Patent ID: 7791847

Claim:
A fault-sensing and protecting apparatus for sensing fault in a soft start circuit of an inverter the soft start circuit comprising a soft start resistor and an electrically controllable switch unit with a normally open end, and the soft start resistor being in parallel with the normally open end, the fault-sensing and protecting apparatus comprising: a central processing unit (CPU) electrically connected to the inverter and an input port of the electrically controllable switch unit; and a photo coupler comprising a light emitting diode (LED) and a photo diode, wherein the LED is electrically connected to a serial resistor and then connected to the normally open end in parallel, wherein the photo diode is electrically connected to the CPU; wherein the CPU is configured to stop outputting voltage to the inverter after the inverter starts and the normally open end is controlled by the CPU to become short circuited and the CPU senses signal from the photo coupler.