A short-circuit protection circuit

The short-circuit protection circuit in SMPS dynamically adjusts to limit small short-circuit currents, enhancing protection and reducing complexity and costs by integrating a switch control and op-amp sampling module.

CN115118145BActive Publication Date: 2025-07-15MORNSUN GUANGZHOU SCI & TECH
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Patent Information

Application Number
CN202210802534.0
Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Filing Date
2022-07-07
Publication Date
2025-07-15
Estimated Expiration
2042-07-07

AI Technical Summary

Technical Problem

The existing short-circuit protection circuit of switching power supply cannot effectively limit the small short-circuit current, and there are problems of high cost and complex structure.

Method used

The short-circuit protection circuit is adopted, including the switch control module, the op-amp sampling module and the short-circuit control module. The voltage signal is compared through the op-amp sampling module, and the switching control module is controlled to limit the short-circuit current.

Benefits of technology

The short circuit protection of switching power supplies is achieved, which can limit the small short circuit current, reduce circuit complexity and cost, and protect the load and switching power supplies from damage.

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Abstract

The present invention discloses a short - circuit protection circuit applied to a switching power supply, which includes a switch control module, an operational amplifier sampling module, and a short - circuit control module. The switch control module is used to sample the input voltage of the switching power supply and use it as the reference voltage of the operational amplifier sampling module. The short - circuit control module is used to output a first voltage signal to the operational amplifier sampling module when the load is normal, or to limit the magnitude of the short - circuit current of the load and output a second voltage signal to the operational amplifier sampling module when the load is short - circuited. The operational amplifier sampling module is used to compare the first voltage signal or the second voltage signal with the reference voltage, and when the first voltage signal is less than the reference voltage, control the switch control module to conduct, so that the switching power supply forms a path with the load, and when the second voltage signal is greater than the reference voltage, control the switch control module to turn off, so that the switching power supply is open - circuited with the load. The present invention can add a short - circuit protection function to the switching power supply and limit the short - circuit protection current according to the application situation.
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Description

Technical Field

[0001] The present invention relates to switching power supply technology, and particularly to the protection control of a switching power supply under short - circuit conditions. Background Art

[0002] The short - circuit protection function of a switching power supply is one of its main indicators. Short - circuit protection is the protection against short - circuit faults caused by electrical short - circuits in the switching power supply. Most switching power supplies have the function of short - circuit protection. At the same time, different short - circuit protection methods are set according to different situations. Generally, in the case of an output - terminal short - circuit, the PWM control circuit can limit the output current within a safe range. It can use various methods to implement the current - limiting circuit. When power current - limiting does not work in a short - circuit, only an additional part of the circuit needs to be added for short - circuit protection. However, the existing control methods, device compositions, costs, structures, and performances of short - circuit circuits do not have advantages. The existing technologies mainly have the following characteristics:

[0003] Currently, the commonly used short - circuit protection widely adopts a circuit scheme that uses a controller to limit the current for protection. This short - circuit protection scheme is actually based on the same principle as over - current. This control method also cooperates with the current - limiting resistor of the primary MOSFET to control the maximum output power to achieve short - circuit protection. Traditional short - circuit protection cannot independently control the short - circuit current, especially in the case where a very small short - circuit current needs to be limited; in the short - circuit protection of a switching power supply, it cannot meet the requirement of limiting a relatively small short - circuit current. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a short - circuit protection circuit that can achieve protection under the short - circuit state of a switching power supply, limit the short - circuit current, and meet the requirement of limiting a relatively small short - circuit current.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In the first aspect, a short - circuit protection circuit is provided, which is applied to a switching power supply and includes a switch control module, an operational - amplifier sampling module, and a short - circuit control module;

[0007] The first input terminal and the fourth input terminal of the switch control module are used to be connected to the output terminal of the switching power supply. The second input terminal is connected to the first output terminal of the operational - amplifier sampling module, the third input terminal is connected to the second output terminal of the operational - amplifier sampling module, the first output terminal is respectively connected to the first end of the short - circuit control module and the positive end of the load, and the second output terminal is connected to the first input terminal of the operational - amplifier sampling module;

[0008] The second input terminal of the operational - amplifier sampling module is respectively connected to the second end of the short - circuit control module and the negative end of the load;

[0009] The third terminal of the short - circuit control module is used to connect to the output terminal of the switching power supply;

[0010] The switch control module is used to sample the input voltage of the switching power supply and use the obtained voltage signal as the reference voltage of the operational - amplifier sampling module;

[0011] The short - circuit control module is used to output a first voltage signal to the operational - amplifier sampling module when the load is in a normal state, or to limit the magnitude of the short - circuit current of the load and output a second voltage signal to the operational - amplifier sampling module when the load is in a short - circuit state;

[0012] The operational - amplifier sampling module is used to compare the first voltage signal or the second voltage signal with the reference voltage, and when the first voltage signal is less than the reference voltage, control the switch control module to turn on so that the switching power supply and the load form a path, and when the second voltage signal is greater than the reference voltage, control the switch control module to turn off so that the switching power supply and the load are open - circuited.

[0013] Preferably, the short - circuit control module includes a capacitor C3, a resistor R6, a resistor R7, and a switch Q3; one end of the resistor R6 serves as the first terminal of the short - circuit control module, and the other end is connected to one end of the capacitor C3 and the control terminal of the switch Q3; the other end of the capacitor C3 serves as the third terminal of the short - circuit control module; the first end of the switch Q3 is connected to one end of the resistor R7 and then serves as the second terminal of the short - circuit control module; the second end of the switch Q3 is connected to the other end of the resistor R7 and then grounded.

[0014] Preferably, the resistor R7 is an adjustable resistor.

[0015] Preferably, the switch control module includes: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a switch Q1, and a switch Q2; one end of the resistor R1 is connected to the second end of the switch Q1 and then serves as the first input terminal of the switch control module; the other end of the resistor R1 is connected to one end of the resistor R2 and then serves as the second output terminal of the switch control module; the other end of the resistor R2 is grounded; the first end of the switch Q1 serves as the first output terminal of the switch control module, and the control terminal is connected to the first end of the switch Q2 and one end of the resistor R3; the other end of the resistor R3 serves as the second input terminal of the switch control module; the control terminal of the switch Q2 is connected to one end of the resistor R4; the other end of the resistor R4 is connected to one end of the resistor R5 and then serves as the third input terminal of the switch control module; the other end of the resistor R5 is connected to the second end of the switch Q2 and then serves as the fourth input terminal of the switch control module.

[0016] Preferably, the switch control module further includes a diode D1 and a capacitor C1; one end of a resistor R1 is connected to the output end of the switching power supply through the diode D1. After one end of the resistor R1 is connected to the cathode of the diode and the positive terminal of the capacitor C1, it is connected to the power supply terminal of the operational amplifier sampling module; the negative terminal of the capacitor C1 is grounded.

[0017] Preferably, the operational amplifier sampling module includes: an operational amplifier U1A and an operational amplifier U1B; the inverting input terminal of the operational amplifier U1A and the non-inverting input terminal of the operational amplifier U1B are connected and used as the first input terminal of the operational amplifier sampling module; the non-inverting input terminal of the operational amplifier U1A and the inverting input terminal of the operational amplifier U1B are connected and used as the second input terminal of the operational amplifier sampling module; the output terminal of the operational amplifier U1A is used as the first output terminal of the operational amplifier sampling module; the output terminal of the operational amplifier U1B is used as the second output terminal of the operational amplifier sampling module; the power supply terminals of the operational amplifier U1A and the operational amplifier U1B are used as the power supply terminal of the operational amplifier sampling module.

[0018] In a second aspect, a short-circuit protection circuit is provided, which is applied to a switching power supply and includes a switch control module, an operational amplifier sampling module, and a short-circuit control module;

[0019] The switch control module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a switching transistor Q1, a switching transistor Q2, a diode D1, and a capacitor C1;

[0020] The operational amplifier sampling module includes an operational amplifier U1A and an operational amplifier U1B;

[0021] The short-circuit control module includes a capacitor C3, a resistor R6, a resistor R7, and a switching transistor Q3;

[0022] After the anode of diode D1 is connected to the second terminal of switching transistor Q1, it is used to connect to the output terminal of the switching power supply; the cathode of diode D1 is commonly connected to the positive terminal of capacitor C1, one end of resistor R1, the power supply terminal of operational amplifier U1A, and the power supply terminal of operational amplifier U1B; the other end of resistor R1 is commonly connected to one end of resistor R2, the inverting input terminal of operational amplifier U1A, and the non-inverting input terminal of operational amplifier U1B; the control terminal of switching transistor Q1 is connected to one end of resistor R3 and the first terminal of switching transistor Q2; the other end of resistor R3 is connected to the output terminal of operational amplifier U1A; the control terminal of switching transistor Q2 is connected to one end of resistor R4, and the other end of resistor R4 is connected to one end of resistor R5 and the output terminal of operational amplifier U1B; after the second terminal of switching transistor Q2 is connected to the other end of resistor R5, it is used to connect to the output terminal of the switching power supply; the first terminal of switching transistor Q1 is connected to one end of resistor R6 and then used to connect to the positive terminal of the load; the other end of resistor R6 is connected to one end of capacitor C3 and the control terminal of switching transistor Q3; the other end of resistor C3 is used to connect to the output terminal of the switching power supply; the first terminal of switching transistor Q3 is connected to one end of resistor R7, the non-inverting input terminal of operational amplifier U1A, and the inverting input terminal of operational amplifier U1B; the second terminal of switching transistor Q3, the other end of resistor R7, the other end of resistor R2, and the negative terminal of capacitor C1 are grounded.

[0023] Preferably, both switching transistor Q1 and switching transistor Q2 are PNP type MOS transistors, and switching transistor Q3 is an NPN type MOS transistor.

[0024] Preferably, the first terminals of switching transistor Q1, switching transistor Q2, and switching transistor Q3 are all drain electrodes, the second terminals are all source electrodes, and the control terminals are all gate electrodes.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The short-circuit protection circuit of the present invention can sample the output current of the switching power supply. The short-circuit protection can adjust the short-circuit current, especially can realize the function of limiting a smaller short-circuit current, and can be used in most constant-voltage products;

[0027] 2. The short-circuit protection circuit of the present invention can not only perform short-circuit protection on the switching power supply, can limit a short-circuit current smaller than normal load, and the startup process is not affected;

[0028] 3. The short-circuit protection circuit of the present invention does not use a digital control chip, reducing the complexity of the circuit and the development cost of the switching power supply, and having more advantages in terms of space and cost;

[0029] 4. The short-circuit protection circuit of the present invention can not only protect the customer application load terminal during short-circuit protection, but also protect the switching power supply terminal, and will not cause stress damage and thermal damage to components. Description of the Drawings

[0030] Figure 1 It is the schematic diagram of the application of the short - circuit protection circuit in the first embodiment of the present invention in a switching power supply;

[0031] Figure 2 It is the framework diagram of the application of the short - circuit protection circuit in the first embodiment of the present invention in a switching power supply. Detailed implementation manners

[0032] To make the technical solution of the present invention clearer, the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are partial embodiments of the present invention. Those of ordinary skill in the art can make various other forms of modifications, substitutions, or changes to the present invention without creative efforts, and still fall within the protection scope of the present invention.

[0033] Refer to Figure 1 and Figure 2 , Figure 1 is the application block diagram of the short - circuit protection circuit in this embodiment, Figure 2 is the schematic diagram of the application of the short - circuit protection circuit in the first embodiment of the present invention in a switching power supply. In this embodiment, a short - circuit protection circuit is provided, which is applied to a switching power supply and includes a switch control module 11, an operational amplifier sampling module 12, and a short - circuit control module 13;

[0034] The first input terminal and the fourth input terminal of the switch control module 11 are used to be connected to the output terminal of the switching power supply. The second input terminal is connected to the first output terminal of the operational amplifier sampling module 12, the third input terminal is connected to the second output terminal of the operational amplifier sampling module 12, the first output terminal is respectively connected to the first end of the short - circuit control module 13 and the positive end of the load, and the second output terminal is connected to the first input terminal of the operational amplifier sampling module 12;

[0035] The second input terminal of the operational amplifier sampling module 12 is respectively connected to the second end of the short - circuit control module 13 and the negative end of the load;

[0036] The third end of the short - circuit control module 13 is used to be connected to the output terminal of the switching power supply;

[0037] The switch control module 11 is used to sample the input voltage of the switching power supply and use the obtained voltage signal as the reference voltage of the operational amplifier sampling module 12;

[0038] The short - circuit control module 13 is used to output a first voltage signal to the operational amplifier sampling module 12 when the load is in a normal state, or to limit the magnitude of the short - circuit current of the load and output a second voltage signal to the operational amplifier sampling module 12 when the load is in a short - circuit state;

[0039] The operational amplifier sampling module 12 is used to compare the first voltage signal or the second voltage signal with the reference voltage. When the first voltage signal is less than the reference voltage, it controls the switch control module 11 to turn on, so that the switching power supply and the load form a path. When the second voltage signal is greater than the reference voltage, it controls the switch control module 11 to turn off, so that the switching power supply and the load are open-circuited.

[0040] As a specific embodiment of the short-circuit control module 13, the short-circuit control module 13 includes a capacitor C3, a resistor R6, a resistor R7, and a switching transistor Q3. One end of the resistor R6 serves as the first end of the short-circuit control module 13, and the other end is connected to one end of the capacitor C3 and the control end of the switching transistor Q3. The other end of the capacitor C3 serves as the third end of the short-circuit control module 13. The first end of the switching transistor Q3 is connected to one end of the resistor R7 and then serves as the second end of the short-circuit control module 13. The second end of the switching transistor Q3 is connected to the other end of the resistor R7 and then grounded.

[0041] Specifically, the resistor R7 is an adjustable resistor. The resistor R7 is a sampling resistor, which is used to sample the short-circuit signal during output short-circuit, can limit the magnitude of the short-circuit current, and set different resistance values as different sampling signals.

[0042] As a specific embodiment of the switch control module 11

[0043] The switch control module 11 includes: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a switching transistor Q1, and a switching transistor Q2. One end of the resistor R1 is connected to the second end of the switching transistor Q1 and then serves as the first input end of the switch control module 11. The other end of the resistor R1 is connected to one end of the resistor R2 and then serves as the second output end of the switch control module 11. The other end of the resistor R2 is grounded. The first end of the switching transistor Q1 serves as the first output end of the switch control module 11, and the control end is connected to the first end of the switching transistor Q2 and one end of the resistor R3. The other end of the resistor R3 serves as the second input end of the switch control module 11. The control end of the switching transistor Q2 is connected to one end of the resistor R4. After the other end of the resistor R4 is connected to one end of the resistor R5, it serves as the third input end of the switch control module 11. After the other end of the resistor R5 is connected to the second end of the switching transistor Q2, it serves as the fourth input end of the switch control module 11.

[0044] In order to reduce the complexity and volume of the circuit, the switch control module 11 further includes a diode D1 and a capacitor C1. One end of the resistor R1 is connected to the output end of the switching power supply through the diode D1. After one end of the resistor R1 is connected to the cathode of the diode and the positive end of the capacitor C1, it is connected to the power supply terminal of the operational amplifier sampling module 12. The negative end of the capacitor C1 is grounded. The capacitor C1 is a power supply capacitor, which provides a power supply voltage VGG for the normal operation of the operational amplifier U1A and the operational amplifier U1B.

[0045] As a specific implementation of the operational amplifier sampling module 12, the operational amplifier sampling module 12 includes: operational amplifiers U1A and U1B; the inverting input terminal of operational amplifier U1A is connected to the non-inverting input terminal of operational amplifier U1B and serves as the first input terminal of the operational amplifier sampling module 12; the non-inverting input terminal of operational amplifier U1A is connected to the inverting input terminal of operational amplifier U1B and serves as the second input terminal of the operational amplifier sampling module 12; the output terminal of operational amplifier U1A serves as the first output terminal of the operational amplifier sampling module 12; the output terminal of operational amplifier U1B serves as the second output terminal of the operational amplifier sampling module 12; the power supply terminals of operational amplifiers U1A and U1B serve as the power supply terminal of the operational amplifier sampling module 12.

[0046] Specifically, after the anode of diode D1 is connected to the second terminal of switch Q1, it is used to connect to the output terminal of the switching power supply; the cathode of diode D1 is commonly connected to the positive terminal of capacitor C1, one end of resistor R1, the power supply terminal of operational amplifier U1A, and the power supply terminal of operational amplifier U1B; the other end of resistor R1 is commonly connected to one end of resistor R2, the inverting input terminal of operational amplifier U1A, and the non-inverting input terminal of operational amplifier U1B; the control terminal of switch Q1 is connected to one end of resistor R3 and the first terminal of switch Q2; the other end of resistor R3 is connected to the output terminal of operational amplifier U1A; the control terminal of switch Q2 is connected to one end of resistor R4, and the other end of resistor R4 is connected to one end of resistor R5 and the output terminal of operational amplifier U1B; the second terminal of switch Q2 is connected to the other end of resistor R5 and is used to connect to the output terminal of the switching power supply; the first terminal of switch Q1 is connected to one end of resistor R6 and is used to connect to the positive terminal of the load; the other end of resistor R6 is connected to one end of capacitor C3 and the control terminal of switch Q3; the other end of resistor C3 is used to connect to the output terminal of the switching power supply; the first terminal of switch Q3 is connected to one end of resistor R7, the non-inverting input terminal of operational amplifier U1A, and the inverting input terminal of operational amplifier U1B; the second terminal of switch Q3, the other end of resistor R7, the other end of resistor R2, and the negative terminal of capacitor C1 are grounded. Switch Q1 and switch Q2 are both PNP-type MOS transistors, and switch Q3 is an NPN-type MOS transistor; the first terminals of switch Q1, switch Q2, and switch Q3 are all drain electrodes, the second terminals are all source electrodes, and the control terminals are all gate electrodes.

[0047] Specifically, the switching transistor Q1 of the switch control module 11 is the main control device for short - circuiting the entire module, controlling normal output or output shutdown; the source of the switching transistor Q1 is connected to VIN +, the input terminal of this module's circuit. The input terminal VIN + is the positive output terminal of the switching power supply, and the input terminal GND is the negative output terminal of the switching power supply; the drain of the switching transistor Q1 is connected to VO + as the output terminal of this module's circuit, which is used to connect to the positive terminal of the load; the resistor R3 is a driving resistor, used to output high and low levels to drive the switching transistor Q1, and the driving level is provided by the output terminal PIN1 of the operational amplifier U1A. The gate of the switching transistor Q1 is simultaneously connected to the drain of the switching transistor Q2. The resistor R4 is a driving resistor, used to output high and low levels to drive the switching transistor Q2, and the driving level is provided by the output terminal PIN7 of the operational amplifier U1B. The resistor R5 is a pull - up resistor at the output terminal of the operational amplifier U1B, connected to the input terminal VIN + (i.e., the positive output terminal of the switching power supply), enabling the operational amplifier U1B to output a high level after comparison; the source of the switching transistor Q2 is connected to the input terminal VIN + to provide a high level.

[0048] The switch control module 11 maintains normal output by directly driving the conduction of the switching transistor Q1; or it turns off the output by driving the switching transistor Q1 to turn off through the conduction of the switching transistor Q2, thus achieving the function of short - circuit protection.

[0049] The operational amplifier sampling module 12 mainly samples, compares, and outputs driving levels for the dual operational amplifiers U1A and U1B; the supply voltage VGG is divided by the resistors R1 and R2 to obtain a voltage signal REF, which serves as the reference level for the inverting input terminal of the operational amplifier U1A and simultaneously as the reference level for the non - inverting input terminal of U1B.

[0050] The supply terminals of the operational amplifier U1A and the operational amplifier U1B are connected to the supply voltage VGG, the ground terminal PIN4 of the operational amplifier U1A and U1B is connected to GND. The non - inverting input terminal of the operational amplifier U1A is connected to the negative output terminal VO - of this module's circuit, used to input the first voltage signal or the second voltage signal sampled from the negative output terminal of the short - circuit protection circuit. The first voltage signal or the second voltage signal is compared with the reference voltage, and the output terminal of the operational amplifier U1A outputs a level to drive the PMOS transistor Q1 of the switch control module 11; the inverting input terminal of the operational amplifier U1B is connected to the negative output terminal VO -, used to input the first voltage signal or the second voltage signal sampled from the negative output terminal of the short - circuit protection circuit. The first voltage signal or the second voltage signal is compared with the reference voltage, and the output terminal of the operational amplifier U1B outputs a level to drive the PMOS transistor Q2 of the switch control module 11.

[0051] The switching transistor Q3 of the short - circuit control module 13 controls the conduction path during the starting process at a relatively small short - circuit current, so that the short - circuit protection function of the sampling signal will not be accidentally triggered during the current - rising process at startup; the capacitor C3 provides the driving voltage from the input terminal VIN+ of this module. By charging the capacitor C3 first, a certain voltage is provided to drive the switching transistor Q3; the resistor R6 provides a zero - level to turn off Q3 in the short - circuit state. When the load is in a short - circuit state, the current enters from the negative terminal of the load to the resistor R7, which can play the role of short - circuit protection and limiting the short - circuit current.

[0052] This embodiment is proposed for the protection function and limiting short - circuit current under short - circuit conditions. The working principle of this embodiment is analyzed as follows:

[0053] The second voltage signal V1 has the following formula:

[0054] V1 = Io * R7, where Io is the output current and R7 is the sampling resistor of the output current.

[0055] The conduction condition of the switching transistor Q1 is that the VGS (gate - source voltage) is negative, that is, the VS (source voltage) is higher than the VG (gate voltage), and the VSD (source - gate voltage) conducts forward.

[0056] When the switching power supply is in a normal working state, the voltage at the non - inverting input terminal of the operational amplifier U1A is less than the voltage at the inverting input terminal. The output level of the operational amplifier U1A is low. A low level is output to the gate of the switching transistor Q1 through the resistor R3. The source of the switching transistor Q1 is connected to the input terminal VIN+ and is always at a high level. At this time, the level of the source of the switching transistor Q1 is higher than the level of the gate, the VGS (gate - source voltage) is negative, and the switching transistor Q1 conducts. Similarly, the voltage at the inverting input terminal of the operational amplifier U1B is less than the voltage at the non - inverting input terminal. The output level of the operational amplifier U1B is high. A high level is output to the gate of the switching transistor Q2 through the resistor R4. At this time, the gate and source of the switching transistor Q2 are both at a high level and cannot reach the conduction voltage, so the switching transistor Q2 is in a cut - off state and does not conduct; the input terminal VIN+ is output to the output terminal VO+ of the short - circuit protection circuit through the conduction of the switching transistor Q1, the switching power supply outputs normally, and the switching power supply does not enter the protection state.

[0057] When the load at the customer's backend shows an abnormal short - circuit state, the potential difference across resistor R6 is 0, providing a zero - level to cut off switch Q3. The output current Io flows from the positive output terminal VO+ to the negative output terminal VO-, then to resistor R7. After sampling, the second voltage signal V1 is output and compared with the reference voltage at the operational amplifier terminal REF. The voltage at the non - inverting input terminal of operational amplifier U1A is greater than the voltage at the inverting input terminal. The output level of operational amplifier U1A is high, and a high level is output to the gate of switch Q1 through resistor R3. The voltage at the inverting input terminal of operational amplifier U1B is greater than the voltage at the non - inverting input terminal. The output level of operational amplifier U1B is low, and a low level is output to the gate of switch Q2 through resistor R4. The source of switch Q2 is connected to the input terminal VIN+ and is at a high level. The source level of switch Q2 is higher than the gate level, and VGS (gate - source voltage) is negative, so switch Q2 conducts. The voltage at the source of switch Q2 is equal to the voltage at the gate of switch Q1, both being high levels. Switch Q1 cannot meet the conduction condition, so switch Q1 is cut off at this time, the output is turned off, realizing the function of short - circuit protection, and the limited short - circuit current is the sampling current.

[0058] The above is only used to illustrate the technical solution of the present application rather than to limit it. Although the present invention has been described in detail according to the embodiments, those of ordinary skill in the art can modify or replace the specific implementation manners of the present invention. Any modification or replacement that does not depart from the spirit and scope of the present invention is within the protection scope of the claims of the present invention.

Claims

1. A short-circuit protection circuit, applied to a switching power supply, characterized in that It includes a switch control module, an operational amplifier sampling module, and a short - circuit control module; The first input terminal and the fourth input terminal of the switch control module are used to connect to the output terminal of the switching power supply. The second input terminal is connected to the first output terminal of the operational amplifier sampling module, the third input terminal is connected to the second output terminal of the operational amplifier sampling module, the first output terminal is respectively connected to the first end of the short - circuit control module and the positive end of the load, and the second output terminal is connected to the first input terminal of the operational amplifier sampling module; The second input terminal of the operational amplifier sampling module is respectively connected to the second end of the short - circuit control module and the negative end of the load; The third end of the short - circuit control module is used to connect to the output terminal of the switching power supply; The switch control module is used to sample the input voltage of the switching power supply and use the obtained voltage signal as the reference voltage of the operational amplifier sampling module; The short - circuit control module is used to output a first voltage signal to the operational amplifier sampling module when the load is in a normal state, or to limit the magnitude of the short - circuit current of the load and output a second voltage signal to the operational amplifier sampling module when the load is in a short - circuit state; The operational amplifier sampling module is used to compare the first voltage signal or the second voltage signal with the reference voltage, and when the first voltage signal is less than the reference voltage, control the switch control module to conduct, so that the switching power supply and the load form a path, and when the second voltage signal is greater than the reference voltage, control the switch control module to turn off, so that the switching power supply and the load are open - circuited; The switch control module includes: resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, switch tube Q1, and switch tube Q2; One end of resistor R1 is connected to the second end of switch tube Q1 and serves as the first input terminal of the switch control module; The other end of resistor R1 is connected to one end of resistor R2 and serves as the second output terminal of the switch control module; The other end of resistor R2 is grounded; The first end of switch tube Q1 serves as the first output terminal of the switch control module, and the control end is connected to the first end of switch tube Q2 and one end of resistor R3; The other end of resistor R3 serves as the second input terminal of the switch control module; The control end of switch tube Q2 is connected to one end of resistor R4; After the other end of resistor R4 is connected to one end of resistor R5, it serves as the third input terminal of the switch control module; After the other end of resistor R5 is connected to the second end of switch tube Q2, it serves as the fourth input terminal of the switch control module.

2. The short-circuit protection circuit according to claim 1, wherein The short - circuit control module includes capacitor C3, resistor R6, resistor R7, and switch tube Q3; One end of resistor R6 serves as the first end of the short - circuit control module, and the other end is connected to one end of capacitor C3 and the control end of switch tube Q3; The other end of capacitor C3 serves as the third end of the short - circuit control module; The first end of switch tube Q3 is connected to one end of resistor R7 and serves as the second end of the short - circuit control module; The second end of switch tube Q3 is connected to the other end of resistor R7 and grounded.

3. The short-circuit protection circuit according to claim 2, wherein, Resistor R7 is an adjustable resistor.

4. The short-circuit protection circuit according to claim 1, wherein The switch control module further includes a diode D1 and a capacitor C1; one end of a resistor R1 is connected to the output terminal of a switching power supply through the diode D1. After one end of the resistor R1 is connected to the cathode of the diode and the positive terminal of the capacitor C1, it is connected to the power supply terminal of the operational amplifier sampling module; the negative terminal of the capacitor C1 is grounded.

5. The short-circuit protection circuit according to claim 4, wherein The operational amplifier sampling module includes: an operational amplifier U1A and an operational amplifier U1B; the inverting input terminal of the operational amplifier U1A and the non-inverting input terminal of the operational amplifier U1B are connected and used as the first input terminal of the operational amplifier sampling module; the non-inverting input terminal of the operational amplifier U1A and the inverting input terminal of the operational amplifier U1B are connected and used as the second input terminal of the operational amplifier sampling module; the output terminal of the operational amplifier U1A is used as the first output terminal of the operational amplifier sampling module; the output terminal of the operational amplifier U1B is used as the second output terminal of the operational amplifier sampling module; the power supply terminals of the operational amplifier U1A and the operational amplifier U1B are used as the power supply terminal of the operational amplifier sampling module.

6. A short-circuit protection circuit is applied to a switching power supply, characterized in that, It includes a switch control module, an operational amplifier sampling module and a short-circuit control module; The switch control module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a switching transistor Q1, a switching transistor Q2, a diode D1 and a capacitor C1; The operational amplifier sampling module includes an operational amplifier U1A and an operational amplifier U1B; The short-circuit control module includes a capacitor C3, a resistor R6, a resistor R7 and a switching transistor Q3; The anode of the diode D1 is connected to the second terminal of the switching transistor Q1 and then used to be connected to the output terminal of the switching power supply; the cathode of the diode D1 is commonly connected to the positive terminal of the capacitor C1, one end of the resistor R1, the power supply terminal of the operational amplifier U1A and the power supply terminal of the operational amplifier U1B; the other end of the resistor R1 is commonly connected to one end of the resistor R2, the inverting input terminal of the operational amplifier U1A and the non-inverting input terminal of the operational amplifier U1B; the control terminal of the switching transistor Q1 is connected to one end of the resistor R3 and the first terminal of the switching transistor Q2; the other end of the resistor R3 is connected to the output terminal of the operational amplifier U1A; the control terminal of the switching transistor Q2 is connected to one end of the resistor R4, and the other end of the resistor R4 is connected to one end of the resistor R5 and the output terminal of the operational amplifier U1B; the second terminal of the switching transistor Q2 is connected to the other end of the resistor R5 and then used to be connected to the output terminal of the switching power supply; the first terminal of the switching transistor Q1 is connected to one end of the resistor R6 and then used to be connected to the positive terminal of the load; the other end of the resistor R6 is connected to one end of the capacitor C3 and the control terminal of the switching transistor Q3; the other end of the resistor C3 is used to be connected to the output terminal of the switching power supply; the first terminal of the switching transistor Q3 is connected to one end of the resistor R7, the non-inverting input terminal of the operational amplifier U1A and the inverting input terminal of the operational amplifier U1B; the second terminal of the switching transistor Q3, the other end of the resistor R7, the other end of the resistor R2 and the negative terminal of the capacitor C1 are grounded.

7. The short-circuit protection circuit according to claim 6, characterized in that, The switching transistors Q1 and Q2 are both PNP type MOS transistors, and the switching transistor Q3 is an NPN type MOS transistor.

8. The short-circuit protection circuit according to claim 7, wherein, The first terminals of the switching transistors Q1, Q2 and Q3 are all drain electrodes, the second terminals are all source electrodes, and the control terminals are all gate electrodes.

Citation Information

Patent Citations

  • Short-circuit protection circuit

    CN209805407U

  • Short circuit automatic protection circuit and system

    CN216625279U