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Light-emitting diodes (LEDs) are becoming the dominant lighting source over their conventional counterparts. Besides the benefits of high efficiency and long lifetime, LEDs also show great potential for high-speed data transmission because of their wide bandwidth (BW). In addition to offering general lighting, the light output can be modulated with fast-switched LEDs to achieve visible light communication...
Ultra-low-voltage operation is highly demanded in a system that adopts the DVFS scheme, e.g., a portable device that sustains days-long standby with a tiny battery. Such a system usually embeds modules that have specific minimum supply voltages. Point-of-load low-dropout regulators (LDOs) are used to power these modules as per the required applications, from a global supply rail Vdd. The global Vdd...
Long-term-evolution (LTE) communication enables high data-rates but degrades the efficiency of the power amplifiers (PAs) due to high peak-to-average power ratios of transmitted signals. Envelope tracking (ET) and envelope-elimination-and-restoration (EER) techniques have been proposed to improve the PA efficiency by adapting the PA supply voltage to the envelope. Linear PAs in ET systems are mostly...
A theoretical analysis of constructing a reconfigurable TEG array is presented in this paper. All possible combinations of 2-TEG and 4-TEG arrays are investigated and the cause of intrinsic maximum power loss is analyzed for some combinations. Based on the analytic induction, an optimized and universal method to construct a reconfigurable TEG array using only resistive switch, and being expandable...
This paper proposes a single on/off reference tracking buck converter for DVFS application with a novel turning point prediction based on the turning point of the output voltage. The equation to determine the turning point of the output voltage for optimal reference tracking is analyzed and implemented by a current multiplier and divider circuit. In addition, a new reference tracking scheme is introduced...
An analytical study of designing power stage for the emerging digital LDO is presented in this paper. Two widely adopted sizing options are discussed, namely binary and multiple-unary weighted power stage sizing. Both methods target at realizing a balanced speed and resolution of the digital LDO. The binary sizing benefits the large current step, however, in average, may render a more oscillating...
This paper analyzes and compares two methods to measure the loop-gain function of high-frequency DC-DC converters. A guideline is given on the measurement setups, component selection and situations that should be avoided. The correctness of the presented methods is verified by measuring the gain and phase transfer function of a 50-MHz 3-level buck converter. The measurement results fit well with the...
In this paper, a 50-MHz 5-V input 3-W output 3-level buck converter is presented. A real-time flying capacitor (CF) calibration is proposed to ensure a constant Vg/2 voltage across the CF, which is essential to ensure the reliability and maintain the advantages of 3-level converters. A 0.6–4.2V wide output range, a 90% peak efficiency and a 23–29ns/V reference tracking response are observed in measurements...
A more accurate steady state analysis of the zero-voltage switching quasi-resonant (ZVSQR) converter is conducted in this paper. The conversion ratio equation and the conditions to achieve zero-voltage switching (ZVS) are derived. According to the analysis, a ZVSQR converter can be designed to operate within a wider input voltage range. A ZVSQR inverted buck converter is simulated as an example to...
A 65-nm external capacitor-less asynchronous digital low drop-out regulator (DLDO) with adaptive sizing and fast transient response is presented in this paper. Operating at a wide input voltage range from as low as 0.6V to 1V, this DLDO is capable of delivering a maximum current of 500mA with 50mV drop-out voltage. The proposed adaptive sizing featured by row-column-bit 3-dimensional (3D) power stage...
A digital low drop-out regulator (DLDO) load regulation enhancement technique which includes soft multi-step switching and adaptive timing is presented in this paper. As multi-step switching is widely used to balance the speed and resolution, a power-efficient method to improve the poor resolution during the switching between coarse- and finegrained regulations is in demand. The proposed technique,...
With the emergence of nanoscale material-based energy harvesters such as thermoelectric generator and microbial fuel cells, energy-harvesting-assisted self-powered electronics systems are gaining popularity. The state-of-the-art low-voltage CMOS boost converter, a critical voltage converter circuit for low power energy harvesting sources will be reviewed in this paper. Fundamentals of the boost converter...
This paper presents a 95VAC-120VAC mains powered converter-free LED driver for general lighting application. A quasi-constant power control scheme is proposed to significantly reduce the low-frequency-flicker, combined with a valley fill circuit to maintain good power factor performance. The driver achieves 88.2% efficiency and 0.92 PF with only 18% flicker at 110VAC 60Hz input and does not require...
A systematic analysis of 3-level integrated buck converters is conducted in this paper. Detailed derivations of the working principles, voltage conversion ratio and output voltage ripple are given. In particular, the system loop gain of 3-level buck converters is analyzed, which provides guidance on designing fast and robust 3-level converters. The derived loop gain is verified with time-domain small...
In this paper, a low substrate loss, monolithically integrated power inductor for compact LED drivers is designed and experimentally demonstrated. A 5.2 μH inductor is embedded at the backside of the silicon substrate, and the low-k, insulating material SU-8 is used to reduce the substrate loss. The inductor achieves a DC resistance of 2.3 Ω and a peak Q factor of 22 at 3.4 MHz. The inductor, controller,...
Reducing the supply voltage of digital circuits to the sub- or near-threshold regions minimizes dynamic power consumption and achieves better efficiency [1]. This technique is widely used in energy-efficient applications, and is especially beneficial for wirelessly powered devices such as wearable electronics, biomedicai implants and smart sensor networks. Such devices have long standby times and...
This work first generates ±1 V output via the self-startup pulse transformer boost converter. Another on-chip single-stage voltage tripler then generates 3 V output from the extra output power of boost converter, which is shunted otherwise. Higher voltage headroom is instrumental for sensor, analog and RF circuits. Charge pump clock frequency is adaptively tracking the input voltage, which is sensed...
Recent advancement in commercial MEMS-based piezoelectric energy harvesters has enabled further reduction of both system cost and size as the device dimension scales down. A nature inspired interface circuit by mimicking water bucket fountain to harvest piezoelectric charge is presented. The proposed architecture offers built-in input voltage protection, harvests electrical energy using minimal switching...
Boost converter designed using miniaturized high turn-ratios transformer is an excellent circuit to achieve fully electrical autonomous start up at low input voltage. Nevertheless, at regulated output voltage, its power conversion loss at high input voltage is significant. A 2× cross-coupled charge pump is added to assist energy harvesting at high input voltage. The charge pump is turned on whenever...
This study describes a through-silicon-underfill dispensing that the encapsulant is dispensed through through-silicon-vias (TSVs). The TSVs function as entrances for encapsulant dispensing or paths for fluid flow. Typically, the inflow for TSV dispensing may be flow with a constant speed or free droplets. A model was developed to investigate the filling time and the pressure distribution for the quasi-steady,...
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