System and method for determining a characteristic of an input signal

An LED power supply configured to detect a characteristic of an input signal, comprising:

• a Buck power factor control circuit being configured to receive the input signal, the input signal being referenced to a power ground, and to output an output signal, the output signal being referenced to an output ground, wherein the output ground is level shifted with respect to the power ground;
• and
• a controller configured to output an LED drive signal, the controller referenced to the output ground, wherein the controller is configured to determine the characteristic of the input signal measuring a plurality of switching times of the Buck power factor control circuit, and determining conduction times and/or conduction frequencies of the Buck power factor control circuit, the plurality of switching times of the Buck power factor control circuit being determined by the controller according to a switching signal referenced to the output ground.