So far, the "light engine" has not yet had a very strict and precise definition, so many readers still don't know what the light engine is. Some people define it as "a 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 conventional connector that matches the LED luminaire is directly connected to the branch circuit. The LED luminaire is designed not to use a standard lamp holder." This definition seems to be complete, but it is often 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.
Some people call the COB LED a light engine, which is obviously wrong! Because it does not have a constant current drive source, there is no "drive", how can it be called "engine"?
The types of power sources can be divided into two categories: DC light engine and AC light engine. However, due to the large number of light engines currently used in indoor lighting, we are paying more attention to the light engine of AC power.
So is the entire LED luminaire also called a light engine? Of course not. Just as the whole car can't be called an engine, the engine is the powertrain of the car, but it doesn't equal the car, and it needs to be added to the car to become a car. Products such as light engines are needed because all lamps have a variety of appearances. Some fixtures can even be called artwork. Take the incandescent lamp, it can be said that it has only one form of the simplest light bulb, at most plus a candle light or a tiny Christmas light. However, its shape can be varied. In particular, the crystal lamp is a variety of arts and crafts, extremely gorgeous. But the LED must also be equipped with an extremely complex constant current drive source to work as an incandescent lamp (it can be illuminated by connecting 220V). 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). This on the one hand contributes to standardization and on the other hand greatly facilitates the design of the enclosure (and radiator) designers.
First, the benefits of using a light engine
Many people believe that the main purpose of promoting light engines is to standardize to increase their interchangeability. In fact, this standardization should not only start with the light engine, but should start with the interface between the unified heat sink and the light engine. 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. Even with such specific problems, there are still many difficulties. Because it is related to the wattage and the heat dissipation capability of the heat sink. Therefore, the promotion of the light engine can not only focus on the benefits of interchangeability.
It can be said that the biggest benefits of promoting the light engine are as follows.
1. Reduce the R&D expenses of LED lighting manufacturers and shorten the 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.
2. Promotion of 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.
3. Improve 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.
4. Reduced costs
At least the printed board of the constant current driving source can be omitted, and the production cost thereof.
For now, the simplest and most important is the light engine for LED bulbs. Let's take a look at the composition of this light engine.
Second, the light engine of the LED bulb
For a bulb, its composition is very close to standardization. It consists mainly of three major components: LED light source, constant current drive power supply, heat sink and housing (including lamp holder and lamp cover).
So if you take the LED bulb, 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.
1. Switching power supply is not suitable for 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. Someone has tried to do this, and the result is very crowded (see Figure 2).
As can be seen from this photo, 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 likely that there are five 1W LEDs in the picture. If you want to make a 9W or 10W bulb, it is completely impossible to achieve.
2. Linear power supply can reduce component count but is inefficient
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. This can be understood from the internal structure diagram and waveform diagram of this chip. Figure 3 is the internal structure of the CL8801 chip of Supertex Corporation of the United States.
Its current and voltage waveforms are shown in Figure 4. It can be seen from the figure that when the AC voltage rises to a certain value, the first switch is turned on, the first string of LEDs is turned on, and the first constant current source is selected; the first switch is continued to rise to a higher value. Disconnected, the second switch is turned on, the first string is turned on with the second string of LEDs at a second current source of higher current, and so on, the last string of on-time is the shortest, but the on-current is the largest. (The last constant current source). This results in a current waveform that is close to the voltage waveform (half sine wave), resulting in the highest power factor. But it also brings a series of shortcomings and problems (see later).
Below are several light engines that use a non-electrolytic linear constant current source.
These are the linear constant current source solutions of electroless capacitors. Daxin's DS6622 uses a bridge stack of varistors, three resistors and one capacitor and two ICs (DS6622). A total of eight components occupy only 10 The area around %. This light engine is a viable solution in terms of footprint. However, its disadvantage is that, like all common linear power supplies, according to the data given by ExClara, the efficiency is 84%-93% when the input mains voltage changes by +/-10%. Moreover, only the mains voltage variation is allowed to be less than 20% and the LED voltage must be within 10% of the design value, otherwise the efficiency will become very low. The power efficiency of the SU1203 is shown in Figure 6.
As can be seen from the figure, the efficiency is about 96% at an input voltage of 200V, and about 80% at an input voltage of 245V. The average is about 88%, which is equivalent to the efficiency at 220V. If the efficiency is 100% at 190V (impossible!), the efficiency at 260V is 70%, then the average is 85%. To sum up, the shortcomings and problems of this electroless capacitor solution are as follows:
1. Inefficient, about 88%.
2. The LED is not a DC drive, but it is switched on and off, so the LED utilization is low, and the high pulse current of the last string of LEDs will also affect its life.
3. The overall luminous efficiency is about 15% lower than that of electrolytic capacitors.
4. 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.