■ FIGURE 4. The finished project.
Cree® 1-A XLamp® LEDs bring out the
blue from the curio cabinet contents.
■ FIGURE 6. LED and heatsink assemblies mounted to the
incandescent light fixture.
highlights in the dishes in the china
curio cabinet (Figure 4). With
darker china patterns, a warm white
LED may be more appropriate. The
LED provides up to 100 lumens.
While this is significantly less
lumens than a standard
incandescent bulb, the LED focuses
this light to where it is needed
which significantly reduces the
required lumen output.
The necessary LED current for
a specific application is difficult to
calculate. The best approach is to
empirically adjust the LED current
until you get the desired lighting
effect. Select the lowest current
that provides acceptable results.
Lower currents minimize power
dissipation and reduce the LED
temperature which
increases the LED’s
lifetime.
Size R2 to
handle the required
power dissipation.
Because the full
We settled on an 820 mohm resistor in this design
which results in 975 mA of LED current; it dissipates 780
m W of power. You must design the remaining power
supply components to operate with the actual input and
output voltage range. An application note for the
TPS54160 provides all necessary design equations; all
design equations are integrated into an easy to use Excel
■ EQUATION 2.
ILED2 PR2= R2
■ FIGURE 5. LEDs and PWB with
thermal vias mounted to the aluminum
heatsink.
Michael Day, Power Management
Application Supervisor for Texas
Instruments’ Power organization,
has more than 16 years design
experience in the field of power
conversion. Currently, Michael
manages the DC/DC Power
Applications group at TI. He
received his BSEE and MSEE in
Pulsed Power from Texas Tech
University, Lubbock, TX. Michael is
a member of IEEE and has
published over 65 articles on power,
portable power, and lighting topics.
You can reach Michael at
ti_michaelday@list.ti.com.
32
November 2011
