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EE 136 Final Presentation

EE 136 Final Presentation. Professor Dr. Zhou Presented by: Cynthia David. Agenda. Part 1, Chapter 22 Centering of Auxiliary Output Voltages on Multiple-Output Converters. Part 1, Chapter 23 Auxiliary Supply Systems Part 1, Chapter 24 Operation of Voltage-Stabilized Power Supplies.

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EE 136 Final Presentation

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  1. EE 136 Final Presentation Professor Dr. Zhou Presented by: Cynthia David

  2. Agenda • Part 1, Chapter 22 • Centering of Auxiliary Output Voltages on Multiple-Output Converters. • Part 1, Chapter 23 • Auxiliary Supply Systems • Part 1, Chapter 24 • Operation of Voltage-Stabilized Power Supplies

  3. Centering Auxiliary Output Voltages on Multiple-Output Converters • Problem • Obtaining an absolute output voltage value. • Solution • Saturable reactors – small toroids • Used to control voltage and current control. • Provides pulse width / timing techniques

  4. Centering Auxiliary Output Voltages on Multiple-Output Converters • Saturable Reactors • with a forward converter . Vout = Vs × ton / ( ton + toff ) from Chapter 21 Part 1 • Example Given Vout = +12, -12, +5 Desire: 11.5 turns use 12 Higher Output Voltage is given ie. 12.7 ton = 15 µs toff = 18 µs

  5. Centering Auxiliary Output Voltages on Multiple-Output Converters • Saturable Reactors • td = ton – required V × ton / (actual Vout ) = 15 - (12*15) / (12.7) = .827 µs td is delay time, ton is on cycle, • Vs = Vout ( ton + toff) / ton = 27.9 V . • td = Np × ∆B × Ae / (Vs) Np is the primary turns, ∆B difference in remanance flux from flux density saturation. Ae is the effective area of the core. Given ∆B = .4 • Ae = Vs × td / ( Np × ∆B ) assume Np = 1.

  6. Centering Auxiliary Output Voltages on Multiple-Output Converters • Saturable Reactors • Ae = Vs × td / ( Np × ∆B ) assume Np = 1. = 27.9*.827 µs / (1 * .4) = 57.7 mm^2

  7. Centering Auxiliary Output Voltages on Multiple-Output Converters • Applications • large industrial furnaces, welders and high-power voltage regulators. • Important Concept • Depending on application, with saturable reactors, decide to alter the area or number of turn ratios to produce Vout.

  8. Auxiliary Supply Systems • Auxiliary Supply Systems • Provide power for control • Drive circuits within the main switch-mode unit. • Need to be common to input and output lines. • Safety factors must be given • Creepage distance, isolation requirements • Auxiliary supply methods must be considered

  9. Auxiliary Supply Systems • Various auxiliary supply units • 60 Hz Line Transformers • Energized before the main converter, allows power available to the main switching mode. • Meets insulation and creepage requirements. • Disadvantage: size & cost

  10. Auxiliary Supply Systems • Auxiliary Converters • Two auxiliary power supplies from high frequency flyback converters. + More efficient because energy Is returnted to the supply during Flyback period.

  11. Auxiliary Supply Systems • Stabilized Auxiliary Converters • Modifications Zener Diode,Q2, winding P3 • Maintains constant frequency + Maintains constant frequency. Can Be used as a clock.

  12. Auxiliary Supply Systems • High-efficiency auxiliary supply. • Includes a bridge rectifier supply the converter & fan application + Most efficient supply system + Useful in 110-220V applications

  13. Parallel Operation of Voltage-Stabilized Power Supplies • Voltage Stabilized Power Supplies • connected in parallel with high voltages • usually have small output resistances • big difference in current load! • desire equal distribution in current • may cause output power supply to be overloaded! Domino Effect!

  14. Parallel Operation of Voltage-Stabilized Power Supplies • Configurations of Power Supplies • Master Slave Operation • Master controls the parallel supplies. P-terminal and Transistor 3 control current KEY POINTS + Similar output current - 20% Accurate - Limited to the number of supplies - If Master Fails, other units follow

  15. Parallel Operation of Voltage-Stabilized Power Supplies • Configurations of Power Supplies • Voltage – Controlled Current Source • P terminal link adjust for output voltage, R1 and R2 sense output current. KEY POINTS + More accurate output current - Less percent of failure

  16. Parallel Operation of Voltage-Stabilized Power Supplies • Configurations of Power Supplies • Force Current Sharing • Compares Vref and V from R3 and R4 to maintain constant Voutput. • A2 compares the currents and Rx alternates alters V2 and Vout. KEY POINTS + More accurate output current + Failure to one does not affect others. + Redistribute load if others fail. + Output voltage adjust itself to the average value of the independent units.

  17. Parallel Operation of Voltage-Stabilized Power Supplies • Configurations of Power Supplies • Parallel Redundant Operation • Ensures maintenance of power in case supply fails. • Diodes senses differences in Voutput. KEY POINTS + Failure to one does not affect others. + Redistribute load if others fail

  18. Conclusion • Review • Centering of Auxiliary Output Voltages on Multiple-Output Converters • Auxiliary Supply Systems • Parallel Operation of Voltage Stabilized Power Supplies.

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