• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
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  • 引用文献
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    • 专利摘要:
    PURPOSE: A circuit for protecting high voltage of a monitor is provided to block VAC(Volts Alternating Current) in common use, when the VAC in common use over a regular scope flows into SMPS(Switched Mode Power Supply). CONSTITUTION: SMPS(Switched Mode Power Supply) of a monitor converts VAC(VoltsAlternating Current) in common use, flowed from outside, to DC(Direct Current) voltage through a bridge diode(D1) and a smooth capacitor(C4), supplies on a first side of a transformer(2), and supplies to each circuit of the monitor, by converting the VAC into the DC voltage. A circuit for protecting high voltage of the monitor comprises: a VAC reducing section(10) for reducing voltage by receiving the inputted VAC in common use from outside; a DC converter(20) for converting the reduced VAC into the DC voltage; a high voltage sensor(30) for outputting a high voltage sensing signal when the converted DC voltage(10) is over regular voltage; JFET(Junction type Field Effect Transistor)s(JFET11,JFET12), which a gate terminal receives the high voltage sensing signal, and which a drain terminal and a source terminal are connected to a supply line of the VAC, and for supplying/blocking the VAC by being on/off according to an over voltage sensing signal; and diodes(D11,D12) for being reversely connected between the drain terminal and the source terminal, blocking reverse current, and providing a flowing path of forward current.
    公开号:KR20000021533A
    申请号:KR1019980040684
    申请日:1998-09-30
    公开日:2000-04-25
    发明作者:최재순
    申请人:전주범；대우전자 주식회사；
    IPC主号:
    专利说明:

    A over-voltage protection circuit in a monitor
    The present invention relates to a high voltage protection circuit of a monitor, and relates to a high voltage protection circuit of a monitor which is configured to cut off the supply of the commercial AC voltage by using a semiconductor having a fast reaction rate when a commercial AC voltage of more than a rated range flows into a switching power supply circuit. will be.
    In general, the power circuit serves to properly supply the voltage required for each part of the monitor, which is related to the SMPS (Switched Mode Power Supply), which is smaller, lighter and more efficient than the Linear Power Supply. Technology is currently in a rapidly developing trend.
    As shown in FIG. 1, the conventional switching power supply circuit includes a DC power supply 1, a transformer 2, a power transistor 3, a control IC 4, an output 5, and a voltage. It consists of the feedback part 6.
    Referring to Figure 1, the operation of the general switching power supply (SMPS), when a commercial AC voltage of 100V or 220V is first applied through the fuse (Fuse), the line filter (L1, L2) and capacitors (C1, C2, C3) removes noise introduced through the commercial AC voltage by the L · C resonance action.
    On the other hand, the commercial AC voltage passing through the line filter (L1, L2) and capacitors (C1, C2, C3) is rectified by the bridge diode (D1) in the smoothing capacitor (C4) through the inrush current prevention resistor (R1) Smoothed DC voltage ( V i And then to the primary winding of the transformer (2).
    At the same time, the rectified voltage rectified by the bridge diode D1 is applied to the control IC 4. V cc The resistor IC is applied to the stage to operate the control IC 4, and the power transistor 30 is turned on / off by the PWM control signal output from the control IC 4. .
    That is, the DC voltage ( V i ) Is applied, the DC voltage ( V i ), The driving power of the control IC (4) ( V cc ) Reaches a starting voltage, the control IC 4 is operated to generate a PWM control signal, and the power transistor 3 is turned on / off by this PWM control signal.
    When the power transistor 3 remains on and turns off by the PWM control signal output from the control IC 4, induced electromotive force is induced from the primary winding of the transformer 2 to the secondary winding. Done.
    Therefore, the transformer 2 is the AC voltage required in the secondary winding by the PWM control signal ( V s, V sm, V sn ) Will be printed.
    By repeating this operation, the AC voltage output from the secondary winding of the transformer 2 V s, V sm, V sn ) Again through the output unit (5) DC voltage ( V o, V om, V on Is converted to).
    That is, the AC voltage inputted to the output unit 5 V s, V sm, V sn ) Is controlled by the rectifier diodes (D2, D3) and smoothing capacitors (C7, C8). V o, V om, V on ) Is supplied to each circuit of the monitor to operate the circuit.
    However, the power supply voltage output through the output unit 5 V o, V om, V on ) Rises above the reference voltage, resulting in breakage of the circuit elements due to overvoltage, which can shorten the life of the power supply circuit. Therefore, in order to maintain the output voltage of the output unit 5 at a constant voltage, the switching power supply circuit The SMPS generally includes a voltage feedback section 6.
    In more detail, the power supply voltage supplied to each circuit of the monitor ( V o ) Is sensed by the voltage feedback section 6 composed of the error amplifier EA and the photocouplers PC1 and PC2, and the detection signal is input to the feedback stage of the control IC 4.
    For example, the power supply voltage output from the transformer 2 ( V o Is larger than during normal operation, the error amplifier EA senses the overvoltage and lowers the voltage at the output side of the error amplifier EA. At this time, the output side of the error amplifier EA is connected to the cathode end of the light emitting unit PC1 of the photocoupler, and the other end of the light emitting unit PC1 is output ( V om In this case, more current flows momentarily in the light emitting unit PC1 than in normal operation, thereby emitting as much light.
    Accordingly, the light receiving unit PC2 of the photocoupler receives the light, converts the optical signal into an electrical signal, and outputs the light signal to the feedback terminal of the control IC 4. The input current increases than during normal operation, so that the control IC 4 generates a PWM control signal with a short on time, and the on time of the power transistor 3 is shortened by the PWM control signal.
    As the on-time of the power transistor 3 is shortened, the induced electromotive force induced from the primary winding of the transformer 2 to the secondary winding ( V s, V sm, V sn ) Is lowered, the power supply voltage (outputted from the switching power supply circuit (SMPS) V o, V om, V on ) Is maintained at a constant voltage and supplied to each circuit of the monitor.
    As described above, the conventional switching power supply circuit (SMPS) operates by receiving a commercial AC voltage within a rated range. When a commercial AC voltage above the rated range flows into the switching power supply circuit, the fuse is forcibly cut off. The monitor was protected from overvoltage.
    However, in case of forcibly breaking the fuse to protect the monitor from overvoltage, the user has had to change the fuse again. Eliminate the hassle to replace.
    That is, the fuse circuit breaker is connected between the output terminal of the switching power supply circuit (SMPS) and the load (each part of the monitor circuit), and the fuse circuit breaker is operated when the overvoltage occurs to block the inflow of the overvoltage.
    However, the fuse or fuse circuit breaker has a problem in that the monitor often burns out before the fuse or fuse circuit breaker blocks the inflow of the overvoltage when the overvoltage occurs.
    Accordingly, the present invention has been made to solve the above problems, the high voltage of the monitor is to block the supply of the commercial AC voltage using a semiconductor having a fast reaction rate when a commercial AC voltage of more than the rated range flows into the switching power supply circuit The purpose is to provide a protection circuit.
    The high voltage protection circuit of the monitor according to the present invention for achieving the above object,
    After converting the commercial AC voltage from the outside into DC voltage through bridge diode and smoothing capacitor, supply it to the primary side of the transformer and convert it into DC voltage when the desired AC voltage is supplied from the secondary side. In the switching power supply circuit of the monitor,
    An AC voltage reduction unit configured to reduce the voltage by receiving the commercial AC voltage input from the outside;
    A DC converter converting the reduced AC voltage into a DC voltage;
    A high voltage detector for outputting a high voltage detection signal when the converted DC voltage is above a predetermined voltage;
    A junction type field effect transistor having a gate terminal receiving the high voltage detection signal and a drain terminal and a source terminal connected to the commercial AC voltage supply line, and being turned on / off according to the overvoltage detection signal to supply / block the commercial AC voltage; And
    It is characterized in that the diode is connected in the reverse direction between the drain terminal and the source terminal of the junction field effect transistor to block the reverse current and provide a flow path of the forward current.
    1 is a circuit diagram showing a general switching power supply circuit,
    2 is a circuit diagram showing a high voltage protection circuit of the monitor according to the present invention;
    3 is a waveform diagram of each part of the circuit according to the present invention.
    * Names of symbols according to the main parts of the drawings
    10: AC voltage reduction unit 20: DC conversion unit
    30: high voltage detection unit D 11, 12: first and second diodes
    phase shifter: ideal phase multiplier: multiplier
    OP11: Amplifier OP12: Comparator
    JFET 1,2: 1st and 2nd P-channel isolated junction field effect transistor
    R 11, 12, 13, 14, 15, 16, 17, 18: resistance
    Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
    2 is a circuit diagram showing a high voltage protection circuit of the monitor according to the present invention.
    As shown in Figure 2, the circuit of the present invention, the commercial AC voltage introduced from the outside ( V ac ) Through the bridge diode (D1) and smoothing capacitor (C4) V i ) And supply it to the primary side of the transformer (2) to V s, V sm, V sn ) Is supplied with a DC voltage ( V o, V om, V on In the switching power supply circuit (SMPS) of the monitor which is converted into the power supply and supplied to each circuit of the monitor, the commercial AC voltage ( V ac AC voltage reduction unit 10 for receiving a voltage to reduce the input; A direct current conversion unit 20 converting the reduced AC voltage into a direct current voltage; A high voltage detector 30 outputting a high voltage detection signal when the converted DC voltage 10 is above a predetermined voltage; A gate terminal receives the high voltage detection signal, and a drain terminal and a source terminal provide the commercial AC voltage. V ac Connected to a supply line and turned on / off according to the overvoltage detection signal to V ac Junction field effect transistors (JFET11, JFET12) for supplying / blocking And diodes D11 and D12 connected in a reverse direction between the drain and source terminals of the junction field effect transistors JFET 11 and JFET 12 to block the reverse current and provide a flow path of the forward current.
    Here, the AC voltage reduction unit 10, the inverting (-) input terminal through the resistance (R12, R13) the commercial AC voltage ( V ac ), The non-inverting (+) input terminal is grounded, and the output terminal is feedback-connected to the inverting (-) input terminal through the resistor (R14), and the input commercial AC voltage ( V ac ) Is configured as a differential amplifier (OP11) for reducing the voltage.
    In addition, the DC converter 20 includes: a phase shifter for converting a phase of the AC voltage signal output from the differential amplifier OP11 by 90 °; A first multiplier1 that multiplies the signal output from the phase-shifter; And a second multiplier 2 that squares the AC voltage signal output from the differential amplifier OP11, and adds the output signal of the second multiplier 2 to the output signal of the first multiplier 1. Generate a DC voltage.
    In this case, by implementing the DC converter 20 as a phase shifter and the first and second multipliers 1 and 2, a response speed may be relatively faster than that of the smooth capacitor and the rectifier diode.
    In addition, the high voltage detection unit 30, the non-inverting (+) input terminal is connected to the contact of the output terminal of the first multiplier (multiplier1) and the second multiplier (multiplier2), the inverting (-) input terminal is a reference voltage ( V ref ) And an output terminal is feedback-connected to the non-inverting (+) input terminal through a resistor (R17), and comprises a comparator (OP12) for supplying an output signal to the gate terminal of the junction type field effect transistor (20). have.
    In addition, the junction field effect transistors JFET11 and JFET12 are implemented as P-channel isolated JFETs.
    Subsequently, the operation and effect of the circuit according to the present invention configured as described above are described. V ac ) And the common AC voltage above the rated range V ac ) Is divided into the following case.
    1. Commercial AC voltage within the rated range ( V ac ) Inflow
    Since the junction type field effect transistors JFET11 and JFET12 remain turned on in the initial state in which the gate voltage is not supplied, the commercial AC voltage ( V ac ) Is applied through the drain and source terminals of the first and second junction type field effect transistors JFET11 and JFET12 to be supplied to the bridge diode D1.
    Accordingly, the commercial AC voltage ( V ac ) Is rectified at the bridge diode D1 and smoothed at the smoothing capacitor C4 through the inrush current preventing resistor R1 to provide a direct current voltage ( V i And then to the primary winding of the transformer (2).
    At this time, the commercial AC voltage ( V ac ) Is input to the differential amplifier OP11 through a resistor to reduce the voltage by a certain level.
    A sine wave as shown in FIG. 3 (a) output from the differential amplifier OP11 sinw o t AC voltage is converted into 90 ° phase through a phase-shifter to cosine wave as shown in FIG. cosw o t The AC voltage of the cosine wave output from the phase-shifter is squared by the first multiplier 1 to form a half-wave rectified waveform as shown in FIG.
    On the other hand, the AC voltage of the sine wave (as shown in Fig. 3 (a)) output from the differential amplifier OP11 is squared by the second multiplier 2 and is a half-wave rectified waveform as shown in Fig. 3 (d). To achieve.
    At this time, if the output signal of the second multiplier 2 (as shown in Fig. 3 (d)) is added to the output signal of the first multiplier 1 (as shown in Fig. 3 (c)), DC voltage as shown in Fig. 3E is generated.
    The DC voltage output from the DC converter 20 is input to the non-inverting (+) input terminal of the comparator OP12, and the reference voltage input to the inverting (-) input terminal ( V ref ).
    At this time, since the non-inverting (+) input voltage is smaller than the inverting (-) input voltage, the comparator OP12 supplies a low level overvoltage detection signal to the gate terminals of the first and second junction type field effect transistors JFET11 and JFET12. do.
    As a result, the first and second junction type field effect transistors JFET11 and JFET12 remain turned on, and commercial AC voltages introduced from outside V ac ), The positive voltage component is supplied to the bridge diode D1 through the drain and source terminals of the first junction type field effect transistor (JFET11), and the negative voltage component is supplied to the second junction type field effect transistor ( The switching power supply circuit SMPS performs a normal operation by being supplied to the bridge diode D1 through the drain end and the source end of the JFET 12.
    2. Commercial AC voltage above the rated range V ac ) Inflow
    At this time, since the non-inverting (+) input voltage is greater than the inverting (-) input voltage, the comparator OP12 supplies a high level overvoltage detection signal to the gate terminals of the first and second junction type field effect transistors JFET11 and JFET12. do.
    Accordingly, the first and second junction type field effect transistors JFET11 and JFET12 are turned off, and commercial AC voltage introduced from the outside ( V ac ) Is not supplied to the bridge diode (D1), the switching power supply circuit (SMPS) does not perform a normal operation.
    In this case, the resistors R15 and R16 are for forming a hysteresis band.
    As described above, the present invention has the effect of protecting the monitor by blocking the supply of the commercial AC voltage by using a semiconductor having a fast reaction rate when a commercial AC voltage of more than the rated range flows into the switching power supply circuit.
    权利要求:
    Claims (4)
    [1" claim-type="Currently amended] The commercial AC voltage introduced from the outside is transferred to the DC voltage through the bridge diode D1 and the smoothing capacitor C4. V i ) And supply it to the primary side of the transformer (2) to V s, V sm, V sn ) Is supplied with a DC voltage ( V o, V om, V on In a switching power supply circuit (SMPS) of a monitor which is converted into
    The commercial AC voltage input from the outside ( V ac AC voltage reduction unit 10 for receiving a voltage to reduce the input;
    A direct current conversion unit 20 converting the reduced AC voltage into a direct current voltage;
    A high voltage detector 30 outputting a high voltage detection signal when the converted DC voltage 10 is above a predetermined voltage;
    A gate terminal receives the high voltage detection signal, and a drain terminal and a source terminal provide the commercial AC voltage. V ac Connected to a supply line and turned on / off according to the overvoltage detection signal to V ac Junction field effect transistors (JFET11, JFET12) for supplying / blocking And
    The diode of the monitor connected to the drain terminal and the source terminal of the junction field effect transistor (JFET11, JFET12) in the reverse direction, blocking the reverse current and provide a flow path of the forward current, characterized in that the monitor High voltage protection circuit.
    [2" claim-type="Currently amended] The method of claim 1, wherein the AC voltage reducing unit 10,
    Inverting (-) input terminal is the common AC voltage through the resistor (R12, R13) V ac ), The non-inverting (+) input terminal is grounded, and the output terminal is feedback-connected to the inverting (-) input terminal through the resistor (R14), and the input commercial AC voltage ( V ac The high voltage protection circuit of the monitor, characterized by consisting of a differential amplifier (OP11) for reducing the voltage.
    [3" claim-type="Currently amended] According to claim 2, wherein the DC converter 20,
    A phase-shifter for converting a phase of the AC voltage signal output from the differential amplifier OP11 by 90 degrees;
    A first multiplier1 that multiplies the signal output from the phase-shifter; And
    It is composed of a second multiplier (2) multiplier to square the AC voltage signal output from the differential amplifier (OP11), the output signal of the second multiplier (multiplier2) is added to the output signal of the first multiplier (multiplier2) A high voltage protection circuit of a monitor, characterized by generating a voltage.
    [4" claim-type="Currently amended] The method of claim 3, wherein the high voltage detection unit 30,
    A non-inverting (+) input terminal is connected to the contacts of the first multiplier1 output terminal and the second multiplier2 output terminal, and the inverting (-) input terminal is a reference voltage ( V ref ), The output terminal is feedback-connected to the non-inverting (+) input terminal through a resistor (R17), and comprises a comparator (OP12) for supplying an output signal to the gate terminal of the junction field effect transistor (20) Monitor high voltage protection circuit.
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    同族专利:
    公开号 | 公开日
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1998-09-30|Application filed by 전주범, 대우전자 주식회사
    1998-09-30|Priority to KR1019980040684A
    2000-04-25|Publication of KR20000021533A
    优先权:
    申请号 | 申请日 | 专利标题
    KR1019980040684A|KR20000021533A|1998-09-30|1998-09-30|Circuit for protecting high voltage of monitor|
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