CN218387263U - Output overcurrent protection circuit of switching power supply - Google Patents
Output overcurrent protection circuit of switching power supply Download PDFInfo
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- CN218387263U CN218387263U CN202222759827.3U CN202222759827U CN218387263U CN 218387263 U CN218387263 U CN 218387263U CN 202222759827 U CN202222759827 U CN 202222759827U CN 218387263 U CN218387263 U CN 218387263U
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Abstract
The utility model discloses an output overcurrent protection circuit of a switch power supply, which comprises an output current sampling resistor, a first voltage division circuit, a first voltage stabilization reference source and an overcurrent protection signal output circuit, wherein the switch power supply comprises a main circuit and a control circuit, the main circuit comprises a direct current output end, and the control circuit comprises a controller; the first end of the first voltage division circuit is connected with the reference voltage, and the second end of the first voltage division circuit is connected with the negative electrode of the direct current output end; the output current sampling resistor is connected between the negative electrode of the direct current output end and the ground, and the voltage signal output end of the first voltage division circuit is connected with the reference electrode of the first voltage stabilization reference source; the anode of the first voltage-stabilizing reference source is grounded, the cathode of the first voltage-stabilizing reference source is connected with the input end of the overcurrent protection signal output circuit, and the output end of the overcurrent protection signal output circuit is connected with the overcurrent protection signal input end of the controller. The utility model discloses can draw down output current rapidly when the main circuit overflows, protection preceding stage power device does not receive the damage, and the protection action is rapid, and is accurate, and circuit cost is lower.
Description
[ technical field ]
The utility model relates to a switching power supply especially relates to a switching power supply's output overcurrent protection circuit.
[ background art ]
The switching power supply has the advantages of lightness, high frequency, low power consumption, high efficiency, low noise and the like, and is widely applied to the fields of various household appliances, industrial equipment, military electronic equipment, instruments, industrial automation and the like. However, with the wide application of the switching power supply, the reliability of the switching power supply is also required to be higher, the performance of the switching power supply is required to meet the requirements of power supply equipment, the protection measures of the switching power supply are also required to be improved, once the power supply output is over-current, the switching power supply needs to shut off the output voltage of the switching power supply, and a rear-stage system is protected from being damaged.
The utility model with patent number CN202123391494.5 discloses a switching power supply output overcurrent protection circuit and a switching power supply, the circuit comprises an overcurrent protection main circuit, a pulse width modulation chip voltage overcurrent closing circuit and a sampling reference circuit; the overcurrent protection main circuit is connected with the pulse width modulation chip voltage overcurrent closing circuit, and the sampling reference circuit is connected with the overcurrent protection main circuit. The utility model discloses an adopt operational amplifier to realize overcurrent protection, circuit structure is complicated, and the reaction of protection action is slower.
[ summary of the invention ]
The to-be-solved technical problem of the utility model is to provide a fast switching power supply's of protection action output overcurrent protection circuit.
In order to solve the technical problem, the utility model adopts the technical scheme that an output overcurrent protection circuit of a switching power supply comprises an output current sampling resistor, a first voltage division circuit, a first voltage stabilization reference source and an overcurrent protection signal output circuit, wherein the switching power supply comprises a main circuit and a control circuit, the main circuit comprises a direct current output end, and the control circuit comprises a controller; the first end of the first voltage division circuit is connected with the reference voltage, and the second end of the first voltage division circuit is connected with the negative electrode of the direct current output end; the output current sampling resistor is connected between the negative electrode of the direct current output end and the ground, and the voltage signal output end of the first voltage division circuit is connected with the reference electrode of the first voltage stabilization reference source; the anode of the first voltage-stabilizing reference source is grounded, the cathode of the first voltage-stabilizing reference source is connected with the input end of the overcurrent protection signal output circuit, and the output end of the overcurrent protection signal output circuit is connected with the overcurrent protection signal input end of the controller.
In the output overcurrent protection circuit, the overcurrent protection signal output circuit comprises an optical coupler and an MOS (metal oxide semiconductor) tube, wherein the anode of an optical coupler light-emitting diode is connected with the anode of a first auxiliary power supply through a first current-limiting resistor, and the cathode of the optical coupler light-emitting diode is connected with the cathode of a first voltage-stabilizing reference source; the collector of the optocoupler phototriode is connected with the anode of the second auxiliary power supply through a second current-limiting resistor, and the emitter of the optocoupler phototriode is connected with the grid of the MOS tube; the grid of the MOS tube is connected with a primary power ground through a pull-down resistor; the source electrode of the MOS tube is connected with the primary side power ground, and the drain electrode of the MOS tube is connected with the overcurrent protection signal input end of the controller.
In the output overcurrent protection circuit, the overcurrent protection signal output circuit comprises a fifth capacitor and a sixth capacitor, the fifth capacitor is connected with the pull-down resistor in parallel, and the sixth capacitor is connected between the source electrode and the drain electrode of the MOS transistor.
The output overcurrent protection circuit comprises a first resistor, a third resistor and a first capacitor, wherein the first resistor is connected between the cathode of the first voltage-stabilizing reference source and the anode of the first auxiliary power supply; the third resistor is connected in series with the first capacitor and then connected between the voltage signal output end of the first voltage division circuit and the cathode of the first voltage stabilization reference source.
The output overcurrent protection circuit comprises a reference voltage source, wherein the reference voltage source comprises a second voltage-stabilizing reference source and a second voltage division circuit; the cathode of the second voltage-stabilizing reference source is connected with the anode of the first auxiliary power supply through a fourth current-limiting resistor, and the anode of the second voltage-stabilizing reference source is connected with the cathode of the direct-current output end; the first end of the second voltage division circuit is connected with the cathode of the second voltage stabilization reference source, the second end of the second voltage division circuit is connected with the anode of the second voltage stabilization reference source, and the voltage signal output end of the second voltage division circuit is connected with the reference electrode of the second voltage stabilization reference source; the cathode of the second voltage-stabilizing reference source is used as the output end of the reference voltage and is connected with the first end of the first voltage division circuit.
In the output overcurrent protection circuit, the reference voltage source includes the second capacitor, and the second capacitor is connected between the anode of the second voltage-stabilizing reference source and the reference electrode.
In the output overcurrent protection circuit, the main circuit comprises the output capacitor, and the output capacitor is connected between the anode and the cathode of the direct current output end.
The utility model discloses can draw down output current rapidly when the main circuit overflows, protection preceding stage power device does not receive the damage, and the protection action is rapid, and is accurate, and circuit cost is lower.
[ description of the drawings ]
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a wiring diagram of a controller according to an embodiment of the present invention.
Fig. 2 is a circuit diagram of an output overcurrent protection circuit according to an embodiment of the present invention.
Fig. 3 is an equivalent circuit diagram of the circuit of fig. 2 according to the embodiment of the present invention.
[ detailed description of the invention ]
The embodiment of the utility model provides a switching power supply's output overcurrent protection circuit's structure is shown in figure 1 and figure 3. The switching power supply comprises a main circuit and a control circuit, wherein the main circuit comprises a direct current output end, and an output capacitor C4 is connected between the positive pole VOUT + and the negative pole VOUT-of the direct current output end. The control circuit comprises a microcontroller IC4.
The output overcurrent protection circuit comprises an output current sampling resistor R11, a first voltage division circuit, a first voltage stabilization reference source IC2 (431 voltage stabilization reference source), a reference voltage source and an overcurrent protection signal output circuit.
The first voltage division circuit is composed of resistors R5, R6, R7 and R8, the first end of the first voltage division circuit is connected with a reference voltage output end of a reference voltage source, and the second end of the first voltage division circuit is connected with a negative pole VOUT-of a direct current output end. The output current sampling resistor R11 is connected between the negative pole VOUT-of the DC output terminal and the output sampling ground GND. The voltage signal output end of the first voltage division circuit is connected with the reference pole of the first voltage stabilization reference source IC 2. The third resistor R3 is connected in series with the first capacitor C1 and then connected between the voltage signal output end of the first voltage division circuit and the cathode of the first voltage-stabilizing reference source IC2, the anode of the first voltage-stabilizing reference source IC2 is connected with the output sampling ground GND, the cathode of the first voltage-stabilizing reference source IC2 is connected with the input end of the overcurrent protection signal output circuit, and the output pin OCP of the overcurrent protection signal output circuit is connected with the overcurrent protection signal input pin VB/PFCFB of the microcontroller IC4. The third resistor R3 and the first capacitor C1 form a response loop, and the response time is determined by T = Rc.
The overcurrent protection signal output circuit comprises an optical coupler IC1 and an MOS tube Q1, the anode of an optical coupler light-emitting diode IC1-B is connected with the anode VCCS of the first auxiliary power supply through a first current-limiting resistor R2, the cathode of the optical coupler light-emitting diode IC1-B is connected with the cathode of the first voltage-stabilizing reference source IC2, and the first resistor R1 is connected between the cathode of the first voltage-stabilizing reference source IC2 and the anode VCCS of the first auxiliary power supply. The collector of the opto-coupler IC1 phototriode is connected with the positive pole VCCA of the second auxiliary power supply through a second current-limiting resistor R12, and the emitter of the opto-coupler IC1 phototriode IC1-A is connected with the grid of the MOS tube Q1. The grid of the MOS transistor Q1 is connected with a primary power ground GND1 through a pull-down resistor R13, and a fifth capacitor C5 is connected with the pull-down resistor R13 in parallel. (the GND1 is what) the source of the MOS transistor Q1 is connected with the primary power ground GND1, and the sixth capacitor C6 is connected between the source and the drain of the MOS transistor Q1. The drain of the MOS transistor Q1 is connected with an overcurrent protection signal input pin VB/PFCFB of the microcontroller IC4.
The reference voltage source includes a second regulated reference IC3 (431 regulated reference) and a second voltage dividing circuit. The second voltage dividing circuit is formed by connecting a resistor R9 and a resistor R10 in series, the cathode of the second voltage-stabilizing reference source IC3 is connected with the positive pole VCCS of the first auxiliary power supply through a fourth current-limiting resistor R4, and the anode of the second voltage-stabilizing reference source IC3 is connected with the negative pole VOUT-of the direct current output end. The first end of the second voltage division circuit is connected with the cathode of the second voltage stabilization reference source IC3, the second end of the second voltage division circuit is connected with the anode of the second voltage stabilization reference source IC3, and the voltage signal output end (the connection point of the resistor R9 and the resistor R10 in series) of the second voltage division circuit is connected with the reference electrode of the second voltage stabilization reference source IC 3. The second capacitor C2 is connected between the anode of the second voltage-stabilizing reference source IC3 and the reference electrode. The cathode of the second voltage-stabilizing reference source IC3 is used as the output end of the reference voltage and is connected with the first end of the first voltage division circuit.
As shown in fig. 2 and fig. 3, after the first auxiliary power source VCCS supplies power to the second regulated reference power source IC3 through the resistor R4, the IC3 is normally turned on, and at this time, the reference pole of the second regulated reference power source IC3 generates a reference voltage of 2.5V, that is, the voltage to ground of the reference pole of the second regulated reference power source IC3 = U1=2.5V at both ends of the resistor R10, the voltage U4 is obtained by voltage division of the resistor R9 and the resistor R10, and the voltage U3, that is, uab, that is, the voltage divided by the resistor R8 through a voltage division network (first voltage division circuit) in which the resistor R5 is connected in series with R6// R7 and R8, is obtained; when the switching power supply normally works, the current Io between the positive pole VOUT + and the negative pole VOUT-of the direct current output end is converted into voltage U2, namely Ubc through the sampling resistor R11; uac is the input of a voltage comparator of the second voltage-stabilizing reference source IC2, and the internal reference voltage of the second voltage-stabilizing reference source IC2 is 2.5V; when U2+ U3 is greater than 2.5V and reaches the action potential of a reference electrode of a second voltage-stabilizing reference source IC2, the second voltage-stabilizing reference source IC2 is conducted, after the second voltage-stabilizing reference source IC2 is conducted, an optical coupler light-emitting diode IC1-B is also conducted in sequence to emit a light signal, an optical coupler phototriode IC1-A is conducted after receiving the light signal, the level of a grid electrode of an MOS tube Q1 is pulled high, and after the MOS tube Q1 is conducted, the level of an overcurrent protection signal input pin VB/PFCFB of a microcontroller IC4 is quickly pulled low to trigger overcurrent protection.
The utility model discloses above embodiment switching power supply's output overcurrent protection circuit utilizes the opto-coupler to primary side transmission light signal, utilizes 431's reference voltage as the actuating signal, can reduce the output current of main circuit rapidly when overflowing, protects preceding stage power device not damaged. The utility model discloses above embodiment protection action is rapid, and is accurate, and the circuit cost is lower.
Claims (7)
1. An output overcurrent protection circuit of a switching power supply comprises a main circuit and a control circuit, wherein the main circuit comprises a direct current output end, and the control circuit comprises a controller; the output current sampling resistor is connected between the negative electrode of the direct current output end and the ground, and the voltage signal output end of the first voltage division circuit is connected with the reference electrode of the first voltage stabilization reference source; the anode of the first voltage-stabilizing reference source is grounded, the cathode of the first voltage-stabilizing reference source is connected with the input end of the overcurrent protection signal output circuit, and the output end of the overcurrent protection signal output circuit is connected with the overcurrent protection signal input end of the controller.
2. The output overcurrent protection circuit of claim 1, wherein the overcurrent protection signal output circuit comprises an optocoupler and an MOS transistor, an anode of an optocoupler light emitting diode is connected to an anode of the first auxiliary power supply through a first current limiting resistor, and a cathode of the optocoupler light emitting diode is connected to a cathode of the first voltage-stabilizing reference source; the collector of the optocoupler phototriode is connected with the anode of the second auxiliary power supply through a second current-limiting resistor, and the emitter of the optocoupler phototriode is connected with the grid of the MOS tube; the grid of the MOS tube is connected with a primary side power ground through a pull-down resistor; the source electrode of the MOS tube is connected with the primary power ground, and the drain electrode of the MOS tube is connected with the overcurrent protection signal input end of the controller.
3. The output overcurrent protection circuit of claim 2, wherein the overcurrent protection signal output circuit comprises a fifth capacitor and a sixth capacitor, the fifth capacitor is connected in parallel with the pull-down resistor, and the sixth capacitor is connected between the source and the drain of the MOS transistor.
4. The output overcurrent protection circuit of claim 1, comprising a first resistor, a third resistor, and a first capacitor, wherein the first resistor is connected between the cathode of the first regulated reference source and the anode of the first auxiliary power supply; the third resistor is connected in series with the first capacitor and then connected between the voltage signal output end of the first voltage division circuit and the cathode of the first voltage stabilization reference source.
5. The output overcurrent protection circuit of claim 1, comprising a reference voltage source, wherein the reference voltage source comprises a second regulated reference source and a second voltage divider circuit; the cathode of the second voltage-stabilizing reference source is connected with the anode of the first auxiliary power supply through a fourth current-limiting resistor, and the anode of the second voltage-stabilizing reference source is connected with the cathode of the direct-current output end; the first end of the second voltage division circuit is connected with the cathode of the second voltage stabilization reference source, the second end of the second voltage division circuit is connected with the anode of the second voltage stabilization reference source, and the voltage signal output end of the second voltage division circuit is connected with the reference electrode of the second voltage stabilization reference source; the cathode of the second voltage-stabilizing reference source is used as the output end of the reference voltage and is connected with the first end of the first voltage division circuit.
6. The output overcurrent protection circuit of claim 1, wherein the reference voltage source comprises a second capacitor, and the second capacitor is coupled between an anode of the second regulated reference and the reference electrode.
7. The output overcurrent protection circuit of claim 1, wherein the main circuit comprises an output capacitor, and the output capacitor is connected between a positive pole and a negative pole of the dc output terminal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222759827.3U CN218387263U (en) | 2022-10-20 | 2022-10-20 | Output overcurrent protection circuit of switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222759827.3U CN218387263U (en) | 2022-10-20 | 2022-10-20 | Output overcurrent protection circuit of switching power supply |
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| Publication Number | Publication Date |
|---|---|
| CN218387263U true CN218387263U (en) | 2023-01-24 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202222759827.3U Active CN218387263U (en) | 2022-10-20 | 2022-10-20 | Output overcurrent protection circuit of switching power supply |
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| Country | Link |
|---|---|
| CN (1) | CN218387263U (en) |
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2022
- 2022-10-20 CN CN202222759827.3U patent/CN218387263U/en active Active
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