CN214100826U - Secondary overcurrent protection circuit of switching power supply - Google Patents
Secondary overcurrent protection circuit of switching power supply Download PDFInfo
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- CN214100826U CN214100826U CN202121800573.4U CN202121800573U CN214100826U CN 214100826 U CN214100826 U CN 214100826U CN 202121800573 U CN202121800573 U CN 202121800573U CN 214100826 U CN214100826 U CN 214100826U
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Abstract
The utility model discloses a switch power supply secondary side overcurrent protection circuit, which comprises a current sampling resistor, a voltage amplifying circuit, a voltage comparison circuit and an overcurrent protection signal output circuit of the switch power supply secondary side, wherein the voltage amplifying circuit comprises an amplifier, and the voltage comparison circuit comprises a comparator; the first input end of the amplifier is connected with the first end of the current sampling resistor, and the second input end of the amplifier is connected with the second end of the current sampling resistor; the non-inverting input end of the comparator is connected with the output end of the amplifier, and the non-inverting input end of the comparator is connected with the output end of the amplifier and the reference voltage; the output end of the comparator is connected with the overcurrent protection signal output circuit. The utility model discloses a voltage to vice limit current sampling resistance carries out real-time sampling and with reference voltage comparison and then form corresponding control signal, realized switching power supply when overflowing quick protection, improved switching power supply's reliability.
Description
Technical Field
The utility model relates to a switching power supply especially relates to a switching power supply secondary limit overcurrent protection circuit.
Background
The current signal of the primary side of the transformer is detected by a switch power supply through an overcurrent protection method commonly adopted by the switch power supply, an action threshold value is set through a comparator, when the current of the primary side is increased and reaches a set value of the action of a chip, the chip closes a driving circuit, and finally a switch tube in a power switch circuit is turned off to realize overcurrent protection. The disadvantage of this protection method is that when the output end of the switching power supply is short-circuited and the output current is rapidly increased to cause the primary side current of the transformer to increase and reach the chip action value, an action signal is generated, the drive is closed, and the switching tube of the power switching circuit is turned off. The delay in this process creates the risk of damage to the switches in the power switching circuit due to excessive VDS spikes.
Disclosure of Invention
The to-be-solved technical problem of the utility model is to provide a switching power supply secondary overcurrent protection circuit that can realize the protection when secondary overflows fast.
In order to solve the technical problem, the utility model adopts the technical scheme that the switch power supply secondary overcurrent protection circuit comprises a current sampling resistor, a voltage amplifying circuit, a voltage comparison circuit and an overcurrent protection signal output circuit, wherein the current sampling resistor, the voltage amplifying circuit, the voltage comparison circuit and the overcurrent protection signal output circuit are arranged on the switch power supply secondary side; the first input end of the amplifier is connected with the first end of the current sampling resistor, and the second input end of the amplifier is connected with the second end of the current sampling resistor; the non-inverting input end of the comparator is connected with the output end of the amplifier, and the non-inverting input end of the comparator is connected with the output end of the amplifier and the reference voltage; the output end of the comparator is connected with the overcurrent protection signal output circuit.
In the secondary side overcurrent protection circuit of the switching power supply, the voltage amplification circuit comprises a first resistor, a second resistor and a third resistor, and the first end of the current sampling resistor is connected with the secondary ground; the non-inverting input end of the amplifier is connected with the first end of the current sampling resistor through a second resistor, and the inverting input end of the amplifier is connected with the second end of the current sampling resistor through the second resistor; the third resistor is connected between the output end and the inverting input end of the amplifier.
In the above-mentioned secondary side overcurrent protection circuit of the switching power supply, the voltage amplification circuit includes the first capacitor and the second capacitor, the first capacitor is connected between the non-inverting input terminal and the inverting input terminal of the amplifier, and the second capacitor is connected in parallel with the third resistor.
In the above-mentioned secondary side overcurrent protection circuit of the switching power supply, the voltage comparison circuit includes the fourth resistor, the fifth resistor, the sixth resistor and the third capacitor, the non-inverting input terminal of the comparator is connected to the reference voltage through the fifth resistor, the inverting input terminal is connected to the output terminal of the amplifier through the fourth resistor, and the sixth resistor and the third capacitor are connected in series and then connected between the output terminal and the inverting input terminal of the comparator.
In the secondary side overcurrent protection circuit of the switching power supply, the fourth resistor and the fifth resistor have the same resistance value.
In the secondary side overcurrent protection circuit of the switching power supply, the overcurrent protection signal output circuit comprises a diode and a seventh resistor, the seventh resistor is connected in series between the output end of the comparator and the cathode of the diode, and the anode of the diode is used as the output end of the overcurrent protection signal output circuit.
The secondary side overcurrent protection circuit of the switching power supply comprises a reference voltage sampling circuit, wherein the reference voltage sampling circuit comprises a controllable precise voltage-stabilizing source, an eighth resistor and a fourth capacitor; the cathode of the controllable precise voltage-stabilizing source is connected with the anode of the direct-current power supply through an eighth resistor; the fourth capacitor is connected between the cathode and the anode of the controllable precise voltage-stabilizing source, and the anode of the controllable precise voltage-stabilizing source is connected with the secondary ground; the control end of the controllable precise voltage-stabilizing source is connected with the cathode of the controllable precise voltage-stabilizing source; the cathode of the controllable precise voltage-stabilizing source is used as the output end of the reference voltage.
The utility model discloses a voltage to vice limit current sampling resistance carries out real-time sampling and with reference voltage comparison and then form corresponding control signal, realized switching power supply when overflowing quick protection, improved switching power supply's reliability.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a schematic block diagram of a secondary overcurrent protection circuit of a switching power supply according to an embodiment of the present invention.
Fig. 2 is a circuit diagram of the secondary overcurrent protection circuit of the switching power supply according to the embodiment of the present invention.
Detailed Description
The embodiment of the utility model provides a secondary limit overcurrent protection circuit's of switching power supply structure and principle are shown in fig. 1 and fig. 2, current sampling resistance RS1, voltage amplifier circuit, voltage comparison circuit, reference voltage sampling circuit and overcurrent protection signal output circuit including the secondary limit of switching power supply.
The current sampling resistor RS1 is connected in series with the negative terminal of the output of the switching power supply, and the first terminal of the current sampling resistor RS1 is connected with the secondary ground AGND. When the output current of the switching power supply changes, the voltage at the two ends of the current sampling resistor RS1 changes along with the change of the output current, and the change of the output current can be converted into the change of a voltage signal.
The voltage amplifying circuit comprises an amplifier U3-A, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1 and a second capacitor C2. The non-inverting input terminal of the amplifier U3-A is connected with the first terminal of the current sampling resistor RS1 through the second resistor R2, and the inverting input terminal of the amplifier U3-A is connected with the second terminal of the current sampling resistor RS1 through the second resistor R2. The third resistor R3 is connected between the output and the inverting input of the amplifier U3-A. The first capacitor C1 is connected between the non-inverting input terminal and the inverting input terminal of the amplifier U3-A for negative feedback, and the second capacitor C2 is connected in parallel with the third resistor R3. Adjusting resistor R3 may change the amplification of the voltage.
The voltage comparison circuit comprises a comparator U3-B, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a third capacitor C3, wherein the non-inverting input end of the comparator U3-B is connected with the reference voltage provided by the reference voltage sampling circuit through the fifth resistor R5, the inverting input end of the comparator U3-B is connected with the output end of the amplifier U3-A through the fourth resistor R4, and the sixth resistor R6 and the third capacitor C3 are connected between the output end and the inverting input end of the comparator U3-B after being connected in series. The fifth resistor R5 and the fourth resistor R4 have the same resistance.
The overcurrent protection signal output circuit comprises a diode D1 and a seventh resistor R7, the seventh resistor R7 is connected in series between the output end of the comparator U3-B and the cathode of the diode D1, and the anode of the diode D1 serves as the output end of the overcurrent protection signal output circuit.
The reference voltage connected with the non-inverting input end of the comparator U3-B is 2.5V, when the voltage input by the inverting input end of the comparator U3-B is less than 2.5V, the output of the comparator U3-B is high level, and the switching power supply circuit works normally; when the voltage input by the inverting input end of the comparator U3-B is more than 2.5V, the output of the comparator U3-B is at a low level, the diode D1 is conducted at the moment, and the switching power supply carries out overcurrent protection.
The reference voltage sampling circuit comprises a controllable precise voltage regulator U1, an eighth resistor R8 and a fourth capacitor C4. The cathode of the controllable precise voltage-stabilizing source U1 is connected with the anode of the 2V4 direct-current power supply (the anode of the secondary side voltage output end of the switching power supply) through an eighth resistor R8. The fourth capacitor C4 is connected between the cathode and the anode of the controllable precise voltage regulator U1, and the anode of the controllable precise voltage regulator U1 is connected to the secondary ground AGND. The control end of the controllable precise voltage stabilizing source U1 is connected with the cathode of the controllable precise voltage stabilizing source U1. And the cathode of the controllable precise voltage-stabilizing source U1 is used as an output end of the reference voltage.
The utility model discloses when the vice limit of switching power supply overcurrent protection circuit of above embodiment is higher than the reference pole voltage of controllable accurate steady voltage source when the voltage of the reverse phase input of comparator input, the power overcurrent protection has realized that output draws down rapidly when overflowing, has reduced the electric current when switch tube turn-offs in other words to reduce switching power supply switch tube's transient stress, improved switching power supply's reliability.
Claims (7)
1. A secondary side overcurrent protection circuit of a switching power supply comprises a current sampling resistor on the secondary side of the switching power supply, and is characterized by comprising a voltage amplification circuit, a voltage comparison circuit and an overcurrent protection signal output circuit, wherein the voltage amplification circuit comprises an amplifier, and the voltage comparison circuit comprises a comparator; the first input end of the amplifier is connected with the first end of the current sampling resistor, and the second input end of the amplifier is connected with the second end of the current sampling resistor; the non-inverting input end of the comparator is connected with the output end of the amplifier, and the non-inverting input end of the comparator is connected with the output end of the amplifier and the reference voltage; the output end of the comparator is connected with the overcurrent protection signal output circuit.
2. The switching power supply secondary side overcurrent protection circuit according to claim 1, wherein the voltage amplification circuit comprises a first resistor, a second resistor and a third resistor, and a first end of the current sampling resistor is connected with a secondary ground; the non-inverting input end of the amplifier is connected with the first end of the current sampling resistor through a second resistor, and the inverting input end of the amplifier is connected with the second end of the current sampling resistor through the second resistor; the third resistor is connected between the output end and the inverting input end of the amplifier.
3. The switching power supply secondary side overcurrent protection circuit according to claim 2, wherein the voltage amplification circuit comprises a first capacitor and a second capacitor, the first capacitor is connected between a non-inverting input terminal and an inverting input terminal of the amplifier, and the second capacitor is connected in parallel with the third resistor.
4. The switching power supply secondary side overcurrent protection circuit according to claim 1, wherein the voltage comparison circuit comprises a fourth resistor, a fifth resistor, a sixth resistor and a third capacitor, a non-inverting input terminal of the comparator is connected to the reference voltage through the fifth resistor, an inverting input terminal of the comparator is connected to the output terminal of the amplifier through the fourth resistor, and the sixth resistor and the third capacitor are connected in series and then connected between the output terminal and the inverting input terminal of the comparator.
5. The switching power supply secondary side overcurrent protection circuit according to claim 4, wherein the fourth resistor and the fifth resistor have the same resistance value.
6. The switching power supply secondary side overcurrent protection circuit according to claim 1, wherein the overcurrent protection signal output circuit includes a diode and a seventh resistor, the seventh resistor is connected in series between the output terminal of the comparator and the cathode of the diode, and the anode of the diode serves as the output terminal of the overcurrent protection signal output circuit.
7. The switching power supply secondary side overcurrent protection circuit according to claim 1, comprising a reference voltage sampling circuit, wherein the reference voltage sampling circuit comprises a controllable precision voltage-stabilizing source, an eighth resistor and a fourth capacitor; the cathode of the controllable precise voltage-stabilizing source is connected with the anode of the direct-current power supply through an eighth resistor; the fourth capacitor is connected between the cathode and the anode of the controllable precise voltage-stabilizing source, and the anode of the controllable precise voltage-stabilizing source is connected with the secondary ground; the control end of the controllable precise voltage-stabilizing source is connected with the cathode of the controllable precise voltage-stabilizing source; the cathode of the controllable precise voltage-stabilizing source is used as the output end of the reference voltage.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121800573.4U CN214100826U (en) | 2021-08-04 | 2021-08-04 | Secondary overcurrent protection circuit of switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121800573.4U CN214100826U (en) | 2021-08-04 | 2021-08-04 | Secondary overcurrent protection circuit of switching power supply |
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| CN214100826U true CN214100826U (en) | 2021-08-31 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202121800573.4U Active CN214100826U (en) | 2021-08-04 | 2021-08-04 | Secondary overcurrent protection circuit of switching power supply |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114089226A (en) * | 2022-01-18 | 2022-02-25 | 成都市安比科技有限公司 | Active load detection circuit with anti-static damage and controllable overcurrent protection functions |
| CN114725897A (en) * | 2022-04-11 | 2022-07-08 | 北京伽略电子股份有限公司 | Overcurrent protection circuit for switching power supply |
-
2021
- 2021-08-04 CN CN202121800573.4U patent/CN214100826U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114089226A (en) * | 2022-01-18 | 2022-02-25 | 成都市安比科技有限公司 | Active load detection circuit with anti-static damage and controllable overcurrent protection functions |
| CN114725897A (en) * | 2022-04-11 | 2022-07-08 | 北京伽略电子股份有限公司 | Overcurrent protection circuit for switching power supply |
| CN114725897B (en) * | 2022-04-11 | 2022-11-29 | 北京伽略电子股份有限公司 | Overcurrent protection circuit for switching power supply |
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