LED drive power classification methods do you know how much?
The input of LED drive power supply includes high voltage power frequency switching (i.e., power supply), low voltage direct current, high voltage direct current, low voltage high frequency switching (for example, the output of the electronic transformer). While the output of the LED drive power supply is most of the constant current source that can change with the forward voltage drop of LED.
LED supply focus elements include switch controller, inductor, switch components (MOSfet), feedback resistance, input filter, output filter, etc.. According to the requirements of different places, but also have input over-voltage protection circuit, input under voltage protection circuit, LED open circuit protection, over current protection circuit.
Classification by driving method
Constant current type
Constant current driving circuit output current is constant, while the output DC voltage is as the load resistance of different sizes of change in a certain range, load resistance is small, the output voltage is low, the greater the load resistance, the output voltage is higher;
Constant current circuit is not afraid of load short circuit, but it is strictly prohibited to load completely open circuit;
Constant current drive circuit LED is more ambitious, but relatively high cost;
The maximum value of the current and voltage, which is used to limit the amount of LED used.
When the voltage regulator circuit parameters are determined, the output voltage is strong, and the output of the current with the load change and change;
Voltage regulator circuit is not afraid of load open circuit, but the load is strictly prohibited;
In order to drive the LED driver circuit, each string must be coupled with the resistance of the resistance can make each string LED performance uniformity;
Brightness will be affected by the voltage change rectifier.
Characteristics of LED drive power supply
Particularly like the LED street lamp driver power supply, installed in the high altitude, maintenance is not convenient, the cost of maintenance is also large.
LED is the product of energy saving, the drive power supply is subject to high. To deal with power placement in the lamp inside the junction heat dissipation is very tight. The power supply is subject to high, the power consumption is small, and the heat quantity is small, and the temperature rise of the lamp is reduced. Favorable to delay the LED attenuation.
High power factor
Power factor is the requirement of power grid to load. Usually less than 70 watts of home appliances, there is no force index. Although power is not a single power factor of low power grid has little impact on the power grid, but the use of large lighting at night, the same load is too high, will be a serious pollution of the power grid. Against 30 watts ~40 watts LED driver power, I heard that in the near future, it will probably have a positive indicator of the power factor requirements.
Today, there are two unobstructed: one is a constant pressure source for multiple constant current source, each constant current source to each road LED alone. This approach, combined maneuver, together with LED hinders, does not affect other LED things, but the cost will be slightly higher. The other is direct constant current power supply is also "in the Branch Hui Bao" to accept the driving method, LED series or parallel operation. It's advantage is low cost, but mobility is poor, but also to handle a LED hinder, do not affect other LED running the subject. These two kinds of circumstances, in a period of time. Multi way constant current output power supply method, in terms of cost and performance will be better. Probably because of the mainstream bias in the future.
LED is a relatively poor ability of anti surge, especially the anti reverse voltage power. To enhance the protection of this area is also very tense. Some LED lights are installed outdoors, such as LED street lamps. Due to the load of the power grid and lightning surge, from the grid system will invade all kinds of surge, some surge will lead to the destruction of LED. Therefore analysis ", Bao Hui" driving power in surge protection should shortage is sure, and for frequent replacement power supply and lighting, the LED driving power supply to the invasion of the restraint of the surge, cover the LED is not destroyed ability.
Power in addition to the groovy protection function, most fortunately, constant current output growth led temperature negative feedback, preparedness LED temperature is too high, to comply with the safety and electromagnetic compatibility requirements.
The advantages and disadvantages of the group constant current and constant current method
With the constant current group compared by the constant current is more than the cost disadvantage, high. But it can really play a cover LED and extend the life of LED, in order to be constant current is the trend of the future.