Quietening ultra-low-loss SiC & GaN waveforms

Lead Research Organisation: University of Bristol
Department Name: Electrical and Electronic Engineering

Abstract

Power electronics reduces our carbon footprint and contributes nearly £50bn per year to the UK economy and supports 82,000 skilled jobs in over 400 UK-based companies. Power electronic converters regulate the flow of power in most electrical devices, in electric vehicles etc. They do so by switching currents on and off, 10s of thousands of times per second, and the ratio of on-time to off-time determines the power flow. The efficiency, size, and weight of these converters are determined by the amount of waste heat generated. For example, the size of laptop power adapters has shrunk over the years, due to their increase in efficiency. In an electric car, waste heat causes power converters to be typically larger than the motors they are feeding. This heat is mostly produced in the instances when the transistors are switching.

The power electronics industry is about to undergo significant change, as ultra-fast-transition transistors made from silicon carbide (SiC) or gallium nitride (GaN) have recently emerged. Their switching transitions are so short (below 10 nanoseconds) that, in principle, efficiency can be pushed to levels never achieved before. This could lead to a ten-fold miniaturisation, leading to converters that are much smaller than the motor being driven, or credit-card-sized laptop power adapters.

The fast switching, however, comes with the downside of extreme electromagnetic noise, and industry is struggling to adopt these new technologies. Our project will provide answers to key uncertainties for adoption of these new technologies, namely how to drive the SiC and GaN power devices quickly, safely and quietly.

The electromagnetic noise (EMI) is seen on an oscilloscope as sharp corners, rapid oscillations, and overshoot spikes, during the switching transitions.
In this project, we are developing solutions to achieve clean switching, without these undesirable features, to quieten the EMI. These features are countered by feeding specially-shaped signals into the transistors' gates.
The switching transition is too fast for any known signal generators and closed-loop control methods, or passive switching-aid (filtering) circuits to provide the required shaping of gate signals. Therefore, an alternative approach is adopted.

We recently developed a chip that can adjust its current output every 100 picoseconds, i.e. the time it takes light to travel 3 cm. It is the only known driver chip that can interact frequently enough with a gate signal to shape these short sub-10 nanosecond switching transitions. We will create improved versions of this driver to drive gallium nitride and silicon carbide transistor gates with signals that are designed to soften the switching and cancel out unwanted high-frequency effects. The signals need to be changed automatically as the converter temperature changes, and when changes to its output power are requested. Also, each type of circuit requires slightly different signals. Therefore, automatic adaptation will be developed to simplify the use of this technology by industry. An interesting challenge is the safe generation of optimised gate signals, as the wrong signal can cause a power converter to fail. Another challenge is the regeneration of energy put into the gate, so that it can be used for the next switching event.

The project develops microelectronics (high-speed, EMI-quietening gate drivers) and power electronics (converters and control systems). Industry advisors from 8 partner companies will steer the development for three years. In Year 4, the research is scaled down, and trials in UK-based industry set up to transfer knowhow, test the research, and provide new avenues for fundamental research.

This research will help maintain the compatibility between emerging high-efficiency power electronics and modern ultra-low-power microelectronics that is increasingly susceptible to electromagnetic noise, and simplify and expedite industry adoption of SiC & GaN.

Planned Impact

We aim to enable the UK to gain a competitive advantage by successful early deployment of recently emerged SiC and GaN power conversion devices. The impact of this project can be summarised as follows:

Economy and UK companies:
1. Significant miniaturisation of power technology, helping UK industry reduce size, weight, and power of products and systems.

2. Improved knowledge for utilisation of GaN & SiC devices, resulting in lowering costs by avoiding expensive EMI mitigation, and in speeding up time to market.

3. Access to state-of-the-art facilities and knowledge.

4. Increased market demand as power electronic system capability increases.

5. UK to maintain its position as a major player in GaN & SiC power electronics.

6. Increased IP residing in the UK.

7. Attract high-value activities such in areas of electric vehicles, robotics, consumer products, and renewables, to the UK.

Society:
1. Reduced greenhouse emissions and enhanced opportunity for meeting future targets (CO2 reduction 2020 and 2050 goals) through more efficient power conversion, miniaturisation of electrical systems in electric vehicles, and adoption of renewables through use of smart grid technologies.

2. Cleaner urban environment due to enhanced impact of clean transportation (electric/hybrid vehicles, rail, 'more electric' aircraft systems, ship propulsion).

3. Skilled young researchers and PhD students helping to address skill shortage.

4. Improved knowledge of industry engineers.

Publications

10 25 50
 
Description This 4-year award is now in its 4th year. Also, we have been given more time to complete our results due to Covid which shut down our laboratories.

In terms of helping industry:

We have organised discussions and workshops with around 20 power electronics companies (UK companies, and global corporations with a UK R&D base). This has helped senior engineers discuss best practice and explain to us what hurdles they face when adopting the latest, most efficient electronic components. We are able to carry out high-risk investigations to help with these problems. It would not be efficient if this were done in each company. Also, we have acquired a number of specialist skills whilst pushing devices to their limits, in areas that are important to industry, such as in high-bandwidth instrumentation and measurement skills, or in designing high-speed printed circuit board layouts. We know that our findings have had an impact since 3 UK-based companies have funded the Bristol and Edinburgh teams to carry out this type of work on their own internal projects, and Imperial have received investment to turn their work into a start-up company. Companies tell us their needs and we are then able to tailor workshops to these needs.

From a scientific perspective:

We have learned what is necessary to be able to create power electronics that automatically adapts its gate driving signals to reduce electromagnetic emissions whilst increasing power efficiency.

We have created new measurement techniques to help industry work on SiC and GaN.

We are working towards energy recycling in power electronic circuits, and adaptive gate driving to quieten converters.
have been captured and key application constraints have been identified, in part due to the holding of two industry workshops.

We have managed to reduce the cost and size of the underpinning gate driving technology so that the equipment can more easily be transferred to all partners, and used in radiated emissions test facilities.

We have discovered new driving techniques for SiC power devices, and built a test rig to refine these.

We have ported our world-leading active gate driving technology to SiC, which meant finding ways of maintaining its record-breading speed, but raising the voltage by 6x. This new chip is now working at it is being investigated if it can help make electric vehicles more efficient and lighter.

We applied for a patent on generating driving profiles for power semiconductor devices in systems where the operating conditions such as temperature and torque change (as is the case in most electrical drives), but then abandoned this as the duration between filing and it becoming adopted by industry was probably going to be many years, and we would not have had the funds to maintain the patent until then.
Exploitation Route The main outcomes have been published and are most likely contributing to a trend towards the sophisticated gate driving techniques being adopted by the automotive industry. Automotive companies have approached us for collaborative work to apply our findings in electric vehicles. We are also making the sensors available that we designed during this project. Finally, we helping UK-based companies by applying some of the peripheral findings of this project, for example by helping design high power converters for wind turbines. We would like to take the research further to create sensors for a much broader range of electronic sensing and control. We submitted a grant proposal on this to EPSRC but it came 5th out of 39 entries and just didn't make the cut since the success rates are currently only around 14%. We will also try to research into automated active gate driving funded, and failing that, help other organisations continue this research while we move onto other topics. A break in funding typically results in researchers leaving, requiring a fresh start once funding is successfully obtained.
Sectors Aerospace, Defence and Marine,Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Security and Diplomacy,Transport

 
Description Asking companies what types of findings they actually need ******************************************************************** We organised and hosted two full-day technical workshops. For the first, we arranged for Engineering Directors, CTOs, and Chief Engineers of around 20 UK-based power electronics companies to present their needs and challenges in this area. Academics from 5 universities listened in and asked questions, and used this to align their research with the difficulties that companies are experiencing when moving to new power electronic technologies. For example, one of these challenges was how to measure signals in the products given that modern faster switches create faster waveforms and more electromagnetic interference. In the second, we invited more companies, and presented the state of the art in some of the problem areas we had identified in the first workshop. For example, we put on a seminar on advanced measurement techniques. We provided a platform for these companies to discuss the challenges, which helped everyone share good practice, and which helped the academics better target their research at the most urgent and important challenges. Transfer of findings to UK-based companies ************************************************** We publish many of our findings, but in addition, in this project, we have been able to work on joint projects with companies. For example, we had a designer shadow our researchers for a week while they worked on a design for a company, which allowed this designer to carry on in this line of work at the company, with new-found skills. Using our findings to help companies develop new products ******************************************************************** We have applied our findings when helping companies with their own products. This includes helping them apply measurement methods that we have developed, and how to lay out fast-switching power electronic designs that use the latest SiC and GaN power devices. We show them how to keep waveforms from becoming noisy which would cause products to fail EMC certification. This helps the companies keep up with the latest technologies, for example to help them reduce the size and weight of power products. We have also been told by industry contacts that our insights into active gate driving are very likely being adopted in the automotive industry, however this would be hard for us to verify. We are currently helping a UK automotive manufacturer in this area. Providing new technology that contains our findings to companies *************************************************************************** We offer gate driver chips for experimentation and sensors. We have provided over 50 companies and organisations with free sensor samples. Although it takes quite a bit of skill and high-end equipment to design our sensors, we sampled devices to companies for free, until we had iterated the design to the point where it is a world-leading sensor. Now we are charging a handling fee, and distributing them via the website infinitysensor.com. Some companies have told us they are building them into their own products. Creating new companies and jobs based on our findings **************************************************************** We, or specifically the Imperial-based researchers on this project, have spun out a company called Bumblebee, which uses the highly efficient, high-frequency GaN and SiC power electronics developed in this project. The company has received investment and is employing full-time engineers. Combining our findings with international research to make it go further ********************************************************************************* The driver chips developed in this project were 3rd party validated by a university in Germany who have an automotive testing facility, which led to interesting joint research and benefits to both sides.
First Year Of Impact 2017
Sector Aerospace, Defence and Marine,Education,Electronics,Energy,Transport
 
Description £10k EPSRC impact acceleration funding for Strathclyde
Amount £10,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 09/2020 
 
Description EPSRC IAA PIV010 HCASiC Finney SGRE, £66,414,
Amount £66,414 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 07/2020 
End 03/2021
 
Description University of Strathclyde EPSRC Impact Acceleration Account: 'Performance Comparison of Si and SiC Power Semiconductor Devices in Switched Reluctance Machine Drives', £19,725 including £10,000 in-kind contribution from Technelec Ltd.
Amount £9,725 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 08/2020 
End 06/2021
 
Description Collaboration with Siemens Gamesa Renewable Energy Limited 
Organisation Siemens Gamesa Renewable Energy
Country Spain 
Sector Private 
PI Contribution Development of proposal for industrial R&D in the field of wind turbine interfaces. ( Details Confidential)
Collaborator Contribution Technical input and to PhD student projects and guest lectures to MSc class. Participation in Quietening ultra-low-loss SiC & GaN waveforms industry workshops and contribution to QW reserach. Funding for PhD and lab hardware approx £120k
Impact 2-Level Si IGBT Converter with Parallel Part-Rated SiC Converter Providing Partial Power Transfer and Active Filtering Paul D. Judge ; Stephen Finney 2019 20th Workshop on Control and Modeling for Power Electronics (COMPEL) Year: 2019 | Conference Paper
Start Year 2017
 
Description Design collaboration with Nidec Control Techniques 
Organisation Control Techniques Drives Ltd
Country United Kingdom 
Sector Private 
PI Contribution Two contracts for a co-design collaboration between Nidec Control Techniques and the University have been carried out.
Collaborator Contribution There was a financial contribution (confidential), and exchange of valuable expertise.
Impact Outcomes Knowledge and design expertise transferred to company. Application and product design expertise transferred to university. Research and development roadmap of the company has been influenced.
Start Year 2019
 
Description Design collaboration with Toshiba Bristol Research and Innovation Lab 
Organisation Toshiba Research Europe Ltd
Country United Kingdom 
Sector Private 
PI Contribution The University of Bristol provides training and prototyping facilities, and design expertise.
Collaborator Contribution Toshiba have contributed financially, and provided semiconductor design and application expertise.
Impact Too soon to tell.
Start Year 2019
 
Description Membership of CSA-Catapult Power Electronics Industrial Steering Group 
Organisation Compound Semiconductor Applications Catapult
Country United Kingdom 
Sector Private 
PI Contribution Contribution to CSA strategy through membership of the CSA-Catapult Power Electronics Industrial Steering Group that will help guide the direction of CSA-Catapult research supply chain support, including Evaluation Module (EVM) roadmap and specification development.
Collaborator Contribution Hosting of wide band gap power semiconductor workshops and networking events
Impact None
Start Year 2019
 
Description PhD funded by Toshiba BRIL 
Organisation Transport Research Laboratory Ltd (TRL)
Country United Kingdom 
Sector Private 
PI Contribution This section is not phrased well at all. What comes directly to my research is a fraction of what is paid to the company. This is extreme in the case of a PhD, where a company would fund the overseas fees, the stipend, a stipend enhancement, but zero pounds come into our lab. We spend time helping the researcher, and if they are very good then they produce something that offsets the time we spend training them.
Collaborator Contribution Financial and monitoring.
Impact This has only just begun.
Start Year 2018
 
Company Name BUMBLEBEE POWER LTD 
Description The Imperial-based researchers on this project, have spun out a company called Bumblebee, which uses the highly efficient, high-frequency GaN and SiC power electronics developed in this project. The company has received £750,000 of seed investment and is employing full-time engineers. 
Year Established 2018 
Impact The company is in its early days. Impact will be updated as it arises.
Website https://www.bumblebeepower.com/home
 
Description Chairing Special Session on Advanced Measurement Techniques in Power Electronics at PCIM'22 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact PI was invited to chair the Special Session on "Advanced Measurement Techniques in Power Electronics" at PCIM'22. In-person and online audiences, and permanent videos, so large reach.
Year(s) Of Engagement Activity 2022
 
Description Chairing Technical Programme Committee of Wireless Power Week 2022 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Prof Mitcheson is TPC chair of Wireless Power Week 2022
Year(s) Of Engagement Activity 2022
 
Description Invited talk at University of Utah 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The Imperial group gave an invited talk at University of Utah in Feb 2022.
Year(s) Of Engagement Activity 2022
 
Description Membership of Steering Committee of Wireless Power Week 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Prof Mitcheson is on the new steering committee of wireless power week.
Year(s) Of Engagement Activity 2022
 
Description Organised a 3-day Design for Electromagnetic Compatibility Course for 20 participants in 2019 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Study participants or study members
Results and Impact The Universities of Edinburgh and Bristol organised a course for all project members in Bristol, with an open invitation to wider research group members.
The course was led by an internationally renowned EMC expert.
Year(s) Of Engagement Activity 2019
 
Description Organised a high-speed printed circuit board design workshop 2019 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Study participants or study members
Results and Impact A one-day workshop organised by University of Bristol, and hosted at the University of Strathclyde, to advance the skills of project
researchers, in the area of PCB design, using Altium for schematic capture, and producing circuit layouts.
May 13, 2019.
Year(s) Of Engagement Activity 2019
 
Description Quietening Waveforms Technical Workshop 2019 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Technical Workshop 1: Challenges of adopting SiC and GaN
*********************************************************************
Engineering Directors, Chief Engineers, Managing Directors, and other senior decision makers from 11 Power Electronics companies (global corporations with a strong UK presence, or UK companies) made 5 minute presentations on their technical and commercial challenges of adopting new power semiconductor technologies. Each presentation was followed by 20-40 minutes of discussion amongst the companies and research groups present.

The outcomes of the workshop were:
- Increased common understanding of the technical and commercial hurdles facing the UK power electronics industry.
- Increased understanding of the application domain of power electronics research, and the future needs of industry.
- Increased mutual understanding between industry and academic research groups.
- Increased ability for research groups to create productive roadmaps for their research, and to gain collaboration partners.

A follow-up workshop was requested and duly offered.
Year(s) Of Engagement Activity 2019
 
Description Quietening Waveforms Technical Workshop 2020 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Engineering Directors, Chief Engineers, and other senior decision makers from 10 Power Electronics companies (global corporations with a strong UK presence, or UK companies) took part in an interactive workshop with 4 sessions. The first, on high-bandwidth measurement of high-performance power electronics had been requested at the previous workshop. The other sessions opened up research questions faced by the research groups at Imperial, Edinburgh, Strathclyde, and Bristol. The sessions contained on average 5 questions, and industry and academia discussed possible methods and pitfalls for about 2/3 of the time.
The workshop was ended with a discussion on how universities can enhance their support of industry with courses, knowledge exchange and other types of interaction. The attendees requested a follow-up workshop, and a course for graduate engineers. Two representatives from EPSRC were present at the workshop.

Outcomes:
This workshop furthered the common understanding between industry and university research groups, and led to new relationships between engineers and researchers.
The Quietening Waveforms project benefited from the wealth of experience of the industry attendees, who were very active and forthcoming with advice and ideas. Generally everyone felt they had learned new things, and were supportive of continuing this workshop series in the same discussion-based format. The EPSRC reps commented on the collaborative nature and openness of discussion of this event.
Year(s) Of Engagement Activity 2020