| 摘要 |
PROBLEM TO BE SOLVED: To provide a half-bridge current-resonant switching power supply device that implements low output voltage fluctuation and output ripple and high efficiency.SOLUTION: An error amplification circuit 30 is provided for amplifying a difference between an output voltage Vo and a target voltage Vr to output a control signal Ie. A frequency modulation circuit 32 is provided for frequency-modulating the control signal Ie according to a modulation condition α to output a reference pulse Vf of a frequency F. A switching voltage monitoring circuit 34 is provided for outputting first and second timing signals Vt1, Vt2 when voltages Vd1, Vd2 of first and second main switching elements 16(1), 16(2) become equal to or lower than a predetermined value. A mode selection circuit 36 is provided for regarding the control signal Ie as an output current Io to operate, selecting a normal operation mode if the output current Io is higher than a current reference value, and selecting a skip operation mode if it is lower. A drive circuit 38 is provided for driving the main switching elements 16(1), 16(2) on the basis of the reference pulse Vf and the signals Vt1, Vt2, Vm. |
