| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a step-up type switching power supply of wide freedom in designing which has a power factor improving function in which the derating of a switching element is improved. <P>SOLUTION: A controlling IC41 turns on a switching element Q when a zero current detecting terminal Zcd is applied with a zero current signal. An IC operation power supply circuit 42 supplies a capacitor C2 with a voltage induced at an auxiliary coil Ls during off-period of the switching element Q, and supplies a smoothed output to an IC operation power supply terminal Vcc. A capacitor C3 is connected between the auxiliary coil Ls and the IC operation power supply circuit 42. A resistor R1 is connected between the capacitor C3 and the zero current detecting terminal Zcd. A diode D3 charges the capacitor C3 with the voltage induced during on-period of the switching element, and the charged voltage is added to the capacitor C2 during off-period of the switching element Q. An impedance circuit 45 is connected between the capacitor C3 and the zero current detecting terminal Zcd. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
