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Component Selection

Component Selection. By Prof. Bitar. Power Supply Example. Input: 120VAC / 60Hz (nominal) Output: 5V +/- 5% (4.5 to 5.5 V) 100mA (max). Possible Full-Wave Topologies (Assuming Linear Voltage Regulators). Typical Voltage Waveforms.

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Component Selection

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  1. Component Selection By Prof. Bitar

  2. Power Supply Example • Input: • 120VAC / 60Hz (nominal) • Output: • 5V +/- 5% (4.5 to 5.5 V) • 100mA (max)

  3. Possible Full-Wave Topologies(Assuming Linear Voltage Regulators)

  4. Typical Voltage Waveforms

  5. Begin Distributor Part Searchfor “Voltage Regulators”

  6. Yikes! Only 41,864 Possibilities… 41,864 Possibilities!

  7. Narrow the Search! In Stock !!! 6,241 Linear

  8. Further Search Criteria • Current (100mA) • Package / Case (TO-92 Thru-Hole!) • Packaging (for shipping) • Topology (Positive Fixed) • Voltage (5V)

  9. Down to Mfg & Pricing(Note Sorting Criteria) • Fairchild Semiconductor $0.32 • (More $, but better spec sheets & support.) • Micro Commercial Co: $0.20 • (Not as well supported, but CHEAP!)

  10. Selecting Part-Number Link Yields More Information Including Price Breaks! Finally a Data Sheet!

  11. Component Data Sheet • Absolute Maximum Ratings • (Not to be exceeded !!) • Input Voltage Max (30V) • Operating Temp (-20 to 120 C) • Storage Temp (-55 to 150 C) • Electrical Characteristics • (Under very specific test conditions!) • Output Voltage • (4.8 to 5.2 V @ T = 25 C) • Load Regulation (ΔVOUT / Δ ILOAD) • (60mV MAX from 1 to 100mA) • Line Regulation (ΔVOUT / Δ VIN) • (150mV MAX, Vin from 7 to 20V) • Quiescent Current (5.5mA MAX) • Output Noise Voltage (40uV TYPICAL) • Ripple Rejection (41dB MIN) • Dropout Voltage (1.7V TYPICAL)

  12. Q: Does this Voltage Regulator Meet our Specifications? YES! • OK, Repeat this Process for Every Component… • Power Transformer • Diodes • Filter Capacitors

  13. Selecting a Power Transformer • Questions: • What voltage do we need? • What is the maximum current? • What configurations do we need? • What configurations are available? Single or Dual Primary Single or Dual Secondary

  14. 1. What Voltage Do We Need? • Desired DC Output = 5V • Minimum Drop Across Regulator = 1.7V (spec) • Maximum Ripple Voltage = 1V (guess) • Drop Across Rectifier Diodes = 0.7 or 1.4V • Therefore, for C.T. Transformer: • Vpk = 5+1.7+1+0.7 = 8.4V = 5.9VRMS • Or for Full-Wave Bridge: • Vpk = 5+1.7+1+1.4 = 9.1V = 6.4VRMS • OK, Looking for 6.4VRMS @ 100mA (min)

  15. Parts Distributor Search

  16. Possible Choices Tamura 3FS212 : 6.3VAC, 180mA Transformer $3.75

  17. Transformer Spec Sheet

  18. Electrical Specifications

  19. Mechanical Specifications

  20. Hole Pattern Spacing

  21. Configuration Options

  22. Available Voltages / Currents

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