Abstract: A switching power supply, in which a series circuit consisting of a primary winding of a transformer and a controllable switch is connected with a DC power source and a secondary winding of the transformer is connected with a first voltage source outputting the voltage developed across the secondary winding during the on-period of the controllable switch and a second voltage source storing the exciting energy of the transformer during the off-period of the controllable switch by using the exciting inductance of the transformer as a current source, a series circuit consisting of the first and the second voltage sources being connected with a load. Owing to this construction, even if voltage-current characteristic of a load having constant voltage characteristic, such as a magnetron, vary due to variations in the temperature, etc., the output voltage is automatically compensated and a stable electric power can be supplied to the load.

Abstract: An inverter-type switching power supply circuit which comprises an inverter for converting the DC output of a DC power source to an AC output, a transformer for receiving the AC output of the inverter, a rectifier for rectifying the output of the transformer, a smoothing capacitor for smoothing the output of the rectifier and supplying it to a load, and a transformer short-circuiting circuit for short-circuiting either the primary side or the secondary side of the transformer. The transformer is frequency controlled such that the product of the applied voltage and time of the transformer becomes constant. Thus, the transformer can be designed to have a small size and a light weight.

Abstract: A semiconductor switching device includes a row of a plurality of switching elements connected in series. The input terminal of the input-nearest switching element and the output terminal of the output-nearest switching element are connected with the input terminal and output terminal of the semiconductor switching device, respectively. A control signal is applied to the control terminal of the output-nearest switching element. The semiconductor switching device comprises a first plurality of capacitive elements each of which is connected between the output terminal of the output-nearer switching element and the control terminal of the input-nearer switching element of the adjacent switching elements among the switching element row; and a second capacitive element connected between the output terminal and input terminal of the input-nearest switching element. At least the switching elements (S.sub.2 -S.sub.n) have insulating gates, respectively.

Abstract: A power supply apparatus for a resistance welder has an inverse-parallel thyristor circuit for constrolling the welding current. One of thyristors connected in inverse-parallel relationship is turned on by a first signal whose reference phase is established by a synchronizing signal which is based on a voltage wave form of an AC power source and the other thyristor is turned on by a second signal whose reference phase is established by a signal which is delayed half a period of the voltage wave form with respect to the first signal, so that integrals of positive and negative halves of the output voltage wave form of the inverse parallel thyristor circuit can always be made equal.

Abstract: The positive terminal of a series circuit consisting of two capacitors is connected with the cathode of a field controlled thyristor through a resistor and a transistor and the negative terminal thereof is connected with the gate of the field controlled thyristor. The junction of the series circuit is connected with the cathode of the field controlled thyristor through a thyristor. Each capacitor is charge by d.c. current. When the field controlled thyristor is intended to be turned off, the thyristor and the transistor are first made conductive and then the one capacitor is discharged through the thyristor. As a result, the field controlled thyristor is turned off. After the turn-off of the field controlled thyristor, the voltage of the other capacitor is applied to the gate of the field controlled thyristor to hold it in the blocking state.

Abstract: An apparatus for controlling the operation of an inverter which converts DC power obtained by rectification of a received AC power or DC power received from a battery which is alternatively actuated in case of an AC power supply failure or the like, into AC power. The inverter control apparatus includes a first control means which detects the output voltage of the inverter to thereby control the operation of the inverter in accordance with the detected value of the inverter output voltage. The inverter control apparatus further includes a detector for detecting variations in the input voltage of the inverter and second control means for controlling the width of the firing angle which is controlled by the first control means, in accordance with the detected value of the inverter input voltage variations, so that variations in the output voltage of the inverter may be suppressed even in the case of occurrence of variations in the input voltage of the inverter.

Abstract: A high-voltage power supply device comprising a first DC power source, a first reactor supplied with direct current from this first DC power source, a resistor connected in parallel with the first reactor, a current interrupter initially permitting circulation of the flow of current between it and the first reactor and subsequently interrupting the flow of the circulating current therethrough, at least one auxiliary reactor connected in parallel with the first reactor, a second DC power source supplying direct current to the auxiliary reactor, an auxiliary current interrupter initially permitting circulation of the flow of current between it and the auxiliary reactor and subsequently interrupting the flow of the circulating current therethrough, and a diode and switch means connected between the first reactor and the auxiliary reactor.