Patent ID: 8842447

Claim:
A DC power supply ( 1 ) for providing a fixed, regulated DC voltage (VCC) comprising a transformer ( 3 ; 103 ; 12 ) having a primary winding (Wp) and having an auxiliary winding (W 1 ) that is connected via a rectifier (D 1 ) to a series regulator ( 2 ), the transformer ( 3 ; 103 ; 12 ) has a second auxiliary winding (W 2 ), wherein all of the auxiliary windings have a different number of windings, a switching device ( 4 ; 104 ; 204 ; 304 ) is provided through which the series regulator ( 2 ) is connectable to one of the auxiliary windings (W 1 , W 2 ) and the switching device ( 4 ; 104 ; 204 ; 304 ) has a control signal input ( 5 ; 105 ; 205 ; 305 ) that is configured to receive a switching signal, and wherein the switching device ( 6 ) has a first transistor (Q 2 ) having an emitter-collector path that is disposed between a rectifier (D 2 ) of the second auxiliary winding (W 2 ) and the series regulator ( 2 ), a base of a first transistor (Q 2 ) is connected via a resistor (R 2 ) to a collector-emitter path of a second transistor (Q 3 ) and a base of the second transistor (Q 3 ) acts as the control signal input ( 5 ).