There are several different types of diodes that are available for use in electronics design.
This type of diode conducts in the reverse direction when the reverse bias voltage exceeds the breakdown voltage. The LED is one of the most popular types of diodes which produces light when the diode permits the transfer of electric current between the electrodes. A Photodiode is used to detect light and feature wide, transparent junctions as it operates in reversed bias where small amounts of current flow. A Schottky diode is constructed from a metal-to-semiconductor contact and has a lower forward voltage drop than ordinary P-N junction diodes.
The tunnel diode is similar to a standard P-N junction except that the doping levels are high with narrow depletion region. These are used as voltage-controlled capacitors which feature a reverse bias that varies the width of the depletion as per the voltage across the diodes. This type of diode provides a stable reference voltage and can be made to conduct backwards. The past few decades have brought a continuing and rapidly evolving sequence of technological revolutions, particularly in the digital arena, which has dramatically changed many aspects of our daily lives.
The incandescent lamp is the best known of Thomas Edison's major inventions, and the only one to have persisted in use (and in nearly its original form) to the present day, now more than a century after its introduction. Although light emitting diodes are in operation all around us in videocassette recorders, clock radios, and microwave ovens, for example, their use has been limited mainly to display functions on electronic appliances.
The widespread utilization of diode devices for general lighting is still some years away, but LEDs are beginning to replace incandescent lamps in many applications.
Approximately 10 percent of the red traffic lights in the United States have now been replaced with LED-based lamps. As improvements have been made in manufacturing efficiency and toward the ability to produce light emitting diodes with virtually any output color, the primary focus of researchers and industry has become the white light diode.
Details of the fundamental processes underlying the function of light emitting diodes, and the materials utilized in their construction, are presented in the ensuing discussion.
The fundamental element of the LED is a semiconductor chip (similar to an integrated circuit), which is mounted in a reflector cup supported by a lead frame connected to two electrical wires, and then embedded in a solid epoxy lens (see Figure 1). The functional details of the light emitting diode are based on properties common to semiconductor materials, such as silicon, which have variable conduction characteristics. At progressively higher energy levels, proceeding outward from the nucleus, two distinct energy bands can be defined, which are termed the valence band and the conduction band (Figure 3). In conductors, the valence and conduction bands partially overlap in energy (see Figure 3), so that a portion of the valence electrons always resides in the conduction band. Semiconductors have band gaps that are small but finite, and at normal temperatures, thermal agitation is sufficient to move some electrons into the conduction band where they can contribute to electrical conduction. The element silicon is the simplest intrinsic semiconductor, and is often used as a model for describing the behavior of these materials. The process of doping to modify the electronic properties of semiconductors is most easily understood by considering the relatively simple silicon crystal structure.
Doping in order to produce the opposite type of material, having a negative overall charge character (n-type), is accomplished through the addition of Group V elements, such as phosphorus, which have an "extra" electron in their outermost energy level. Although silicon and germanium are commonly employed in semiconductor fabrication, neither material is suitable for light emitting diode construction because junctions employing these elements produce a significant amount of heat, but only a small quantity of infrared or visible light emission.
The fundamental key to manipulating properties of solid-state electronic devices is the nature of the p-n junction.
In a diode configuration, electrodes on opposite ends of the device enable a voltage to be applied in a manner that can overcome the effect of the depletion region. If the circuit polarity is reversed with respect to the p-type and n-type regions, electrons and holes will be pulled in opposite directions, with an accompanying widening of the depletion region at the junction.
Manipulation of the interaction between electrons and holes at the p-n junction is fundamental in the design of all semiconductor devices, and for light emitting diodes, the primary design goal is the efficient generation of light. The basic structure of a light emitting diode consists of the semiconductor material (commonly referred to as a die), a lead frame on which the die is placed, and the encapsulation epoxy surrounding the assembly (see Figure 1).
Although the color of light emitted from a semiconductor die is determined by the combination of chip materials, and the manner in which they are assembled, certain optical characteristics of the LED can be controlled by other variables in the chip packaging. For creation of diffused LED lenses, minute glass particles are embedded in the encapsulating epoxy. The choice of material systems and fabrication techniques in LED construction is guided by two primary goals—maximization of light generation in the chip material, and the efficient extraction of the generated light. Although the radiative recombination process is desirable in LED design, it is not the only recombination mechanism that is possible in semiconductors. An obvious goal in LED design, given the factors just described, is to maximize the radiative recombination of charge carriers relative to the nonradiative. The radiative lifetime for a particular semiconductor largely determines whether radiative recombinations occur before nonradiative. Silicon and germanium are examples of indirect semiconductors, in which radiative recombination of injected carriers is extremely unlikely. The wavelength (and color) of light emitted in a radiative recombination of carriers injected across a p-n junction is determined by the difference in energy between the recombining electron-hole pair of the valence and conduction bands.
As previously discussed, maximization of light generation in the diode semiconductor material is a primary design goal in LED fabrication.
Figure 7 illustrates the escape of light from a layered semiconductor chip of refractive index n(s) into epoxy of lower index (n(e)).
The proportion of light emitted from an LED chip into the surroundings is dependent upon the number of surfaces through which light can be emitted, and how effectively this occurs at each surface. Most of the LED structural arrangements rely on a secondary growth step to deposit a single-crystal layer on top of a single-crystal bulk-grown substrate material. The techniques of epitaxial crystal growth involve deposition of one material on another, which is closely matched in atomic lattice constants and thermal expansion coefficient to reduce defects in the layered material. The details of the various epitaxial structures employed in LED fabrication are not presented here, but are discussed in a number of publications.

Even though it does not typically contain the p-n junction region, the LED substrate material becomes an integral part of the function, and is chosen to be appropriate for deposition of the desired epitaxial layers, as well as for its light transmission and other properties.
The transparent substrate (TS) chip is designed to increase light extraction by incorporating a substrate that is transparent to the wavelength of emitted light. The first commercial light emitting diode, developed in the 1960s, utilized the primary constituents gallium, arsenic, and phosphorus to produce red light (655-nanometer wavelength). Changes in the elemental proportions, doping, and substrate materials resulted in development of gallium-arsenide-phosphorus (GaAsP) diodes producing orange and yellow emission, as well as a higher-efficiency red emitter. More recently, blue LEDs have been developed based on gallium nitride and silicon carbide materials. Solid-state researchers have sought to develop a bright blue light source since the development of the first light emitting diodes. The role of the gallium-indium-nitride semiconductor material system extends to the development of white-light diodes. Whereas conventional light sources exhibit an average output of 15 to 100 lumens per watt, the efficiency of white LEDs is predicted to reach more than 300 lumens per watt through continued development.
White LEDs are certainly suitable for display and signage applications, but in order to be useful for general illumination (as hoped), and for applications demanding accurate and aesthetically pleasing color rendering (including illumination for optical microscopy), the manner in which "white" light is achieved must be seriously considered.
A chromaticity diagram is a graphical means of representing the results obtained from mixing colors. Another means of generating white light is by combining the emission of three colors that will produce the perception of white light when they are combined in the proper power ratio. The combination of red, green, and blue diode chips into one discrete package, or in a lamp assembly housing a cluster of diodes, allows the generation of white light or any of 256 colors by utilizing circuitry that drives the three diodes independently. Most white-light diodes employ a semiconductor chip emitting at a short wavelength (blue, violet or ultraviolet) and a wavelength converter, which absorbs light from the diode and undergoes secondary emission at a longer wavelength.
The first commercially available white LED (fabricated and distributed by the Nichia Corporation) was based on a blue-light-emitting gallium-indium-nitride (GaInN) semiconductor device surrounded by a yellow phosphor.
The relative contributions of the two emission bands can be modified to optimize the luminous efficiency of the LED, and the color characteristics of the total emission.
White light diodes can generate emission by another mechanism, utilizing broad-spectrum phosphors that are optically excited by ultraviolet radiation. Dyes are another suitable type of wavelength converter for white diode applications, and can be incorporated into the epoxy encapsulant or in transparent polymers. White light LEDs based on semiconductor wavelength converters have been demonstrated that are similar in principle to the phosphor conversion types, but which employ a second semiconductor material that emits a different wavelength in response to the emission from the primary source wafer. Because white light can be created by several different mechanisms, utilizing white LEDs in a particular application requires consideration of the suitability of the method employed to generate the light. LED lighting has become increasingly popular over the years due to its lower usage costs, energy efficiency and better performance when compared to conventional lighting technologies.
This safe, long lasting and robust form of lighting is used in a wide range of settings including domestic households, traffic light systems, supermarkets and retail outlets, intelligent building systems, automotive industries, schools and colleges and communication technologies. LED stands for ‘Light-Emitting Diode’ and has been around for many years, making its first appearance back in 1962.
The first LED was a visible-spectrum ‘red’ light and was used in indicator lamps but the addition of visible, infrared and ultraviolet LED’s broadened its reach.
A single LED light is comprised of a series of electrons that together with a semi-conductor material produces a beam of light whilst releasing a small amount of heat, via a heat sink, at the same time.
LED lights are available in different colours and wavelength spectrum, from infrared at one end through to visible red, green and blue and then ultraviolet at the other end.
General purpose lighting as used in domestic or commercial environments requires white light.
The broader the spectrum of white light emitted the higher the colour rendering index (CRI) of the LED light. LED lighting emits light in a particular direction whereas incandescent and fluorescent lights emit light (and heat) in all directions. So, they only use heat and light when needed which is less wasteful and more energy efficient. ABOUT LEDA Light Emitting Diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction of p-n junction. ABOUT USTeknovision Allied Products was formed in Mumbai in the year of 1985 for manufacturing DC Tube lights and inverters for Buses and Trains.
LED tube lights are commonly used in various lighting facilities to serve as a replacement light source for traditional fluorescent tubes. With the continuing development and progress of science and technology, lighting systems based on light emitting diode (LED) light sources undoubtedly are a full-fledged technology in the lighting field. An LED lamp as a replacement for a fluorescent tube typically includes a plurality of LEDs assembled on one or maybe more printed circuit boards. Perfect for a wide range of applications, Eastar Lighting’s LED tube lights are ideal energy saving alternative to linear fluorescent light bulbs. Our tube lights are typically designed as single end powered to achieve easy installation and effectively eliminate the shock rock. The various types of diodes enable different kinds of application specifications to be met. The avalanche effect occurs when the reverse electric field across the P-N junction causes a wave of ionization, reminiscent of an avalanche, leading to a large current. The energy is released in the form of light when the diode is switched ON or forward-biased and the electrons combine with the holes.
A laser is formed when a LED-like structure is contained in a resonant cavity formed by polishing the parallel end faces.
Photodiodes can be used in solar cells, in photometry, in optical communications or to generate electricity. It can be used as a low-loss rectifier, although its reverse leakage current is generally higher than other diodes. Tunneling is an effect that is caused by quantum mechanical effects when electrons pass through a potential barrier.

These diodes act as capacitors, and capacitor plates are formed by the extent of conduction regions and the depletion region as the insulating dielectric. Zener and switching diodes are connected in series and in opposite directions to balance the temperature coefficient to near zero. The first series of LED lights were used in electronic display devices and laboratory equipment before expanding into consumer devices such as radios, telephones, calculators and televisions. By mixing the light from red, green and blue LED’s, using electronic circuits to control the blend. This is important in terms of now natural an object looks when placed under a lighting source. The color of the emitted light depends on the composition and condition of the semiconducting material used, and can be infrared, visible, or near-ultraviolet. Our Inverters and Fittings for buses got approval from almost all city and state transport undertakings such as DTC Delhi, BEST Mumbai, AMTS Ahmedabad and Indian Railways.
Fluorescent tube light fixtures are typically found in offices, institutions, shops, garages and many other places.
An LED is a semiconductor diode that transforms electric energy efficiently straight into spontaneous and non-coherent electromagnetic radiation at visible and virtually infrared wavelengths by electro-luminescence at a forward-biased pn junction. The LED circuit board(s) is usually enclosed within a housing this includes a metallic housing and also a transparent plastic housing. They have standard bi-pin G13 sockets and fit into existing fixtures without hassle and are compatible with instant start ballasts, require basically no modifications to your existing fixture, no ballast and no rewiring. As a result of the properties of these different diode types, different semiconductor diode types can be used to perform different functions. Avalanche diodes are designed to break down at a well-defined reverse voltage without being destroyed. The color of light depends on the energy gap of the semiconductor and produces wavelengths from the infrared to the near ultraviolet depending on the material.
A short wavelength blue LED is coated with different coloured phosphor materials that convert this from a short wavelength to a broad-spectrum white light.
LED lighting tends to give a higher CRI score as compared to fluorescent and incandescent lighting.
A fluorescent lighting fixture includes one or more fluorescent tubes, with each tube having an end cap on each end of a most commonly cylindrical glass tube. LED light sources feature low energy consumption, swift in response, and dramatically reduced maintenance costs. The metallic part of the housing behaves as a heat dissipater whilst the plastic portion of the housing shields the LEDs from external environments. Inside the tube is confined a mixture of gases which may induce a coating on the inside of the tube to fluoresce when electrical power is conducted through the gas from one end of the tube to the other.
They have substantially longer life and they also use much less power than fluorescent tubes of equivalent output.
The LEDs are attached to the lower side of the circuit board and electrically connected to the circuit board. Our LED tube lights are carefully designed to meet up with the highest manufacturing standards. These lights provide an unmatched energy savings of over 60% without compromising brightness and color rendering, and with the ability to operate in extreme temperature environments (-40°C to +55°C), more robust and resistant to cold environments than normal fluorescent tubes.
Every time a fluorescent tube is energized, the mercury vapor within the tube will be activated, giving out ultraviolet radiation.
They utilize premium quality SMD LEDs, which feature low light decrease over time and exceptional heat dissipation; The high quality aviation aluminum housing prevents internal heat buildup by way of a design allowing efficient heat dissipation. The operational lifetime of our LED lamps is 30,000 to 50,000 operation hours, which implies much fewer replacements compared with fluorescent tubes. Our AC series eliminates the driver circuits and use high voltage power input with extreme safety protection.
When the ultraviolet radiation strikes a phosphor coating the interior of the tube, visible light is produced. Owing to these advantages, a lot of traditional light bulbs or light tubes are gradually replaced with LED tube lights. High efficiency constant current drive system, with heat protection system, can also work under unstable voltage. The AC series LED tube lights are dimmable, a unique feature seldom found on other manufacturer’s tubes.
Fluorescent lamps tend to be more durable, economical and efficient when compared with incandescent lamps, in which most of the electrical energy generates heat instead of light. The power supply is connected to the lighting component and located on the upper side of the circuit board. High color rendering index, soft and wide light emitting, high light extracting rate, our LED tube lights combine innovative optical and mechanical design features to achieve a light distribution comparable to traditional fluorescent lamps, providing illumination without flickers and glare. However, fluorescent lamp tubes may have certain disadvantages for instance a short life time, easily broken filaments, flickering light that triggers eye strain plus some ultraviolet radiation. Moreover, the ends of tube can easily turn black over time and thus restricting the light output. On the inside of LED tubes, you will find a printed board or a corresponding structure, where LEDs and electronic current supply components they need are mounted.
The power supply converts the alternating voltage of the mains into direct voltage and to regulate the direct current required by the LEDs. LEDs are different from fluorescent tubes in that basically a power supply or ballast capable of converting high voltage AC line current to a somewhat lower voltage DC input current to the LEDs is required. When the LED tube light is employed to replace the fluorescent tube in a lighting fixture, the fluorescent tube ballast and starter, if any, are taken off from the lighting fixture at the time of installation.

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