First, what is LED power? It can convert the power supply into a specific voltage current to drive the voltage converter of LED luminescence. Normally, the input of LED driving power includes high voltage power frequency ac (i.e., municipal power), low voltage dc, high voltage dc, low voltage high frequency ac (e.g., output of electronic transformer), etc. The output of LED drive power is mostly a constant current source which can change the voltage with the change of forward voltage drop of LED.
The core components of LED power supply include switch controller, inductor, switch component (MOSfet), feedback resistance, input filter, output filter and so on. According to the requirements of different occasions, there must be input overvoltage protection circuit, input undervoltage protection circuit, LED open circuit protection, overcurrent protection and other circuits.
Sort by drive
(1) the constant flow
The output current of the constant-current drive circuit is constant, while the output dc voltage varies within a certain range with the magnitude of the load resistance. The load resistance value is small, the output voltage is low, and the higher the load resistance value is, the higher the output voltage is.
Constant current circuit is not afraid of short circuit load, but it is strictly prohibited to open the load completely.
Constant current drive circuit driving LED is ideal, but relatively high price;
Note that the maximum current and voltage values used limit the number of leds used.
(2) voltage type
When the parameters of the voltage stabilizing circuit are determined, the output voltage is fixed, but the output current changes with the increase or decrease of the load.
The stable voltage circuit is not afraid of load opening, but it is strictly prohibited to short-circuit the load completely.
The LED is driven by a stable voltage drive circuit, and an appropriate resistance should be added to each string in order to average the brightness of each LED display.
The brightness is affected by the voltage change from the rectifier.
LED drive power features
(1) high reliability
Especially like the driving power of LED street lamp, it is installed at high altitude, which is inconvenient to maintain and expensive to maintain.
(2) high efficiency
LED is an energy saving product, and the driving power is more efficient. It is very important for the nodal heat dissipation of the power source installed in the lamp. The efficiency of power supply is high, its consume loss power is small, the heat that generates inside lamps and lanterns is small, also reduced the temperature rise of lamps and lanterns. It is beneficial to delay the LED's optical fading.
(3) high power factor
Power factor is the load requirement of power grid. Generally under 70 watts of household appliances, no mandatory indicators. Although the power factor of a single appliance with low power has little influence on the power grid, the light used at night is large and similar loads are too concentrated, which will cause serious pollution to the power grid. For the 30 - to 40-watt LED power supply, it is said that in the near future, there may be some requirements on the power factor.
(4) drive mode
There are two kinds of current passageways: one is a constant voltage source for multiple constant current sources, and each constant current source separately supplies each LED. This way, flexible combination, all the way LED failure, does not affect other LED work, but the cost will be slightly higher. The other is direct constant current power supply, which is the driving mode adopted by zhongke huibao instead, LED running in series or in parallel. It has the advantage of lower cost, but less flexibility, and it has to solve some LED failures, without affecting other LED operations. These two forms coexist for a time. Multi-channel constant current output power supply mode, in terms of cost and performance will be better. Maybe the mainstream of the future.
(5) surge protection
The ability of LED to resist surge is poor, especially the ability to resist reverse voltage. It is also important to strengthen protection in this regard. Some LED lights are installed outdoors, such as LED street lamps. As a result of the load of the power grid and the induction of lightning strikes, from the power grid system will invade all kinds of surges, some of which will lead to LED damage. Therefore, the driving power of "zhongke huibao" should be deficient in surge protection. As for the frequent replacement of power source and lamps, the LED driving power should have the ability to suppress surge intrusion and protect the LED from damage.
(6) protection function
Besides the conventional protection function, it is better to add negative feedback of LED temperature in constant current output to prevent LED temperature from being too high. To meet the requirements of safety and electromagnetic compatibility.
The advantages and disadvantages of integral constant current and route constant current working mode
Compared with the overall constant current, although the path constant current has many disadvantages, the cost is also high. However, it can really protect LED and prolong the life of LED, so it is the future trend of constant flow by road.