Introduction to the role of high frequency transformers in switching power supplies
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, electric scooter chargers, and various household appliances. Therefore, in switching power supplies, we always see a high-frequency transformer. Today, we will talk about its role in switching power supplies.
Working principle of switch mode power supply
We know that there are two types of switching power supplies: self-excited switching power supplies and separately excited switching power supplies. Now, let's take separately excited switching power supplies as an example to illustrate their working process, so that we can further explain the role of high-frequency transformers in switching power supplies. In a separately excited switching power supply, a control pulse signal is generated by an independent oscillator to control the conduction and disconnection of the switching tube. When the switching tube V is in the switching state, an electromotive force is generated on the primary winding of the high-frequency transformer, which is induced on the secondary winding. The electromotive force on the secondary winding charges the electrolytic capacitor through the VD2 diode, which acts as a filter and waits for a stable DC voltage on the load RL.
The role of high-frequency transformers used in switch mode power supplies
I think high-frequency transformers have two main functions in switching power supplies, which we will discuss separately below. The first point is that the use of high-frequency transformers in switching power supplies is to improve the conversion efficiency of the power supply. Due to the use of silicon steel sheet iron core in high-frequency transformers, this type of silicon steel sheet has excellent magnetic conductivity, which can greatly improve the electrical 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 and personnel behind, playing a role in safety isolation, while also purifying the high-voltage power supply to prevent interference. We assume that the output voltage of a switching power supply is too high due to some reason during operation, and the excessive voltage will be sent to the protection circuit. Then, the protection circuit in the switching power supply will activate the protection mode, which will "command" the switching transistor to stop working. Once the switching transistor stops working, the primary winding end of the high-frequency transformer will not be able to generate electromotive force, and the secondary winding of the high-frequency transformer will not be able to receive induced electromotive force, resulting in no voltage output at the output end, thus protecting the load from high voltage damage. If a high-frequency transformer is not used, this phenomenon can be very dangerous. If the switch tube is broken down, the high voltage will be directly output to the electrical appliance, burning it out and even endangering human life safety.
