The scenario
A 12 V automotive electrical system powers a high-power LED headlamp; load dump and reverse-battery events must not destroy the LED string.
What is in this drawing
Read the decisions behind it.
01
Series fuse and reverse-polarity diode isolate the downstream constant-current stage from harness faults.
02
Two-transistor current limiter uses Q1 as the pass element and Q2 to regulate the voltage across a 1.8 ohm sense resistor, holding LED current near 350 mA.
03
Zener diode across the input clamps transient overvoltages before they reach the LED string.
Linear constant-current LED driver for 12-14 V automotive DC, moderate LED current, and overvoltage/reverse protection.
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