SU1339803A1 - Apparatus for controlling and protecting a voltage converter - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to devices for controlling and protecting push-pull DC-DC converters on transistors. The aim of the invention is to increase reliability, the goal is achieved by introducing a soft start unit consisting of transistor 14, capacitor 15 and two resistors 16 and 17, and switching between a driving generator 3 and selectors 8 and 9 of a differential circuit and a resistor 6, to a common point of which a varying magnitude bias voltage is applied using a pulse width modulator. The pulse-width modulation mode is performed by controlling the position of the pulses of the differential circuit relative to the trigger threshold of the selectors 8 and 9 pulses. On the same principle, a smooth start scheme is built. 1 hp f-ly, 3 ill. iS

Description

I1 3

Invention from 1-k) to converting equipment, in particular to control devices and backdrops of two act p-converters (transient voltage on a transistor) ;.

The aim of the invention is to improve reliability.

Fig. 1 shows the functional diagram of the device for controlling and constituting the voltage converter in Fig. 2, a functional diagram of the controllable current of the pulse-width modulator; Fig. 3 is a circuit diagram of a control unit of a pulse width modulator (111. 1).

The control and protection device of converter 2 contains a master oscillator 3, a shaper of 4 rectangular pulses, a differentiating circuit from a capacitor 5 and a resistor 6, a frequency divider 7, selectors 8 and 9 pulses, a trigger 10 for protection 1.1, and a photodetector 11 for overload protection, control 12 and an executive 13 pulse width modulator, a soft start circuit consisting of a transistor 14, a capacitor 15, a first resistor 16 and a second resistor 17, a power source 18. Converter 2 contains a half-bridge inverter 19 on bipolar transistors with a rectifier and a smoothing filter, element 20 is part of an overload protection circuit that includes overload current sensors (two, by the number of power switches) and an LED of an opto-coupler that is optically connected to the element 1I, which is part of the executive unit of the overload protection circuit, an additional winding 21 (with a midpoint) of the power transformer of the inverter 19, which serves to organize the protection of the power switches of the inverter 19 against through currents In this case, in the certain phase of the feedback voltage pulses, the third inputs of the selectors 8 and 9 are applied.

The control part of the pulse-width modulator has a block diagram (Fig. 2) and contains an output voltage ripple isolation circuit 22 and a reference voltage circuit 23, the output voltages of which are fed to the inputs of the operational amplifier of the comparison circuit 24. The error signal is amplified by the operational amplifier and converted to changes in current through 9803

a mobile battery 25, affecting the photodetector 13.

The ripple separation circuit contains a zener diode 26 and a resistor 27 and is connected through a resistor 28 to the inverting input of opera1, ion reference amplifier 29 (fig-3). The reference voltage circuit contains a resistor

IQ 30 and Zener diode 3, in parallel with which a trimming potentiometer 32 is connected. The reference voltage from the slider of this potentiometer is fed to the non-inverting input of the operating

15 an amplifier 29. The output circuit of the operational amplifier is formed by a resistor 33 and an LED 34 of a diode onron pair. The gain of the operational amplifier 29 is determined by the ratio of the resistors 35 and 28. The voltage supplying the operational amplifier 29 is stabilized by the elements 36 and 37. The key on the transistor 38 is the output resistor 39

The & fj base prevents the operation of the operational amplifier 29 but the time for the soft start of the voltage converter until the zener diode 26 is opened, thus achieving the independence of the operation of the soft start circuits and.

The control device works as follows.

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When you turn on the converter in the network and the voltage T. At the output of the source 18, the master oscillator 3 starts to work, and at the output of the imaging device 4, square-wave pulses appear, which follow with a doubled clock frequency. These pulses are fed to the differentiating circuit from the capacitor 5 and the resistor 6, as well as to the input of tripler 7 operating in the frequency division mode by two. From the Q and Q outputs of the tripra 7, the antiphase meander pulse sequences following the clock frequency go to the first inputs of the selectors 8 and 9. The minimum fixed pause between the output pulses of the control device is formed using elements 5 and 6, the lower circuit of the resistor 6 is connected to the common wire of the control device through the output Q of the overload protection trigger JO, since when voltage U is detected, the trigger 10 is set to the position corresponding to a logical zero on this output. A smooth start and PWM organization is achieved by supplying a variable positive bias voltage from source 18 to a common point of elements 5 and 6. A smooth start and an IC is achieved by the appearance of a voltage U, at a common point of elements 5 and 6 the bias voltage supplied through the transistor 14 and the resistor 16 and through the photodetector 13, the resistance of which varies under the action of a signal from the light emitter included in the control part 12 of the broadband modulator.

Claims (2)

Invention Formula i.The device for controlling and protecting a voltage converter supplied with a power transformer, comprising a master oscillator, a differentiating circuit, a frequency divider, the direct and inverse outputs of which are connected to the first inputs of two pulse selectors made on elements 3 OR-NOT, the outputs of which are pre-calculated for connection to the control inputs of a voltage converter, a pulse-width modulator, an input intended for connection to the output of a voltage converter, and a protection trigger, characterized by it, that in order to increase reliability, etc. introduced shaper mougolnk pulses and a soft start unit including a transistor, a capacitor and two resistors, the output from the oscillator square wave generator five ten 15 20 39803 connected to the input of the frequency divider, the output of the pulse-width modulator is connected to the output of the differentiating circuit and to the second inputs of the pulse selectors, the third inputs of which are intended to be connected to the output of the power transformer of the voltage converter, the differentiating circuit resistor is connected to the total device width via a protection trigger, while the soft start node capacitor is connected between the base and the collector of the trap ican connected to schine feeding device and the emitter and base of the transistor through first and second resistors connected to the output of the differentiating circuit. 2. A device according to claim 2, characterized in that the pulse-width modulator comprises a control unit comprising an output voltage ripple isolation circuit, a reference voltage circuit, a comparison unit at the operational amplifier and an optocoupler light emitter a unit made on an optocoupler photo-detector, the output of the output voltage ripple circuit being used as the input of a pulse-width modulator; the output of the output voltage ripple circuit is connected to the inverting input amplifier, non-inverting input of which is connected to the output circuit of the reference voltage, and the output - to the input of the light emitter of the optocoupler, while the output of the photoreceiver of the optocoupler is used as the output of the pulse-width modulator. thirty 35 40 FIG. 2 Editor G. Volkova Compiled by O. Mescher Kova Tehred M. Khodanich Korre -: Torus S.Shekmar Order 4240/5 Circulation 659 Subscription; VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab. d. 4/5 Production and golgograficheskoy predntshti, g, Uzhgorod, st. Project, 4