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Title: Power management and power conditioning integrated circuits for near-field wireless power transfer
Author: Fan, Philex Ming-Yan
ISNI:       0000 0004 7651 4622
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2019
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Near-field wireless power transfer (WPT) technology facilitates the energy autonomy of heterogeneous systems, significantly augmenting complementary metal-oxide-semiconductor field-effect-transistor (CMOS) technology. In low-power wearable devices, existing power conditioning integrated circuits do not maximize the power factor (PF) for rectification and power conversion efficiency (PCE) due to multiple conversion. Additionally, there is no core power management for the entire power flow. The majority of the research focuses on active rectifiers, which reduce the turn-on voltage for rectification. Certain studies target the output voltage regulation via feedback to the transmitter or direct battery charging without power maximization. Firstly, this study investigates a high-power factor WPT front-end circuit that is namely the mono-periodic switching rectifier (MPSR) and implemented in a 0.18µm 1.8V/5V CMOS process. Integrated phase synchronizers are used to align the waveshape of a wirelessly-coupled sinusoidal voltage source in a receiving coil to the corresponding conducting current. Using this approach, the PF can be increased from roughly 0.6 to unity without requiring any wireless or wired feedback to the transmitter. The proposed MPSR can also provide AC-DC rectification, and step up and down the sinusoidal voltage source's peak amplitude using a pulse-width modulator. Measured voltage conversion ratios range between 0.73X and 2X, and the PF can be boosted up to unity. Secondly, the wireless power system-on-chip (WPower-SoC) is proposed and implemented in a 0.18µm 1.8V/3.3V CMOS process. The WPower-SoC integrating power management can provide rectification, output voltage regulation, and battery charging. Additionally, the implementation of feedforward envelope detection (FED) can reduce the variation in a wireless power link and improve load transient responses. Simulated results demonstrate that 5% of the output voltage regulation is improved when an output load changes. Moreover, the FED reduces approximately 40% of the transient response time. Overshoot and undershoot voltages are decreased by 23% and 26.5%, respectively. The measured output voltage regulates at 3.42V and can supply output power up to 342mW. A temperature sensor as part of the power management core remains active when the WPT receivers enter sleep mode to prolong the battery usage time. In the final part of this study, a nano-watt high-accuracy temperature sensing core is implemented in a 0.18µm 1.8V/3.3V CMOS process that can self-compensate the temperature shift without the need for additional compensating techniques that consume extra power.
Supervisor: Hasko, David Sponsor: Taiwan Cambridge Scholarship
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Near-field wireless power transfer ; Power Management ; Unity power factor ; M0N0-periodic switching rectifier ; AC-DC rectifier ; Pulse-width modulation ; Wireless power system-on-chip ; Feedforward envelope detection