Patent ID: 8125197

Claim:
A switch controller comprising: a voltage sensor configured to generate an input sensing voltage corresponding to a voltage input into the switch; a zero voltage detector configured to: compare the input sensing voltage with a predetermined first reference value; and generate a zero cross detection signal with a first level or a second level in accordance with a result of the comparison; a reference clock generator configured to generate a reference clock signal such that the reference clock signal varies in frequency by one cycle of the zero cross detection signal; a digital sine curve generator configured to generate digital signals by using the reference clock signal and the zero cross detection signal, the digital signals synchronizing with the zero cross detection signal while increasing in accordance with the reference clock signal during half of the one cycle of the zero cross detection signal and decreasing in accordance with the reference clock signal during the other half cycle of the zero cross detection signal; and a digital-to-analog converter configured to generate a reference signal with a voltage level corresponding to the digital signal.