What about using of Smart power switch BTS 133 ?

[Pet]

I have tried to switch the fuel HiZ injector with a smart lowside power switch BTS133 (60V,7A,50mOhm), this one is equiped with a driver (so logic level input) and many of protections (overload, thermal, overvoltage...). Clamping voltage is internally set to 60-73V (this was confirm by a scope), clamping energy 2000mJ, and it was hapilli switching without any cooling. What do you thing about using these unclamped (externally) smart FET's in ECU ??

(upper ch. 20V@2ms/d, lower ch. 5V/d - 5V PWM input 20Hz) - Audi N75 boost valve (034 906 283J) switching test

[MWfire]

I use irf640N. 200V 18A 0.15ohm. I don't have heatsink


Once i accidentally disabled pwm on low impendance resistors(0.9ohm) and drive car for 30km without overheating problems(mosfet, injectors were veary hot:)

[GintsK]

What you talking about? LowZ or HigZ injector control?
 I use cheap STF20NF06 60V - 0.06 Ω - 20A TO-220/TO-220FP
 http://www.datasheetcatalog.org/datasheet2/3/06fsdziq30itys6isqu3r0hy1uky.pdf

It easily survives in both applications. I have no one failed without clear reason.

We need find a reason for frequently smoked FETs on many units.
E.g. is BTS133 is protected from voltage spikes on Gate? VEMS use Ubatt on INJFET gates. May be this is a reason.

[Pet]

We need find a reason for frequently smoked FETs on many units.
E.g. is BTS133 is protected from voltage spikes on Gate? VEMS use Ubatt on INJFET gates. May be this is a reason.

  Yes, BTS133 has ESD input protection, it seems for 10V zener diode, because this smart FET is designated to be driven with 5V logic levels. I'll try it in real and let you know.

[MWfire]

We need find a reason for frequently smoked FETs on many units.
E.g. is BTS133 is protected from voltage spikes on Gate? VEMS use Ubatt on INJFET gates. May be this is a reason.

  Yes, BTS133 has ESD input protection, it seems for 10V zener diode, because this smart FET is designated to be driven with 5V logic levels. I'll try it in real and let you know.

With 10V zener diode and 14V of supply voltage, this will give 120mA gate current(to much for resistor).
My suggestion is irf640N and 100V zener diode solder to PCB(backup for flyback). It's veary cheap(0.6$), veary fast, but doesn't have protection for short circuit.

[rob@vems.co.uk]

The smart power switch is not recommended for driving injectors, the FETs we use have been selected because they are suitable for the job.
If you choose to use these smart switches then you'll have to accept that you are in an experimental world and all the problems that are associated with it.

So if that's the sort of thing that excites you then you'll need to change the resistors that feed the gate and increase them to something like a 1K value.

[lugnuts]

Just curious - what do the commercial ECU use for injector drivers?

I have installed 100+ Autronic ecus which can run saturated and peak-hold injectors, no need for flyback wiring, 2X18 (SMC/SM2)or 1x14 AWG(SM4) Ground wires for the whole ECU.
And I never, ever, had a problem with a single unit.

And the Link/ViPEC ECU - the V44/Plugin has saturated drivers that are very small surface mount chips, no heatsinks, no clumsy clamping plates. What do they use?


Why re-invent the wheel here?

[rob@vems.co.uk]

I think it came down to costs and availability.  The LowZ injectors were originally PWMed for peak and hold, but it turned out that using Resistors and a transient suppression diode gave better injector control.

[lugnuts]

But what are the causes of the failed FETS people are having?

If another design does not need the flyback wire, and has the same or better control and reliability, then why not use that method?

These ECU's have a very high feature to dollar ratio. I wouldn't even blink if I was asked to pay $50 more to make them more reliable. The cost to me of having one customer with a problem is much much more than that.

[rob@vems.co.uk]

You will find that there are FETs that have a flyback diode in them, but you need external diodes to clamp the voltages in any serious manner.
If the injectors are correctly fused then the fuse should protect the FET.

[lugnuts]

I'm not very knowledgable on electrical engineering, so much of this is over my head.

I just hate the clamping plates, and having to depend on the flyback circuit.
Many of my Plug-and-Play applications (IE: OEM Wiring) no longer have flyback.
And most of the Commercial Aftermarket ECU's do not have flyback either, so I know it can be done reliably. Especially with Saturated injectors.

My biggest wish is to have surface mount DPAK style drivers, and no need for flyback. 
This way I would need either 0 clamping plates, or 1 plate just for the 4 IGBTs I usually specify.

About the injector drivers themselves, there are new saturated injectors on the market that out-perform any injector available. They are 880cc/min on test fluid, 1000cc/min on VP C16 fuel, at 3 Bar pressure. They are perfectly happy operating at 100+ PSI fuel pressure.

I am using these injectors now so I no longer even care about peak and hold operation. Less problems as far as I'm concerned.

[GintsK]

I think it came down to costs and availability.  The LowZ injectors were originally PWMed for peak and hold, but it turned out that using Resistors and a transient suppression diode gave better injector control.

Sorry, Rob, but I can't agree with your statement! My experience said vice versa, if it refers to control, not the hardware bugs.

But about hardware: my thoughts is we need one level higher protection from spikes in supply.
Now I have even two cases when outer transients in vehicle cause total config or even firmware crash!!!
One time it was cheap relay in external circuit. Other - welding with disconnected battery, but not disconnected VEMS.

I have opened SMC on table - it is full of caps.

[PeepPaadam]

I had failed P259 and stepper chip due to failed coil-pack (had a crack in the housing) that sparked (arced?) to the chassis.

I personally haven't had mysteriously failed FET's but one of my customers had, and it failed for absolutely no obvious reason (car has been running for a few months, BMW E30 with 745 3.5liter turbocharged engine, Siemens Deka 630cc injectors).