CONTROLLER FOR LUMINANCE OF LED

摘要

PROBLEM TO BE SOLVED: To control so as to maintain the visibility of an LED(light emitting diode) display as much as possible while attaining a long life of LED elements. SOLUTION: The ambient temperature of an LED element 12 is detected by a temperature sensor 14 and when the luminance control circuit 16 of this controller judges that the ambient temperature exceeds a first reference temperature (60 deg.C), the controller controls so as to reduce the light emission luminance of the LED element 12 at a fixed rate by changing a duty ratio while thinning out the driving signal at a fixed rate. The controller continues a lighting control in a state in which the luminance of the element 12 is reduced until the ambient temperature of the element 12 becomes a temperature equal to or lower than a second reference temperature (30 deg.C) by detecting the ambient temperature with the sensor 14. When the ambient temperature is lowered to a temperature equal to or lower than the second reference temperature, the controller performs control so as to return the duty ratio to the original state in order to light the element 12 with a normal luminance. Moreover, when the element 12 is lighted with the normal luminance and the ambient temperature of the element 12 becomes a temperature equal to or higher than the first reference temperature, the controller repeats the control to reduce the luminance of the element 12 at the fixed rate by changing the duty ratio again.