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August 22, 2023

A light emitting diode (LED) is a semiconductor device that generates light through the recombination of holes and electrons and consists of an N-type and a P-type semiconductor. LEDs are innately direct current (DC) devices that only pass current in one polarity and are often driven by DC voltage sources that limit the voltage and current given to the LED via resistors, current regulators, and voltage regulators. As a result, a power source or "driver" is necessary to convert mains AC power to a DC voltage or current appropriate for driving the LEDs. An LED driver is a self-contained power source with outputs that correspond to the electrical characteristics of the LED array. Most LED drivers are built to supply consistent currents to the LED array. As a result, LEDs that rely on a driving circuit to operate at a constant current level are referred to as DC LEDs.



An alternating current (AC) supply, on the other hand, might be used to power the LED lighting system. An AC LED is an LED that operates directly from alternating current (AC) line energy rather than using a driver to convert the line voltage to direct current (DC). An AC LED chip is made up of a number of LED components that are built into a circuit loop or a Wheatstone bridge to be utilized directly in an alternating current field. An AC LED is also known as a high voltage light emitting diode (HV LED) since it lacks a current conversion driving component and may be used directly in mains electricity, which is both high voltage (220V in Europe and 110V in the United States) and alternating current (AC).



The typical LED luminaire has a complex driving circuit, which may result in higher production costs, a considerable reduction in operating life, less design freedom due to greater volume with additional driving and dimming circuits, low power efficiency, and system stability.


The inclusion of drive circuits in a DC LED lighting system has a number of negative consequences. To begin with, the service life of an electronic circuit is substantially less than that of an LED. Furthermore, because an LED's input load characteristics do not remain constant during its lifetime, but rather change with age and environmental circumstances, the compatibility between an LED and its driver may eventually decrease, resulting to unstable LED performance. The power converter affects the light emitting device's efficiency. The power losses inherent in such a power converter lower the light source's overall efficiency. To modulate the operational parameters, a driver circuit may incorporate resistive loads, inductive coils, capacitors, switching transistors, clocks, and other components. LED lamps and their LED drivers experience a variety of parasitic losses during operation, including heat, vibration, radio frequency or electromagnetic interference, switching losses, and so on. As time passes, environmental conditions and parasitic losses may cause the operational performance of LED lights to deteriorate to the point that they no longer meet the operational requirements.


Additional voltage transformers or rectifiers are not required for AC LEDs, and AC LEDs can work immediately by applying alternating current. As a result, the cost of an AC LED light is lower when compared to its DC counterpart, and circuit-related quality issues are decreased. Because the linear power supply does not require high frequency switching operation, electromagnetic interference (EMI) is no longer a worry. The transformation for lower voltage direct current is not required, which reduces energy consumption in power transformers. The power converter reduces power factor while increasing overall harmonic distortion of current. An AC-direct design's inherent efficiency allows for a high power factor of more than 0.9 with no additional power conditioning or power factor correction circuitry required. Another advantage of the AC LED arrangement is its inherent full-range dimmability, which eliminates the need for a dimming circuit. Compatibility with phase-cut (triac) dimmers is a key aspect of AC LED methods. It is frequently sought to use LED bulbs with dimming capabilities to provide variable light output.



Nonetheless, there is still room for development in the manufacture of AC LEDs. Because of the fast change in polarity at mains frequency, the light generated by AC-LEDs operated by the AC mains supply can exhibit an unacceptable level of optical flicker. This flicker can be annoying, especially in indoor lighting settings. The flicker issue can be resolved by using a rectifier and a capacitor, both of which are common components in DC LED drivers. Furthermore, LED lights with driver circuitry can be built to convert a wide range of AC mains voltage (e.g. 100-277V) into a possible constant load voltage and current. AC LEDs can only accept a narrow range of input voltage, such as 220-240V, limiting its use in applications with extreme voltage variations.



LEDs supplied by alternating current create a non-linear demand. LEDs supplied by AC power sources may have a lower power factor and higher total harmonic distortion as a result of non-linearity. An alternating current (AC) electric power system's power factor is defined as the ratio of real power to apparent power flowing to a load.

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