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 unchanged, the ton is changed, and the other is the frequency modulation mode. The ton is unchanged and the Ts is changed (prone to interference). Its specific circuit consists of the following categories:
(1) Buck circuit - step-down chopper, whose output average voltage Uo is smaller than the input voltage Ui, and the polarity is the same.
(2) Boost circuit - boost chopper, whose 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, whose 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, whose 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 makes a qualitative leap in DC/DC. The 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)%. Japan's NemicLambda Corporation recently introduced a high-frequency switching power supply module RM series using soft switching technology. Its switching frequency is (200~300) kHz, the power density has reached 27 W/cm3, and synchronous rectifier (MOS-FET is used instead of Shaw). The special base diode) is the overall circuit efficiency increased to 90%.