Technical knowledge of LED power supply and drive circuit

Time:2018-11-29 Views:140

The main function of LED drive circuit is to convert ac voltage into dc voltage, and complete the matching with LED voltage and current at the same time.As the power supply voltage of silicon integrated circuit drops linearly, LED working voltage is more and more in the optimal range of power supply output voltage. Most technologies for low-voltage IC power supply are also applicable to LED, especially for high-power LED power supply.Moreover, LED power supply should also be able to take advantage of the low voltage IC power supply output to gradually increase the economies of scale.

(1) main technical overview of LED power supply and drive circuit

1) voltage conversion technology

Power supply is an important component that affects the reliability and adaptability of LED light source.At present, the municipal power of our country is 220V alternating current, and LED light source belongs to semiconductor light source, which is usually supplied with low DC voltage, which requires that AC-DC conversion circuit be set in or outside these lamps to adapt to the characteristics of LED current drive.Currently, switching power supply, high-frequency power supply, capacitor step-down rectification power supply and other options are available for power supply selection. Different choices are made according to the requirements of current stability, transient overshoot, safety and reliability.

2) life and cost of power supply and driving circuit

In terms of LED life, although the life of a single LED itself is as long as 100,000 hours, it must be equipped with power supply conversion circuit when it is applied, so the overall life of LED lighting appliance must be considered from the photoelectric integration application.But for lighting LED, in order to meet the matching requirements, the life of power supply and drive circuit must exceed 100,000 hours, so that it no longer becomes the bottleneck factor of semiconductor lighting system.In consideration of long life and at the same time cannot increase too much cost, the life of power supply and drive circuit and cost usually should not exceed 1/3 of the total cost of lighting system, in the early stage of semiconductor lighting lamps and lanterns product development, must balance the relationship between power supply and drive circuit life and cost.

3) programmable technology of driver

LED as light source, a remarkable characteristic is under the condition of low drive current can still maintain its lumen efficiency, at the same time for R.G.B type polycrystalline mixed to form white light, the light through the development of a digital RGB hybrid control system for the LED, enabling users to in large range of LED brightness, color and color adjusted, give a person with a kind of brand-new visual enjoyment.In the application of urban landscape lighting, LED light sources can be changed according to different modes under the control of microprocessors to form a dynamic effect with diverse forms at night, which will reflect the unique competitive advantage of LED compared with other light sources.

4) power supply and drive circuit efficiency

LED power supply and drive circuit, both must have certain required for LED to the constant current forward current output, and high conversion efficiency, electro-optic conversion efficiency is an important factor of semiconductor lighting, or you will lose the advantages of LED energy saving, the commercialization of switch power supply, its efficiency is about 80%, as a semiconductor lighting power supply, its conversion efficiency will be further ascension.

(2) technology development trend

1) a series of constant voltage and constant current control electronic circuits are developed according to the characteristics of LED. Integrated circuit technology is used to control the input current of each LED at the optimal current value, so that LED can obtain stable current and produce the highest output light flux.LED drive circuit in the input voltage and environmental temperature and other factors change, it is best to control the size of LED current.

2) LED drive circuit has intelligent control function, so that the load current of LED can be controlled at the pre-designed level under the influence of various factors.When the load current changes due to various factors, the primary control IC can make the load current return to the original design value by controlling the switch.

3) in the aspect of control circuit circuit design, centralized control, standard modularization and system scalability should be developed.

4) in the current situation of limited LED light efficiency and flux, give full play to the characteristics of LED color diversity, and develop the control circuit of color-changing LED lighting.