DC/DC two categories, DC/DC converter has realized modularization, and the design technology and production process at home and abroad have been mature and standardized, and has been recognized by users, but the modularization of AC/DC, because of its own characteristics in the process of modularization, encounter more complex technology and process manufacturing problems. The structure and characteristics of the two types of switching power supply are described below
DC/DC conversion is the conversion of a variable DC voltage into a fixed DC voltage, also known as DC chopper. Chopper working mode has two, one is the pulse width modulation mode Ts unchanged, change ton(universal), the other is frequency modulation (
(1) Buck circuit – buck chopper, the output average voltage U0 is less than the input voltage Ui, the polarity is the same.
(2) Boost circuit — boost chopper, the output average voltage U0 is greater than the input voltage Ui, the polarity is the same.
(3) Buck-boost circuit — Buck or Boost chopper, whose output average voltage U0 is greater than or less than the input voltage Ui, polarity is opposite, inductive transmission.
(4) Cuk circuit – buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the polarity is opposite, capacitor transmission. There are Sepic and Zeta circuits.
The above is a non-isolated DC-DC converter circuit. The isolated DC-DC converter includes forward circuit, flyback circuit, half-bridge circuit, full-bridge circuit and push-pull circuit.
Today’s soft switching technology has made a qualitative leap in DC/DC. VICOR has designed and manufactured a variety of ECI soft switching DC/DC converters, whose maximum output power is 300W, 600W, 800W, etc. The corresponding power density is (6.2, 10, 17)W/cm3, and the efficiency is (80 ~ 90) %. The RM series of high frequency switching power module, which adopts soft switching technology, launched by TDK-Lambda in Japan, has a switching frequency of (200 ~ 300)kHz and a power density of 27W/cm3. By using synchronous rectifier (MOSFET instead of Schottky diode), the efficiency of the whole circuit is improved to 90%.