How much do you know about the classification of LED drive power?

By TENCO in 2019-07-09 17:03

First, let's talk about what is LED drive power?It can convert the power supply to a specific voltage and current to drive the LED LED light voltage converter, generally: LED drive power supply input including high voltage power frequency ac (that is, mains), low voltage dc, high voltage dc, low voltage high frequency ac (such as the output of electronic transformer) and so on.The output of LED drive power is mostly a constant current source that can change the voltage with the change of LED forward voltage drop value.

LED power core components include switch controller, inductor, switch components (MOSfet), feedback resistance, input filter, output filter and so on.According to the requirements of different occasions, but also the input overvoltage protection circuit, input undervoltage protection circuit, LED open circuit protection, overcurrent protection circuit.

By driving mode

(1) the constant flow

The output current of constant current drive circuit is constant, while the output dc voltage varies within a certain range with the difference of load resistance value. If the load resistance value is small, the output voltage will be low, and the larger the load resistance value, the higher the output voltage will be.

Constant current circuit is not afraid of load short circuit, but it is forbidden to load completely open;

Constant current drive circuit drive LED is ideal, but relatively high price;

Note the maximum current and voltage values used, which limit the number of leds used.

(2) voltage type

When the parameters in the voltage regulator circuit are determined, the output voltage is fixed, while the output current changes with the increase or decrease of the load.

Voltage regulator circuit is not afraid of open load, but strictly prohibit the load completely short circuit;

LED is driven by voltage stabilizing drive circuit, and each string needs to be added with appropriate resistance to make each string of LED display brightness average;

The brightness will be affected by the voltage change from rectification.

LED drive power features

(1) high reliability

Especially like the drive power of LED street lamp, which is installed in the high altitude, the maintenance is not convenient, and the maintenance cost is also large.

(2) high efficiency

LED is energy saving products, the efficiency of driving power to high.It is very important to heat the knot inside the lamp.The efficiency of the power supply is high, its consumption power is small, the heat in the lamp is small, also reduced the temperature rise of the lamp.It is beneficial to delay LED light decay.

(3) high power factor

Power factor is the requirement of power grid to load.Generally, there is no mandatory index for household appliances under 70 watts.Although the power factor of a single appliance with small power is a little lower, it has little impact on the power grid, but at night, the use of lighting is large, the same load is too concentrated, will produce serious pollution to the power grid.For the 30-40 watt LED drive power supply, it is said that in the near future, there may be certain power factor requirements.

(4) driving mode

There are two kinds of current: one is a constant voltage source to supply multiple constant current sources, and each constant current source alone provides power to each LED.In this way, the combination is flexible, and the LED failure will not affect the work of other leds, but the cost will be slightly higher.The other is direct constant current power supply, that is, "zhongke huibao" to adopt the drive mode, LED series or parallel operation.Its advantage is low cost, but poor flexibility, but also to solve one LED fault, does not affect the operation of other LED problems.These two forms coexist for a period of time.Multi-channel constant current output power supply mode, in terms of cost and performance will be better.Maybe it's going to be the mainstream.

(5) surge protection

LED anti - surge ability is relatively poor, especially anti - reverse voltage ability.Strengthening protection in this area is also important.Some LED lights are installed outdoors, such as LED street lamps.Due to the swing of power grid load and the induction of lightning strike, various surges will be invaded from the power grid system, and some surges will lead to the damage of LED.Therefore, the analysis of "zhongke huibao" drive power supply should have a certain lack of surge protection, and as for frequent replacement of power supply and lamps, LED drive power supply should have the ability to inhibit the invasion of surge and protect LED from being damaged.

(6) protection function

In addition to the conventional power 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 the integral constant current mode and the by-pass constant current mode

Compared with the overall constant current, constant current by route has more disadvantages and higher cost.However, it can really protect LED and extend the life of LED, so constant current is the future trend.