Abstract: A first switching unit and a second switching unit are connected in series to an electric power load. A voltage supply unit, which is connected between the first switching unit and the second switching unit, supplies a voltage to the second switching unit. A determining unit determines an occurrence of a malfunction in at least one of the first switching unit and the second switching unit.

Abstract: A first switching unit and a second switching unit are connected in series to an electric power load. A voltage supply unit, which is connected between the first switching unit and the second switching unit, supplies a voltage to the second switching unit. A determining unit determines an occurrence of a malfunction in at least one of the first switching unit and the second switching unit.

Abstract: An image forming apparatus including a plurality of load units, a power supply device, and a control mechanism. The plurality of load units has an image forming mechanism serving as one of the plurality of load units and a specific load component. The power supply device has a first power source to supply a first power to the plurality of load units during a normal operation mode and to provide a second (e.g., minimal) power to the apparatus during an energy saving mode. The power supply device also has a second power source to supply a second power to the specific load component during the energy saving mode. The control mechanism changes a power mode from the normal operation mode to the energy saving mode according to at least one of an instruction for entering into the energy saving mode and satisfaction of a condition that the plurality of load units are inactivated.

Abstract: A controller for controlling a bias power source associated with, for example, a developing unit of an electrophotographic copier such that a bias voltage to be applied to the developing unit for the adjustment of image density is variable in level. The controller includes a central processing unit in which a timer/event counter is built in for delivering a trigger pulse signal to trigger the power source. In order to produce a bias voltage associated with a desired density level, the trigger pulse signal is subjected to pulse width modulation control at a period which is far shorter than an output time consant of the power source.

Abstract: A high-tension power supply applicable to an electrophotographic image recorder switches a DC voltage, boosts the switched DC voltage by a transformer, and outputs a high DC or AC voltage through a high-voltage side and a low-voltage side terminal which are connected to a secondary winding of the transformer. A diode or diodes are connected between the low-voltage side terminal and a ground terminal. An ammeter may be connected between the low-voltage side and ground terminals to measure an output current of the power supply.