Switching Power Converters Distribute Power

　　Providing various adjustable, stable and reliable power supplies for communications, computers, ships, artificial satellites, spacecraft, industry, transportation and other departments is an important application of switching power supplies .

　　As for the communication power supply system, the required DC power supply types are various, such as DC 48V, 12V, 5V, 3V, 1V, etc., as well as AC voltage and ringing current power supply of different frequencies. In the early days, the centralized power supply structure (Centralized Power Architecture) was adopted to directly convert 220V AC into 5V DC through AC/DC rectifier converter . This requires a 5V DC bus, and due to the low voltage, the bus current is large, the voltage loss and circuit loss are also large. Therefore, the distributed power supply structure (Distributed Power Architecture) is used instead of the centralized power supply structure to avoid the above problems.

The distributed power supply structure is to supply power to the load board (Board)  　　through a 250~425V/48V DC/DC converter and a 48V bus voltage, and then convert the 48V into the 3~5V required by the load through several parallel thin DC/DC converters on the board (ON board) . Generally, the power density of the DC/DC converter can reach 100W/in3, the efficiency is 90%, and it should be parallelable. The distributed power supply system is suitable for large workstations composed of ultra-high-speed integrated circuits (such as image processing stations), large digital AC systems, etc. Its advantages are that it can realize the modularization of DC/DC converter components; it is easy to achieve N+1 power redundancy and improve the reliability of the system; it is easy to expand the load capacity; it can reduce the current and voltage drop on the 48 V bus; it is easy to achieve uniform heat distribution, which is convenient for heat dissipation design; it has good transient response and can replace failed modules online, etc.

　　There are two types of distributed power supply systems.

　　1) Two-level structure

　　It consists of a front-end converter and a point of load (POL) converter. The front-end converter outputs 48V and supplies power to several parallel isolated POL converters or load converters through a 48V bus. When the load is a microprocessor, the DC/DC converter that supplies power is called a voltage regulator module (VRM), and its output voltage may be lower, such as 5V, 3V, 1V, etc.

　　2) Tertiary structure

　　It consists of three stages: a front-end converter, an intermediate bus converter, and a load converter. The 48V bus supplies power to the isolated intermediate bus converter, which outputs 12V. The 12V intermediate bus then supplies power to several parallel non-isolated load converters or VRMs to output the voltage required by the load.

　　According to Synqor, a US company, the cost of a three-stage distributed power supply structure is reduced by half compared to a two-stage distributed power supply structure. Each stage of the converter can be composed of multiple converters in parallel. Through current sharing control, each parallel module can share the load power evenly.

　　The front-end converter includes an AC/DC rectifier, a PFC power factor correction converter, outputs 400V DC, and a DC/DC converter (outputs 48V DC). The load converter is a standard module structure. The technical requirements for the module are: high efficiency, high power density, wide output voltage adjustment range, wide operating temperature range, and current limiting protection.