A reference signal generating circuit is provided that generates a reference signal corresponding to an input signal for power factor compensation of a power converter. The reference signal generating circuit includes a detector sampling the input signal according to a reference clock to detect and hold the maximum input signal and a phase measuring unit measuring a phase of the sampled input signal based on the sampled input signal and the detected maximum input signal. The circuit also includes a reference signal generating unit configured to generate a reference signal having a specific value in response to the measured phase.