Transcript Session Title

Introduction to Prototyping
a LED Driver
Part I: Driver Design and
Component Selection
September 24-28, 2012
Carol Lenk
PCB Prototyping Process
Design
Schematic Capture
Layout
Manufacturing
(Gerber) Files
PCB-top copper.gbr
PCB-top mask.gbr
PCB-top silkscreen.gbr
PCB-bottom copper.gbr
PCB-drill data.drl
Bill of Materials (BOM)
PCB Layout Software
Layout Software Options
• Low Cost – Eagle
– $69, 2-layer PCB, 100mmx80mm
– Steep learning curve, uses scripts.
• PCB Manufacturer Provided – PCB Artist
– Can’t import or export, must order from 4pcb.com.
– Can get gerbers after one PCB order.
• Freeware – DesignSpark
– Functionally similar to PCB Artist, but can generate
gerbers.
– Easy to use graphical interface.
– No
Boost SMPS
Our book uses this circuit in a example converting 2D batteries
(2.4V) to drive a single power LED (3V).
•Vin < Vout
•Vin max 6V.
•Vin always connected to L1.
•Internal transistor ON pulls SW
to GND. Thus L1 current goes
up, D1 is off.
•Transistor OFF pulls SW above
FB to turn on D1 to power LEDs
and causes L1 current to go
down.
Practical DC Drive Circuitry for LEDs. Lenk, Ron and Carol. “Practical
Lighting Design with LEDs.” Wiley, 2011.
AC Example
Our book uses this circuit in a example BR40 self ballasted light bulb
design.
•Supertex HV9910 uses
external MOSFET Q1. Current
controlled Buck converter.
•R2 sense resistor sets
current.
•R1 sets the switching
frequency.
•When Q1 is on, D1 is off, L1
current increases.
•When Q1 is off, D1 turns on,
L1 current decreases.
•Vin can be up to 450VDC,
usable worldwide.
HV9910 Demo Board
The HV9910DB3v.3 can supply a maximum
output current of 900mA to drive LED strings
from a 9VDC to 30VDC input. It achieves an
overall efficiency above 85%. The
HV9910DB3v.3 is ideally suited to drive two
1Watt or 3Watt LEDs from a 12V or 24V input
voltage.
Demo Board Schematic
Bill of Materials (BOM)
• Tolerance not an issue.
• Narrow down by Operating Temperature, Min
Qty, Click on up-arrow under Price:490-55201-ND
Surface Mount Packages
Resistors
•
•
•
•
Search: Resistor. Select: Chip Resistor-Surface Mount.
Select: 147 K, 1/10 W.
Select: Cut-tape.
0805 is $0.86, 0603 is $0.10: P147KHCT-ND
Remaining Component
• Search: Schottky Diode. Select Diodes, Rectifiers, Single.
• Select 40V, 1 A, SM. Sort by price: 641-1015-1-ND
• Search: Power Inductor. Select: Inductor, Coils, Chokes – Fixed.
• Select 220 uH, 1 A, Shielded: 513-1424-1-ND
• Search: MOSFET N-Channel. Select: FETs, Single.
• Select 50 V, 2.4 V to 15 V. Sort by price, pick SM: RFD14N05LSM-ND
• Search: HV9910. Select: PMIC – LED Drivers.
• Pick no heat pad: CLA320CT-ND
Digikey Order
Thank You