Abstract: A rectifier using a semiconductor active element as a rectifying element is connected through an overvoltage protection circuit to a terminal voltage comparator for comparing the input voltage and the output voltage thereof. A pulse control circuit is connected to the control terminal of the active element for controlling the same in response to the output from the terminal voltage comparator. Thus, the rectifier can operate at high frequencies with a high degree of efficiency.

Abstract: In a DC-DC converter of the type in which an inductance stores energy when a main switching transistor is turned on and releases the stored energy when the main switching transistor is turned off, a semiconductor active element is used as a flywheel element which is turned off when the main switching element is turned on, but is turned on to provide the path for the current established by the release of the stored energy, and the signal which is substantially in synchronism with the switching operation of the main switching transistor is applied to the control terminal of the semiconductor active element so as to cause it to turn on and off.

Abstract: In a DC--DC converter of the type in which an inductance stores energy when a main switching transistor is turned on and releases the stored energy when the main switching transistor is turned off, a semiconductor active element is used as a flywheel element which is turned off when the main switching element is turned on, but is turned on to provide the path for the current established by the release of the stored energy, an auxiliary diode is connected in parallel with the semiconductor active element and in the same forward direction, and the signal which is substantially in synchronism with the switching operation of the main switching transistor is applied to the control terminal of the semiconductor active element so as to cause it to turn on and off.

Abstract: A rectifier in which a semiconductor active element, which is a rectifying element, and a diode are connected in parallel in the same direction so that the degradation in rectifying efficiency due to the delay in rise time of voltage when the active element is turned on can be avoided.