Abstract: The present invention describes a charging circuit for energy storage capacitors which is especially useful in charging the energy storage capacitors used to provide the voltage supply of flashlamps in photocopying machines. The charging circuit has two series-connected d.c. converters and a current limiting device. The current limiting device has a measuring circuit for determining the current through the second d.c. converter, which is related to the output current of the first converter, and a regulating circuit for regulating the output current of the first d.c. converter and thus indirectly regulating the output current of the second d.c. converter.

Abstract: A temperature-sensitive element on a rotatable drum of a copying machine changes a characteristic in response to a temperature on said drum. The characteristic is employed to control a temperature signal. The temperature signal from the drum is connected to stationary portions of the copying machine through sliding contacts. A control circuit responds to the temperature signal to control the energization of a heater to maintain the temperature of the drum at a predetermined value. The temperature signal and the control circuit complement each other to avoid errors caused by changes in resistance in the sliding contacts. In one embodiment, the temperature signal is a controlled current, independent of resistance in series with it, and the control circuit measures the current.