Patent ID: 8143810

Claim:
A LED driver arrangement including: a switching-mode stage ( 12 ) to produce a drive current for feeding at least one LED (L) from a DC input ( 10 ); a current sensor ( 18 ) sensitive to the current fed to said at least one LED (L) for producing a feedback signal indicative of the intensity of the drive current fed to said at least one LED (L); error amplifier circuitry ( 24 ) for comparing said feedback signal with a reference value indicative ( 20 , 22 ) of a LED current as requested by a user and generating a control signal ( 32 ); control circuitry ( 26 , 28 , 30 ) sensitive to said control signal ( 32 ) to control said switching-mode stage ( 12 ) whereby the drive current fed by said switching-mode stage ( 12 ) to said at least one LED (L) corresponds to said LED current as requested by a, user, characterized in that it includes: an opto-coupler ( 34 ) to feed said control signal ( 32 ) to said control circuitry ( 26 , 28 , 30 ); said opto-coupler ( 34 ) having associated biasing circuitry ( 341 , 342 ) for causing the current on said opto-coupler ( 34 ) to increase when said LED current as requested by a user decreases, said opto-coupler ( 34 ) configured to saturate when the drive current fed by said switching-mode stage ( 12 ) to said at least one LED (L) reaches a minimum level; an auxiliary supply voltage (V aux1 ) for said control circuitry ( 26 , 28 , 30 ), wherein said auxiliary supply voltage (V aux1 ) is kept above a minimum level by said opto-coupler ( 34 ) and the associated biasing circuitry ( 341 , 342 ), when such opto-coupler ( 34 ) is saturated.