Patent ID: 7728530
Filing Date: 2010-06-01
Classification: H05B

Abstract:
1. LED driving circuit including a power switch and a current sampling unit for sampling LED operating current, said circuit further comprising: a voltage comparison unit for comparing the voltage obtained by the current sampling unit with the voltage of a first reference voltage source; an input voltage sampling unit for converting the sampled input voltage into a current signal; a timing unit for controlling the off-time of the power switch based on the magnitude of the input voltage collected by the input voltage sampling unit, wherein the timing unit further includes a timing capacitor that is connected in series with the input voltage sampling unit and then grounded, a timing switch connected in parallel with the timing capacitor, and an operational amplifier, the inphase terminal of which is grounded via a second reference voltage source and the outphase terminal of which is connected between the input voltage sampling unit and the timing capacitor; and a logical unit for controlling the power switch by means of a power switch driving unit, based on the comparison of the voltage comparison unit and the output signal of the timing unit, and for controlling the timing switch in the timing unit.