Patent ID: 8830699
Filing Date: 2014-09-09
Classification: H02M

Abstract:
1. A control circuit of a switching power supply system wherein the switching power supply system is a flyback-type switching power supply system comprising a switching device and a transformer, in which system the switching device carries out a turning-on operation to thereby input a DC voltage, to which an AC input voltage is rectified, to the transformer to store energy in the transformer and carries out a turning-off operation to thereby release the energy stored in the transformer for outputting a specified DC voltage to a load, and the control circuit carries out control so as to decrease a switching frequency of the switching device when a load factor of the load decreases to be lower than a specified load factor, the control circuit comprising: an input voltage detection unit having the AC input voltage inputted for detecting whether the AC input voltage is a voltage of a high voltage system or a voltage of a low voltage system; and a frequency decreasing gain setting unit provided so as to switch decreasing gain characteristics of switching frequencies relative to the load factor according to a result of the detection of the AC input voltage carried out by the input voltage detection unit.