High frequency transformer's function in switching power supply
Switching transformers have many advantages such as high conversion efficiency, small size, light weight, and wide operating voltage range. Switching power supplies are used in mobile phone chargers, battery car chargers, and various household appliances. In switching power supplies, we There will always be a high-frequency transformer. Today we will talk about the role of this high-frequency transformer in switching power supplies.
Working principle of switching power supply
We know that there are two types of switching power supplies: self-excited switching power supply and other-excited switching power supply. Now we will use the example of other-excited switching power supply to illustrate its working process so that we can further illustrate the role of high-frequency transformers in switching power supplies. In the other-excited switching power supply, an independent oscillator generates a control pulse signal to control the on and off of the switch tube. When the switch tube V is in the switch state, there will be an electromotive force generated on the primary winding of the high-frequency transformer. , so that it will be induced to the secondary winding, the electromotive force on the secondary winding will charge the electrolytic capacitor through the VD2 diode, and the electrolytic capacitor will act as a filter, so that a stable DC voltage will be obtained on the load RL .
The role of high-frequency transformers used in switching power supplies
I think that the high-frequency transformer mainly has the following two functions in the switching power supply, and we will talk about them separately below. The first point is that the use of high-frequency transformers in switching power supplies is to improve the conversion efficiency of power supplies. Since the iron core of the high-frequency transformer is a silicon steel sheet iron core, this silicon steel sheet has good magnetic permeability and can greatly improve the resistivity and magnetic permeability, thereby improving the conversion efficiency of the switching power supply and increasing its output. power.
The second point is to protect the safety of the load behind and personal safety, which plays the role of safety isolation, and also purifies the high-voltage power supply to prevent interference. We assume that the output voltage of the switching power supply is too high for some reason during operation, so that the excessive voltage will be sent to the protection circuit, then the protection circuit in the switching power supply will turn on the protection mode, and it will "command" the switch Once the switching tube stops working, the primary winding end of the high-frequency transformer cannot generate electromotive force, so the secondary winding of the high-frequency transformer cannot obtain the induced electromotive force, and the output terminal will have no voltage output, thereby protecting the The load is protected from high voltage damage. If the high-frequency transformer is not used, once this phenomenon occurs, it will be very dangerous. If the switch tube is broken down, the high voltage will be directly output on the electrical appliance, which will directly burn the electrical appliance, and even endanger human life.
