Some Reflections on the Field of Power Electronics and Control of DC-DC Converters

1. Some Reflections on the Field of Power Electronics and Control of DC-DC Converters Trey Burns October 1, 2012

2. Presentation Overview • Introduction - A Brief Look Back • An Unconventional Approach to Control • Conclusion – A Brief Look Forward

3. Evolution of Power Electronics • Switching Converters Have a Long History • “The Parallel Inverter”, F. Tompkins, 1932 • Power Semiconductor Switches are Key Enablers • Bipolar Transistors and SCRs Introduced in the 1950s • Power MOSFETs Became Dominant in the 1980s • Wilson and Moore Codified Fundamentals in “Basic Considerations for DC-DC Conversion Networks”, 1966

4. Some Key Power Electronics Milestones • Silicon General Introduced the SG1524 PWM IC, 1976 • Middlebrook and Cuk offered “A General Unified Approach to Modeling Switching Converter Power Stages”, 1976 • IR Introduced the HEXFET, 1979

5. Evolution of Power Electronics – The Process Circuit Optimization Improved Components • Fundamentals Are Well Understood • Circuits Are Optimized Around Components and Applications

6. Evolution of Power Electronics • Past Examples of the Process • Bipolar Transistors Proportional Base Drive • FETs Higher Frequency Switching Converters • Low RDSon FETs Synchronous Rectification • Synchronous Rectification Higher Efficiency Converters • The Process Continues – Digital Technology • Enables more Flexibility • Enables more Intelligent Control

7. Semiconductor Enablers Power Switches Thyratrons & Ignitrons Bipolar Transistors Silicon Carbide GaN FETs Controllers Programmable & Application Specific Digital ICs Discrete Analog Components Analog ICs

8. The Control Challenge

9. Go Inside The Control Booth I can see only Vo!

10. Go Inside The Control Booth ix I want to be here. How do I get here? I need to see more than Vo! Vo/R vc Vo (<V)

11. Laws of Physics Determine How We Move Through the State Plane

12. Close the Switch and Move from (0,0) to (V,V/R)

15. Open the Switch and Move from (V,V/R) to (0,0)

20. Three Possible Conditions for the Buck Converter

25. (These Are Off Trajectories)

26. Large Inductor – Less Δ ix Small Inductor – Discontinuous Mode

27. Heavy Load Light Load

28. Shapes of Trajectories • Dependent on Power Stage Component Values • L, C • Parasitic Elements (ESR, Vd, …) • Dependent on Operating Conditions • Input Voltage • Load

30. Unique Steady-State Solution = f(L, C, Vin, Io, Vo, T) This is where we want to be!

31. How Should I Control the Switches to Get There?

32. Establish a Switching Boundary We can now see how to get there from anywhere!

33. Transient Response Not Constrained by Fixed Ton, Toff or T But Steady State Response Reverts Back to Fixed Ton, Toff or T

35. Heavy Load Nominal Load Light Load

36. Higher Frequency Lower Frequency

37. Trajectory Shapes Changed When the Load Changed

38. State Trajectory ControlApplied to Boost Converters Target voltage “Off-Trajectory” “On-Trajectory” Steady state trajectory Off trajectories converge to 60V, 15A point, because this is the value of the input voltage and the load Starting point Different Trajectories, Same Principles

39. State Trajectory Control • Incorporate All System Information • Component Values • Line and Load Operating Conditions • Observe System Behavior • Determine where you are vs. • Where you want to be • Make Switching Decisions Accordingly • Take advantage of all information available and do not constrain switching decisions unnecessarily

40. Opportunities for Innovation in Power Electronics • Architectures • Evolve to Meet System Requirements • Example – Factorized Power from Vicor • Circuits • Build on Fundamental Principles • Optimization for Applications • Components • Strive for Ideal Behavior • Energy Storage as well as Switching and Control

41. Opportunities for Innovation in Power Electronics • Materials • Thermal Interfaces • Power System in Package • Design Tools • Enable Complex Physical Relationships & Dependencies • Faster Product Development Cycle Times • Manufacturing Tools • More Precision Smaller Components • Better Control of Processes Higher Yields, Improved Quality • Higher Levels of Integration

42. Technology Enablers • Semiconductor Switches • Higher Frequency, Clean Switching Transitions • Lower On Resistance • High Frequency, Low Loss Ferrite Materials • Higher Energy Density Capacitors • Higher Levels of Integration • Monolithic Switching Regulators (e.g., Volterra) • Power System on Silicon (e.g., Enpirion) • Advanced Manufacturing Processes • Digital Control Technology

43. Digital Power Conversion • Digital Controllers Are Being Marketed Today • Some Application Specific • Some Programmable • Digital Controllers Enable • Intelligent Nonlinear Algorithms • Stable Operation Over Temperature • Improved Noise Immunity • Adaptive Control Algorithms

44. Digital Power Conversion – An Opportunity • PLDs and FPGAs as Controllers • Power System Designers Avoid the Time and Cost of ASIC Development • Faster than Micro-Controllers • Power Supply Makers Retain Proprietary IP • Product Ideas Can Be Developed & Verified Quickly

45. Final Note: When approaching difficult nonlinear problems, you may need more than one approach to reach a solution.

46. Thank You for Your Attention