Switching power supply is the use of transistors composed of oscillator circuit, the 220V utility (rectified and filtered 315V DC) into 15 ~ 35KHz pulse alternating current, through the high-frequency transformer isolation into a low voltage. Because the transistor is working in the switching state, so this electronic transformer is called "switching power supply", mainly used to distinguish him from the "industrial frequency transformer" called.
At present, switching power supply is very widely used: color TV, DVD, laptop, computer, cell phone charger, shaver and so on all use switching power supply.