CN2459806Y

CN2459806Y - Input over/under voltage protector

Info

Publication number: CN2459806Y
Application number: CN 00267947
Authority: CN
Inventors: 张建利
Original assignee: BEIJING TONGLIHUAN ELECTRICAL Co Ltd
Current assignee: BEIJING TONGLIHUAN ELECTRICAL Co Ltd
Priority date: 2000-12-28
Filing date: 2000-12-28
Publication date: 2001-11-14
Anticipated expiration: 2010-12-28

Abstract

The utility model relates to an input over and under voltage protector, which comprises a pulse modulation chip, wherein, the output ends of the pulse modulation chip are connected with two comparators. The output ends of the two comparators are connected with optical coupling devices. The input end of an error amplifier is connected with a power source voltage signal, the output end is connected with the positive input end of the first comparator and the negative input end of the second comparator, and the other input end of the two comparators is connected with comparative fiducial voltage. The output ends of the two comparators are connected with the input ends of the optical coupling devices. The utility model slickly uses a PWM regulating principle to perfectly combine an auxiliary power source and an input over and under voltage protective circuit, and the common ground of the protective circuit and a PWM control chip of the auxiliary power source is successfully realized. The utility model has the advantages that the circuit is simple, cost is low, and the utility model can be suffered from strong electromagnetic interference of a power conversion circuit and can not be damaged.

Description

Input overvoltage/undervoltage protector

The utility model relates to the input over under-voltage protection circuit, especially a kind of input over under-voltage protection circuit that utilizes PWM type auxiliary switching power supply to realize.

In large-scale power-supply system of modern times, generally all comprise the PWM type auxiliary switching power supply and the input over under-voltage protection circuit of promising main power conversion circuit power supply.The input voltage (exchange input and do rectifying and wave-filtering) that accessory power supply generally all directly utilizes main transformer to change circuit obtains needed VD grade through high frequency conversion; and over under-voltage protection circuit is not isolated owing to the electric pressure height that will detect and with major loop; so often will provide a current supply circuit for over under-voltage protection circuit separately; this has not only increased the complexity and the cost of accessory power supply; and this part circuit directly and power conversion circuit altogether, strong electromagnetic and damage take place easily.

In view of above-mentioned, the purpose of this utility model provides the input over under-voltage protection circuit that a kind of PWM of utilization type auxiliary switching power supply is realized, it can be simplified auxiliary power circuit and reduce cost, and also can avoid the strong electromagnetic of power conversion circuit.

The purpose of this utility model provides following technical scheme to realize:

A kind of input overvoltage/undervoltage protector comprises the pulse modulation chip, it is characterized in that: the output of described pulse width modulating chip connects two comparators, and the output of two comparators connects optical coupler, wherein:

Connect compensating circuit between the error amplifier input of pulse width modulating chip and the error amplifier output, the output of its error amplifier connects the positive input terminal of first comparator and the negative input end of second comparator, the reference voltage input terminal of pulse width modulating chip is connected with an end of three electric resistance partial pressure branch roads, another termination power ground of dividing potential drop branch road;

First, second dividing point of this dividing potential drop branch road connects the negative input end of first comparator and the positive input terminal of second comparator respectively;

The output of first and second comparators connects the input of optical coupler respectively after diode is isolated mutually.

Because the utility model has utilized the Principles of Regulation of PWM type Switching Power Supply cleverly; accessory power supply and input over under-voltage protection circuit are perfectly combined; the pwm chip of successfully having realized protective circuit and accessory power supply altogether; circuit is simple, cost is low so have, and can not suffer the strong electromagnetic of power conversion circuit and the advantage of damage.

Describe in detail below in conjunction with drawings and Examples.

Fig. 1 is the electrical schematic diagram of semibridge system conversion accessory power supply;

Fig. 2 is the utility model circuit diagram.

For solving two problems that exist in the prior art; the utility model has utilized the Principles of Regulation of PWM type Switching Power Supply cleverly; accessory power supply and input over under-voltage protection circuit are perfectly combined, and the pwm chip of successfully having realized protective circuit and accessory power supply altogether.Below in conjunction with schematic diagram this method is described.

See also the circuit of semibridge system conversion accessory power supply shown in Figure 1.Interchange is input as three phase network voltage, after rectifying and wave-filtering, obtains a stable DC voltage, through high frequency DC/DC conversion, obtains the output of two-way direct current, and one the tunnel is that main transformer changes circuit supply, and one the tunnel is the control circuit power supply of accessory power supply own.

At first how explanation realizes the sampling of AC-input voltage.

We know, in the PWM voltage-regulating system, input voltage and load variations be to the influence that output voltage causes, and are that the output by voltage error amplifier brings the variation of pulse duration to realize output voltage compensation.For typical pwm modulator SG3525, its 9th pin is the output of voltage error amplifier, so its size both reflected the size of AC-input voltage, has also reflected the size of load current.If be adopted as the output feedback of one road direct current output of SG3525 power supply as voltage-regulating system, because the control circuit power of accessory power supply itself is little and constant substantially, can think that load current is constant, like this, the voltage of SG3525 the 9th pin is just unique relevant with AC-input voltage.The utility model utilizes the sampled point of the 9th pin voltage of SG3525 as AC-input voltage just.

See also Fig. 2: the utility model comprises pulse modulation chip N4, and its output meets two comparator N1 and N2, and the output of two comparators meets optical coupler N3.Wherein:

Connect the compensating circuit that R3 and C1 form between error amplifier input 1 pin of pulse width modulating chip N4 and error amplifier output 9 pin, the output of its error amplifier connects the positive input terminal of the first comparator N1 and the negative input end of the second comparator N2, reference voltage input terminal 16 pin of pulse modulation chip N4 are connected with an end of R4-R6 three electric resistance partial pressure branch roads, another termination power ground of dividing potential drop branch road.The first dividing point VR1 of dividing potential drop branch road, the second dividing point VR2 connect the negative input end of the first comparator N1 and the positive input terminal of the second comparator N2 respectively; The output of first and second comparators connects the input of optical coupler N3 respectively after diode N4, N5 isolate mutually.

The Vf that adds to pulse width modulating chip N4 is the voltage signal for the SG3525 power supply.

When AC network was under-voltage, the error amplifier output 9 pin current potentials of N4 raise, and surpassed voltage reference VR1, and comparator N1 exports high level, drove photoelectrical coupler N3 output high level guard signal, realized the overvoltage protection of main power conversion circuit.

When the AC network overvoltage, the error amplifier output 9 pin current potentials of N4 reduce, and are lower than voltage reference VR2, and comparator N2 exports high level, drive photoelectrical coupler N3 output high level guard signal equally, realize the under-voltage protection of main power conversion circuit.

Foregoing circuit can be contained in the shell.

More than narration and embodiment for the utility model is described, are not to be used for limiting claim of the present utility model only, and therefore, the improvement of any unsubstantiality of doing based on the utility model and prior art surely belongs within the scope of patent protection of the present utility model.

Claims

1. an input overvoltage/undervoltage protector comprises the pulse modulation chip, and it is characterized in that: the output of described pulse width modulating chip connects two comparators, and the output of two comparators connects optical coupler, wherein:

Connect compensating network between the error amplifier input of pulse width modulating chip and the error amplifier output, the output of its error amplifier connects the positive input terminal of first comparator and the negative input end of second comparator, the reference voltage input terminal of pulse modulation chip is connected with an end of three electric resistance partial pressure branch roads, another termination power ground of dividing potential drop branch road;