automotive dc dc boost converter help

Hey all, I am looking for some help with finding an automotive rated boost converter.

I want to replace the LEDs and driver circuits in a diode dynamics 12” driving light bar with osram white flat 1 and push them much harder than the diode dynamics circuitry does. Preferably >4A.

There are 12 LEDs in this lightbar, so I was thinking a boost converter would be the best approach, rather than trying a bunch of strings of series and parallel together, but if thats what I need to do, I’ll deal with it.

I see TaskLED has released the UltraBoost converter, but it appears to be limited to a hair under 4A, and perhaps 12 osrams in series would be asking a bit much from a single driver, from a power/heat perspective.

Also, with automotive power being fairly dirty, I’m looking for some advice as how to best protect the driver from reverse polarity (assuming it lacks such protection) and voltage spikes from an automotive relay opening/closing.

For dirty automotive power, how about Super Capacitors. Clean as a bean. :-)


That’s not a bad idea to clean things up. I’ll start looking at what if out there for HID/LED conversions (bleh) as some of the ballasts don’t play nice with PWM vehicle circuits.

What voltage do you need—to what voltage do you want to boost the 12V?

12 in series. So roughly 36-40v range depending on the forward voltage.

So for a 4Amp load the DCDC (12V/40V) would need to be rated about 160W output; and for a 5A load about 200W.

On the 12V input side you would need a 14 to 20Amp supply.

This would only cover the voltage conversion for the supply; then you would need an LED driver/amplifier to regulate the load current.

There may already be such a device out there, my DCDC boards operate at 400V/12V 125Amps.

And this is where I’m stuck. I’m looking for a boost converter that can push the current I want, even if the voltage output is lower, I can handle wiring in more than one string if I need to.

I see buck converters like this that I could use, but for 12 strings I would need 3, which adds cost, bulk (issues with locating drivers in relation to the bar) and 6A is pushing it for the white flat 1, likely needing me to switch to the flat 2mm^2. And given this buck regulator is limited to 12v output, not sure it would reach that full 6A power with 3 strings of 4 series wired LEDs, given djozz’s test show the forward voltage of the at 6A being nearly 3.5v

The above link also has a 13.8v output 10A output model… even with the boost HX/white flat 2.2 that’s pushing the current in something that has limited mass, and the smaller footprint peaks at about 7.5A based on djozzs testing…

Two Taskled Ultraboost drivers would provide 4A. Wire 6s LEDs per driver. A single DIWDiver 16.7A linear driver could work also with 4s 3P config. A Pololu shunt regulator might work to supress voltage spikes.

Alright, here’s a question, would it be possible to wire two powersources in parallel to a single string of LEDs? Say two ultraboosts wired with a diode to prevent one from backfeeding into the other?

I believe the answer is no but you should ask taskled directly. Let us know what he says.

George at TaskLED stated that two of the UltraBoost drivers would be a good candidate for driving a string of 6 LEDs to 4A.

He also offered the H6cc in a buck arrangment for the whiteflat 2mm LEDs, however being a buck driver, I’d need more and wire into strings of 3.

If you want to control both drivers from a single POT, use a “dual gang” POT to do so.

I think I should be good to use the onboard pot, it’ll be a set and forget type of thing. Once I’ve got the current dialed in I’d just leave it, unless swapping the LEDs again at some point in the future.

My remaining question is how I can trigger the switch circuit without an additional switch. I’d like them to turn on when power is supplied.

The board will turn on automatically when power is applied to IN+. No switch is required.

“SHDN is connected onboard to IN+ via a 100k ohm resistor. This will power the driver up by default. If the user wishes to power down the Ultraboost driver, the SHDN pin should be driven low (nominally 0V). In shutdown mode the Ultraboost draws less than 30uA. Maximum input voltage to SHDN is IN+ voltage.”

Thanks Hoop, I appreciate the help.

So I picked up this:\_=pd_bap_m_rp_1_sc boost circuit.

12v -> 36v DC, 5A output (claimed). I will have an order in with led4power for osram LEDs tomorrow. Looking forward to stepping this project forward.

I now also have a question about using a 4s fet driver. Take this one from mtn electronics: 30mm FET + 7135 Driver - MTN-30DDm - 2S-4S Input Voltage (Clicky) from a relay circuit in a running vehicle with a healthy battery, I can expect to see around 14v to the driver. If I were interested in using this to try and power a series of 4 3vf LEDs, should I be purposefully reducing wire gauge to try to limit current?

You need regulation. DIWdiver’s driver in 10A flavor would do the trick. You can limit the max current to less than 10A with the trimpot. The low voltage cutoff value is configurable when you order.

BTW I’m on page 813 of Atlas Shrugged. $

i used cheap boards from ebay, in cars to power aux equipment, at first i was worried about “dirty power” killing the dc-dc borads, but so far none died. so imo, either the concept “dirty power” is overblown, or newer cars have good enough regulation so it does not become a problem,