(2) Classification of switching power supplies
According to the conversion method, the power supply products have the following four categories;
(1): The first category: AC/DC switching power supply;
(2): The second category: DC/DC switching power supply;
(3): The third category : DC/AC switching power supply;
(4): The fourth category: AC/AC switching power supply.
In view of the tradition, only the first two types are called switching power supplies at present, while the latter two types are called inverters and frequency converters.
In China, these four types of power products are collectively referred to as power electronic products.
In fact, for the above four types of products, the relatively accurate name should be power supply products or power conversion products.
Therefore, as a switching power supply, there are mainly two categories: AC/DC and DC/DC. The DC/DC converter as the secondary power supply has been modularized, and the design technology and production process have been mature and standardized at home and abroad, and have been recognized by users. However, the primary power supply AC/DC, due to its own characteristics, encounters relatively complicated technical problems and process manufacturing problems in the process of modularization.
1. DC/DC switching power supply
The DC/DC switching power supply converts a fixed DC voltage into a variable DC voltage, also known as a DC chopper. Choppers work in two ways:
One is that the pulse width modulation mode T remains unchanged, and the frequency modulation mode t is changed (general purpose);
the other is that the frequency modulation mode t is unchanged but T is changed (easy to generate interference). The specific circuits are as follows:
①Buck circuit – step-down chopper, which outputs an average voltage U. Less than the input voltage Uo, the polarity output is the same;
②Boost circuit-boost chopper, which outputs the average voltage U. Greater than the input voltage Up, the polarity output is the same;
③Buck-Boost circuit – buck-boost chopper, which outputs an average voltage U. Greater or less than the input voltage Uo, the polarity output is opposite, and the inductance is transmitted;
④Cuk circuit – a step-down or step-up chopper, which outputs an average voltage U. Greater or less than the input voltage Up, the polarity output is reversed, and the capacitance is transmitted.
Today's soft switching technology has made a qualitative leap in DC/DC converters. Various ECI soft-switching DC/DC converters designed and manufactured by American VICOR switching power supply company, the maximum output power is 300W, 600W, 800W, etc., the corresponding power density is 6.2W/cm3, 10W/cm3, 17W/cm3, the efficiency 80% -90%. The RM series of high-frequency switching power supply modules newly launched by Japan Nemic Lambda Company adopts soft switching technology. Its switching frequency is 200~300kHz, and its power density has reached 27W/cm3. , so that the efficiency of the entire circuit can be increased to 90%.
2.AC/DC Converter
The AC/DC converter converts AC to DC, and its power current flow can be bidirectional. The transformation of power current flowing to the load is called "rectification", and the power current is transmitted from the load back to the power source is called "active inverter".
AC/DC converters can be divided into half-wave circuits and full-wave circuits according to the wiring method of the circuit; according to the control characteristics of the circuit, they can be divided into three types: uncontrollable, half-control and full-control; according to the number of power supply phases, they can be divided into single-phase , Three-phase and multi-phase; According to the circuit working quadrant, it can be divided into one quadrant, two quadrants, three quadrants and four quadrants.
3. Circuit structure classification
Switching power supplies are mainly divided into the following types according to the circuit structure:
①According to the driving mode, there are self-excited and separately-excited;
②According to the working mode of the DC/DC converter, there are single-ended positive excitation type and flyback type, push-pull type, half-bridge type, full-bridge type, buck type, boost type and buck-boost type, etc.;
③ According to the circuit composition, there are resonant type and non-resonant type;
④ According to the control mode, there are pulse width modulation (PWM) type: pulse frequency modulation (PFM) type and PWM and PFM hybrid type;
⑤ According to whether the power supply is isolated or not and the feedback control signal coupling method, there are isolated, non-isolated, transformer coupled, photoelectric coupled, etc.
The combination of the above methods can constitute a variety of switching-type regulated power supplies. Therefore, the designer needs to effectively combine the characteristics of various methods to produce a high-quality switching power supply that meets the needs.
4. Classification of power switch tubes
① Transistor;
②Thyristor;
③ MOSFET tube;
④IGBT switching power supply.
5. Classification of circuit topology
①Buck step-down;
②Boost boost;
③Buck-Boost buck-boost;
④Flyback flyback;
⑤ Forward
⑥Two-Transistor Forward double transistor forward;
⑦Push-Pull push-pull;
⑧Half Bridge half bridge;
⑨Full Bridge full bridge;
⑩SEPIC；
⑪C’uk。
