High efficiency driver circuit with fast response

A switched-mode driver including an output connectable to a load, the switched-mode driver comprising:

• a converter stage to receive an input voltage at an input and provide an output voltage to the load at the output, the converter stage further comprising a feedback loop, the converter stage further including a switching device;
• a power factor correction controller connected to the switching device to provide a gate signal so that an input current waveform follows an input voltage waveform;
• a speed-up circuit connected to the switching device in the converter stage, the speed-up circuit comprising a control switch with an associated series current sensing resistance to determine current flowing between the switching device and the control switch, and being operable to increase current at the input of the switched-mode driver in response to an increased demand by the load;
• and
• one or more current regulators comprising an overhead control circuit configured to inject a control signal into the feedback loop to adaptively adjust the output voltage in response to changes in operating efficiency of the load.

A method of operating an LED lighting system, the method comprising:

• receiving an input voltage and supplying an output voltage to one or more parallel LED strings;
• using a power factor correction controller connected to a switching device to provide a gate signal so that an input current waveform follows an input voltage waveform;
• using a speed-up circuit comprising a control switch with an associated series current sensing resistance to determine current flowing between the switching device and the control switch, to increase current at an input to a converter stage in response to an increased demand for current by the one or more parallel LED strings;
• using a current regulator, the current regulator comprising an overhead controller to adaptively adjust the output voltage in response to changes in the operating efficiency of LEDs in the one or more parallel LED strings.