Education & Background

Doctor of Philosophy
in Electrical Engineering, November, 1990. 
Virginia Polytechnic Institute and State University, Blacksburg, Virginia.
Dissertation: A New Small-Signal Model for Current-Mode Control.

Master of Science in Electrical Engineering, January 1986.
Virginia Polytechnic Institute and State University, Blacksburg, Virginia.
Thesis: Investigation of Parallel Switching Power Supply Modules.

Bachelor of Science in Electrical Engineering, Summa Cum Laude, May 1981.Boston University, Boston, Massachusetts.Senior project: Investigation of Ferro-Resonant Power Supplies.

President, Ridley Engineering, Inc. April 1991 - present

Consulting to companies worldwide on power supply and power systems design at power levels from less than 1 W to over 100 kW. All levels of assistance to companies from full power system to development, in-depth design reviews, system analysis, and design conception. Specific projects have included:

Analysis and control design for 20 kW power system for computer servers with up to 480 VAC three phase input, power factor correction, phase-shifted bridge topologies. Development of innovative control scheme for wide-range input PFC circuit (180 VAC to 480 VAC).

Ruggedness and failure analysis of flyback converters for industrial applications. 
Analysis and modeling of multi-output converters for aerospace applications.Development of flyback and forward converters for utility and telecommunications applications, from concept to full production.

Teaching of unique hands-on design workshop over one thousand of engineers worldwide. This unique course, developed and taught exclusively by Dr. Ridley, incorporates his years of experience and design skills into an intense 4-day workshop where engineers learn how to be fast and effective power supply designers. Dr. Ridley's style of teaching cuts through all the confusion and mystery of power supply design, and his carefully designed labs are structured to train and educate engineers with all levels of experience.

Author of POWER 4-5-6 design and simulation software, the industry's most comprehensive tool for designing and analyzing switching power supplies. This software is the culmination of over 25 years' experience in developing power systems for industry, incorporating all of Dr. Ridley's insight in power converter design, control, and simulation. Many thousands of engineers use this software in their daily work for rapidly designing their switching power supplies.

Dr. Ridley is perhaps best-known in the industry for his landmark work on current-mode control which clarified exactly how the system should be analyzed for the best accuracy and practicality. This work has now been the standard for current mode analysis for over 20 years.

From 2000 to 2006, Dr. Ridley was publisher and editor of Switching Power Magazine, a unique industry publication distributed to over 10,000 engineers and power systems managers worldwide. Articles from this magazine are still available at

Dr. Ridley is a regular author of Design Tips for engineers in Power Systems Design Europe, Power Systems Design US, and Power Systems Design China.

Assistant Director, Virginia Power Electronics Center
Virginia Polytechnic Institute and State University, 1987 - April 1991.
VPEC is the largest university power electronics group in the world, with seven full-time faculty, thirty graduate students, and approximate funding of $2 million per year. It has recently been appointed an NSF research center.

Position responsibilities included:

  • Management of four power electronics research laboratories and
  • supervision of three research engineers
  • Performance of research on contracts
  • Design and teaching of power electronics courses for industry partners of VPEC
  • Generation of proposals for research contracts
  • Guidance of graduate students on research contracts for industry and government
  • Promotions, public relations, and interfacing with industry members of
  • VPEC's 40-member industry partnership program. This is the most successful program of its kind in this field with each member paying $10,000 per year to belong to the partnership

Specific research projects:

  • Design and analysis of power factor correction circuits for single-phase and three phase ac inputs, at up to 16 kW; Development of new small-signal models for single-phase units
  • Design and analysis of parallel power converters for computer mainframes
  • Development of new control systems and small-signal models for multiple converter power systems
  • Development of high-speed simulation and analysis software for piecewise-linear switched circuits
  • Development of computer-aided design tools for control-loop design for power converter circuits, and optimization for power circuits and magnetic components
  • Design of high-frequency, zero-voltage switching full-bridge converter, and design of zero-current-switched quasi-resonant converter for computer systems
  • Multi-loop control design of high-frequency multi-resonant power converters for on-board computer applications

Senior Engineer, Prime Computer, Framingham, Massachusetts.
October 1981 - August 1984. Power systems design projects included:

  • Design of multi-output high frequency switching power supply at 800 W
  • Design of instrumentation systems for analysis of switching power supplies
  • Investigation and analysis of power line disturbances on computer equipment
  • This included extensive testing and characterization of power line isolation units
  • Design of power distribution units
  • Small-signal analysis, measurement, and characterization of purchased power supplies
  • Design and development of software for small-signal analysis and large-signal simulation of switching power supplies



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