TWI596855B - Protection circuit for switching power supply with multi-output - Google Patents

Description

Protection circuit for switched power supply with multiple outputs

The present invention relates to a related art of a power supply device, and more particularly to a protection circuit suitable for a switching power supply device having multiple outputs.

A switching power supply with multiple outputs is widely available to consumers by providing multiple output voltages of different sizes to multiple different electronic devices. However, since the switching power supply device may cause an overvoltage at the output end of the switching power supply device due to the failure of its internal feedback circuit, the internal components of the switched power supply device are damaged. In addition, since the consumer may also accidentally short-circuit any of the output terminals of the switching power supply device during operation, the internal components of the switched power supply device are also damaged.

However, up to now, the protection circuit of any of the switching power supply devices has been protected against both the overvoltage and the short circuit at the output of the above-described switching power supply device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a protection circuit suitable for a switching power supply device having multiple outputs, which can be protected against both an overvoltage and a short circuit at the output of the above-described switching power supply device.

The present invention proposes a protection circuit suitable for a switching power supply device having multiple outputs. The protection circuit includes a voltage abnormality detecting unit and a protection trigger signal generating unit. The voltage abnormality detecting unit receives the first output power of the switching power supply device Pressing the second output voltage to determine whether the first output voltage is greater than the first preset value, and determining whether the second output voltage is greater than the second preset value. When any of the above determination results is yes, the coupling signal is generated. . The protection trigger signal generating unit is configured to generate and latch the protection trigger signal according to the coupling signal, and provide the protection trigger signal to the first pulse width modulation control circuit and the second pulse width modulation control circuit of the switching power supply device, and further The first pulse width modulation control circuit and the second pulse width modulation control circuit respectively stop outputting the first pulse width modulation signal and the second pulse width modulation signal.

100‧‧‧Switching power supply unit

100-1, 100-2‧‧‧ output

102‧‧‧ Noise Filter

104‧‧‧AC/DC converter circuit

106, 124‧‧‧Transformers

106-1, 106-2, 124-1‧‧‧ primary side coil

106-3, 124-2‧‧‧second side coil

108, 126‧‧‧ power level

108-1, 126-1‧‧‧ PWM control circuit

108-2, 126-2‧‧‧ Power transistors

110, 128, 204, 208, 214, 216, 220, 222, 226, 230, 302, 306, 308, 312, 314‧‧‧ impedance

112, 116, 130‧‧‧Rectifier circuit

114, 118, 132‧‧‧ energy storage unit

120, 134‧‧ ‧ feedback circuit

122, 136‧‧‧ signal isolation unit

202, 218, 224, 318‧‧‧ diodes

206‧‧‧Signal transmission unit

206-1, 210-1, 304-1‧‧‧ first end

206-2, 210-2, 304-2‧‧‧ second end

200‧‧‧Voltage abnormality detection unit

210‧‧‧Voltage control switch

210-3‧‧‧ Reference

212, 228‧‧ ‧ Jenus diode

232‧‧‧ Circuitry

300‧‧‧Protection trigger signal generation unit

304‧‧‧Signal receiving unit

310‧‧‧PNP type double carrier junction transistor

316‧‧‧NPN type double carrier junction transistor

B‧‧‧ base

C‧‧‧集极

E‧‧‧射极

TRI‧‧‧protection trigger signal

VCC‧‧‧ operating voltage

VIN‧‧‧ input voltage

VOUT1, VOUT2, VOUT3, VOUTN‧‧‧ output voltage

VSS1, VSS2‧‧‧ reference potential

1 depicts a protection circuit suitable for use with a switched power supply having multiple outputs in accordance with an embodiment of the present invention.

1 depicts a protection circuit suitable for a switched power supply device having multiple outputs in accordance with an embodiment of the present invention. Referring to FIG. In Fig. 1, reference numeral 100 denotes a switched power supply having multiple outputs, and the combination of the two portions indicated by reference numerals 200 and 300 represents a protection circuit in accordance with an embodiment of the present invention. To simplify the description, the switching power supply device 100 takes two different outputs as an example, and provides output voltages VOUT1 and VOUT2 through the output terminals 100-1 and 100-2, respectively. As shown in FIG. 1 , the switching power supply device 100 includes a noise filter 102 , an AC-DC conversion circuit 104 , a transformer 106 , a power stage 108 , an impedance 110 , a rectifier circuit 112 , and an energy storage unit 114 . The rectifier circuit 116, the energy storage unit 118, the feedback circuit 120, the signal isolation unit 122, the transformer 124, the power stage 126, the impedance 128, the rectifier circuit 130, and the energy storage unit 132.

In this example, transformer 106 has two primary side coils (indicated by 106-1 and 106-2, respectively) and one secondary side coil (indicated by 106-3), and one of the primary side coils of transformer 106. One end of 106-1 is coupled to the input voltage VIN through the AC-DC conversion circuit 104 and the noise filter 102 in sequence. The noise filter 102 can be an EMI filter, and the designer can decide according to actual design requirements. Whether or not the noise filter 102 is used. Further, the AC-DC conversion circuit 104 may be a bridge rectifier.

The power stage 108 has a pulse width modulation (PWM) control circuit 108-1 and a power transistor 108-2 used as a switch. The power transistor 108-2 is coupled to the AC-DC conversion circuit 104 through the primary side coil 106-1 and coupled to the reference potential VSS1 through the impedance 110. By controlling the on/off state of the power transistor 108-2, it is possible to determine whether or not current is allowed to pass through the primary side coil 106-1. The PWM control circuit 108-1 is configured to receive the operating voltage VCC and generate a PWM signal to the control terminal of the power transistor 108-2 to control the switching frequency of the power transistor 108-2 between the on and off states. Of course, the power transistor 108-2 can also be modified to be coupled between the primary side coil 106-1 and the AC-DC conversion circuit 104, which is a simple replacement in the art.

One end of the other primary side coil 106-2 of the transformer 106 is coupled to one end of the energy storage unit 118 through the rectifying circuit 116, and the other end of the primary side coil 106-2 is coupled to the other end of the energy storage unit 118 and the reference. Potential VSS1. The rectifier circuit 116 is coupled to the energy storage unit 118 to generate the operating voltage VCC required for the entire system shown in FIG. One end of the secondary side coil 106-3 of the transformer 106 is coupled to one end of the energy storage unit 114 through the rectifying circuit 112, and the other end of the secondary side coil 106-3 is coupled to the other end of the energy storage unit 114 and the reference. The potential VSS2, this reference potential VSS2 can be, for example, a ground potential (Ground). The rectifier circuit 112 is coupled to the energy storage unit 114 to generate an output voltage VOUT1.

In this example, the rectifier circuits 112 and 116 can each be implemented by a diode, and the rectifier circuit 112 can be modified to be coupled between the other end of the secondary side coil 106-3 and the reference potential VSS2, and the rectifier circuit 116 can also be modified to be coupled between the other end of the primary side coil 106-2 and the reference potential VSS1, which is also a simple replacement of the art, but the anodes of the two diodes of the rectifier circuits 112 and 116 are required. The reference potentials VSS2 and VSS1 are coupled respectively. In addition, the impedance 110 can be implemented by a resistor, and the energy storage units 114 and 118 Each capacitor can be used, and the designer can decide whether to use the impedance 110, the energy storage unit 114 and the energy storage unit 118 according to actual design requirements.

The signal isolation unit 122 can be a photo coupler for transmitting the feedback signal generated by the feedback circuit 120 to the PWM control circuit 108-1, so that the PWM control circuit 108-1 can adjust the PWM accordingly. The duty cycle of the signal, which in turn allows the value of the output voltage VOUT1 to settle within a preset range.

The transformer 124 has a primary side coil and a secondary side coil (indicated by 124-1 and 124-2, respectively), and one end of the primary side coil 124-1 of the transformer 124 is also sequentially transmitted through the AC-DC conversion circuit 104. The input voltage VIN is coupled to the noise filter 102. The interior of power stage 126 has a PWM control circuit 126-1 and a power transistor 126-2 that acts as a switch. The power transistor 126-2 is coupled to the AC-DC conversion circuit 104 through the primary side coil 124-1 and coupled to the reference potential VSS1 through the impedance 128. By controlling the opening and closing state of the power transistor 126-2, it is possible to determine whether or not current is allowed to pass through the primary side coil 124-1. The PWM control circuit 126-1 is configured to receive the operating voltage VCC and generate a PWM signal to the control terminal of the power transistor 126-2 to control the switching frequency of the power transistor 126-2 between the on and off states. Of course, the power transistor 126-2 can also be modified to be coupled between the primary side coil 124-1 and the AC-DC conversion circuit 104, which is a simple replacement in the art.

One end of the secondary side coil 124-2 of the transformer 124 is coupled to one end of the energy storage unit 132 through the rectifying circuit 130, and the other end of the secondary side coil 124-2 is coupled to the other end of the energy storage unit 132 and the reference. Potential VSS2. The rectifier circuit 130 is coupled to the energy storage unit 132 to generate an output voltage VOUT2.

In this example, the rectifier circuit 130 can be implemented by a diode, and the rectifier circuit 130 can be modified to be coupled between the other end of the secondary side coil 124-2 and the reference potential VSS2, which is also a technology in the art. A simple replacement, but the anode of the diode as the rectifier circuit 130 is coupled to the reference potential VSS2. In addition, the impedance 128 and the energy storage unit 132 can be implemented by using a resistor and a capacitor, respectively, and the designer can decide whether to adopt the resistor according to actual design requirements. Anti-128 and energy storage unit 132.

The signal isolation unit 136 can also be an optocoupler for transmitting the feedback signal generated by the feedback circuit 134 to the PWM control circuit 126-1, so that the PWM control circuit 126-1 can adjust the responsibility of the PWM signal. The period, and thus the value of the output voltage VOUT2, can be stabilized within a preset range.

Referring to FIG. 1 again, as described above, the protection circuit includes a voltage abnormality detecting unit 200 and a protection trigger signal generating unit 300. The voltage abnormality detecting unit 200 receives the output voltages VOUT1 and VOUT2, and determines whether the output voltage VOUT1 is greater than a first preset value, and determines whether the output voltage VOUT2 is greater than a second preset value. When any of the above determination results is yes, A coupling signal is generated. The protection trigger signal generating unit 300 is configured to generate and latch the protection trigger signal TRI according to the coupling signal, and provide the protection trigger signal TRI to the PWM control circuits 108-1 and 126-1, thereby controlling the two PWM control circuits to stop respectively. Output PWM signal.

In the case that the switching power supply device 100 has only two different outputs, the voltage abnormality detecting unit 200 includes a diode 202, an impedance 204, a signal transmitting unit 206, an impedance 208, a voltage control switch 210, and a sigma diode. 212, impedance 214, impedance 216, diode 218, impedance 220, and impedance 222. The signal transmitting unit 206 has a first end 206-1 and a second end 206-2, and when the first end 206-1 and the second end 206-2 form an on state, the signal transmitting unit 206 generates the coupling signal. The signal transmitting unit 206 can be implemented by using a light emitting portion of an optical coupler. The voltage control switch 210 has a first end 210-1, a second end 210-2 and a reference end 210-3, and the first end 210-1 of the voltage control switch 210 is coupled to the second end 206-2 of the signal transmission unit 206. The second terminal 210-2 of the voltage control switch 210 is coupled to the reference potential VSS2. When the voltage of the reference terminal 210-3 of the voltage control switch 210 reaches the third preset value, the voltage control switch 210-3 causes the first end 210-1 and the second end 210-2 to be in an on state. The voltage control switch 210-3 can be implemented by using the switching elements of the TL431.

The anode of the diode 202 is configured to receive the output voltage VOUT1, and the impedance 204 is coupled between the cathode of the diode 202 and the first end 206-1 of the signal transmission unit 206. The anti-208 is connected in parallel with the signal transmitting unit 206. The cathode of the diode 212 is coupled to the cathode of the diode 202, and the anode through the impedance 214 is coupled to the reference terminal 210-3 of the voltage control switch 210, and is coupled to the reference potential VSS2 through the impedances 214 and 216 in sequence. The cathode of the diode 218 is coupled to the first end 206-1 of the signal transfer unit 206, and the anode transmits the output voltage VOUT2 through the impedance 220. As for the impedance 222, it is coupled between the output voltage VOUT2 and the reference terminal 210-3 of the voltage controlled switch 210.

In addition, in the case that the switching power supply device 100 has three different outputs, the voltage abnormality detecting unit 200 may further include a diode 224, an impedance 226, an arrester diode 228, and an impedance 230. The anode of the diode 224 is used to receive the output voltage VOUT3 of the switching power supply device 100, and the cathode is coupled to the cathode of the diode 228 through the impedance 226. The anode through the impedance 230 of the Zener diode 228 is coupled to the reference terminal 210-3 of the voltage controlled switch 210. In this way, the voltage abnormality detecting unit 200 can further determine whether the output voltage VOUT3 is greater than a fourth preset value, and when the determination is yes, the coupling signal is generated. In addition, assuming that the switched power supply device 100 has more than three different outputs, the designer can use a set of circuits indicated by the numeral 232 in the voltage abnormality detecting unit 200 for each additional output. If the switching power supply device 100 has N different outputs, the designer can use the circuit shown by the N-2 group flag 232 in the voltage abnormality detecting unit 200. In addition, in the voltage abnormality detecting unit 200, the impedances 204, 208, 214, 216, 220, 222, 226, and 230 can each be implemented by using a resistor, and the designer can decide whether to use the impedance 204 according to actual design requirements. 208, 220 and 226.

The protection trigger signal generating unit 300 includes an impedance 302, a signal receiving unit 304, an impedance 306, an impedance 308, a PNP type bipolar junction transistor 310, an impedance 312, an impedance 314, and an NPN type dual carrier junction transistor 316. Diode 318. The signal receiving unit 304 has a first end 304-1 and a second end 304-2, and when the signal receiving unit 304 receives the coupling signal, the first end 304-1 and the second end 304-2 are turned on. status. The signal receiving unit 304 can be implemented by using the light receiving portion in the same optical coupler as the signal transmitting unit 206. The first end 304-1 of the signal receiving unit 304 receives the operation through the impedance 302. The voltage VCC, and the second end 304-2 of the signal receiving unit 304 is coupled to the reference potential VSS1 through the impedance 306. The emitter E of the PNP-type bipolar junction transistor 310 receives the operating voltage VCC through the impedance 308, and the collector C of the PNP-type bipolar junction transistor 310 is coupled to the second end of the signal receiving unit 304 through the impedance 312. 304-2. The base B of the NPN-type bipolar junction transistor 316 is coupled to the second terminal 304-2 of the signal receiving unit 304 and coupled to the reference potential VSS1 through the impedance 306. The collector C of the NPN-type bipolar junction transistor 316 is coupled to the base B of the PNP-type bipolar junction transistor 310 through the impedance 314, and the emitter E coupling of the NPN-type bipolar junction transistor 316. Connect to the reference potential VSS1. As for the diode 318, the cathode is coupled to the collector C of the NPN-type bipolar junction transistor 316, and the anode is coupled to the PWM control circuit 108-1 and the PWM control circuit 126-1, and is used for outputting the protection trigger signal. TRI. In addition, in the protection trigger signal generating unit 300, the impedances 302, 306, 308, 312, and 314 can each be implemented by using a resistor, and the designer can decide whether to use the impedances 302, 308, 312, and 314 according to actual design requirements. Of course, the diode 318 can also be replaced by two other diodes, but the cathodes of the two diodes are coupled to the collector C of the NPN-type bipolar junction transistor 316. The anodes of the two diodes are coupled to the PWM control circuit 108-1 and the PWM control circuit 126-1, respectively.

Next, according to various problems faced by consumers during operation, the operation mode of the above protection circuit under different conditions will be explained. It should be noted that in the following description, the output voltage VOUT1 has the largest value, the output voltage VOUT2 has the smallest value, and the remaining output voltages are between the output voltages VOUT1 and VOUT2.

Assuming that the switching power supply device 100 has an overvoltage at the output terminal 100-1 after the power is turned on, when the output voltage VOUT1 rises to reach the first preset value, the output diode 212 is turned on due to the collapse. Further, when the partial pressure generated by the impedances 214 and 216 reaches a third preset value, for example, when the voltage is 2.5 volts (V), the voltage control switch 210-3 has its first end 210-1 and the second end 210-2. A conductive state is formed. As a result, the first end 206-1 and the second end 206-2 of the signal transmitting unit 206 also form an on state, so that the signal transmitting unit 206 generates a coupling signal. When the signal receiving unit 304 receives the above coupling signal In the case of the first end 304-1 and the second end 304-2, the NPN-type bipolar junction transistor 316 is pulled up to a high level due to the level of its base B. Presented in a conducting state. After the NPN-type bipolar junction transistor 316 is turned on, the PNP-type dual-carrier junction transistor 310 is also turned on due to the level of the base B being pulled down to a low level, thereby making the NPN type. The level of the base B of the bipolar junction transistor 316 is maintained at a high level. In this way, both the NPN-type bipolar junction transistor 316 and the PNP-type bipolar junction junction transistor 310 will have an interlocking effect due to the conduction state, and thus the cathode of the diode 318. The level continues to pull down at a low level, which is equivalent to retaining the overvoltage message. Therefore, once the diode 318 is turned on, the diode 318 generates a protection trigger signal TRI from its anode, thereby triggering the PWM control circuit 108-1 and the PWM control circuit 126-1 to cause the two to start performing overvoltage. The protection function, that is, the two respectively stop outputting the pulse width modulation signal, thereby causing the switching power supply device 100 to stop providing the output voltages VOUT1 and VOUT2.

Similarly, if the output terminal 100-2 has an overvoltage condition, then when the output voltage VOUT2 rises to reach the second preset value, so that the partial pressure generated by the impedances 222 and 216 reaches the third preset value, the signal The transmitting unit 206 also generates a coupling signal, so that the protection trigger signal generating unit 300 generates the protection trigger signal TRI. As another example, when the output voltage VOUT3 rises to reach the fourth preset value, the output diode 228 is turned on due to the collapse, so that the voltage generated by the impedances 230 and 216 reaches the third preset value, the signal The transmitting unit 206 also generates a coupling signal, so that the protection trigger signal generating unit 300 generates the protection trigger signal TRI.

In addition, it is assumed that the feedback circuit 120 or the signal isolation unit 122 in the switched power supply device 100 is damaged, and the consumer unknowingly turns on the switched power supply device 100. At this time, if the PWM control circuit 108-1 is powered on. The speed is faster than the PWM control circuit 126-1 is turned on (because the boot time of the two is difficult to maintain consistent), then the output voltage VOUT1 will be generated first, and will rise continuously to reach the first preset value, so that The diode 212 is turned on due to collapse, thereby causing the impedances 214 and 216 to be generated. The partial pressure reaches the third preset value. As a result, the signal transmission unit 206 also generates a coupling signal, so that the protection trigger signal generating unit 300 generates the protection trigger signal TRI, so that the PWM control circuit 108-1 stops outputting the pulse width modulation signal. Due to the interlocking effect of the NPN-type bipolar junction transistor 316 and the PNP-type bipolar junction transistor 310, the level of the cathode of the diode 318 is continuously pulled down at a low level, so once the PWM When the control circuit 126-1 is turned on, the PWM control circuit 126-1 also receives the protection trigger signal TRI and stops outputting the pulse width modulation signal.

Similarly, it is assumed that the feedback circuit 134 or the signal isolation unit 136 in the switched power supply device 100 is damaged, and the consumer unknowingly turns on the switched power supply device 100, and at this time, if the PWM control circuit 126-1 The startup speed is faster than the PWM control circuit 108-1 is turned on, then the output voltage VOUT2 is generated first, and will rise continuously to reach the second preset value, so that the partial pressure generated by the impedances 222 and 216 reaches the third preset. value. As a result, the signal transmission unit 206 also generates a coupling signal, so that the protection trigger signal generating unit 300 generates the protection trigger signal TRI, so that the PWM control circuit 126-1 stops outputting the pulse width modulation signal. Due to the interlocking effect of the NPN-type bipolar junction transistor 316 and the PNP-type bipolar junction transistor 310, the level of the cathode of the diode 318 is continuously pulled down at a low level, so once the PWM When the control circuit 108-1 is turned on, the PWM control circuit 108-1 also receives the protection trigger signal TRI and stops outputting the pulse width modulation signal.

In addition, assuming that the consumer turns the switched-mode power supply device 100 on, but accidentally short-circuits the output terminals 100-1 and 100-2 of the switched-mode power supply device 100 after power-on, the output voltage VOUT2 will rise continuously. The second preset value is reached, so that the partial pressure generated by the impedances 222 and 216 reaches a third preset value. As a result, the signal transmission unit 206 also generates a coupling signal, so that the protection trigger signal generating unit 300 generates the protection trigger signal TRI, so that the PWM control circuits 108-1 and 126-1 stop outputting the pulse width modulation signal.

In addition, it is assumed that the consumer accidentally causes the switching power supply device 100 to lose The terminals 100-1 and 100-2 are short-circuited, and the switching power supply device 100 is turned on without knowingly. At this time, if the PWM control circuit 108-1 is turned on faster than the PWM control circuit 126-1 is turned on. , then the output voltage VOUT1 will be generated first. Due to the short circuit relationship between the output terminals 100-1 and 100-2, the voltage division generated by the impedances 222 and 216 will soon reach the third preset value. As a result, the signal transmission unit 206 also generates a coupling signal, so that the protection trigger signal generating unit 300 generates the protection trigger signal TRI, so that the PWM control circuit 108-1 stops outputting the pulse width modulation signal. Due to the interlocking effect of the NPN-type bipolar junction transistor 316 and the PNP-type bipolar junction transistor 310, the level of the cathode of the diode 318 is continuously pulled down at a low level, so once the PWM When the control circuit 126-1 is turned on, the PWM control circuit 126-1 also receives the protection trigger signal TRI and stops outputting the pulse width modulation signal.

In summary, the present invention utilizes the voltage abnormality detecting unit to determine whether any of the output voltages of the switching power supply device exceeds its corresponding preset value, and therefore the output of the switching power supply device is The feedback circuit or the signal isolation unit fails to exhibit an overvoltage, or an overvoltage occurs due to the short circuit. When any of the determination results is yes, the voltage abnormality detecting unit generates a coupling signal to control the protection trigger signal generating unit to generate The protection trigger signal is latched, so that the control PWM control circuit stops outputting the pulse width modulation signal, and the two conditions of overvoltage and short circuit at the output end are protected.

100‧‧‧Switching power supply unit

100-1, 100-2‧‧‧ output

102‧‧‧ Noise Filter

104‧‧‧AC/DC converter circuit

106, 124‧‧‧Transformers

106-1, 106-2, 124-1‧‧‧ primary side coil

106-3, 124-2‧‧‧second side coil

108, 126‧‧‧ power level

108-1, 126-1‧‧‧ PWM control circuit

108-2, 126-2‧‧‧ Power transistors

110, 128, 204, 208, 214, 216, 220, 222, 226, 230, 302, 306, 308, 312, 314‧‧‧ impedance

112, 116, 130‧‧‧Rectifier circuit

114, 118, 132‧‧‧ energy storage unit

120, 134‧‧ ‧ feedback circuit

122, 136‧‧‧ signal isolation unit

202, 218, 224, 318‧‧‧ diodes

206‧‧‧Signal transmission unit

206-1, 210-1, 304-1‧‧‧ first end

206-2, 210-2, 304-2‧‧‧ second end

200‧‧‧Voltage abnormality detection unit

210‧‧‧Voltage control switch

210-3‧‧‧ Reference

212, 228‧‧ ‧ Jenus diode

232‧‧‧ Circuitry

300‧‧‧Protection trigger signal generation unit

304‧‧‧Signal receiving unit

310‧‧‧PNP type double carrier junction transistor

316‧‧‧NPN type double carrier junction transistor

B‧‧‧ base

C‧‧‧集极

E‧‧‧射极

TRI‧‧‧protection trigger signal

VCC‧‧‧ operating voltage

VIN‧‧‧ input voltage

VOUT1, VOUT2, VOUT3, VOUTN‧‧‧ output voltage

VSS1, VSS2‧‧‧ reference potential

Claims (4)

A protection circuit is applicable to a switching power supply device having multiple outputs, the protection circuit comprising: a voltage abnormality detecting unit, receiving a first output voltage and a second output voltage of the switched power supply device, Determining whether the first output voltage is greater than a first predetermined value, and determining whether the second output voltage is greater than a second predetermined value. When any of the determination results is YES, a coupling signal is generated; The protection trigger signal generating unit is configured to generate and latch a protection trigger signal according to the coupling signal, and provide the protection trigger signal to a first pulse width modulation control circuit and a second pulse of the switching power supply device The wide modulation control circuit further controls the first pulse width modulation control circuit and the second pulse width modulation control circuit to stop outputting a first pulse width modulation signal and a second pulse width modulation signal, respectively. The protection circuit of claim 1, wherein the voltage abnormality detecting unit comprises: a first diode having an anode for receiving the first output voltage; and a second diode for an anode Receiving the second output voltage; a signal transmission unit having a first end and a second end, the first end being coupled to the cathode of the first diode and the cathode of the second diode, and The signal transmitting unit generates the coupling signal when the first end and the second end are in an on state; the voltage control switch has a third end, a fourth end and a reference end, and the third end is coupled The second end is coupled to a reference potential, and when the voltage of the reference terminal reaches a third preset value, the voltage control switch causes the third end to form a conducting state with the fourth end; a first inductor, the cathode of which is coupled to the cathode of the first diode; a first impedance, one end of which is coupled to the anode of the first gated diode; and a second impedance coupled to one end thereof The first impedance of the other End, while the other end of the second resistor coupled to the reference potential; and a third impedance having one end coupled to an anode of the second diode and the other end coupled to the reference potential. The protection circuit of claim 2, wherein the voltage abnormality detecting unit further receives a third output voltage of the switching power supply device, and further determines whether the third output voltage is greater than a fourth The preset value, when the determination is yes, the coupling signal is generated, the voltage abnormality detecting unit further comprises: a third diode, the anode is configured to receive the third output voltage; a cathode having a cathode coupled to the cathode of the third diode; and a fourth impedance coupled to the anode of the second arrester diode and coupled to the other end of the first impedance. The protection circuit of claim 1, wherein the protection trigger signal generating unit comprises: a signal receiving unit having a first end and a second end, wherein the first end is configured to receive an operating voltage, and When the signal receiving unit receives the coupling signal, the first end and the second end are in an on state; an impedance is coupled to the second end at one end and coupled to a reference potential at the other end; a dual-carrier junction transistor, the PNP-type dual-carrier junction transistor has a first emitter, a first base and a first collector, the first emitter for receiving the operating voltage; An NPN type bipolar junction transistor having a second emitter, a second base and a second collector, the second base coupled to the second And the first collector, the second collector is coupled to the first base, and the second emitter is coupled to the reference potential; and a diode having a cathode coupled to the second collector The anode is coupled to the first pulse width modulation control circuit and the second pulse Modulation control circuit, and for outputting the trigger signal protection.