| 摘要 |
PROBLEM TO BE SOLVED: To provide an LED drive circuit which can make the emission luminance of an LED constant irrespective of power supply voltage fluctuation time when performing PWM drive of an LED. SOLUTION: A duty ratio setting part 20 sets a duty ratio Don according to a voltage VBAT based on a digital conversion value Da. A variability time measurement part 16 measures a time ΔT between the maximum and minimum values of a voltage VBAT based on a digital conversion value Da. A period setting part 21 changes a value of a PWM period Td when a set PWM period Td is in agreement with a variability time ΔT. A driving signal formation part 22 generates a driving signal Sd having a duty ratio Don and a PWM period Td. COPYRIGHT: (C)2009,JPO&INPIT
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