Lighting control circuit for vehicle lighting equipment

摘要

This disclosure relates to protecting a switching regulator by sensing immediately a change in an input voltage when the input voltage of the switching regulator is changed suddenly. When an input voltage of a switching regulator 12 is changed suddenly and an interrupt request signal IRQ is provided from an input voltage sensing circuit 16 while electromagnetic energy accumulated in the switching regulator 12 is discharged to an output block 14 by turning ON/OFF a switch SW 1 in accordance with a switching signal generated by a microcomputer 18 , to control a lighting of an LED 1 , the microcomputer 18 reduces an ON duty of the switching signal provided to the switch SW 1 in response to the interrupt request signal IRQ and limits an increase of a peak value of a current flowing through a primary side of the switching regulator 12.