How LED Diodes Work

How LED Diodes Work

Like a regular diode, LEDs allow current to flow in only one direction. When this happens, the electrons from the n-region and holes from the p-region recombine to emit light.

LEDs have two leads and are marked with a flat notch that indicates which is the anode and which is the cathode. The PN junction inside is surrounded by an epoxy resin shell that acts like a lens, concentrating the light output.

Power

The power of a LED is determined by the current that flows through it when it’s operating at its recommended forward voltage. It is also affected by the amount of heat dissipated in the resistor that’s used to limit current.

As with other diodes, an LED only allows current to flow in one direction. When current does flow through the diode, it releases photons dc to ac inverter into the surrounding air, emitting light in the process. The color of the emitted light depends on the type of semiconductor material used and impurities applied during manufacturing.

A common method for supplying power to an LED is through a series resistor, which is inexpensive but inefficient, as energy is wasted in the resistor’s heating effect. To minimize waste, it is a good idea to check the LED datasheet for its suggested forward voltage and current rating, and use Kirchhoff’s circuit laws and Ohm’s law to calculate the appropriate resistor value.

Another alternative is to use an LED driver that is designed solely for driving these devices. This reduces wiring complexity and provides better current regulation, while offering other features like current matching between the LEDs in a parallel configuration.

Voltage

A LED is a PN junction diode that emits light only when it is forward-biased. In this condition, electrons fall from a higher energy band to a lower one and radiate photons of the corresponding wavelength. Unlike ordinary diodes, an LED does not have a negative voltage across its semiconductor junction and must be current-limited with a series resistor to prevent it from burning out due to overcurrent.

The LED’s color is determined by the combination of elements such as gallium, arsenic and phosphorus used in its manufacture. Each manufacturer’s LEDs are a bit different and therefore each can have a slightly different emitted wavelength. However, this variation is typically quite small and does not affect the overall appearance of the LED.

The luminous flux of an LED is measured using a calibrated 2.5-m integrating sphere. The measurement system is configured to measure total spectral radiant flux in the 360- to 830-nm wavelength range. NIST offers calibration services for this method of measuring LED spectral radiant flux. The luminous flux of an LED can also be measured with a voltohmeter set up to measure DC current in the forward direction.

Current

The current of a led diode is controlled by its driver. Increasing the current makes it brighter but will also increase the power consumption and heat generation. Similarly decreasing the current will decrease the brightness but will also reduce the power consumption and heat generation.

Since an LED is a specialised type of diode (it is a PN junction diode), it only allows current to flow in the forward direction and blocks current in the reverse direction. Its efficiency is low and it requires more current to operate than a normal p-n junction diode.

It does not start to conduct until the voltage reaches its knee voltage and then the current starts increasing exponentially which is directly proportional to the intensity of light it emits. To ensure that the knee voltage is not exceeded, it is important to use a current limiting resistor. Its value is usually around 330 Ohms but can vary depending on the particular LED model used and the current specifications.

Material

The emitted light colour of an LED is determined by the semiconductor compound used to make its PN junction during manufacturing. Coloured LEDs are made using a variety of semiconductor compounds such as red, green, yellow, blue and infrared and the spectrum that is emitted covers most of the visible light range.

To make a LED emit light, it needs to be connected in a forward biased condition across a power supply. This will push electrons from the n-side to the p-side of the diode, leaving holes behind. When the minority charge carriers reach the active region, they recombine and radiate energy in the form of visible light. This process is called Electro-luminescence.

The emitted light intensity is proportional to the current passing through the LED and is regulated by a resistor to avoid overheating. The peak spectral wavelength of an LED rtc electronic component is also dependent on the energy band gap of the semiconductor material used for its manufacture. For this reason, it is important to know the energy band gap of the semiconductor material that is used in an LED’s production to ensure its maximum output spectral wavelength matches that of the intended application.

Applications

LEDs are used as indicators and can also be used in various other applications. They are powered by a DC power supply and have series resistors that prevent them from getting too hot. This reduces the current flow through the LED and limits it to about 20mA. If it is too high, the LED will permanently damage its junction.

LED is a chip of semiconductor material that is doped with impurities that creates a boundary for charge carriers. When electricity flows into the semiconductor, it jumps from one side of the boundary to the other, releasing energy in the process. This energy usually leaves as heat, but in the case of LEDs it is dissipated as light.

The structure of the LED includes three regions of semiconductor material, a P-type region, an N-type region, and an active region. The active region has holes, while the P-type layer has electrons. When you apply a forward voltage to the LED, electrons move from the N-type region to the active region, and then combine with holes. This produces light, and the emitted light is proportional to the amount of current flowing through the diode.