An inside view: are Filament lamps good for you?

We welcome fans of LED-lamps on the pages of the blog Prestigio!

Today we will talk about one burning and extremely popular recently topic, namely filament (or, in Russian, threadlike) LED lamps. On Geektimes many articles are devoted to them ( 1 , 2 , 3 ), however they do not affect the analysis of lamps and the comparison of their temperature characteristics. Therefore, especially for you, dear readers, we conducted a detailed analysis of lamps from different manufacturers, including the measurement of the temperature of the LED filaments. And under the cut, we will try to answer the question: are the lamp filament as good as the marketers represent us?

Background question

When it comes to new technology, one of the most important questions immediately arises: how does this technology merge into the overall technological “eco-environment”? Usually, revolutionary technologies simply do not fit into the usual course of things, and huge efforts have to be made to introduce revolutionary products. For example, this was the case with renewable energy sources installed on private houses when the cost of the “kit” subsided by orders of magnitude , and in some places on our planet people also paid extra for electricity generation , which required a revision of the relationship between producers and consumers of electricity. A completely similar story happened with electric cars, when the industry split up and went in two ways: hybrids and full-fledged electric machines with separate “filling” stations.

5 years ago, LED lighting began to actively conquer his minions and adepts. Engineers have long tried to adapt two-dimensional from the nature of the light sources for three-dimensional illumination (which only cost lamps in the form of corn cobs ). This was written several times, both then and very recently .
')
And so, filament lamps were put on the market. It would seem that even the ideal solution was found, but the optimal solution to the problem, when “the sheep are full and the wolves are intact”: the light bulb is almost no different from the Ilyich light bulb both in form and in content, only the tungsten filament is replaced with the LED filament. Even the old glass-blowing plants and workshops found work . Now it is proposed to use a ceramic translucent substrate to improve the radial distribution of the luminous flux of the lamps (for example, Crystal Ceramic MCOB ).


However, despite the indisputable advantages over SMD LEDs, the filament of lamps has a number of problems that for some reason they don’t want to notice. For example, in the “standard” arrangement with SMD diodes, a rather massive aluminum substrate and body efficiently remove heat, whereas in the filaments the only way to remove heat is actually only convection and dissipation through the walls of the glass bulb. That is, a banal overheating gradually kills both the diodes themselves (the brightness decreases with temperature) and the phosphor (the CRI or R _a color rendering index and the CCT color temperature suffer). Yes, this method of "overheating" works for a tungsten lamp, because the gas in it partially contributes to the regeneration of the filament during use, but no more. More about overheating from a scientific point of view can be read here . As follows from the presented article, it is relatively harmless to consider temperatures of about 60-70 degrees.

In a nutshell, for an ordinary consumer, overheating or insufficient heat dissipation from LEDs means only one - multiple (sometimes by orders of magnitude) deterioration in the characteristics of LED lamps.

In order to confirm or disprove this point of view, it is necessary to stock up on lamps, take conventional LED lamps for comparison and experiment ... including temperature measurement, in which the 5th series Flir thermal imager with a 240 by 320 pixel matrix will help us. With this camera, the temperature was measured both on the flask for half an hour and on the LEDs themselves after the flask was removed.

By tradition, conclusions for those in a hurry are presented in two summary tables at the very end of the article . And lovers of thorough showdowns are welcome to the experimental part.

Part experimental

So, for the experiments, three lamps from different manufacturers were taken: a cheap Chinese Ebay bulb from CroLED (actually equivalent to Eglo at a price), another Eglo bulb from a local Leroy Merlin, and the highly respected and widely known Phillips. Yes, it is worth noting that perhaps the bulb with Ebay does NOT have anything to do with CroLED .

CroLED: Chinese Ebay Quality

Let's start with filament-lamp from the Middle Kingdom. The light bulb arrived from China in a simple cardboard box with a minimum of information on it (temperature, power and supply voltage. Honestly, the expectations were different, but the reality was much harsher. The ripple factor was 67% (!), I think this is a record ! In fact, the light went out and flared up again with a frequency of 10 ms. The color temperature differed to a lesser extent from what is indicated in the seller's shop on Ebay.


NB: All lamps presented in the article have a glass flask. And although it can withstand falling to the floor, be careful when handling them!

Analysis of the light bulb revealed one interesting feature of the design - namely, the driver. More precisely, its complete absence: the lamp is powered through a banal MB10F diode bridge with a pair of resistors and a huge solid-state capacitor. But compact!


The LEDs are located on a matte (!) Substrate in the amount of 18 pieces. Each LED chip is made of an asterisk sapphire textured substrate. Chips are completely small size - less than a human hair.


And what about the temperature? - the reader will ask. Yes, the temperature on the flask in 5-7 minutes reaches about 40 degrees and remains so for half an hour.

But now let's look under the flask of our lamp. After removing the glass and measuring the temperature, it turned out that the threads very quickly (literally within 1 minute) heat up to almost 90 degrees, and in some places, apparently, where the LEDs are located, the temperature reaches more than 100 degrees.

Eglo: ordinary bulbs with ordinary features

The next lamp from the company Eglo, which, by the way, has a representative office in the Russian Federation , is generally pleased with its characteristics. The pulsations at a frequency of 100 Hz were about 6%, while the color temperature and the CRI fully correspond to the declared characteristics.



Inside the lamp there are also four threads of LEDs, as in the Chinese lamp. Inside the driver is hidden on the basis of capacitor ballast. LEDs are slightly larger - 113 to 57 microns than in the previous case. However, they are extremely poorly fixed on the matte substrate again.


As for the temperature, the bulb quickly (for the same 5-7 minutes) warms up to a temperature of about 50 degrees. And the threads again show a temperature of ~ 90 degrees. Straight, like the curse of the design of the lamp "glowing" some!

Phillips: quality is paramount

Phillips last tested light bulb. Surprisingly, this E14 bulb demonstrates excellent compliance with the stated characteristics and the level of pulsations is extremely low.


What is the reason, because the base E14 is much smaller than the E27? - you will ask a question. Everything ingenious is simple: Phillips has good, very good engineers who are able to create an ultra-compact driver (flyback converter) so that it fits into the E14 cartridge, while the driver provides an extremely low ripple level (<1%).

In the lamp itself there are only two LED threads, as it consumes only 2.3 watts. LED chips are placed on a transparent substrate and are similar in size to those used in Eglo lamps, but with a different substrate texture - the “shield” . As already noted above, you will not trample against the laws of thermal physics.


In about 10 minutes, the lamp bulb warms up to ~ 45 degrees (two threads slowly “warm up” the entire lamp). However, the temperature of the filaments without a glass bulb is still 95 degrees, in some places - we repeat, most likely, at the place of mounting the LED chips to the substrate - reaching values ​​of 110-120 degrees.


In order not to be unfounded when passing a verdict on filament-lamps, we will add a few photos of the already familiar IKEA lamps and high-power Prestigio smart lamps, which we will talk about next time. The IKEA lamp body warms up to 75 degrees for half an hour, and the Prestigio smart lamp is up to 58. At the same time, the Prestigio SMD LEDs, for example, heat up to the maximum power of 60-70 degrees indicated at the very beginning of the article.

findings

Let us now summarize some results and try to answer the question: is the game worth the candle filament'ov?

1. By tradition, the test data is summarized in the table below. But, in my opinion, you should not trust the declared luminous flux of the Chinese lamp, and the other characteristics do not inspire confidence. Manufacturers of consumer goods have a habit of overstating results. The rest of the Eglo and Phillips lamps correspond to those stated on the package, and China - you understand perfectly well ...
   
   Please save your health and time - request test results before buying LED lamps on Ebay, and in regular stores you will also have to introduce this measure soon!
   
   
   
   
   
   
2. A comparison of the spectra did not reveal any significant differences: in all the lamps, most likely, the same phosphor is used, which gives a warm lamp filament-light. There are slight variations in the blue components, which can be traced to the color temperature above: Eglo is the warmest, Phillips is in the middle, CroLED is the “coldest”.
   
   
3. If we talk about some technology, then only Phillips has the right to be called a good and safe lamp with a normal driver, once again confirming the status of a leading player in the market.
   All tested lamps have surprisingly similar values ​​of specific luminous flux and power density. These values ​​are comparable to average SMD lamps . Apparently, the heat transfer and heating of LEDs significantly limit these characteristics in comparison with the usual layout based on SMD LED assemblies.
   
   
   
   
   
4. And the most delicious in store for dessert. Measuring the temperature of the filaments themselves with the help of an IR camera (thermal imager) - we hope - convincingly show and prove that the filament technology cannot be a complete replacement for conventional SMD lamps with an aluminum radiator and a much more efficient heat sink. Plus, we will add significantly limited space for the driver and as a result we will find that creating bright and powerful luminaires with a long service life based on filament will be problematic (already 12 W of the lamp is often equipped with a radiator ).
   

In the next article, we will continue poking around in the lamps and look under the skirt under the radiator Prestigio bulbs , including smart lamps, controlled via the BlueTooth protocol. We will see what's interesting there!

PS: In the past, a review and comparison of IKEA and Canyon lamps, user kenbik suggested testing lamps for electromagnetic interference using an FM radio receiver. The old receiver was not found, so the SBH-52 headset with a built-in FM receiver was used.


Reporting: Of the installed IKEA, Gauss, and Presigio smart bulbs, only the IKEA LED lamps are buzzing noticeably. And everything: that E27, that E14 and different in power. Gauss is practically silent, as well as Prestigio (do not forget, yet in modern devices there is effective noise reduction).

Stay tuned and subscribe to our blog ! It is not difficult for you - we are pleased!

---

A full list of published articles "Inside Look" on Habré and GT:

Opening the Nvidia 8600M GT chip , a more detailed article is given here: Modern chips - a view from the inside
An inside look: CD and HDD
An inside look: LED bulbs
An inside look: the LED industry in Russia
An inside look: Flash and RAM
An inside view: the world around us
Inside View: LCD and E-Ink Displays
An inside look: matrix digital cameras
An inside look: Plastic Logic
An inside look: RFID and other tags
An inside look: postgraduate study at EPFL. Part 1
An inside look: postgraduate study at EPFL. Part 2
An inside view: the world around us - 2
An inside view: the world around us - 3
View from the inside: the world around us - 4
An inside look: 13 LED lamps and a bottle of rum. Part 1
An inside look: 13 LED lamps and a bottle of rum. Part 2
An inside look: 13 LED lamps and a bottle of rum. Part 3
An inside look: IKEA LED strikes back
An inside view: are Filament lamps good for you?

and 3DNews:
Microview: a comparison of modern smartphones displays