Patent ID: 6933767

Claim:
A circuit arrangement for supplying an LED array comprising: input terminals for connection to a voltage supply source; output terminals for connection to the LED array; a DC—DC-converter coupled between the input terminals and the output terminals, the DC—DC-converter comprising: an inductive element L; a unidirectional element; a switching element coupled to the inductive element and the unidirectional element; and a control circuit coupled to a control electrode of the switching element for generating a high frequency control signal for rendering the switching element conductive and non-conductive at a high frequency to thereby operate the DC—DC-converter in the critical discontinuous mode and equipped with circuitry for controlling the current through the output terminals at a predetermined value, the circuitry for controlling the current through the output terminals comprising: a circuit coupled to the input terminals and the output terminals for controlling a time lapse T on , during which the switching element is maintained in a conductive state during each high frequency period of the control signal, proportional to a mathematical expression that is a function of V in and V out , wherein V in is the voltage present between the input terminals and V out is the voltage present between the output terminals; wherein the DC—DC-converter is an up-converter and the circuit comprises a circuit for controlling T on proportional to V out /V in 2 .