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Efficient Lighting System for Rural Villages

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Rechargeable 12V lead-acid battery (supplied by the customer) Possibility of an over ... Aluminum Electrolytic: Low cost and high capacitance in a small package ... – PowerPoint PPT presentation

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Title: Efficient Lighting System for Rural Villages


1
Efficient Lighting System for Rural
Villages
  • Group 5
  • Kevin R. Cahill
  • Zaiai Chen
  • Mohammad R. Khan
  • ECE 445 Senior Design
  • December 1, 2005

2
Introduction
  • Incandescent bulbs emit 98 of their input power
    as heat and only 2 as visible light.
  • There are still many areas in the world with
    unreliable or no electrical infrastructure.
  • Kerosene/Gas lamps are a safety and health hazard
    to the user.
  • Emerging LED technology combined with power
    electronics provides an alternative.

3
Objectives
  • Achieve optimal converter efficiency to extend
    battery life
  • Compact/portable design
  • Low cost
  • Provide a quality of lighting comparable to
    incandescent bulbs

4
Design Process
  • System Overview
  • Circuit design
  • Performance Requirements

5
System Overview
  • Block Diagram

6
Source
  • Rechargeable 12V lead-acid battery (supplied by
    the customer)
  • Possibility of an over charged battery, circuit
    must handle up to 15V on the input

7
LEDs (Luxeon Emitter)
  • Highest flux per LED
  • 45 Lumens
  • Operating life up to 100k hours
  • Low voltage DC operation
  • Instant light (lt 100 ns)
  • Safe to touch

8
LEDs (Luxeon Emitter)
  • Steep VI curve requires a well regulated
    converter output

9
Lambertian Radiation Pattern for Luxeon Emitter
LED
10
DC-DC Buck Converter
  • Vout D1(Vin)
  • D1 MOSFET on-time

11
  • MOSFET
  • On-resistance must be low to reduce I2R loss
  • Logic-level gate drive
  • Diode
  • Must be a Schottky diode (quick on/off time)
  • Low forward voltage drop

12
Inductor Design
  • When selecting an inductor for a Buck converter,
    as with
  • all switching regulators, you will need to define
    or
  • calculate the following parameters
  • Maximum input voltage 15V
  • Output voltage 3V
  • Designed switching frequency 50kHz
  • Maximum ripple current
  • Cost/Size Penalty (Rule of thumb ?i 20 p-p)
  • Duty cycle
  • Result L100µH

13
  • Inductor design software
  • Calculates number of
  • coil turns based on
  • inductance, core size and
  • wire gauge

14
Output Filter Capacitor
  • Limits the output voltage ripple
  • Equivalent Series Resistance (ESR) should be kept
    low to reduce I2R loss
  • Aluminum Electrolytic Low cost and high
    capacitance in a small package
  • Design target ?v 0.1V
  • Calculated value 10µF

15
Simulations Waveforms
  • Verify hand calculations for output inductance
    and capacitance with PSpice simulations

16
Measured Voltage Ripple
17
Simulations Waveforms
  • In order to verify the overall design MatLab was
    used to simulate a PID Controller with a lossy
    Buck Converter
  • The PID Controller

18
Simulations Waveforms
  • Lossy Buck Converter

19
MatLab Results
20
Buck Converter Simulation Results
21
Control Circuit
  • UCC3803 Low-Power PWM control chip (TI)
  • Maximum Duty Cycle 100
  • Low Turn-Off Threshold Voltage 3.6V
  • Switching Frequency Up To 1MHz
  • Low Cost

22
Control Circuit
23
Control Circuit
  • UCC3803 PWM IC

24
PWM / Output Voltage
25
Buck Converter Control
Converter Output
Buck Converter
Battery Input
PWM IC
26
LED Array
27
Converter Efficiency
  • Good Efficiency
  • Longer battery life, smaller/lighter design (no
    heat sinks)
  • Conduction Losses
  • MOSFET on-resistance
  • ESR in the output capacitor
  • ESR in the inductor
  • Voltage drop across diode
  • Connection/solder points
  • Control Circuit Power Consumption
  • Switching Losses

28
Switching Frequency
  • Reduce Switching Losses
  • Ideal
  • Switch Open (VVin, I0A)
  • Switch Closed (V0V, IIin)
  • Instantaneous Switch Action
  • Actual
  • You can never achieve Ploss 0W

29
Switching Frequency
30
Efficiency vs. Vin
31
Output Regulation
32
Cost Analysis for Development
  • Labor
  • Member 3
  • Expected Salary 40 / hour
  • Work Per Week 10 hours
  • Length of Project 10 weeks
  • Labor 3 x (40 / hour) x 2.5 x 10 x 10 30,000

33
Cost Analysis for Development
  • Components Cost Quantity Total
  • LED 5.95 3 17.85
  • PWM 2.88 1 2.88
  • MOSFET 1.18 1 1.18
  • Diode 0.10 1 0.10
  • Resistor 0.42 1 0.42
  • Trimmers 1.73 2 3.46
  • Capacitor
  • (Ceramic) 0.15 3 0.45
  • (Electrolytic) 0.23 3 0.69
  • Inductor 2.73 1 2.73
  • Proto-Board 1.99 1 1.99
  • Connector 0.04 3 0.13
  • Total 31.18
  • Total Cost Labor Parts 30,031.18

34
Cost Analysis for Production
  • Components Unit Cost _at_ 1000
    Quantity Total
  • LED 5.95 3 17.85
  • PWM 1.63 1.63
  • MOSFET 0.46 1 0.46
  • Diode 0.08 1 0.08
  • Resistor 0.28 1 0.28
  • Trimmers 0.96 2 1.92
  • Capacitor
  • (Ceramic) 0.05 3 0.15
  • (Electrolytic) 0.08 3 0.23
  • Inductor 0.98 1 0.98
  • PCB 2.52 2.52
  • MTA Connector 0.04 3 0.11
  • Total 25.93
  • Total Cost Labor Parts 30,025.93

35
Thank You
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