the function of a power supply is to provide the stable voltage required by electrical appliances. as all kinds of appliances nowadays need to work at a stable voltage, the power supply must not only provide the required voltage, but also a stable voltage. In a broad sense, power supplies include power supplies and power circuits. Common power sources include 220V AC provided by the mains, as well as various batteries. Common power supply circuits include various regulated power supplies, uninterruptible power supplies, etc. these power supply circuits process the voltage provided by the power supply into the voltage required by the appliance, and the processed voltage is stable. The power supply circuit is therefore a very important part of the power supply. All electrical appliances must have a good power supply circuit in order to work properly.