| 摘要 |
A switching power supply circuit includes a rectifier inputting and rectifying an alternating-current voltage to produce a rectified voltage; a smoothing unit smoothing the rectified voltage; a switching unit including a switching element operable to perform a switching operation; a switching drive unit operable to drive the switching element; an isolation converter transformer including primary and secondary windings with a coupling coefficient to obtain adequate zero voltage switching in an intermediate load condition; a primary-side parallel resonant circuit including a leakage inductance component and a capacitance of a primary-side parallel resonant capacitor to make the switching unit exhibit voltage resonant operation; a secondary-side series resonant circuit including a leakage inductance component and a capacitance of a secondary-side series resonant capacitor; a secondary-side direct-current output voltage producing unit producing a secondary-side direct-current output voltage by a rectifying operation; a controller stabilizing the level of the secondary-side direct-current output voltage; and a power factor improving unit intermittently blocking a rectified current due to superposition of a switching output on the output of the rectifier.
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