Feed-Forward Scheme for an Electrolytic Capacitor-Less AC/DC LED Driver to Reduce Output Current Ripple

This paper designs a kind of new electrolytic capacitor-less LED (light-emitting diode) driver, which converts the commercial ac voltage to a pulsating current with twice the line frequency driving high-brightness LEDs. As no electrolytic capacitor is used, this driver possesses the unique advantage of long lifetime to match with that of LEDs. A method of injecting the third and fifth harmonics into the input current to reduce the peak-to-average ratio of the output current is also proposed. A 25V, 0.35A output prototype is built and tested in the laboratory, and the experimental results are presented to verify the effectiveness of the electrolytic capacitor-less LED driver and its control method.

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Three-phase switched capacitor converter without electrolytic capacitor for Power LEDs and low output current ripple

2015 IEEE 24th International Symposium on Industrial Electronics (ISIE) ◽

10.1109/isie.2015.7281644 ◽

2015 ◽

Author(s):

Ronaldo P. Coutinho ◽

Edilson M. Sa ◽

Kleber C.A. de Souza ◽

Pedro H. Miranda ◽

Fernando L. M. Antunes

Keyword(s):

Electrolytic Capacitor ◽

Switched Capacitor ◽

Output Current ◽

Three Phase ◽

Switched Capacitor Converter ◽

Current Ripple

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AC–DC Flyback Dimmable LED Driver with Low-Frequency Current Ripple Reduced and Power Dissipation in BJT Linearly Proportional to LED Current

Energies ◽

10.3390/en13164270 ◽

2020 ◽

Vol 13 (16) ◽

pp. 4270

Author(s):

Yeu-Torng Yau ◽

Kuo-Ing Hwu ◽

Kun-Jie Liu

Keyword(s):

Power Dissipation ◽

Light Emitting Diode ◽

Low Frequency ◽

Output Current ◽

Led Driver ◽

Voltage Range ◽

Flyback Converter ◽

Linear Current ◽

Current Ripple ◽

Frequency Current

In this paper, a dimmable light-emitting diode (LED) driver, along with the low-frequency current ripple decreased and the bipolar junction transistor (BJT) power dissipation reduced, is developed. This driver is designed based on a single-stage flyback converter. On the one hand, the low-frequency output current ripple reduction is based on the physical behavior of the linear current regulator. On the other hand, when the voltage across the LED string is decreased/increased due to dimming or temperature, the output voltage of the flyback converter will be automatically regulated down/up, thereby making the power dissipation in the BJT linearly proportional to the LED current. By doing so, not only the power loss in the linear current regulator will be decreased as the LED current is decreased or the LED temperature rises, but also the output current ripple can be reduced. Furthermore, the corresponding power factor (PF) is almost not changed, and the total harmonic distortion (THD) is improved slightly. In addition, the LED dimming is based on voltage division. Eventually, a 30 W LED driver, with an input voltage range from 85 to 295 Vrms and with 24 LEDs in series used as a load, is developed, and accordingly, the feasibility of the proposed LED driver is validated by experimental results.

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The effect of capacitance on drive current of general lighting LED luminaires

Lighting Research and Technology ◽

10.1177/1477153517732811 ◽

2017 ◽

Vol 50 (8) ◽

pp. 1270-1281

Author(s):

AN Padmasali ◽

JE Noronha ◽

SG Kini

Keyword(s):

Service Life ◽

Capacitor Bank ◽

Light Output ◽

Electrolytic Capacitor ◽

Output Current ◽

Led Driver ◽

Drive Current ◽

Led Light ◽

Led Luminaire

The reliability of a LED luminaire depends on the reliability of each of its subsystems. Experience suggests that, of these subsystems, it is the LED driver that tends to fail earliest. Any LED driver has an electrolytic capacitor to limit the ripple current, which helps the luminaire to function appropriately. This paper describes the effects on ripple current of changes in the capacitance and thus on LED luminaire performance. A capacitor bank is developed containing electrolytic capacitor combinations to obtain 27 capacitance values in the range 0.017 to 1570 µF. Two commercially available LED downlighter luminaires of the same model and manufacturer were used for this study. The ripple current and lumen output values are observed after connecting each capacitance from the bank, and the percentage flicker is calculated. LED light output shows visible flicker for low capacitances up to 0.1 µF with percentage flicker above 100%, while percentage flicker for capacitors up to 100 µF is more than 50%. For capacitance values of 220 µF and more, the percentage flicker is less than 50%. For the LED driver the capacitor decides the amount of ripple in the output current, so this work helps in formulating metrics for determining the service life of LED luminaires.

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