KR890000306B1 - Circuit for prevention of excess voltage - Google Patents

Abstract

The circuit prevents application of excess voltage output occurring on an abnormality of the power source. The circuit comprises a line filter (1), a regulating cir. section (2) for converting AC to DC, IC power source (3), PWM control section (4), protective circuit (5) against an excess voltage application, output regulating circuit (6) for maintaining a constant DC output, and detection circuit (7) for detecting the steady voltage output and providing against an excess voltage output from the source.

Description

Overvoltage protection and output state detection circuit of power supply

1 is an overall block diagram of a power supply including the present invention.

2 is an internal circuit diagram of the PWM controller 4 of FIG.

3 is a detailed circuit diagram of the overvoltage protection and output state detection circuit 7 of the present invention.

4 is an output DC power supply state when input AC power is on / off.

The present invention relates to a DC power supply device, the overvoltage protection and output state detection of the power supply for preventing the overvoltage is applied to the output terminal due to the abnormality of the power supply device of the DC power supply of a prescribed value supplied to electronic devices such as computers It is about a circuit. In general, a DC power supply device has a problem that an overvoltage of a predetermined value or more occurs at an output terminal due to an abnormal state inside a circuit and an abnormality of an input power supply, which is applied to a load such as a computer, causing a failure.

The present invention solves the conventional problems as described above with reference to the accompanying drawings in detail the circuit configuration and operation effects as follows.

1 is a block diagram showing the overall circuit configuration of a DC power supply including the present invention, a low pass filter in-line filter (1), a rectifier circuit unit (2) for converting AC into DC, and a constant constant voltage for supplying a PWM IC. IC power supply (3), PWM control (4) for controlling pulse width, overcurrent protection circuit (5) for protecting circuit from overcurrent, output rectifier circuit (6) for maintaining constant DC output and overvoltage generation It is composed of an overvoltage protection and an output state detection circuit (7) to protect the circuit from the damage and to recognize the stable state of the DC output voltage.

Hereinafter, the circuit operation of the present invention will be described.

When the AC power input through the AC power input terminal of FIG. 1 is input to the IC power supply unit 3 through the line filter 1, the constant constant voltage Vsrc output from the IC power supply unit 3 is converted into the PWM control unit 4. The PWM control unit 4 has a soft start function and has a built-in regulator for switching operation in a steady state. The regulator generates an output voltage. The output voltage Vref of this regulator is used as a reference voltage of the overvoltage protection and output state detection circuit 7. Here, when the internal regulator has a predetermined voltage, that is, the soft start function is completed, the function of the PWM controller 4 is enabled to start a switching operation, and through the transformer T1, 2 There is a transfer of energy to the vehicle side. The applied voltage of the transformer T1 secondary side is determined according to the turns ratio of the transformer T1, has a pulse shape, and is applied to the output rectifying circuit unit 6 to output a DC voltage. However, in order for the output DC voltage to have a constant value and maintain a desired state, the output DC voltage Vout terminal F is connected to the differential amplifier input terminal B of the PWM controller 4 to obtain a constant voltage. It is. If an abnormality occurs in the load and the power supply and an overcurrent or an overvoltage occurs, the overcurrent protection circuit 5 and the overvoltage protection and output state detection circuit 7 recognize an abnormal state and disable the PWM control unit 4. (Disable) stops the switching operation and does not damage the load and power supply.

2 is an internal circuit diagram of the PWM controller 4, which includes an oscillator 4a, a differential amplifier 4b, a shutdown unit 4c for disabling the circuit, and a PWN unit for controlling the pulse width. 4d, logic 4e, and output transistor 4f. In order to keep the output voltage constant, terminal F of FIG. 1 is connected to terminal B of differential amplifier 4b and is differential As described above, the terminal A of the amplifier 4b is connected to Vref and compared and amplified to apply the signal to the input terminal PWM of the PWM unit 4d. In addition, a triangular wave of a constant frequency due to R-C oscillation is input to the input terminal 의 of the PWM unit 4d, compared, and output, and then applied to the logic unit 4e. On the other hand, the logic unit 4e generates a pulsed output signal by the flip flop operation and is used as a bias of the output transistor 4f. That is, the PWM operation in which the bias of the output transistor 4f is changed by the comparison value of the PWM section 4d is performed.

3 is a detailed circuit diagram of the overvoltage protection and output state detection circuit 7, which is an essential part of the present invention, and includes an output voltage comparison unit 7a, a shutdown signal generator 7b, a constant voltage comparison unit 7c, and an output power abnormality sense The branch portion 7d, the shutdown control portion 7e, and the output power state display portion 7f. The output voltage comparator 7a divides Vout output to the output terminal F of the output rectifying circuit part 6 of FIG. 1 and compares it with the divided voltage of Vref output from the PWM control section 4, and then outputs the logic. The signal is applied to the shutdown signal generator 7b and the logic of the shutdown signal is applied to the shutdown terminal 4c input terminal C of the PWM controller 4 according to the output logic of the output voltage comparator 7a. Enable or disable 4). In addition, the constant voltage comparator 7c compares the logic signal output from the output voltage comparator 7a with the divided voltage of Vsrc output from the output terminal D to the IC power supply 3 of FIG. The logic signal is applied to the output power supply abnormality detection unit 7d to switch the transistor Q2 so that the output signal is applied to the output power state display unit 7f and the shutdown control unit 7e. The output power state display unit 7f can visually check whether there is an abnormality in output power depending on whether the light emitting diode (LED.1) is lit or not. This was recognized. The shutdown control unit 7e compares the logic of the output power state signal supplied to the load of the computer and the divided voltage of Vsrc output from the output terminal D of the IC power supply unit 3 to generate the shutdown signal. In response to the on / off switching operation of the transistor Q1, the logic of the shutdown signal is applied to the input unit c of the shutdown unit 4c of the PWM control unit 4 by applying the unit 7b to the PWM control unit 4. Enable or disable. Referring to the circuit operation when an overvoltage occurs in the output terminal due to an error in the power supply device is as follows.

When Vout outputted to the output terminal F of the output flow circuit unit 6 of FIG. 1 is input to the Vout terminal, the voltage is divided by the resistors R1 and R2, and the divided voltage is divided by the '-' terminal of the comparator A3. Vref, which is a reference voltage output from the PWM control unit 4 of FIG. 1, is input to the Vref terminal and divided and applied to the resistors R3 and R4, respectively. At this time, the comparator A3 compares this, and when Vout is greater than the divided value of Vref, the output of the comparator A3 becomes a logic " 0 " state and is applied to the base of the transistor Q1 through the resistor R19. Turn transistor Q1 ON. As a result, a '-' potential appears at the resistor R20 terminal, and the potential C operates the terminal C of the PWM control unit 4 of FIG. 1 connected to the collector side of the transistor Q1 as a logic " 1 ". This disables the PWM control unit 4 and immediately stops all switching operations, thus protecting the computer used as the circuit and load of the power supply. On the other hand, when the power supply is normal, the output of the comparator A3 becomes a logic " 1 " and the transistor Q1 is turned off, so that the potential across the resistor R20 does not appear. The terminal C of the PWM control unit 4 in the figure maintains a logic " 0 " state to keep the circuit in a steady state.

When the DC output of the garden feeder is normal, the light emitting diode (LED.1) is turned on. If the DC output is abnormal, the light emitting diode (LED.1) is turned off immediately. It is configured to recognize this in the back load. In this series of processes, when the DC voltage output to the output terminal F of the output rectifying circuit 6 of FIG. 1 is normal, the '+' terminal of the comparator A2 has a higher potential than the '-' terminal. The output of A2) has a logic " 1 " state. In addition, since the '+' terminal of the comparator A1 is divided with the resistors R5 and R6, the input potential of the '-' terminal of the comparator A1 becomes higher, so that the output of the comparator A1 becomes higher. Becomes a logic " 0 " state and is applied to the base of transistor Q2 through resistor R9, thereby turning transistor Q2 on and having a '+' potential across resistor R11, resulting in a light emitting diode ( By driving LED.1), a signal of logic " 1 " is transmitted to a load of a computer lamp.

At the same time, the voltage of Vsrc divided by the resistors R16 and R17 is applied to the '-' terminal of the comparator A4 and the comparator A4 is configured so that the '-' terminal side of the comparator A4 has a high potential. The output terminal of the < RTI ID = 0.0 >) < / RTI > becomes logic " 1 " and is applied to the base of the transistor Q1 through the resistor R15 to turn off the transistor Q1. The terminal c is kept in a logic " 0 " state to maintain a normal state.

If a circuit abnormality occurs, such as when the input power is turned off, Vout outputted to the output terminal F of the output rectifying circuit section 6 of FIG. 1 has a time for maintaining a certain voltage and the output is maintained. Before turning off completely, set the POWER GOOD signal to NO GOOD and send it to a computer. In this series of processes, as shown in FIG. 4, when the output voltage Vout is gradually decreased, the '-' terminal of the comparator A2 is in a state of logic "1", and the output of the comparator A2 is The output of the comparator A1 is brought into the logic " 1 " state by setting the logic " 0 " to the logic " 0 " state of the comparator A1.

Accordingly, transistor Q2 is turned off and no potential appears at both ends of resistor R11, thereby turning off light-emitting diode LED.1, and a logic " 0 " signal is applied to the computer to completely eliminate Vout. It is possible to detect the abnormal state of the power supply before it is turned off and to identify the abnormal state directly. In addition, in other circuit abnormal states, as described above, as the terminal c of the PWM control unit 4 maintains the logic " 1 " state, the POWER GOOD signal becomes logic " 0 " and the light emitting diode (LED.1). Is configured to be off.

As described above, when the overvoltage is detected at the output terminal due to an abnormality in the power supply, the present invention stops the circuit operation by comparing it with the reference voltage, thereby protecting electronic devices such as computers from overvoltage, and By detecting the abnormal condition of the computer, it is possible to keep the data processing function of the computer and the like, and the user can directly detect the power supply state with the naked eye.

Claims (1)

Vref of the PWM control unit 4 in connecting the overvoltage protection and output state detection circuit 7 between the PWM control unit 4 and the output terminal F of the output rectifying circuit unit 6 as described herein and shown in the drawings. An output voltage comparator 7a is connected to terminal A to compare the divided voltages of Vout and Vout, and a constant voltage comparator 7c for comparing the output of the output voltage comparator 7a with the divided voltage of Vsro. And an output terminal of the shutdown signal generator 7b for generating logic of the shutdown signal, respectively, and a signal output from the constant voltage comparator 7c is applied to the output power abnormality detection unit 7d to sense the output power abnormality. The logic signal output from the branch unit 7d is connected to the output garden state display unit 7f and the shutdown control unit 7e so that the output signal of the output power state display unit 7f can be transmitted to a load such as a computer. Output power abnormality detection applied to the shutdown control unit 7e The voltage obtained by dividing the output signal of 7d and the divided voltage of VSRC are compared and outputted to the shutdown signal generator 7b to output the logic of the shutdown signal to the shutdown unit 4c of the PWM controller 4. The overvoltage protection and output state detection circuit of a power supply, characterized in that configured by connecting to the PWM control unit (4) to enable or disable by applying to the input terminal (c).

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