MOSFET for high speed PWM

Would this be a good alternative IC?
http://pdf1.alldatasheet.com/datasheet-pdf/view/12074/ONSEMI/MC34151P.html

(The one you suggested is not available from the supplier I will be ordering other parts in the next few days anyway.)

Almost...they require a minimum 6.5V Vcc voltage while the TC4426A works at 5V. If you have a 7V-12V supply available you could use that. Otherwise it looks like it will do the job.

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Alright! I'm curious to learn of your results.

Me Too!

I THINK most 'Regular' Red / IR LEDs are relatively linear with pulsed current VS radiant output, up to some point.

If so, for IR communication / beam detection the (unknown to me) question is the RECEIVER response and how that works into the equation. ie. does twice the pulse current give twice the response, or can the pulse be "too short"??

White LEDs etc. that have a phosphor that indirectly produces light CAN be pumped to higher levels with short pulses and give a beneficial non-linear response to short high-current pulses. I read somewhere.

No question that pulsed IR beams are far more stable and long-range with tuned receivers than simple on-off source / receiver. These are cool: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=86 when you need to have a beam several meters from the transmitter to receiver.

I want to experiment with an infrared laser for long beams. I'd like to design a product that includes a visible laser you turn on temporarily to align the transmitter to the receiver. Then the Invisible beam can trip your camera, etc...

Thanks again RuggedCircuits and Terry, I'm about to leave for a concert but will come back tomorrow for the details.

Do I need anything else beside the driver IC and the mosfet? Any special resistors / capacitors for that part of the circuit?

I would add a resistor (10k?) from the input of the MOSFET driver to ground to keep it off when the Arduino is in reset or being programmed. Don't want those MOSFET's turning on at random times! I'd put a similar resistor from MOSFET gate to ground just to bleed charge from the gate should it start to accumulate while you are messing around with wiring and such.

I can't think of where you'd need capacitors....oh...wait, I'd put a capacitor at the power supply of the MOSFET driver (between the supply pin and ground), 1uF-10uF as minimum, bigger is better (but don't go nuts else you'll have a huge inrush current).

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or can the pulse be "too short"??

Terry, I can only guess at this point, but assuming you have a fast photodiode with rise & fall times in the nanosecond range I assume that this part will not be a problem.
But what the effect of the following bandpass filter and demodulator will have, I have no idea... I guess we will see in a few days once I got all the parts.

RuggedCircuits:
Would you mind having a look at this datasheet http://www.vishay.com/docs/91126/sihfd024.pdf
After lots of digging through datasheets it seems that this might be a candidate but since I have no experience with mosfets so far I'd appreciate a second opinion :wink:

Thanks a lot!
Tom

The IRFD024 is not a good choice IMHO because its gate charge (Qg) is 25nC, or about 5 times higher than the MOSFET I recommended. Ballpark, it'll take 5 times longer for it to switch on and off.

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You are right, unfortunately the one you recommended isn't available from my supplier.

But I think I found a reasonable alternative: HTTP 301 This page has been moved
Not quite as fast as and low Qg than the STP27N3LH5 but almost, would you agree?

Meh...that's a 1.5 ohm MOSFET. That's pretty high and will get very warm if carrying ~1A of current.

If you're constrained by a particular supplier, let us know what that is and perhaps we can work around this constraint.

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I guess with such a short pulse, using multiple parallel mosfets (that are available), isn't an option?

Darn, I didn't check the resistance you are right.

I am currently living in Germany and will be ordering from voelkner.de in the next few days.
If I could find a driver and mosfet there that would be great.
Unfortunately their assortment isn't too big, so conrad.de might be the alternative.

They both seem to carry a lot of transistors by "International Rectifier" so I'm now trying to find suitable mosfet from them, but no luck so far.

Dave:
I have no idea since I haven't worked with mosfets so far, but wouldn't parallel mosfets actually increase the total gate capacitance and thus be even slower?!

I was thinking in terms of charging say 4 in parallel would be quicker than 1 large gate. Finding suitable mosfets for the job isn't trivial though :~
In terms of mosfet top trumps - the item that RuggedCircuits posted (STP27N3LH5) is pretty hard to beat.... I'm currently trying to design an utterly indestructible H Bridge (it's taking me forever). I think I might use a number of those.

You are right, if you want fast, well-defined pulses you will want a combination of a low gate capacitance MOSFET and high-current MOSFET driver, like a Microchip TC4426A.

Not necessarily, for an amp or so a MOSFET driver chip is sufficient in itself (and much faster) - the MIC4422 for instance will drive several amps and has logic level input. For a low-duty cycle application this will do without further boosting (not much power dissipation required).

That's a very interesting idea Mark, thanks for pointing it out!

Gentelmens,
My question is the same you are interesting above.
For Senior Design project, ı have to design DC/DC buck converter. To drive the MOSFET in the circuit. I added GATE DRİVER and BUFFER to protect the GATE Driver IC. to send a PWM signal 50kHz to the Buffer.
But I do not know how to design codes for PWM cycle at 50kHz on Arduıno.

If you want to circuit, arduıno paltform.JPG - Google Drive

Well, I think you need to explain for a start, what part an Arduino would have in a buck converter. These are totally different functions, I doubt anyone here could see any way they would be related. :astonished:

I doubt anyone here could see any way they would be related

FOD8316 2.5A IGBT Optocoupler

VIN+ Non-inverting Gate Drive Control Input

@OP,
So where is the rest of your buck converter schematic ?

(All you posted was the IGBT driver circuit)

But I do not know how to design codes for PWM cycle at 50kHz on Arduıno.

Have a look at this

For starters, consider the brute force bit banging approach (for the sake of discussion):

Let f = 50kHz

period = 1/50000 = 0.000020 sec = 20uS

Let duty cycle = 10%

0.1 * 0.000020 sec = 0.000002 sec (2 uS)

void setup()
{
pinMode(13, OUTPUT);
}

void loop()
{
digitalWrite(13, HIGH);
delayMicroseconds(2); // Approximately 10% duty cycle @ 50KHz
digitalWrite(13, LOW);
delayMicroseconds(18);
}

delayMicroseconds()

Notes and Warnings

This function works very accurately in the range 3 microseconds and up. We cannot assure that delayMicroseconds will perform precisely for smaller delay-times.

(What does this mean ? It means you have to experiment with the delay times using a scope to see
if it is possible to achieve the desired timing)

and then there's Fast PWM:

Fast PWM Mode

The following code fragment sets up fast PWM on pins 3 and 11 (Timer 2). To summarize the register settings, setting the waveform generation mode bits WGM to 011 selects fast PWM. Setting the COM2A bits and COM2B bits to 10 provides non-inverted PWM for outputs A and B. Setting the CS bits to 100 sets the prescaler to divide the clock by 64. (Since the bits are different for the different timers, consult the datasheet for the right values.) The output compare registers are arbitrarily set to 180 and 50 to control the PWM duty cycle of outputs A and B. (Of course, you can modify the registers directly instead of using pinMode, but you do need to set the pins to output.)

pinMode(3, OUTPUT);
pinMode(11, OUTPUT);
TCCR2A = _BV(COM2A1) | _BV(COM2B1) | _BV(WGM21) | _BV(WGM20);
TCCR2B = _BV(CS22);
OCR2A = 180;
OCR2B = 50;

TomS:
I know what you mean, but I think that there will be differences regarding precision and range of the sensor when using differently modulated pulses.

If they are significant enough to be useful is a question we can only find out by testing it - which is what I'd like to do.

So what I would need is a mosfet with very low gate capacitance or some kind of driver to switch it right?

No, just a MOSFET driver chip is all thats' needed to do this, try a MIC4422 powered from 5V, its internal
resistance will be a few ohms, might be enough by itself to act as LED current limit. These chips
can switch plenty fast enough, and with a low duty cycle heat dissipation isn't a problem.

Be sure to use plenty of ceramic decoupling on the MIC4422, right next to the pins. At least 1uF.

@Mark,
You just answered a post from 2011. (by repeating your post of Jun 1st, 2011)

The latest post is reply #21 (Dec 2nd, 2018)

Doh, scrolled to end of page 1 and didn't notice the next page!