How many types of specific circuits are there for switching power supplies?
(1) Buck circuit - a step-down chopper whose average output voltage Uo is lower than the input voltage Ui and has the same polarity.
(2) Boost circuit - a boost chopper whose output average voltage Uo is greater than the input voltage Ui and has the same polarity.
(3) Buck Boost circuit - a step-down or step-up chopper whose output average voltage Uo is greater or less than the input voltage Ui, with opposite polarity and inductive transmission.
(4) Cuk circuit - a step-down or step-up chopper, whose output average voltage Uo is greater or less than the input voltage UI, with opposite polarity and capacitive transmission. Today's soft switching technology has led to a qualitative leap in DC/DC, with various ECI soft switching DC/DC converters designed and manufactured by VICOR Corporation in the United States having maximum output powers of 300W, 600W, 800W, etc., corresponding power densities of (6, 2, 10, 17) W/cm3, and efficiencies of (80-90)%. The latest high-frequency switching power module RM series launched by NemicLambda in Japan adopts soft switching technology, with a switching frequency of (200~300) kHz and a power density of 27 W/cm3. It uses synchronous rectifiers (MOS-FET instead of Schottky diodes), which improves the overall circuit efficiency to 90%.
AC/DC conversion
AC/DC conversion is the process of converting alternating current into direct current, 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 an AC/DC converter is 50/60Hz AC power, which must be rectified and filtered. Therefore, a relatively large filtering capacitor is essential. At the same time, due to the limitations of safety standards (such as UL, CCEE, etc.) and EMC directives (such as IEC, FCC, CSA), The AC input side must be equipped with EMC filtering and use components that meet safety standards, which limits the miniaturization of AC/DC power supply volume. In addition, due to the high-frequency, high-voltage, and high current switch actions inside, it is more difficult to solve EMC electromagnetic compatibility problems, which puts high demands on the high-density installation circuit design inside. For the same reason, high-voltage and high current switches increase the power consumption and limit the modularization process of AC/DC converters. Therefore, power system optimization design methods must be adopted to achieve a certain level of satisfactory working efficiency.
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 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 quadrant one, quadrant two, quadrant three, and quadrant four.
