Design of a High Efficiency WLED Driver in 40 nm CMOS Technology

Ahmad, H.; Shahroury, Fadi R.

doi:10.1109/icm50269.2020.9331783

Cited by 3 publications

(6 citation statements)

References 7 publications

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“…A simple pulse skipping controller (PSC) is used to control the gates of the high-side switches. For optimal power efficiency of 18 WLEDs, typically enough for a smartphone backlight, WLEDs are arranged as three strings; each has 6 WLEDs [4]. There are two modes of operation: MDCC mode and PSC mode.…”

Section: The Proposed Architecture and Its Basic Operationmentioning

confidence: 99%

“…The WLED driver ideally operates in a similar manner to a voltage-regulated boost converter, except it regulates the output current through the string of LEDs with high power efficiency, especially in portable devices. Besides, there is a need for an accurate current within any string and among the different strings to guarantee consistency in brightness [4]. A multi-string WLED driver is a natural application of multi-independentoutput converters.…”

Section: Introductionmentioning

confidence: 99%

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A Multi-Output Multi-String High-Efficiency WLED Driver Using 40 nm CMOS Technology

Ahmad

Shahroury

Abuishmais

2021

JLPEA

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In this work, a multi-independent-output, multi-string, high-efficiency, boost-converter-based white LED (WLED) driver architecture is proposed. It utilizes a single inductor main switch with a common maximum duty cycle controller (MDCC) in the feedback loop. A simple pulse skipping controller (PSC) is utilized in each high-side switch of the multiple independent outputs. Despite the presence of multiple independent outputs, a single over-voltage protection (OVP) circuit is used at the output to protect the circuit from any voltage above 27 V. An open circuit in any of the strings is addressed, in addition to the LED’s short-circuit conditions. Excellent current matching between strings is achieved, despite the low ON-resistance (Rdson) of transistors used in the 40 nm process. Most circuits are designed in digital CMOS logic to overcome the extreme process variations in the 40 nm node. Compared to a single output parallel strings topology, a 50% improvement in efficiency is achieved relative to extremely unbalanced strings. Three strings are used in this proposal, but more strings can be supported with the same topology. Each string is driven by a 25 mA current sink. An input voltage of 3.2–4.2 V and an output voltage up to 27 V are supported.

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Section: The Proposed Architecture and Its Basic Operationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Multi-Output Multi-String High-Efficiency WLED Driver Using 40 nm CMOS Technology

Ahmad

Shahroury

Abuishmais

2021

JLPEA

Self Cite

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“…They provide a backlight plus dimming and brightness control. A DC-DC boost converter is very popular in building WLED drivers [1,2]. The available input voltage is usually the battery voltage (3.2 V to 4.2 V), while the needed output voltage is, relatively, much higher.…”

Section: Introductionmentioning

confidence: 99%

“…The electrical current that flows through the WLED determines its brightness. The forward voltage drop of a typical WLED varies depending on the type of semiconductor used in its fabrication and the manufacturing process's tolerances [1].…”

Section: Introductionmentioning

confidence: 99%

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Design Aspects of a Single-Output Multi-String WLED Driver Using 40 nm CMOS Technology

Shahroury¹,

Ahmad²,

Abuishmais³

2022

JLPEA

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This work presents various essential features and design aspects of a single-inductor, common-output, and multi-string White Light Emitting Diode (WLED) driver for low-power portable devices. High efficiency is one of the main features of such a device. Here, the efficiency improvement is achieved by selecting the proper arrangement of WLEDs and a proper sensing-circuit technique to determine the minimum, real-time, needed output voltage. This minimum voltage necessary to activate all WLEDs depends on the number of strings and the forward voltage drops among the WLEDs. Advanced CMOS technology is advantageous in mixed-signal environments such as WLED drivers. However, this process suffers from low on-resistance, which degrades the accuracy of the current sinks. To accommodate the above features and mitigate the low node process issue, a boost-converter that is single output with a load of a three-string arrangement, with 6 WLEDs each, is presented. The designed driver has an input voltage range of 3.2–4.2V. The proposed solution is realized with ultra-low power consumption circuits and verified using ADS tools utilizing 40 nm 1P9M TSMC CMOS technology. An inter-string current accuracy of 0.2% and peak efficiency of 91% are achieved with an output voltage up to 25 V. The integrated WLED driver circuitry enables a high switching frequency of 1MHz and reduces the passive elements’ size in the power stage.

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A Design Methodology of High-Efficiency Dimmable Current Sink for Current-Regulated Drivers

2022

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This paper proposes a high-efficiency and dimmable current sink topology along with a design methodology for low node processes. The design methodology is demonstrated using a boost-based WLED driver application. In this work, the focus is on current regulation rather than voltage regulation. Therefore, the proposed topology exploits a smaller and faster NMOS pass device, replacing the conventional PMOS-based LDO arrangement. An amplifier-boosted pass-transistor current sink topology combined with a 5-bit programmable degenerated source resistor is being utilized for high-efficiency and brightness control. The realized WLED driver validates the proposed topology and the design methodology utilizing 40 nm CMOS TSMC technology. The design takes advantage of the programmability of the resistor to enhance the system’s power efficiency. This programmable resistor enables dimmability via current segmentation with a 1 mA step for a total of 25 mA. For a 500 mV voltage ripple at the DC-DC converter output driving 6 WLEDs with a 3.2 V forward voltage drop each, a worst-case current ripple of 200 µA and simulated efficiency of 97.6% is achieved for optimum pass-transistor size.

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Design of a High Efficiency WLED Driver in 40 nm CMOS Technology

Cited by 3 publications

References 7 publications

A Multi-Output Multi-String High-Efficiency WLED Driver Using 40 nm CMOS Technology

A Multi-Output Multi-String High-Efficiency WLED Driver Using 40 nm CMOS Technology

Design Aspects of a Single-Output Multi-String WLED Driver Using 40 nm CMOS Technology

A Design Methodology of High-Efficiency Dimmable Current Sink for Current-Regulated Drivers

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