Pulse quietening at source for higher-frequency power and signal switching

Today's portable microelectronic systems, such as mobile telephones, require high energy efficiencies to further battery life. They also require compact electronics. Combining these two requirements poses a problem with relation to their power supplies, since it implies greater miniaturisation, high conversion efficiencies and high power densities.

Using silicon-based DC/DC converters places limits on how far these improvements can go. We intend to make use of a new gallium-nitride transistor technology to develop smaller, more efficient power supplies. Specifically, we will produce a 10W power supply in this new technology, with a high voltage conversion factor, and integrate it inside a contemporary microelectronics package.

The only way that this will work is to operate the new power supply at incredibly high switching frequencies (>100 MHz), which is 10-100 times faster than today's power supplies. The project then revolves around solving the challenges of: 1) how to operate such a power supply at very high frequencies; 2) how to integrate it into a small, modern, microelectronics package. We expect key challenges to be the creation of unacceptable electromagnetic emissions from the high switching speeds, and the need to accurately control the impedances of the circuit, since circuit impedances become more significant the faster one switches.

We will solve the challenges by deploying an advanced version of a drive-pulse shaping technique that we call "pulse quietening", and by using modern integration techniques, including the creation of a custom chip to control the new power supply. Our method is to create several prototypes, running at increasingly high speeds, from 1MHz up to 100 MHz. We will create models and theories about the most efficient way to drive the power supply transistors and measure the outputs, as well as furthering our knowledge and application of pulse quietening.

The project is structured in such a way as to impact both the academic sector and the commercial one. We will, for the first time, address the question of electromagnetic noise reduction in very fast power supplies, whilst simultaneously enabling their miniaturisation. The outputs from the project will include new theories and models of GaN FET transistors, waveform generation and measurement and electromagnetic noise reduction. Each of these represents a new contribution to the worldwide body of knowledge, and a key discovery in its own right.
Using the accepted methods of journal and conference publications as primary mechanisms, we will produce and disseminate a significant body of novel research contributions to the field. Specific outputs will include waveform shaping methods, measurement techniques, validated high-frequency models, reference layouts, reference switching aid-circuits, reference package equivalent electric circuit models, device design improvements, and design processes.

We have a detailed communication plan for engaging with the academic community and interested commercial parties. This will enable system designers in both realms to deploy our new high frequency switching techniques to reduce overall power losses in their power supplies and/or reduce the area, cost and packaging requirements of a microelectronic system. Existing techniques, such as DVFS, will be enhanced using our novel techniques, and we anticipate this would represent one initial direction for follow-on research.

The outputs from this project will address an immediate need in the UK's £62 billion commercial microelectronics sector and the projected US$8.4bn worldwide GaN FET sector.
The area is one where the UK remains a world-leader, and statements of support from UK-based companies, such as Imagination Technologies and multinational NXP can be found in the letters of support that accompany this proposal. Their enthusiasm for this project indicates its significance to industry.
The creation of an integrated, high-efficiency switched mode power supplies would help many UK companies to produce more energy efficient microelectronic devices than they currently do. This would result in smaller and cheaper devices and longer battery life, delivering a competitive advantage.
The proposal includes close collaboration with NXP, and direction and support from Imagination technologies, who represent two key beneficiary sectors of the UK economy. This level of interaction will maximise the research's applicability to the UK and worldwide commercial sector, whilst still allowing us the freedom to explore the intellectually interesting problems and deliver novel models and concepts to the academic community.

The research groups involved have track records in engaging the wider community, and will continue to do so during this project. Schemes such as media interaction and outreach will enable us to communicate our main discoveries to a diverse audience, disseminating formal and informal community knowledge, and ensuring that our discoveries reach as wide a potential user set as possible.

The project will employ two post-doctoral researchers and two members of academic staff. Over the course of the project, all will develop their knowledge and research, analytical and engineering skills. Combined with the university's formal staff training programmes, and the ability to inspire other individuals who encounter our research, we will make a contribution to the development of "people capital" in the high-tech sector. Finally, one of the post-doctoral researchers will spend time at the end of the project embedded in a partner company. They will use this time to identify contributions of commercial interest from the project deliverables, and organise a UK-wide workshop to disseminate this knowledge and spark wider interest from the commercial sector. We expect to gain new future partners and accelerate UK R&D efforts by this mechanism.