| 摘要 |
A switching power supply circuit is provided to reduce a switching noise by performing a soft switching operation based on a voltage resonant converter. A rectifier(Di) receives an AC voltage and rectifies the AC voltage. A smoothing unit(Ci) includes a smoothing capacitor and smooths the voltage rectified from the rectifier(Di). A switching unit(Q1) receives the rectified voltage as a DC input voltage and performs a switching. A switching driving unit drives a switching unit(Q1). An insulated converter transformer(PIT) includes a first coil which provides a switching output generated from the switching operation of the switching unit, and a second coil which induces an AC voltage by a switching output acquired from the first coil. A first side parallel resonant circuit(Cr) includes a leakage inductance element having a first winding wire of the insulated converter transformer(PIT), and a capacitance of the first side parallel resonant capacitor. The first side parallel resonant circuit(Cr) provides a voltage resonant operation as an operation of a switching unit(Q1). A second side series resonant circuit(C2) connects a second series resonant capacitor to a second winding wire of the insulated converter transformer(PIT) in series. A second side DC output voltage generation unit receives an AC voltage induced from a second winding wire of the insulated converter transformer(PIT), and generates a second DC output voltage by performing a rectifying operation. A controller stabilizes a level of the second DC output voltage by providing the switching driving unit with a detection output based on a level of the second side DC output voltage. A power factor improvement unit(10) includes a power factor improvement element which breaks interruptedly the rectified current by overlapping the switching output with the rectified output generated from the rectifying operation of the rectifier(Di). |
