Overcurrent protection circuit system for realizing power output

Abstract

The invention relates to an overcurrent protection circuit system for realizing power output, which comprises a power output control circuit, a power output circuit, an overcurrent turn-off circuit, an output monitoring circuit and an MCU (Microprogrammed Control Unit), and is characterized in that the power output control circuit is connected with the MCU, the power output circuit is connected with an input power supply, and the power output circuit is connected with the power output control circuit; the overcurrent turn-off circuit is connected with the power supply output circuit, the output monitoring circuit is connected with the power supply output circuit and the MCU, and the output monitoring circuit is also connected with the output end. By adopting the over-current protection circuit system for realizing power supply output, higher power supply voltage can be provided for a load, when the output circuit adopts a PMOS (P-channel Metal Oxide Semiconductor) for output, load current similar to that of a high-side driving chip can be provided, and the circuit cost is reduced. The defects of the background technology are effectively overcome, the influence of the load current of the power output end on the size of the current-limiting resistor is avoided, and the problem that the voltage drop of the power input end and the power output end of the power output circuit is large is solved.

Description

Technical Field

[0001] The present invention relates to the field of protection circuits, in particular to the field of overcurrent protection circuits for power output circuits, and specifically refers to an overcurrent protection circuit system for realizing power output. Background Art

[0002] In the prior art, comparative document 1 "Overcurrent protection circuit for vehicle-mounted ECU output power supply" CN212435348U discloses an overcurrent protection circuit based on a current limiting resistor and a transistor, which can detect the output current through the current limiting resistor and shut down the output short circuit through the transistor when the current exceeds the rated value, thereby achieving the purpose of overcurrent protection.

[0003] Comparative Document 1 solves the problem of PMOS output overcurrent protection, but still has the following technical defects:

[0004] 1. The size of the current that needs to be output will affect the size and price of the current limiting resistor. The larger the current, the larger the resistor size, the higher the price, and the more space it occupies on the PCB.

[0005] 2. The existence of the current limiting resistor will cause the voltage drop between the power supply and the output end to increase. When the power supply input voltage is low and the load current demand is large, the output demand of the specified load voltage cannot be met. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an overcurrent protection circuit system for realizing power supply output which has the advantages of simple circuit, low circuit cost and wide application range.

[0007] In order to achieve the above object, the overcurrent protection circuit system for power supply output of the present invention is as follows:

[0008] The overcurrent protection circuit system for realizing power output has the following main features: the system comprises a power output control circuit, a power output circuit, an overcurrent shutdown circuit, an output monitoring circuit and an MCU; the power output control circuit is connected to the MCU; the power output circuit is connected to the input power supply; the power output circuit is connected to the power output control circuit; the overcurrent shutdown circuit is connected to the power output circuit; the output monitoring circuit is connected to the power output circuit and the MCU; and the output monitoring circuit is also connected to the output end; the power output circuit is used for power output; when the output current reaches a certain threshold, the conduction voltage drop of the output circuit becomes larger; the overcurrent shutdown circuit controls the conduction and shutdown of the first transistor Q1 through the second transistor Q2 in the power output circuit, so as to realize forced shutdown of the second transistor Q2 when the output is overcurrent, and the overcurrent shutdown threshold is adjustable.

[0009] Preferably, the power output control circuit includes a third triode Q3, a seventh resistor R7 and an eighth resistor R8, the base of the third triode Q3 is connected to one end of the seventh resistor R7, the other end of the seventh resistor R7 is connected to the MCU, the emitter of the third triode Q3 is grounded, one end of the eighth resistor R8 is connected to the base of the third triode Q3, the other end of the eighth resistor R8 is connected to the emitter of the third triode Q3, and the collector of the third triode Q3 is connected to the power output circuit.

[0010] Preferably, when the GPIO pin of the MCU outputs a low level, the third transistor Q3 is in a cut-off state, and PIN3 of the third transistor Q3 is in a suspended state; when the GPIO pin of the MCU outputs a high level, the third transistor Q3 is turned on, and PIN3 of the third transistor Q3 is turned to ground.

[0011] Preferably, the power output circuit includes a second triode Q2, a third resistor R3, a fifth resistor R5, a first diode D1 and a first capacitor C1, the base of the second triode Q2 is connected to one end of the fifth resistor R5, the other end of the fifth resistor R5 is connected to the collector of the third triode Q3 of the power output control circuit, the emitter of the second triode Q2 is connected to the input power supply, the collector of the second triode Q2 is connected to the positive electrode of the first diode D1, the negative electrode of the first diode D1 is connected to the output end, one end of the first capacitor C1 is connected to the output end, and the other end is grounded, one end of the third resistor R3 is connected to the base of the second triode Q2, and the other end is connected to the emitter of the second triode Q2; the fifth resistor R5 is used to adjust the saturation conduction current range of the second triode Q2, the first diode D1 is used to prevent external high voltage, and the first capacitor C1 is used to resist external interference.

[0012] Preferably, when PIN3 of the third transistor Q3 of the power output control circuit is in a suspended state, the voltages at both ends of the third resistor R3 are consistent, the second transistor Q2 is in a cut-off state, and the power output is disconnected; when PIN3 of the third transistor Q3 is connected to ground, the third resistor R3 and the fifth resistor R5 divide the voltage, so that the second transistor Q2 is turned on and the power output is turned on.

[0013] Preferably, the overcurrent shutdown circuit includes a first transistor Q1, a first resistor R1 and a second resistor R2, the base of the first transistor Q1 is connected to the second resistor R2, the other end of the second resistor R2 is connected to the power supply output control circuit, the collector and emitter of the first transistor Q1 are both connected to the output control circuit, one end of the first resistor R1 is connected to the base of the first transistor Q1, and the other end is connected to the emitter of the first transistor Q1.

[0014] Preferably, when the load current of the overcurrent shutdown circuit is small, the voltage drop between PIN2 and PIN3 of the second transistor Q2 is low, the first transistor Q1 is in the cut-off state, and the power supply is output normally;

[0015] When the load current is large, the voltage drop between PIN2 and PIN3 of the second transistor Q2 increases, and the voltage across R1 increases, controlling the first transistor Q1 to turn on, reducing the voltage drop between PIN2 and PIN1 of the second transistor Q2, and the second transistor Q2 enters the cut-off state, disconnecting the power output;

[0016] When the load impedance increases, the voltage across the first resistor R1 decreases. When the voltage decreases to a level where the first transistor Q1 cannot be saturated and turned on, the first transistor Q1 enters the cut-off state. If the GPIO of the MCU continues to output high and low levels at this time, the second transistor Q2 resumes the on state.

[0017] Preferably, the output monitoring circuit includes a fourth resistor R4, a sixth resistor R6 and a second capacitor C2. The fourth resistor R4 and the sixth resistor R6 are connected, the other end of the fourth resistor R4 is connected to the power output circuit, the other end of the sixth resistor R6 is grounded, one end of the second capacitor C2 is connected to the middle point of the fourth resistor R4 and the sixth resistor R6, and the other end is grounded. The fourth resistor R4 and the sixth resistor R6 form a voltage divider circuit to divide the voltage of the power output port and output it to the ADC port of the MCU. The second capacitor C2 is used for hardware filtering of the monitoring signal.

[0018] Preferably, when the output monitoring circuit outputs voltage, the MCU monitors the output voltage through the ADC port. After the power output port is short-circuited to ground or power, the MCU determines whether the circuit is abnormal based on the output level state of the GPIO and the voltage value read by the ADC.

[0019] Preferably, the power output circuit adjusts the output current range of the second transistor Q2 by modifying the resistance values ​​of the third resistor R3 and the fifth resistor R5; or

[0020] Preferably, the over-current shutdown circuit adjusts the over-current shutdown threshold of the power output circuit by modifying the resistance values ​​of the first resistor R1 and the second resistor R2.

[0021] The overcurrent protection circuit system for realizing power output of the present invention is adopted. The overcurrent shutdown threshold can be modified by simply modifying the resistance value of the overcurrent shutdown circuit. The PCB space occupancy is low and the circuit cost is low. The voltage drop between the power input and output ends of the power output circuit is reduced. Compared with the current limiting resistor solution, a higher power supply voltage can be provided to the load to avoid load performance reduction during operation. When the output circuit adopts PMOS for output, a load current similar to that of the high-side driver chip can be provided, reducing the circuit cost. The present invention effectively overcomes the shortcomings of the background technology, avoids the influence of the load current size of the power output end on the size of the current limiting resistor, and also solves the problem of large voltage drop between the power input and output ends of the power output circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a circuit diagram of the prior art.

[0023] Figure 2 The present invention is a circuit diagram of an overcurrent protection circuit system for implementing power supply output.

[0024] Figure 3 The circuit diagram of a specific embodiment of the overcurrent protection circuit system for power supply output of the present invention is shown. DETAILED DESCRIPTION

[0025] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0026] The overcurrent protection circuit system for realizing power output of the present invention includes a power output control circuit, a power output circuit, an overcurrent shutdown circuit, an output monitoring circuit and an MCU, wherein the power output control circuit is connected to the MCU, the power output circuit is connected to the input power supply, the power output circuit is connected to the power output control circuit, the overcurrent shutdown circuit is connected to the power output circuit, the output monitoring circuit is connected to the power output circuit and the MCU, and the output monitoring circuit is also connected to the output end; the power output circuit is used for power output, when the output current reaches a certain threshold, the conduction voltage drop of the output circuit becomes larger, the overcurrent shutdown circuit controls the conduction and shutdown of the first transistor Q1 through the second transistor Q2 in the power output circuit, so as to realize forced shutdown of the second transistor Q2 when the output is overcurrent, and the overcurrent shutdown threshold is adjustable.

[0027] As a preferred embodiment of the present invention, the power output control circuit includes a third triode Q3, a seventh resistor R7 and an eighth resistor R8, the base of the third triode Q3 is connected to one end of the seventh resistor R7, the other end of the seventh resistor R7 is connected to the MCU, the emitter of the third triode Q3 is grounded, one end of the eighth resistor R8 is connected to the base of the third triode Q3, the other end of the eighth resistor R8 is connected to the emitter of the third triode Q3, and the collector of the third triode Q3 is connected to the power output circuit.

[0028] As a preferred embodiment of the present invention, when the GPIO pin of the MCU outputs a low level, the third transistor Q3 is in a cut-off state, and PIN3 of the third transistor Q3 is in a suspended state; when the GPIO pin of the MCU outputs a high level, the third transistor Q3 is turned on, and PIN3 of the third transistor Q3 is turned to ground.

[0029] As a preferred embodiment of the present invention, the power output circuit includes a second transistor Q2, a third resistor R3, a fifth resistor R5, a first diode D1 and a first capacitor C1, the base of the second transistor Q2 is connected to one end of the fifth resistor R5, the other end of the fifth resistor R5 is connected to the collector of the third transistor Q3 of the power output control circuit, the emitter of the second transistor Q2 is connected to the input power supply, the collector of the second transistor Q2 is connected to the positive electrode of the first diode D1, the negative electrode of the first diode D1 is connected to the output end, one end of the first capacitor C1 is connected to the output end, and the other end is grounded, one end of the third resistor R3 is connected to the base of the second transistor Q2, and the other end is connected to the emitter of the second transistor Q2; the fifth resistor R5 is used to adjust the saturation conduction current range of the second transistor Q2, the first diode D1 is used to prevent external high voltage, and the first capacitor C1 is used to resist external interference.

[0030] As a preferred embodiment of the present invention, when PIN3 of the third transistor Q3 of the power output control circuit is in a suspended state, the voltages at both ends of the third resistor R3 are consistent, the second transistor Q2 is in a cut-off state, and the power output is disconnected; when PIN3 of the third transistor Q3 is connected to ground, the third resistor R3 and the fifth resistor R5 divide the voltage, so that the second transistor Q2 is turned on, and the power output is turned on.

[0031] As a preferred embodiment of the present invention, the overcurrent shutdown circuit includes a first transistor Q1, a first resistor R1 and a second resistor R2, the base of the first transistor Q1 is connected to the second resistor R2, the other end of the second resistor R2 is connected to the power supply output control circuit, the collector and emitter of the first transistor Q1 are both connected to the output control circuit, one end of the first resistor R1 is connected to the base of the first transistor Q1, and the other end is connected to the emitter of the first transistor Q1.

[0032] As a preferred embodiment of the present invention, when the load current of the overcurrent shutdown circuit is small, the voltage drop between PIN2 and PIN3 of the second transistor Q2 is low, the first transistor Q1 is in the cut-off state, and the power supply output is normal;

[0033] When the load current is large, the voltage drop between PIN2 and PIN3 of the second transistor Q2 increases, and the voltage across R1 increases, controlling the first transistor Q1 to turn on, reducing the voltage drop between PIN2 and PIN1 of the second transistor Q2, and the second transistor Q2 enters the cut-off state, disconnecting the power output;

[0034] When the load impedance increases, the voltage across the first resistor R1 decreases. When the voltage decreases to a level where the first transistor Q1 cannot be saturated and turned on, the first transistor Q1 enters the cut-off state. If the GPIO of the MCU continues to output high and low levels at this time, the second transistor Q2 resumes the on state.

[0035] As a preferred embodiment of the present invention, the output monitoring circuit includes a fourth resistor R4, a sixth resistor R6 and a second capacitor C2. The fourth resistor R4 and the sixth resistor R6 are connected, the other end of the fourth resistor R4 is connected to the power output circuit, the other end of the sixth resistor R6 is grounded, one end of the second capacitor C2 is connected to the middle point of the fourth resistor R4 and the sixth resistor R6, and the other end is grounded. The fourth resistor R4 and the sixth resistor R6 form a voltage divider circuit to divide the voltage of the power output port and output it to the ADC port of the MCU. The second capacitor C2 is used for hardware filtering of the monitoring signal.

[0036] As a preferred embodiment of the present invention, when the output monitoring circuit outputs voltage, the MCU monitors the output voltage through the ADC port. After the power output port is short-circuited to the ground or the power is on, the MCU determines whether the circuit is abnormal based on the output level state of the GPIO and the voltage value read by the ADC.

[0037] As a preferred embodiment of the present invention, the power output circuit adjusts the output current range of the second transistor Q2 by modifying the resistance values ​​of the third resistor R3 and the fifth resistor R5; or

[0038] As a preferred embodiment of the present invention, the over-current shutdown circuit adjusts the over-current shutdown threshold of the power output circuit by modifying the resistance values ​​of the first resistor R1 and the second resistor R2.

[0039] In a specific embodiment of the present invention, an overcurrent protection circuit is provided that is not limited by a current limiting resistor and can reduce the voltage drop between the power input and output ends, ensuring that the power output circuit can meet the load current requirements of different usage scenarios when outputting the power voltage with a lower voltage difference. At the same time, the overcurrent shutdown threshold can be modified without changing the resistor size, so that when the load current at the power output end is greater than the set value, the power output is turned off, and when the load at the power output end is reduced, the power output can be automatically restored, thereby achieving the overcurrent protection function.

[0040] like Figure 2 As shown, the power input of this circuit system is VBAT, the output is VOUT, and it consists of four parts:

[0041] 1. Power output control circuit: It is composed of Q3, R7 and R8. Q3 is NPN or NMOS. When the MCU's GPIO outputs a low level, Q3 is in the cut-off state, and PIN3 of Q3 is in a floating state. When the MCU's GPIO outputs a high level, Q3 is turned on, and PIN3 of Q3 is connected to the ground.

[0042] 2. Power output circuit: It is composed of Q2, R3, R5, D1 and C1. Q3 is PNP or PMOS. When PIN3 of Q3 is in floating state, the voltages at both ends of R3 are consistent, Q2 is in cut-off state, and the power output is disconnected. When PIN3 of Q3 is connected to ground, R3 and R5 divide the voltage to make Q2 turned on and turn on the power output. R5 is used to adjust the saturation conduction current range of Q2. D1 is used to prevent external high voltage and C1 is used to resist external interference.

[0043] 3. Overcurrent shutdown circuit: It is composed of Q1, R1, and R2. Q1 is PNP. When the load current is small, the voltage drop between PIN2 and PIN3 of Q2 is low, Q1 is in the cut-off state, and the power supply outputs normally. When the load current is large, the voltage drop between PIN2 and PIN3 of Q2 increases, and the voltage across R1 increases, thereby controlling Q1 to turn on, lowering the voltage drop between PIN2 and PIN1 of Q2, and Q2 enters the cut-off state, disconnecting the power supply output. When the load impedance increases, the voltage across R1 decreases. When the voltage decreases to the point where Q1 cannot be saturated and turned on, Q1 enters the cut-off state. If the GPIO of the MCU continues to output high and low levels at this time, Q2 resumes the on state.

[0044] 4. Output monitoring circuit: It is composed of R4, R6 and C2. R4 and R6 form a voltage divider circuit to divide the voltage of the power output port and output it to the ADC port of the MCU. C2 is used for hardware filtering of the monitoring signal. When the power outputs voltage, the MCU can monitor the output voltage through the ADC port. When the power output port is short-circuited to the ground or the power is on, the MCU can determine whether the circuit is abnormal based on the output level status of the GPIO and the voltage value read by the ADC.

[0045] An overcurrent protection method for a power output circuit of the present invention mainly comprises a power output circuit and an overcurrent shutdown circuit.

[0046] The power output circuit mainly uses PNP or PMOS for power output. When the output current reaches a certain threshold, the conduction voltage drop of the output circuit will increase significantly.

[0047] The overcurrent shutdown circuit can control the on and off of Q1 through the voltage drop between Q2 PIN2 and PIN3 in the power output circuit, so as to achieve the function of quickly and forcibly shutting down Q2 when the output of Q2 is overcurrent, and the overcurrent shutdown threshold is adjustable.

[0048] The power supply output circuit can adjust the output current range of Q2 by modifying the resistance values ​​of R3 and R5.

[0049] The overcurrent shutdown circuit can adjust the overcurrent shutdown threshold of the power supply output circuit by modifying the resistance values ​​of R1 and R2.

[0050] For power output circuits that need to resist external high voltage, pulse or electrostatic interference, anti-reverse diodes and ceramic capacitors can be added to the power output to increase system reliability.

[0051] The power output circuit can be controlled by a power output control circuit. The MCU controls the on and off of Q3 by outputting high and low levels, thereby indirectly controlling the on and off of Q2.

[0052] If the system requires voltage monitoring of the power supply output, an output monitoring circuit can be added. The monitoring range of the output voltage can be adjusted by modifying the resistance values ​​of R4 and R5, and the hardware filtering parameters of the output voltage monitoring signal can be adjusted by modifying the capacitance value of C2.

[0053] In a specific embodiment, Figure 3 For example, assume VBAT = 12V.

[0054] 1. Power output control circuit: It consists of Q3, R7, and R8. Q3 is NPN. When the MCU's GPIO outputs a low level, the voltage across R8 is lower than 0.3V, which is lower than the saturation voltage drop of Q3's BE pole. There is no current at Q3's B pole. At this time, Q3 is in the cut-off state, and Q3's PIN3 is suspended. When the MCU's GPIO outputs a high level of 5V, R2 and R8 divide the voltage. The voltage across R8 is calculated to be 4.1V. Since Q3's BE pole saturation voltage drop is about 0.7V, the voltage across R8 is 0.7V, and R7's current is about 1.95mA. The minimum gain of Q3 is 100. Therefore, when the current flowing through Q3 PIN3 is less than 188mA, Q3 is in the on state, and Q3's PIN3 is connected to the ground.

[0055] 2. Power output circuit: It is composed of Q2, R3, R5, D1 and C1. Q2 is PNP. When PIN3 of Q3 is suspended, the voltage across R3 is VBAT, and there is no current in the B pole of Q2. Q2 is in the cut-off state, and the power output is disconnected. When PIN3 of Q3 is connected to the ground, R3 and R5 divide the voltage. The voltage across R3 is calculated to be 9.8V. Since the saturation voltage drop of the EB pole of Q2 is about 0.7V, the voltage across R3 is 0.7V, and the current of R5 is about 5.1mA. The gain of Q2 is 100. Therefore, when the current flowing through Q2PIN3 is less than 503mA, Q2 is in the on state, and the power output is turned on. The maximum reverse withstand voltage of D1 is 60V, which can ensure that the power output circuit is not damaged when the power output port is short-circuited to a maximum of 72V. C1 is a 10nF capacitor, which can absorb part or all of the energy of electrostatic interference or other pulse interference to protect the power output circuit.

[0056] 3. Overcurrent shutdown circuit: It consists of Q1, R1, and R2. Q1 is PNP. When the power supply output current is lower than 503mA, the voltage drop between PIN2 and PIN3 of Q2 is lower than the saturation voltage drop of the CE pole. After R1 and R2 are divided, the voltage across R1 is lower than the saturation voltage drop of the BE pole of Q1. There is no current at the B pole of Q1. Q1 is in the cut-off state. The power supply outputs normally. The gain of Q1 is 100. When Q1 and Q3 are turned on, the current of R5 is about 5.45mA. At this time, the current of the B pole of Q1 should be greater than 54.5uA. When the power supply output current is higher than 503mA, the PIN2 and The voltage drop between PIN3 will increase with the increase of current, causing the voltage across R1 to increase. When the voltage across R1 is greater than the saturation voltage drop of Q1's BE pole and the current of Q1's B pole is greater than 54.5uA, Q1 is turned on, lowering the voltage drop between Q2's PIN2 and PIN1, and Q2 enters the cut-off state, disconnecting the power supply output. When the load current decreases and the load impedance increases, the voltage across R1 decreases. When the voltage is lower than the saturation voltage drop of Q1's BE pole, there is no current at Q1's B pole, and Q1 is in the cut-off state. If the MCU's GPIO continues to output high and low levels at this time, Q2 resumes the on state.

[0057] 4. Output monitoring circuit: It is composed of R4, R6, and C2. The maximum saturation voltage drop of the CE pole of Q2 is 0.25V. R4 and R6 form a voltage divider circuit. The normal output power supply voltage range is 11.75V~12V. The voltage divided to the MCU ADC port is approximately 2.8V~2.86V. Combined with the accuracy of the voltage divider resistor and the ADC sampling error, when the GPIO outputs a high level and the ADC port voltage is lower than a certain voltage threshold below 2.8V, the MCU should determine that the power output is overcurrent or short-circuited and turn off the power output. When the GPIO outputs a high level and the ADC port voltage is higher than a certain voltage threshold above 2.86V, the MCU should determine that the power output port is short-circuited to high voltage and turn off the power output. C2 and R4 form an RC filter with a filtering time of 7.5us, which can filter out voltage changes with a frequency of approximately 133KHz or above.

[0058] MCU is the abbreviation of Microcontroller Unit, which refers to a single-chip microcomputer; GPIO is the abbreviation of General Purpose Input / Output, which refers to general-purpose input and output; PMOS is the abbreviation of Positive Channel Metal Oxide Semiconductor, which refers to P-channel field effect transistor; NMO is the abbreviation of Negative Channel Metal-Oxide-Semiconductor, which refers to N-channel field effect transistor; PNP refers to PNP transistor; NPN refers to NPN transistor; PCB refers to Printed circuit board.

[0059] The load current requirements for power output circuits vary greatly among different products, especially in vehicle-mounted controllers, which control several to dozens of power outputs and require currents ranging from 10mA to 20A. If current limiting resistor detection is used for overcurrent protection, the circuit layout and cost will vary greatly. At the same time, the size of the power supply voltage output to the load also has a certain impact on the operating state of the load, such as the brightness of the load light, the driving capability of the load motor, etc.

[0060] The specific implementation scheme of this embodiment can refer to the relevant description in the above embodiment, which will not be repeated here.

[0061] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0062] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0063] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0064] The overcurrent protection circuit system for realizing power output of the present invention is adopted. The overcurrent shutdown threshold can be modified by simply modifying the resistance value of the overcurrent shutdown circuit. The PCB space occupancy is low and the circuit cost is low. The voltage drop between the power input and output ends of the power output circuit is reduced. Compared with the current limiting resistor solution, a higher power supply voltage can be provided to the load to avoid load performance reduction during operation. When the output circuit adopts PMOS for output, a load current similar to that of the high-side driver chip can be provided, reducing the circuit cost. The present invention effectively overcomes the shortcomings of the background technology, avoids the influence of the load current size of the power output end on the size of the current limiting resistor, and also solves the problem of large voltage drop between the power input and output ends of the power output circuit.

[0065] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A circuit system for overcurrent protection of power supply output, characterized in that: The system comprises a power output control circuit, a power output circuit, an overcurrent shutdown circuit, an output monitoring circuit and an MCU. The power output control circuit is connected to the MCU, the power output circuit is connected to an input power supply, the power output circuit is connected to the power output control circuit, the overcurrent shutdown circuit is connected to the power output circuit, the output monitoring circuit is connected to the power output circuit and the MCU, and the output monitoring circuit is also connected to an output end; the power output circuit is used for power output, when the output current reaches a certain threshold, the conduction voltage drop of the output circuit increases, the overcurrent shutdown circuit controls the conduction and shutdown of the first transistor Q1 through the second transistor Q2 in the power output circuit, so as to realize forced shutdown of the second transistor Q2 when the output is overcurrent, and the overcurrent shutdown threshold is adjustable.

2. The overcurrent protection circuit system for realizing power supply output according to claim 1, characterized in that: The power output control circuit includes a third triode Q3, a seventh resistor R7 and an eighth resistor R8, the base of the third triode Q3 is connected to one end of the seventh resistor R7, the other end of the seventh resistor R7 is connected to the MCU, the emitter of the third triode Q3 is grounded, one end of the eighth resistor R8 is connected to the base of the third triode Q3, the other end of the eighth resistor R8 is connected to the emitter of the third triode Q3, and the collector of the third triode Q3 is connected to the power output circuit.

3. The overcurrent protection circuit system for realizing power supply output according to claim 2, characterized in that: When the GPIO pin of the MCU outputs a low level, the third transistor Q3 is in a cut-off state, and PIN3 of the third transistor Q3 is in a suspended state; when the GPIO pin of the MCU outputs a high level, the third transistor Q3 is turned on, and PIN3 of the third transistor Q3 is turned to ground.

4. The overcurrent protection circuit system for realizing power supply output according to claim 1, characterized in that: The power output circuit includes a second triode Q2, a third resistor R3, a fifth resistor R5, a first diode D1 and a first capacitor C1, the base of the second triode Q2 is connected to one end of the fifth resistor R5, the other end of the fifth resistor R5 is connected to the collector of the third triode Q3 of the power output control circuit, the emitter of the second triode Q2 is connected to the input power supply, the collector of the second triode Q2 is connected to the positive electrode of the first diode D1, the negative electrode of the first diode D1 is connected to the output end, one end of the first capacitor C1 is connected to the output end, and the other end is grounded, one end of the third resistor R3 is connected to the base of the second triode Q2, and the other end is connected to the emitter of the second triode Q2; the fifth resistor R5 is used to adjust the saturation conduction current range of the second triode Q2, the first diode D1 is used to prevent external high voltage, and the first capacitor C1 is used to resist external interference.

5. The overcurrent protection circuit system for realizing power supply output according to claim 4, characterized in that: When PIN3 of the third transistor Q3 of the power output control circuit is in a suspended state, the voltages at both ends of the third resistor R3 are consistent, the second transistor Q2 is in a cut-off state, and the power output is disconnected; when PIN3 of the third transistor Q3 is connected to the ground, the third resistor R3 and the fifth resistor R5 divide the voltage, so that the second transistor Q2 is turned on, and the power output is turned on.

6. The overcurrent protection circuit system for realizing power supply output according to claim 1, characterized in that: The overcurrent shutdown circuit includes a first transistor Q1, a first resistor R1 and a second resistor R2, the base of the first transistor Q1 is connected to the second resistor R2, the other end of the second resistor R2 is connected to the power output control circuit, the collector and emitter of the first transistor Q1 are both connected to the output control circuit, one end of the first resistor R1 is connected to the base of the first transistor Q1, and the other end is connected to the emitter of the first transistor Q1.

7. The overcurrent protection circuit system for realizing power supply output according to claim 6, characterized in that: When the load current of the overcurrent shutdown circuit is small, the voltage drop between PIN2 and PIN3 of the second transistor Q2 is low, the first transistor Q1 is in the cut-off state, and the power supply output is normal; When the load current is large, the voltage drop between PIN2 and PIN3 of the second transistor Q2 increases, and the voltage across R1 increases, controlling the first transistor Q1 to turn on, reducing the voltage drop between PIN2 and PIN1 of the second transistor Q2, and the second transistor Q2 enters the cut-off state, disconnecting the power output; When the load impedance increases, the voltage across the first resistor R1 decreases. When the voltage decreases to a level where the first transistor Q1 cannot be saturated and turned on, the first transistor Q1 enters the cut-off state. If the GPIO of the MCU continues to output high and low levels at this time, the second transistor Q2 resumes the on state.

8. The overcurrent protection circuit system for realizing power output according to claim 1, characterized in that: The output monitoring circuit includes a fourth resistor R4, a sixth resistor R6 and a second capacitor C2. The fourth resistor R4 and the sixth resistor R6 are connected, the other end of the fourth resistor R4 is connected to the power output circuit, the other end of the sixth resistor R6 is grounded, one end of the second capacitor C2 is connected to the middle point of the fourth resistor R4 and the sixth resistor R6, and the other end is grounded. The fourth resistor R4 and the sixth resistor R6 form a voltage divider circuit to divide the voltage of the power output port and output it to the ADC port of the MCU. The second capacitor C2 is used for hardware filtering of the monitoring signal.

9. The overcurrent protection circuit system for realizing power supply output according to claim 8, characterized in that: When the output monitoring circuit outputs voltage, the MCU monitors the output voltage through the ADC port. After the power output port is short-circuited to the ground or the power supply, the MCU determines whether the circuit is abnormal based on the output level state of the GPIO and the voltage value read by the ADC.

10. The overcurrent protection circuit system for realizing power supply output according to claim 1, characterized in that: The power output circuit adjusts the output current range of the second transistor Q2 by modifying the resistance values ​​of the third resistor R3 and the fifth resistor R5; or The over-current shutdown circuit adjusts the over-current shutdown threshold of the power output circuit by modifying the resistance values ​​of the first resistor R1 and the second resistor R2.

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