Air conditioners were the first major home appliance to use inverter control. Key semiconductor devices used for inverter control of a compressor motor include microcontrollers, insulated gate bipolar transistors (IGBTs) and photocouplers. Microcontrollers provide overall system control, pulse-width-modulation (PWM) generation and system protection functions. IGBTs and photocouplers reside in the inverter driver circuit and its interface, respectively. These days, more and more air conditioners feature a self-cleaning capability and a vector-controlled compressor motor for energy saving. Power factor correction (PFC) ICs or IGBTs are used in the power supply circuit to keep harmonics in the input current below the IEC limit.
