| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an LED driving device capable of driving an LED so as to keep the luminance constant without using a constant current circuit even if there is a variation in power supply voltage. <P>SOLUTION: The LED driving device is provided with an LED L1 and a switching element Tr1 which are connected in series to a power supply V<SB>H</SB>having a predetermined voltage, a control means for controlling the LED L1 so as to emit light giving predetermined luminance by outputting a PWM driving signal having a predetermined duty ratio to the switching element Tr1 to carry out duty driving in response to an input of a lighting instruction signal, a voltage measurement means 8, 1 for measuring the voltage value of the power supply V<SB>H</SB>, and a voltage duty-ratio varying means 6, 1 for varying the predetermined duty ratio in accordance with the measured voltage value. The control means 1 controls the LED L1 to emit light giving constant luminance irrespective of a variation in the power supply voltage by driving the switching element Tr1 with the PWM driving signal having the duty ratio varied by the voltage duty-ratio varying means 6, 1. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
