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The Design Process Applying Value Analysis to Determine an Optimum Solution

This article explores the design process for determining the best solution for a window candle. It covers research, brainstorming, value analysis, applying constraints, and the preferred solution. It also provides information on relevant components and manufacturers.

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The Design Process Applying Value Analysis to Determine an Optimum Solution

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  1. The Design ProcessApplying Value Analysis to Determine an Optimum Solution by Prof. Bitar

  2. Abstraction & SynthesisHomework #2 Research Prior Art Brainstorm Possible Solutions HW#2 Abstraction & Synthesis Perform Value Analysis Viable Options Apply Constraints Preferred Solution

  3. Window Candle Block Diagram with Two Defined Blocks Photo Sensor Solar Cell Charge Controller Rechargeable Battery 1.2V NiCd DC-DC Boost Converter LED 3.2V 20mA Mode Selection Flickering Control

  4. Agilent White LED Spec. Sheet

  5. LED Specifications – Curves !Max. Forward Current vs. Voltage Check: 20mA @ 3.2V (Typical)

  6. Battery Specifications

  7. Battery SpecificationDischarge Curve

  8. DC-DC Boost ConverterInterface Specs • INPUT: 1.2V(Nominal) • Minimum ? (0.8V) • Maximum ? (1.6V) • OUTPUT: 20mA (constant current?) • 3.2V (Nominal for White) • 1.7V (Nominal for Red)

  9. Searching for Possible Boost Converters… • www.digikey.com • DC-DC Converters (4,561 IN STOCK!) • Narrowing Search (down to 47) • Step-Up (Boost) • Vmin ≤ 0.8V (why?) • Internal Switch • Number of Outputs (1) • Small Qty. Packaging (cut tape / tube) • Case…

  10. Package/Case Concerns… • For prototypes, through-hole packages (8-DIP, 16-Dip, etc.) are easiest to work with. • If chip is only available in surface-mount, avoid DFN, QFN, LLP and BGA packages since pins are underneath. • For surface-mount ic’s, try to get largest packages possible with gull-wing pins.

  11. Possible Manufacturers

  12. Also Ran Across Another Device!LED Driver IC’s… • www.digikey.com • LED Drivers (1,319 IN STOCK!) • Narrowing Search (down to 47) • Step-Up (Boost) • Vmin ≤ 0.8V (why?) • Internal Switch • Number of Outputs (1) • Small Qty. Packaging (cut tape / tube) • Case…avoid DFN, QFN, LLP, BGA

  13. Possible LED Drivers

  14. IC’s Making the First Cut(Just based on PRICE!)

  15. National - LM2623

  16. Typical Application Circuit(Constant Voltage Output)

  17. Note External Components… • Inductor • Capacitor(s) • Schottky Diode • Resistive Divider

  18. ST - L6920DB

  19. Typical Application Circuit(Note Fewer External Components!)

  20. Diodes/Zetex - ZXLD383ET5CT

  21. Typical Application Circuit

  22. Leaning Toward the Diodes/Zetex LED Driver • http://www.diodes.com/datasheets/ZXLD383.pdf • Pro’s • Price • Ease of Use (Few External Components) • Designed for My Application • Con’s • Single Manufacturer (Not Multiple Source!)

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