I've been sort of ignoring this thread, but if I wanted simplicity, I would fall back to the basics. The LED does not care what voltage is applied, it needs current limiting.
Adding a regulator is something you really don't need, although the DC to DC converter is a great idea, it solves 2 problems, low track voltage, and also it allows you to use a higher supply voltage and put LEDs in series.
What I would do is have the DC to DC inverter (fed by a FW bridge of course) running at a voltage that was convenient, ideally what would be needed by all the LEDs in the car in series. Then I would use a CL2 current regulator in series with the diodes to control the current.
example: say I wanted to run 6 white LEDs which had a nominal forward voltage of 3.6 volts each. So, I would want slightly more than 3.6 * 6 volts, so say 24 volts... put all the 6 LEDs and one CL2 current regulator in series. Feed from the DC to DC inverter and a nice big 35 volt cap on the output. I don't see a reason to put a cap on the input.
Now this is a pretty efficient setup, and will store the voltage in the cap, and the inverter will work down to pretty low input voltage. put any extra money in a larger cap.
This should run for quite a while with virtually no power... you might have to make the output voltage on the DC to DC inverter a bit higher but with today's LEDs they run at significantly lower current (and voltage somewhat) than the 20 milliamperes the CL2 provides. You could also make a series parallel setup of the LEDS, paralleling 2 strings of 3 LEDS, and split the 20 milliamps from the CL2 among the 2 strings, giving each LED 10 ma, which is normally just about as bright, and this lets you lower the "voltage" requirements of the DC to DC inverter, allowing "charging" of the capacitor at a lower voltage, or keep the voltage at 24 and have a lot more reserve.
Greg
Adding a regulator is something you really don't need, although the DC to DC converter is a great idea, it solves 2 problems, low track voltage, and also it allows you to use a higher supply voltage and put LEDs in series.
What I would do is have the DC to DC inverter (fed by a FW bridge of course) running at a voltage that was convenient, ideally what would be needed by all the LEDs in the car in series. Then I would use a CL2 current regulator in series with the diodes to control the current.
example: say I wanted to run 6 white LEDs which had a nominal forward voltage of 3.6 volts each. So, I would want slightly more than 3.6 * 6 volts, so say 24 volts... put all the 6 LEDs and one CL2 current regulator in series. Feed from the DC to DC inverter and a nice big 35 volt cap on the output. I don't see a reason to put a cap on the input.
Now this is a pretty efficient setup, and will store the voltage in the cap, and the inverter will work down to pretty low input voltage. put any extra money in a larger cap.
This should run for quite a while with virtually no power... you might have to make the output voltage on the DC to DC inverter a bit higher but with today's LEDs they run at significantly lower current (and voltage somewhat) than the 20 milliamperes the CL2 provides. You could also make a series parallel setup of the LEDS, paralleling 2 strings of 3 LEDS, and split the 20 milliamps from the CL2 among the 2 strings, giving each LED 10 ma, which is normally just about as bright, and this lets you lower the "voltage" requirements of the DC to DC inverter, allowing "charging" of the capacitor at a lower voltage, or keep the voltage at 24 and have a lot more reserve.
Greg
