Analysis of Advantages and Disadvantages of Electroless Capacitor LED Light Engine

An LED light engine is an integral combination of LED packages (components) or LED arrays (modules), LED drivers, and other brightness, thermal, mechanical, and electrical components. The device is connected directly to the branch circuit through a conventional connector that matches the LED luminaire, which is designed to not use a standard lamp holder. This definition seems to be complete, but it tends to be confusing because it also includes other brightness, thermal, mechanical, and electrical components.

In fact, it is very simple to define the light engine: that is, the combination of the LED light source and the LED driving power supply into one module can be called the light engine. More generally, it can be said that any constant current drive source is placed on the LED aluminum substrate to become a light engine. And if the LED is made into a light engine, it will be brighter when it is connected to 220V like an incandescent lamp (of course, it needs a matching radiator).

First, the advantages of LED light engine analysis

In the case of an LED bulb, the size of the light engine and the heat sink is basically the same, and specifically relates to the size position of the positioning screw hole and the positioning screw hole of the heat sink. The advantages of using a light engine are mainly reflected in the following aspects:

(1) LED light engine can greatly accelerate the promotion of LED lamps

In recent years, with the ban on incandescent lamps, LED lamps are about to explode. LED lighting factories have sprung up like mushrooms. Although this is an inevitable trend, it also brings a lot of problems, especially the performance of LED lamps and the disorderly price war between various manufacturers. The emergence of LED light engines can solve such problems to a large extent. Because the quality is determined by several big manufacturers that produce light engines, the price is not likely to have much difference. This greatly reduces the internal friction caused by disorderly competition. Help the rapid development of the LED lighting industry.

(2) LED light engine improves the overall performance of LED lamps

For example, the overall light efficiency (lm/W) is increased, here is the overall light efficiency including power efficiency, of course, the whole lamp should also include the light transmittance of the lampshade (but this is not the company that produces the light engine). Responsible, but responsible for the company that produces the radiator). It can also increase the color temperature, color rendering index and other indicators.

(3) LED light engine shortens product production cycle

Because the optical and electrical specifications of all LED luminaires are set by the light engine manufacturer. Even the corresponding heat sink is recommended. Lamp manufacturers only need to install the light engine inside the radiator. Lamp manufacturers do not even need experienced optical and electronics engineers, nor do they need to purchase expensive optical and electronic equipment. In other words, the light engine can greatly reduce the entry limit of the LED lighting factory, but it will not reduce the quality of the LED lighting. Of course, this requires the manufacturer of the light engine to have a very high level.

(4) LED light engine reduces costs

For now, the simplest and most important is the light engine for LED bulbs. Since the light engine is used, at least the printed circuit board of the constant current driving source can be omitted, and the production cost thereof.

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Second, the analysis of the disadvantages of LED light engine

Also taking LED bulbs, if you want to make a light engine, you must combine its power board and LED board into one board. It can be seen that the difficulty is very big. The disadvantages of using a light engine are:

1) Switching power supply is not suitable for LED light engine

Although the switching power supply has better performance and higher efficiency, the biggest disadvantage is that the number of components is very large, and it is very difficult to integrate with the LED light board. Some people have tried to do this, and the result is very crowded.

As can be seen from the above figure, the entire switching power supply occupies almost 70% of the area, while minimizing the space of the LED. This structure is obviously not feasible because it not only reduces the light-emitting area of the LED, but also blocks part of the light. And the biggest problem is to reduce the heat dissipation area of the LED. It seems that there may be five 1W LEDs in the picture. It is completely impossible to make a 9W or 10W bulb.

2) Linear power supply can reduce component count but low efficiency

In order to reduce the number of components, the easiest way is to use a linear power supply. Usually, the linear power supply has only 5-6 components, which can greatly reduce the occupied area. At present, most of the light engines on the market are linear constant current sources using electroless capacitors. The electroless capacitor solution was proposed by ExClara in the United States in August 2011. Later, 6-7 companies imitated their ideas. A similar chip. Its basic principle is to connect LED strings driven with different constant current values when inputting different values of the AC voltage waveform to obtain a current waveform matching the half sinusoidal waveform after AC rectification, so that power close to 1 can be obtained. Factor. Inefficiency is also reflected in the following points.

Inefficient, about 88%.

The LED is not a DC drive, but is time-interrupted, so the LED utilization is low, and the high pulse current of the last string of LEDs also affects its lifetime.

The overall luminous efficiency is about 15% lower than that of electrolytic capacitors.

The current waveform is close to half a sine wave, so there will be 100Hz flicker. Cannot be used in digital camera photography and security systems.

3) The combination of power supply and light board will cause serious heat dissipation problems.

Is it a viable LED light engine solution to use a normal linear constant current source? Not the case. Although it solves the problem of occupying space, in addition to the disadvantages already mentioned above, there is a drawback that cannot be ignored, that is, the heat dissipation problem. Although no matter where the power is placed, its heat is always dissipated into the space through the heat sink, but when the power supply and the light board are put together, the power consumed by the power supply becomes heat and is directly applied to the light board. It will increase the amount of heat that the lamp board needs to dissipate, which will increase the junction temperature of the LED and reduce its life. Moreover, the biggest disadvantage of linear constant current sources is their extremely low efficiency. So this is an extremely serious problem.

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