Patent ID: 7994727

Claim:
A power-supply arrangement for driving at least one light-emitting diode (LED) having a threshold voltage, including: a transformer having a secondary winding for driving said at least one LED and a primary winding defining a transformer turn ratio, a half-bridge arrangement to be fed with an input voltage and coupled to said transformer, a resonant circuit between said half-bridge arrangement and the primary winding of said transformer, said resonant circuit having a resonance frequency, and a controller configured for switching said half-bridge arrangement with a switching frequency variable between at least one first value and at least one second value, wherein said second value is closer than said first value to said resonance frequency, the controller varies said switching frequency toward the second value to produce a boosting effect of the voltage fed towards said at least one LED via said transformer when said input voltage is lower than the threshold voltage of said at least one LED multiplied by the transformer turn ratio, wherein said power supply arrangement is located in a housing; said at least one LED is connected to the secondary winding of said transformer via a rectifier, wherein said rectifier is placed outside said housing.