Automotive 3/6/9A driver - feeler thread

DIWdiver

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Hi gang,
I'm considering developing a new driver for the high-power LED automotive market.

My big question is: would anyone want this instead of DerWichtel's driver?

Characteristics of this driver would be:
Similar in operation and based on the IS1006 driver.
Suitable for use in 12 volt automotive application without external components (except hi/lo switch and LED).
Linear Current regulation - ideal for LEDs, won't cause electrical interference.
Current up to 10A, possibly more.
1 or 2 modes, either or both adjustable.
Modes selectable by toggle switch, not clicky, etc.
Thermal protection for the driver, which can also protect LEDs if designed properly.
Linear regulation, which means only moderate efficiency, and requires 3-4 LEDs in series, and good heatsinking for the driver.
Price $35-40, including thermal mounting pad.
Size around 1.5" x 1.5" x 0.5".
Mounting by single 6-32 or M3 screw. A second mounting hole would be provided for optional use.

I'm looking to see what the interest is in such a driver, and any suggestions for features I haven't thought of.

Suggested uses:

Three SST-50s or SST-90s in series, full output when engine is running, reduced output when engine is off and battery is not fully charged.

3, 6, or 9 XM-L in 3S1P, 3S2P, or 3S3P configuration, full output whether engine is running or not.

4, 8, or 12 XM-L in 4S1P, 4S2P, or 4S3P configuration, full output when engine is running, quite reduced output when engine is off. Can be tricky to reach full 3A/LED.

Could also be used for single or dual (2S1P) XM-L or dual SST-50 applications. The efficiency would suck, but maybe that doesn't matter.

Any comments are welcome.
 

Mattaus

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I'm open to any drivers developed specifically for automotive use - there are not enough doing the rounds. I've fiddled with developing my own LED light bar for my 4WD in the past (other projects have taken precedence however) but one thing I struggled with was driving the emitters. Realistically you can't use generic flashlight drivers.

Some things that need to be considered (and I'm no electrical expert) is voltage spikes especially when the car engine is running. How will your driver deal with these spikes?

That price seems excellent if you can keep it at that...

EDIT: Der Wichtel goes through a potential protection method in his 9A buck converter thread involving Zener diodes and capacitors. This is all well and good but I am eluding more to an built-in method. Less work for people to have to do, and closer to the traditional wiring job that we are all probably more used to. Just a suggestion :)
 
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sadtimes

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This would be awesome.. now if only someone could make a cnc machined housing for some sst-90's we would be all over this....
 

DIWdiver

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I'm open to any drivers developed specifically for automotive use - there are not enough doing the rounds. I've fiddled with developing my own LED light bar for my 4WD in the past (other projects have taken precedence however) but one thing I struggled with was driving the emitters. Realistically you can't use generic flashlight drivers.

Some things that need to be considered (and I'm no electrical expert) is voltage spikes especially when the car engine is running. How will your driver deal with these spikes?

That price seems excellent if you can keep it at that...

EDIT: Der Wichtel goes through a potential protection method in his 9A buck converter thread involving Zener diodes and capacitors. This is all well and good but I am eluding more to an built-in method. Less work for people to have to do, and closer to the traditional wiring job that we are all probably more used to. Just a suggestion :)

DW suggests clamping everything at 20V. However, in the worst cases, there can be a huge amount of energy available at 20V. That's why he suggests using 5 diodes in parallel. I'm not sure even that's enough in the worst cases, but then most vehicles will never see the worst cases.

My board would clamp spikes (high voltage, but low energy) at around 80V, and survive surges (lower voltage but higher energy) up to 80V. The driver would survive a short time at 80V, but not a long duration. This approach requires a high-voltage mosfet, which doesn't work well at really low voltages, but that's not an issue here. It also doesn't require large capacitors or multiple diodes.
 

Mattaus

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OK, so protection is built in which makes this driver perfect.

vg67654_shut_up_and_take_my_money-n1294512916668.jpg
 

SemiMan

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Unless I am building them by the thousands, I don't really care about EMI. If I am building them in the thousands, then I am not going to pay 35-40 for what amounts to a simple linear regulator.


FYI, the HV mosfet is really not an issue for this application since you would almost never be fully enhanced so RDSon does not really matter too much. That said, since it's linear, you are going to clamp at a low voltage any way.

Just not seeing the value in this too much.
 

SemiMan

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Let's also keep in mind:

- 10Amps
- 14+ volts + when the car is running
- 3 leds in series, say 10.5V forward
- That's a minimum of 35watts of dissipation and could be higher

Takes a heck of a good sized heat sink to dissipate 35 watts ... much more than can be mounted with a #6 screw.
 

Moddoo

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I've been running one of Don's automotive drivers to 4 XML in series @ 5A on the front of the truck for maybe 6 months now.
Thermal interface is a screw to the light case with some Arctic silver.

No problems at all so far.

I am getting ready to expand the setup to 20 leds.

These work great, and the high/low function is nice.
 

DIWdiver

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Out of curiosity, and not to sound too silly, but which Don are we talking about and which driver?

The Don he's talking about is me. The driver is the IS1006 discussed extensively here:
http://www.candlepowerforums.com/vb...stable-10A-linear-LED-driver-New-and-Improved!

While not originally designed for automotive applications, with a few component changes and two external components, it adapted pretty well for that.

What I'm considering now is a driver designed specifically for automotive applications, so it wouldn't need external components. Because of the large power dissipation pointed out by SemiMan (and discussed elsewhere as well), the FET will be in a larger package to help with heat transfer. I've also thought that temperature protection would also be a good idea, given the high power levels that are readily available in a vehicle, which can easily overdrive even a very large heatsink. People are discussing builds up to 500W (LEDs + driver) with multiple IS1006s.
 

DIWdiver

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Unless I am building them by the thousands, I don't really care about EMI. If I am building them in the thousands, then I am not going to pay 35-40 for what amounts to a simple linear regulator.


FYI, the HV mosfet is really not an issue for this application since you would almost never be fully enhanced so RDSon does not really matter too much. That said, since it's linear, you are going to clamp at a low voltage any way.

Just not seeing the value in this too much.

You might care about EMI if you were trying to listen to the radio in the vehicle with the lights on. Others have commented on severe interference from cheap imported drivers. I would expect DW's driver to be better, but any switcher will generate broadband EMI. It takes careful design and mitigation to minimize (never eliminate) this, and that don't come cheap.

If you ordered 1000 pcs, I'm sure I could dramatically reduce the price. The estimated price is for 1 pc. with total production in the dozens.

You're right that the high-voltage FET isn't a big deal. But it isn't trivial either. You want one with good heat-transfer characteristics, which means a big die. And if you want to run 4 XM-Ls in series when the vehicle is off, you don't have any overhead on the regulator. Four times 3.35V is 13.6V, so in this case your overhead is less than zero and ANY resistance in the FET costs you output. In this situation the FET would be fully enhanced. The question isn't whether the output is reduced, it's how much is the output reduced, and that depends partly on the FET.

As far as not seeing the value, I welcome that input. In fact, I question the value myself. The reason I started this thread is to see if enough people see the value to make it worth my time to build the driver. Also, I wanted to see if anyone had ideas that could add to the value.
 
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Mattaus

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Thanks for clearing that up - there just seem to be many 'Don' characters here on CPF it can make keeping tabs on who's doing what a little difficult. It also doesnt help that Der Wichtel makes drivers, and his drivers are commonly referred to as DW drivers which, as you can probably see where I am going here, is close to DIW.

Or maybe I'm the only one getting confused:stupid:


I think demand for these drivers would increase if most people realized that while you can use normal off the shelf drivers in automotive applications, it's not the best or most robust long term solution. At the moment I don't think that sort of knowledge is out there, and it might take a few actual builds to get the word spread. If you ever get these going I am definitely in for a handful (lets say 5 or 6) but that would only be after I get my new Amarok, and that's still a number of months off. The girlfriend won't let me build anything in advance...apparently 'enough is enough' :(

So for me personally I sincerely hope others jump on this just so that there is something for me to get down the track!!!

Cheers,

- Matt
 

SemiMan

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You might care about EMI if you were trying to listen to the radio in the vehicle with the lights on. Others have commented on severe interference from cheap imported drivers. I would expect DW's driver to be better, but any switcher will generate broadband EMI. It takes careful design and mitigation to minimize (never eliminate) this, and that don't come cheap.

If you ordered 1000 pcs, I'm sure I could dramatically reduce the price. The estimated price is for 1 pc. with total production in the dozens.

You're right that the high-voltage FET isn't a big deal. But it isn't trivial either. You want one with good heat-transfer characteristics, which means a big die. And if you want to run 4 XM-Ls in series when the vehicle is off, you don't have any overhead on the regulator. Four times 3.35V is 13.6V, so in this case your overhead is less than zero and ANY resistance in the FET costs you output. In this situation the FET would be fully enhanced. The question isn't whether the output is reduced, it's how much is the output reduced, and that depends partly on the FET.

As far as not seeing the value, I welcome that input. In fact, I question the value myself. The reason I started this thread is to see if enough people see the value to make it worth my time to build the driver. Also, I wanted to see if anyone had ideas that could add to the value.


80+V N-channel FETs under 10mohm are pretty inexpensive these days (rated in the 100+W range too). Even P-Channel are pretty much there and with obviously simpler drive circuitry. 10mohm (over temp) at 10 amps is 100mV. Odds are wiring is going to be a bigger issue than the drivers. Softening the edges on the switcher so that you get 80's instead of 90's efficiency can eliminate much of that noise issue as can a bit of filtering. I find that once you hit high powers, it is cheaper to put the money into filtering versus aluminum, etc. for the heat sink. It is great if you can use the vehicle, but steel makes for a poor heat sink. Can't say I have ever heard any noise on my car stereo when I have had LED drivers hooked up to the battery, some of which have been 50+ watts. Many car stereos have switchers for higher voltage for their amplifiers these days ... home stereos too. If you are going to build 10, then yes likely not worth the time to work out the noise issues, but lots of high voltage, high powered switch mode controllers that will take load dump without any issues.

Semiman
 

DIWdiver

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80+V N-channel FETs under 10mohm are pretty inexpensive these days (rated in the 100+W range too). Even P-Channel are pretty much there and with obviously simpler drive circuitry. 10mohm (over temp) at 10 amps is 100mV. Odds are wiring is going to be a bigger issue than the drivers. Softening the edges on the switcher so that you get 80's instead of 90's efficiency can eliminate much of that noise issue as can a bit of filtering. I find that once you hit high powers, it is cheaper to put the money into filtering versus aluminum, etc. for the heat sink. It is great if you can use the vehicle, but steel makes for a poor heat sink. Can't say I have ever heard any noise on my car stereo when I have had LED drivers hooked up to the battery, some of which have been 50+ watts. Many car stereos have switchers for higher voltage for their amplifiers these days ... home stereos too. If you are going to build 10, then yes likely not worth the time to work out the noise issues, but lots of high voltage, high powered switch mode controllers that will take load dump without any issues.

Semiman

Clearly a properly designed switcher is a much better choice than a linear at high power levels. The fact that today's cars are loaded with them (including, I imagine, high power LED drivers for headlights) is proof of that. Unfortunately, there doesn't seem to be a DIY one readily available for high-power LEDs in an automotive environment. DW's is the closest, and it needs 10 external parts to provide reasonable (not bulletproof) protection.

Since I don't have the ambition to go to the effort necessary to develop a proper switcher that will survive, won't wipe out your radio, will be efficient, and sell at a reasonable price, at small quantities, I wonder if anyone else will either.

If I wanted to build a light bar like people here are using the IS1006 for, I'd probably build exactly the board I'm talking about. It just isn't worth the effort to do anything else. Or maybe I'd just use a few IS1006s. Oh, who am I kidding; I'd build the board. It's what I do.

When I designed the IS1006 a few years ago, I expected it would be obsolete within a few months, given that two CPF members were working on switchers. I decided to buy 30 PCBs, planning to break even on the cost if I sold 20 pieces, make a few bucks if I sold more. I lost track somewhere around 70 pcs, and just shipped two yesterday. So it's not a huge commercial success, but it filled a niche need, which was the original intent.

The big question today is 'Would a similar driver tailored to the automotive market fare as well?' Given that the response to my feeler is very excited people who are very few in number, I don't think the answer is yet clear.

D
 

DIWdiver

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Hi,

Glad to see I'm not the only person in the world struggling to find a driver that will work in the automotive world.:)

Wouldn't you only have to design for 40 volts if you used AUML's in the protection circuit?

http://www.littelfuse.com/products/Varistors/Multilater+Varistors+(MLV)/AUML.html

Good luck

Mark

Yes, those look like pretty good parts. They are expensive though. I ran across them the other day while researching load dump protection, for this project.

However, in this particular case, the difference between designing for 40V and designing for 80V is pretty minimal (often it isn't). I haven't been through a careful design process yet, but I suspect that when that is said and done, it would turn out to be better to design for 80V and save the cost of these parts. Still, it's a good tool to have in the toolbox.

D
 

SemiMan

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Actually for real automotive design, it can be far harder to design for double battery (boosted wrong) and failied regulator (19 volts typ for test) as now you can be dissipating some serious power with a linear solution. Usually a fold back is the best option and simplest. With a switch mode, this can be normal operation.

Semiman
 

DIWdiver

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That could be a problem if the LED lights are on when you try to jump the vehicle or if the regulator fails. I suppose it would be a good exercise to investigate whether the thermal limit would protect the driver before it gets destroyed. FET die temperatures would rise pretty fast if the input were 24V and the output was 9A @ 10V! 126W isn't unreasonable for the FETs I'd be using, subject to proper heatsinking. If the thermal limit sensor (thermistor) is well coupled to the die, it would be okay. If not, there could be a failure.

Perhaps an 'overvoltage cutout' circuit would be a good addition. I'll have to look into the thermo-mechanics of it to know.

Thanks for the input.
 

SemiMan

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You can do wonderful things with a 12V zener and resistor connected at the right spot. It makes for a simple voltage driven current fold back. There is no expectation of proper operation past about 14.8V or so in automotive. Things just need to survive past that voltage, not operate normally.
 
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