| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply circuit of an electronic apparatus which receives commercial power, transforms and rectifies the commercial power, supplies prescribed rated power to a load, has an economically advantageous constitution, can avoid useless power consumption, and can achieve power savings without depending upon a manual operation and without employing an expensive and large scale backup circuit using a high voltage and high capacity auxiliary battery. <P>SOLUTION: A decision circuit 15 decides a connection state of a load from a value obtained by measuring a voltage drop of a power supply output end by using a voltage of a low voltage power supply PS as a reference voltage. A current applied to the load is measured from a differential voltage between both ends of a low resistance element r4 and, according to the measured value, the connection state, power supply state (operation state), etc., of the load are decided. According to the decision results, a power supply cut-off switch SW1 which is connected in series to a supply route of a commercial power supply is controlled so as to be turned off selectively. <P>COPYRIGHT: (C)2003,JPO |
