This circuit is designed to replace a dual-filament incandescent bulb in a combined brake/tail light for automotive use. When power is applied to the 'Tail' input the current in the LED is regulated to 300mA. When power is applied to the 'Brake' input or both inputs simultaneously, the current in the LED increases to 900mA. The 'Brake' and 'Tail' input voltage can vary between 8V and 40V This makes the circuit suitable for standard passenger cars and trucks with 8V-16V batteries as well as freight trucks, tow trucks, fork lifts, and other vehicles that use a double lead-acid battery system, or 16V-32V. Diodes D3 and D4 provide reverse battery protection, and D2 ensures that a 'Brake' input supercedes a 'Tail' input. The LM5010 can withstand inputs voltages of up to 75V. This circuit does not need additional protection from 'load dump' events up to 75V.
Although not shown, the brightness of the LED can be dimmed with a PWM input by placing a signal-level NFET from the RON pin to ground and driving the gate with the PWM signal. This circuit is also compatible with 100Hz PWM of the input voltage for 'theater dimming' of interior lights. Please note that the PhotoMOS M1 and the op-amp A1 are shown as Q1 and U2 in the PCB layout, respectively.
Schematic
Example Schematic Showing Connection for all Components.
Example Schematic Showing Connection for all Components.
