What is a switching power supply? What's the difference between a linear power supply?

With the development trend and independent innovation of power electronics technology, switching power supply technology is also constantly innovating. At present, switching power supply is widely used in almost all electronic equipment with the characteristics of small, light weight and high efficiency. It is an indispensable power supply method for the rapid development of the electronic information industry.

Switching power supply is a relative linear power supply said, the input end immediately will AC current rectifier into AC, and then in the effect of high frequency fluctuation circuit, with the power switch tube to control the conduction of the current, high frequency surge current. With the help of inductor (high frequency transformer), output stable bottom voltage AC.

Because the magnetic core size of the transformer is inversely proportional to the square meter of the output power of the switching power supply, the higher the frequency of the rail, the smaller the heart. That can greatly reduce the transformer, so that the power to ease the net weight and volume. And because it operates the direct current immediately, the efficiency of such power sources is much higher than that of linear power sources. That saves electricity, so it is popular. Switching power supply manufacturers remind, it is also a defect, that is, the circuit is complex, difficult maintenance, the environmental pollution of the circuit is more serious. The power supply is noisy and should not be used in some low noise circuits.

Characteristics of switching power supply

Switching power supply generally consists of pulse width modulation (PWM) control IC and MOSFET. With the development trend of power electronics technology and independent innovation, the current switching power key is widely used in basically all electronic products with the characteristics of small and medium-sized, lightweight and high efficiency, its necessity can be seen.

Classification of switching power supplies

According to the method of connecting the power switching components in the circuit, the switching power supply can be divided into series switching power supply, parallel switching power supply, transformer switching power supply and so on.

Among them, the transformer switching power supply can be further divided into: push-pull, half product chain, full product chain and so on. According to the transformer to encourage and output working voltage position, and can be divided into: forward, flyback, single and double excitation and so on.

Switching power supply and general power supply difference

General power supply is generally linear power supply, linear power supply, is to adjust the tube work in the linear case of power supply. And in the switching power supply is not the same, the power switch tube (in the switching power supply, people generally referred to the adjustment tube as the power switch tube) is working in the open, off two cases: open - resistor is not big, off - resistor very big.

Switching power supply is a relatively new type of power supply. It has the advantages of high efficiency, light weight, rising and lowering blood pressure, large power and so on. But because the circuit work in the power switch situation, so the noise is larger.

Key difference: Approach at work

The output power regulating tube of a linear power supply has been operating in a large area, and the current flow through it is continuous. Because the adjustment tube consumes a lot of output power, it must be a large output power adjustment tube and equipped with a large volume heat pipe radiator, hot more serious, high efficiency is very low, generally in 40%~60%(also said to be a very good linear power supply).

The working method of linear power supply, so that from high voltage to bottom voltage must have voltage equipment, generally all transformers, but also other like KX power supply, and then after the rectifier output AC voltage. So the volume is quite large, relatively heavy, low efficiency, calorific value is also large; But it is also an advantage: small harmonic distortion, good adjustment rate, small impact of opening to the outside world, suitable for use and simulation of analog circuits/various amplifiers.

Switching power supply its power electronic devices work in the power switch situation, when the working voltage adjustment kinetic energy is according to the inductance to temporary storage, so that his loss is small, high efficiency is high, the heat pipe heat dissipation provisions are low, but it is also higher provisions for transformers and storage inductors, with low loss and high permeability of raw materials to do. Its transformer is a word small. The total efficiency is 80% ~ 98%, the high efficiency of switching power supply but the size is small, but the harmonic distortion and linear power supply than his, the current voltage adjustment rate will have a certain discount.