I do not understand the transformer should only work in the alternating voltage, but the switching power supply to the PWM IC output terminal connected to the primary input PWM IC has been rectified filter DC. Is the PWM modulation obtained by the high frequency of the exchange?
1, the principle of transformer work is: through the PWM (pulse width modulation) control switch, the rectified DC voltage for high-frequency switch conduction, making high-frequency current into the switching power supply of the high-frequency transformer primary side, which is the transformer vice Side induced current, after rectification can be obtained after the required voltage or multiple voltage.
The transformer in the switching power supply is basically the same as that of a conventional power transformer, except that it has a feedback winding that provides a positive feedback signal to the PWM IC to cause high frequency oscillation along with the primary winding, Winding DC with a large AC component, the high-frequency AC components through the transformer core isolation in the secondary form of a pure high-frequency AC, rectifier filter after the supply of electrical equipment.
Because the frequency is very high, compared to ordinary power frequency, switching power supply in the transformer and filter capacitor are greatly reduced.
2, PWM (pulse width modulation) is higher than 50Hz frequency, so that the transformer can be smaller, and the work efficiency will be greatly improved.
