The specific circuit of switching power supply consists of the following categories
(1) Buck circuit - step-down chopper, its output average voltage Uo is less than the input voltage Ui, and the polarity is the same.
(2) Boost circuit - boost chopper, its output average voltage Uo is greater than the input voltage Ui, and the polarity is the same.
(3) Buck-Boost circuit - buck or boost chopper, its output average voltage Uo is greater than or less than the input voltage Ui, the polarity is opposite, and the inductance is transmitted.
(4) Cuk circuit - buck or boost chopper, its output average voltage Uo is greater than or less than the input voltage UI, the polarity is opposite, and the capacitance is transmitted. Today's soft-switching technology has brought about a qualitative leap in DC/DC. Various ECI soft-switching DC/DC converters designed and manufactured by VICOR in the United States have a maximum output power of 300W, 600W, 800W, etc., and the corresponding power density is (6 , 2, 10, 17) W/cm3, the efficiency is (80-90)%. The latest high-frequency switching power module RM series using soft switching technology launched by Japan NemicLambda Company has a switching frequency of (200~300) kHz and a power density of 27 W/cm3. It uses a synchronous rectifier (MOS-FET instead of Xiao Tetky diode), the efficiency of the whole circuit is increased to 90%.
AC/DC conversion
AC/DC conversion is to convert AC to DC, and its power flow can be bidirectional. The power flow from the power source to the load is called "rectification", and the power flow from the load back to the power source is called "active inverter". The input of the AC/DC converter is 50/60Hz alternating current. Because it must be rectified and filtered, a relatively large filter capacitor is essential. At the same time, due to safety standards (such as UL, CCEE, etc.) and EMC directives Restrictions (such as IEC, FCC, CSA), the AC input side must add EMC filtering and use components that meet safety standards, which limits the miniaturization of the AC/DC power supply. In addition, due to the internal high frequency, high voltage, and large current The switching action makes it more difficult to solve the problem of EMC electromagnetic compatibility, which also puts forward high requirements for the design of internal high-density installation circuits. For the same reason, high-voltage and high-current switches increase power consumption and limit AC /DC converter modularization process, so it is necessary to adopt the power system optimization design method to make its work efficiency reach a certain degree of satisfaction.
AC/DC conversion can be divided into half-wave circuit and full-wave circuit according to the wiring method of the circuit. According to the number of power supply phases, it can be divided into single phase, three phase and multi phase. According to the working quadrant of the circuit, it can be divided into one quadrant, two quadrants, three quadrants, and four quadrants.
