What are the design parameters of LED switching power supply? What exactly does it represent?

1. Power density of LED switching power supply

To improve the power density of switching power supply, to make it small and lightweight, is the goal that people constantly pursue. This is especially important for portable electronic devices such as mobile phones, digital cameras, etc. The specific ways to miniaturize switching power supply are as follows.

One is high-frequency. In order to achieve high power density of the power supply, the working frequency of PWM converter must be increased, thus reducing the volume weight of the energy storage components in the circuit.

The second is the application of piezoelectric transformer. The application of piezoelectric transformer can make the high-frequency power converter light, small, thin and high power density. The piezoelectric transformer uses the characteristic voltage-vibration and vibration-voltage transformation properties of piezoelectric ceramic materials to transmit energy. Its equivalent circuit is like a series-parallel resonant circuit, which is one of the research hotspots in the field of power transformation.

Third, the use of new capacitors. In order to reduce the volume and weight of power electronic equipment, it is necessary to try to improve the performance of capacitors, improve the energy density, and research and development of new capacitors suitable for power electronics and power system, requiring large capacitance, small equivalent series resistance (ESR), small size, etc.

2, LED switching power supply in the selection of high-frequency magnetic components

A large number of magnetic components are used in LED switching power supply system. The materials, structure and properties of high-frequency magnetic components are different from those of power frequency magnetic components, so 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 properties. Magnetic materials that are suitable for megahertz frequency have attracted much attention. Nano-crystalline soft magnetic materials have also been developed and applied.

3. Application of soft switching technology after high frequency conversion of LED switching power supply

In order to improve the efficiency of LED switching power supply, soft switching technology must be developed and applied. It is a research hotspot in the international power supply field in the past decades.

The PWM-LED switching power supply works in hard switching mode (voltage down/up and current up/down waveform overlap during on/off), so the switching loss is large. Although the high frequency can reduce the size and weight, but the switching loss is greater. Therefore, it is necessary to study the technology of non-overlapping switching voltage/current waveform, namely the so-called zero voltage switch (ZVS)/ zero current switch (ZCS) technology, or soft switching technology, low power soft LED switching power efficiency can be increased to 80%~85%. The resonant switching power supply in the 1970s laid the foundation for soft switching technology. Then new soft switching technologies emerged, such as quasi-resonant (mid-1980s) full-bridge phase-shifting ZVS-PWM, constant-frequency ZVS-PWM/ZCS-PWM(late 1980s)ZVS-PWM active embedding; ZVT-PWM/ZCT-PWM(early 1990s) full bridge phase shift ZV-ZCS-PWM(mid 1990s) etc. The latest soft switching technology has been applied in 6kW communication power supply, with an efficiency of 93%.

4. Synchronous rectification technology is used in LED switching power supply

Synchronous rectification technology is used in LED switching power supply. Compared with soft switching converter with low voltage and high current output, 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, reverse connection of power MOS tube as switching diode for rectification, instead of Schottky diode (SBD), can reduce the tube voltage drop, so as to improve the efficiency of LED switching power supply circuit.

5, LED switching power factor correction (PFC) converter application

Power factor correction (PFC) converter applications in LED switching power supply. Since the input end of AC/DC conversion circuit has rectifier devices and filter capacitors, when the sinusoidal voltage is input, the power factor of the grid side (AC input end) is only 0 for the electronic equipment supplied by single-phase rectifier power supply. 6-0. Sixty-five. With power factor correction (PFC) converter, the power factor of the network side can be increased to 0. 95 to 0. 99, input current. Ten percent. Not only the harmonic pollution to the grid is controlled, but also the overall efficiency of the power supply is improved. This technique is called active power factor correction (APFC).

6. Full digital control of LED switching power supply

The control of LED switching power supply has been from analog control, analog - digital mixed control, into the full digital control stage. Full digital control is a developing trend and has been used in many power conversion devices.

The advantage of full digital control is that the digital signal can calibrate smaller quantity compared with the mixed module signal, and the chip price is also lower. The error of current detection can be corrected accurately, and the voltage detection is more accurate. Can achieve fast, flexible control design.

7. Electromagnetic compatibility of LED switching power supply

Electromagnetic compatibility of LED switching power supply: Electromagnetic compatibility (EMC) of high frequency LED switching power supply has its particularity. The di/dt and dv/dt generated in the switching process of power semiconductor devices will cause strong conducted electromagnetic interference and harmonic interference, as well as strong electromagnetic field (usually near field) radiation. It not only seriously pollutes the surrounding electromagnetic environment, causes electromagnetic interference to nearby electrical equipment, but also endangers the safety of nearby operators. At the same time, the control circuit inside the power electronic circuit (such as switching converter) must also be able to withstand the EMI generated by the switching action and the electromagnetic noise of the application site. The particularity mentioned above, coupled with the specific difficulties in EMI measurement, there are many interdisciplinary frontier topics to be studied in the electromagnetic compatibility field of power electronics.

8. LED switching power supply design and test technology

LED switching power system CAD, 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. It is one of the development directions of simulation and CAD technology in 21st century to use the expert system based on simulation to CAD LED switching power system, which can make the designed system performance optimal, reduce the design and manufacturing costs, and make manufacturability analysis. In addition, the development, research and application of LED switching power system thermal test, EMI test, reliability test and other technologies should also be vigorously developed.

9. LED switching power system integration technology

LED switching power supply system integration technology ED power supply equipment manufacturing characteristics of non-standard parts, high labor intensity, long design cycle, high cost, low reliability, and users require manufacturers to produce LED switching power products more practical, higher reliability, lighter, lower cost. These conditions make LED switching power supply manufacturers under great pressure, and it is urgent to carry out research and development of integrated LED switching power supply module, so as to achieve the standardization, modularization, manufacturability, scale production, cost reduction and other goals of LED switching power supply products.

In fact, in the development process of LED switching power supply integration technology, has gone through the modular power semiconductor devices, power and control circuit integration, integrated passive components (including magnetic integration technology) and other development stages. In recent years, the development direction is to integrate the low-power LED switching power supply system on a chip, which can make the LED switching power supply products more compact, smaller volume, but also reduce the length of the lead, thus reducing the parasitic parameters. On this basis, integration can be achieved, all components together with control protection integrated in one module.