LED 相關知識
What is an LED?
A Light Emitting Diode is a semi-conductive material that produced light via Electroluminescence. This is an optical and electrical phenomenon in which light is emitted from a material when an electrical current or strong electrical field is passed through it.
The invention and development of the high-power white-light LED used in luminaires is rapidly replacing incandescent and fluorescent lighting. The development of LED technology has caused their efficiency and light output to rise exponentially, with a doubling occurring approximately every 36 months since the 1960s.
Advantages of LED?
1.LOW RUNNING COSTS
LEDs are far more efficient at converting electricity into light than alternative light sources. In LEDs, typically 80% – 90% of the electricity is converted into light whereas traditional incandescent lamps only turn around 50% of their electricity into light.
This means you use less power to achieve the same amount of light.
2.LONG LIFE
Almost all LED luminaire manufacturers quote a life of 50,000 hours for an LED, but they will also normally show L80 after that figure.This relates to the life, so L80 means that at 50,000 hours, you will still have 80% of the light from the LED that you have on day one.
At 12 hours a day 365 days a year, the LED would last around 11.5 years.
To put this in context, a now outlawed Tungsten Candle lamp would give 1000 hour life, a low voltage lamp would typically give 5000 hour life, a Metal halide discharge lamp would give 12,000 hour life and a T5 Fluorescent up to around 20000 hour life.
3.NO HEAT OR UV LIGHT
Incandescent uses 50% of its energy in the infrared/heat range which can’t be seen by the eye. In LED’s, 100% of the light produced is within our eyesight range of 400-700nm.
4.EARTH FRIENDLY
Unlike fluorescent lights that can contain a lot of different chemicals including mercury, LEDs are free of toxic chemicals and are 100% recyclable.
5.INSTANT LIGHT
Unlike other lamps such as compact fluorescent which take time to warm up to full brightness, LEDs are 100% instantaneous. This makes them perfect for use with switch types such as PIR and occupancy sensors.
6.FLEXIBLE
• Available in different colour temperatures – extremely warm white to daylight (2400k-6000k)
• Available in different sizes.
• Robust – if you drop one it will still work afterwards.
• Work well in different temperatures
• Fully dimmable
RGB LED
White light can be formed by mixing differently coloured lights; the most common method is to use red, green, and blue (RGB). Hence the method is called multi-colour white LEDs often referred to as RGB.
Solid-state devices such as LEDs are subject to very limited wear and tear if operated at low currents and at low temperatures. Typical lifetimes quoted are 50,000 to 100,000 hours, but heat and current settings can extend or shorten this time significantly. LED performance is temperature dependent as LED light output rises at lower temperatures, levelling off, depending on type, at around -30°C.
S.M.D – Surface Mounted Device
SMD are a newer generation of chips that can be soldered directly onto a printed circuit board therefore requiring less space between them. SMD Chips are usually followed by a number that denotes its size. 35:28 for example meaning a size of 35mm x 28mm. The benefits of this chip are; Low voltage requirements and little generated heat. You’d typically find these on LED Strips, LED retrofit lamps and RGB digital tapes.
C.O.B – Chip On Board
COB are the most recent development in chip technology. They are made from multiple diodes (usually more than 9) packaged together on a substrate by epoxy resin or other material and a yellow phosphor covers them over. The result is that when lit, it looks like a single module. The benefits of this type of arrangement are; greater lumen to watt ratio, 30% cheaper build cost, high CRI, high power and intensity. Typical uses are Down Lights, Street Lights and Flood Lights.