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A detailed LED drive power features and disadvantages - (AddTime - 2013-01-24)

1, what is LED drive power
Led drive power supply the power supply into specific voltage current drive led luminous voltage converter, usually: led drive power input including high pressure power frequency ac (namely mains), low voltage dc high-voltage direct current, low voltage, high frequency ac (such as electronic transformer output), etc. And LED drive power output is most for LED with positive pressure drop value change and change the voltage of the constant current source. LED power core element including switch controller, inductor, switch components (MOSfet), the feedback resistance, input filter parts, output filter parts, etc. According to different occasions requirements, have input overvoltage protection circuit, input under-voltage protection circuit, LED open circuit protection, over current protection circuit.
2, LED drive power characteristics
(1) high reliability
Special like LED street lamp driver power supply, installed in high altitude, maintenance is convenient, the cost of maintenance is also big. (2) high efficiency
LED is energy saving products, drive power efficiency should be high. For power installed in within the lamps and lanterns and heat dissipation is very important. Power efficiency is high, it is the loss of power is small, the lamps and lanterns is small, also in calorific value is to reduce the temperature of lamps and lanterns. LED to delay the light of the favorable failure.
(3) high power factor
Power factor is the grid load requirements. The following general 70 watts of appliances, there is no mandatory indicators. Although the power is not a single use electric power factor lower on the influence of the power grid is not big, but use at night lighting quantity is big, the same load is too concentrated, will power to produce more serious pollution. For 30 tile ~ and tile LED drive power supply, it is said that in the near future, may be to power factors have certain parameters.
(4) driving mode
Now going to have two kinds: one is a constant voltage source for more constant current source, each constant current source to each individual LED power supply. This way, the combination of agile, LED failure, do not affect other LED work, but the cost will be slightly a little higher. Another kind is direct constant current power supply is also "zhongke hui treasure" the driving mode, the LED series or parallel operation. It has the advantage of low cost a little, but low agility, but also solve a LED failure, do not affect other LED operation problems. The two forms, both in a period of time. Multiple constant current output power supply mode, in the cost and performance will be better. Perhaps is the mainstream of the future direction.
(5) surge protection
LED the ability of resistance to surge is relatively poor, especially the resistance to reverse voltage ability. Strengthen the protection is also very important. Some 200W led flood lights installed in outdoor, such as the LED street lamp. Due to the power grid load shedding and lightning induction, from the power grid system into all kinds of surge, some surge will lead to the damage of LED. So analysis "zhongke hui treasure" drive power in surge protection should have certain lack, and as for the power supply and lamps and lanterns frequent replacement, LED drive power to suppress surge of intrusion, protect the LED not damaged ability.
(6) protection function
Power supply in addition to the conventional protection function outside, had better be in constant current output increase in LED temperature negative feedback, prevent LED temperature is too high; To conform to the safety and emc requirements.
3, according to the driving mode classification

(1) constant flow
A constant current drive circuit output current is constant, and the output of the dc voltage is along with the load resistance of different size in a certain range change, load resistance is small, the output voltage is low, the greater the load resistance, the output voltage is higher.
B constant current circuit are not afraid of load short circuit, but it is strictly prohibited to load completely open.
C constant current drive circuit drive LED is ideal, but relatively high prices.
D should pay attention to use bearable current and voltage value, it limits the number of the use of LED.
(2) voltage type

A when voltage regulator circuit parameters of the later, the output voltage is fixed, and the output current is along with the load increase and decrease and change;

B voltage regulator circuit are not afraid of open load, but it is strictly prohibited to load completely short circuit.
C to stabilized voltage driving circuit drive LED, each string need to add appropriate resistance can make each string LED display brightness average;
D brightness will be rectified the voltage changes.
4, integral constant current and constant current mode by road advantages and disadvantages
From the above contrast can also see that way by constant current although shortcomings more, the cost is high. But it can really play a role in protecting LED and prolong the service life of LED, so by road constant current is the trend of the future.
5, LED the power shortage
LED power supply is also a supporting products, currently on the market power quality is uneven, according to the existing data query and project execution meet bad light problem about analysis of the LED drive power supply at present the causes of deficiency of:
A production 200W led Flood light and related products company technical staff to switch power supply understanding is not enough, make power can be normal work, but some critical evaluation and electromagnetic compatibility consideration is not enough, there are still have to hidden trouble.
B most LED power production enterprises from ordinary switch power transformation to do LED power supply, LED to the characteristics and use of knowledge is not enough.
C at present about the standard of LED almost no, most of them are reference switching power supplies and electronic rectifier standard.
D now most LED power no unified, so most of the quantity is small. Purchase quantity is small, the price is on the high side, and components supplier don't fit.
E LED power stability: wide voltage input, high temperature and low temperature, thermal, over voltage protection without problems to solve them.
F is first drive circuit whole life, especially the key devices such as: capacity at high temperature life directly affects the life of the power supply.
G is LED driver should challenge higher conversion efficiency, especially in the high power LED driver is so, because all not as light output power as heat dissipation, power conversion efficiency is too low, the impact of the LED energy saving effect of the play.
H is currently in power smaller (1-5 w) applications, constant current drive power cost the proportion is close to one-third, are close to the cost of the light source, to a certain extent, affected the market promotion.