An overcurrent protection circuit with automatic latching function

Abstract

The present invention discloses an overcurrent protection circuit with an automatic latching function, comprising a feedback control module, a main control switch module and a current detection module connected in sequence, a filter unit connected to a power supply to output electric energy to the main control switch module, and provide a stable voltage for the load, the feedback control module is used to receive the signal of the current detection module and control the on and off of the main control switch module, the main control switch module is connected to the power supply, and the main control switch module controls the on and off of the power supply, the current detection module is used to detect the current of the load line and transmit the signal to the feedback control module, and a latch unit is also provided between the feedback control module and the main control switch, and the latch unit is used to latch the control signal output by the current detection module to the feedback control module; the intelligent triggering of the overcurrent signal is realized by adding a detection resistor through the PN junction property of the base and emitter of the transistor, and the response time is short and the reliability is high. The current detection sensitivity and the adjustable overcurrent threshold value are realized by the detection resistor.

Description

Technical Field

[0001] The invention relates to the field of overcurrent protection, and in particular to an overcurrent protection circuit with an automatic latching function. Background Art

[0002] Overcurrent protection refers to a protection method that causes the protection device to operate when the current exceeds a predetermined maximum value. When the current flowing through the protected component exceeds a predetermined value, the protection device is activated, causing the circuit breaker to trip or give an alarm signal. If an overcurrent protection device is not set, once the current in some circuits is too large due to a short circuit or abnormal components, it is easy to burn out the components, especially in some circuits that are sensitive to current changes. In serious cases, it may even cause fire accidents due to excessive current. Therefore, it is necessary to set up an overcurrent protection circuit. The existing overcurrent protection device responds more accurately to changes in large currents, but responds slowly or even cannot detect relatively small overcurrents. This phenomenon easily leads to the overcurrent protection device being able to work only in the case of a short circuit or a large current change. If it needs to wait for the current to rise to a higher level before it works, some components that are sensitive to current will be broken down and burned during the current rise process. At the same time, the existing overcurrent protection circuit has an unreliable separation phenomenon during reuse, that is, after the overcurrent protection responds, the separation of the control switch and the load circuit is not complete. Therefore, an overcurrent protection circuit is required which has a quick response and can latch the control to ensure complete disconnection. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an overcurrent protection circuit which is simple and reliable to use, low cost, low latency, has an adjustable overcurrent threshold and can quickly cut off the load power supply and automatically latch when an overcurrent fault occurs.

[0004] The technical solution adopted by the present invention to solve the above technical problems is: an overcurrent protection circuit with an automatic latching function, comprising a feedback control module, a main control switch module and a current detection module connected in sequence, the filtering unit is connected to the power supply to filter out the input power supply noise and output the filtered electric energy to the main control switch module, and provide a stable voltage for the load, the feedback control module is used to receive the signal of the current detection module and control the on and off of the main control switch module, the main control switch module is connected to the power supply and supplies power to the load line where the current detection module is located, and the main control switch module controls the on and off of the power supply, the current detection module is used to detect the current of the load line and transmit the signal to the feedback control module, and a latch unit is also arranged between the feedback control module and the main control switch, and the latch unit is used to latch the control signal output by the current detection module to the feedback control module.

[0005] Furthermore, the power supply includes a power line connected to the positive electrode and a ground line connected to the negative electrode, the main control switch includes a first field effect transistor and a second field effect transistor, the source of the first field effect transistor is connected to the power line, the gate of the first field effect transistor is connected to one end of the first resistor and one end of the second resistor, the other end of the first resistor is connected to the power supply, the other end of the second resistor is connected to the drain of the second field effect transistor, the source of the second field effect transistor is connected to the ground line, the gate of the second field effect transistor is connected to the feedback control module, and the drain of the first field effect transistor is connected to the current detection module.

[0006] Furthermore, the feedback control module includes a first transistor, the collector of the first transistor is connected to the gate of the second field effect transistor, the emitter of the first transistor is connected to the ground line, the collector of the first transistor is also connected to the power line through a third resistor, and the base of the first transistor is connected to the current detection module through a fourth resistor.

[0007] Furthermore, the current detection module includes a detection resistor and a second transistor, the emitter of the second transistor is connected to one end of the detection resistor and the drain of the first field effect transistor, the base of the second transistor is connected to the other end of the detection resistor, the other end of the detection resistor is also connected to the load, the collector of the second transistor is connected to one end of the fifth resistor, one end of the fifth resistor is also connected to the fourth resistor, and the other end of the fifth resistor is connected to the ground wire.

[0008] Furthermore, the latch unit includes a third transistor and a fourth transistor, the base of the third transistor is connected to the collector of the first transistor and the gate of the second field effect transistor, the emitter of the third transistor is connected to the power line through a sixth resistor, the collector of the third transistor is connected to the ground line through a seventh resistor, the base of the fourth transistor is connected to the collector of the third transistor, the emitter of the fourth transistor is connected to the ground line, and the collector of the fourth transistor is connected to the base of the third transistor.

[0009] Furthermore, the filtering unit includes a filtering inductor, one end of the filtering inductor is connected to the power supply, the other end of the filtering inductor is connected to the source of the first field effect transistor, one end of the filtering inductor is connected to the ground wire through the first capacitor, and the other end of the filtering inductor is connected to the ground wire through the second capacitor.

[0010] The advantages of the present invention are that fast response, overcurrent protection and self-locking functions with adjustable overcurrent threshold are achieved through fewer low-cost discrete components, and can be applied to different current requirements in different occasions. Intelligent triggering of overcurrent signals is achieved by adding detection resistors to the PN junction properties of the transistor base and emitter, replacing the more expensive comparator plus microcontroller solution, which has great advantages in terms of cost, response time and reliability. The current detection sensitivity and adjustability of the overcurrent threshold size are achieved through detection resistors, replacing the comparator plus MCU solution that requires additional reference voltage source and reference current source, has poor adjustability and is limited in application scenarios. By adding a self-locking module, the overcurrent signal detected by the current detection module can be fed back to the feedback control module, and then transmitted to the self-locking module to lock the main switch in the overcurrent off state, thereby ensuring the reliable disconnection of the main control switch module, and completely disconnecting the load line from the power supply part, effectively improving safety and reliability, and avoiding excessive current in the load line from acting reversely on the power supply, causing accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a block diagram of the working principle of the present invention;

[0012] Figure 2 Schematic diagram of the circuit connection principle of the invention. DETAILED DESCRIPTION

[0013] The present invention is further described in detail below with reference to the accompanying drawings.

[0014] An overcurrent protection circuit with an automatic latching function comprises a feedback control module, a main control switch module and a current detection module connected in sequence, the feedback control module is used to receive a signal from the current detection module and control the on and off of the main control switch module, the main control switch module is connected to a power supply and supplies power to a load line where the current detection module is located, and the main control switch module controls the on and off of the power supply, the current detection module is used to detect the current of the load line and transmit the signal to the feedback control module, and a latch unit is also provided between the feedback control module and the main control switch, the latch unit is used to latch the control signal output from the current detection module to the feedback control module.

[0015] The above-mentioned power supply includes a power line connected to the positive electrode and a ground line connected to the negative electrode, the main control switch includes a first field effect tube and a second field effect tube M2, the source of the first field effect tube M1 is connected to the power line, the gate of the first field effect tube M1 is connected to one end of the first resistor R1 and one end of the second resistor R2, the other end of the first resistor R1 is connected to the power supply, the other end of the second resistor R2 is connected to the drain of the second field effect tube M2, the source of the second field effect tube M2 is connected to the ground line, the gate of the second field effect tube M2 is connected to the feedback control module, and the drain of the first field effect tube M1 is connected to one end of the inspection resistor of the current detection module.

[0016] The above-mentioned feedback control module includes a first transistor Q1, the collector of the first transistor Q1 is connected to the gate of the second field effect transistor M2, the emitter of the first transistor Q1 is connected to the ground line, the collector of the first transistor Q1 is also connected to the power line through the third resistor R3, and the base of the first transistor Q1 is connected to the collector of the second transistor Q2 of the current detection module through the fourth resistor R4.

[0017] The above-mentioned current detection module includes a detection resistor R6 and a second transistor Q2, the emitter of the second transistor Q2 is connected to one end of the detection resistor R6 and the drain of the first field effect transistor M1, the base of the second transistor Q2 is connected to the other end of the detection resistor R6, the other end of the detection resistor R6 is also connected to the load, the collector of the second transistor Q2 is connected to one end of the fifth resistor R5, one end of the fifth resistor R5 is also connected to the fourth resistor R4, and the other end of the fifth resistor R5 is connected to the ground line.

[0018] The latch unit includes a third triode Q3 and a fourth triode Q4, the base of the third triode Q3 is connected to the collector of the first triode Q1 and the gate of the second field effect transistor M2, the emitter of the third triode Q3 is connected to the power line through the sixth resistor R6, the collector of the third triode Q3 is connected to the ground line through the seventh resistor R7, the base of the fourth triode Q4 is connected to the collector of the third triode Q3, the emitter of the fourth triode Q4 is connected to the ground line, and the collector of the fourth triode Q4 is connected to the base of the third triode Q3.

[0019] The filtering unit provided in the present invention includes a filtering inductor L1, one end of the filtering inductor L1 is connected to the power supply V1, the other end of the filtering inductor L1 is connected to the source of the first field effect transistor M1, one end of the filtering inductor L1 is connected to the ground wire through the first capacitor C1, and the other end of the filtering inductor L1 is connected to the ground wire through the second capacitor C2; through the setting of the filtering unit, the power supply voltage can be optimized and stabilized, the quality of the power supply can be effectively improved, and the voltage output can be more stable, thereby reducing the current fluctuation in the load circuit connected to the main control circuit under normal working conditions, thereby improving the reliability of the current detection module.

[0020] The working principle of the present invention is: in the initial normal working state, the current of the load circuit is normal, the voltage of the detection resistor R6 is small, so that the second diode is in the cut-off state, at this time, the first transistor Q1 is directly connected to the ground line through the fourth resistor R4 and the fifth resistor R5, and the first transistor Q1 is also in the cut-off state. At the same time, the base of the third transistor Q3 is connected to the power line through the third resistor R3, and the emitter is connected to the power line through the sixth resistor R6. Therefore, the third transistor Q3 is in the cut-off state, and the base of the fourth resistor R4 is connected to the ground line through the seventh resistor R7, and is also in the cut-off state.

[0021] In the initial state, the gate of the second field effect transistor M2 is connected to the power line through the third resistor R3, and the voltage is pulled up to the power supply voltage. The gate-source voltage of the second field effect transistor M2 is greater than the gate-source threshold voltage, so the drain and source of the second field effect transistor M2 are turned on; at the same time, the first resistor R1 and the second resistor R2 perform voltage division, and the voltage of the first resistor R1 after voltage division acts on the gate of the first field effect transistor M1, and is greater than the gate-source threshold voltage of the first field effect transistor M1, so that the drain and source of the first field effect transistor M1 are turned on, and the power line outputs voltage to the outside through the source and drain of the first field effect transistor M1.

[0022] When the load line is short-circuited to ground or equipment fails, that is, the current in the load line increases rapidly, the voltage drop across the detection resistor R6 increases, and the voltage acting on the emitter and base of the second transistor Q2 increases. When the voltage drop is greater than 0.7V, the second transistor Q2 enters the saturation region and turns on after a reaction time. At this time, the voltage across the fifth resistor R5 is approximately equal to the power supply voltage; at this time, the base voltage of the first transistor Q1 connected to the fifth resistor R5 through the fourth resistor R4 increases, and at this time, the Vbe of the first transistor Q1 will reach 0.7V, and the first transistor Q1 will enter the saturation region. At this time, the first transistor Q1 is turned on, and the gate of the second field effect transistor M2 will be pulled down to the ground, so that the second field effect transistor M2 enters the cut-off region. When the first transistor Q1 is turned on, the latch unit works, that is, the base of the third transistor Q3 is connected to the ground line, and the voltage is pulled down to the ground. At this time, the emitter of the third transistor Q3 is connected to the power line through the sixth resistor R6, so that the third transistor Q3 enters the saturation region and is turned on. At the same time, due to the voltage division of the sixth resistor R6 and the seventh resistor R7, the base voltage of the fourth transistor Q4 increases, thereby driving the fourth transistor Q4 to be turned on. When the second field effect transistor M2 enters the cut-off state, the first field effect transistor M1 also enters the cut-off state. At this time, the current load in the load line drops rapidly to zero, and the voltage drop across the detection resistor R6 decreases, causing the second transistor Q2 to enter the cut-off state, and then causing the base of the first transistor Q1 to be pulled down to ground through the fourth resistor R4 and the fifth resistor R5, and the first transistor Q1 enters the cut-off state; due to the response of the latch unit, at this time, the base of the third transistor Q3 is kept grounded through the collector and emitter of the fourth transistor Q4, and the emitter of the third transistor Q3 is connected to the power line through the sixth resistor R6, thereby ensuring the conduction of the third transistor Q3. At the same time, the conduction of the third transistor Q3 ensures the conduction of the fourth transistor Q4, that is, the mutual interaction realizes the automatic latching of the signal, thereby reliably ensuring that the gate of the second field effect transistor M2 is connected to the ground line, so that the first field effect transistor M1 is reliably disconnected, and overcurrent protection is realized.

[0023] The above-mentioned embodiments are only preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. An overcurrent protection circuit with automatic latching function, characterized in that: The invention comprises a feedback control module, a main switch module and a current detection module connected in sequence, wherein the filter unit is connected to the power supply to filter out the input power supply noise and output the filtered electric energy to the main switch module, and provide a stable voltage for the load, the feedback control module is used to receive the signal of the current detection module and control the on-off of the main switch module, the main switch module is connected to the power supply and supplies power to the load line where the current detection module is located, and the main switch module controls the on-off of the power supply, the current detection module is used to detect the current of the load line and transmit the signal to the feedback control module, and a latch unit is also arranged between the feedback control module and the main switch, and the latch unit is used to latch the control signal output by the current detection module to the feedback control module; the power supply comprises a power line connected to the positive electrode and a ground line connected to the negative electrode, the main switch comprises a first field effect transistor and a second field effect transistor, the source of the first field effect transistor is connected to the power line, the gate of the first field effect transistor is connected to one end of the first resistor and one end of the second resistor, the other end of the first resistor is connected to the power supply, and the second The other end of the resistor is connected to the drain of the second field effect tube, the source of the second field effect tube is connected to the ground line, the gate of the second field effect tube is connected to the feedback control module, and the drain of the first field effect tube is connected to the current detection module; the feedback control module includes a first triode, the collector of the first triode is connected to the gate of the second field effect tube, the emitter of the first triode is connected to the ground line, the collector of the first triode is also connected to the power line through the third resistor, and the base of the first triode is connected to the ground line. The latch unit includes a third triode and a fourth triode, the base of the third triode is connected to the collector of the first triode and the gate of the second field effect tube, the emitter of the third triode is connected to the power line through the sixth resistor, the collector of the third triode is connected to the ground line through the seventh resistor, the base of the fourth triode is connected to the collector of the third triode, the emitter of the fourth triode is connected to the ground line, and the collector of the fourth triode is connected to the base of the third triode.

2. An overcurrent protection circuit with automatic latching function according to claim 1, characterized in that: The current detection module includes a detection resistor and a second transistor, the emitter of the second transistor is connected to one end of the detection resistor and the drain of the first field effect transistor, the base of the second transistor is connected to the other end of the detection resistor, the other end of the detection resistor is also connected to the load, the collector of the second transistor is connected to one end of the fifth resistor, one end of the fifth resistor is also connected to the fourth resistor, and the other end of the fifth resistor is connected to the ground wire.

3. The overcurrent protection circuit with automatic latching function according to claim 2, characterized in that: The filtering unit includes a filtering inductor, one end of which is connected to a power supply, the other end of which is connected to a source of a first field effect transistor, one end of which is connected to a grounding wire via a first capacitor, and the other end of which is connected to a grounding wire via a second capacitor.

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