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Power Processing Unit (PPU) for the CubeSAT

Power Processing Unit (PPU) for the CubeSAT. Carlos Thayer David Xiao. Introduction. The PPU is designed to meet specifications to power the CubeSat propulsion system called the microcavity discharge (MCD) thrusters. http://cubesat.ece.illinois.edu/CubeSat_3D.html. Project Overview.

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Power Processing Unit (PPU) for the CubeSAT

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  1. Power Processing Unit (PPU) for the CubeSAT Carlos Thayer David Xiao

  2. Introduction • The PPU is designed to meet specifications to power the CubeSat propulsion system called the microcavity discharge (MCD) thrusters. http://cubesat.ece.illinois.edu/CubeSat_3D.html

  3. Project Overview • Design Specifications • Operating temperature: 0-50 deg. Celsius • Input Voltage: 12V • Output Voltage: 3kV p-p • Output Frequency: >1MHz • Output Power: 10 W • Efficiency: >90% • Weight: 30g ( 3g/watt) • Circuit Lifetime: >60h • Design Modules • Voltage Source Inverter (VSI) -Timers -Gate Drivers -Switches • Transformer

  4. Diagrams & Schematics Block Diagram VSI circuit with Timer (LM555) to Transformer

  5. Voltage Source Inverter (VSI) • Designed to convert 12 V DC input into a 12 V peak-to-peak AC output driven at 1 MHz • LM555 Timers • BJT Emitter Follower Pair • Complementary MOSFET Switches

  6. LM555 • 2 LM555 Timers -Astable -Monostable • Variable resistors allow duty cycle and frequency control • Astable circuit triggers monostable circuit • Timers drive BJT emitter follower pair

  7. LM555

  8. BJT Pair • Originally a BJT push-pull pair • Changed to NPN and PNP emitter followers with variable resistor between emitter and ground • Resistor allows for control of MOSFET switches by controlling current flow

  9. Transformer • Specifications • 1 MHz operation • 1:250 turns ratio • Ferrite Toroid Cores • 22 AWG windings • 36 AWG windings

  10. Transformer • Coilcraft CT1-Current Transformer

  11. Transformer • Primary: 36 AWG • Secondary: 36 AWG

  12. Transformer • Primary: 22 AWG • Secondary: 36 AWG

  13. PCB • Software: OrCad PCB Editor

  14. PCB (First Layout)

  15. PCB (Second Layout)

  16. PCB (Final Layout)

  17. Circuit Output

  18. Efficiency Tests

  19. Efficiency Tests

  20. Efficiency Tests • Average Efficiency: 34% • 0.48 W dissipated on gate driver

  21. Successes • VSI circuit can output 12 V peak-to-peak signal at 1 MHz • Noise in signal has been significantly reduced • Output can be stepped up with one transformer

  22. Challenges • Stability • Circuit startup • Efficiency • Transformer • Costs/Availability • Large turns ratio • Stacking Transformers

  23. Acknowledgements • Ariel Moctezuma • Professor Krein • YingyingKuai • Mark Smart and Dan Mast, Parts Shop

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