Patent ID: 6310786
Filing Date: 2001-10-30
Classification: H02M,Y02B

Abstract:
A switching power-supply circuit comprising:rectifying and smoothing means for inputting a commercial AC power supply, generating a rectified and smoothed voltage and outputting said rectified and smoothed voltage as a direct-current input voltage;an insulating converter transformer for transferring a primary-side output to a secondary side wherein a gap is created to give a required coupling coefficient providing loose coupling;switching means including a switching device for intermittently passing on said direct-current input voltage to a primary winding of said insulating converter transformer;a primary-side resonance circuit translating an operation of said switching means into voltage resonance and comprising a leakage inductance component including at least a primary winding of said insulating converter transformer and a capacitance component including a primary-side parallel-resonance capacitor;power-factor improvement means for improving a power factor by:feeding back a switching output voltage obtained at said primary-side resonance circuit to said power-factor improvement means by way a tertiary winding formed by winding up a primary winding of said insulating converter transformer, and a series-resonance capacitor by supplying said switching output voltage to a rectified-current path; andgenerating intermittently a rectified current based on said fed-back switching output voltage;a secondary-side resonance circuit comprising a leakage inductance component including a secondary winding of said insulating converter transformer and a capacitance component including a secondary-side resonance capacitor on a secondary side of said insulating converter transformer;direct-current output voltage generation means including said secondary-side resonance circuit and carrying out operations to input and rectify an alternating voltage obtained at a secondary winding of said insulating converter transformer in order to generate a secondary-side direct-current output voltage; andconstant-voltage control means for executing constant-voltage control on said secondary-side direct-current output voltage in accordance with the level of said secondary-side direct-current output voltage.