Led driver circuit, and led arrangement and a driving method

Abstract

The invention provides a driver circuit for driving an LED arrangement which uses a switch mode power converter, for example a flyback ringing choke converter, which comprises a main switch (e.g. bipolar transistor) and a sub-circuit for generating a current for the control terminal of the main switch. The sub-circuit in some examples makes use of an auxiliary winding as a voltage supply, and further comprises a ramp circuit for generating a ramp voltage from the voltage supply and a voltage follower, such as a control transistor, connected between the voltage supply and the control input of the main switch. By ramping up the current of the main switch, the losses arising as a result of the current flowing to the control input of the main switch are reduced. One set of examples makes use of a flyback ringing choke converter, which enables low cost implementation and good efficiency. The driver is able to receive a wide range of input voltages, by ensuring that the power loss is kept low. In particular, by ramping up the control current of the main switch, the losses arising as a result of the current flowing are reduced.