Browsing by Author "Liu, Chi-Wei"

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A Single-Inductor Triple-Input-Triple-Output (SITITO) Energy Harvesting Interface with Cycle-by-Cycle Source Tracking and Adaptive Peak-Inductor-Current Control
(2017-01-01)
Liu, Chi-Wei
;
Chung, Ming-Jie
;
Lee, Hui-Hsuan
;
Liao, Pei-Chun
;
Chen, Po-Hung
In this paper, a single-inductor triple-input-triple-output (SITITO) buck-boost converter with cycle-by-cycle source tracking (CCST) is developed for multi-source energy harvesting. The proposed CCST is capable of harvesting power from the PV and TEG simultaneously, and automatically selects the appropriate source according to the maximum power point (MPP) of the transducers in each switching cycle. The converter provides two regulated outputs for the analog (V-OUT1 = 1.2 V) and the digital (V-OUT2 = 0.4-0.6 V) circuits, while storing the excess energy in a storage capacitor (C-OUT3). An adaptive on-time (AOT) circuit with an adaptive peak-inductor-current (APIC) control is developed for dynamically adjusting the on-time based on the input voltage (V-IN) to obtain high conversion efficiency under different V-IN. The proposed converter achieves a peak efficiency of 84.4% with an available input voltage of 0.05 V to 0.8 V. Compared to the conventional constant peak-inductor-current (CPIC) control, the proposed APIC improves 11 % efficiency at low V-IN.
An 82.9%-Efficiency Triple-Output Battery Management Unit for Implantable Neuron Stimulator in 180-nm Standard CMOS
(2019-05-01)
Liu, Chi-Wei
;
Chen, Yi-Lun
;
Liao, Pei-Chun
;
Lin, Shiau-Pin
;
Wang, Ting-Wei
This brief presents a high-efficiency battery management unit combining a single-inductor dual-output (SIDO) buck converter with two charge pumps (CPs) to provide three voltage levels (6 V, -6 V, and 2 V) for neuron stimulators in implantable medical devices. The stacked power stage in the buck converter mitigates the voltage stress issue in the power stage to manage 3.2-4.8 V battery voltage. By cascading a buck converter and CPs, the voltage across the CP power stage is reduced to generate 6 V and -6 V high voltage outputs without using high voltage devices. As a result, the proposed battery management could provide 6 V, -6 V, and 2 V output voltages from 3.2 to 4.8 V input voltage using a 180-nm standard CMOS process. The measurement results demonstrate that the proposed battery management achieved a peak efficiency of 82.9% with an available input voltage of 3.2-4.8 V.
Dual-Source Energy-Harvesting Interface With Cycle-by-Cycle Source Tracking and Adaptive Peak-Inductor-Current Control
(2018-10-01)
Liu, Chi-Wei
;
Lee, Hui-Hsuan
;
Liao, Pei-Chun
;
Chen, Yi-Lun
;
Chung, Ming-Jie
In this paper, we present a single-inductor triple-input-triple-output (SITITO) buck-boost converter in a 0.18-mu m CMOS process for dual-source energy harvesting. The converter operates in the single-source mode, dual-source mode (DSM), and backup mode automatically by detecting the input and output conditions. Converter operation in the proposed DSM enables extraction of power from both a photovoltaic cell and a thermoelectric generator in one switching cycle for efficient power extraction. The cycle-by-cycle source-tracking approach selects the appropriate input source according to the maximum power point of the energy transducers. The adaptive on-time circuit with the proposed adaptive peak-inductor-current (APIC) control adjusts the on-time of power transistors to obtain high conversion efficiency under different input voltages. The experimental results demonstrate that the proposed SITITO converter has a peak efficiency of 84.4%. When compared with the conventional constant peak-inductor-current control, an efficiency improvement of 11% is obtained via the proposed APIC control.
Silicon microwire arrays decorated with amorphous heterometal-doped molybdenum sulfide for water photoelectrolysis
(2017-02-01)
Chen, Chih-Jung
;
Yang, Kai-Chih
;
Liu, Chi-Wei
;
Lu, Ying-Rui
;
Dong, Chung-Li
Silicon is a promising photocathode material for solar hydrogen evolution because of its small band gap, negative conduction band position, and ideal theoretical current density. In this study, p-type Si microwire (p-Si MW) arrays were prepared as photocathodes because of the large surface area and high light-harvesting capability. However, Si MWs suffered from low photocatalytic activity because of slow photo-induced carriers during driving of water-splitting reaction. Therefore, molybdenum sulfide (MoS2) with appropriate band alignment with p-Si material was employed for surface modification to function as a co-catalyst for collecting photo-generated minority carriers and reducing recombination possibility. The onset potential and current density at 0 V versus reversible hydrogen electrode (RHE) of Si@MoS2 MWs were + 0.122 V and -8.41 mA cm(-2). Heterometal atoms were employed to dope MoS2 co-catalyst and expose more sulfurterminated active sites to further boost photoelectrochemical performance. Optimal activity of Si@MMoSx (M = Fe, Co, Ni) was achieved by doping Co heteroatoms, and its turn-on voltage and photocurrent density at 0 V (vs. RHE) were respectively increased to + 0.192 V and -17.2 mA cm(-2). X-ray absorption spectroscopy was applied to demonstrate that Fe ions of FeMoSx were dichalcogenide materials, forming a composite with MoS2 and contributing better photoelectrolytic efficiency. By contrast, two-valent heteroatoms of CoMoSx and NiMoSx substituted the Mo4+ ions in MoS2. For charge compensation, more defects and edges were revealed as active sites of solar hydrogen production by adding Co or Ni dopants in MoS2 co-catalyst, which led to lower overpotential.
Single-Inductor Dual-Input Dual-Output Battery-PV Hybrid System With 2-D Adaptive On-Time Control for Internet of Things
(2020-03-01)
Lee, Hui-Hsuan
;
Liu, Chi-Wei
;
Takamiya, Makoto
;
Chen, Po-Hung
;
電子工程學系及電子研究所
In this article, we present a single-inductor dual-input dual-output power converter with two-dimensional adaptive-on-time (2-D AOT) control for Internet of things (IoT) applications. The proposed system combines energy from a 0.55-0.7 V photovoltaic (PV) module with a non-rechargeable 1.4-V zinc-air battery to extend the battery life. The proposed converter employs the buck-boost mode and the buck mode for the PV module and the battery, respectively, to produce two output voltages for different loading currents. The proposed 2-D AOT technique not only reduces the output voltage ripple but also improves the dual-source conversion efficiency over a wide input voltage range. Moreover, the response time of the self-tracking zero-current detector can also be improved by the proposed 2-D AOT. We fabricated the test chip using 0.18-mu m technology in an area of 1.9 x 2.2 mm(2). The measurement results demonstrated a peak efficiency of 92.5% with an input voltage range of 0.55-1.4 V. The output voltage ripple was less than 2.3% VOUT under different input voltage ranges.