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Dr. Stephen Watkins

Steve Watkins is the founder of the company and has 35 years industrial experience in power electronics and motion control. Most specifically in switched-mode power supplies, renewable inverters, brushless motor drives and multilevel power converter systems.

Industrial - Power Converters

After graduating from the University of Leeds in 1982, Steve worked in the switched-mode power supply industry as a design engineer for the next 6 years. Firstly at Farnell Instruments Ltd in Wetherby, Yorkshire and then at Advance Power Supplies Ltd in Bishop's Stortford, Hertfordshire. At Farnell's he worked on the hardware development of an automatic test system for various high-volume power supplies. This system was controlled by a Commodore PET and used GPIB to control the different elements of the ATE system. The key components developed for the ATE were a thyristor controlled transformer tap-changer for changing the input mains voltage, MOSFET-based electronic loads and a 30 MHz bandwidth peak-to-peak detector for output ripple and noise measurements.

Whilst at Farnells, Steve also undertook some research work to developed a resonant SMPS. This work resulted in a practical resonant flyback power supply which utilised the leakage inductance of the transformer and a separate parallel capacitor across the transformer. Although this work wasn't published at the time due to commercial confidentiality, it can be found in his MPhil thesis.

At Advance, Steve developed the low voltage DC input variant (PD500/PB350) of the popular Powerflex range (P500) of multiple output SMPS. The Powerflex SMPS was one of the first commercial zero-voltage switching transition power supplies on the market, which utilised magnetic amplifier secondary-side regulators. He also helped in the development of a 100 kHz MOSFET-based half-bridge SMPS, an early example of the commercialisation of MOSFETs in SMPS.

Over the last 20 years Steve has worked on various low power isolated multiple output SMPS for digital TV set-top boxes and mobile phone substation systems for Pace Microelectronics and Filtronic Comtek. Most recently he has undertaken work on prototype high switching frequency 'digital' power supplies using DSP control instead of conventional analogue PWM controllers. The most relevant power topologies include active front-end power factor correctors, zero-voltage transition (ZVT) full-bridge converters with synchronous rectification and synchronous buck DC-DC regulators.

Steve has also helped develop an inverter system for green power applications which meets international regulations for interfacing with the electricity grid. The inverter topology is basically a non-isolated high-frequency bridge DC/AC converter and uses DSP control to lock on to the grid voltage/frequency and regulate the supplied sinusoidal current without introducing significant harmonics. The DC source can be derived from renewable sources such as solar panels and wind turbines.

Industrial - Motor Drives

Steve joined Switched Reluctance Drives Ltd (now Nidec SR Drives) in 1988 and spent nearly nine years with the company, working on a wide variety of motor drive systems. He was the key investigator on a five year project to develop SR motor drive technology suitable for automotive applications. Of significance was his work on the power electronics and control of an SR generator aimed at replacing the existing alternator. This work included the development of a closed-loop control system for voltage regulation, based on his experience in SMPS, which allowed stable operation of the generator in the continuous current region at high speed. SR Drives have placed great importance in this application of SR machines as can be gauged by the numerous patents filed in recent years. Other contributions of significance commercially was the design of the first prototype drive system for Beckman Coulter Avanti® centrifuge and the simple control algorithm patent used in the AMETEK Lamb Infin-A-Tek vacuum cleaner.

Steve through FEL has provided patent information services on switched reluctance motor technology to a number of companies in industrial, white goods and automotive applications based in the UK, USA, Germany, Turkey and Japan. Most notably, this has contributed, in a modest way, the commercial development of an advanced 100,000 rpm vacuum cleaner motor drive by a world leader in white goods products.

In recent years Steve has added PM machine experience to his portfolio of knowledge through the design consultancy work undertaken by FEL. Both conventional BLDC and PMSM prototype drives have been developed using six-step and sinewave PWM control. He has also been involved, in collaboration with Aalborg University, on research & development on a novel single-phase hybrid permanent magnet reluctance drive system for low-cost applications which has great promise.

Industrial - Embedded Systems

Steve joined Pace Microelectronics in 1997 to work on some of the embedded software and hardware for the first digital TV set-top box to be launched in the UK by Sky. The product, now produced in the millions included Steve's user control micro design and software algorithms for synchronising the sound to the video via transport stream processor clock control. Steve has also worked in more recent years part-time at Filtronic Comtek on the microelectronics associated with mobile phone base-station equipment while he was studying for his PhD.

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