Power supply control circuit with over-current protection self-locking and detection functions

Abstract

The utility model provides a power supply control circuit with over-current protection self-locking and detection functions, which is used for solving the technical problems of poor over-current or short-circuit protection reliability and high cost in the existing power supply output circuit. The circuit comprises an output control circuit, an over-current detection circuit and a self-locking control circuit, the input end of the over-current detection circuit is connected with a power supply input port, the output end of the over-current detection circuit is connected with the output control circuit, the output control circuit is connected with a power supply output port, and the self-locking control circuit is connected with the power supply output port. The self-locking control circuit is respectively connected with the power supply output port and the output control circuit, the self-locking control circuit is connected with the on-off control and state detection port, and the on-off control and state detection port is connected with an external circuit. According to the utility model, the functions of power supply output control, output state detection and automatic over-current protection are realized at the same time, the action time is extremely short, the on-off performance is ideal, the protection action is accurate, the reliability is relatively high, and the cost is relatively low.

Description

Technical Field

[0001] This utility model relates to the technical field of power supply control, and in particular to a power supply control circuit with overcurrent protection self-locking and detection functions. Background Technology

[0002] In most circuits with power output functions, it is generally required that while providing power and control, they also have overcurrent or short-circuit protection functions to prevent uncontrollable damage or even more serious accidents such as fires in the event of an accident. Inappropriate protection function design may also affect the normal power output. Therefore, it is very important to have reliable, accurate and stable overcurrent or short-circuit protection functions.

[0003] In existing technologies, the solutions to the above problems typically involve using fuses, resettable PTC fuses, and electronic current limiters. Fuses generally have slow response times and must be replaced once activated, resulting in high maintenance costs. Resettable fuses have relatively high internal resistance, slow response times, and unsatisfactory switching characteristics, making them suitable only for applications with low requirements. Simple electronic current limiters offer fast response times, but generate significant power consumption and heat after activation, leading to poor reliability. Achieving a more ideal protection effect requires a relatively complex design and incurs higher costs.

[0004] Utility model patent application number 202021053460.8 discloses an overcurrent protection circuit, including a power input unit and a load unit. The power input unit forms a power supply loop with the load unit to supply power to the load unit. The overcurrent protection circuit also includes a switch protection unit, a current detection unit, and a self-locking control unit. The current detection unit detects the current of the load unit and outputs a detection signal to the self-locking control unit based on the detection result. The self-locking control unit determines whether an overcurrent has occurred in the load unit based on the detection signal and controls the switch protection unit to turn on or off the power supply loop of the load unit based on the determination result. The self-locking control unit is also used to adjust the overcurrent response range of the load unit. Thus, while realizing the overcurrent protection function of the circuit, it has the characteristics of fast response, wide overcurrent range, and low loss. However, the above patent cannot actively control the working state of the protection circuit, nor can it detect the protection circuit; at the same time, the main control MOS of the circuit is located on the low side of the power supply, resulting in poor versatility, a relatively complex circuit structure, and high cost. Utility Model Content

[0005] To address the technical problems of poor reliability and high cost of overcurrent or short-circuit protection in existing power supply output circuits, this utility model proposes a power supply control circuit with overcurrent protection self-locking and detection functions. In addition to realizing common power supply output control, it can also automatically and quickly cut off the power supply output after a short circuit or overcurrent, and provide signals for different operating states. It can maintain self-locking during normal operation and protection shutdown without external intervention. It effectively integrates the commonly used functions required for external power supply, avoids most of the problems of other protection schemes, and has a simple structure, maintaining a relatively low cost.

[0006] To achieve the above objectives, the technical solution of this utility model is as follows: a power supply control circuit with overcurrent protection, self-locking, and detection functions, characterized in that it includes an output control circuit, an overcurrent detection circuit, and a self-locking control circuit. The input terminal of the overcurrent detection circuit is connected to the power supply input port, the output terminal of the overcurrent detection circuit is connected to the output control circuit, the output control circuit is connected to the power supply output port, the self-locking control circuit is connected to both the power supply output port and the output control circuit, the self-locking control circuit is connected to the on / off control and status detection port, and the on / off control and status detection port is connected to an external circuit.

[0007] Preferably, the on / off control and status detection port is a bidirectional port for control signal injection and detection signal output.

[0008] Preferably, the overcurrent detection circuit includes a transistor Q2 and a resistor R0. The emitter of the transistor Q2 is connected to the power supply input port, and the base and collector of the transistor Q2 are both connected to the output control circuit. The base of the transistor Q2 is connected to the emitter through the resistor R0.

[0009] Preferably, the resistor R0 is a self-resetting fuse PTC.

[0010] Preferably, the output control circuit includes a switch Q1, a resistor R1, and a resistor R2. The drain of the switch Q1 is connected to the power supply output port, and the gate of the switch Q1 is connected to the source of the switch Q1 through the resistor R1. The gate of the switch Q1 and one end of the resistor R1 are both connected to the base of the transistor Q2. The collector of the transistor Q2 is connected to the other end of the resistor R1. The other end of the resistor R1 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the self-locking control circuit.

[0011] Preferably, the switching transistor is a MOSFET or a PNP transistor.

[0012] Preferably, the MOSFET is a P-channel MOSFET for power output control.

[0013] Preferably, the self-locking control circuit includes a transistor Q3, a resistor R3, and a resistor R4. The collector of transistor Q3 is connected to the other end of resistor R2 in the output control circuit. The emitter of transistor Q3 is grounded through a reference voltage source. The base of transistor Q3 is connected to one end of resistor R3 and one end of resistor R4. The other end of resistor R3 is connected to the power supply output port and the drain of switching transistor Q1. The other end of resistor R4 is grounded.

[0014] Preferably, the reference voltage source is obtained by voltage division of the power supply, or the reference voltage source is provided by a Zener diode or a reference source; the power supply input port is connected to the positive terminal of the power supply, and the negative terminal of the power supply is grounded; the power supply output port is connected to the load.

[0015] Preferably, the current value corresponding to the overcurrent protection action is the on-state voltage of transistor Q2 divided by the resistance value of resistor R0.

[0016] When the input voltage Vin at the power supply input port is powered on and reaches the normal operating voltage, the output voltage Vout at the power supply output port and the terminal voltage Vctrl at the on / off control and status detection port are both 0V because the switch Q1 in the output control circuit is turned off. The base and emitter of the transistor Q3 in the self-locking control circuit are reverse biased and remain off. No current flows through the control resistors R1 and R2, and the switch Q1 has no driving voltage and remains off. No current flows through the resistor R0, and the transistor Q2 remains off, resulting in an output voltage Vout = 0. No current flows through the resistors R3 and R4, and the voltage across the resistor R4 is 0, maintaining the off state of the transistor Q3. The circuit remains off and self-locked. The terminal voltage Vctrl = 0 indicates that the circuit is in the output power-off self-locking state.

[0017] If an external circuit injects a high voltage into the on / off control and status detection port as an on-state control signal, when the on-state control signal makes the terminal voltage Vctrl greater than the sum of the BE turn-on voltage of transistor Q3 and the voltage Vref of the reference voltage source, transistor Q3 turns on, and current flows through resistors R1 and R2. The resistance values ​​of resistors R1 and R2 are set so that the voltage across resistor R1 is greater than the threshold voltage Vth when transistor Q3 turns on. Therefore, switching transistor Q1 turns on, and at this time, the output voltage Vout of the power supply output port is equal to the input voltage Vin. Set the resistance values ​​of resistors R3 and R4 so that the voltage across resistor R4 is greater than the sum of the BE turn-on voltage of transistor Q3 and the voltage Vref of the reference voltage source when switch Q1 is turned on. The condition that switch Q1 is turned on maintains the turn-on condition of transistor Q3. Even if the externally injected turn-on control signal is removed, it will still remain in the output turn-on state. Transistors Q1 and Q3 remain turned on and latched up. The terminal voltage Vctrl is equal to the sum of the BE turn-on voltage of transistor Q3 and the voltage Vref of the reference voltage source. The external indicator circuit is in the output power supply latched up state.

[0018] When the output needs to be actively shut down, the external circuit injects a low voltage into the on / off control and status detection port as a shutdown control signal. When the shutdown control signal makes the terminal voltage Vctrl less than the voltage Vref, the transistor Q3 turns off. Even if the shutdown control signal is removed, the shutdown of transistor Q3 will cause the switch Q1 to turn off, and the shutdown of switch Q1 will maintain the shutdown of transistor Q3, thus changing from the on-locked state to the off-locked state.

[0019] When an overcurrent or short circuit occurs, the current generates a voltage across resistor R0. When this voltage reaches the turn-on voltage of transistor Q2, transistor Q2 turns on. The turn-on current drives the gate voltage of switching transistor Q1 to rise, thereby limiting the output current of switching transistor Q1. This causes the output voltage Vout and the terminal voltage Vctrl to decrease. When the terminal voltage Vctrl drops below the voltage Vref, transistor Q3 turns off, and subsequently switching transistor Q1 turns off, switching from the turn-on self-locking state to the turn-off self-locking state. The output is cut off, achieving output short-circuit or overcurrent protection. The terminal voltage Vctrl changes from high voltage to low voltage.

[0020] Compared with existing technologies, the beneficial effects of this utility model are as follows: It mainly includes an output control circuit, an overcurrent detection circuit, and a self-locking control circuit, with four external connection ports: a power supply input port, a power supply output port, a common ground port, and a switch-on / off control and status detection port. This utility model can actively set the circuit to the corresponding self-locking state by injecting different voltages into the switch-on / off control and status detection port, and then perform status detection on the circuit through the switch-on / off control and status detection port. When an overcurrent or short circuit occurs, this utility model can automatically cut off the output and maintain it in the cut-off state; simultaneously, the switch-on / off control and status detection port will also output a corresponding status signal for subsequent processing by other supporting circuits. This utility model simultaneously realizes power supply output control, output status detection, and automatic overcurrent protection functions, achieving extremely short operating time, ideal switching performance, accurate protection action, and high reliability, while also maintaining low cost. When used in conjunction with other external circuits to form a complete product, it does not occupy excessive port, computing power, or time resources, yet achieves ideal protection and control effects. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1This is a schematic diagram of the circuit structure of this utility model.

[0023] In the diagram, 1 is the output control circuit, 2 is the overcurrent detection circuit, and 3 is the self-locking control circuit. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] like Figure 1 As shown, a power supply control circuit with overcurrent protection, self-locking, and detection functions includes an output control circuit 1, an overcurrent detection circuit 2, and a self-locking control circuit 3. The power supply input port Pin is connected to the overcurrent detection circuit 2, which is also connected to a power source. The overcurrent detection circuit 2 is used to implement the overcurrent detection function. The overcurrent detection circuit 2 is connected to the output control circuit 1, which is connected to the self-locking control circuit 3. The output control circuit 1 has a power supply output port Pout, which is connected to the load. The self-locking control circuit 3 is connected in parallel across the load. The self-locking control circuit 3 is connected to an on / off control and status detection port, which is connected to an external circuit. The external circuit provides on / off control signals to actively change the circuit's operating state, such as restarting the power supply after power-on or overcurrent protection, or actively shutting down the output. The external circuit can also detect the output power supply status and perform corresponding subsequent processing, such as re-controlling power-on after a delay, indicating abnormalities in indicator lights or display screens. Output control circuit 1 is used to implement power supply output control function, and self-locking control circuit 3 is used to implement state self-locking and state signal output function. The output control circuit 1, overcurrent detection circuit 2 and self-locking control circuit 3 work together to simultaneously realize power-on / off state self-locking, active control output, overcurrent automatic power-off protection and holding, and power-on / off state signal output.

[0026] The overcurrent detection circuit 2 includes a transistor Q2 and a resistor R0. The emitter of transistor Q2 is connected to the power supply input port Pin, and both the base and collector of transistor Q2 are connected to the output control circuit 1. The base of transistor Q2 is connected to the emitter through resistor R0. Transistor Q2 is an overcurrent detection transistor. Resistor R0 is a current sampling resistor, using a resettable PTC fuse, but it can also be replaced with a general-purpose resistor. The overcurrent detection circuit 2 uses a resettable PTC fuse as the sampling resistor to improve protection reliability, operational accuracy, and temperature stability. The use of a general-purpose resistor is also supported.

[0027] Output control circuit 1 includes a MOSFET Q1, resistors R1 and R2. The drain of MOSFET Q1 is connected to the power output port Pout. The gate of MOSFET Q1 is connected to the source of MOSFET Q1 through resistor R1. The gate of MOSFET Q1 and one end of resistor R1 are both connected to the base of transistor Q2. The collector of transistor Q2 is connected to the other end of resistor R1. The other end of resistor R1 is connected to one end of resistor R2, and the other end of resistor R2 is connected to the self-locking control circuit 3. MOSFET Q1 is a P-channel MOSFET for power output control, and can also be replaced with a PNP transistor. Resistors R1 and R2 are the drive resistors for MOSFET Q1. MOSFET Q1 acts as a power on / off control switch, and resistors R1 and R2 are the voltage divider resistors for driving MOSFET Q1. Output control circuit 1 can be replaced with a transistor without affecting the normal operation of the circuit, which is beneficial for low-cost applications.

[0028] The self-locking control circuit 3 includes a transistor Q3, resistors R3 and R4. The collector of transistor Q3 is connected to the other end of resistor R2, and the emitter of transistor Q3 is grounded through a reference voltage source Ref. The base of transistor Q3 is connected to one end of resistor R3 and one end of resistor R4. The other end of resistor R3 is connected to the power supply output port Pout and the drain of MOSFET Q1, and the other end of resistor R4 is grounded. The base of transistor Q3 is connected to the on / off control and status detection port Ctrl, which is connected to the control detector. Transistor Q3 is a status self-locking control transistor. Resistors R3 and R4 are the driving voltage divider resistors for transistor Q3 and also the output voltage divider resistors for the detection signal. Ref is a reference voltage source, which can be obtained by voltage division from the power supply or provided by a Zener diode or a reference source. Transistor Q3, resistors R3 and R4, and the reference voltage source Ref constitute the self-locking control circuit. Pin is the power input port, Pout is the power output port, and Ctrl is the on / off control and status detection port, a bidirectional port for both control signal injection and detection signal output. The active control output function and the on / off status signal output function are implemented by multiplexing the on / off control and status detection port on the same port, saving port resources.

[0029] This invention controls power supply output or shutdown by driving MOSFET Q1 to turn on and off. Transistor Q2 detects and limits the output current through resistor R0. Transistor Q3 and transistor Q1 achieve state latching. These components work together to first limit the output current when it is too high, and then quickly and completely shut down the output when the output voltage drops to the latching off point. Simultaneously, the on / off control and state detection port Ctrl outputs a corresponding voltage to indicate the current state. The following is a detailed explanation of this process:

[0030] The power supply input port Pin is set to input voltage Vin, the reference voltage source Ref to Vref, and the power supply output port Pout to output voltage Vout. The on / off control and status detection port Ctrl has a terminal voltage of Vctrl. For simplified analysis, the on-resistance of MOSFET Q1, transistor Q2, and transistor Q3 is preset to 0, and the off-resistance to infinite. The turn-on threshold voltage of MOSFET Q1 is Vth. The turn-on voltages (BE) of transistors Q2 and Q3 are both Vbe. The initial state of MOSFET Q1, transistor Q2, and transistor Q3 is off.

[0031] When the input voltage Vin is powered on and reaches the normal operating voltage, the output voltage Vout and the terminal voltage Vctrl are 0V because MOSFET Q1 is turned off. Therefore, the base-emitter junction of transistor Q3 remains reverse-biased and off. No current flows through resistors R1 and R2, and MOSFET Q1 remains off due to the lack of a driving voltage. No current flows through resistor R0, resulting in a voltage drop of 0, thus transistor Q2 remains off. At this time, Vout = 0, no current flows through resistors R3 and R4, and the voltage across resistor R4 is 0, maintaining the off state of transistor Q3. The circuit remains in a self-locking off state. Vctrl = 0 indicates that the circuit is in an output power-off self-locking state.

[0032] If an external circuit injects a high voltage into the on / off control and status detection port Ctrl as an on / off control signal, transistor Q3 will turn on when this control signal makes Vctrl > Vbe + Vref. Current will flow through resistors R1 and R2. Resistors R1 and R2 should be set to appropriate values ​​so that the voltage across resistor R1 is greater than the threshold voltage Vth when transistor Q3 is on. The calculation method is R1 / (R1+R2)*(Vin-Vref) > Vth. Therefore, MOSFET Q1 will turn on, and the output voltage Vout = Vin at the power supply output port. Resistors R3 and R4 should be set to appropriate values ​​so that the voltage across resistor R4 is greater than Vbe + Vref when MOSFET Q1 is on. The calculation method is R4 / (R3+R4)*Vout > Vref + Vbe. Therefore, the conduction of MOSFET Q1 maintains the condition for transistor Q3 to conduct. Even if the externally injected turn-on control signal is removed, the circuit will still remain in the output turn-on state, and transistors Q1 and Q3 will remain conducting and latched. At this time, Vctrl = Vref + Vbe indicates that this circuit is in the output power supply latch-up state.

[0033] When active shutdown of the output is required, the external circuit injects a low voltage into the on-off control and status detection port Ctrl as the shutdown control signal. When this shutdown control signal causes the terminal voltage Vctrl < Vref, the triode Q3 turns off. After that, even if the shutdown control signal is removed, since the turn-off of the triode Q3 will lead to the turn-off of the MOS transistor Q1, and the turn-off of the MOS transistor Q1 will maintain the turn-off of the triode Q3, this circuit will change from the on self-locking state to the off self-locking state. The utility model limits the driving voltage through the triode, resulting in insufficient drive of the switching transistor, causing the output voltage to drop and unlock.

[0034] From the above analysis, when the external circuit needs to actively intervene in the control, by injecting a high voltage or a low voltage into the on-off control and status detection port Ctrl, this circuit can be set in the on or off state respectively. After removing the injected control voltage signal, this circuit will still be self-locked and maintain this state. Then the external circuit can convert the port for outputting the control voltage signal into a high-impedance input port, and by continuously detecting the voltage value presented by the terminal voltage Vctrl through this port, the working state of this circuit can be known.

[0035] When overcurrent or short circuit occurs, the current will generate a voltage on the resistor R0. When it reaches the conduction voltage Vbe of the triode Q2, the triode Q2 conducts, and its conduction current will drive the gate voltage of the MOS transistor Q1 to rise, thereby limiting the output current of the MOS transistor Q1, and further causing the output voltage Vout and the terminal voltage Vctrl to decrease. When the terminal voltage Vctrl drops to Vctrl < Vref, the triode Q3 turns off, and then the MOS transistor Q1 turns off. The power supply control circuit of the utility model is switched from the on self-locking state to the off self-locking state, and the output is cut off, realizing output short circuit or overcurrent protection. The terminal voltage Vctrl changes from a high voltage to a low voltage. Therefore, the calculation method of the current value corresponding to the overcurrent protection action is Vbe / R0.

[0036] The MOS transistor Q1 uses a P-channel MOS transistor, which has lower requirements for the drive circuit in this circuit and can obtain relatively ideal on-off performance. In occasions where the current is small, the performance requirements are not high or the cost is sensitive, the MOS transistor Q1 can be replaced with a PNP type triode.

[0037] The resistor R0 uses a self-restoring fuse PTC, and its own internal resistance is used as the sampling resistor. The calculation method of the protection action current is the same as that of an ordinary resistor. Combining with the overcurrent protection characteristics of the self-restoring fuse PTC itself, better protection action characteristics and protection reliability can be obtained. In occasions with low requirements, the resistor R0 can be replaced with an ordinary resistor.

[0038] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A power supply control circuit with overcurrent protection self-locking and detection function, characterized in that, It includes an output control circuit (1), an overcurrent detection circuit (2), and a self-locking control circuit (3). The input terminal of the overcurrent detection circuit (2) is connected to the power supply input port, the output terminal of the overcurrent detection circuit (2) is connected to the output control circuit (1), the output control circuit (1) is connected to the power supply output port, the self-locking control circuit (3) is connected to the power supply output port and the output control circuit (1) respectively, the self-locking control circuit (3) is connected to the on / off control and status detection port, and the on / off control and status detection port is connected to the external circuit.

2. The power supply control circuit with overcurrent protection self-locking and detection function according to claim 1, characterized in that, The on / off control and status detection port is a bidirectional port for both control signal injection and detection signal output.

3. The power supply control circuit with overcurrent protection self-locking and detection function according to claim 1 or 2, characterized in that, The overcurrent detection circuit (2) includes a transistor Q2 and a resistor R0. The emitter of the transistor Q2 is connected to the power supply input port, and the base and collector of the transistor Q2 are both connected to the output control circuit (1). The base of the transistor Q2 is connected to the emitter through the resistor R0.

4. The power supply control circuit with overcurrent protection self-locking and detection function according to claim 3, characterized in that, The resistor R0 is a self-resetting fuse PTC.

5. The power supply control circuit with overcurrent protection self-locking and detection function according to claim 3, characterized in that, The output control circuit (1) includes a switch Q1, a resistor R1 and a resistor R2. The drain of the switch Q1 is connected to the power supply output port. The gate of the switch Q1 is connected to the source of the switch Q1 through the resistor R1. The gate of the switch Q1 and one end of the resistor R1 are both connected to the base of the transistor Q2. The collector of the transistor Q2 is connected to the other end of the resistor R1. The other end of the resistor R1 is connected to one end of the resistor R2. The other end of the resistor R2 is connected to the self-locking control circuit (3).

6. The power supply control circuit with overcurrent protection self-locking and detection function according to claim 5, characterized in that, The switching transistor is a MOSFET or a PNP transistor.

7. The power supply control circuit with overcurrent protection self-locking and detection function according to claim 6, characterized in that, The MOSFET is a P-channel MOSFET for power output control.

8. The power supply control circuit with overcurrent protection self-locking and detection function according to any one of claims 4-7, characterized in that, The self-locking control circuit (3) includes a transistor Q3, a resistor R3 and a resistor R4. The collector of transistor Q3 is connected to the other end of resistor R2 of the output control circuit (1). The emitter of transistor Q3 is grounded through a reference voltage source. The base of transistor Q3 is connected to one end of resistor R3 and one end of resistor R4 respectively. The other end of resistor R3 is connected to the power supply output port and the drain of the switching transistor Q1 respectively. The other end of resistor R4 is grounded.

9. The power supply control circuit with overcurrent protection self-locking and detection function according to claim 8, characterized in that, The reference voltage source is obtained by voltage division of the power supply, or the reference voltage source is provided by a Zener diode or a reference source; the power supply input port is connected to the positive terminal of the power supply, and the negative terminal of the power supply is grounded; the power supply output port is connected to the load.

10. The power supply control circuit with overcurrent protection self-locking and detection function according to claim 9, characterized in that, The current value corresponding to the overcurrent protection action is the on-state voltage of transistor Q2 divided by the resistance value of resistor R0.

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