The main working principle of switch mode power supply
The MOS tubes of the upper and lower bridges take turns conducting. First, the current flows into the upper bridge MOS tube, which utilizes the storage function of the coil to gather electrical energy in the coil. Finally, the upper bridge MOS tube is closed, and the lower bridge MOS tube is opened. The coil and capacitor continue to supply external power. Then turn off the lower bridge MOS transistor, and then turn on the upper bridge to allow current to enter. Repeat this process because the MOS transistor needs to be turned on and off in turn, so it is called a switching power supply.
However, linear power sources are different. Due to the lack of switch intervention, the water supply pipe keeps discharging water. If there is too much, it will leak out. This is what we often see in some linear power sources. The Mos pipe generates a lot of heat, and all the unused electricity is converted into heat energy. From this perspective, the conversion efficiency of linear power sources is very low, and when the heat is high, the lifespan of the components is bound to decrease, which affects the final use effect.
The main difference between switching power supplies and linear power supplies is their working mode.
The power device of a linear power supply works in a linear state, which means that it always works when used, resulting in low work efficiency, usually between 50 [%] and 60 [%]. It can also be said that it is a good linear power supply. The working mode of a linear power supply requires a voltage regulating device to convert it from high voltage to low voltage. Generally, it is a transformer, but there are also other types of power supplies like KX, which can output DC voltage through rectification. In this way, his volume becomes large, bulky, inefficient, and generates a lot of heat. He also has his advantages: small ripple, good adjustment rate, and low external interference. Suitable for use in analog circuits, various amplifiers, etc.
Switching power supply. His power devices work in a switch state (one on and one off, one on and one off, with a very fast frequency. Generally, the frequency of a flat panel switch power supply is between 100-200KHz, and that of a module power supply is between 300-500KHz). In this way, his losses are small, efficiency is high, and there is also a requirement for transformers to use materials with high magnetic permeability. There's a bit of ink on it. His transformer is just a small word, with an efficiency of 80% to 90%. It's said that the best VICOR module in the United States can reach up to 99%. Switching power supplies have high efficiency and small size, but compared to linear power supplies, their ripple and voltage and current adjustment rate are discounted.
