Patent attributes
A DC power source device comprises a MOS-FET 5 which performs the intermittent switching operation for converting DC input from a DC power supply 1 into high frequency electric power; a control circuit 9 for turning MOS-FET 5 on and off; and a rectifying smoother 6 for converting the high frequency electric power through MOS-FET 5 into a DC power output supplied to a load 50. Control circuit 9 comprises an output current controller 11 for controlling the on-off term of MOS-FET 5 to make DC output current IO through load 50 settle toward a rated value IOMAX; a shunt regulator 24 for receiving a drive current ISH supplied from rectifying smoother 6 and producing a reference voltage VR1 to regulate the rated value IOMAX of output current controller 11; and a constant current source 32 for keeping drive current ISH on a substantially constant level under the rated output current value condition and reduced output voltage condition. Constant current source 32 functions to supply shunt regulator 24 with minimum drive current ISH to maintain reference voltage VREF on a constant level under the reduced output voltage, and also to control drive current ISH to shunt regulator 24 to a necessary but minimum level under the rated value of DC output current.
