Patent ID: 8508204

Claim:
A method of operating a controller, the controller being for controlling a power generator circuit for supplying power to a pulse modulated signal, the pulse modulated signal being for driving a load, the load being switchable with a switch, which controller has a cycle with a period corresponding to the sum of an off-time and an on-time, the power generator circuit being arranged to start to switch off at the start of the off-time, and to start to switch on at the start of the on-time, the method comprising the steps of: (a) monitoring a rate of change of output power of the power generator circuit at a time when it is ramping up from an off-state to an on-state, (b) determining a lead-time from the rate of change of output power, (c) storing the determined lead-time, and (d) adjusting at least one of the off-time and the on-time of the controller in dependence on the stored lead-time.