What is the classification and principle of switching power supplies?
A switching power supply is a device that uses a circuit to control the switch tube for high-speed channel on and off. It converts direct current into high-frequency alternating current and provides it to a transformer for voltage transformation, thereby generating the required set or sets of voltages! The reason for switching to Huawei's high-frequency AC power is that the efficiency of high-frequency AC in the transformer transformation circuit is much higher than that of 50HZ. Therefore, switching transformers can be made very small and not very hot when working! The cost is very low. If 50HZ is not converted to high-frequency, then the switching power supply is meaningless!! Switching transformers are not mysterious. They are just ordinary transformers! This is the switching power supply. Switching power supplies can generally be divided into two types: isolated and non isolated. The isolated type must have a switching transformer, while the non isolated type may not necessarily have one.
When the power is the same, the higher the switching frequency, the smaller the volume of the switching transformer, but the higher the requirement for the switching transistor; The secondary of a switching transformer can have multiple windings or one winding with multiple taps to obtain the required output; Generally, some protective circuits should also be added, such as no-load and short circuit protection, otherwise it may burn out the switch power supply.
Classification of Switching Power Supplies
People's field of switch power supply technology is to develop related power electronic devices while developing switch frequency conversion technology. The mutual promotion of the two promotes the development of switch power supplies towards light, small, thin, low noise, high reliability, and anti-interference with a growth rate of over two digits each year. Switching power supplies can be divided into two categories: AC/DC and DC/DC. DC/DC converters have now achieved modularization, and the design technology and production process have been mature and standardized both domestically and internationally, and have been recognized by users. However, the modularization of AC/DC, due to its own characteristics, encounters more complex technical and manufacturing problems in the process of modularization. The structure and characteristics of two types of switching power supplies are explained below.
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 ways in which choppers work: one is to keep the pulse width modulation mode Ts unchanged and change T (universal), and the other is to keep the frequency modulation mode T unchanged and change T (prone to interference).
The specific circuits are divided into the following categories:
(1) Buck circuit - a buck chopper with an average output voltage Uo smaller than the input voltage Ui and the same polarity.
(2) Boost circuit - a boost chopper with an average output voltage Uo greater than the input voltage Ui and the same polarity.
(3) Buck Boost circuit - a buck or boost chopper with an average output voltage Uo greater than or less than the input voltage Ui, opposite polarity, and inductive transmission.
(4) Cuk circuit - a buck or boost chopper with an average output voltage Uo greater than or less than the input voltage UI, opposite polarity, and capacitor transmission. Today's soft switching technology has made a qualitative leap in DC/DC. VICOR Company in the United States has designed and manufactured various ECI soft switching DC/DC converters, with maximum output power of 300W, 600W, 800W, etc. The corresponding power density is (6, 2, 10, 17) W/cm3, and the efficiency is (80-90)%. The latest high-frequency switching power module RM series launched by Japanese company NemicLambda 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 efficiency of the entire circuit to 90%.
