| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting circuit capable of suppressing temperature of a light emitting element to a heat-resistant temperature of the light emitting element or less, and precisely predicting the temperature of the light emitting element without increase in the number of components.SOLUTION: A lighting circuit 100 for a vehicle which controls lighting so that the temperature of an LED 210 is the heat-resistant temperature or less includes a storing part 18 which stores a circuit side heat resistance of itself, a light source side heat resistance of the LED 210, and the heat-resistant temperature of the LED 210. An output power which is supplied to the LED 210 is detected, a loss of itself is calculated, and an absolute temperature of itself is detected (S11, S12, S14). A product of the output power and the light source side heat resistance is subtracted from the heat-resistant temperature to provide a value, which is added with a product of the loss and the circuit side heat resistance to provide a value, which is set as a current suppression start temperature (S13). Then, when the detected absolute temperature reaches the set current suppression start temperature, suppressing of current for the LED 210 is started, and lighting control is made for the temperature of the LED 210 to be the heat-resistant temperature or less (S15, S16, S17). |
