| 摘要 |
A switching power supply apparatus that can precisely control the overload protection voltage is provided. The apparatus includes a secondary current on-period detection circuit for detecting the time between turn-off of the switching device and off-timing of the secondary current; and an output power limiting circuit for comparing the output signal of the secondary current on-period detection circuit with a signal indicating a predetermined maximum secondary current on-period, and for outputting an output power limiting signal for reducing or stopping power supply to a load to a switching signal control circuit when the former signal is higher than the latter signal, wherein the maximum secondary current on-period is arranged to correspond to the secondary current on-period when the device current flowing through the switching device reaches the maximum current defined by the switching signal control circuit, or the oscillation frequency of the device current reaches the maximum oscillation frequency defined by the oscillator, and the second DC voltage from the output voltage generation circuit is released from constant-voltage control and reduced. |
