| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a current detection circuit of a step-up converter used for power factor improvement in a switching power supply device, capable of being incorporated in an IC, and being small in size. <P>SOLUTION: A current detection circuit 32 for a step-up converter 31 has: a current transformer 20 detecting a current flowing between an inductor 5 and a switching element 6; a current-to-voltage converter 22 converting a current Ia detected by the current transformer 20 into a voltage Va; and a current detection signal generation circuit 23 having a capacitor, and configured so that the capacitor is charged by the voltage Va outputted from the current-to-voltage converter 22 to hold the voltage during a time period in which the switching element 6 is turned on, and the capacitor is discharged by a current depending on a difference voltage between a voltage of a pair of step-up voltage output terminals 29 and a voltage between a pair of output terminals of a rectification device 2 during a time period in which the switching element 6 is turned off, and a voltage of the capacitor is outputted as a current detection signal Va_ave over the on time period and the off time period of the switching element 6. <P>COPYRIGHT: (C)2012,JPO&INPIT |
