| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable a power supply circuit driving by a constant current an LED series circuit in which a plurality of LEDs are connected in series, to be used in a plurality of LED series circuits having the different number of LEDs without changing circuit constants and components. <P>SOLUTION: An LED series circuit 851 is connected to a power conversion circuit 120 of a power supply circuit 100. The power conversion circuit 120 is drive-controlled by a control operation circuit 112 to supply a constant current to the LED series circuit 851. A voltage detection circuit 123 detects a voltage applied to the LED series circuit 851. The control operation circuit 112 determines whether or not the number of LEDs of the LED series circuit 851 is 40 or 20 based on a voltage detected by the voltage detection circuit 123. The control operation circuit 112 has a constant current value table 151 for 40 LEDs and a constant current value table 152 for 20 LEDs, selects any one of the constant current value tables 151 and 152 depending on a determination result, and performs constant current control of the power conversion circuit 120 based on the selected constant current value table. <P>COPYRIGHT: (C)2012,JPO&INPIT |
