Personnel

FICs - Prof. Wing-Hung Ki

Description

The concepts of wireless transmission of signal and power emerged together in the late 1880's. Certainly, the past century has witnessed the exponential growth of wireless transmission of signal (wireless communication), such as wireless telegraph (1896), AM radio (1906), color TV (1929), mobile radio (1950), GSM phone (1992), digital TV (1999), to iPhone 6 (2015). In comparison, the demonstration of wireless transmission of power (other than through tightly coupled transformers) lags far behind. However, two major applications are driving the development of wireless power transfer (WPT): one is on the (relatively) high-power side of wireless charging, for mobile gadgets and even for electric vehicles; and the other is on the (relatively) low-power side of wirelessly powered bio-medical implants. The bottleneck of WPT has been low power transfer efficiency due to weak coupling and poor directivity. In this research, we propose to first work on the backbone knowledge for designing high-efficiency resonant wireless power transfer (R-WPT) systems. For a WPT system with weak coupling, the link gain (voltage at load / source voltage) and the link efficiency (power consumed by load / power delivered from source) could be enhanced by adding a capacitor to resonate with the inductor both at the primary and at the secondary, such that the imaginary part of the reflected equivalent impedance could be cancelled or minimized. We propose to employ a design-oriented analysis to study R-WPT systems, to arrive at link gains and link efficiencies that could be optimized easily and interpreted physically by circuit-design engineers. The results of this part of research will be useful for both high-power and low-power applications. Our next step is to attend to low-power applications of implantable medical devices (IMDs). We propose to use two coils with different orientations in intercepting fluxes, as such, the associated link gains and link efficiencies has to be derived and optimized together. On the circuit level, we will develop one-stage power processing architectures that integrate AC-DC rectification with DC-DC regulation to reduce loss. We will also develop (integrated) circuit techniques to combine power from the two coils together to enhance directivity. Finally, we will design, fabricate and test the integrated circuit power management unit (PMU), and build and test the power transponder of a low-power 1-primary 2-secondary (1P-2S) R-WPT system for bio-medical implants. We will also develop strategies for testing the PMU and the power transponder individually, and for testing the complete system.

Source: RGC | ITF