Abstract: A power field-effect switching transistor is switched-on by charging its gate-source capacitance by connecting a capacitor thereto by means of a first transistor. Switching-off of the power field-effect switching transistor is achieved by discharging the gate-source capacitance by switching-on a second transistor. In this manner, the charging and discharging processes take place at low resistance, and therefore in a short period of time. As a result, switching times and switching power losses for the power field-effect switching transistor are minimized. In addition, the need for a separate auxiliary voltage source and inductive circuit elements is obviated.

Abstract: A free-running blocking oscillator-type converter for producing a controlled output signal. The converter is provided with a primary winding of a transformer, a switching transistor, and a resistor which are connected in series with one another between first and second input terminals of the converter. The transformer is further provided with a feedback winding which is coupled to the base terminal of the switching transistor. In some embodiments, optoelectronic coupling devices are used in a sensor arrangement for providing a control signal responsive to variations in the magnitude of the output signal of the converter. In other embodiments, such variations in the output signal of the converter are sensed by a transformer winding. Circuitry is disclosed for applying the sensor control signal selectably to the base and emitter terminals of the switching transistor.

Abstract: A circuit for protecting a semiconductor switch which connects an inductive load to a voltage supply. The switch is shunted by the series combination of a diode and a capacitor. The capacitor is connected to the input terminals of flyback converter, the converter having a control input terminal for receiving a control signal which also controls the conduction state of the semiconductor switch. The electrical energy which is provided at output terminals of the protective circuit may be advantageously returned to the voltage supply so as to reduce to a minimum the electrical energy dissipated in the protective circuit, or, alternatively, such energy may be available for any desired use, illustratively, as an auxiliary power supply.