Danfoss A/s

Hans Doktor

Kjeld Hellegaard

Niels O Jacobsen

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.

Current supply apparatus for an A.C. consumer

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.

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Aarhus C, Denmark

Hans Doktor