| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To restrain the occurrence of an overshoot and an undershoot in a semiconductor light source current. <P>SOLUTION: In a first lighting mode, an NMOS transistor 20 is turned on according to a PWM control signal having a duty ratio of 100% in response to a DRL/POS switching signal 106 of a high level. An electric current I<SB>1</SB>is supplied to a light source 14 from a DC-DC converter 16, and when switched to a second lighting mode from the first lighting mode, the NMOS transistor 20 is turned on and off according to the PWM control signal 108 having a duty ratio of 15% in response to the DRL/POS switching signal 106 of a low level, and a gain of a noninversing amplifier 58 is increased, and an output voltage Vo of the noninversing amplifier 58 is apparently increased, and voltages Vs at both ends of a shunt resistance Rs are reduced, and an electric current I<SB>2</SB>having a peak value smaller than the electric current I<SB>1</SB>is supplied to the light source 14. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
