Short-circuit protection circuit

Abstract

The utility model discloses a short circuit protection circuit in the technical field of power supply protection, which comprises an auxiliary power supply circuit, the auxiliary power supply circuit is connected with a sampling circuit and a locking protection circuit, and the sampling circuit is connected with the locking protection circuit. The auxiliary power supply circuit supplies power to the other circuits and also provides reference voltage for the sampling circuit, the sampling circuit is used for collecting current signals in the circuits and providing overcurrent protection signals for the locking protection circuit, and the locking protection circuit is in an alternating circulation from conduction to protection until faults are removed. Therefore, the power supply bus is protected when a short circuit is caused by a fault of a certain branch, normal work of other branches is ensured, the capability of supplying power to load equipment can be automatically recovered after the short circuit fault is eliminated, and the reliability and the safety of system power supply are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to short circuit protection circuit in the power supply protection technical field. BACKGROUND

[0002] With the diversification of electric equipment, the power supply branch is more and more, usually by several power supply branches share an input bus, any one power supply branch on the electric equipment end caused short circuit fault often will lead to bus power supply abnormality, thereby influence all equipment's normal use. UTILITY MODEL CONTENTS

[0003] The utility model discloses a kind of short circuit protection circuits, protect power supply bus when the short circuit caused by certain branch fault, guarantee other branch normal work and the ability of automatically recovering to load equipment power supply after short circuit fault elimination, improve the reliability and safety of system power supply.

[0004] To achieve the above object, the utility model provides a kind of short circuit protection circuit, including auxiliary power supply circuit, auxiliary power supply circuit is connected with sampling circuit and lock protection circuit, sampling circuit is connected with lock protection circuit.

[0005] Compared with prior art, the utility model has the beneficial effect that auxiliary power supply circuit is powered for other several circuits and also provides reference voltage for sampling circuit, sampling circuit is used to collect current signal in circuit, provides overcurrent protection signal for lock protection circuit, from on to protection alternation in the cycle of lock protection circuit, until fault elimination, so that in the short circuit caused by certain branch fault, protect power supply bus, guarantee other branch normal work and the ability of automatically recovering to load equipment power supply after short circuit fault elimination, improve the reliability and safety of system power supply.

[0006] As a further improvement of the utility model, the auxiliary power supply circuit includes a three-terminal voltage regulator U1, the 1 pin of the three-terminal voltage regulator U1 is connected with the positive pole of input voltage and one end of capacitor C2 respectively, the 3 pin of the three-terminal voltage regulator U1 is connected with the other end of capacitor C2 and grounded, the 2 pin of the three-terminal voltage regulator U1 is connected with one end of capacitor C3 and one end of resistor R5 respectively, the other end of capacitor C3 is connected with the 3 pin of the three-terminal voltage regulator U1, the other end of resistor R5 is connected with the cathode and control electrode of thyristor U2, the anode of thyristor U2 is connected with the other end of capacitor C3.

[0007] In this way, the three-terminal voltage regulator circuit is used to realize stable power supply, and is used for power supply of the sampling circuit and the lock protection circuit.

[0008] As a further improvement of the utility model, the sampling circuit comparator A1, the 1 pin of the comparator A1 is connected with one end of resistor R6, the other end of resistor R6 is connected with the 8 pin of the comparator A1 and the 2 pin of the three-terminal voltage regulator U1 respectively, the 3 pin of the comparator A1 is connected with one end of resistor R7 and grounded, the other end of resistor R7 is connected with one end of resistor R12 and the 4 pin of the comparator A1 respectively, one end of resistor R12 is connected with the negative pole of input voltage, the other end of resistor R12 is connected with one end of resistor R11 and the 2 pin of the comparator A1 respectively, the other end of resistor R11 is connected with the other end of resistor R5.

[0009] In this way, under normal load condition, the voltage divided by R11 and R12 is positive, the reverse end voltage of the comparator A1 is zero, and the output of the comparator A1 is low level; when short circuit output overcurrent occurs, the voltage drop on the sampling resistor R7 increases, the voltage value of the reverse end of the comparator A1 decreases, when the voltage value of the reverse end of the comparator A1 drops to 0V, the comparator A1 outputs an overcurrent protection signal QH.

[0010] As a further improvement of the utility model, the electric lock protection circuit includes a monostable trigger U3, the 1 pin of the monostable trigger U3 is connected with one end of capacitor C4, the other end of capacitor C4 is connected with the 2 pin of the monostable trigger U3 and one end of resistor R13 respectively, the other end of resistor R13 is connected with the 2 pin of the three-terminal voltage regulator U1 and the 16 pin of the monostable trigger U3 respectively, the 3 pin, 5 pin and 13 pin of the monostable trigger U3 are connected, the 4 pin of the monostable trigger U3 is connected with the 1 pin of the comparator A1, the 6 pin and 11 pin of the monostable trigger U3 are connected, the 8 pin and 12 pin of the monostable trigger U3 are connected and grounded, the 14 pin of the monostable trigger U3 is connected with one end of capacitor C5 and one end of resistor R14 respectively, the other end of resistor R14 is connected with the 16 pin of the monostable trigger U3, the other end of capacitor C5 is connected with the 15 pin of the monostable trigger U3.

[0011] Pin 10 of the monostable multivibrator U3 is connected to one end of resistor R2 and one end of resistor R1. The other end of resistor R1 is connected to the negative terminal of the power supply. The other end of resistor R2 is connected to the gate (G) of MOSFET Q2. The source (S) of MOSFET Q2 is connected to the other end of resistor R1. The drain (D) of MOSFET Q2 is connected to one end of capacitor C1. One end of capacitor C1 is connected to one end of resistor R4 and one end of resistor R3. The other end of capacitor C1 is connected to the source (S) of MOSFET Q2 and the other end of resistor R4. The other end of resistor R3 is connected to the positive terminal of the power supply and the positive terminal of the device. One end of resistor R4 is also connected to the gate (G) of MOSFET Q1. The source (S) of MOSFET Q1 is connected to the other end of resistor R4. The drain (D) of MOSFET Q1 is connected to the negative terminal of the device.

[0012] When a short circuit fault occurs in the circuit of this branch, the sampling circuit outputs an overcurrent signal QH at a high level, Q2 is turned on, the gate of Q1 is grounded through Q2, Q1 is turned off, the protection lockout circuit sets the gate of Q1 to a low level and holds it for a period of time, which is the protection action lockout time; after the lockout time ends, the protection lockout circuit releases the gate of Q1, Q1 is turned on again, and the circuit restarts. If the load that caused the overcurrent fault is always in the circuit, then Q1 will be in a cycle of alternating between being turned on and being protected. Attached Figure Description

[0013] Figure 1 This is the circuit diagram of the auxiliary power supply for this utility model.

[0014] Figure 2 This is the sampling circuit diagram of this utility model.

[0015] Figure 3 This is the circuit diagram for the locking protection of this utility model. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings:

[0017] like Figures 1-3 The short-circuit protection circuit shown includes an auxiliary power supply circuit, which is connected to a sampling circuit and a locking protection circuit. The sampling circuit is connected to the locking protection circuit.

[0018] The auxiliary power supply circuit includes a three-terminal voltage regulator U1. Pin 1 of the three-terminal voltage regulator U1 is connected to the positive terminal of the input voltage and one end of capacitor C2. Pin 3 of the three-terminal voltage regulator U1 is connected to the other end of capacitor C2 and grounded. Pin 2 of the three-terminal voltage regulator U1 is connected to one end of capacitor C3 and one end of resistor R5. The other end of capacitor C3 is connected to pin 3 of the three-terminal voltage regulator U1. The other end of resistor R5 is connected to the cathode and control electrode of thyristor U2. The anode of thyristor U2 is connected to the other end of capacitor C3.

[0019] The sampling circuit comparator A1, the 1 pin of comparator A1 is connected with one end of resistor R6, the other end of resistor R6 is connected with the 8 pin of comparator A1 and the 2 pin of three-terminal voltage regulator U1 respectively, the 3 pin of comparator A1 is connected with one end of resistor R7 and grounded, the other end of resistor R7 is connected with one end of resistor R12 and the 4 pin of comparator A1 respectively, one end of resistor R12 is connected with the negative pole of input voltage, the other end of resistor R12 is connected with one end of resistor R11 and the 2 pin of comparator A1 respectively, the other end of resistor R11 is connected with the other end of resistor R5.

[0020] The electric lock protection circuit comprises a monostable trigger U3, the 1 pin of monostable trigger U3 is connected with one end of capacitor C4, the other end of capacitor C4 is connected with the 2 pin of monostable trigger U3 and one end of resistor R13 respectively, the other end of resistor R13 is connected with the 2 pin of three-terminal voltage regulator U1 and the 16 pin of monostable trigger U3 respectively, the 3 pin, 5 pin and 13 pin of monostable trigger U3 are connected, the 4 pin of monostable trigger U3 is connected with the 1 pin of comparator A1, the 6 pin and 11 pin of monostable trigger U3 are connected, the 8 pin and 12 pin of monostable trigger U3 are connected and grounded, the 14 pin of monostable trigger U3 is connected with one end of capacitor C5 and one end of resistor R14 respectively, the other end of resistor R14 is connected with the 16 pin of monostable trigger U3, the other end of capacitor C5 is connected with the 15 pin of monostable trigger U3.

[0021] The 10 pin of monostable trigger U3 is connected with one end of resistor R2 and one end of resistor R1 respectively, the other end of resistor R1 is connected with the negative pole of power supply, the other end of resistor R2 is connected with the G pole of MOS tube Q2, the S pole of MOS tube Q2 is connected with the other end of resistor R1, the D pole of MOS tube Q2 is connected with one end of capacitor C1, one end of capacitor C1 is connected with one end of resistor R4 and one end of resistor R3 respectively, the other end of capacitor C1 is connected with the S pole of MOS tube Q2 and the other end of resistor R4 respectively, the other end of resistor R3 is connected with the positive pole of power supply and the positive pole of electric equipment respectively, one end of resistor R4 is also connected with the G pole of MOS tube Q1, the S pole of MOS tube Q1 is connected with the other end of resistor R4, the D pole of MOS tube Q1 is connected with the negative pole of electric equipment.

[0022] In the utility model, the whole circuit is arranged between the initial section of branch circuit and electric equipment, wherein the auxiliary power supply circuit is as shown in the figure, three-terminal voltage regulation circuit is adopted to realize stable power supply, and is used for power supply of sampling circuit and lock protection circuit. Figure 1 In addition, the three-terminal voltage regulator also provides reference voltage Vref

[0023] The sampling circuit is as shown in the figure. Figure 2As shown, in the normal load condition, the voltage divided by R11 and R12 is positive, the reverse terminal voltage of comparator A1 is zero, and the output of comparator A1 is low; when short circuit overcurrent occurs, the voltage drop on sampling resistor R7 increases, the voltage value of the reverse terminal of comparator A1 decreases, and when the voltage value of the reverse terminal of comparator A1 drops to 0V, the overcurrent protection signal QH of comparator A1 is output.

[0024] The protection lock circuit is as shown in Figure 3 As shown, the monostable trigger U3 is CD4098, which has the characteristic that under the triggering of an input pulse, a rectangular pulse with constant width is generated at its output, and this state is temporarily stable, and returns to the initial state after a time t. The time t is adjusted by external resistors R13 and R14 and external capacitors C5 and C4. The pulse widening circuit obtained by the monostable trigger U3 widens the narrow pulse of the overcurrent signal, locks off the time of MOS transistor Q1, avoids the overcurrent protection frequency being too high when the overcurrent protection is turned on, and prevents the MOS transistor Q1 from being damaged by overheating. Moreover, since it returns to the initial state after a time t, the protection is recoverable.

[0025] In operation, when the sampling circuit obtains the overcurrent protection signal QH, the QH signal is output as QH1 after passing through the monostable trigger U3, and QH1 is the widened wave of QH. Since the load needs to be disconnected from the bus during overcurrent, i.e. the MOS transistor Q1 needs to be turned off, the gate voltage of the MOS transistor Q1 needs to be adjusted to be low, and the overcurrent protection signal needs to be inverted before being used to control the MOS transistor Q1. The overcurrent signal control logic can be inverted through the MOS transistor Q2. When the electrical equipment is working normally, the sampling circuit outputs a low-level signal QH, Q1 is turned on, and the power supply circuit normally provides voltage for the subsequent circuit. When the subsequent circuit has a short circuit fault, the sampling circuit outputs a high-level overcurrent signal QH, MOS transistor Q2 is turned on, the gate of MOS transistor Q1 is grounded through MOS transistor Q2, MOS transistor Q1 is cut off, and the protection lock circuit sets the gate of MOS transistor Q1 to be low and maintains for a period of time, which is the protection action lock time. After the lock time ends, the protection lock circuit releases the gate of MOS transistor Q1, and MOS transistor Q1 is turned on again, and the circuit is started again. If the load that causes the overcurrent fault is directly in the circuit, then MOS transistor Q1 will be in a cycle of being turned on and protection, so that the branch will not affect the power supply bus when a short circuit fault occurs, thereby ensuring that other branches work normally, and the ability to supply power to the load equipment of the branch can be automatically restored after the short circuit fault is eliminated.

[0026] The utility model discloses not limited to the above embodiment, on the basis of the technical scheme of the present disclosure, the technical personnel in the art can make some replacement and deformation to some technical features in it according to the disclosed technical content without creative labor, and these replacement and deformation are all within the protection scope of the utility model.

Claims

1. A short circuit protection circuit, characterized by: The auxiliary power supply circuit is connected with the sampling circuit and the lock protection circuit; The auxiliary power supply circuit comprises a three-terminal voltage regulator U1, a pin 1 of the three-terminal voltage regulator U1 is connected with a positive pole of an input voltage and one end of a capacitor C2, a pin 3 of the three-terminal voltage regulator U1 and the other end of the capacitor C2 are connected and grounded, a pin 2 of the three-terminal voltage regulator U1 is connected with one end of a capacitor C3 and one end of a resistor R5, the other end of the capacitor C3 is connected with the pin 3 of the three-terminal voltage regulator U1, the other end of the resistor R5 is connected with a cathode and a control electrode of a thyristor U2, an anode of the thyristor U2 is connected with the other end of the capacitor C3; The sampling circuit comprises a comparator A1, a pin 1 of the comparator A1 is connected with one end of a resistor R6, the other end of the resistor R6 is connected with a pin 8 of the comparator A1 and a pin 2 of the three-terminal voltage regulator U1, a pin 3 of the comparator A1 is connected with one end of a resistor R7 and grounded, the other end of the resistor R7 is connected with one end of a resistor R12 and a pin 4 of the comparator A1, one end of the resistor R12 is connected with a negative pole of the input voltage, the other end of the resistor R12 is connected with one end of a resistor R11 and a pin 2 of the comparator A1, the other end of the resistor R11 is connected with the other end of the resistor R5; The lock protection circuit comprises a monostable trigger U3, one end of a capacitor C4 is connected with a pin 1 of the monostable trigger U3, the other end of the capacitor C4 is connected with a pin 2 of the monostable trigger U3 and one end of a resistor R13, the other end of the resistor R13 is connected with the pin 2 of the three-terminal voltage regulator U1 and a pin 16 of the monostable trigger U3, a pin 3, a pin 5 and a pin 13 of the monostable trigger U3 are connected, a pin 4 of the monostable trigger U3 is connected with the pin 1 of the comparator A1, a pin 6 and a pin 11 of the monostable trigger U3 are connected, a pin 8 and a pin 12 of the monostable trigger U3 are connected and grounded, one end of a capacitor C5 and one end of a resistor R14 are connected with a pin 14 of the monostable trigger U3, the other end of the resistor R14 is connected with the pin 16 of the monostable trigger U3, the other end of the capacitor C5 is connected with a pin 15 of the monostable trigger U3; A pin 10 of the monostable trigger U3 is connected with one end of a resistor R2 and one end of a resistor R1, the other end of the resistor R1 is connected with a negative pole of a power supply, the other end of the resistor R2 is connected with a G electrode of a MOS tube Q2, an S electrode of the MOS tube Q2 is connected with the other end of the resistor R1, a D electrode of the MOS tube Q2 is connected with one end of a capacitor C1, one end of the capacitor C1 is connected with one end of a resistor R4 and one end of a resistor R3, the other end of the capacitor C1 is connected with the S electrode of the MOS tube Q2 and the other end of the resistor R4, the other end of the resistor R3 is connected with a positive pole of the power supply and a positive pole of an electrical equipment, one end of the resistor R4 is also connected with a G electrode of a MOS tube Q1, an S electrode of the MOS tube Q1 is connected with the other end of the resistor R4, a D electrode of the MOS tube Q1 is connected with a negative pole of the electrical equipment.

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