Patent ID: 7916101
Filing Date: 2011-03-29
Classification: G09G,H05B

Abstract:
1. A light emitting diode (LED) driving apparatus, comprising: drive means for driving an LED to emit light; and control means that controls a driving current supplied from the drive means to the LED, in which the control means determines whether a target value of luminous power of the LED is smaller than a predetermined value, and when a determination result therefrom indicates that the target value is smaller than the predetermined value the control means implements luminous power control by controlling an ON/OFF ratio of the driving current, and when the determination result therefrom indicates that the target value is equal to or larger than the predetermined value the control means implements luminous power control by controlling a level of the driving current, when the control means implements luminous power control by controlling the ON/OFF ratio of the driving current, a ratio of a length of an ON period to a total length of the ON period and an OFF period equals a value obtained by dividing the target value by the predetermined value, in which luminous efficiency of the LED is obtained by dividing the luminous power by input power, and in which the predetermined value represents a luminous power value obtained from a driving current value having a highest value of the luminous efficiency of the LED, such that when the determination result indicates that the target value is smaller than the luminous power value obtained from the driving current value having the highest value of the luminous efficiency of the LED the control means implements the luminous power control by controlling the ON/OFF ratio of the driving current, and when the determination result indicates that the target value is equal to or larger than the luminous power value obtained from the driving current value having the highest value of the luminous efficiency of the LED the control means implements the luminous power control by controlling the level of the driving current, in which in the luminous power control implemented by controlling the ON/OFF ratio of the driving current, the level of the driving current is kept constant at the driving current value that provides the highest luminous efficiency of the LED.