A power supply is a device that provides power to electronic equipment, also known as a power supply, which provides the electrical energy needed by all the components in a computer. The size of the power supply power, current and voltage stability, will directly affect the computer's performance and service life. Generators can convert mechanical energy into electrical energy, and dry batteries can convert chemical energy into electrical energy. Generator, the battery itself is not electrically charged, its poles were positive and negative charge, positive and negative charge generated by the voltage, the charge conductor would have been, to generate current only need to add voltage can be, when the battery poles connected to the conductor in order to generate current and the positive and negative charge released, when the charge is dissipated, it will be loaded out of the flow of the elimination. Dry cell batteries are called power sources. A device that turns alternating current into direct current by means of a transformer and rectifier is called a rectified power supply. An electronic device that provides a signal is called a signal source. A crystal transistor amplifies the signal sent from the front and transmits the amplified signal to the circuit behind. The crystal transistor can also be regarded as a signal source for the circuit behind it. Rectifier power supply, signal source is sometimes called a power supply.