Switching power supply is a voltage conversion circuit, the main work content is to boost and buck, widely used in modern electronic products. Because the switching triode always works in the state of "on" and "off", so called switching power supply, switching power supply chip is generally composed of pulse width modulation (PWM) control IC and MOSFET, switching power supply IC refers to the pulse width control integration of switching power supply, power supply depends on it to adjust the stability of output voltage and current.
Electronic switching power supply chip can be divided into AC/DC power chip and DC/DC power chip two categories, AC/DC and DC/DC or there are great differences, from the product design, device selection request, robustness to complete the purpose and so on: AC/DC is far more complex than DC/DC, difficult to do, now DC/DC converter has been modular, and the design technology and production process at home and abroad have been mature and standardized, and has been recognized by users, but AC/DC modular, because of its own characteristics in the process of modular, encountered more complex technology and process manufacturing problems.
AC/DC power chip conversion is to transform AC into DC, its power flow can be bidirectional, power flow from the power source to the load is called "rectification", power flow from the load back to the power source is called "active inverter". AC/DC converter input is 50/60Hz AC, because must be rectified, filtering, so relatively large filter capacitor is essential, and due to the safety standards (such as UL, CCEE, etc.) and EMC instructions (such as IEC, FCC, CSA) restrictions, EMC filtering and safety standard components must be added to the AC input side to limit the miniaturization of AC/DC power supplies.
Due to the internal high frequency, high voltage and high current switch action, it makes it more difficult to solve the EMC EMC problem, and also puts forward high requirements for the internal high-density installation circuit design. For the same reason, high voltage and high current switch makes the power supply work loss increase, limiting the AC/DC converter modular process. Therefore, the optimal design method of power supply system must be adopted to make its work efficiency reach a certain degree of satisfaction.
In terms of device selection and reliability, AC/DC design is more difficult than DC/DC. From the above description, AC/DC directly faces high voltage, and the selection of input devices, especially power MOSFET, the higher the voltage, the greater the on-voltage drop and switching loss, the more difficult it is to meet the thermal design of power supply. Other diodes and triodes also have such problems, high voltage is difficult to choose, low voltage is easy to choose. At the same time, AC/DC power requirements fit the safety level is much higher than DC/DC. From the point of view of circuit structure AC/DC generally to two levels of transformation, and DC/DC only need one level of transformation, and DC/DC use of the main power conversion circuit is relatively simple.
DC/DC power chip is a fixed DC voltage into a variable DC voltage, also known as DC chopper. There are two working modes of chopper, one is the pulse width modulation mode Ts unchanged, change TON (general), the other is the frequency modulation mode, ton unchanged, change is easy to produce interference.
Switching power supply control chip varieties also very much, mainly divided into two major categories of current control and voltage control model, at present our country's power supply technology and international advanced technology had not much difference, AC/DC, DC/DC about system, all bear a role, as a system power transformation and transmission, its role in the system is equivalent to the role of the human body heart, Once appear problem, the system will stop working, people at the edge of the switching power supply chip technology is developing related power electronics device, edge development switch frequency conversion technology, which both promote each other to promote switch power supply each year the growth rate of more than two digits to light, small, thin, low noise, high reliable and anti-jamming in the direction of development.