Rapid turn-off overvoltage protection circuit

Abstract

The utility model relates to the technical field of electronics, in particular to a fast turn-off overvoltage protection circuit, which can improve the turn-off speed of overvoltage protection, and comprises a partial voltage detection circuit used for providing detection voltage; the comparison control circuit is used for comparing the detection voltage with the set voltage by using double comparators to obtain a switching signal; and a power supply switching circuit for switching off or conducting the power supply by the switching signal.

Description

Technical Field

[0001] The utility model relates to the field of electronic technology, in particular to a fast-shutdown overvoltage protection circuit. Background Art

[0002] Flow cytometers belong to the field of in vitro diagnostic equipment and are used for biochemical analysis. Flow cytometers have a precise structure and contain a variety of precise and expensive components. It is of great significance to be able to reliably protect each component module in the event of an accidental overvoltage of the power supply.

[0003] Currently, dedicated overvoltage protection devices, such as varistors or protection circuits, are commonly used for power supply overvoltage protection, but conventional overvoltage protection circuits have limited shutdown speeds, especially in high-current power supply circuits. Summary of the invention

[0004] In order to solve the above technical problems, the utility model provides a fast-shutdown overvoltage protection circuit, which can improve the overvoltage protection shutdown speed.

[0005] The technical solution is as follows: a fast-shutdown overvoltage protection circuit, characterized in that it includes:

[0006] A voltage-dividing detection circuit, used for providing a detection voltage;

[0007] The comparison control circuit uses a dual comparator to compare the detection voltage with the set voltage to obtain a switch signal;

[0008] The power switch circuit cuts off or turns on the power supply by the switch signal.

[0009] It is further characterized in that the voltage division detection circuit comprises a resistor R1 and a resistor R2 connected in series, one end of the resistor R1 is a voltage input end, and the other end of the resistor R1 is connected to one end of the resistor R2 as a detection voltage collection point;

[0010] The comparison control circuit includes a comparator U2 and a comparator U3, the positive phase input terminal of the comparator U2 and the negative phase input terminal of the comparator U3 are respectively input with a set voltage, the negative phase input terminal of the comparator U2 and the positive phase input terminal of the comparator U3 are respectively connected to the detection voltage collection point, the output terminal of the comparator U2 is connected to the positive electrode of the voltage regulator tube D2 and the gate terminal of the switch tube Q2 through a resistor R4, the output terminal of the comparator U3 is connected to the drain terminal of the switch tube Q2 and the power switch circuit through a resistor R3, and the negative electrode of the voltage regulator tube D2 and the source terminal of the switch tube Q2 are both connected to the input power supply;

[0011] The power switch circuit includes a voltage regulator tube D1 and a MOS tube Q1, the positive electrode of the voltage regulator tube D1 and the gate end of the MOS tube Q1 are connected to the comparison control circuit, the source end of the MOS tube Q1 and the negative electrode of the voltage regulator tube D1 are both connected to the power supply, and the drain end of the MOS tube Q1 is the power output end.

[0012] After adopting the utility model, the double comparator structure is utilized and the switch tube Q2 is added, so the overvoltage protection shut-off speed is effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the circuit schematic diagram of the utility model;

[0014] Figure 2 This is a circuit schematic diagram for implementing the utility model. DETAILED DESCRIPTION

[0015] See Figure 1 As shown, a fast-shutdown overvoltage protection circuit comprises:

[0016] The voltage division detection circuit includes a resistor R1 and a resistor R2 connected in series, one end of the resistor R1 is a voltage input end, and the other end of the resistor R1 is connected to one end of the resistor R2 as a detection voltage collection point for providing a detection voltage;

[0017] A comparison control circuit includes a comparator U2 and a comparator U3, wherein a set voltage is input to a positive input terminal of the comparator U2 and an inverting input terminal of the comparator U3 respectively, and the inverting input terminal of the comparator U2 and the positive input terminal of the comparator U3 are respectively connected to a detection voltage collection point, an output terminal of the comparator U2 is connected to a positive electrode of a voltage regulator tube D2 and a gate terminal of a switch tube Q2 via a resistor R4, an output terminal of the comparator U3 is connected to a drain terminal of the switch tube Q2 and a power switch circuit via a resistor R3, a negative electrode of the voltage regulator tube D2 and a source terminal of the switch tube Q2 are both connected to an input power supply, and a dual comparator is used to compare the detection voltage and the set voltage to obtain a switch signal;

[0018] The power switch circuit includes a voltage regulator tube D1 and a MOS tube Q1. The positive electrode of the voltage regulator tube D1 and the gate end of the MOS tube Q1 are connected to the comparison control circuit. The source end of the MOS tube Q1 and the negative electrode of the voltage regulator tube D1 are both connected to the power supply. The drain end of the MOS tube Q1 is the power output end. The power supply is cut off or turned on by a switch signal.

[0019] The specific implementation circuit is as follows Figure 2As shown, comparator U2 and comparator U3 are implemented by dual-channel comparator U1, model TLV1812, the set voltage V_set is provided by voltage reference chip U4, LM285-2.5 generates 2.5V, the power supply voltage is 24V, resistor R1 is 9.42K, resistor R2 is 1K, the accuracy is 1%, and the theoretical voltage protection point is set to 26.5V. The voltage protection point can be adjusted by adjusting the voltage dividing ratio of the voltage dividing resistors R1 and R2. The voltage dividing signal, that is, the detection voltage V_monitor voltage value is (Powerin)* R2 / (R1+R2).

[0020] During operation, when the power supply voltage is not over-voltage, V_monitor is less than V_set, when the first comparator outputs OutA at a high level, the second comparator outputs OutB at a low level, at which time the switch tube Q2 is turned off, the MOS tube Q1 is turned on, and the power is turned on; when the power supply voltage is over-voltage, V_monitor is greater than V_set, the first comparator outputs OutA at a low level, the second comparator outputs OutB at a high level, at which time the switch tube Q2 is turned on, the MOS tube Q1 is turned off, and the power is cut off.

[0021] The peripheral resistor R21 is used for current limiting. The resistor R4 is 1K ohm, and the value should be as small as possible to increase the power off speed. The resistor R3 is 100K ohm. A slightly larger value can appropriately reduce the power on speed and achieve a certain degree of power slow start effect. The switch tube Q2 is PMV88ENE PMOS tube, which has an input capacitance of 196pF and a continuous current of 2.2A, which can quickly turn off the power switch circuit. The voltage regulator tube D2 is BZT52H-B18 to protect the gate of the switch tube Q2. The MOS tube Q1 is RSJ250P10 PMOS tube, which supports a continuous current of up to 25A. The voltage regulator tube D1 is BZT52H-B18 to protect the gate of the MOS tube Q1. The actual shutdown response is fast (<20us), the start slope is smooth, and the voltage protection point can be easily adjusted by adjusting the voltage divider ratio of the voltage divider detection circuit.

Claims

1. A fast-shutdown overvoltage protection circuit, characterized in that: It includes: A voltage-dividing detection circuit, used for providing a detection voltage; The comparison control circuit uses a dual comparator to compare the detection voltage with the set voltage to obtain a switch signal; The power switch circuit cuts off or turns on the power supply by the switch signal.

2. A fast-shutdown overvoltage protection circuit according to claim 1, characterized in that: The voltage division detection circuit includes a resistor R1 and a resistor R2 connected in series, one end of the resistor R1 is a voltage input end, and the other end of the resistor R1 is connected to one end of the resistor R2 as a detection voltage collection point.

3. A fast-shutdown overvoltage protection circuit according to claim 2, characterized in that: The comparison control circuit includes a comparator U2 and a comparator U3, wherein the positive phase input terminal of the comparator U2 and the negative phase input terminal of the comparator U3 are respectively input with a set voltage, the negative phase input terminal of the comparator U2 and the positive phase input terminal of the comparator U3 are respectively connected to the detection voltage collection point, the output terminal of the comparator U2 is connected to the positive electrode of the voltage regulator tube D2 and the gate terminal of the switch tube Q2 through a resistor R4, the output terminal of the comparator U3 is connected to the drain terminal of the switch tube Q2 and the power switch circuit through a resistor R3, and the negative electrode of the voltage regulator tube D2 and the source terminal of the switch tube Q2 are both connected to the input power supply.

4. A fast-shutdown overvoltage protection circuit according to claim 3, characterized in that: The power switch circuit includes a voltage regulator tube D1 and a MOS tube Q1, the positive electrode of the voltage regulator tube D1 and the gate end of the MOS tube Q1 are connected to the comparison control circuit, the source end of the MOS tube Q1 and the negative electrode of the voltage regulator tube D1 are both connected to the power supply, and the drain end of the MOS tube Q1 is the power output end.

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