GB819530A - Improvements in or relating to control circuits for gas-filled valves - Google Patents

Abstract

819,530. Rectifying. BROD, S. Sept. 23, 1957 [June 27, 1956], No. 19939/56. Class 38 (2). The conductivity of a gas-filled valve Vl through which half-wave rectified current is supplied to load L from A.C. source S1 is controlled by the voltage across capacitor C connected to its grid. When triode V2 is non-conductive capacitor C is charged from D.C. source S2 through resistor R to make the grid of V1 positive so that this valve conducts over most of each positive half cycle. When triode V2 is made conducting during the negative half cycles by a variable control voltage S3 applied to its grid, capacitor C is charged negatively to an extent determined by the voltage S3. During each positive half cycle the capacitor discharges through resistor R and source S2 until the grid of valve V1 becomes sufficiently positive for that valve to conduct. The instant of conduction is thus determined by the value of control voltage S3. In modifications the two gas-filled rectifiers are connected in bi-phase and are controlled together by two triode sections in one envelope (Fig. 2, not shown) or by a single triode, interaction between the gas-filled valves being prevented by rectifiers (Fig. 4, not shown). In another modification two valves are independently controlled to vary both the direction and magnitude of the load current (Fig. 3, not shown). By connecting capacitor C and resistor R in parallel between the source S2 and the grid (Fig. 5, not shown) or between source S2 and the cathode, Fig. 6, the internal resistance of source S2 does not effect the RC time constant when C is discharging. In the circuit of Fig. 6 current from S1 does not flow through S2. In the arrangement of Fig. 7 triode V2 is replaced by a variable resistor RV in series with a rectifier G3.