Patent ID: 8664889
Filing Date: 2014-03-04
Classification: G05F,H02M,H05B,Y02B

Abstract:
1. A load control device for controlling the amount of power delivered from an AC power source to an electrical load to a desired amount of power, the load control device comprising: a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the bidirectional semiconductor switch having a control input for rendering the bidirectional semiconductor switch conductive and non-conductive; and a control circuit receiving a signal representative of a voltage developed across the bidirectional semiconductor switch, the control circuit operable to determine a half-cycle start time near the beginning of a half-cycle of the AC power source in response to the signal representative of the voltage developed across the bidirectional semiconductor switch; wherein the control circuit: further comprising a rectifier circuit for receiving the voltage developed across the bidirectional semiconductor switch and generating a rectified voltage; wherein the signal representative of a voltage developed across the bidirectional semiconductor switch comprises the rectified voltage generated by the rectifier circuit; wherein the control circuit is operable to determine the half-cycle start time in response to the magnitude of the rectified voltage exceeding a threshold when the rectified voltage is increasing in magnitude with respect to time, such that the half-cycle start time occurs after the beginning of a half-cycle of the AC power source; and wherein the control circuit comprises a microprocessor.