Abstract: A voltage-type self-commutated conversion system including a voltage-type self-commutated power converter with a plurality of anti-parallel circuits of a self-turn-off device and a diode. DC terminals of the power converter are connected to DC bus lines of the voltage-type self-commutated conversion system. The voltage-type self-commutated conversion system further includes a DC capacitor connected between the DC bus lines, a transformer connected between an AC system and AC terminals of the power converter and a control circuit for controlling the power converter.

Abstract: An inverter device includes an input power-factor improving circuit which causes part of a high frequency output of an inverter circuit to feedback, through an impedance element forming at least part of two oscillatory systems, to a rectified output end of a rectifier, and a high-frequency current supply to the rectifier to be made substantially over entire range of an AC source voltage, and a control means operates the inverter circuit at a fixed frequency for attaining the two oscillatory systems in which the output supplied to a load is substantially equalized, whereby ripple component giving ill influence on the load can be remarkably reduced.

Abstract: A step-down circuit for power supply voltage, which converts an external power supply voltage into a first voltage that is lower than the external power supply voltage so as to apply it to an internal circuit, is provided with: a reference voltage generation circuit for generating a reference voltage from an external power supply voltage, a differential amplification circuit for releasing a difference between the reference voltage and the first voltage as a control signal, a driving circuit for controlling a driving current to be supplied to the internal circuit according to the control signal from the differential amplification circuit, a signal generation circuit for releasing a detection signal by detecting an increase of consumption current in the internal circuit, and a control means for controlling the driving circuit so as to increase the current to be supplied to the internal circuit in accordance with the detection signal from the signal generation circuit.

Abstract: A system controls a transformer having a primary coil. A pulse is applied to an inverter associated with the primary coil, whereby a leading edge of the pulse creates in the primary coil a tank circuit current of an initial polarity in a tank circuit inherent to the transformer. The tank circuit is seen from an effective inductance in series with the primary coil, the effective inductance including a leakage inductance of the primary coil, and an effective capacitance in parallel with the primary coil, the effective capacitance including a parasitic capacitance of the transformer. A trailing edge of the pulse occurs when the tank circuit current is different from the initial polarity.