POWER SOURCE

PURPOSE:To enhance the reliability and to reduce the size and cost by detecting both the output voltage and current of a high voltage transformer at the secondary side, and feeding back them to the primary side to control an oscillator of the primary side. CONSTITUTION:A power source 1 has a high voltage transformer T, and an oscillation transistor Tr is connected with the primary side coil N1 of the transformer T. Further, a charger load RL of a copying machine is output through a rectifier of rectifying diodes and a spark discharge preventing resistor R2 from the secondary side coil N2. In this case, an output voltage detector 6 and an output current detector 8 and comparing means 10 for comparing the both outputs are provided between the primary side and the secondary side of the transformer T and output to the controller 2 of the transistor Tr. Thus, the controller 2 increases or decreases the base current to be applied to the transistor Tr in response to the output signal from the comparing means 10 to obtain the prescribed output drooping characteristic.