| 摘要 |
<p>A switching power supply circuit includes: a transformer (104) having a primary winding (N1), a secondary winding (N2) and a tertiary winding (N3); a primary-side rectifying-and-smoothing circuit (103) that converts AC power to DC power then smoothes it; a secondary-side rectifying-and-smoothing circuit (106) that smoothes secondary-side power; a tertiary-side rectifying-and-smoothing circuit (107) that smoothes power from the tertiary winding; a switching circuit (108) that switches the primary winding; a pulse width control circuit (109) that controls the switching of the switching circuit; an output-error detecting circuit (110) that detects a deviation of a secondary-side DC output voltage from a reference voltage; and a ripple-voltage detecting-and-controlling circuit (171) that detects a ripple-voltage of the secondary-side DC output voltage and stop-controls the output-error detecting circuit, wherein a stop-control signal from the ripple-voltage detecting-and-controlling circuit causes the output-error detecting circuit to stop outputting, then a drive signal to the switching circuit is stopped, thus the operation of the switching power supply circuit is stopped.</p> |
