Basic knowledge of power modules.The power module is a power supply that can be directly mounted on a printed circuit board and is characterized by an application specific integrated circuit (ASIC), a digital signal processor (DSP), a microprocessor, a memory, and a field programmable gate array (FPGA). ) and other digital or analog loads provide power. In general, such modules are referred to as point-of-load (POL) specialty power supply systems or point-of-use power supply systems (PUPS). Because of the many advantages of modular structure, module power supply is widely used in switching equipment, access equipment, mobile communications, microwave communications, optical communications, routers and other communications fields and automotive electronics, aerospace and so on. Especially in recent years, due to the rapid development of data services and the continuous promotion of distributed power supply systems, the increase of module power supply has exceeded the primary power supply. With the large use of semiconductor technology, packaging technology and high-frequency soft switches, the module power supply density is getting larger and larger, the conversion efficiency is getting higher and higher, and the application is becoming more and more simple.
In the field of switching power supply technology, people develop related power electronic devices and develop switching frequency conversion technology. The two promote each other to promote the switching power supply to a lighter, smaller, thinner, lower noise and high reliability. The direction of anti-interference is developing. Switching power supply can be divided into two major categories: AC/DC and DC/DC. The DC/DC converter has been modularized, and the design technology and production process have been matured and standardized at home and abroad, and have been recognized by users, but The modularity of AC/DC, due to its own characteristics, leads to more complex technical and process manufacturing problems in the process of modularization. The following is a description of the structure and characteristics of two types of switching power supplies.
1, DC / DC conversion
The DC/DC conversion converts a fixed DC voltage into a variable DC voltage, also known as DC chopping. There are two ways to operate the chopper. One is that the pulse width modulation mode Ts is constant, the ton is changed, and the other is frequency modulation.
(1) Buck circuit - step-down chopper, whose output average voltage U0 is smaller than the input voltage Ui, and the polarity is the same.
(2) Boost circuit - the boost chopper, whose output average voltage U0 is greater than the input voltage Ui, and the polarity is the same.
(3) Buck-Boost circuit - buck or boost chopper, whose output average voltage U0 is greater or less than the input voltage Ui, the opposite polarity, the inductance transmission.
(4) Cuk circuit - buck or boost chopper, whose output average voltage U0 is greater or less than the input voltage Ui, the polarity is opposite, and the capacitance is transmitted.
2, AC / DC conversion
AC/DC conversion is to convert AC to DC, and its power flow direction can be bidirectional. The power flow from the power supply to the load is called “rectification”, and the power flow is returned to the power supply by the load called “active inverter”. AC/DC converter input is 50/60Hz AC, because it must be rectified and filtered, so the relatively large size of the filter capacitor is essential, and at the same time due to safety standards (such as UL, CCEE, etc.) and EMC directives Restrictions (such as IEC, FCC, CSA), EMC input must be added to the AC input side and components that comply with safety standards are used, which limits the miniaturization of the AC/DC power supply. In addition, due to internal high frequency, high voltage, and large The current switching action makes it more difficult to solve the EMC electromagnetic compatibility problem, and it also puts high requirements on the internal high-density mounting circuit design. For the same reason, the high voltage and high current switch make the power supply working loss increase, which limits the limitation. The modularization process of AC/DC converters must use the power system optimization design method to achieve a certain degree of satisfaction in their work efficiency.