Diodes AL5802 User Manual
Page 9
AL5802
Document number: DS35516 Rev. 9 - 2
9 of 11
March 2014
© Diodes Incorporated
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To remove the potential of incorrect connection of the power supply
damaging the lamp’s LEDs, many systems use some form of
reverse polarity protection.
One solution for reverse input polarity protection is to simply use a
diode with a low V
F
in-line with the driver/LED combination. The low
V
F
increases the available voltage to the LED stack and dissipates
less power. A circuit example is presented in Fig. 18 using Diodes
Inc. SBR® (Super Barrier Rectifier) technology. An SDM10U45LP
(0.1A/45V) is shown, providing exceptionally low V
F
for its package
size of 1mm x 0.6mm, equivalent to an 0402 chip style package.
Other reverse voltage ratings are also available in Diodes’ website
such as the SBR02U100LP (0.2A/100V) or SBR0220LP (0.2A/20V).
Automotive applications commonly use this method for reverse
battery protection.
A second approach, shown in Fig. 19, improves upon the method
shown in Fig. 18. Whereas the method in Fig. 18 protects the light
engine, it will not function until the problem has been diagnosed and
corrected.
The method shown in Fig. 19 not only provides reverse polarity
protection, it also corrects the reversed polarity, allowing the light
engine to function.
The BAS40BRW incorporates four low V
F
, Schottky diodes into a
single package and allows more voltage available for the LED stack
and dissipates less power that standard rectifier bridges.
Fig. 18 Application circuit for LED driver
with reverse polarity protection
Fig. 19 Application circuit for LED driver with
assured operation regardless of polarity
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