Patent ID: 6836393
Filing Date: 2004-12-28
Classification: H02M

Abstract:
A resonance type power supply unit having a switching circuit comprising an inductive element and a capacitive element and causing a current waveform or a voltage waveform to resonate, said unit comprising:a resonance voltage detector for detecting a resonance voltage generated by said inductive element and said capacitive element; a voltage converter for converting the resonance voltage detected by said resonance voltage detector to a comparable DC voltage; a voltage comparator for comparing the DC voltage obtained by said voltage converter to a reference voltage; a switching controller for controlling a switching frequency or an on-state time interval of said switching circuit to correspond to the reference voltage in accordance with comparison output by said voltage comparator; and a reference voltage controller for changing the reference voltage; wherein said reference voltage controller gradually increases the reference voltage to a first preset value at a time of start control, and gradually decreases the reference voltage to a second preset value at a time of stop control; and wherein said switching controller stops switching in said switching circuit.