GB930683A - Improvements in electrical circuit arrangements - Google Patents

Abstract

930,683. Automatic regulators. EVERSHED & VIGNOLES Ltd. Sept. 8, 1960 [Sept. 8, 1959], No. 30649/59. Class 38 (4). [Also in Group XXXIX] A circuit for producing a D.C. output proportional to and isolated from a low-impedance source 12 of variable D.C. input voltage or a reference potential value comprises a transformer 1 having a primary winding 2 connected through a series impedance to an A.C. source 5, a first secondary winding circuit 3 the output of which is rectified and applied in opposition to the D.C. input, and a second secondary winding circuit 4 which provides the D.C. output after rectification and capacitor smoothing. As shown in Fig. 1, the impedance in the primary circuit comprises a full-wave rectifier 6 and the circuit of a valve 20. A first secondary winding 3 is connected to a D.C. input voltage source 12 through a full-wave rectifier 11 and a second secondary winding 4 is connected to a smoothing capacitor 14 shunted by a high-leakage resistance 15 by way of a rectifier 13. In operation, the transformer secondary voltage at rectifier 11 becomes effectively equal to the voltage of the opposing D.C. input source, and the voltages across the other transformer windings likewise attain proportional values according to their respective numbers of turns. The valve circuit is optional and enables an output current to be produced in a load at terminals 23 which is proportional to the D.C. input voltage, the valve being controlled by the D.C. output from the rectifier bridge 13. A large cathode resistor 21 and a positive bias source 22 in the grid circuit are provided. As transformer magnetising current must always be present, the valve circuit includes a bias source 25 which neutralizes this current in the valve load circuit. Alternatively the load may be shunted by a resistor 24. An alternative embodiment is shown in Fig. 2 in which two transformers 1, 1<SP>1</SP> having separate circuits for D.C. input voltages from sources 12, 12<SP>1</SP>, and series-connected output circuits from windings 4, 4<SP>1</SP> provide a D.C. current output at 23 which represents the sum of the input voltages. The rectifier bridge 6 and the valve circuit is replaced in the remaining Figure by a simple impedance 7, and A.C. output voltages are obtained. Fig. 3 is a modification of Fig. 1 which uses separate winding portions 3a, 3b and 4a, 4b for the first and second secondary winding circuits respectively and half-wave rectifiers 30- 33. Separate capacitors and leakage resistors 34 -37 are provided across the two D.C. output terminals 38, 39 and with D.C. input signal at 12a, 12b of different levels, corresponding and separate half-way outputs are obtained at 38 and 39. A stabilized D.C. output voltage is obtained at terminals 42 in the Fig. 4 arrangement, a reference potential level being determined by a Zener diode 41 which becomes conductive at a multiple or submultiple of the voltage required depending on the turns ratio of windings 3 and 4. In Fig. 5 the second secondary circuit is equivalent to that in Fig. 3, and separate controlled outputs are obtained at terminals S1, S2 in accordance with the respective Zener voltages of diodes 43 and 44.