Anti-misoperation protection circuit and method
By introducing Zener diode D1 and transistor Q2 into the satellite power protection circuit, the problem of malfunction caused by output bus voltage fluctuations was solved, ensuring the reliability and efficiency of the power system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI INST OF SPACE POWER SOURCES
- Filing Date
- 2025-12-29
- Publication Date
- 2026-05-01
AI Technical Summary
Existing satellite power supply protection circuits are prone to malfunction when the output bus voltage fluctuates, leading to unnecessary shutdowns of the power system and affecting its reliability and efficiency.
By introducing Zener diode D1 and transistor Q2 into the protection circuit and adjusting the processing method of overvoltage detection and reference signals, the accuracy of the comparator output is ensured, and malfunctions are prevented.
It enables the protection circuit to operate accurately when the output bus voltage fluctuates, avoiding unnecessary power system shutdowns and improving the reliability and efficiency of the power system.
Smart Images
Figure CN121965403A_ABST
Abstract
Description
A protection circuit and method for preventing malfunctions Technical Field
[0001] This invention belongs to the field of power management technology for satellite power systems, and relates to a protection circuit and method for preventing malfunctions. Background Technology
[0002] As a core component of a satellite, the primary task of the power system is to provide high-quality, highly reliable continuous power to the entire satellite. With the continuous development of aerospace technology, the performance of protection circuits for space power supplies has been further improved, while also placing higher demands on various protection circuits to operate quickly, accurately, and reliably.
[0003] Currently, in the main power circuit of a space power supply, a large-capacity capacitor array is typically connected in series in the output bus that supplies power to the load. This is used to reduce the overshoot or drop in the output bus voltage when the load experiences large step changes. In a protection circuit shown in Figure 1, the comparator COMP compares the overvoltage detection signal OV_fb and the overvoltage reference signal OV_th.
[0004] Under normal circumstances, if the output bus voltage is in an overvoltage state, the protection circuit will trigger the relevant actions to shut down the main power circuit: according to the comparison result of OV_fb > OV_th, the comparator COMP will output a high level, the transistor Q1 will be turned on, the coil of the electromagnetic relay RELAY will be energized to close its contacts, the voltage of the soft-start pin SOFTSTART of the pulse width modulation chip will be pulled low, the drive signal of the switching device (such as MOSFET) output to the main power circuit will be turned off, thereby shutting down the main power circuit and realizing the protection of the power supply system and the load.
[0005] The overvoltage detection signal OV_fb is a voltage divider of the output bus voltage, and the overvoltage reference signal OV_th is obtained by current limiting and voltage regulation of the auxiliary source's output voltage (e.g., 12V) through resistor R5 and voltage regulator D2. A switch SW is installed on the path from the input voltage source Vin to the main power circuit and the auxiliary source. When this switch SW is open, the value of the overvoltage reference signal OV_th will decrease rapidly because the auxiliary source typically does not have a large capacity of energy storage. However, the large capacitance array on the output bus needs to discharge slowly through the load, causing the voltage drop rate of the overvoltage detection signal OV_fb to be much lower than that of the overvoltage reference signal OV_th. Therefore, during the rapid drop of the overvoltage reference signal OV_th, if the current value of the overvoltage reference signal OV_th is lower than the current value of the overvoltage detection signal OV_fb, the comparator COMP will also correspondingly determine that OV_fb > 0. The comparison result of OV_th caused the protection circuit to erroneously trigger the relevant actions to shut down the main power circuit even when it was no longer supplying power to the main power circuit and the output bus voltage was obviously not overvoltage.
[0006] To prevent malfunctions in the protection circuit, one existing method involves adding a resistive load to the output bus to accelerate the descent of the output bus voltage and the overvoltage detection signal OV_fb after power-down. However, this method increases power supply heat dissipation and reduces efficiency, contradicting the design goals of the power supply system. Another method involves adding a capacitor to the output of the auxiliary source to slow down the descent of the overvoltage reference signal OV_th. However, this method results in a slow build-up of the auxiliary source's output voltage, which in turn delays the build-up time of the output bus voltage, violating the requirement for fast output bus response. Therefore, improvements to the protection circuit are urgently needed to overcome these shortcomings. Summary of the Invention
[0007] The purpose of this invention is to provide an improved protection circuit that can prevent malfunctions.
[0008] To achieve the above objectives, one technical solution of the present invention is to provide a protection circuit for a power supply system, characterized in that the power supply system includes an input voltage source and a main power circuit; the protection circuit includes an auxiliary source, a pulse width modulation chip, a comparator, a relay, transistors Q1 and Q2, Zener diodes D1 and D2, a resistor R4, and a voltage divider circuit; wherein the Zener diode D1 has a Zener voltage V. D1 The voltage regulation value V is greater than that of Zener diode D2. D2 And less than the undervoltage latch lower limit V of the pulse width modulation chip. UVLO V D2 < V D1 < V UVLO The input voltage sources are supplied to the main power circuit and the auxiliary source, respectively. The output bus voltage provided by the main power circuit supplies power to the load, and the output voltage of the auxiliary source supplies power to other components in the protection circuit. The main power circuit, through a voltage divider circuit, supplies the overvoltage detection signal OV_fb to the non-inverting input of the comparator. The overvoltage detection signal OV_fb corresponds to the voltage division of the output bus voltage. The output voltage of the auxiliary source, through the Zener diode D2, supplies the overvoltage reference signal OV_th to the inverting input of the comparator. The output of the comparator is connected to the base of transistor Q1. The output of transistor Q1... The emitter of transistor Q2 is connected to the collector of transistor Q1, and the collector of transistor Q1 is connected to one end of the relay coil. The other end of the relay coil is connected to the output voltage of the auxiliary source. The emitter of transistor Q2 is grounded, and the base of transistor Q2 is connected to the anode of Zener diode D1. The cathode of Zener diode D1 is connected to the second end of resistor R4, and the first end of resistor R4 is connected to the output voltage of the auxiliary source. The pulse width modulation chip is connected to the main power circuit through an external driving circuit. The driving signal output by the pulse width modulation chip is used to drive the switching devices of the main power circuit. The soft-start pin of the pulse width modulation chip is connected to the contacts of the relay.
[0009] For example, the voltage divider circuit includes resistors R1 and R2 connected in series; the first end of resistor R1 is connected to the output bus of the main power circuit supplying power to the load; the second end of resistor R2 is grounded; the connection point between the second end of resistor R1 and the first end of resistor R2 is further connected to the non-inverting input of a comparator to transmit an overvoltage detection signal OV_fb.
[0010] For example, the output of the main power circuit is also connected to one end of capacitor C1, and the other end of capacitor C1 is grounded.
[0011] For example, the protection circuit also includes a resistor R5 connected in series with the Zener diode D2; the first end of the resistor R5 is connected to the output voltage of the auxiliary source; the anode of the Zener diode D2 is grounded; the connection point between the cathode of the Zener diode D2 and the second end of the resistor R5 is further connected to the inverting input of the comparator to transmit the overvoltage reference signal OV_th.
[0012] For example, the protection circuit also includes a resistor R3; the first end of the resistor R3 is connected to the output voltage of the auxiliary source, and the second end of the resistor R3 is connected to the base of the transistor Q1.
[0013] For example, the protection circuit further includes a switch; the positive terminal of the input voltage source is connected to the first terminal of the switch, and the negative terminal of the input voltage source is grounded; the second terminal of the switch is connected to the input terminal of the main power circuit and the input terminal of the auxiliary source, respectively.
[0014] For example, the power system is a space power source.
[0015] For example, the output bus of the main power circuit supplying power to the load is connected in series with a capacitor array.
[0016] Another technical solution of the present invention is to provide a method for preventing malfunction of a protection circuit, used in the protection circuit of any of the above-mentioned power supply systems; the output voltage of the auxiliary source is lower than the undervoltage latch lower limit V of the pulse width modulation chip. UVLO When the pulse width modulation chip does not output a drive signal to the main power circuit, the switching devices of the main power circuit are in a normally open state, and the output voltage bus provided by the main power circuit to the load is not overvoltage; when the comparator outputs a high or low level, neither the pulse width modulation chip nor the switching devices of the main power circuit operate; the output voltage of the auxiliary source is higher than the undervoltage latch lower limit V of the pulse width modulation chip. UVLOWhen the output voltage is lower than or equal to the rated value of the auxiliary source's output voltage, if OV_fb > OV_th, the output voltage bus is in an overvoltage state, the comparator outputs a high level, the relay operates, pulling down the voltage of the soft-start pin of the pulse width modulation chip, and turning off the drive signal output by the pulse width modulation chip to the main power circuit, thereby protecting the power supply system and the load; if OV_fb < OV_th, the output voltage bus is not overvoltage, the comparator outputs a low level, the relay does not operate, the pulse width modulation chip outputs the drive signal normally, and the switching devices of the main power circuit are modulated normally.
[0017] For example, the output voltage of the auxiliary source is between 0 and V. D2 Within the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are in a normally open state, the output voltage of the main power circuit is zero, neither Zener diodes D1 nor D2 have reached the regulated state, and both transistors Q2 and Q1 are cut off; when the comparator outputs a high or low level, the relay will not malfunction because transistors Q2 and Q1 are cut off; the output voltage of the auxiliary source is within V... D2 ~ V D1 Within the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are in a normally open state, the output voltage of the main power circuit is zero, the Zener diode D2 reaches the regulated state, and OV_fb > OV_th will not occur; and the Zener diode D1 has not reached the regulated state, both transistors Q2 and Q1 are cut off, and the relay will not malfunction; the output voltage of the auxiliary source is within V D1 ~ V UVLO Within the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are in a normally open state, the output voltage of the main power circuit is zero, the Zener diode D2 reaches the regulated state, and there will be no OV_fb > OV_th, so the relay will not malfunction; at this time, the Zener diode D1 reaches the regulated state, and the transistor Q2 is turned on; the output voltage of the auxiliary source is higher than the undervoltage latch lower limit V of the pulse width modulation chip. UVLO When the voltage is below or equal to the rated value of the auxiliary source's output voltage, Zener diodes D1 and D2 reach a regulated state, transistor Q2 is turned on, the pulse width modulation chip outputs a normal drive signal, and the main power circuit switching devices are normally modulated; when OV_fb > OV_th, the output voltage bus is in an overvoltage state, transistor Q1 is turned on according to the high level output by the comparator, the relay coil is energized and the contacts are closed, pulling down the voltage of the soft-start pin of the pulse width modulation chip, turning off the drive signal output by the pulse width modulation chip to the main power circuit, thus protecting the power system and load, which is a normal protection action.
[0018] The improved protection circuit of this invention can perform normal protection actions according to the actual overvoltage state of the output bus, and the protection circuit will not malfunction when the power supply system is powered on or off, thus overcoming the defects of existing protection circuits. Attached Figure Description
[0019] Figure 1 is a schematic diagram of a protection circuit before the improvement.
[0020] Figure 2 is a schematic diagram of an improved protection circuit. Detailed Implementation
[0021] Figure 1 shows a power supply system and its protection circuit. The power supply system includes an input voltage source Vin, a switch SW, a main power circuit, and a capacitor C1. The protection circuit includes an auxiliary source, a pulse width modulation chip, a comparator COMP, an electromagnetic relay RELAY, a transistor Q1, a Zener diode D2, and resistors R1, R2, R3, and R5.
[0022] The positive terminal of the input voltage source Vin is connected to the first terminal of switch SW, and the negative terminal of input voltage source Vin is grounded. The second terminal of switch SW is split into two paths. One path is connected to the input terminal of the main power circuit, which is responsible for power conversion, transforming the input voltage into a stable output voltage to power the load (the main power circuit may include switching devices (such as MOSFETs), as well as transformers, rectifiers, and other components). The other path of the second terminal of switch SW is connected to the input terminal of the auxiliary source, which provides operating power to various components in the protection circuit (such as pulse width modulation chips, comparators COMP, electromagnetic relays RELAY, etc.) through the output voltage of the auxiliary source (such as 12V).
[0023] The output of the main power circuit is connected to one end of capacitor C1, and the other end of capacitor C1 is grounded. Capacitor C1 is responsible for filtering, which can improve the stability of the output bus voltage and reduce voltage fluctuations. The output of the main power circuit also transmits an overvoltage detection signal OV_fb to the non-inverting input (+) of comparator COMP through a voltage divider formed by resistors R1 and R2 in series.
[0024] Among them, the first end of resistor R1 is connected to the output bus of the main power circuit supplying power to the load, and the second end of resistor R2 is grounded; the connection point between the second end of resistor R1 and the first end of resistor R2 serves as a voltage divider point, which is further connected to the non-inverting input (+) of comparator COMP, and sends an overvoltage detection signal OV_fb to the non-inverting input (+) of comparator COMP; the overvoltage detection signal OV_fb corresponds to the voltage division of the output bus voltage.
[0025] The output voltage (12V) of the auxiliary source is current-limited and regulated by a series resistor R5 and a Zener diode D2, resulting in an overvoltage reference signal OV_th, which is then sent to the inverting input (-) of the comparator COMP. Specifically, the first terminal of resistor R5 is connected to the output voltage of the auxiliary source, and the anode of Zener diode D2 is grounded. The connection point between the second terminal of resistor R5 and the cathode of Zener diode D2 is further connected to the inverting input (-) of comparator COMP, supplying the overvoltage reference signal OV_th to this input. The value of this overvoltage reference signal OV_th is determined by the regulated voltage of Zener diode D2.
[0026] The output of comparator COMP is connected to the base of transistor Q1, the emitter of transistor Q1 is grounded, and the collector of transistor Q1 is connected to one end of the coil of electromagnetic relay RELAY. The other end of the coil of electromagnetic relay RELAY is connected to the output voltage (12V) of the auxiliary source. The first end of resistor R3 is also connected to the output voltage (12V) of the auxiliary source, and the second end of resistor R3 is connected to the base of transistor Q1. Resistor R3 provides current-limiting drive between the output of comparator COMP and the base of transistor Q1.
[0027] The pulse width modulation (PWM) chip is connected to the main power circuit via an external drive circuit (not shown). The drive signal output by this chip drives the switching devices (such as MOSFETs) of the main power circuit, and the power transfer of the main power circuit is controlled by adjusting the duty cycle of the drive pulse. The soft-start pin SOFTSTART of the PWM chip is connected to the contact of the electromagnetic relay RELAY. When the contact is closed, the voltage of the SOFTSTART pin is pulled low, thereby turning off the drive signal to the main power circuit. The example PWM chip is the UC1825.
[0028] Under normal conditions, if the output bus voltage is in an overvoltage state, and the value of the overvoltage detection signal OV_fb is higher than the value of the overvoltage reference signal OV_th (OV_fb > OV_th), the comparator COMP outputs a high level, the transistor Q1 is turned on, the coil of the electromagnetic relay RELAY is energized, causing its contacts to close, the voltage of the soft-start pin SOFTSTART of the pulse width modulation chip is pulled low, and the drive signal output to the main power circuit is turned off, thus turning off the main power circuit and protecting the power supply system and load.
[0029] Theoretically, if the output bus voltage is not in an overvoltage state, and the value of the overvoltage detection signal OV_fb is lower than the value of the overvoltage reference signal OV_th (OV_fb < OV_th), the comparator COMP outputs a low level, the transistor Q1 is cut off, no current flows through the coil of the electromagnetic relay RELAY, and its contacts remain open. At this time, the soft-start pin SOFTSTART of the pulse width modulation chip is not affected by the electromagnetic relay RELAY, and maintains normal operation to drive the switching devices of the main power circuit. The main power circuit normally supplies power to the load, and the protection circuit does not perform protection actions.
[0030] However, the protection circuit in Figure 1 cannot distinguish that in some cases, the output bus voltage is not actually overvoltage but there is an "overvoltage illusion" of OV_fb > OV_th, and thus erroneously triggers the protection action of shutting down the main power circuit.
[0031] For example, when the power system in Figure 1 is used as a space power source to supply power to satellites, a large-capacity capacitor array is connected in series in the output bus of the main power circuit supplying power to the load. This is used to reduce the overshoot or drop in the output bus voltage when the load experiences large step changes. Assuming that when switch SW is open, the large-capacity capacitor array slowly discharges through the load, causing the voltage drop rate of the overvoltage detection signal OV_fb to be much lower than the voltage drop rate of the overvoltage reference signal OV_th. This results in an "overvoltage illusion" where the output bus voltage is actually not overvoltage (switch SW is open, and the main power circuit is not supplying power) but OV_fb > OV_th during the rapid drop in the value of the overvoltage reference signal OV_th.
[0032] The protection circuit may malfunction under these conditions without overvoltage, including: the comparator COMP will still output a high level based on the comparison result of OV_fb > OV_th, the transistor Q1 will turn on, the coil of the electromagnetic relay RELAY will be energized and the contacts will close, the voltage of the soft-start pin SOFTSTART of the pulse width modulation chip will be pulled low, and the drive signal output to the main power circuit will be turned off.
[0033] To prevent malfunction of the protection circuit, as shown in Figure 2, this invention provides an improved protection circuit that adds three components: resistor R4, Zener diode D1, and transistor Q2. The Zener diode D1 has a Zener voltage regulation value V. D1 The voltage regulation value V is greater than that of Zener diode D2. D2 And less than the undervoltage latch lower limit V of pulse width modulation chips (such as UC1825). UVLO That is: V D2 <V D1 <V UVLO .
[0034] The difference from the circuit in Figure 1 is that in the improved protection circuit shown in Figure 2, the emitter of transistor Q1 is connected to the collector of the newly added transistor Q2, the emitter of transistor Q2 is grounded, the base of transistor Q2 is connected to the anode of Zener diode D1, the cathode of Zener diode D1 is connected to the second terminal of resistor R4, and the first terminal of resistor R4 is connected to the output voltage (12V) of the auxiliary source. The other components of the protection circuit and their connections are the same as in Figure 1, and will not be described in detail.
[0035] During the first to third stages below, the output voltage of the auxiliary source is always lower than the undervoltage latch lower limit V of the pulse width modulation chip. UVLO The chip is in an undervoltage latch state and does not output a drive signal; the main power circuit has no drive signal, and the switching devices are in a normally open state, making the output voltage of the main power circuit zero. Therefore, the output bus voltage will not be overvoltage during these stages. The improved protection circuit can prevent malfunctions during these stages. The specific mechanism is as follows: In the first stage, the output voltage of the auxiliary source is between 0 and V. D2 Within the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are turned off, the output voltage of the main power circuit is zero, and the output bus voltage will not experience overvoltage. Even if OV_fb > OV_th, it is considered an "overvoltage illusion." Although the comparator COMP outputs a high level, the output voltage of the auxiliary source has not reached the regulated value V. D1 and V D2 If neither Zener diodes D1 nor D2 reaches the regulated state, then there is no driving current at the base of transistor Q2, and transistor Q2 is cut off. This causes the emitter of transistor Q1 to be open, and transistor Q1 is cut off. At this time, the coil of electromagnetic relay RELAY has no current and the contacts are normally open, so it will not malfunction.
[0036] In the second stage, the output voltage of the auxiliary source is at V D2 ~ V D1 Within the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are turned off, the output voltage of the main power circuit is zero, and the output bus voltage will not experience overvoltage; because the output voltage of the auxiliary source reaches the regulated value V... D2 Zener diode D2 is in a regulated state, so OV_fb > OV_th will not occur, and the output voltage of the auxiliary source has not reached the regulated value V. D1 If the Zener diode D1 does not reach the regulated state, and transistors Q2 and Q1 are still cut off, then the coil of the electromagnetic relay RELAY has no current and the contacts are normally open, so it will not malfunction.
[0037] In the third stage, the output voltage of the auxiliary source is at V D1 ~ V UVLOWithin the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are turned off, the output voltage of the main power circuit is zero, and the output bus voltage will not experience overvoltage; the output voltage of the auxiliary source reaches the regulated value V. D1 and V D2 When Zener diode D1 is in a regulated state, transistor Q2 is turned on; and because Zener diode D2 is in a regulated state, OV_fb > OV_th will not occur, and electromagnetic relay RELAY will not malfunction.
[0038] In the fourth stage, the output voltage of the auxiliary source is at V UVLO Within the range of ~12V, both Zener diodes D1 and D2 are in a regulated state, transistor Q2 is turned on, and the emitter of transistor Q1 is reliably grounded through transistor Q2.
[0039] At this time, if OV_fb < OV_th, it is considered that the output bus voltage is not in an overvoltage state. The comparator COMP outputs a low level, the base of transistor Q1 does not have sufficient drive current, transistor Q1 is cut off, and the electromagnetic relay RELAY does not operate (no current in the coil, contacts are normally open). The soft-start pin SOFTSTART of the pulse width modulation chip is not affected by the electromagnetic relay RELAY and normally provides a drive signal to the main power circuit. The switching devices of the main power circuit are normally modulated. At this time, the protection circuit does not trigger the protection action.
[0040] At this time, if OV_fb > OV_th, it is considered that the output bus voltage is in an overvoltage state. The comparator COMP outputs a high level, the transistor Q1 is turned on, and the electromagnetic relay RELAY is activated (the coil is energized and the contacts are closed). This pulls down the voltage of the soft-start pin SOFTSTART of the pulse width modulation chip, turns off the drive signal output to the main power circuit, and realizes the protection of the power system and the load. This is a normal protection action.
[0041] Therefore, in the improved embodiment of the present invention, the protection circuit can perform normal protection operation according to the actual overvoltage state of the output bus, and the protection circuit will not malfunction when the power supply system is powered on or off.
[0042] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A protection circuit for a power supply system, characterized in that, The power supply system includes an input voltage source and a main power circuit; the protection circuit includes an auxiliary source, a pulse width modulation chip, a comparator, a relay, transistors Q1 and Q2, Zener diodes D1 and D2, a resistor R4, and a voltage divider circuit; wherein, the Zener diode D1 has a regulated voltage V. D1 The voltage regulation value V is greater than that of Zener diode D2. D2 And less than the undervoltage latch lower limit V of the pulse width modulation chip. UVLO V D2 < V D1 < V UVLO The input voltage sources are supplied to the main power circuit and the auxiliary source, respectively. The output bus voltage provided by the main power circuit supplies power to the load, and the output voltage of the auxiliary source supplies power to other components in the protection circuit. The main power circuit, through a voltage divider circuit, supplies the overvoltage detection signal OV_fb to the non-inverting input of the comparator. The overvoltage detection signal OV_fb corresponds to the voltage division of the output bus voltage. The output voltage of the auxiliary source, through the Zener diode D2, supplies the overvoltage reference signal OV_th to the inverting input of the comparator. The output of the comparator is connected to the base of transistor Q1. The output of transistor Q1... The emitter of transistor Q2 is connected to the collector of transistor Q1, and the collector of transistor Q1 is connected to one end of the relay coil. The other end of the relay coil is connected to the output voltage of the auxiliary source. The emitter of transistor Q2 is grounded, and the base of transistor Q2 is connected to the anode of Zener diode D1. The cathode of Zener diode D1 is connected to the second end of resistor R4, and the first end of resistor R4 is connected to the output voltage of the auxiliary source. The pulse width modulation chip is connected to the main power circuit through an external driving circuit. The driving signal output by the pulse width modulation chip is used to drive the switching devices of the main power circuit. The soft-start pin of the pulse width modulation chip is connected to the contacts of the relay.
2. The protection circuit of the power supply system as described in claim 1, characterized in that, The voltage divider circuit includes resistors R1 and R2 connected in series; the first end of resistor R1 is connected to the output bus of the main power circuit supplying power to the load; the second end of resistor R2 is grounded; the connection point between the second end of resistor R1 and the first end of resistor R2 is further connected to the non-inverting input of the comparator to transmit the overvoltage detection signal OV_fb.
3. The protection circuit of the power supply system as described in claim 1, characterized in that, The output terminal of the main power circuit is also connected to one end of capacitor C1, and the other end of capacitor C1 is grounded.
4. The protection circuit of the power supply system as described in claim 1, characterized in that, The protection circuit also includes a resistor R5 connected in series with the Zener diode D2; the first end of the resistor R5 is connected to the output voltage of the auxiliary source; the anode of the Zener diode D2 is grounded; the connection point between the cathode of the Zener diode D2 and the second end of the resistor R5 is further connected to the inverting input of the comparator to transmit the overvoltage reference signal OV_th.
5. The protection circuit for the power supply system as described in claim 1, characterized in that, The protection circuit also includes a resistor R3; the first end of the resistor R3 is connected to the output voltage of the auxiliary source, and the second end of the resistor R3 is connected to the base of the transistor Q1.
6. The protection circuit of the power supply system as described in claim 1, characterized in that, The protection circuit also includes a switch; the positive terminal of the input voltage source is connected to the first terminal of the switch, and the negative terminal of the input voltage source is grounded; the second terminal of the switch is connected to the input terminal of the main power circuit and the input terminal of the auxiliary source, respectively.
7. The protection circuit of the power supply system as described in claim 1, characterized in that, The power system is a space power source.
8. The protection circuit for the power supply system as described in claim 7, characterized in that, The main power circuit has a capacitor array connected in series with the output bus that supplies power to the load.
9. A method for preventing malfunction of a protection circuit, used in the protection circuit of the power supply system according to any one of claims 1 to 8, characterized in that, The output voltage of the auxiliary source is lower than the undervoltage latch lower limit V of the pulse width modulation chip. UVLO When the pulse width modulation chip does not output a drive signal to the main power circuit, the switching devices of the main power circuit are in a normally open state, and the output voltage bus provided by the main power circuit to the load is not overvoltage; when the comparator outputs a high or low level, neither the pulse width modulation chip nor the switching devices of the main power circuit operate; the output voltage of the auxiliary source is higher than the undervoltage latch lower limit V of the pulse width modulation chip. UVLO When the output voltage is lower than or equal to the rated value of the auxiliary source's output voltage, if OV_fb > OV_th, the output voltage bus is in an overvoltage state, the comparator outputs a high level, the relay operates, pulling down the voltage of the soft-start pin of the pulse width modulation chip, and turning off the drive signal output by the pulse width modulation chip to the main power circuit, thereby protecting the power supply system and the load; if OV_fb < OV_th, the output voltage bus is not overvoltage, the comparator outputs a low level, the relay does not operate, the pulse width modulation chip outputs the drive signal normally, and the switching devices of the main power circuit are modulated normally.
10. The method as described in claim 9, characterized in that, The output voltage of the auxiliary source is between 0 and V. D2 Within the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are in a normally open state, the output voltage of the main power circuit is zero, neither Zener diodes D1 nor D2 have reached the regulated state, and both transistors Q2 and Q1 are cut off; when the comparator outputs a high or low level, the relay will not malfunction because transistors Q2 and Q1 are cut off; the output voltage of the auxiliary source is within V... D2 ~ V D1 Within the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are in a normally open state, the output voltage of the main power circuit is zero, the Zener diode D2 reaches the regulated state, and OV_fb > OV_th will not occur; and the Zener diode D1 has not reached the regulated state, both transistors Q2 and Q1 are cut off, and the relay will not malfunction; the output voltage of the auxiliary source is within V D1 ~ V UVLO Within the specified range, the pulse width modulation chip does not output a drive signal, the switching devices of the main power circuit are in a normally open state, the output voltage of the main power circuit is zero, the Zener diode D2 reaches the regulated state, and there will be no OV_fb > OV_th, so the relay will not malfunction; at this time, the Zener diode D1 reaches the regulated state, and the transistor Q2 is turned on; the output voltage of the auxiliary source is higher than the undervoltage latch lower limit V of the pulse width modulation chip. UVLO When the voltage is below or equal to the rated value of the auxiliary source's output voltage, Zener diodes D1 and D2 reach a regulated state, transistor Q2 is turned on, the pulse width modulation chip outputs a normal drive signal, and the switching devices of the main power circuit are normally modulated; when OV_fb > OV_th, the output voltage bus is in an overvoltage state, transistor Q1 is turned on according to the high level output of the comparator, the relay coil is energized and the contacts are closed, pulling down the voltage of the soft-start pin of the pulse width modulation chip, turning off the drive signal output by the pulse width modulation chip to the main power circuit, thus protecting the power system and the load, which is a normal protection action.