Patent ID: 7317287

Claim:
A circuit arrangement for an LED array, comprising: a plurality of parallel-connected LED chains, in each of which at least one LED is arranged, and when there are two or more LEDs, the latter are connected in series, in which anode sides of the respective LED chains are coupled to a positive pole of a supply voltage and cathode sides of the respective LED chains are coupled to a negative pole of the supply voltage; a plurality of regulating arrangements for regulating a predetermined current distribution among the LED chains, with said plurality of regulating arrangements being respectively connected in series with said LED chains such that each of said LED chains has a different one of said plurality of regulating arrangements connected in series with said each LED chain; wherein each of said regulating arrangements includes one of a following transistor arrangement: a) a bipolar transistor, a collector terminal of which is connected to the cathode side of the associated LED chain, and an emitter terminal of which is connected via an emitter resistor to the negative pole of the supply voltage, or b) a bipolar transistor, a collector terminal of which is connected to the anode side of the associated LED chain, and an emitter terminal of which is connected via an emitter resistor to the positive pole of the supply voltage; a drive circuit applying a predetermined current to base terminals of the bipolar transistors; and wherein said drive circuit comprises a series circuit formed by a diode and a resistor, said series circuit being arranged between the respective collector terminal and the respective base terminal of the transistor of a regulating arrangement.