Highlights of switching power supply technology
1 Switching power supply power density.
Improving the power density of switching power supply, making it miniaturized and lightweight is the goal that people are constantly pursuing. This is especially important for portable electronic devices (such as mobile phones, digital cameras, etc.). There are several specific ways to miniaturize the switching power supply: one is high frequency. In order to achieve high power density of the power supply, the operating frequency of the PWM converter must be increased, thereby reducing the volume and weight of the energy storage components in the circuit. The second is the application of piezoelectric transformers. The application of piezoelectric transformers enables high-frequency power converters to be light, small, thin, and high in power density. Piezoelectric transformers use the unique properties of "voltage-vibration" transformation and "vibration-voltage" transformation of piezoelectric ceramic materials to transmit energy. Its equivalent circuit is like a series-parallel resonant circuit, and it is one of the research hotspots in the field of power conversion. The third is to use a new type of capacitor. In order to reduce the volume and weight of power electronic equipment, it is necessary to try to improve the performance of capacitors, increase energy density, and research and develop new capacitors suitable for power electronics and power systems, which require large capacitance and small equivalent series resistance (ESR). , small size, etc.
2. High frequency magnetic components.
A large number of magnetic components are used in the power system. The materials, structure and performance of high-frequency magnetic components are different from those of power frequency magnetic components. There are many problems to be studied. The magnetic materials used in high-frequency magnetic components are required to have low loss, good heat dissipation performance and superior magnetic performance. Magnetic materials suitable for megahertz frequencies have attracted people's attention, and nanocrystalline soft magnetic materials have also been developed and applied.
3. Synchronous rectification technology.
For low-voltage, high-current output soft-switching converters, the measure to further improve its efficiency is to try to reduce the on-state loss of the switch. For example, synchronous rectification (SR) technology, that is, the reverse connection of the power MOS tube is used as the switching diode for rectification instead of the Schottky diode (SBD), which can reduce the voltage drop of the tube, thereby improving the circuit efficiency.
4. Electromagnetic Compatibility.
The electromagnetic compatibility (EMC) problem of high-frequency switching power supply has its particularity. The di/dt and dv/dt generated by power semiconductor devices during the switching process will cause strong conducted electromagnetic interference and harmonic interference, as well as strong electromagnetic field (usually near field) radiation. Not only seriously pollute the surrounding electromagnetic environment, but also cause electromagnetic interference to nearby electrical equipment, and may also endanger the safety of nearby operators. At the same time, the control circuit inside the power electronic circuit (such as a switching converter) must also be able to withstand the EMI generated by the switching action and the electromagnetic noise interference of the application site. Many universities at home and abroad have carried out research on electromagnetic interference and electromagnetic compatibility of power electronic circuits, and have achieved many gratifying results.
