An Introduction to the Classification of Switching Power Supplies
The field of switch mode power supply technology is developing related power electronic devices while developing switch frequency conversion technology. The two mutually promote and drive the development of switch mode power supplies towards the direction of light, small, thin, low-noise, high reliability, and anti-interference with an annual growth rate exceeding two digits. Switching power supplies can be divided into two categories: AC/DC and DC/DC. DC/DC converters have now been modularized, and the design technology and production process have been mature and standardized both domestically and internationally, and have been recognized by users. However, the modularity of AC/DC, due to its own characteristics, encounters complex technical and process manufacturing problems in the process of modularization. The following elaborates on the structure and characteristics of two types of switching power supplies.
DC/DC conversion
DC/DC conversion is the process of converting a fixed DC voltage into a variable DC voltage, also known as DC chopping. There are two working modes of a chopper: one is the pulse width modulation mode, where Ts remains unchanged and ton is changed (universal), and the other is the frequency modulation mode, where ton remains unchanged and Ts is changed (prone to interference).
The specific circuits are divided into the following categories:
(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%.
