| 摘要 |
PURPOSE:To control temperature of an LED array constant even through a lighting condition of the LED array is varied by a method wherein an electric power control means adds electric power to be obtained by subtracting electric power of the LED array detected by an electric power detection means from standard electric power to a heating means. CONSTITUTION:A current value flowing to an LED array 32 is detected with a current value detection circuit 56, and successively a mean current value is obtained with an integral circuit 56. Thereafter, this means current value is converted to an electric power value with an amplifier circuit 57. Then, the estimated electric power value is subtracted with a next subtracting circuit 58 from standard electric power indicating total consumption electric power value of the LED array 32 and a heater 51 which is established with a standard electric power establishing circuit 54, and the electric power value obtained by subtraction is given to a heater driving circuit 59 as a control signal. Then, electric power varied according to the subtracted electric power value is given to the heater 51. Thereby, in the case where a lighting condition of the LED array and ambient temperature are varied, temperature of all LED arrays can be always conformed to one another. |
