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what is a switching power supply
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what is a switching power supply

Time:2021-05-17  /  Read:99

Switching power supply is a kind of high frequency switching type energy conversion electronic circuit, often used as the power supply of equipment, common conversion classification: AC-DC, DC-DC, DC-AC, etc., due to the rapid development of LED technology, switching power supply is widely used and towards light, small, thin, low noise, high reliability, anti-interference direction.

 

Switching power supply introduction:

What is switching power supply?Switch Mode Power Supply (SMPS), also known as Switched Power Supply and Switching Converter, is a kind of high-frequency Power conversion device and a kind of Power Supply.Its function is to convert the voltage of one level into the voltage or current required by the client through different forms of architecture.The input of switching power supply is mostly AC power supply (such as mains) or DC power supply, and the output is mostly the equipment that needs DC power supply, such as LED lamp strip, switching power supply will carry out the voltage and current conversion between the two.

 

Operating principle of switching power supply

The input higher DC voltage (AC) is converted to the lower DC voltage (DC) required by the luminaire by the high frequency switching technology.The core of switching power supply is to improve the power density of the power supply by increasing the working frequency, so as to achieve the purpose of reducing the volume and weight of the transformer.The obvious advantage of switching conversion is that it greatly improves the conversion efficiency of electric energy. The efficiency of typical LED lamp power supply is more than 85%, while the efficiency of the corresponding linear regulated voltage power supply is only about 50%.The stability of the output voltage of the switching power supply depends on the change of the pulse width, which is called PWM.

 

Switching power supply basic components

Resistor: a resistor is used to limit the current in the circuit and release the charge stored in the capacitor after the power supply is turned off to avoid electric shock accidents.

Capacitance: In order to withstand the high voltage DC after rectification, the high-voltage electrolytic capacitor is used for the primary circuit of the power supply;In order to reduce the loss caused by continuous charging and discharging of the output electrolytic capacitor, the secondary side circuit uses a large number of electrolytic capacitors with high temperature resistance and long life and low impedance.Because there are chemical substances in the capacitor (electrolyte), the working temperature has a considerable impact on the life of the electrolytic capacitor, so for a long time to operate, in addition to maintaining a good heat dissipation of the power supply, but also to ensure the reliability and life of the stable operation of the power supply.

Inductance: the inductor can be used as the energy storage component in the switching circuit, the voltage adjustment component of the magnetic amplifier circuit and the output filter after the secondary side rectification. It is widely used in the power supply.

Diodes: inside the power supply, different types and specifications are used according to the required output size of each circuit. In addition to general diodes, there are Schottky barrier diodes (SBD), fast recovery diodes (FRD), Zener diodes (ZD) and other types.

Triode: transformer: transformer as high and low voltage separation, and the use of magnetic energy for energy exchange, not only can avoid the danger of leakage when the high and low voltage circuit failure, but also can simply produce a variety of voltage output.

Because the transformer operates at a higher frequency, the volume of the transformer is smaller than that of the general AC transformer.

Control IC: The control IC in the power supply is divided according to the installation position and purpose. It is used as PFC circuit, as power level primary side PWM circuit, and as PFC/PWM integrated control.

 

Switching power supply circuit diagram

General switch circuit mainly includes the input filter in the PCB, switching circuit, control circuit, the output filter for four main parts, the red box is the main current channel, including input filter, switching circuit, three important part of the output filter, for the rest of the control circuit, which need to focus on the part of the sampling circuit and feedback circuit.

 

Characteristics of switching power supply

Small size, light weight;Switching power supply is a kind of nonlinear power supply, because there is no power frequency transformer, so the volume and weight of the linear power supply is only 20~30%.

Low power consumption, high efficiency;Power transistors work in the switching state, so the transistor's power consumption is small, the conversion rate is high, generally 60~70%, and the linear power supply is only 30~40%.

 

Application of switching power supply

Switching power supply products are widely used in industrial automation control, military industry equipment, scientific research equipment, LED lighting, industrial control equipment, communications equipment, electrical equipment, instrumentation, medical equipment, semiconductor refrigeration and heating, air purifier, electronic refrigerator, LCD, LED lamps and lanterns, communications equipment, audio and video products, security monitoring, LED lights belt, computer case,Digital products and instruments and other fields.