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LED drive power knowledge

May 08, 2017

Cooling, drive power, light source is a key part of making LED lighting products the most critical. Although the heat is particularly important, the cooling effect directly affects the quality of life of lighting products, but the light source is the core of the entire product, driving the power supply itself, the life and output current, voltage stability of the product's overall life quality also has a great impact.

LED drive power is also a complementary product, the current power quality on the market uneven, the following provides some LED drive power related knowledge.

1.What is the LED drive power

LED drive power to convert the power supply to a specific voltage and current to drive the LED light-emitting voltage converter, usually: LED drive power input, including high-voltage power frequency AC (ie, electricity), low voltage DC, high voltage DC, low voltage Exchange (such as the output of electronic transformers) and so on. While the LED drive power output is mostly with the LED forward voltage drop to change the voltage constant current source. LED power supply core components include switch controller, inductor, switch components (MOSfet), feedback resistor, input filter, output filter and so on. According to different occasions, but also have input overvoltage protection circuit, input undervoltage protection circuit, LED open circuit protection, overcurrent protection and other circuits.

2.LED drive power characteristics

(1) Highly reliable

Especially as LED lights drive power, installed at high altitude, maintenance is not convenient, maintenance costs are also large.

(2) High efficiency

LED is energy-saving products, drive power efficiency is higher. It is very important for the power supply to be installed in the fixture. Power efficiency is high, its power consumption is small, in the lamp heat is small, it will reduce the lamp temperature. To delay the LED light failure beneficial.

(3) High power factor

The power factor is the load on the grid. Generally less than 70 watts of electrical appliances, there is no mandatory indicators. Although the power is not a single power factor lower power factor little effect on the power grid, but the use of large amount of light at night, the same type of load is too concentrated, the grid will produce more serious pollution. For 30 watts to 40 watts of LED drive power, it is said that in the near future, may have a certain degree of power factor requirements.

(4) drive mode

Now there are two kinds of traffic: one is a constant pressure source for a number of constant current source, each constant current source to each LED power supply. This way, the combination of flexible, all the way LED failure, does not affect the work of other LED, but the cost will be slightly higher. The other is a direct constant current power supply is "in the Division Huibao" to use the drive mode, LED series or parallel operation. Its advantage is a little lower cost, but the flexibility is poor, but also to solve an LED failure, does not affect the other LED operation problems. These two forms coexist for a period of time. Multi-channel constant current output power supply, in terms of cost and performance will be better. Perhaps the future direction of the mainstream.

(5) Surge protection

LED anti-surge capability is relatively poor, especially anti-reverse voltage capability. It is also important to strengthen this protection. Some LED lights installed in the outdoors, such as LED lights. Due to the load of the grid load and lightning induction, from the grid system will invade a variety of surges, and some surge will lead to LED damage. Therefore, the analysis of "in the Division Huibao" drive power in the surge protection should have a certain lack of, and as the frequent replacement of power and lighting, LED drive power to suppress the surge of intrusion, the protection of LED is not damaged capacity.

(6) Protection function

Power supply In addition to the conventional protection function, it is best to increase the constant current output LED temperature negative feedback to prevent the LED temperature is too high; to comply with safety and electromagnetic compatibility requirements.

3.By driving the classification

(1) constant current constant current drive circuit output current is constant, and the output of the DC voltage with the load resistance of the size of the different changes in a certain range, the load resistance is small, the output voltage is low, load resistance The constant current drive circuit is very ideal, but relatively high prices; should pay attention to the use of the maximum withstand current and the use of the current is very high, the higher the output voltage is higher; constant current circuit is not afraid of load short circuit, Voltage value, which limits the number of LEDs used.

(2) Regulator voltage regulator circuit in the parameters determined, the output voltage is fixed, and the output current with the load increases or decreases; voltage regulator circuit is not afraid of load open, but the load is strictly prohibited Short circuit; to drive the driver circuit to drive the LED, each string need to add the appropriate resistance to each string of LED display brightness average; brightness will be affected by the rectification of the voltage changes.

4.The overall constant current and constant current way of dealing with the advantages and disadvantages

Compared with the overall constant current, the road constant current although the shortcomings are more cost is relatively high. But it can really play a protective LED and extend the life of the LED, so the road is the future trend of constant current.

5. LED power shortage

LED drive power is currently undercritical reasons:

First, the production of LED lighting and related products, the company's technical staff on the switching power supply is not enough understanding of the power to make the normal work, but some of the key assessment and electromagnetic compatibility is not enough, there must be hidden;

Second, most of the LED power supply manufacturers are switching from the ordinary switching power supply to do LED power, the characteristics of the use of LED and understanding is not enough;

Third, the current standard on the LED almost no, most of the reference switching power supply and electronic rectifier standards; now most of the LED power supply is not uniform, so most of the smaller. Purchase volume is small, the price is high, and component suppliers are not with the;

Fourth, the stability of LED power: wide voltage input, high temperature and low temperature work, over temperature, overvoltage protection and other issues are not resolved one by one.

The first is the overall life of the drive circuit, especially the key components such as: the life of the capacitor at high temperatures directly affect the life of the power supply; LED driver should challenge the higher conversion efficiency, especially in driving high power LED even more so, because All the power is not as a light output as heat dissipation, power conversion efficiency is too low, affecting the LED energy-saving effect play. Currently in the smaller power (1-5W) applications, the proportion of constant current drive power costs have been close to 1/3, has been close to the cost of the light source, to some extent affected the marketing.




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