Patent ID: 8456873

Claim:
A method for operating a power conversion device comprising: activating the power conversion device, wherein activating the power conversion device comprises turning on the power conversion device and turning off a switch in the power conversion device; then rectifying a grid voltage to produce a rectified voltage comprising a dc voltage; placing the rectified voltage on a bus coupled to an output converter, the bus having the switch located on at least one line of the bus; monitoring the rectified voltage using voltage sensing circuitry, the switch remaining off until the rectified voltage reaches zero volts; turning the switch on when the rectified voltage reaches zero volts; maintaining the switch in the on state during operation of the device until it is determined that the rectified voltage exceeds a first threshold, the first threshold indicating an excessive voltage level that poses a threat of damage to a bulk capacitor in the output converter; and turning the switch off when the rectified voltage exceeds the first threshold.