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Low Voltage Power for Future Microprocessor

Low Voltage Power for Future Microprocessor

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Low Voltage Power for Future Microprocessor

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  1. Low Voltage Power for Future Microprocessor Matt Niehaus Justin Fitzgerald

  2. DC-DC Power Supply for Future Microprocessors Specifications Input: +5V, +12V Output: 1V ±1% Power: 1-70Watts

  3. Why1V?Why70A? The Pentium III runs at 1.8V using 35.5WThe Pentium IV runs at 1.7V using 55WOur converter will output 1V with 70W

  4. Synchronous Buck Converter

  5. Why Synchronous? • Standard diode has 1Volt forward voltage drop. • Maximum 50% efficiency with a 1V forward drop diode.

  6. Multi-Phase Buck Converter

  7. Why Multi-Phase? • Less Current through each MOSFET. • Increase output frequency • Reduce ripple. • Reduce the size and cost of filtering elements.

  8. Gate Driver

  9. Master Clock Generates a Square Wave at the Output Frequency.

  10. Counter 74F163 Counter (Four bit binary counter)

  11. Decoder 74F139 decoder Takes the lowest two bits from the counter as the select inputs for the decoder. Outputs four 75% duty ratio signals 90 degrees out of phase.

  12. PWM Controllers UC3843 PWM Controllers takes compare input from feedback circuitry and compares to triangle wave created from the decoder output. Generates a square wave a duty ratio controlled by the compare input.

  13. Deadband Generator Insures that the synchronous FET fully turns off before the primary FET turns on and vice versa.

  14. Buck Converter Design

  15. Part Specifications • MOSFETs- Low RDSon • Diodes-Low Forward Voltage Drop • Inductors- High Saturation Current

  16. Output Filter Using L=1uH, the capacitor would need to be 20000uF for a single phase buck converter. With a four phase converter, the capacitance needed is reduced to 1250uF

  17. Input LC Filter • Due to switching the high current, the input power supply wasn’t able to maintain a steady voltage and current. • A series inductor was added to help control the input current. • A capacitor was added to each phase so that the MOSFET “saw” a voltage source.

  18. Turn Off Snubbers • Prevent immediate voltage change on turn off. • Helps reduce switching loss.

  19. Feedback

  20. Results

  21. Results

  22. Unresolved Issues • Excessive Ripple • Poor Efficiency • Reach Full Output

  23. Excessive Ripple • 1V ±10% output • Solutions • Shorten wires to reduce unwanted inductance • 6 phase buck converter

  24. Poor Efficiency • 50-60% efficiency • Solutions • Lower ESR Capacitors • Shorten wires to reduce unwanted resistance • Insure MOSFET ton is equal on all phases

  25. Reach Full Output • 30W output reached • Solutions • Fix Efficiency Problem

  26. Future Ideas • LTC1629 • Programmable Multi-Phase Synchronous Buck Controller • 6 Phases • Coupled Inductors

  27. LTC1629 • Multi-phase, high efficiency, synchronous buck switching regulator. • Controls up to 12 phase buck converter for circuits requiring up to 200A of output current.

  28. Six Phase Buck Converter Number of Phases ≥ Vin / Vout

  29. Coupled Inductor • Coupled Inductors allow easier attenuation of specific frequencies.