Patent ID: 8766561
Filing Date: 2014-07-01
Classification: H05B

Abstract:
1. A lighting device comprising: a DC power source; a switching power supply further comprising a switching element, an inductive element to which a current is intermittently passed from the DC power source via the switching element, a rectifying element effective to pass the current flowing from the inductive element, and an output capacitor effective to charge and discharge current flowing from the inductive element, first and second ends of said output capacitor defining first and second output terminals for the lighting device, respectively; switching control circuitry effective to determine a switching frequency and an ON period for the switching element, and to control the switching element to be turned on/off according to the determined frequency and ON period; a variable impedance element coupled across the output terminals for the lighting device; and an impedance control circuit effective to adjust the impedance of the variable impedance element in association with the determined ON period for the switching element, wherein an impedance value corresponding with a minimum on-duty of the switching element is smaller than an impedance value corresponding with a maximum on-duty of the switching element.