| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To ensure safety of traveling and obtain energy saving even if a light amount of a semiconductor lighting source is changed. <P>SOLUTION: When an input terminal 46 becomes low level by a signal for dimming an LED 16, a PNP transistor 50 becomes ON, and the voltage of a positive input terminal of an operational amplifier 52 is increased according to the time constant defined by a resister R8 and a capacitor C5. A source current I1 is supplied from the operational amplifier 52 to a current detection terminal 32 as the voltage increases. As the current value of the source current I1 is gradually increased, the current flowing in a shunt resistor R1 of a switching regulator 12 is gradually reduced, the degree of light emission of the LED 16 is gradually reduced from a full lighting state to a 70% dimming light state, and the light amount of the LED 16 is changed by 30% in 10 seconds. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
