Patent ID: 6972546
Filing Date: 2005-12-06
Classification: H02M,Y02B

Abstract:
1. A power system for outputting voltage to a load by switching between power devices, comprising: a DC-DC converter for controlling an output voltage at a predetermined level, comprising an inductor, switching elements for supplying input voltage to said load via said inductor, a drive circuit that generates a drive signal for complementarily performing on/off control of said switching elements at a predetermined time ratio, and a control circuit that switches said drive circuit on or off and that controls the time ratio at said switching elements by a feedback signal based on said output voltage to said load; a pseudo-feedback-signal generating circuit that generates a pseudo feedback signal in synchronization with said drive signal of said DC-DC converter; and a series regulator that supplies said input voltage to said load after stepping down said input voltage; wherein when said load is light, the drive circuit of said DC-DC converter is switched off and voltage is supplied to said load from said series regulator; wherein when said load is heavy, the voltage supply from said series regulator is halted and the drive circuit of said DC-DC converter is switched on to supply voltage to said load; wherein when a voltage supply source to said load is switched from said series regulator to said DC-DC converter, voltage is continually supplied from said series regulator to said load for a predetermined period of time; and wherein said DC-DC converter supplies said pseudo feedback signal in place of the feedback signal to said control circuit while leaving said drive circuit off to control the time ratio at said switching elements, and when said predetermined period of time elapses, halts voltage supply from said series regulator, switches said pseudo feedback signal to said feedback signal, and starts on/off operations of said switching elements by switching on said drive circuit.