Abstract
AC-DC LED drivers may have a lifespan shorter than the lifespan of LED chips if electrolytic capacitors are used in their construction. Using film capacitors solves this problem but, as their capacitance is considerably lower, the low-frequency ripple will increase. Solving this problem by limiting the output ripple to safe values is possible by distorting the input current using harmonic injection technique, as long as these harmonics still complies with Power Factor Regulations (Energy Star). This harmonic injection alleviates the requirements imposed to the output capacitor in order to limit the low-frequency ripple in the output. This idea is based on the fact that LEDs can be driven by pulsating current with a limited Peak-To-Average Ratio (PTAR) without affecting their performance. By considering the accurate model of LEDs, instead of the typical equivalent resistance, this paper presents an improved and more reliable calculation of the intended harmonic injection. Wherein, its orders and values can be determined for each input/output voltage to obtain the specified PTAR and Power Factor (PF). Also, this harmonic injection can be simply implemented using a single feedback loop, its control circuit has features of wide bandwidth, simple, single-loop and lower cost. A 21W AC-DC buck converter is built to validate the proposed circuit and the derived mathematical model and it complies with IEC61000 3-2 class D standard.
Highlights
LED technology has several merits over conventional lamps such as: high-efficiency, very long lifespan, lower power consumption, low maintenance cost and instantaneous switch-on [2,3]
This paper introduces a step modify the harmonic to be simpler by using an accurate model chip. loop, that can achieve the target Peak-To-Average Ratio (PTAR) and Power Factor (PF) by andmeans more of economic through using justfor one feedback means of using an accurate model for LED chip
It is in this script where using the real model of the LED rather than the typical equivalent resistance makes the conversion ratio to have a significant impact on PTAR and PF
Summary
LED technology has several merits over conventional lamps such as: high-efficiency, very long lifespan (approximately 100,000 h [1]), lower power consumption, low maintenance cost and instantaneous switch-on [2,3]. The idea is to inject predefined harmonics into the input current to (as a consequence of the ripple) results in a change in the chromaticity coordinates, color correlated limit the PTAR of the output. 1a–c shows different temperature (CCT), color rendering index (CRI), flux and efficacy degradation, so LED light is perceived harmonics combinations for the LED current [10,11] with the result of a lower PTAR if those as bluish-white harmonics are wisely selected. The idea is to than injectinpredefined into theSecond, input current shows the double line frequency output current combined with the fifth harmonics In this case, limit the PTAR of the output LED current while observing PF regulations. Double line frequency output current combined with the fifth harmonics In this case, the resulting a two-stage driver is first introduced.
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