Patent GB-1286354-A (GB)
Title: A d.c. voltage converter with stabilised output voltage
Inventor: SAUTEL AUGUSTE
IPC: H02M3/335
Filed: 1970-08-26
Abstract: 1286354 Automatic voltage control A SAUTEL and E TINTURE 26 Aug 1970 [20 Oct 1969] 41130/70 Heading G3R [Also in Division H2] A D.C. to D.C. converter having a stabilized output voltage comprises a transistor 12 which chops the current from an earthed D.C. source 10 and filter 11 to produce, via members 13---16, a reduced D.C. voltage at output terminals 103, 104 floating relative to earth, a decoupling circuit 4 which senses the stabilized output voltage and provides, with D.C. isolation therefrom, a voltage for application to a comparator 3 also supplied with a reference voltage derived from the source 10, and a pulse duration modulator 6 which is supplied by a multivibrator 5 and controlled by the comparator 6 to produce an output for varying the ratio of on to off time of the transistor 12 to maintain the output voltage at a desired value. As shown in Fig.3, the circuit 4 comprises a transistor 405 controlled by an output 416 of the multivibrator so that transistors 406, 409 are alternately made conductive to produce in the primary winding of a transformer 410 a rectangular waveform signal of the same frequency as the multivibrator, which signal is applied through the secondary winding to make transistors 407, 408 alternately conductive. These transistors control the primary winding of a transformer 411 to which is applied the voltage from terminals 103, 104, the secondary winding thus producing an alternating voltage of the same frequency as the multivibrator and having an amplitude dependent on the converter output voltage. This alternating voltage is passed to members 421-424 to produce a D.C. voltage at terminals 403, 404 for application to the base of one transistor of a differential amplifier of comparator 3, Fig.2 (not shown), the base of the other transistor of this amplifier being supplied with a reference voltage derived from a resistor and Zener diode series connected across the output of the filter 11. The modulator 6 is shown in Fig.4 and comprises a resistorcapacitor circuit 611, 612 which converts the square pulses from the multivibrator 5 into sawtooth signals for application to the base of transistor 607, subsequent amplification in transistor 608 and application to circuit members 613, 614, 609 causing pulses to be produced at the collector of the latter transistor, the width of which pulses are reversed by the transistor 610, Fig.5 (not shown). The output signal from the comparator 3 at terminal 604 varies the level of the sawtooth signals and hence the width of the pulses produced at output terminals 605, 606, which pulses are applied to the transistor 12 through a twostage transistor amplifier 7, Fig.6 (not shown). The filter 11 provides a signal to protection circuit 8, Fig.7 (not shown) which applies a signal to transistor 607 of the modulator 6 when the current through the inductance of the filter exceeds a predetermined value, this signal terminating pulse emission to the transistor 12 and operation of the converter. Circuit 8 includes a thyristor fired by a transistor, conduction of the latter and firing of the former being delayed by respective capacitor circuits.