Patent GB-1192628-A (GB)
Title: Improvements in or relating to Electrical Circuits Employing Semiconductor Devices
IPC: H02M3/338
Filed: 1967-10-02
Abstract: 1,192,628. Semi-conductor oscillators using charge storage effects. INTERNATIONAL BUSINESS MACHINES CORP. 2 Oct., 1967 [14 Oct., 1966], No. 44716/67. Heading H3T. [Also in Division H2] In a free running oscillator circuit diodes 50, 58 are coupled between the base and emitter regions of semi-conductor devices 42, 40 for permitting injection of minority carriers into the collector regions and potential applying means is provided for alternately effecting injection and forward conduction into the semi-conductor devices. In a converter which supplies a load via diodes 46, 54 the conduction of the transistors 40, 42 is controlled by charge storage within those transistors. Consider transistor 40 as having an accumulation of charge in its collector region; transistor 40 becomes conductive and current flows in winding 51. This induces a current in the secondary winding 52 which turns on diode 54 and supplies current through inductor 56 to the load. When the carriers have been removed from transistor 40 it turns OFF and current continues to be circulated in the secondary winding due to the energy stored in the inductance 56. A current is then induced in the primary winding 49 which causes a current to flow via diode 50 and the base-collector diode of the transistor 42 so as to inject minority carriers into the collector region of the transistor 42 and the operation is then similar to that for transistor 40. The converter may be started by injecting a pulse to the anode, e.g. 55 of either diode 46, 54 or to the base of either transistor 40, 42. The inductance of the transformer 45 may provide sufficient inductance so that the inductors 48, 56 may be removed. A saturable reactor (85), Fig. 6 (not shown), may be used to effect frequency control of the secondary windings. The frequency of the converter may be varied by connecting a constant current source (64, Fig. 5, not shown), between the anodes of the diodes 50, 58 (66, 65) and the emitters of the inverter transistors (60, 61) and diodes (71, 72) are provided to clamp the collector voltage and protect the emitter-base junctions from excess reverse voltages. PNP transistors can be used instead of the NPN shown or combinations of PNP and NPN may be used. In an alternative converter having two series connected transistors 100, 108, Fig. 7) energy stored in an inductance 101 in the primary or secondary windings of the output transformer 105 inject alternately charge carriers into the transistors and a capacitor 102 which is charged while one of the transistors 100 is conducting discharges through the other transistor 108 to removed its charged carriers. A control current generator (64 as in Fig. 5, not shown) can be used in the base circuit of these transistors 100, 108. In a further circuit (Fig. 8) for providing high frequency output power, consider transistor 150 to have stored minority carriers, this transistor conducts to provide an output via diode 161 or 162 and biases, via transformer 158, a transistor 152 so that it is able to store charge under control from an amplifier 155 which permits direct control of the average current output. When the charge has been removed from 150, transistor 152 begins forward conduction due to the stored charge and causes a current through the winding 159 to charge the capacitor 146 and store minority carriers in transistor 151. When the stored charge has been removed from transistor 152 it turns off and capacitor 146 discharges via the primary 148 and removes the stored charge in transistor 151. Energy from inductor 158 is then supplied via winding 156 to charge capacitor 145 and effect minority carrier storage in transistor 150. As the energy in inductor falls to zero the transistor 150 conducts to remove the stored charge and the above sequence is repeated.