Patent ID: 9030114
Filing Date: 2015-05-12
Classification: H05B

Abstract:
1. An LED drive circuit that carries out, by use of a DC-to-DC converter, control of brightness of light of an LED, the LED drive circuit comprises: (i) a control IC having a function to adjust an off period of oscillation of the DC-to-DC converter; (ii) an emitter follower circuit connected to a terminal of the control IC, the terminal determining the off period of oscillation of the DC-to-DC converter; (iii) a first DC voltage supply connected to a MULT terminal of the control IC; and (iv) a second DC voltage supply connected to the emitter follower circuit, wherein wherein voltages of the first DC voltage supply and the second DC voltage supply are variable, wherein the brightness control is carried out so that: where (i) f(dim.min) is an average oscillation frequency during a minimum audible brightness control, (ii) f(dim.max) is an average oscillation frequency during a maximum brightness control, and (iii) f(max) is a maximum average oscillation frequency.