A discharge circuit

Abstract

The present invention proposes a discharge circuit, which is coupled between an input power supply and a load unit; the discharge circuit includes a switch unit, a signal capture unit and a discharge unit for discharging residual charge in the discharge circuit; the switch unit is connected in series between the input power supply and the load unit, and one end of the load unit is grounded. The signal capture unit at least includes an amplifier circuit, which is used to capture the change of the signal of the circuit in the switch switching state by using the amplifier circuit, and send the signal to the discharge unit after processing. The discharge circuit of the present invention consumes very little energy after the circuit is powered on, and there will be no situation where the greater the current in the circuit, the greater the loss; at the same time, it can be selected according to the actual situation to be pure resistance discharge or constant current circuit discharge. The pure resistance circuit is simple, uses fewer devices, and has low cost. The constant current circuit has a stable discharge and will not have the risk of sudden large current causing device damage.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a discharge circuit. Background Art

[0002] When the circuit is disconnected, the circuit needs to be able to release the accumulated charge in a short time, otherwise people may accidentally touch the circuit and get an electric shock. Especially for circuits with very large capacitive loads, such as switching voltage regulator circuits, these circuits often have large capacitance capacitors. If these capacitors are not discharged, the charge will continue to accumulate on the circuit board. If the load on the circuit board is the only one to discharge the charge, it may take hours or even days, which will leave a great safety hazard. Therefore, it is particularly important to add a discharge circuit to the circuit to discharge the remaining charge in the disconnected circuit in a short time, thereby protecting the safety of personnel.

[0003] In addition, when the switch is turned off, the voltage generated by the residual charge in the circuit is unstable. Therefore, adding a single-chip microcomputer, integrated circuit chip and other devices that require a stable voltage to work in the circuit will not be able to play a control role. The control part of the discharge circuit cannot use such devices that require a stable voltage to work. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a discharge circuit which can quickly release the residual charge in the circuit after the switch is disconnected.

[0005] In order to solve the above technical problems, the present invention provides a discharge circuit coupled between an input power source and a load unit; the discharge circuit comprises:

[0006] A switch unit having a first terminal and a second terminal, wherein the first terminal of the switch unit is connected to the positive electrode of the input power supply, the second terminal of the switch unit is connected to one end of the load unit, and the other end of the load unit is connected to the negative electrode of the input power supply and then grounded. In addition, it also includes a signal capturing unit and a discharge unit; the signal capturing unit at least includes an amplifying circuit, which is used to capture the change of the signal of the circuit in the switch switching state by using the amplifying circuit, and send the signal to the discharge unit after processing; the discharge unit is used to discharge the residual charge in the circuit.

[0007] In some feasible implementations, the signal capture unit includes an amplifier circuit consisting of an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a first voltage regulator diode, wherein:

[0008] The negative power supply pin of the operational amplifier is grounded, the positive power supply pin is connected to the second terminal of the switch unit, the in-phase input terminal is connected in series with the third resistor and then connected to the ground, the inverting input terminal is connected in series with the fourth resistor and then connected to the output terminal of the operational amplifier, one end of the first resistor is connected to the in-phase input terminal of the operational amplifier, and the other end is connected to the first terminal of the switch unit, one end of the second resistor is connected to the inverting input terminal of the operational amplifier, and the other end is connected to the second terminal of the switch unit, one end of the fifth resistor is connected to the output terminal of the operational amplifier, and the other end is connected to the cathode of the first voltage regulator diode, and the anode of the first voltage regulator diode is grounded; the fifth resistor and the first voltage regulator diode D1 constitute a voltage regulator circuit, wherein the stable voltage V of the first voltage regulator diode D1 is Z The threshold voltage V of the first MOS tube GS(th) The following relationship needs to be satisfied:

[0009] V Z ≥V GS(th)

[0010] The operational amplifier, the first resistor, the second resistor, the third resistor, and the fourth resistor in the signal capture unit form a differential amplifier circuit, and the output voltage of the differential amplifier is

[0011]

[0012] In the formula, U1 is the voltage at the first terminal of the switch unit 1, U2 is the voltage at the first terminal of the switch unit 2, R1, R2, R3, R4 are the resistance value of the first resistor, the resistance value of the second resistor, the resistance value of the third resistor, and the resistance value of the fourth resistor, respectively. The common node of the first voltage zener diode and the fifth resistor is the output end of the signal capture unit.

[0013] In some feasible implementations, the signal capture unit specifically includes an amplifier circuit consisting of an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, and a tenth resistor, wherein:

[0014] One end of the first capacitor is connected to the first terminal of the switch unit, and the other end is connected in series with the tenth resistor and then connected to the second terminal of the switch unit. The negative power supply pin of the operational amplifier is grounded, and the positive power supply pin is connected to the second terminal of the switch unit. The in-phase input end is connected in series with the third resistor and then connected to the ground. The inverting input end is connected in series with the fourth resistor and then connected to the output end of the operational amplifier. One end of the second resistor is connected to the in-phase input end of the operational amplifier, and the other end is connected to the common node of the first capacitor and the tenth resistor. One end of the first resistor is connected to the second terminal of the switch unit, and the other end is connected to the inverting input end of the operational amplifier. The output end of the operational amplifier is the output end of the signal capture unit.

[0015] In some feasible embodiments, the discharge unit includes a first MOS tube and a sixth resistor; wherein one end of the sixth resistor is connected to the second terminal of the switch unit, and the other end is connected to the drain of the first MOS tube, the gate of the first MOS tube is connected to the output end of the signal capture unit, and its source is grounded.

[0016] In some feasible implementations, the discharge unit includes a third MOS tube and a constant current circuit, and the constant current circuit discharges the charge in the circuit with a constant current magnitude.

[0017] In some feasible embodiments, the constant current circuit includes a seventh resistor, an eighth resistor, a ninth resistor, a second diode, a third diode, a second bipolar transistor, and a third MOS tube, wherein one end of the seventh resistor is connected to the second terminal of the switch unit, and the other end is connected to the base of the second bipolar transistor, one end of the eighth resistor is connected to the second terminal of the switch unit, and the other end is connected to the collector of the second bipolar transistor, one end of the ninth resistor is connected to the emitter of the second bipolar transistor, and the other end is connected to the drain of the third MOS tube, the anode of the second diode is connected to the base of the second bipolar transistor, and the cathode is connected to the anode of the third diode, the cathode of the third diode is connected to the drain of the third MOS tube, the source of the third MOS tube is grounded, and its gate is connected to the output end of the signal capture unit.

[0018] In some feasible implementations, the MOS transistor is an N-channel enhancement mode MOS transistor.

[0019] The beneficial effects of the present invention are: 1) The discharge circuit of the present invention consumes very little energy after the circuit is powered on, and there will be no situation where the greater the current in the circuit, the greater the loss; 2) The discharge unit in the present invention can be selected as pure resistance discharge or constant current circuit discharge according to actual conditions. The pure resistance circuit is simple, uses fewer devices, and has low cost. The constant current circuit has stable discharge and there is no risk of sudden large current causing damage to the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a functional schematic diagram of a first embodiment of the discharge circuit of the present invention.

[0021] Figure 2 It is a circuit connection diagram of a second embodiment of the discharge circuit of the present invention.

[0022] Figure 3 It is a functional schematic diagram of a third embodiment of the discharge circuit of the present invention.

[0023] Figure 4 It is a circuit connection diagram of a fourth embodiment of the discharge circuit of the present invention.

[0024] Figure 5 It is a circuit connection diagram of a fifth embodiment of the discharge circuit of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] Combination Figure 1 , a first embodiment of the discharge circuit of the present invention, the discharge circuit is coupled between the input power supply 1 and the load unit 5; the discharge circuit specifically includes:

[0027] A switch unit 2 having a first terminal and a second terminal, a signal capture unit 3 and a discharge unit 4; wherein the first terminal of the switch unit 2 is connected to the positive electrode of the input power supply 1, the second terminal of the switch unit 2 is connected to one end of the load unit 5, and the other end of the load unit 5 is connected to the negative electrode of the input power supply 1 and then grounded. The signal capture unit 3 controls the switch of the discharge unit 4 according to the on and off of the switch unit 2. When the signal capture unit 3 detects that the switch unit 2 is disconnected, the signal capture unit 3 will turn on the discharge unit 4. At this time, the discharge unit 4 will start to discharge the residual charge in the circuit. When the switch unit 2 is closed, the signal capture unit 3 will turn off the discharge unit 4.

[0028] When the switch unit 2 is closed, the circuit works normally. At this time, since the switch unit 2 is not detected to be disconnected, the signal capture unit 3 will not open the discharge unit 4 for discharge; when the switch unit 2 is disconnected, the circuit no longer works. At this time, the signal capture unit 3 detects that the switch unit 2 is disconnected, and the signal capture unit 3 will open the discharge unit 4 for discharge.

[0029] Figure 2 It is a second embodiment of the discharge circuit of the present invention, wherein the signal capture unit 3 includes an operational amplifier, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a first voltage-stabilizing diode D1, wherein: the negative power supply pin of the operational amplifier is grounded, the positive power supply pin is connected to the second terminal of the switch unit 2, the in-phase input terminal is connected in series with the third resistor R3 and then grounded, the inverting input terminal is connected in series with the fourth resistor R4 and then connected to the output terminal of the operational amplifier, one end of the first resistor R1 is connected to the in-phase input terminal of the operational amplifier, and the other end is connected to the first terminal of the switch unit 2, one end of the second resistor R2 is connected to the inverting input terminal of the operational amplifier, and the other end is connected to the second terminal of the switch unit 2, one end of the fifth resistor R5 is connected to the output terminal of the operational amplifier, and the other end is connected to the cathode of the first voltage-stabilizing diode D1, and the anode of the first voltage-stabilizing diode D1 is grounded. The discharge unit 4 includes a first MOS transistor Q1 and a sixth resistor R6; wherein one end of the sixth resistor R6 is connected to the second terminal of the switch unit 2, and the other end is connected to the drain of the first MOS transistor Q1, the gate of the first MOS transistor Q1 is connected to the common node of the first voltage stabilizing diode D1 and the fifth resistor R5, and the source thereof is grounded. The first MOS transistor is an N-channel enhancement type MOS transistor.

[0030] The fifth resistor R5 and the first voltage stabilizing diode D1 form a voltage stabilizing circuit, wherein the stabilizing voltage V Z The threshold voltage V GS(th) The following relationship needs to be satisfied:

[0031] V Z ≥V GS(th)

[0032] The operational amplifier in the signal capture unit 3, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 form a differential amplifier circuit, whose output voltage is

[0033]

[0034] Wherein, U1 is the voltage at the first terminal of the switch unit 2, and U2 is the voltage at the second terminal of the switch unit 2.

[0035] When the resistance of the first resistor R1 is equal to the resistance of the second resistor R2, and the resistance of the third resistor R3 is equal to the resistance of the fourth resistor R4, the above formula can be simplified to:

[0036]

[0037] When the switch unit 2 is closed, the circuit works normally. At this time, the voltage drop on both sides of the switch unit 2 is almost 0V, and the output voltage of the operational amplifier is about 0V. At this time, the first MOS tube Q1 is turned off, and the discharge unit 4 does not work; when the switch unit 2 is disconnected, the circuit no longer works, and the voltage at the second terminal of the switch unit 2 decreases due to the load in the circuit, which slowly releases the charge, but the voltage at the first terminal of the switch unit 2 remains unchanged. In this way, the voltage difference ΔU between the first terminal and the second terminal will gradually increase, and the differential amplifier circuit outputs a voltage V OUT will also gradually increase until it reaches the threshold voltage of the first MOS tube Q1. At this time, the discharge unit 4 is turned on and starts to discharge the residual charge. OUT The fifth resistor R5 and the first voltage regulator diode D1 are added to the output end of the operational amplifier so that the gate voltage of the first MOS tube Q1 does not exceed the voltage regulator value of the voltage regulator diode D1. As the charge is gradually released, the voltage at the second terminal of the switch unit 2 will drop, which also means that the voltage at the positive power supply pin of the operational amplifier will also drop. Due to the characteristics of the operational amplifier, its output voltage V OUT Saturation occurs, and the output voltage V OUT It will also decrease with the decrease of the voltage at the second terminal of the switch unit 2 until the gate voltage of the first MOS transistor Q1 is less than its threshold voltage and the first MOS transistor Q1 is turned off. At this time, most of the residual charge in the circuit has been released and will not cause harm to personnel and equipment.

[0038] Figure 3 This is the third embodiment of the discharge circuit of the present invention, wherein the discharge unit 4 is composed of a third MOS tube and a constant current circuit 41, and the constant current circuit 41 discharges the charge in the circuit with a constant current. When the signal capture unit 3 detects that the switch unit 2 is disconnected, the signal capture unit 3 will turn on the discharge unit 4 including the constant current circuit 41, so that the residual charge in the circuit can be discharged with a constant current.

[0039] Figure 4It is the fourth embodiment of the discharge circuit of the present invention, wherein the constant current circuit 41 specifically includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a second diode D2, a third diode D3, a second bipolar transistor Q2, and a third MOS tube Q3, wherein one end of the seventh resistor R7 is connected to the second terminal of the switch unit 2, and the other end is connected to the base of the second bipolar transistor Q2, one end of the eighth resistor R8 is connected to the second terminal of the switch unit 2, and the other end is connected to the collector of the second bipolar transistor Q2, one end of the ninth resistor R9 is connected to the emitter of the second bipolar transistor Q2, and the other end is connected to the drain of the third MOS tube Q3, the anode of the second diode D2 is connected to the base of the second bipolar transistor Q2, and the cathode is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the drain of the third MOS tube Q3, the source of the third MOS tube Q3 is grounded, and its gate is connected to the cathode of the first voltage stabilizing diode D1. On the basis of the previous embodiment, the discharge unit 4 is improved, and the constant current circuit 41 is added.

[0040] The seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the second diode D2, the third diode D3, and the second bipolar transistor Q2 in the discharge unit 4 together form a constant current source circuit. When the third MOS tube Q3 is turned on and the discharge unit 4 is working, the constant current source circuit will generate a constant current I C Discharge residual current, the current I C Size is about

[0041]

[0042] Where V F2 With V F3 are the forward voltage drops of the second diode D2 and the third diode D3, V be is the turn-on voltage of the second bipolar transistor Q2.

[0043] Therefore, the constant current circuit 41 can discharge the residual charge at a constant current when the discharge unit 4 is turned on.

[0044] Figure 5It is a fifth embodiment of the discharge circuit of the present invention, wherein the signal capture unit 3 specifically includes an operational amplifier, a first capacitor C1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a tenth resistor R10, wherein one end of the first capacitor C1 is connected to the first terminal of the switch unit 2, and the other end is connected in series with the tenth resistor R10 and then connected to the second terminal of the switch unit 2, the negative power supply pin of the operational amplifier is grounded, the positive power supply pin is connected to the second terminal of the switch unit 2, the in-phase input end is connected in series with the third resistor R3 and then grounded, the inverting input end is connected in series with the fourth resistor R4 and then connected to the output end of the operational amplifier, one end of the second resistor R2 is connected to the in-phase input end of the operational amplifier, and the other end is connected to the common node of the first capacitor C1 and the tenth resistor R10, one end of the first resistor R1 is connected to the second terminal of the switch unit 2, and the other end is connected to the inverting input end of the operational amplifier.

[0045] When the switch unit 2 is disconnected, the first capacitor C1 is DC Charging starts through the tenth resistor R10 and the load resistor R. At this time, the voltage difference V on the tenth resistor R10 R10 It can be expressed as

[0046]

[0047] Where C is the load capacitance.

[0048] The signal capture unit 3 is composed of an operational amplifier, a fourth resistor R4, a first resistor R1, a second resistor R2, and a third resistor R3, which can capture the voltage V across the tenth resistor R10. R10 It is amplified and output to the discharge module, thereby turning on the discharge module to start discharging the large capacitor C.

[0049] The above embodiments are merely examples of implementation forms of the technical concept of the present invention. The protection scope of the present invention is not limited to the above embodiments, but can be extended to equivalent technical means that can be conceived by those skilled in the art based on the technical concept of the present invention.

Claims

1. A discharge circuit, coupled between an input power source and a load unit; characterized in that: The discharge circuit comprises: A switch unit having a first terminal and a second terminal, a signal capture unit and a discharge unit; wherein the first terminal of the switch unit is connected to the positive electrode of the input power supply, the second terminal of the switch unit is connected to one end of the load unit, and the other end of the load unit is connected to the negative electrode of the input power supply and then grounded; The discharge unit is used to discharge the residual charge in the circuit; the discharge unit is composed of a first MOS tube and a sixth resistor; wherein one end of the sixth resistor is connected to the second terminal of the switch unit, and the other end is connected to the drain of the first MOS tube, the gate of the first MOS tube is connected to the output end of the signal capture unit, and the source thereof is grounded; The signal capturing unit at least comprises an amplifying circuit, which is used to capture the change of the signal of the circuit in the switch switching state by using the amplifying circuit, and send the signal to the discharge unit after processing; The signal capture unit specifically includes an amplifier circuit consisting of an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a first voltage regulator diode, wherein: The negative power supply pin of the operational amplifier is grounded, the positive power supply pin is connected to the second terminal of the switch unit, the in-phase input terminal is connected in series with the third resistor and then connected to the ground, the inverting input terminal is connected in series with the fourth resistor and then connected to the output terminal of the operational amplifier, one end of the first resistor is connected to the in-phase input terminal of the operational amplifier, and the other end is connected to the first terminal of the switch unit, one end of the second resistor is connected to the inverting input terminal of the operational amplifier, and the other end is connected to the second terminal of the switch unit, one end of the fifth resistor is connected to the output terminal of the operational amplifier, and the other end is connected to the cathode of the first voltage regulator diode, and the anode of the first voltage regulator diode is grounded; wherein, the stable voltage V of the first voltage regulator diode Z The threshold voltage V of the first MOS tube GS(th) The following relationship needs to be satisfied: In Z ≥V GS(th) ; or The signal capture unit specifically includes an amplifier circuit consisting of an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, and a tenth resistor, wherein: One end of the first capacitor is connected to the first terminal of the switch unit, and the other end is connected in series with the tenth resistor and then connected to the second terminal of the switch unit. The negative power supply pin of the operational amplifier is grounded, and the positive power supply pin is connected to the second terminal of the switch unit. The non-inverting input end is connected in series with the third resistor and then grounded, and the inverting input end is connected in series with the fourth resistor and then connected to the output end of the operational amplifier. One end of the second resistor is connected to the non-inverting input end of the operational amplifier, and the other end is connected to the common node of the first capacitor and the tenth resistor. One end of the first resistor is connected to the second terminal of the switch unit, and the other end is connected to the inverting input end of the operational amplifier.

2. The discharge circuit according to claim 1, characterized in that: The discharge unit includes a third MOS tube and a constant current circuit, and the constant current circuit discharges the charge in the circuit with a constant current.

3. The discharge circuit according to claim 2, characterized in that: The constant current circuit includes a seventh resistor, an eighth resistor, a ninth resistor, a second diode, a third diode, and a second bipolar transistor, wherein one end of the seventh resistor is connected to the second terminal of the switch unit, and the other end is connected to the base of the second bipolar transistor, one end of the eighth resistor is connected to the second terminal of the switch unit, and the other end is connected to the collector of the second bipolar transistor, one end of the ninth resistor is connected to the emitter of the second bipolar transistor, and the other end is connected to the drain of the third MOS tube, the anode of the second diode is connected to the base of the second bipolar transistor, and the cathode is connected to the anode of the third diode, the cathode of the third diode is connected to the drain of the third MOS tube, the source of the third MOS tube is grounded, and its gate is connected to the output end of the signal capture unit.

4. The discharge circuit according to any one of claims 1 to 3, characterized in that: The MOS tube is an N-channel enhancement type MOS tube.

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