GB1339953A - Stabilized dc supply systems - Google Patents

Abstract

1339953 Controlling converters LICENTIA PATENT-VERWALTUNGS-GmbH 19 April 1971 [19 June 1970] 22717/71 Heading H2F [Also in Division G3] A stabilized D.C. supply system of the type comprising a transformer TR and rectifier bridge GL1 feeding a load RL through a thyristor TH controlled by a pulse generator IG in response to the comparison between the D.C. output voltage and a reference voltage, is arranged to provide synchronous firing over the whole load current range by ensuring that the pulse generator can only operate when the thyristor is forward biased, that is when the rectified voltage at its anode is greater than the voltage at its cathode produced by the smoothing capacitor C3. The voltage across this capacitor is sensed by a divider R7, R8, R9 which provides a signal to the base of a transistor T1 to whose emitter is supplied a reference voltage provided by a voltage dependent resistor R1 fed from the same voltage as the divider through a resistor R6. Variations in voltage across the capacitor C3 produce corresponding variations in the voltage across transistor T1, which controls the rate of firing of pulse generator IG formed by transistors T2, T3, T4 of which T3 and T4, together with the divider R3, R4, form a flipflop circuit equivalent to the known flip-flop circuit using a four layer diode. Transistor T2 acts as a voltage controlled resistance to vary the charge rate of a capacitor C2 in accordance with the voltage across transistor T1, the drive voltage for the generator and the charging current for capacitor C2 being obtained through a diode GL2 which conducts only when the thyristor TH is forwardly biased. When the voltage across capacitor C2 reaches a predetermined value, transistors T3 and T4 become conductive to fire the thyristor TH, the subsequent immediate discharge of capacitor C2 causing transistors T3 and T4 to be cut off. Protective elements C4, R10 and GL3 are provided. Comparison is made, Fig. 2 (not shown) of the operation of a prior art stabilized D.C. supply, Fig. 1 (not shown) with that of the described embodiment expressed in simplified form, Fig. 3 (not shown).