A 96%-efficiency and 0.5%-current-cross-regulation single-inductor multiple floating-output LED driver with 24b color resolution

Hsiang An Yang, Wen Hau Yang, Ke-Horng Chen, Chin Long Wey, Ying Hsi Lin, Chao Cheng Lee, Jian Ru Lin, Tsung Yen Tsai, Shin Chi Lai

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

11 Scopus citations

Abstract

Lighting flicker, a rapid and repeated change over time in the brightness of light, has long been known to cause illness in humans that ranges from headaches to seizures. Thus, [1] has specified the dimming frequency, fDIM, larger than 3kHz to achieve a no-observable-effect flicker level. State-of-the-art LED drivers employ the SIMO topology with four channels in Fig. 12.7.1, to deliver energy to each LED using the time-multiplexing (TM) control technique [2-4], in which the luminance is controlled by the dimming signals. Two major shortcomings for such approaches are: (1) Sequential dimming signals; and (2) Current cross-regulation (CCR) effects. In [2], the LED drivers with TM control result in only 9b color resolution at the dimming frequency of 1.5kHz, which may cause flicker hazard. Besides, the complete white-red-green-blue (WRGB) sequence needs a total of four switching periods to light up the 4 LEDs separately. On the other hand, due to inherent rising and falling delay of the hysteretic current control (HCC) circuit, tdr and tdf respectively, the CCR effect seriously affects the accuracy of the controller when the inductor current slope is varied. For example, with L=15μH, VIN=20V, VR=2.5V, VG=3.5V, tdr=300ns and tdf=250ns, the SIMO will result in 4% CCR between Iavg,R and Iavg,G when the average LED current is 1A. More specifically, with the same color in the sequence, voltage regulation may be disregarded when regulated constant current through the sensing resistor RSEN is used as a negative feedback control. However, when different colors are in sequence, where VO, =VR, VG, VB, or VW, are different, large voltage cross-regulation (VCR) across the RSEN occurs and so does the CCR. The CCR effects become an open question for enhancing LED current accuracy. For alleviating the CCR effect, the discontinuous conduction mode (DCM) has been applied for TM control in [3]. However, with the limited output current in DCM, low output power resulted and large output capacitors were required to suppress the VCR.

Original languageEnglish
Title of host publication2016 IEEE International Solid-State Circuits Conference, ISSCC 2016
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages230-231
Number of pages2
ISBN (Electronic)9781467394666
DOIs
StatePublished - 23 Feb 2016
Event63rd IEEE International Solid-State Circuits Conference, ISSCC 2016 - San Francisco, United States
Duration: 31 Jan 20164 Feb 2016

Publication series

NameDigest of Technical Papers - IEEE International Solid-State Circuits Conference
Volume59
ISSN (Print)0193-6530

Conference

Conference63rd IEEE International Solid-State Circuits Conference, ISSCC 2016
CountryUnited States
CitySan Francisco
Period31/01/164/02/16

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