GB566895A - Improvements in or relating to electronic voltage regulators - Google Patents

Abstract

566,895. Automatic voltage regulators. HADFIELD, B. M. June 10, 1943, No. 9313. [Classes 38 (ii) and 38 (iv)] A circuit for maintaining the voltage across a load R constant, irrespective of fluctuations in supply voltage B and changes in load current i2, and which may be used also for smoothing rectified alternating current, comprises a control valve V1 of the pentode type, the anode voltage of which is influenced by the supply voltage and load current changes and affects the grid potential of a valve V2 forming a variable impedance in series with the load and having its grid connected to the anode of the control valve. The grid circuit of the control valve includes an adjustable constant source of potential pE derived from a potentiometer Rp shunting a neon tube N connected across the supply B in series with resistances α, #, so that by adjustment of the potentiometer the load voltage may be controlled. The resistance B and a resistance γ provide, respectively, components of control grid voltage for the valve V1 which are proportional to the supply voltage and load current. Fluctuations in the values of these components are amplified by the control valve and applied with phase reversal, to the grid of V2 by the anode resistance P. Negative feed-back for V1 is provided by a cathode resistance Q to stabilize the control stage, whilst a resistance S, connected as shown and of a value equal to the product of Q with the control grid/screen grid amplification factor of V1, is provided to increase the range of output voltages of this valve by cancelling the effect of standing anode current. To improve frequency response, a condenser K may shunt resistance Q, thus making the time constants of the anode and cathode circuits of VI of the same order. The triode valve V2 may be replaced by a pentode or tetrode having its screen connected to the positive supply rail, when an independent and additional current for a constant-current load may be taken from between the anode and positive supply rail.