| 摘要 |
<P>PROBLEM TO BE SOLVED: To control the current of a semiconductor light source according to the temperature in a lamp without using a temperature sensor. <P>SOLUTION: When a current to light emitting diodes LED1-LEDn is controlled by a D.C./D.C. converter 24, the temperature of the light emitting diodes LED1-LEDn is calculated by introducing an LED temperature detection signal 112 in a microcomputer 28; a value for derating the LED current is set based on the calculated temperature and a temperature control line 204; a control signal for derating the LED current is generated in a control circuit 26 based on the set value and the LED current obtained from a current detection feedback signal 104 to control a switching operation of an NMOS transistor 62; and a derated current is supplied to the light emitting diodes LED1-LEDn from the D.C./D.C. converter 24. <P>COPYRIGHT: (C)2009,JPO&INPIT |
