KR19990013271U - Overvoltage Protection Circuit of DC Power Supply - Google Patents

Abstract

An overvoltage protection circuit of a DC power supply device, comprising: an overvoltage detection circuit for detecting an overvoltage, a protection signal generation circuit for stopping operation of the DC power supply device when an overvoltage is detected in the overvoltage detection circuit; Including an overvoltage display circuit that displays the overvoltage by using a voltage to produce a DC power supply that does not occur a malfunction that may appear due to the change of the output voltage.

Description

Overvoltage Protection Circuit of DC Power Supply

The present invention relates to an overvoltage protection circuit of a DC power supply device. In particular, an overvoltage of an insulated DC power supply device configured to stop an operation of a power supply device by controlling a pulse width control integrated circuit (IC) with an isolated signal when an overvoltage is applied to a load. It relates to a protection circuit.

Hereinafter, with reference to the accompanying drawings as follows.

1 is a configuration diagram showing a protection circuit of a power supply device according to the prior art, Figure 2 is a circuit diagram showing an overvoltage protection circuit according to the prior art.

As shown in FIG. 1, the rectifying unit 1 receives and rectifies AC power, the first to third power output units 2, 3, 4, and the auxiliary power generating unit 5 for generating an auxiliary power source. ), A pulse width modulator 6 driven according to the output power of the auxiliary power generator 5, an overvoltage detection circuit 7 for detecting an overvoltage in comparison with a set reference voltage, and the overvoltage detection circuit ( The output voltage Vcc of the subsidiary power generator 5 is removed by latching the output voltage of the overvoltage controller 8 and the output voltage of the overvoltage controller 8 to control the voltage applied to the load according to the output signal of 7). It consists of a latching part 9.

As shown in FIG. 2, an auxiliary power is generated using an overvoltage controller 8 for controlling a voltage applied to a load according to a detection signal of the overvoltage detection circuit 7 and an output signal of the overvoltage controller 8. It consists of a latching part 9 which stops the output of the part 5.

The overvoltage detecting unit 7 divides the output voltage VB of the second power supply output unit 3 among the voltages VA, VB, and VC applied to the respective loads by dividing the resistors R1 and R2. Set the reference voltage and stabilize the reference voltage with zener diode (ZD1).

In addition, the output voltage of the first power output unit 2 is divided by the resistors R3 and R4 and compared with the reference voltage through the first comparator COMP1 and amplified by the resistor R8.

The output voltage of the second power output unit 3 is divided by the resistors R5 and R6 and biased through the resistor R7. The resistor R9 is compared with the reference voltage through the second comparator COMP2. Amplify).

In addition, when the output of the comparators COMP1 and COMP2 is high when the overvoltage is applied, the transistor Q1 is cut off, and the output voltage VB of the second power output unit 14 is applied to the resistor R13. Via is biased through, transistor Q2 conducts and then drives photodiode PD1.

When the phototransistor PT conducts according to the control signal of the overvoltage control unit 7, the power supply Vcc of the auxiliary power generator 5 is biased by the resistor R15.

Then, the transistor Q3 is conducted and biased by the resistor R16, and the transistor Q4 is conducted to remove the output voltage of the auxiliary power generator 5.

The protection circuit of the DC power supply according to the prior art has a problem that the reliability is poor due to the configuration of the complex overvoltage control unit, causing destruction of the device due to overcurrent, or malfunctioning.

The present invention was devised to solve such a problem. In an insulated DC power supply, the system is protected when the overvoltage is applied to the load while maintaining the electrical insulation of the input and output terminals. Be aware.

Therefore, the purpose is to increase the reliability of the protection circuit by using a device that can prevent malfunction, precise control and minimize environmental constraints.

1 is a configuration diagram showing the configuration of a power supply according to the prior art

FIG. 2 is a detailed view showing the overvoltage protection circuit of FIG. 1 in detail.

3 is a block diagram showing the configuration of a DC power supply according to the present invention

4 is a circuit diagram illustrating in detail the overvoltage protection circuit of FIG.

5 is a circuit diagram showing another embodiment of the present invention

Explanation of symbols for main parts of the drawings

10: input filter circuit 11: transformer

12,15: rectifier circuit 13,16: smooth circuit

14: first load 17: second load

18: overvoltage protection circuit 19: overvoltage detection circuit

20: insulation circuit 21: overvoltage display circuit

22: protection signal generation circuit 23: compensation and insulation circuit

24 pulse width modulation control circuit 25 auxiliary power

The present invention is characterized by the overvoltage protection circuit of DC power supply. An overvoltage detection circuit for detecting an overvoltage, a protection signal generation circuit for stopping the operation of the DC power supply when the overvoltage detection circuit detects the overvoltage, and an overvoltage display circuit for displaying the overvoltage using the voltage induced in the protection signal generation circuit It consists of.

Hereinafter, with reference to the accompanying drawings as follows.

3 is a configuration diagram showing a configuration of a DC power supply according to the present invention, Figure 4 is a circuit diagram showing in detail the overvoltage protection circuit of Figure 3, Figure 5 is a circuit diagram showing another embodiment of the present invention.

As shown in FIG. 3, the DC power supply device to which the present invention can be applied includes an input filter circuit 10, a transformer 11 for supplying electric power isolated from the input filter circuit 10, and the transformer ( 11, rectifying circuits 12 and 15 for rectifying the power output from 11, smoothing circuits 13 and 16 for smoothing the current rectified in the rectifying circuits 12 and 15, and the smoothing circuit 13 Overvoltage protection circuit for sensing the application of overvoltage to the first and second loads 14 and 17 and the first and second loads 14 and 17 operating by receiving the power output from 18), a circuit 23 for compensating and insulating when overvoltage is applied, and a pulse width modulation control circuit for controlling a main switch to maintain a stable output by sensing an output voltage output from the compensating and insulating circuit 23 ( 24 and an auxiliary power supply 25 for supplying DC power to the pulse width modulation control circuit 24.

As shown in FIG. 4, the overvoltage protection circuit 18 includes an overvoltage detection circuit 19 for detecting an overvoltage, an insulation circuit 20 for receiving and insulating a voltage sensed by the overvoltage detection circuit 19. And an overvoltage display circuit 21 for displaying the overvoltage detected by the overvoltage detection circuit 19, and a protection signal generation circuit 22 for stopping the DC protection device when the signal output from the insulation circuit 20 is an overvoltage. It consists of.

The overvoltage detecting circuit 19 divides the output voltage into resistors R1 and R2 for outputting the electromotive voltage, a zener diode U2 for stabilizing the reference voltages of the resistors R1 and R2, and the resistor. And a comparator U1A for comparing the reference voltages of R1 and R2 with the value of the constant voltage U1, a resistor R4 and a photodiode PD1 for remotely transmitting current as an overvoltage signal.

When the output of the comparator U1A comparing the output voltage Vo1 and the constant voltage U1 is an overvoltage, an overvoltage is applied to a load so that a low voltage is input to the photocoupler PC1. ) And the resistor R4 is set so that an appropriate current flows through the photocoupler PC1.

The protection signal generation circuit 22 includes a plurality of transistors Q1 and Q2, resistors R5, R6, R7, and R9, a capacitor C1, a diode D1, and a phototransistor. PT1) are connected in parallel.

When the protection signal generation circuit 13 is in a normal operating state, since the transistor Q1 is in a blocking state, the protection signal is not applied to the pulse width modulation control circuit 15.

On the other hand, when the overvoltage is applied to the load and the phototransistor PT1 is driven, the transistors Q1 and Q2 are conducted by the set values of the resistors R5, R6, and R7, and the resistors R6 and R7 are conducted. Is divided by).

In addition, by applying an appropriate voltage to the pulse width modulation control circuit 15 through the diode D1, the driving of the switching element is stopped and the operation of the power supply device is also stopped.

The transistors Q1 and Q2 remain in a conductive state unless the power source Vcc is removed, and the resistor R6 prevents excessive current from flowing.

In addition, the resistor R9 sets the magnitude of 100 times or more of the resistor R5 to prevent malfunction due to noise or the like.

The overvoltage display circuit 12 has a light emitting diode LED1 and a resistor R7 connected in parallel.

When the transistors Q1 and Q2 are in a conductive state, a voltage is applied to the light emitting diode LED1 of the overvoltage display circuit 12 to indicate an overvoltage state.

In addition, the diode D1 of the protection signal generation circuit 22 prevents the malfunction of the overvoltage display circuit 21 when a voltage is applied to the pulse width modulation control circuit 25 by another means.

According to another embodiment of the present invention, as shown in FIG. 5, in the case of a multi-output power supply device, only an overvoltage detection circuit is added and the photodiode PD1 and the phototransistor PT1 and PT2 are connected in parallel. The prevention circuit can be easily configured.

According to the present invention, an overload protection circuit is applied to an insulated DC power supply so that the user can recognize an overvoltage state by displaying an overvoltage state and generating a signal when an overvoltage is applied while maintaining electrical insulation.

In addition, by using a comparator and a reference voltage in the overvoltage sensing circuit, it is possible to increase the precision and minimize the constraints of environmental conditions such as the ambient temperature, and to prevent the malfunction that may occur due to the change of the output voltage.

Claims (6)

In the overvoltage protection circuit of DC power supply, An overvoltage detection circuit for detecting an overvoltage of the DC power supply; A protection signal generating circuit for stopping the operation of the DC power supply when an overvoltage is applied from the overvoltage detecting circuit; And an overvoltage display circuit for displaying an overvoltage using the voltage induced by the protection signal generation circuit. The method of claim 1, The overload detection circuit includes resistors R1 and R2 for distributing an output voltage and outputting a reference voltage, a zener diode U2 for stabilizing a reference voltage of the resistors R1 and R2, and the resistor R1. A comparator U1A for comparing the reference voltage and the divided voltage of R2, a photodiode PD1 for remotely transmitting a current as an overvoltage signal, and resistors R3 and R4. Overvoltage Protection Circuit. The method of claim 1, The protection signal generation circuit includes a phototransistor PT1 for switching the output signal of the overvoltage sensing circuit to vary the amount of current, a transistor Q2 for switching according to the switching state of the phototransistor PT1, and the auxiliary power supply; A resistor R8 for biasing the auxiliary power supply of the generator and applied to the transistor Q2, a transistor Q1 for switching according to the switching state of the transistor Q2, and a resistor for distributing the output voltage of the transistor Q2. (R5) and (R6), a capacitor (C1) and diode (D1) for outputting the voltage output through the resistor (R5) (R6) at a constant voltage, and a resistor (R9) to prevent malfunction Overvoltage protection circuit of DC power supply. The method of claim 1, The overvoltage display circuit includes a light emitting diode (LED1) and a resistor (R7) are connected in parallel to the overvoltage protection circuit of the DC power supply. The method of claim 2, And a photodiode (PD1) is driven when the output of the comparator (U1A) is low to sense the overvoltage, characterized in that the overvoltage protection circuit of the DC power supply. The method of claim 4, wherein The overvoltage display circuit is a voltage protection circuit for a direct current power supply device, characterized in that when the transistor (Q1) (Q2) is in a conductive state, the voltage is applied to the light emitting diode (LED1), and the overvoltage state is displayed at the same time.