| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting tool drive circuit for vehicles capable of appropriately performing current derating.SOLUTION: A lighting tool drive circuit 1 for vehicles comprises: a load 100 obtained by connecting a plurality of semiconductor light-emitting elements in series; an output voltage and current detector 12 detecting an output voltage and an output current supplied to the load 10; a power setting part 16 setting an instruction value of power to be supplied to the load 10; a divider 18 dividing the instruction value of power that is set by the power setting part 16 by the output voltage detected by the output voltage and current detector 12 to calculate an instruction value of current; a PWM controller 24 generating a PWM signal depending on the smaller one of a current setting value that is preliminarily set for lighting the load 10 and the instruction value of the current calculated by the divider 18; and a DC/DC converter 26 converting power from a power supply depending on the PWM signal generated by the PWM controller 24. |
