fails due to a short circuit, causing its gate voltage to exceed the output voltage of the second gate drive circuit 40, the second current limiting circuit 504 limits the current flowing into the output of the second gate drive circuit 40, thereby lowering its output voltage. For example, it can make the output voltage of the second gate drive circuit 40 lower than the turn-on threshold voltage of the gate of the third synchronous rectifier switch Q3. This prevents the third synchronous rectifier switch Q3 from failing due to mis-turn-on.

[0112] In this embodiment, the upper limit of the gate withstand voltage of the third synchronous rectifier switch Q3 can be equal to the upper limit of the gate withstand voltage of the fourth synchronous rectifier switch Q4, and the turn-on threshold voltage of the gate of the third synchronous rectifier switch Q3 can be equal to the turn-on threshold voltage of the gate of the fourth synchronous rectifier switch Q4. That is, the upper limit of the gate withstand voltage of the multiple parallel-connected switches can be equal, and the turn-on threshold voltage of the gates can be equal. Of course, the upper limit of the gate withstand voltage of the multiple parallel-connected synchronous rectifier switches can also be unequal, and the turn-on threshold voltage of the multiple parallel-connected switches can also be unequal. This application does not limit this aspect.

[0113] In one embodiment, reference continues... Figure 9 The second protection circuit 50 may further include a third current-limiting circuit 505 and a fourth current-limiting circuit 506. One end of the third current-limiting circuit 505 is connected to one end of the first voltage-limiting circuit 501, and the other end is connected to the gate of the third synchronous rectifier switch Q3. That is, one end of the first voltage-limiting circuit 501 is connected to the gate of the third synchronous rectifier switch Q3 through the third current-limiting circuit 505. The third current-limiting circuit 505 is used to limit the current flowing into the first voltage-limiting circuit 501, that is, to limit the current between the gate of the third synchronous rectifier switch Q3 and the fourth node P4. Figure 4 and Figure 5 As shown, the fourth node P4 is the connection node between one end of the first voltage limiting circuit 501 and one end of the first current limiting circuit 503.

[0114] One end of the fourth current-limiting circuit 506 is connected to one end of the second voltage-limiting circuit 502, and the other end of the fourth current-limiting circuit 506 is connected to the gate of the fourth synchronous rectifier switch Q4. That is, one end of the second voltage-limiting circuit 502 is connected to the gate of the fourth synchronous rectifier switch Q4 through the fourth current-limiting circuit 506. The fourth current-limiting circuit 506 is used to limit the current flowing into the second voltage-limiting circuit 502, that is, to limit the current between the gate of the fourth synchronous rectifier switch Q4 and the fifth node P5. Figure 4 and Figure 5 As shown, the fifth node P5 is the connection node between one end of the second voltage limiting circuit 502 and one end of the second current limiting circuit 504.

[0115] It is understandable that the third current limiting circuit 505 can be a current limiting circuit for the first voltage limiting circuit 501, which can prevent the first voltage limiting circuit 501 from failing due to excessive power, thereby ensuring effective protection of the output terminal of the second gate drive circuit 40 by the first voltage limiting circuit 501. The fourth current limiting circuit 506 can be a current limiting circuit for the second voltage limiting circuit 502, which can prevent the second voltage limiting circuit 502 from failing due to excessive power. Therefore, effective protection of the output terminal of the second gate drive circuit 40 by the second voltage limiting circuit 502 can be ensured.

[0116] Furthermore, if any synchronous rectifier switch fails due to a short circuit, and the current flowing through the third current limiting circuit 505 or the fourth current limiting circuit 506 becomes excessive, causing overpower in either circuit, then the overpower current limiting circuit will fail open-circuit. After the current limiting circuit fails open-circuit, it isolates the short-circuited synchronous rectifier switch from the output terminal of the second gate drive circuit 40 and from other synchronous rectifier switches, effectively preventing the voltage limiting circuit from failing open-circuit due to overpower.

[0117] It is also understood that the second protection circuit 50 may include a unidirectional conduction circuit and a current sinking circuit. The structure and working principle of the unidirectional conduction circuit, as well as the structure and working principle of the current sinking circuit, can be referred to the previous description, and will not be repeated here.

[0118] It is also understood that, in the power supply device provided in the embodiments of this application, the synchronous rectifier switch in the DC / DC conversion circuit 10 can be a MOSFET, or it can be an insulated-gate bipolar transistor (IGBT), a silicon carbide power transistor, or a gallium nitride power transistor, etc. The gate drive circuit of the above-mentioned synchronous rectifier switch can be a single-channel gate driver, or a half-bridge gate driver, etc.

[0119] It is also understood that the DC / DC converter circuit 10 described above is illustrated using a half-bridge LLC resonant topology as an example. This DC / DC converter circuit 10 can also employ other types of topologies, such as isolated topologies like a half-bridge LLC resonant topology or a full-bridge LLC resonant topology, or non-isolated topologies like a buck or boost converter. This application embodiment does not limit the type of power conversion topology of the DC / DC converter circuit 10, only requiring that the DC / DC converter circuit 10 includes multiple parallel synchronous rectifier switches.

[0120] In summary, this application provides a power supply device in which the gates of two parallel synchronous rectifier switches are respectively connected to a voltage limiting circuit and a current limiting circuit. The voltage limiting circuit limits the gate voltage of the connected synchronous rectifier switch when it is too high, ensuring the gate voltage is below the upper limit of the gate voltage of the other synchronous rectifier switch. The current limiting circuit limits the current flowing from the gate of the connected synchronous rectifier switch to the output of the gate drive circuit. Therefore, when any synchronous rectifier switch fails due to a short circuit, resulting in an excessively high gate voltage, the protection circuit can effectively lower the output voltage of the gate drive circuit through voltage and current limiting operations. This prevents other synchronous rectifier switches connected in parallel with the short-circuited synchronous rectifier switch from also experiencing passive short-circuit failure.

[0121] Furthermore, since the protection circuit in the power supply equipment can effectively prevent multiple synchronous rectifier switches connected in parallel in the DC / DC converter circuit from short-circuiting and failing together, even if the number of other power supply devices connected in parallel on the DC bus is small (e.g., only one other power supply device is connected in parallel), these other power supply devices can also use external current to break the pin of the short-circuited synchronous rectifier MOSFET, thereby achieving fault isolation and preventing the power system from being shut down for a long time and affecting business operations. In other words, the fault isolation solution achieved by external current is not limited by the number of parallel power supply devices in the power supply system.

[0122] In the embodiments of this application, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "at least one" refers to one or more, and "multiple" refers to two or more.

[0123] In the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0124] The above description is merely an optional implementation of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A power supply device, characterized in that, The power supply device includes: a DC / DC / DC converter circuit, a gate drive circuit, and a protection circuit; The DC / DC converter circuit includes: a first synchronous rectifier switch and a second synchronous rectifier switch connected in parallel; the protection circuit includes: a first voltage limiting circuit, a second voltage limiting circuit, a first current limiting circuit, and a second current limiting circuit. One end of the first voltage limiting circuit is connected to the gate of the first synchronous rectifier switch, and the other end of the first voltage limiting circuit is grounded. The first voltage limiting circuit is used to limit the gate voltage of the first synchronous rectifier switch when the gate voltage of the first synchronous rectifier switch is higher than the first threshold, so that the gate voltage of the first synchronous rectifier switch is lower than the upper limit of the gate voltage of the second synchronous rectifier switch. One end of the second voltage limiting circuit is connected to the gate of the second synchronous rectifier switch, and the other end of the second voltage limiting circuit is grounded. The second voltage limiting circuit is used to limit the gate voltage of the second synchronous rectifier switch when the gate voltage of the second synchronous rectifier switch is higher than the second threshold, so that the gate voltage of the second synchronous rectifier switch is lower than the upper limit of the gate voltage of the first synchronous rectifier switch. One end of the first current limiting circuit is connected to one end of the first voltage limiting circuit, and the other end of the first current limiting circuit is connected to the output terminal of the gate driving circuit. The first current limiting circuit is used to limit the current flowing into the output terminal of the gate driving circuit. One end of the second current limiting circuit is connected to one end of the second voltage limiting circuit, and the other end of the second current limiting circuit is connected to the output terminal of the gate driving circuit. The second current limiting circuit is used to limit the current flowing into the output terminal of the gate driving circuit.

2. The power supply device according to claim 1, characterized in that, The first threshold is higher than the driving voltage of the first synchronous rectifier switch and lower than the gate voltage limit of the second synchronous rectifier switch, and the second threshold is higher than the driving voltage of the second synchronous rectifier switch and lower than the gate voltage limit of the first synchronous rectifier switch.

3. The power supply device according to claim 1 or 2, characterized in that, The protection circuit also includes: a third current limiting circuit and a fourth current limiting circuit; One end of the first voltage limiting circuit is connected to the gate of the first synchronous rectifier switch through the third current limiting circuit, and the third current limiting circuit is used to limit the current flowing into the first voltage limiting circuit. One end of the second voltage limiting circuit is connected to the gate of the second synchronous rectifier switch through the fourth current limiting circuit, and the fourth current limiting circuit is used to limit the current flowing into the second voltage limiting circuit.

4. The power supply device according to claim 3, characterized in that, Each of the first current limiting circuit, the second current limiting circuit, the third current limiting circuit, and the fourth current limiting circuit includes one resistor or multiple resistors connected in series. The total resistance of the resistors included in the third current limiting circuit is less than the total resistance of the resistors included in the first current limiting circuit, and the total resistance of the resistors included in the fourth current limiting circuit is less than the total resistance of the resistors included in the second current limiting circuit.

5. The power supply device according to any one of claims 1 to 4, characterized in that, The power supply device also includes a unidirectional conduction circuit and a current sinking circuit. The other end of the first current limiting circuit and the other end of the second current limiting circuit are connected to the output terminal of the gate driving circuit through the unidirectional conduction circuit, and the conduction direction of the unidirectional conduction circuit is from the output terminal of the gate driving circuit to the first current limiting circuit and the second current limiting circuit. One end of the current sinking circuit is connected to the other end of the first current limiting circuit and the other end of the second current limiting circuit, and the other end of the current sinking circuit is grounded. The current sinking circuit is used to discharge the current flowing out of the first current limiting circuit or the current flowing out of the second current limiting circuit.

6. The power supply device according to claim 5, characterized in that, The current sinking circuit includes a switching transistor, one end of which is connected to the other end of the first current limiting circuit and the other end of the second current limiting circuit, and the other end of which is grounded. The control terminal of the switching transistor is connected to the gate driving circuit, which is used for: When outputting a signal that turns off the first synchronous rectifier switch and the second synchronous rectifier switch, a signal that turns on the switch is also output.

7. The power supply device according to claim 6, characterized in that, The switching transistor is a P-type switching transistor, and both the first synchronous rectifier switching transistor and the second synchronous rectifier switching transistor are N-type switching transistors. The signal that turns off the first synchronous rectifier switching transistor and the second synchronous rectifier switching transistor is the same signal that turns on the switching transistor.

8. The power supply device according to any one of claims 5 to 7, characterized in that, The unidirectional conduction circuit includes a diode, the anode of which is connected to the output terminal of the gate drive circuit, and the cathode of which is connected to the other end of the first current limiting circuit and the other end of the second current limiting circuit.

9. The power supply device according to any one of claims 1 to 8, characterized in that, Each voltage limiting circuit in the first voltage limiting circuit and the second voltage limiting circuit includes: a transient voltage suppression TVS diode, a Zener diode, or a clamping circuit.

10. A power supply system, characterized in that, The power system includes: a plurality of power supply devices as described in any one of claims 1 to 9, wherein the output terminals of the plurality of power supply devices are connected in parallel to a DC bus.

Images