H-Bridge DC motor driver - Page 3 - Electronic Circuits Projects Diagrams Free

hjames · 10th March 2007, 09:05 AM

Quote:

Originally Posted by Generalx5

Should you have any questions Please don't hesitate to contact me Via Email

Jun Zheng,
Gr 12 Senior Engineering Student.
David Thompson Secondary
Vancouver BC. Canada
FIRST Robotics member
Team # 1346

I created an account when I read thru this havoc, I felt frustrated hahaa...the need to answer ppls questions!

There are a rather large number of not-quite-right statements in this comment...

Hero999 · 10th March 2007, 10:23 AM

Quote:

Originally Posted by Generalx5

P type MOSFETs when grounded or LOW at the gates they will turn On.(Yes, it would blow up if there is no resistance at the Gate)

Whilst ture in the configureation you've described it's a gross over-simplification. The MOSFETs only turn on because the gate is pulled below the source by 10V or so.

For both N and P channel MOSFETs you need to be careful not to distroy the gates if the power supply can be >20V.

Quote:

This is traditionally used so that you will never have a SHOOT thru, or shorting out the H BRIDGE, Even a Micro second will hurt your circuity at high frequencise.

Why are you worrying about that?

Providing there are never two MOSFETs on either side on at the same time it doesn't matter.

Quote:

I would Prefere to use N-TYPE MOSFETS ONLY Because they have a significantly higher Amp rating than P-Type mosfets,

So do I.

Quote:

You can do this with just the same, but You will need to use A LOGIC INVERTER, Hex invert. You would have 1 incomming signal either high or low, and the signals will divert to the MOSFET DRIVER that operates the top of the MOSFETS according to the generic diagrams, and the other signal is diverted into the LOGIC Inverters. The output on the Logic Inverters will then reach a second MOSFET DRIVER that drives the bottom set of MOSFETS.

Your logic inverter is totally useless if it doesn't pull the gate and the high side MOSFETs above the positive rail by about 10V. You need bootstrap capacitor (only works with PWM) or a secondary higher supply voltage to switch the high side MOSFETs porberly.

Quote:

This works well because only the Bottom ROW of MOSFETS Give off Heat, as the bottom row will turn on slower due to the Lagg from the Logic gates. This is also very efficient because it also has no chance of shooting thru. Due to the lag in the Logic Gates.

That's nonsense!

If all the MOSFETS have the same part number they'll all disipate a similar amount of heat providing they're driven correctly.

Quote:

I would also stay away from PWM signaling. Instead I would use a linear Voltage regulator. This is because PWM constantly turns on and off the MOSFETS, these switching times are turned into wasted energy in forms of Heat.

Rubbish!

Linear regulation produces more far heat than PWM; the whole point of PWM is to save energy!

Whyt do you think switching regulators are more efficient thatn linear regulators? Because they don't dissipate loads of energy in VI losses!

Quote:

I would recommend setting up several N type MOSFETS, 12 is a good number in parallel so you reduce the load on each MOSFET and dissapate Heat better. Also for better reliability.

True but how big is your motor?

Does it drive a small care or something?

Perhaps you've only needed to use so many MOSFETs because you've used crappy linear regulation and therefore had to dissipate loads of energy?

Quote:

I use IRF3704ZPBF N-TYPE MOSFETS from International Rectifyer? (47Amps at 25C temp / 56Amps at 100C also PBF means Lead Free)

That will give you an enormous 672A capacity! Using a 12V battery it can potentially drive a 8kW motor - more than enough power for a reasonable size golf buggy.

Quote:

This is the one I use because it has a fast Switching time, and low Gate Resistance. But it is limited to 18 volts maximum, You should search up on their website for a higher voltage rating up to 1000V MOSFETS.

The datasheet says 20V but I accept that the practicvle voltage will be lower; 18V seems a reasonable limit to me.

Quote:

As for MOSFET DRIVERS I used with my IRF3704Z a pair of TC4426PBF(Leadfree) Mosfet Drivers that provides 1.5Amps of Current for the MOSFET Gate if needed in case the Gate resistance is high. The MOS Drivers are also PDIP =D

With the best will in the world they still won't drive high side MOSFETs without a higher than VDD power supply though.

Quote:

On my H-Bridge, I had 2 resistors hooked up to the H Bridge so that there is resistance between Gate to Source and Gate to Drain. This way, when power is off, any noise or watever will not damage your motor, Or if the signal is somehow borken or not getting thru, the H-Bridge simply wont turn on. The resistance cant be too big or else it will reduce the effects of the MOSFET Driver(in other words, increase the load on the MOSFET drivers which makes respond slower.

Pease post the schematic.

Quote:

Should you have any questions Please don't hesitate to contact me Via Email

Posting your email on the Internet isn't a good idea unless you want to recieve a load of spam.

By the way welcome to the forum. Please don't be discouraged by any of the criticisms I've made about your post; it's nothing personal.

MrNobody · 13th March 2007, 02:32 PM

Hi..
Here is a simulation of the H-Bridge circuit.
I am using both P type and N type MOSFET..

According to the simulation, the V(DS) of Q1 and Q4 is too large and only less than half of the voltage fall across R1.

Too much power loss and too little power reach the motor..

I did not capture the voltage of V(GS) but it is already close to -30V and that is the max it can go..

Any idea why it won't fully turn on..? And how can i make the power loss less..?

Hero999 · 15th March 2007, 08:37 PM

But the maximum gate voltage is 20V so thehe p-channel MOSFETS will be distroyed.

What's the value of R1?

audioguru · 15th March 2007, 09:19 PM

The 2N2222 transistors don't have base resistors so the one with 12V between its base and its emitter is destroyed.

Hero999 · 15th March 2007, 09:33 PM

I knew there was something I had missed.

I'm not too sure about those 1k resistors either, they're fine if you want just forward and reverse but you might have a prolem with PWM as they will slow down the switching speed of the MOSFETs.

Roff · 15th March 2007, 10:24 PM

I'm guessing he just picked a couple of MOSFET types at random from his selection of models. Did anyone else look at the specs on those parts? I did, a couple of days ago, and IIRC, the PMOS was in a TO-3 pkg and the NMOS was in something like a TO-92, and has 35V VDS breakdown and Ron of around 3 ohms. I could be wrong - I was once before.

MrNobody · 16th March 2007, 01:13 PM

Quote:

Originally Posted by Hero999

But the maximum gate voltage is 20V so thehe p-channel MOSFETS will be distroyed.

What's the value of R1?

Yeah, I just picked one MOSFET from Multisim. Couldn't find the model that I am using in there.. Anyway, I tried with smaller voltage and it functions well using 2N6804 in Multisim..

Anyway, the one I use, the V(GSmax) is 30V..
I tried it with 12V supply and it works well.. Haven't tested it yet with 60V..

The value of R1 is 5Ohm.. That is the resistance of the motor (measured with Ohmmeter.)

Quote:

Originally Posted by audioguru

The 2N2222 transistors don't have base resistors so the one with 12V between its base and its emitter is destroyed.

I added a 100 Ohm resistor to the base of the NPN transistor and supplied it with 5V. It turns on well.. At first, I put 1 Meg resistor (over protective of the NPN) and that thing wont turn on at all.. Spent hours trying to figure out why it won't work.. Thought i connected it wrongly and things like that.. Finally my friend tried 100 Ohm resistor and it worked perfectly..

Quote:

Originally Posted by Hero999

I'm not too sure about those 1k resistors either, they're fine if you want just forward and reverse but you might have a prolem with PWM as they will slow down the switching speed of the MOSFETs.

The 1K resistor, (I presume u meant R2, R3, R5, R6) is just to keep the V(GS) below the V(GSmax).
Since you don't recommend me doing that, how should I make it effecient for PWM and at the same time limit the V(GS)..?

Hero999 · 16th March 2007, 05:37 PM

Quote:

Originally Posted by MrNobody

Yeah, I just picked one MOSFET from Multisim. Couldn't find the model that I am using in there.. Anyway, I tried with smaller voltage and it functions well using 2N6804 in Multisim..

Neither of the MOSFETs have high enough current ratings, the 2N6659 is rated for only 1.4A and the IRF9130 is only rated to 11A and your 5

hm: resistor will try to pull 12A from 60V.

Quote:

Anyway, the one I use, the V(GSmax) is 30V..
I tried it with 12V supply and it works well.. Haven't tested it yet with 60V..

Look at the datasheet (which can be found using Google); it's rated for +-20V.

Quote:

The value of R1 is 5Ohm.. That is the resistance of the motor (measured with Ohmmeter.)

That will just give you the resistance when it starts, the running resistance will be a lot higher.

Quote:

The 1K resistor, (I presume u meant R2, R3,$R5, R6) is just to keep the V(GS) below the V(GSmax).
Since you don't recommend me doing that, how should I make it effecient for PWM and at the same time limit the V(GS)..?

Switching high side MOSFETs when the power supply is higher than 20V is a pain. For fast switching times, you want to be able to discharge the input capacitance as quickly as possible; you can buy special driver ICs for this.

MrNobody · 17th March 2007, 12:59 AM

Quote:

Originally Posted by Hero999

Neither of the MOSFETs have high enough current ratings, the 2N6659 is rated for only 1.4A and the IRF9130 is only rated to 11A and your 5

hm: resistor will try to pull 12A from 60V.

Yeah.. I will add 100 Ohm resistor there to limit the current..

Quote:

Originally Posted by Hero999

That will just give you the resistance when it starts, the running resistance will be a lot higher.

Just wondering, how can the resistance increase after it starts..? Isn't that the resistance of the coil..? I dunno much about construction of the motor..

Quote:

Originally Posted by Hero999

Switching high side MOSFETs when the power supply is higher than 20V is a pain. For fast switching times, you want to be able to discharge the input capacitance as quickly as possible; you can buy special driver ICs for this.

When you say the input capacitance, u mean the capacitance of gate-source and gate-drain..? As for purchasing the special driver IC, we're kinda on a tight budget... Thanks.... Hmm, if I use 1Mega Ohm resistor, that would certainly speed up the charging and discharging time of the capacitance rite (theoritically)..?

Hero999 · 17th March 2007, 01:31 AM

Quote:

Originally Posted by MrNobody

Just wondering, how can the resistance increase after it starts..? Isn't that the resistance of the coil..? I dunno much about construction of the motor..

Perhaps I haven't worded that very well. When you spin a motor it generates a voltage. The same is ture when it's connected to a power supply except the voltage counteracts the current from the power supply. For exampe if your motor generates 50V when spun at the maximum speed, it will draw (60-50) / 5 = 2A when powered from 60V.

Quote:

When you say the input capacitance, u mean the capacitance of gate-source and gate-drain..?

[quote] As for purchasing the special driver IC, we're kinda on a tight budget...

Quote:

Thanks.... Hmm, if I use 1Mega Ohm resistor, that would certainly speed up the charging and discharging time of the capacitance rite (theoritically)..?

You've got that backwards, you need to reduce the resistor value, remember the RC time constant. To get the real answer to this question, look at the datasheet then figure out how long it will take for the gate capacitance to charge to the voltage that will alow the desired current to flow to work out the switching speed.

MrNobody · 17th March 2007, 03:19 AM

Quote:

Originally Posted by Hero999

Perhaps I haven't worded that very well. When you spin a motor it generates a voltage. The same is ture when it's connected to a power supply except the voltage counteracts the current from the power supply. For exampe if your motor generates 50V when spun at the maximum speed, it will draw (60-50) / 5 = 2A when powered from 60V.

You've got that backwards, you need to reduce the resistor value, remember the RC time constant. To get the real answer to this question, look at the datasheet then figure out how long it will take for the gate capacitance to charge to the voltage that will alow the desired current to flow to work out the switching speed.

Ok... thanks very much.. will look into it..

wailyounis · 16th August 2008, 07:10 AM

Hey..
I need help in designing H bridge motor driver circuit to drive a DC permanent motor using N-MOSFET.

The motor specs are:
Type: dc permanent magnet motor.
Voltage rating: 24 Volts dc
Power: 250W

I need help.. Can somebody please help me.. Thanks..

Hero999 · 16th August 2008, 11:34 AM

I will help you but you need to read this entire thread and make an attempt at designing it for yourself before I help you.

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15th March 2007, 08:37 PM	(permalink)
Hero999	But the maximum gate voltage is 20V so thehe p-channel MOSFETS will be distroyed. What's the value of R1? __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

15th March 2007, 09:19 PM	(permalink)
audioguru	The 2N2222 transistors don't have base resistors so the one with 12V between its base and its emitter is destroyed. __________________ Uncle $crooge

15th March 2007, 09:33 PM	(permalink)
Hero999	I knew there was something I had missed. I'm not too sure about those 1k resistors either, they're fine if you want just forward and reverse but you might have a prolem with PWM as they will slow down the switching speed of the MOSFETs. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

15th March 2007, 10:24 PM	(permalink)
Roff	I'm guessing he just picked a couple of MOSFET types at random from his selection of models. Did anyone else look at the specs on those parts? I did, a couple of days ago, and IIRC, the PMOS was in a TO-3 pkg and the NMOS was in something like a TO-92, and has 35V VDS breakdown and Ron of around 3 ohms. I could be wrong - I was once before. __________________ Ron (aka Rube)

16th August 2008, 07:10 AM	(permalink)
wailyounis	Hey.. I need help in designing H bridge motor driver circuit to drive a DC permanent motor using N-MOSFET. The motor specs are: Type: dc permanent magnet motor. Voltage rating: 24 Volts dc Power: 250W I need help.. Can somebody please help me.. Thanks..

16th August 2008, 11:34 AM	(permalink)
Hero999	I will help you but you need to read this entire thread and make an attempt at designing it for yourself before I help you. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.