KR100193632B1 - Overvoltage Lockout Circuits for Switching-Mode Power Supplies - Google Patents

Abstract

The present invention relates to an overvoltage protection circuit of a switched mode power supply (SMPS).

The overvoltage protection circuit includes a fuse in a switching mode power supply (SMPS) power supply circuit that selects a first AC power supply and a second AC power supply having a higher level value than the first AC power supply to be one input power supply. AC input unit for shaping and outputting the first or second AC power input from the outside, rectifying and smoothing the AC power output from the AC input unit and converting to DC power, and outputting the rectifying and smoothing A voltage switching switch element for selecting a voltage-division ratio corresponding to the first or second AC power by switching a negative output signal, and sensing an input power of the AC input unit inputted through the switch element to direct current. And an overvoltage blocking control unit for converting and supplying the fuse to the fuse of the AC input unit.

Description

Overvoltage Lockout Circuits for Switching-Mode Power Supplies

1 is a circuit diagram of a conventional switched mode power supply.

2 is a circuit diagram of a switched mode power supply according to the present invention.

* Explanation of symbols for main parts of the drawings

10: AC input unit 20: AC rectification and smoothing unit

30: overvoltage cutoff control unit VS: voltage changeover switch

40: discharge unit 50: power conversion unit

C1-C6: Capacitor R1-R4: Register

F1: fuse BD1: bridge diode

ZNR1: Varistor RT1: Service Site

D1: Diode T1: Transformer

LF: Line Filter

The present invention relates to an overvoltage cut-off circuit of a switching mode power supply (SMPS), and more particularly, when an AC input voltage higher than the set AC input voltage is applied, it is immediately induced and converted into an overcurrent to be applied to a fuse. An overvoltage blocking circuit of a switched mode power supply (SMPS) that can be protected.

Recently, SMPS is widely used as a power supply device for electronic devices. The reason is that SMPS converts one DC or AC power supply to generate various supply voltages and supplies them to the required circuits.

This SMPS is equipped with a voltage changeover switch. In other words, in Korea, 110V and 220V are used at the same time, so the user switches the voltage switching switch depending on the electronic product.

1 is a circuit diagram of an overvoltage blocking circuit of a conventional SMPS.

Referring to FIG. 1, the conventional overvoltage blocking circuit of the SMPS is composed of a capacitor (C1-C3), a line filter (LF), a fuse (F1), a servicer (RT1) 110V or 220V AC input power applied AC input unit 1 for shaping and outputting a voltage, and a bridge diode BD1 rectifying and smoothing the output voltage of the AC input unit 1 to output a DC voltage signal, and a capacitor ( C4, C5, the discharge part (3) for charging and discharging the output signal of the rectifying and smoothing part (2) to the set capacity, and is installed between the rectifying and smoothing part (2) and the discharge part (3) To the voltage switching switch (V / S) for dividing the total output voltage of the discharge section 3, and the resistors R1-R4, the varistors ZNR1, ZNR2, the diode D1, and the capacitor C6. And a power converter 4 for converting the voltage output from the discharge unit 3 to the set level and supplying the voltage to the primary side of the transformer T1. .

The operation of the overvoltage blocking circuit of the conventional SMPS having the above configuration will be described below. If the home appliance is dedicated to 110V and the voltage switch V / S is shorted and 110V power is supplied to the AC input unit 1, both input terminals L and N of the AC input unit 1 are connected. AC voltage of 110V is applied.

This AC voltage is shaped while passing through the line filter LF, and the voltage across the capacitors C4 and C5 is changed by the rectification of the bridge diode BD1. Is applied twice as much. At this time, the voltage applied to each of the varistors ZNR1 and ZNR2 allows the capacitance of the varistors ZNR1 and ZNR2 to be selected within the allowable AC input voltage range. The margin is set to give a margin of about 10-20%. Subsequently, input voltages passing through the varistors ZNR1 and ZNR2 are applied to the primary side of the transformer T1, and are supplied as voltage signals of various levels on the secondary side, which is not shown in the figure.

On the other hand, if the user applies 220V to the AC input unit 1 without changing the voltage changeover switch (V / S) to the open state (off), the input voltage of 220V Since the voltage multiplied is supplied, the voltage across the capacitors C4 and C5 of the discharge section 3 is relatively Rises by a factor This causes the voltage across the varistors ZNR1 and ZNR2 to exceed the allowable margin. Accordingly, the short circuit (ON) of the varistors ZNR1 and ZNR2 progresses due to the overvoltage, and the overcurrent is supplied to the AC input unit 1 so that the fuse F1 is opened.

However, the conventional SMPS overvoltage blocking circuit has a problem in that the entire SMPS circuit is not quickly protected from overvoltage due to the time when the DC voltage generated in the bridge diode BD1 is charged to the capacitors C4 and C5.

An object of the present invention is to solve the above problems, when the overvoltage AC power is applied to the overvoltage blocking circuit of SMPS that can supply rectified and smooth DC current quickly to the fuse provided in the AC power input terminal It is to provide.

In order to achieve the above object, the present invention provides a switching mode power supply (SMPS) power supply circuit that selects a first AC power supply and a second AC power supply having a higher level value than the first AC power supply and uses one input power. AC input unit having a fuse and configured to output the first or second AC power input from the outside; A rectifying and smoothing unit for rectifying and smoothing the AC power output from the AC input unit and converting the AC power into a DC power source; A voltage switching switch element that is controlled to be switched to a user and selects a voltage division ratio corresponding to the first or second AC power source; And it is characterized in that it consists of an over-voltage cut-off control unit for detecting the input power of the AC input unit input through the switch element to convert the DC current, and then supply to the fuse of the AC input unit.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration, operation and effects of the present invention.

2 is an overvoltage blocking circuit diagram of an SMPS according to the present invention.

Referring to FIG. 2, the overvoltage blocking circuit of the SMPS according to the present invention includes a capacitor C1-C3, a line filter LF, a fuse F1, and a servicer RT1 of 110V or 220V. AC rectification and smoothing unit 20, which is composed of an AC input unit 10 for shaping and outputting an AC input power and a bridge diode BD1, rectifies and smoothes the output voltage of the AC input unit 1, converts the DC voltage signal, and outputs the DC voltage signal. And a voltage changeover switch (V / S) and a voltage changeover switch (V / S) for switching the output signal of the rectifying and smoothing unit 20 to select a divided voltage ratio corresponding to the AC input power sources 110V and 220V. S) is short-circuited and detects the input power of the AC input unit 10 is changed into a DC current, and then the overvoltage cut-off control unit 30 to supply to the fuse (F1) provided in the AC input unit 10, and the overvoltage blocker A discharge unit 40 charged and discharged at predetermined time intervals of the output signal of the fisherman 30, and All changes the voltage to be discharged at 40 to a set level comprises a power converter 50 for supplying the primary side of the transformer (T1).

Hereinafter, the operation of the SMPS overvoltage blocking circuit according to the present invention having the above configuration will be described. The user is a home appliance equipped with an SMPS overvoltage cut-off circuit according to the present invention is 110V only, so that the voltage switching switch (V / S) is short-circuit (on), both input terminals (L, N of the AC input unit 10) Apply AC input power. The AC input power passes through the line filter LF, its waveform is shaped, rectified and smoothed through the bridge diode BD1, and converted into a DC input power and output. At this time, the voltage at both ends of the varistor ZNR1 Since it is set in advance as the capacity value that allows the double value, it operates safely without any problem.

In this case, if 220 V is applied to both terminals L and N of the input power terminal 10 without changing the voltage change switch V / S due to inadvertent use, the DC voltage through the bridge diode BD1 is increased. Since it is immediately induced at both ends of the ZNR1, an overcurrent flows to the fuse F1 of the AC input terminal 10 in a shorted state.

Accordingly, the fuse F1 is opened quickly and the internal circuit of the entire SMPS is protected from overvoltage.

That is, since the circuit is configured to have a structure having a faster response speed than the conventional SMPS overvoltage blocking circuit, it is possible to provide a more reliable SMPS overvoltage protection circuit.

Claims (4)

A switching mode power supply (SMPS) power supply circuit that selects a first alternating current power supply and a second alternating current power supply having a higher level than that of the first alternating current power supply and serves as one input power supply. An AC input unit configured to output the first or second AC power supply; A rectifying and smoothing unit for rectifying and smoothing the AC power output from the AC input unit and converting the AC power into a DC power source; A voltage switching switch element controlled by a user and configured to select a voltage-division ratio corresponding to the first or second AC power supply; And an overvoltage blocking control unit configured to sense input power of the AC input unit input through the switch element, convert the DC power into a DC current, and then supply the fuse to the fuse of the AC input unit. The overvoltage blocking circuit of claim 1, wherein the first AC power source is 110V and the second AC power source is 220V. The overvoltage blocking circuit of claim 1, wherein the overvoltage blocking unit comprises one varistor. The switching device of claim 1, wherein the first AC power is selected by the user when the switch element is in a short circuit state, and the user is selected by the user when the switch element is in an open state. Overvoltage blocking circuit of mode power supply.