Classification of switching power supply, AD/DC and DC/DC power supply in detail
People's switching power supply technology field is the side of the development of related power electronic devices, the side of the development of switching inverter technology, the two promote each other to promote the switching power supply each year to more than double-digit growth rate in the direction of light, small, thin, low-noise, high-reliability, anti-jamming development. Switching power supply can be divided into two categories of AC / DC and DC / DC, DC / DC converter has now achieved modularity, and design technology and production processes at home and abroad have matured and standardised, and has been recognised by users, but the modularity of the AC / DC, because of its own characteristics make the process of modularity, encountered in the modular process, a more complex technology and manufacturing process issues. The following are two types of switching power supply structure and characteristics are described.
DC/DC conversion
DC/DC conversion is the conversion of a fixed DC voltage into a variable DC voltage, also known as DC chopper. Chopper works in two ways, one is the pulse width modulation method Ts is unchanged, change the ton (general purpose), the second is the frequency modulation method, the ton is unchanged, change the Ts (prone to interference). Its specific circuit consists of the following categories:
(1) Buck circuits - buck choppers, whose output average voltage Uo is less than the input voltage Ui, with the same polarity.
(2) Boost circuits - boost choppers, whose output average voltage Uo is greater than the input voltage Ui, with the same polarity.
(3) Buck-Boost circuit - Buck or Boost chopper whose output average voltage Uo is greater or less than the input voltage Ui, with opposite polarity and inductive transfer.
(4) Cuk Circuit - Buck or Boost Chopper with an average output voltage Uo greater or less than the input voltage Ui, opposite polarity, and capacitive transfer.
Today's soft-switching technology makes a qualitative leap in DC/DC, the United States VICOR company designed and manufactured a variety of ECI soft-switching DC/DC converter, its maximum output power of 300W, 600W, 800W, etc., the corresponding power density of (6, 2, 10, 17) W/cm3, the efficiency of (80-90) per cent. Japan's NemicLambda * newly introduced a soft-switching technology of high-frequency switching power supply module RM series, its switching frequency (200-300) kHz, power density has reached 27 W/cm3, using synchronous rectifier (MOS-FET instead of Schottky diode), is the entire circuit efficiency increased to 90%.
AC/DC conversion
AC/DC conversion is to convert AC to DC, the power flow can be bi-directional, the power flow from the power supply to the load is called "rectification", the power flow from the load back to the power supply is called "active inverter". AC/DC converter input 50/60 Hz AC, because of the 50/60 Hz AC input, the power flow from the load to the load is called "active inverter". AC/DC converter input is 50/60Hz alternating current, because it must be rectified, filtered, so the relatively large filter capacitor is essential, and because of the encounter ** standards (such as UL, CCEE, etc.) and EMC directive limitations (such as IEC, FCC, CSA), the AC input side must be added to the EMC filtering and the use of components to meet the standard, which restricts the miniaturisation of the size of the AC/DC power supply, and in addition. Due to the internal high-frequency, high-voltage, high-current switching action, making it more difficult to solve the EMC electromagnetic compatibility problem, but also on the internal high-density installation circuit design puts forward high requirements, due to the same reason, high-voltage, high-current switching makes the power supply work consumption increases, limiting the process of modularity of the AC/DC converter, so it must be used in power supply system optimal design methods in order to make its efficiency To achieve a certain degree of satisfaction.
AC/DC converter can be divided into half-wave circuit and full-wave circuit according to the wiring of the circuit. According to the number of power supply phases can be divided into single, three-phase, multi-phase. According to the circuit operating quadrant can be divided into one quadrant, two quadrants, three quadrants, four quadrants.
