| 摘要 |
PROBLEM TO BE SOLVED: To provide an insulated switching power supply control circuit that is small and the output change of which is minimal with respect to load fluctua tion. SOLUTION: This circuit is provided with an output control circuit 32, that comprises a reference triangular-wave voltage generating circuit, to which a timing capacitor CT for generating reference triangular waves is connected and a comparator that compares the reference triangular-wave voltage with a first output voltage information signal VFB fed back from the output of a power supply via a photocoupler PC1 for controlling of an output voltage and generates control pulse signals. Also, a discharge current control circuit is incorporated that has the functions of locking the control pulses to the 'off' state during the fall time of the reference triangular waves and of extending the minimum 'off' time by reducing the discharge current of the timing capacitor CT, when a second output voltage information signal VF, an average voltage of the control pulses, becomes equal to or lower than a given value. Furthermore, a bias circuit 25 is provided for increasing the second output voltage information signal VF to a given value or larger during the period, when at least the first output voltage information signal VFB is outputted.
|
