CONTROL CIRCUIT OF DC-DC CONVERTER, DC-DC CONVERTER, POWER SUPPLY VOLTAGE SUPPLYING SYSTEM AND POWER SUPPLY VOLTAGE SUPPLYING METHOD

摘要

PPROBLEM TO BE SOLVED: To provide a control circuit of a DC-DC converter, or the like, which prevents localization of switching operations when a light load is connected, and improves power conversion efficiency. PSOLUTION: An oscillator OSC outputs a reference clock signal RCK. A switching duty control circuit 14G controls an on-duty of a transistor FET1 in accordance with an output voltage. An operation frequency control circuit 12G divides the frequency of a reference clock signal having negative correlation with the output voltage and to be inputted, to generate a control clock signal. When it is determined that the load is in a high load state, the reference clock signal RCK is outputted from a switching control circuit 16G, and when it is determined the load is in a low load state, a control clock signal PCK is outputted. A conduction control circuit 17G controls transistors FET1 and FET2 depending on the reference clock signal RCK or the control clock signal PCK. PCOPYRIGHT: (C)2009,JPO&INPIT