LED drive power knowledge

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

 

LED drive power is also a matching product, the market power quality 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 AC (ie, electricity), low voltage direct current, high voltage direct current, AC (such as the output of electronic transformers). While the LED drive power output is the majority of the LED forward voltage drop with the change in the value of the constant current source voltage change. LED power core components include switch controller, inductor, switch components (MOSfet), feedback resistor, input filter, output filter devices and so on. According to different occasions, but also input overvoltage protection circuit, input undervoltage protection circuit, LED open circuit protection, overcurrent protection circuit.

 

2, LED drive power characteristics

 

(1) high reliability

 

In particular, like LED lights drive power, installed in high altitude, maintenance is not convenient, the cost of maintenance is also large.

 

(2) high efficiency

 

LED is energy-saving products, drive power to be more efficient. For the power supply installed in the lamp within the junction cooling is very important. Power efficiency, its power consumption is small, the heat in the lamp is small, it will reduce the temperature rise of the lamp. To delay the decline of LED light favor.

 

(3) high power factor

 

Power factor is the load of the power grid requirements. General 70 watts of the following electrical appliances, there is no mandatory indicators. Although the power is not a single power factor with a little lower impact on the power grid, but the use of large amount of lighting at night, the same load is too concentrated, the grid will have more serious pollution. For 30 watts to 40 watts of LED drive power, it is said that in the near future, there may be some power factor indicators.

 

(4) drive mode

 

Now there are two: one is a constant voltage source for multiple constant current source, each constant current source to each LED power supply alone. In 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 change the drive mode, LED series or parallel operation. It has the advantage of low cost, but the flexibility is poor, but also to solve a LED failure, does not affect the other LED operation problems. These two forms, coexist in a period of time. Multi-channel constant current output power supply, 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. Strengthening protection in this area is also important. Some LED lights installed in the outdoors, such as LED lights. As the load of the grid is switched on and struck by lightning, the grid system invades various surges, and some surges can cause LED damage. Therefore, the analysis of the power of the Division in the surge protection should be a certain lack of protection, and as the power and frequent replacement of lamps, LED drive power to inhibit the intrusion of the surge to protect the LED is not damaged.

 

(6) protection

 

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

 

3, according to drive classification

 

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

 

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

 

4, the overall constant-current and by-way constant current work advantages and disadvantages

 

Compared with the overall constant current, by-way constant current although more shortcomings, the cost is relatively high. But it can really play to protect the LED and extend the life of the LED, so the road by constant current is the future trend.

 

5, LED power shortage

 

LED drive power is currently the reason for the shortage:

 

First, the production of LED lighting and related products, the company's technical staff of the switching power supply is not enough to make the power supply is working, but some of the key assessment and consideration of electromagnetic compatibility is not enough, or have some hidden dangers;

 

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

 

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

 

Fourth, LED power supply stability: wide voltage input, high temperature and low temperature work, over-temperature, over-voltage protection and other issues are not resolved.

 

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 a higher conversion efficiency, especially when driving high power LED, especially because All not as light output power as heat dissipation, power conversion efficiency is too low, affecting the LED energy-saving effect of play. Currently in the power of small (1-5W) applications, the proportion of constant current drive power costs have been close to 1/3, has been close to the cost of light, to some extent affected the marketing.

 

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