| 摘要 |
<p>PURPOSE: An LED operating circuit is provided to reduce a ripple of an LED operating voltage according a change of a load current during the operation of an LED. CONSTITUTION: An error amplifier(11) outputs a voltage difference between a reference voltage(Vref) and a detection voltage(Vovp). A pulse width modulating circuit(12) generates a pulse-width modulating signal by comparing a compassion voltage(Vcomp) with a predetermined saw tooth voltage. A ripple reducing circuit(13) is operated to stop boosting by outputting a control signal(D_SW) as a fixed level signal. The ripple reducing circuit includes a comparer(13_1) and a level selecting unit(13_2). A control signal selecting unit(14) outputs the pulse-width modulating signal or a logical level signal to the control signal.</p> |
