Abstract: The invention relates to a current supply apparatus in which galvanic separation between the control portion and the high voltage portion is provided and has the feature of a rapid interruption of an overcurrent upon overload, such as, short-circuiting. Control pulses for the chopper and inverter transistor thereof are fed to a base control circuit by way of an opto-coupler and the gate feedable with an appropriate blocking signal on overcurrent is disposed between the opto-coupler and the base control circuit for the chopper and for the transistor of the inverter that are connected to the current return line of the inverter.

Abstract: The invention relates to an electronic switching circuit having a power transistor controlled by a control stage. During the "on" time for the transistor a capacitor of a switch off relief circuit is charged and at "turn-off" time the capacitor is discharged through the base-emitter path of the power transistor. The charge of the capacitor is thus utilized to produce a strong base current surge during switching on of the power transistor so as to operate the power transistor rapidly and thereby reduce the power loss of its switching path.