| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a switching power supply device that implements reduced noise and stable operation. <P>SOLUTION: The switching power supply device comprises: a series circuit of a primary winding P1 of a transformer T and a switching element Q1; a control circuit for turning on/off Q1; a rectifying/smoothing circuit D, Co for rectifying/smoothing a voltage generated in a secondary winding S1 of the transformer; and an error amplification circuit OP for outputting an error voltage between an output voltage of the rectifying/smoothing circuit and a reference voltage to the control circuit. The control circuit includes a signal generation section OSC for generating a signal to turn on/off Q1, and a frequency subtracter for counting pulses of an output signal of OSC and decrementing an oscillation frequency every time the count value reaches a predetermined value, and includes a delay time switch circuit 22 for switching a delay time such that the pulse signal at the time of decrementing the frequency is delayed to control an on time of Q1. <P>COPYRIGHT: (C)2013,JPO&INPIT |
