The difference between switching regulated power supply and linear adjustment regulated power supply
1. Comparison between power frequency transformer and high frequency transformer
The switching regulated power supply uses a high-frequency transformer, and the linear regulated power supply uses a power frequency transformer. The description is as follows:
a. The power frequency transformer must be used in the linear adjustment regulated power supply, and the 220V AC mains voltage is reduced through the power frequency transformer. Its working frequency is low, and silicon steel sheet is used as the iron core.
b. The switching regulator circuit uses a high-frequency transformer with magnetic material as the magnetic core. Its operating frequency is very high, its volume is greatly reduced, and its weight is only about one-fifth of the power frequency transformer.
2. Comparison between adjusting tube and switching tube
The main triode in the linear regulated power supply is the adjusting tube, and the main triode in the switching power supply is the switching tube (MOS tube):
a. The operating frequency of the switching tube is high. The switch tube is used in the switching power supply, and the adjustment tube is used in the linear regulated power supply. The working methods of the two are different. The working frequency of the triode is different, and the working frequency of the switch tube is much higher.
b. The switching tube works in the switching state. The switching tube in the switching power supply works in the switching state, that is, it either works in the cut-off state or in the saturated state; in this working mode, the switching tube consumes very little power and has high efficiency, which can reach more than 80%.
c. The power consumption of the switching tube is small. Due to the low power consumption of the triode working in the switching state, there is no need to provide a large heat sink for the switching tube. The temperature inside the machine is low, which is conducive to the stable operation of the power circuit for a long time, and the life of the power supply is relatively long.
d. Adjustment tube efficiency is low. The adjustment tube in the linear power supply works in the amplified state, all the load current flows through the adjustment tube, and the voltage drop between the collector and the emitter of the adjustment tube is used for voltage regulation, and the tube between the collector and the emitter The pressure drop is large, the adjustment tube temperature is high, and a larger volume of heat sink is required. Its conversion efficiency is low, only about 50%.
3. Comparison of rectifier circuit and filter circuit
The rectification and filter circuits of switching power supply and linear regulated power supply are compared as follows:
a. The working voltage of the rectifier circuit is different. The rectifier circuit of the switching power supply is to rectify the 220V AC mains first, output a DC voltage of about 300V, and send it to the next-level circuit for inversion; the AC voltage in the rectifier circuit is relatively high, and the reverse withstand voltage of the rectifier diode is required high. The rectifier circuit in the linear regulated power supply rectifies the low-voltage AC voltage output by the secondary winding of the power transformer. The AC voltage in the rectifier circuit is relatively low, and the reverse withstand voltage of the rectifier diode is required to be low.
b. The capacity requirements of the filter capacitor in the output circuit are different. The capacity of the filter capacitor in the output circuit of the switching power supply is relatively small, but the high-frequency characteristics of the filter capacitor are required to be good. Good filtering effect. The capacity of the filter capacitor in the linear regulated power supply is relatively large. This is because the output voltage AC frequency of the linear power supply is low, and a large enough filter capacitor must be used to achieve a good filtering effect.
4. Comprehensive comparison of circuit principles
a. The circuit of the switching power supply is complex, and there are many components, ranging from dozens to hundreds of components. The main reason is that the control circuit is complex, and the addition of various protection circuits makes the already complex circuit more complicated. It is difficult for electronic engineers who are just getting started to understand the working principle of switching power supplies. When analyzing circuits, multiple conditions need to be used at the same time. The circuits are interconnected, so comprehensive ability to analyze circuits is required. The protection circuit in the switching power supply circuit is complex, and when a fault occurs, it will often cause damage to multiple components, which is difficult to repair and requires high repair technology.
b. The linear power supply is much simpler. A power transformer, plus a rectifier diode, a filter capacitor and a linear adjustment tube, only have a few components. It is easier to understand and analyze the working principle. The protection circuit of the linear regulated power supply is simple, and most products do not have a protection circuit, and the circuit analysis and understanding are relatively easy.
