Simon Stringer

Power Conversion Ltd develops cutting edge power electronic converters, EV chargers, energy storage systems, PV converters, and power supplies, (ACDC, DCDC, DCAC, ACAC), using wide band gap technologies. We have significant experience in the consumer, motive and domestic markets.

During my time at Converter Technology, I have designed a precision ten-rail, digitally controlled power supply with point of load control, intended to power a high speed processing development board. Many of the rails are switched-mode and have a very low output ripple voltage of less than 10mV, and as low as 1mV, for output currents of up to 10A. I also designed the PCB layout, which is an 8-layer board - see picture. I designed the schematic and PCB layout for a high voltage, (400V to 300V DC), synchronous buck converter using recently developed SiC MOSFET modules for a university. During this project, I have reported on the expected power losses, (switching and steady-state), potential thermal issues, and the maximum expected throughput of the converter. Losses were determined by simulation in PLECS/Simulink.

As electrical/electronics lead, I designed and developed electronics controls and systems for hydrogen fuel cell products intended for the consumer electronics and automotive market. My main responsibilities were: • The design of electronic controls and systems. • Leading, mentoring and motivating Electrical/Electronic Engineers in my team. Enhancing their technical skills and developing them as Professional Engineers. • Conducting annual appraisals and performance reviews. • Interviewing potential candidates. • Delegating work packages and responsibilities to my team members according to their skill set with a view to personal and professional development. • Setting business objectives and personal development plans for my team. • Working with Programme Management in order to generate project timing plans and budgets. • Acting as a Design Authority – Reviewing/approving all documentation generated by the Electrical Engineering team. • To ensure that any designs will be compliant to relevant safety standards – Electrical and hydrogen safety. Includes meeting the EMCD, LVD and WEEED. • To ensure that all necessary supporting documentation is generated – Requirements and specification documents, circuit design calculations, FMEAs, thermal analysis, safety analysis, EMC and electrical test reports, design verification documentation, etc. • To ensure that proper design processes are adhered to, including product validation, verification and DFx. • Responsible for change control, bill of material management, and obsolescence. • A technical interface to Senior Management. • To work with Far-Eastern Contract Electronic Manufacturers.

I was responsible for the electronics hardware design and development of poly-phase electricity meters and acted as a design authority for several metering products. During my time at Elster Metering, I worked on reducing the field failure rate of precision poly-phase meters and also increasing the efficiency of an RS232/485 module’s isolated DCDC fly-back converter. I also worked on SMPS circuits which run from 240VAC, single phase and 400VAC, poly-phase supplies. I determined the root cause of significant measurement errors of the A1700i meter when subjected to high relative humidity environments and power supply problems with the A1100 meter. I was tasked with the root cause analysis of field failure returns. I have also generated a Siemens Life expectancy model based on the Siemens standard, SN-29500, for our latest smart-meter.

This role consisted of project management and electronics design. Responsibilities included: project management, developing specifications, generating timing plans and bills of materials, engineering change/design control, costing new designs, constructing and testing prototypes, electronics design and embedded systems software development, working with customers and approval bodies such as BSI and BEAB, managing technicians, dealing with production issues, product testing including the design of PC based automatic test equipment, DFMEAs, product verification/validation work and EMC testing/debugging. I was responsible for the electronics hardware design for the McLaren MP4-12C sports car instrument cluster. This is a complex system which has three dot matrix displays, two colour TFT displays, (similar size and performance to the Nintendo DS), an analogue engine speed indicator using a stepper motor, and an audio output. The interface to the cluster is via two CAN serial links. Overall control of the Instrument Cluster is achieved using a 16 bit micro-controller. The micro-controller interfaces to a dedicated graphics micro-controller using a 16 bit external data bus and serial data link. The graphics micro-controller runs linux and handles all of the TFT graphics and audio files and uses DDR2 memory. I have designed many boiler controls which are normally used in domestic central heating boilers and gas fires. Most of them are powered from the mains supply using capacitor dropper, (series impedance), supplies, switch mode or transformer based supplies, depending on the application. The environment in which these controls must operate in is quite harsh, as ambient temperatures can be as high as 85DegC combined with high relative humidities. These designs must fail safe with up to any two component failures. Therefore, two micro-controllers are used along with a fail safe gas valve drive circuit to ensure that the controls are safe.

After graduating, I worked for two years as an Electronic Engineer designing electronic control systems for high speed manufacturing/packaging machinery and custom built machines. I was responsible for product specifications, design, development, documentation, construction, testing and commissioning of various electrical systems.