are defined in different automotive specifications
such as:
are turned off within the vehicle, switching
transients of electronic circuitry, alternator field
decay, or a fully discharged battery being
disconnected while the alternator is operating at
rated load. These transients consist of both
positive and negative pulses with different
amplitudes and decay times.
DIN 40839 Part 1
“Electromagnetic Compatibility (EMC) in Motor
Vehicles; interferences conducted along supply
lines in 12 V onboard system”
DIN 40839 Part 2
Limited reliability testing has been done with
AlInGaP LED emitters connected in typical LED
signal lamp configurations.
“Electromagnetic Compatibility (EMC) in Motor
Vehicles; interferences conducted along supply
lines in 24 V onboard system”
High-voltage negative transients in excess of the
reverse breakdown voltage can permanently
damage AlInGaP LED emitters. Sufficient energy
can be dissipated within the AlInGaP LED die to
cause localized damage to the p-n diode
structure. This damage can result in reduced
breakdown voltages, and degraded low-current
performance. Under extreme conditions, high
voltage negative transients can even destroy the
p-n junction, resulting in a short between anode
and cathode.
ISO 7647-1
“Road Vehicles—Electrical Disturbance Caused
by Conduction and Coupling; passenger cars
and light commercial vehicles with nominal 12 V
supply voltage”
ISO 7647-2
“Road Vehicles—Electrical Disturbance Caused
by Conduction and Coupling; commercial
vehicles with nominal 24 V supply voltage”
SAE J1113
Adding a high-voltage silicon diode in series with
the LED signal light array, such as previously
shown in Figure 3.6, can prevent potential
damage to high voltage negative transients. The
silicon diode should have a higher reverse
breakdown voltage than the amplitude of the
worst-case negative transient, which can be as
large as –300 V (–600 V for heavy trucks). Table
3.2 shows several recommended silicon diodes
for different LED signal lamp applications.
“Electromagnetic Susceptibility Measurement
Procedures for Vehicle Components (except
Aircraft)”
SAE J1211
“Recommended Environmental Practices for
Electronic Equipment Design”
SAE J1812
“Function Performance Status for EMC
Susceptibility Testing of Automotive Electronic
and Electrical Devices”
In addition, high-voltage positive transients can
permanently damage AlInGaP LED emitters.
Sufficient energy can be dissipated within the
AlInGaP LED die to cause permanent damage to
the p-n diode structure and cause epoxy
These specifications define several electrical
transient pulses that occur when inductive loads
28
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