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ECE 345 - Senior Design Project

ECE 345 - Senior Design Project. A Better Uninterruptible Power Supply (UPS) Jason Fontaine Jon Rasmussen. Why a better UPS?. Simplification of AC/DC conversions Less conversions leads to higher efficiency Increased speed and reliability Direct input into a computer’s power supply.

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ECE 345 - Senior Design Project

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  1. ECE 345 - Senior Design Project A Better Uninterruptible Power Supply (UPS) Jason Fontaine Jon Rasmussen

  2. Why a better UPS? • Simplification of AC/DC conversions • Less conversions leads to higher efficiency • Increased speed and reliability • Direct input into a computer’s power supply

  3. How the design operates • Direct DC from UPS to power supply eliminates one DC/AC and one AC/DC conversion • Diode provides nearly instantaneous switching • Backup power always present behind diode

  4. System Diagram 120 V AC Source 10:1 Transformer Rectifier/ Battery Charger DC/DC (Flyback) Converter 12 V Battery 360 V DC output Diode DC Bus of PC Power Supply

  5. Rectifier/Charger • 12 V, 20 A battery • Similar to common motorcycle battery • Battery tolerant to input variations • Rectified signal can be rough • Charging time a non-issue • Battery under constant charging

  6. Rectifier/Charger Circuit

  7. Gate Drive • Using Pulse Width Modulation IC • UC 3843 PWM • Frequency Control • 10 kHZ - 500 kHZ • Duty Ratio Control • 0 % - 100%

  8. Gate Drive Circuit

  9. Why the Flyback Converter? • DC/DC Converters function like AC transformers • Can use single input to supply several different output voltages • Offer high degree of efficiency • Ability to create a larger “boost” • Turns ratio vs. duty ratio • Less demand for duty ratio accuracy • Does not require a common ground • Provides an isolated output

  10. Flyback Converter Circuit

  11. Project Specifications • AC Source Input Voltage: 120 V AC • DC Source Input Voltage: 12 V DC • DC Output Voltage: 326 V DC • Output Power: 240 Watts • Output Ripple: <5% • Input frequency: 50kHz • DC Source Input Current: 20 A DC • Output Current: 0.74 A DC • Converter Efficiency: >85%

  12. Expected cost parts $30 Expected cost time 140 hrs $8750 Grand total expected $8780 Actual cost parts $69 Actual cost time 144 hrs $9000 Grand total actual $9069 Cost and Time Analysis

  13. Project Conclusions • Performance • Achieved correct design • Circuit behavior acceptable (at low output power) • Budget • Reasonable end total • Must allocate research funds in future

  14. Post Project Conclusions • Ideal design well understood • Realized impact of non-ideal effects • Implementation far more difficult than anticipated • Learned value of design simulation

  15. Project Future • Resolve temperature effects • Reduce inductor size • Package the circuit, add interfaces • Direct tap into DC bus of PC power supply • Provide backup power for display

  16. Future for Project Team • Arkansas Valley Electric Co-op • Ozark, Arkansas • The RMH Group • Denver, Colorado

  17. Now we’re finished!!

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