Principle characteristics and classification of switching power supply

　　Switching power supply is a kind of power supply that uses modern power electronic technology to manipulate the time ratio of switching on and off to maintain a stable output voltage. Switching power supplies are usually composed of pulse width modulation (PWM) control ICs and MOSFETs. With the development and innovation of power electronics technology, the switching power supply technology is also constantly innovating. At this stage, switching power supplies are widely used in almost all electronic products with their advantages of small size, light weight and high efficiency. It is an indispensable power supply method for the rapid development of the current electronic information industry. With the rapid development and expansion of my country's manufacturing industry, switching power supplies have slowly stepped onto the international stage, and the volume of power supplies has gradually tended to be modularized and miniaturized, and the anti-interference level of power supplies has also been strengthened.

　　1 switching power supply

　　Switching power supply is a general term for switching regulated power supply, which usually refers to an AC-DC inverter circuit whose input is AC voltage and output is DC voltage. The power switch tube in the switching power supply works in the high-frequency switching state and consumes very low power. The power supply efficiency can reach 75%~90%, which is twice as high as the general linear stabilized power supply (linear power supply).

　　The difference between the linear power supply and the switching power supply is that the voltage regulation of the linear power supply can be regarded as the voltage regulation of the resistance value, which is like adjusting the sliding rheostat to change the voltage. The switching power supply can be regarded as changing the voltage by adjusting the switching frequency.

　　Switching power supply classification

　　1. No power frequency transformer type switching power supply

　　The non-power frequency transformer-type switching power supply uses a small high-frequency transformer to replace the bulky power frequency transformer, and the experiment is isolated from the power grid. Because the components in the switching power supply work in the high-frequency switching state, the power consumption is very low, and the power supply efficiency is doubled compared with the general linear power supply.

　　2. Switching power supply regulator

　　Switching power supply regulator is a switch type integrated power supply regulator. It integrates PWM controller, power output stage, protection circuit, etc. in a chip. The efficiency of the power supply regulator can reach more than 90%, and some can also Continuously adjust the output voltage, suitable for the production of switching power supplies from tens of watts to hundreds of watts.

　　3. Single chip switching power supply

　　The single-chip switching power supply integrates the main circuits of the switching power supply in the chip, which can realize output isolation, pulse width modulation and multiple protection functions, and its integration is the highest. The single-chip switching power supply adapts 85~265V, 47~400Hz AC power through the input rectifier filter. And it has the advantages of high integration, high cost performance, simplest peripheral circuits, and best performance indicators. Now it has become the preferred integrated circuit for the development of medium and small power switching power supplies, precision switching power supplies and modular switching power supplies below 600W.

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