In recent years, the research on LED power supply and driving circuit by major companies and research institutes is in the ascendant. Different from electronic ballasts for fluorescent lamps, the main function of the LED power supply drive circuit is to convert AC voltage to DC voltage, and at the same time complete the matching of the voltage and current of the LED. With the linear decline of the power supply voltage of silicon integrated circuits, as a new light source, the operating voltage of LEDs is increasingly in the optimal range of power supply output voltage, and most of the technologies for powering low-voltage ICs are also suitable for LEDs , Especially high-power LED power supply. Furthermore, the LED power supply should also be able to take advantage of the economies of scale brought about by the gradual increase in the output of low-voltage IC power supplies.
Technology development trend
1) Develop a series of constant voltage and constant current control electronic circuits based on the characteristics of LEDs, and use integrated circuit technology to control the input current of each LED at the best current value, so that the LED can obtain a stable current and produce the highest output luminous flux. The LED drive circuit is best to control the size of the LED current when the input voltage, ambient temperature and other factors change.
2) In terms of control circuit design, it is necessary to develop in three aspects: centralized control, standard modularization, and system scalability.
3) In the current situation of limited LED luminous efficiency and luminous flux, give full play to the characteristics of LED color diversity, and develop color-changing LED lighting control circuits.
4) The LED drive circuit has an intelligent control function, so that the load current of the LED can be controlled at a pre-designed level under the influence of various factors. When the load current changes due to various factors, the primary control IC can control the switch to return the load current to the initial design value. LED fluorescent lamp power supply
LED power supply and driving circuit main technology overview
1) Voltage conversion technology
The power supply is an important part that affects the reliability and adaptability of the LED light source and must be considered. At present, the mains electricity in our country is 220V alternating current, and the LED light source is a semiconductor light source, which is usually powered by a low DC voltage. This requires an AC-DC conversion circuit in or outside of these lamps to adapt to the characteristics of the LED current drive. At present, there are many ways of power supply selection, such as switching power supply, high-frequency power supply, and rectified power supply after capacitor step-down. Different choices are made according to the different requirements of current stability, transient overshoot, safety and reliability.
2) Programmable technology of driver
A significant feature of LED used as a light source is that it can maintain its lumen efficiency under low drive current conditions. At the same time, for RGB polycrystalline light mixing to form white light, by developing a digital RGB hybrid control system for LEDs, Users can arbitrarily adjust the brightness, color and hue of LEDs in a wide range, giving people a brand-new visual enjoyment. In the application of urban landscape lighting, the LED light source can be changed in different modes under the control of the microprocessor to form a dynamic effect of various forms at night. In this respect, it will reflect the uniqueness of LED relative to other light sources. Competitive advantages. LED drive power.
3) Efficiency of power supply and drive circuit
The LED power supply and drive circuit must have a certain forward current output close to constant current required by the LED, but also have a higher conversion efficiency. The electro-optical conversion efficiency is an important factor in semiconductor lighting, otherwise the LED will be lost. With the advantages of energy saving, the efficiency of the current commercial switching power supply is about 80%. As a power supply for semiconductor lighting, its conversion efficiency still needs to be further improved.
4) Life and cost of LED power supply and drive circuit
In terms of LED life, although the life of a single LED is as long as 100,000 hours, its application must be equipped with a power conversion circuit, so the overall life of LED lighting must be considered from the application of photoelectric integration. But for lighting LEDs, in order to meet the matching requirements, the lifespan of the power supply and the driving circuit must exceed 100,000 hours, so that it no longer becomes a bottleneck factor in the semiconductor lighting system. While considering the long life, it is not necessary to increase the cost too much. The life and cost of the power supply and driving circuit should not exceed one third of the total cost of the lighting system. In the early stage of the development of semiconductor lighting products, it is necessary to balance the power supply and the cost. The relationship between the life of the drive circuit and the cost.
