| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-efficiency switching power supply circuit which is capable of precisely performing a constant current control of an output current against fluctuations in input voltage or output voltage in spite of a simple circuit configuration. <P>SOLUTION: A switching power supply circuit 1 includes: a step-down converter circuit section 2; a switching control circuit 3; a current detection circuit 4; a reference voltage generation circuit 5; a comparator 6; an auxiliary winding 8 coupled to an inductor L1 and detecting a voltage proportional to a voltage applied to the inductor L1; and a zero-voltage detection circuit 9 which, if a polarity of an auxiliary winding voltage when a switching element Q1 is in an on-state is defined as a negative voltage, inputs the auxiliary winding voltage outputted from the auxiliary winding 8 and outputs a turn-on signal for turning on the switching element Q1 to the switching control circuit 3 when the auxiliary winding voltage reaches a threshold voltage around the zero volt from a positive voltage. <P>COPYRIGHT: (C)2012,JPO&INPIT |
