LED filament

from Wikipedia, the free encyclopedia

LED filaments ( English LED filaments ) are rod-shaped light leading electronic components, consisting of a transparent carrier (substrate), mounted thereon, light-emitting diodes (LED) and a fluorescent layer.

A 230 volt LED filament lamp with an E27 lamp base . The eight filaments can be seen as yellow lines.

A LED filament lamp ( English LED filament light bulb ) is a LED light source , wherein the LED such filaments a similarly in a glass flask bulb are housed.

history

LED filaments were patented by Ushio Denki and Sanyo in 2008. In 2013, Panasonic patented a structure of LED semiconductors on a glass strip, mounted horizontally, at the same height as the filament of a classic light bulb. In the same year, Nan Ya Photonics Inc applied for a circular arrangement of SMD LEDs at the level of the filament in the glass bulb of a lamp, but did not pursue this any further. Independently of this, a patent application was filed in the USA in 2014 by the Chinese company Shenzhen Runlite Technology , but not granted. Nevertheless, this structure has been marketed worldwide since then, as individual filaments or complete, ready-to-use lamps in which the filament is installed vertically or at an angle. Filaments installed at an angle correspond to the patent by Ushio Denki and Sanyo , which was granted in 2012. There are now lamps with longer and coiled filaments.

LED filament

construction

Operating an LED filament with approx. 5% of the nominal current shows the individual LED chips under the yellow fluorescent layer
  • Fluorescent layer
  • Substrate glass / sapphire crystal
  • LED chip
  • Connecting wires

    • LED filaments consist of a narrow strip of transparent substrate such as sapphire glass , onto which blue and sometimes additional red LEDs with a chip-on-board technology (COB) adapted to them are directly applied, ie without a chip housing . The individual LED chips are connected in series , with an electrical contact at each end of the strips. In order to generate a broad spectrum of light, the strips are additionally coated on both sides with a fluorescent layer. Their active ingredient is usually powder made from cerium- doped yttrium aluminum garnet (YAG: Ce 3+ ); the yellowish overall appearance of the LED filaments comes from it.

    properties

    The typical dimensions of LED filaments available in 2015 are 38.5 mm × 2.0 mm. They are between 26 and 67 mm. The typical number of LEDs per 38 mm filament is 28. The number and properties of the individual LEDs connected in series are used in data sheets. The operating voltage of a single LED filament is approximately 60 to 80 V, which depends on the number and type of LEDs. They have a specified operating current to be limited . This is typically around 10 mA. In the models available in 2015, a filament consumes around 1  W of power and emits around 100  lm , which was optimized in 2018 to up to 160 lm / W. In the models currently available, the color temperature of the filament is determined by the ratio of blue and red LEDs that are built into the filament, as well as by the composition and density of the fluorescent layer. In contrast to conventional LEDs on an opaque substrate, LED filaments have a radiation characteristic similar to that of a classic incandescent filament, i.e. they radiate almost omnidirectionally, with two opposite darker zones being formed on the sides of the substrate.

    Due to the arrangement of the LED threads and the transparent glass bulb, these lamps look largely like classic incandescent lamps. An elongated bulb shape that corresponds to early incandescent lamps is also marketed under the name "Rustika". Therefore, these lamps are well suited for use in antique lights, for example from the Art Nouveau period. As their dimensions are almost identical to classic incandescent lamps, they can also be screwed into lights with narrow glass shades.

    LED filament lamp

    Structure and appearance

    LED filament     lamp in the shape and appearance of a historical carbon filament lamp

    LED filament lamps largely consist of the same components as classic incandescent lamps with carbon filament or tungsten filament. These are:

    • the lamp base, whose metallic parts of the outer skin represent the electrical contacts
    • the glass lamp base with a gas-tight implementation of the power supply to the actual luminous component, in this case an arrangement of LED filaments
    • an inert gas with high thermal diffusivity
    • the glass outer bulb

    In addition, LED filament lamps contain a small power supply unit , typically built into the lamp base , which converts the AC voltage of the power supply system to the DC voltage required to operate the light-emitting diodes.

    Due to the length and alignment of the LED filaments, the appearance of LED filament lamps when switched on is more reminiscent of a carbon filament lamp than an incandescent lamp with a tungsten filament.

    The design of a lamp described here was also patented in 2014.

    Product evolution and interaction of the components

    The first LED-filament lamp was in 2008 by the Japanese manufacturer Ushio Lighting, Inc. brought to market. However, this model was not very successful because it still had some problems. It was still based on a single, large chip matrix that - like a tungsten filament - was positioned horizontally over the base. The individual LED chips in the lamps became very hot, which made a dedicated heat sink necessary. This meant that the lamp only had a radiation angle of 180 °.

    In order to come close to an omnidirectional light emission, a heat sink in the classic sense has to be dispensed with. Today's LED lamps with LED filaments therefore give off all of their heat to the envelope via the surrounding filler gas (helium). This is made possible by a low operating current and thus lower power per thread length. As with other LED lamps and incandescent lamps, a compromise must be found between service life and efficiency. This means that the total output is usually lower than that of the LED lamps that contain a heat sink.

    Banding in a photo of a glowing filament LED lamp that flickers at twice the mains frequency . With a short exposure time and the rolling shutter effect of the image sensor , the light flicker is shown as stripes.

    As a ballast is often capacitive power supply used. The difference between the rectified mains voltage and the total LED voltage is applied to the capacitor. Due to the relatively high operating voltage of the LED filaments, this is comparatively low; the cost-determining capacitor can be small and can be accommodated in the lamp base together with the additional components. Such LED lamps are not always dimmable. Inferior versions do without a sufficiently dimensioned electrolytic capacitor for voltage smoothing and therefore flicker at 100 Hz, twice the mains frequency . Better lamps contain more complex electronics and are often also dimmable (see also LED lamps ).

    lifespan

    The decisive factor for the service life of LEDs is the operating temperature. LED lamps with a higher power consumption (e.g. 8 W) therefore have a higher luminous flux, but often a higher temperature and thus a potentially shorter service life than a lamp of the same size with a lower power consumption (e.g. 5 W).

    Often the information on the service life cannot be compared between different manufacturers because the selection of criteria has not yet been standardized. For example, one manufacturer assumes a decrease in luminous flux to 70% as a criterion for the end of service life, while another assumes 50%. Various failure rates are also used as a basis.

    Sometimes an ambient temperature of a maximum of 35 ° C is specified, but the typical service life is related to the 25 ° C ambient temperature of the lamp, which is unrealistic for many luminaires because of the obstructed convection. The values ​​are therefore idealized and cannot be reproduced by the consumer.

    In the coming years, however, significant standardization by the market and the legislature can be expected, similar to what happened when converting the luminous flux to classic incandescent lamps ("... corresponds to 60 W") in the course of the incandescent lamp ban.

    The operation of LED filament lamps with a capacitor power supply leads to premature failure

    • on dimmers,
    • together with badly suppressed devices, as well
    • with non-sinusoidal current, e.g. B. from network simulations such as uninterruptible power supplies ( UPS ).

    The higher-frequency interference current and non-sinusoidal current are conducted via the capacitor through the LEDs and lead to unspecified overcurrent.

    Energy efficiency

    The typical data mentioned above (1 W provides around 100 lm) directly result in a light output of 100 lm / W; current models can achieve values ​​of around 150 lm / W. Light sources with such a luminous efficacy are classified in one of the two highest energy efficiency classes A + and A ++.

    The luminous efficacy is reduced by the high ambient temperature, as is the service life, which is characterized by a decrease in luminous flux (degradation) to 50 or 70%, for example.

    Quality features of LED filament lamps

    • Dimmability: not available in many inexpensive models
    • Flicker: typical 100 Hz flicker can be avoided with additional effort
    • Radio interference: occurs with switching power supplies ; Compliance with EMC limit values ​​is often questionable
    • Power factor :. Cos phi type about 0.5 leads to more effective current uptake
    • Interfering noises: can arise in switching power supplies
    • Color rendering index : Ra values ​​of over 90 can be achieved
    • Luminous efficacy: to be assessed together with the service life and the conditions of use

    Other features are the design and the quality of workmanship. Many of the features or their correct information on the packaging can only be determined in the measuring laboratory or not at all. There is also product piracy . Most of the lamps (also from European suppliers) come from Asia, where the most important patent rights are also located.

    Comparison with other light sources

    spectrum

    LED filament lamps, like other LED lamps, contain blue and sometimes red LEDs (the latter for a higher color rendering index and a warmer color temperature). These are covered with a fluorescent layer that fills the missing central part of the light spectrum. In contrast to compact fluorescent lamps, the spectrum is relatively continuous and does not have any extremely prominent peaks in individual colors.

    • Spectrum of a fluorescent lamp

    • Spectrum of a red, green, blue and white light emitting diode

    Luminous flux and power

    Due to the relatively high efficiency of the LEDs used in the meantime (as of December 2015), a luminous flux can be generated with the relatively low total power of around 5 to 8 W (1000 lm at 8 W), which can be achieved with small to medium power from incandescent lamps (up to 75 W) or halogen lamps (brighter than 42 W) are comparable. As of the end of 2015, higher luminous flux with correspondingly higher power consumption are reserved for LED lamps with a dedicated heat sink; However, due to their design - unlike classic incandescent or LED lamps - these usually only emit their light slightly in the direction of the base, which can be a problem in some luminaires.

    Examples of designs

    • Decorative candle lamp with E14 base

    • Pear shape with B22 base

    Web links

    Commons : LED filament lamps  - collection of images, videos and audio files

    Individual evidence

    1. ↑ a b https://patents.google.com/patent/US20090184618A1
    2. ↑ Nobuyoshi Takeuchi, Tsugihiro Matsuda, Hideo Nagai, Masahiro Miki, Takaari Uemoto: Light bulb shaped lamp and lighting apparatus . 2014. Retrieved September 26, 2017.
    3. ↑ Bor-jen Wu: LED LIGHT BULB (abandoned) . US patent office. Retrieved January 4, 2015.
    4. ↑ Yunglong Feng: LED LIGHT AND FILAMENT THEREOF (abandoned) . US patent office. Retrieved January 4, 2015.
    5. ↑ Yunglong Feng: LED LIGHT AND FILAMENT THEREOF . US patent office. Retrieved January 4, 2015.
    6. ^ Novel LED packaging adds filaments to retro bulbs - Designing with LEDs . In: Designing with LEDs . June 25, 2014 ( designingwithleds.com [accessed May 24, 2018]).
    7. ↑ http://www.runlite.cn/en/product-default-358.html
    8. ↑ a b http://www.runlite.cn/en/product-detail-129.html
    9. ↑ LED Filament Bulbs. Retrieved May 24, 2018 .
    10. ↑ a b http://www.runlite.cn/userfiles/5cjerp755q19k1413258994.pdf
    11. ↑ http://yuanleicom.hkhost1.baten.cc/userfiles/file/20160901/20160901084246_29396.pdf
    12. ↑ How do filament LED bulbs work, looking very similar to incandescent bulbs? Retrieved May 24, 2018 .
    13. ↑ Bor-jen Wu: LED LIGHT BULB . US patent office. Retrieved January 4, 2015.
    14. ↑ Figure
    15. ↑ The Next Generation of LED Filament Bulbs - LEDinside. Retrieved May 24, 2018 .
    16. ↑ https://www.led.de/led-filaments-led-lampen-der-naechsten-generation-im-gluehwendel-design
    17. ↑ LED lamps with special features: filament LED (filament) / dimmable. In: Price comparison. heise online, November 27, 2017, accessed on November 27, 2017 .
    18. ↑ Measurement protocol Osram AB39006. (PDF) Sample measured values ​​for a 6 watt filament LED lamp. fastvoice.net, accessed November 29, 2016 .
    19. ↑ Wolfgang Messer: LED filament lamps - a feast for lawyers. February 16, 2016, accessed November 29, 2016 .
    20. ↑ In the test: Dimmable vosLED filament lamp - efficiency miracle with quirks - Fastvoice blog . In: Fastvoice blog . July 19, 2014 ( fastvoice.net [accessed May 24, 2018]).
    21. ↑ LEDCAT LED E27 bulb lamps. Retrieved May 24, 2018 .