KR20020017383A - Protect circuit for low input voltage - Google Patents

Abstract

PURPOSE: A protection circuit for low input voltage is provided to prevent power supply from being damaged due to the high input current by cutting off the power supply at set level when low input voltage is applied. CONSTITUTION: A protection circuit for low input voltage includes coils(L2,L3), a diode(D1), a PWM circuit(100), an FET(Q3) for switching a power factor and a capacitor(C3). An auxiliary power supply includes a diode(D1) and a coil(L1) at the input terminal. An auxiliary power source circuit supplies constant power by a zener diode(D2) as an input voltage passed through the auxiliary power supply is divided by resists(R1,R2). A constant power source supply inputs the constant voltage by an FET(Q1), a zener diode(D3), and a capacitor(C1). A low voltage sensor detects a low voltage by the output of the constant power source supply. A low voltage on-off circuit controls the PWM circuit(100) by the on-off capacitor(C2) of the FET(Q2).

Description

Input Undervoltage Protection Circuits {PROTECT CIRCUIT FOR LOW INPUT VOLTAGE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low voltage protection device in a power supply, and more particularly to an input low voltage protection circuit that can protect a power supply from an input voltage lower than a rated input voltage of a power supply.

In general, since the input current increases as the input voltage decreases, the power supply field requires an input undervoltage protection circuit to prevent breakage of the power supply. As a conventional technique for this purpose, when the low voltage is input to the input as shown in FIG. 1, the power supply is converted in the pulse width conversion circuit 100 to restrict the flow of the predetermined level by driving the FET Q3. It is protected to prevent breakage. However, this method limits the input current of the power supply to the driving of the diode (D1), pulse width conversion circuit 100 and FET (Q3) when the input voltage is input. According to the limitation of the input current of the device, there is a problem that the input power of the power supply is lowered and the output power capacity is lowered. Although not shown in the drawing, the input low voltage protection circuit is applied to prevent damage by turning off the power supply at a point about 10% lower than the minimum input voltage, but the level of the input voltage at which the power supply is turned on / off is the same. Repeated on / off causes a software failure (Fail) of the system that is turned on / off by software management.

Accordingly, an object of the present invention is to provide a level difference between the input voltage point of the power supply and the input voltage point that are turned off when the input voltage is low, even if the power supply applied to the exchange, the computer, etc. is software on / off. In other words, it provides a circuit that prevents the power supply by the input low voltage from repeating on / off.

The present invention for performing the above object in the input low voltage protection circuit having an auxiliary power supply, a pulse width conversion circuit, a power element correction switching unit, and a power element correction smoothing unit, the input voltage from the auxiliary power supply unit; It consists of an input voltage sensing unit for sensing and a power on / off control circuit that controls power on / off when the input voltage is low from the sensing output of the input voltage sensing unit, even though the power supply is on / off by software. When it is low, there is a difference in the level of the input voltage point turned off and the input voltage point turned on so that the power supply by the input low voltage is not repeated on and off.

1 is a conventional current limiting low voltage protection circuit diagram

2 is a low voltage protection circuit diagram according to an embodiment of the present invention.

3 is a detailed circuit diagram of the HIC 200 of FIG.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. In the following, in adding reference numerals to the components of the angular plane, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Terms to be described later are defined in consideration of functions in the present invention, which may vary depending on the intention or custom of the user or chip designer, and the definitions should be made based on the contents throughout the present specification.

FIG. 2 is a circuit diagram according to an embodiment of the present invention, and FIG. 3 is a detailed circuit diagram of a portion shown in FIG.

An auxiliary power supply Vcc consisting of a diode (D1) and a coil (L1) from the input terminal (Vin +) at an input terminal (Vin +, Vin-) through a bridge diode (not shown), and a coil from the input terminal (Vin +) In the low voltage protection circuit comprising (L2, L3), diode (D2), pulse width conversion circuit (100), FET (Q3) and capacitor (C3) for switching power factor adjustment,

The input voltage through the auxiliary power supply Vcc is divided by the resistors R1 and R2 so that a constant power is supplied by the zener diode D2, and an FET (from the output of the auxiliary power circuit) Q1), a constant power supply for inputting a predetermined voltage by the zener diode (D3) and the capacitor (C1), a low voltage sensing unit for detecting a low voltage by the output of the constant power supply, and the output of the low voltage sensing unit And a low voltage on / off circuit for controlling the pulse width conversion circuit 100 through the capacitor C2 from on to off of the FET Q2.

FIG. 3 corresponds to the number of the peripheral connection terminals of 200 of FIG. 2 and is applied to the inputs of the input terminal 1 of the emitter of the transistor Q11 and the zener diodes D4 and D5 connected to the resistors R11 and R12. According to the voltage, the transistor Q11 is driven to output “high” or “low” for turning on / off the FET Q2 through the resistors R15 and R18, and the transistors R through the resistors R14 and R16. Maintain constant state by driving Q12).

Therefore, a specific embodiment of the present invention will be described in detail with reference to FIGS.

The DC voltage rectified by the bridge diode is applied to the input terminal (Vin +,-) to generate 380V of DC output to the output terminal (Vout +,-). Overcurrent flows due to the low voltage. The diode D1 of the auxiliary power supply Vcc supply unit and the auxiliary power supply Vcc are separated from each other so that the input voltage is turned off and the input voltage level is turned off when the input voltage is low. The auxiliary power is controlled by the control of the gate of the FET Q1 by a constant voltage value which is divided by the resistors R1 and R2 of the auxiliary power supply circuit and determined from the zener diode D2. The output of the Vcc supply portion is smoothed by the capacitor C1 through the FET Q1 and applied to the emitter of the transistor Q11 in FIG. A constant level is maintained by the zener diode D3 connected to the gate of the FET Q1, and the input level of the terminal 1, that is, the input level of the emitter of the transistor Q11 is applied to the terminals 3,4. When the level is lower than the level set by the connected zener diode D5, the transistor Q11 is turned off, the transistor Q12 is also turned off, and "low" is applied to the terminal 7 through the resistors R15, R17, and R18. Output This state is the point where the low voltage input is turned off. However, when the input of the terminal 1, that is, the level of the emitter of the transistor Q11 is higher than the level set by the zener diode D4 connected to the terminal 2, the transistor Q11 is turned on and the transistor ( Q12) is also turned on, and outputs "high" to terminal 7 via resistors R15, R17, R18. This state is the point where the low voltage input is turned on. Since the charge / discharge path of the capacitor C2 is formed by turning on / off the FET Q2 at the on / off point, the power supply is controlled by the control of the FET Q3 under the control of the pulse width conversion circuit 100. It is. Therefore, it prevents the flow of high current by turning off the transistor Q11 at the set level by the zener diode D5 when the low voltage is input, thereby protecting the power supply device, and the FET Q2 is turned on only at the on / off point. Because of this difference, the on or off according to the input undervoltage is not repeated.

As described above, when the input low voltage protection circuit is applied, the present invention prevents the power supply from being damaged by the input high current because the power supply is turned off at the set level even if the input low voltage is input, and the power supply is turned on / off. There is an advantage of stabilizing the system because there is a difference in the level so that the on / off is not repeated by the input low voltage.

Claims (4)

In the input low voltage protection circuit comprising an auxiliary power supply, a pulse width conversion circuit, a power element correction switching unit, and a power element correction smoothing unit, An input voltage sensing unit for sensing an input voltage from the auxiliary power supply unit and a power on / off control circuit for controlling power on / off when the input voltage is low voltage from the sensing output of the input voltage sensing unit are configured in software. When the input voltage is low even if the supply is turned on or off, the difference between the level of the input voltage point and the on-off input voltage point of the power supply is set so that the power supply by the input low voltage is not repeated on and off Input undervoltage protection circuit. Auxiliary power supply Vcc supply unit consisting of diode (D1) and coil (L1) from the input terminal (Vin +) at the input terminals (Vin +, Vin-) through the bridge diode, coils (L2, L3) from the input terminal (Vin +), In the low voltage protection circuit including a diode D2, a pulse width conversion circuit 100, a FET Q3 for switching power factor adjustment, and a capacitor C3, A sub power supply circuit for supplying the input voltage through the sub power supply Vcc supply voltage dividedly; a constant power supply unit for inputting a predetermined voltage from the output of the sub power supply circuit; and a low voltage by the output of the constant power supply unit. And a low voltage on / off circuit for controlling the pulse width conversion circuit (100) at an on / off point from the output of the low voltage detector. The method of claim 2, The low voltage detection unit inputs from the level set by the zener diodes D5 providing the reference level of the off point, the zener diode D4 providing the reference level of the on point, and the zener diodes D4 and D5. Input low voltage protection circuit, characterized in that consisting of a transistor (Q11) for determining the on / off point according to the difference from the value. The method of claim 2, The low voltage on / off circuit includes resistors R15 and R17 for dividing from the output of the low voltage sensing unit, a zener diode D11 for regulating the divided voltage level by the resistors R15 and R17, and the zener diode D11. Input low voltage protection circuit, characterized in that consisting of FET (Q2) on / off according to the on / off point level output by the).