Patent ID: 8513904
Filing Date: 2013-08-20
Classification: H05B

Abstract:
1. A light-emitting diode (LED) driver circuit configured to receive an input voltage and to supply a current to drive one or more LEDs, the LED driver circuit comprising: a current sense device coupled between the input voltage and an anode terminal of the LED; an inductor coupled between the cathode terminal of the LED and a first node; a switch coupled between the first node and a ground potential, the switch being controlled by a control signal; a freewheeling diode having an anode terminal connected to the first node and a cathode terminal connected to the input voltage; and a control circuit comprising a hysteretic comparator configured to receive a sense signal from the current sense device indicative of the current through the LED and to generate the control signal for the switch, the hysteretic comparator comparing the sense signal to a high hysteresis level and a low hysteresis level, a difference between the high and low hysteresis levels defining a hysteresis window, the control circuit further comprising a frequency regulator configured to monitor the switching frequency of the control signal and to adjust the hysteresis window of the hysteretic comparator in a way to keep the switching frequency constant.