Introduction to switching power supply technology
1. Power Factor Correction (PFC) converter.
Since the input end of the AC/DC conversion circuit has a rectifier device and a filter capacitor, when the sinusoidal voltage is input, the power factor of the power grid side (AC input end) of the electronic equipment powered by a single-phase rectifier power supply is only 0.6~0.65. Using a power factor correction (PFC) converter, the power factor of the grid side can be increased to 0.95~0.99, and the input current THD<10%. It not only controls the harmonic pollution to the power grid, but also improves the overall efficiency of the power supply. This technology is called active power factor correction (APFC). Single-phase APFC was developed earlier at home and abroad, and the technology is relatively mature; although there are many types of topology and control strategies for three-phase APFC, it still needs to be further researched and developed. Generally, high power factor AC/DC switching power supply is composed of two-stage topology. For low-power AC/DC switching power supply, the overall efficiency of two-stage topology is low and the cost is high. If the requirements for the power factor of the input end are not particularly high, the PFC converter and the subsequent DC/DC converter are combined into a topology to form a single-stage high power factor AC/DC switching power supply, and only one main switch tube can be used. The power factor is corrected to more than 0.8, and the output DC voltage is adjustable. This topology is called a single-tube single-stage PFC converter.
2. Full digital control.
The control of the power supply has changed from analog control to analog-digital hybrid control, and has entered the stage of full digital control. The advantage of full digital control is that digital signals can be calibrated smaller than mixed analog-digital signals, and the chip price is also cheaper; accurate digital correction can be made for current detection errors, and voltage detection is also more accurate; fast and flexible control design. In the past two years, high-performance all-digital control chips have been developed, and the cost has been reduced to a relatively reasonable level. Many companies in Europe and the United States have developed and manufactured digital control chips and software for switching converters.
3. Design and test technology.
Modeling, simulation and CAD are a new design research tool. In order to simulate the power system, the simulation model must first be established, including power electronic devices, converter circuits, digital and analog control circuits, magnetic components and magnetic field distribution models, etc., and the thermal model, reliability model and EMC model of the switch tube should also be considered. Various models are very different, and the development direction of modeling is digital-analog hybrid modeling, hybrid hierarchical modeling, and combining various models into a unified multi-level model.
CAD of power system, including main circuit and control circuit design, device selection, parameter optimization, magnetic design, thermal design, EMI design and printed circuit board design, reliability prediction, computer-aided synthesis and optimization design, etc. Using simulation-based expert system for power system CAD can optimize the performance of the designed system, reduce design and manufacturing costs, and do manufacturability analysis.
