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'[EE]:High power DC switching..'
2002\04\13@111745 by Kevin Howell

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face
I have some high power fast switching transistors, BUV48, which I want to
use to control a 220V DC motor using PWM. The transistor can handle 10A Ic
and 400 Vce (hfe =8!!). My problem is that the motor draws up to 20A and
thus I will
need more than one of these transistors in possibly a darlington
configuration. Please can someone help me with a circuit to control this
current hungry motor using a pic ...

Regards
Kevin Howell

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2002\04\13@124433 by Bob Blick

face picon face
> I have some high power fast switching transistors, BUV48, which I want to
> use to control a 220V DC motor using PWM. The transistor can handle 10A Ic
> and 400 Vce (hfe =8!!). My problem is that the motor draws up to 20A and
> thus I will
> need more than one of these transistors in possibly a darlington
> configuration. Please can someone help me with a circuit to control this
> current hungry motor using a pic ...

Hi Kevin,

Do you really have to use this transistor? Do you already have some
other transistors to use as drivers for them? If not, perhaps you
should consider some other transistors, I would suggest MOSFETs.
Your losses will generally be lower. Also if you do PWM you will
need a freewheel diode across the motor.

Others will likely also have suggestions. A transistor with hfe of 8
doesn't sound like a whole lot of fun.

Cheers,

Bob

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2002\04\13@142542 by Kevin Howell

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I can't find any Mosfets that can handle 200-300V. The problem is not to
source them but to find a suitable part. (Keep in mind the 20A)

Thanks
Kevin


{Original Message removed}

2002\04\13@142815 by Kevin Howell

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face
I forgot to ask you what the freewheel diode is for...


-----Original Message-----
From: pic microcontroller discussion list
[spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU]On Behalf Of Bob Blick
Sent: 13 April 2002 06:44 PM
To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
Subject: Re: [EE]:High power DC switching..


> I have some high power fast switching transistors, BUV48, which I want to
> use to control a 220V DC motor using PWM. The transistor can handle 10A Ic
> and 400 Vce (hfe =8!!). My problem is that the motor draws up to 20A and
> thus I will
> need more than one of these transistors in possibly a darlington
> configuration. Please can someone help me with a circuit to control this
> current hungry motor using a pic ...

Hi Kevin,

Do you really have to use this transistor? Do you already have some
other transistors to use as drivers for them? If not, perhaps you
should consider some other transistors, I would suggest MOSFETs.
Your losses will generally be lower. Also if you do PWM you will
need a freewheel diode across the motor.

Others will likely also have suggestions. A transistor with hfe of 8
doesn't sound like a whole lot of fun.

Cheers,

Bob

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2002\04\13@144839 by Dave King

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At 08:26 PM 4/13/02 +0200, you wrote:
>I can't find any Mosfets that can handle 200-300V. The problem is not to
>source them but to find a suitable part. (Keep in mind the 20A)
>
>Thanks
>Kevin

You didn't happen to run across anything that might handle about 150-200A? ;-]

I just got asked if I could build a controller for a older electric car. It
uses a big
honking (technical electrical car term ....) stainless steel coil that
operate as a
cross between a rheostat and a heat sink. Very inefficient to say the least.

Dave

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2002\04\13@145738 by Bob Blick

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> I forgot to ask you what the freewheel diode is for...

Hi Kevin,

When your transistor turns off, there is energy stored as inductance in
the circuit(primarily in the motor) that must be directed somewhere.
Otherwise it will turn into a huge voltage and kill your transistor. So
the freewheel diode conducts that energy back into the motor.

There are plenty of MOSFETs capable of 400 volts, you might need two or
three of them in parallel. Digi-Key is a good source of IR parts in the
US, don't know what you have there but there are other manufacturers.

You will need something (simple) to drive them from a PIC.

Big electric car motor controllers typically use a dozen or so MOSFETs in
parallel, also a dozen or so freewheel diodes. And a few Big capacitors
across the supply, not optional!

Cheers,

Bob

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2002\04\13@153548 by Kevin Howell

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Wow!! unfortunately not...



-----Original Message-----
From: pic microcontroller discussion list
[PICLISTspamKILLspamMITVMA.MIT.EDU]On Behalf Of Dave King
Sent: 13 April 2002 08:46 PM
To: .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
Subject: Re: [EE]:High power DC switching..


At 08:26 PM 4/13/02 +0200, you wrote:
>I can't find any Mosfets that can handle 200-300V. The problem is not to
>source them but to find a suitable part. (Keep in mind the 20A)
>
>Thanks
>Kevin

You didn't happen to run across anything that might handle about 150-200A?
;-]

I just got asked if I could build a controller for a older electric car. It
uses a big
honking (technical electrical car term ....) stainless steel coil that
operate as a
cross between a rheostat and a heat sink. Very inefficient to say the least.

Dave

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2002\04\13@161955 by Kevin Howell

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I managed to find one just as I received your message!!!

The IRF740 from Fairchild is a logic level MOSFET capable of handling 400V
at 10A! Two or three of these and I am sorted! (I think) Seeing that they
are logic level can I just use a opto isolator in between the PIC and the
MOSFET or not?

Something else bothers me a bit. I have just read through the spec of the
motor and I don't think this motor can handle more than 220V DC. Our mains
supply is 220V Ac. Putting that through a bridge rectifier and a cap will
probably push it to 320 V DC!! which is miles to much. What can I do to get
this down to around 200V DC again?

Thanks,

Kevin


{Original Message removed}

2002\04\13@162433 by PY2NI

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face
   As a starting device try 2 or more IRF 740 (400V @ 10A each) you have
better options if you don't put more than 200V on the FET you can use only 2
IRF 640 (200V  @ 18A each). MOSFets are really friendly devices when you pay
attention on how to handle then, especial care with driver circuits, some of
then  have quite a large input capacitive reatance. Cgs. There are especial
ICs (GATE DRIVERS) designed to deal with this problem if you don't want to
waste your time doing this.
   Hope it helps a bit.

P.S. the devices mentioned aren't expensive, I often buy then for  a buck or
less.

[ ] s
Horta


----- Original Message -----
From: Kevin Howell <EraseMEkevinspam_OUTspamTakeThisOuTRECORD.CO.ZA>
To: <PICLISTspamspam_OUTMITVMA.MIT.EDU>
Sent: Saturday, April 13, 2002 3:26 PM
Subject: Re: [EE]:High power DC switching..


> I can't find any Mosfets that can handle 200-300V. The problem is not to
> source them but to find a suitable part. (Keep in mind the 20A)
>
> Thanks
> Kevin
>
>
> {Original Message removed}

2002\04\13@162628 by Bob

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face
Have you taken a look at IGBT's?


-----Original Message-----
From: Kevin Howell <@spam@kevinKILLspamspamRECORD.CO.ZA>
To: KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU <RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU>
Date: Saturday, April 13, 2002 10:16 AM
Subject: [EE]:High power DC switching..


{Quote hidden}

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2002\04\13@162813 by M. Adam Davis

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Most of these use parallel, matched mosfets.  There are homebrew
electric cars on the net - most of them stick with manufactured
controllers, but some have built their own.  One recently mentioned (I
think on this list since he's using a pic) uses two very large DC motors...

Google for it.  (I love when a company name becomes a verb!)

-Adam

Dave King wrote:

{Quote hidden}

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2002\04\13@164518 by Kevin Howell

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Thanks...


-----Original Message-----
From: pic microcontroller discussion list
[spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU]On Behalf Of M. Adam Davis
Sent: 13 April 2002 10:25 PM
To: TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU
Subject: Re: [EE]:High power DC switching..


Most of these use parallel, matched mosfets.  There are homebrew
electric cars on the net - most of them stick with manufactured
controllers, but some have built their own.  One recently mentioned (I
think on this list since he's using a pic) uses two very large DC motors...

Google for it.  (I love when a company name becomes a verb!)

-Adam

Dave King wrote:

{Quote hidden}

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2002\04\13@171157 by Kevin Howell

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Thanks I found the datasheet on the IRF740, I didn't know that there are
inherent problems when driving a MOSFET (Cgs) . Now the search is on for a
mosfet driver. Can't the IRF740 b interfaced directly to a PIC? Surely it
was designed with a microcontroller in mind?

Thanks
Kevin

{Original Message removed}

2002\04\13@171203 by Kevin Howell

flavicon
face
I managed to find one just as I received your message!!!

The IRF740 from Fairchild is a logic level MOSFET capable of handling 400V
at 10A! Two or three of these and I am sorted! (I think) Seeing that they
are logic level can I just use a opto isolator in between the PIC and the
MOSFET or not?

Something else bothers me a bit. I have just read through the spec of the
motor and I don't think this motor can handle more than 220V DC. Our mains
supply is 220V Ac. Putting that through a bridge rectifier and a cap will
probably push it to 320 V DC!! which is miles to much. What can I do to get
this down to around 200V DC again?

Thanks,

Kevin

{Original Message removed}

2002\04\13@172420 by Rick C.

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face
Try Microchip (believe it or not)
www.telcom-semi.com/products/datasheets/tc426_8.pdf
I believe Microchip bought Telcom to add to their line.
Rick

Kevin Howell wrote:

> Thanks I found the datasheet on the IRF740, I didn't know that there are
> inherent problems when driving a MOSFET (Cgs) . Now the search is on for a
> mosfet driver. Can't the IRF740 b interfaced directly to a PIC? Surely it
> was designed with a microcontroller in mind?
>
> Thanks
> Kevin
>
> {Original Message removed}

2002\04\13@172635 by John Dammeyer

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face
Use a transistor circuit.  A while ago I posted a link to my Casting
Furnce controller

http://www.pacificsun.ca/~john/pdf-files/Furnace.pdf

There's your control for driving the FET.

John


> {Original Message removed}

2002\04\13@173126 by Rick C.

flavicon
face
PS Digikey stocks the TC427/428
TC427CPA-ND, TC428CPA-ND $1.63 ea
Rick

Kevin Howell wrote:

> Thanks I found the datasheet on the IRF740, I didn't know that there are
> inherent problems when driving a MOSFET (Cgs) . Now the search is on for a
> mosfet driver. Can't the IRF740 b interfaced directly to a PIC? Surely it
> was designed with a microcontroller in mind?
>
> Thanks
> Kevin
>
> {Original Message removed}

2002\04\13@173948 by Olin Lathrop

face picon face
> I have some high power fast switching transistors, BUV48, which I want to
> use to control a 220V DC motor using PWM. The transistor can handle 10A Ic
> and 400 Vce (hfe =8!!). My problem is that the motor draws up to 20A and
> thus I will
> need more than one of these transistors in possibly a darlington
> configuration. Please can someone help me with a circuit to control this
> current hungry motor using a pic ...

This is the kind of thing that if you need to ask about you shouldn't be
messing with.  You can't just parallel bipolar transistors because they
won't share the current equally.  The current imbalance is actually
amplified by the thermal characteristics.  This is usually dealt with by
giving each transistor its own emitter resistor.  100mOhms might be OK in
your case.  That can be implemented by a measured length of the right wire.
I don't like darlington for this because of the larger voltage accross the
transistors when on.  At 10A that makes quite a few watts of difference.  If
you are really stuck on these transistors, I would use at least 3 of them
and give them good heat sinks.  The base drive circuit alone will need to
switch over 3A.

Again, there are lots of issues here.  Get someone to do this that knows
what they are doing.


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2002\04\13@175035 by Olin Lathrop

face picon face
> Do you really have to use this transistor? Do you already have some
> other transistors to use as drivers for them? If not, perhaps you
> should consider some other transistors, I would suggest MOSFETs.
> Your losses will generally be lower.

High voltage MOSFETs tend to have much higher on resistance than the low
voltage one you are probably more used to.  At 300V off and 10A on a bipolar
power transistor may very well have a lower on voltage.


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2002\04\13@180450 by Kevin Howell

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Thank you...


-----Original Message-----
From: pic microcontroller discussion list
[RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU]On Behalf Of Rick C.
Sent: 13 April 2002 11:26 PM
To: PICLISTEraseMEspam.....MITVMA.MIT.EDU
Subject: Re: [EE]:High power DC switching..


Try Microchip (believe it or not)
www.telcom-semi.com/products/datasheets/tc426_8.pdf
I believe Microchip bought Telcom to add to their line.
Rick

Kevin Howell wrote:

{Quote hidden}

pay
> attention on how to handle then, especial care with driver circuits, some
of
> then  have quite a large input capacitive reatance. Cgs. There are
especial
> ICs (GATE DRIVERS) designed to deal with this problem if you don't want to
> waste your time doing this.
>     Hope it helps a bit.
>
> P.S. the devices mentioned aren't expensive, I often buy then for  a buck
or
{Quote hidden}

10A
> Ic
> > > and 400 Vce (hfe =8!!). My problem is that the motor draws up to 20A
and
> > > thus I will
> > > need more than one of these transistors in possibly a darlington
> > > configuration. Please can someone help me with a circuit to control
this
{Quote hidden}

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2002\04\13@180516 by Kevin Howell

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Fantastic , I was hoping it would be that simple...

Regards
Kevin


-----Original Message-----
From: pic microcontroller discussion list
[PICLISTSTOPspamspamspam_OUTMITVMA.MIT.EDU]On Behalf Of John Dammeyer
Sent: 13 April 2002 11:29 PM
To: spamBeGonePICLISTSTOPspamspamEraseMEMITVMA.MIT.EDU
Subject: Re: [EE]:High power DC switching..


Use a transistor circuit.  A while ago I posted a link to my Casting
Furnce controller

http://www.pacificsun.ca/~john/pdf-files/Furnace.pdf

There's your control for driving the FET.

John


{Quote hidden}

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2002\04\13@181442 by Kevin Howell

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Something else bothers me a bit. I have just read through the spec of the
motor and I don't think this motor can handle more than 220V DC. Our mains
supply is 220V Ac. Putting that through a bridge rectifier and a cap will
probably push it to 320 V DC!! which is miles to much. What can I do to get
this down to around 200V DC again?

{Original Message removed}

2002\04\13@182047 by David Harris

picon face
Hi-
You could use a half-bridge rectifier -- two diodes instead of four.
David

Kevin Howell wrote:

> Something else bothers me a bit. I have just read through the spec of the
> motor and I don't think this motor can handle more than 220V DC. Our mains
> supply is 220V Ac. Putting that through a bridge rectifier and a cap will
> probably push it to 320 V DC!! which is miles to much. What can I do to get
> this down to around 200V DC again?
>
> {Original Message removed}

2002\04\13@195716 by Olin Lathrop

face picon face
> > Something else bothers me a bit. I have just read through the spec of
the
> > motor and I don't think this motor can handle more than 220V DC. Our
mains
> > supply is 220V Ac. Putting that through a bridge rectifier and a cap
will
> > probably push it to 320 V DC!! which is miles to much. What can I do to
get
> > this down to around 200V DC again?
>
> You could use a half-bridge rectifier -- two diodes instead of four.

You could, but you'd still end up with the same maximum voltage.  It would
just droop more between the peaks.


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2002\04\13@233311 by Sean H. Breheny

face picon face
Hi Olin,

I think he means a full wave rectifier using two diodes and a center-tapped
transformer, to give half voltage.

Sean

At 07:55 PM 4/13/02 -0400, you wrote:
{Quote hidden}

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2002\04\14@005116 by Code

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face
you'll need a MOS driver that's capable of driving large capacitive load

http://www.national.com/pf/DS/DS0026.html


----- Original Message -----
From: "Kevin Howell" <RemoveMEkevinspamspamBeGoneRECORD.CO.ZA>
To: <spamBeGonePICLIST@spam@spamspam_OUTMITVMA.MIT.EDU>
Sent: Sunday, April 14, 2002 5:13 AM
Subject: Re: [EE]:High power DC switching..


> Thanks I found the datasheet on the IRF740, I didn't know that there are
> inherent problems when driving a MOSFET (Cgs) . Now the search is on for a
> mosfet driver. Can't the IRF740 b interfaced directly to a PIC? Surely it
> was designed with a microcontroller in mind?
>
> Thanks
> Kevin
>
> {Original Message removed}

2002\04\14@012211 by Kevin Howell

flavicon
face
I am not using a transformer, I'm using our mains supply which is 220VAC...

Question: Will the very nature of PWM on the motor not cause the average
voltage to drop below the accepted range in any case? Then I just have to
make sure I don't switch the motor on at 100% duty cycle.

Thanks!
Kevin


{Original Message removed}

2002\04\14@012229 by Kevin Howell

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face
Does that mean I won't get away with a 2N2222 or a opto-isolator between the
PIC and the MOSFET?


-----Original Message-----
From: pic microcontroller discussion list
[TakeThisOuTPICLISTspamspamMITVMA.MIT.EDU]On Behalf Of Code
Sent: 14 April 2002 06:50 AM
To: PICLISTEraseMEspamMITVMA.MIT.EDU
Subject: Re: [EE]:High power DC switching..


you'll need a MOS driver that's capable of driving large capacitive load

http://www.national.com/pf/DS/DS0026.html


----- Original Message -----
From: "Kevin Howell" <RemoveMEkevinEraseMEspamspam_OUTRECORD.CO.ZA>
To: <@spam@PICLISTRemoveMEspamEraseMEMITVMA.MIT.EDU>
Sent: Sunday, April 14, 2002 5:13 AM
Subject: Re: [EE]:High power DC switching..


{Quote hidden}

pay
> attention on how to handle then, especial care with driver circuits, some
of
> then  have quite a large input capacitive reatance. Cgs. There are
especial
> ICs (GATE DRIVERS) designed to deal with this problem if you don't want to
> waste your time doing this.
>     Hope it helps a bit.
>
> P.S. the devices mentioned aren't expensive, I often buy then for  a buck
or
{Quote hidden}

10A
> Ic
> > > and 400 Vce (hfe =8!!). My problem is that the motor draws up to 20A
and
> > > thus I will
> > > need more than one of these transistors in possibly a darlington
> > > configuration. Please can someone help me with a circuit to control
this
{Quote hidden}

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2002\04\14@023551 by Kevin Howell

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face
I am just wondering whether it would not be better to do some sort of AC
detection + PWM on the mains power 220VAC and then just rectify it to be
used for the DC motor. That will sort out my problem with the DC voltage
being too high. Isn't there an APPnote about this somewhere on the Microchip
website?


Proposed circuit:


   220VAC ---------> PWM -------> rectifier -------->DC Motor
                      |
                            |
                            |
                         Pic uC


Thanks

Kevin



{Original Message removed}

2002\04\14@043221 by Code

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face
A properly designed driver using discrete components would of course work
good. However, when driving a larger gate charge, a specialized MOS driver
would ensure that the MOSFET gets fully switched ON.

Do also take note that the IRF740 has a higher gate charge than other lower
current, voltage mosfet.

Tan Chun Chiek
----- Original Message -----
From: "Kevin Howell" <.....kevinRemoveMEspamRECORD.CO.ZA>
To: <.....PICLISTSTOPspamspam@spam@MITVMA.MIT.EDU>
Sent: Sunday, April 14, 2002 1:26 PM
Subject: Re: [EE]:High power DC switching..


> Does that mean I won't get away with a 2N2222 or a opto-isolator between
the
> PIC and the MOSFET?
>
>
> {Original Message removed}

2002\04\14@100052 by Olin Lathrop

face picon face
> I am not using a transformer, I'm using our mains supply which is
220VAC...
>
> Question: Will the very nature of PWM on the motor not cause the average
> voltage to drop below the accepted range in any case? Then I just have to
> make sure I don't switch the motor on at 100% duty cycle.

It depends on what the limiting factor of the high voltage spec is.  If it
is based on dielectric strength or arc distance, then you can't do what you
are thinking.  If it is to prevent the motor from drawing too much current
and therefore heating up too much (this is more likely), then you can
compensate with PWM that never exceeds a certain duty cycle.


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2002\04\14@100251 by Olin Lathrop

face picon face
> Does that mean I won't get away with a 2N2222 or a opto-isolator between
the
> PIC and the MOSFET?

Yup.


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2002\04\14@122653 by John Dammeyer

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Sorry,  I disagree and the fact that I am reliably switching 10A through
the IRF series of FETs with a 2N2222A bears that out quite nicely.  I do
agree that a driver is better.  Certainly if you attend one of the
Microchip seminars where they talk about their FET driver product you'd
walk away convinced.  For the FETS that require a full 12V to switch I
do agree you need a decent proper driver but the 5V switched FETs don't
have the same gate capacitance.

John Dammeyer


> {Original Message removed}

2002\04\14@130532 by Spehro Pefhany

picon face
At 09:30 AM 4/14/02 -0700, you wrote:
>Sorry,  I disagree and the fact that I am reliably switching 10A through
>the IRF series of FETs with a 2N2222A bears that out quite nicely.  I do
>agree that a driver is better.  Certainly if you attend one of the
>Microchip seminars where they talk about their FET driver product you'd
>walk away convinced.  For the FETS that require a full 12V to switch I
>do agree you need a decent proper driver but the 5V switched FETs don't
>have the same gate capacitance.

Complementary emitter follower using 0.5A TO-92 transistors will work fine
in most cases for a 5-15V gate driver. Of course you'd have to get the
signal up to higher voltage to drive the driver if it is more than Vdd.

We're not talking RF here, probably 1kHz - 20kHz tops, so an extra hundred
nsec switching time doesn't make much difference to anything (a bit more
heating). If you want to switch the MOSFET in nanoseconds then you need to
(typically) supply *amperes* into/out of the gate and the canned gate
drivers come in  handy.

There are lots of issues with this, BTW, even a few nanohenrys of inductance
in the source circuit can cause a lot of voltage change when the currents are
high. Often you actually don't WANT your MOSFETs/IGBTs to switch that fast.
MOSFETs will switch just about as fast as you can drive the gate, it's
mostly limited by the parasitic package and circuit inductances and by
the available gate drive current.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffEraseMEspam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

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2002\04\14@134026 by Kevin Howell

flavicon
face
Thats what I thought! I am worried about heat and limiting it by using PWM
will do the trick I think!?

Thanks
Kevin


{Original Message removed}

2002\04\14@145445 by Peter L. Peres

picon face
IGBT modules ...

Just don't forget that the car motor probably draws enormous start current
and you cannot let it have it. This means dynamic current limiting, which
is not so simple because you cannot use linear constant current regulation
at that dissipation and you cannot switch IGBTs that are so large quickly
(which is good in a way because of the 'broadcast factor').

Peter

-- Quoted context:

At 08:26 PM 4/13/02 +0200, you wrote:
>I can't find any Mosfets that can handle 200-300V. The problem is not to
>source them but to find a suitable part. (Keep in mind the 20A)
>
>Thanks
>Kevin

You didn't happen to run across anything that might handle about 150-200A?
;-]

I just got asked if I could build a controller for a older electric car.
It uses a big honking (technical electrical car term ....) stainless steel
coil that operate as a cross between a rheostat and a heat sink. Very
inefficient to say the least.

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2002\04\14@153731 by Peter L. Peres

picon face
>I can't find any Mosfets that can handle 200-300V. The problem is not to
>source them but to find a suitable part. (Keep in mind the 20A)

1000V and 2-3A and more at 50W+ dissipation is pretty common (in isolated
TO220 too). They are manufactured for HO stages in color TVs and SMPSUs
used in 220V countries. The usual problem is the high(er) Rdson, up to 2
ohms usually.  However you can parallel almost as many as you wish (unlike
bipolars).

Peter

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2002\04\14@175220 by Olin Lathrop

face picon face
> > > Does that mean I won't get away with a 2N2222 or a
> > opto-isolator between
> > the
> > > PIC and the MOSFET?
> >
> > Yup.
>
> Sorry,  I disagree and the fact that I am reliably switching 10A through
> the IRF series of FETs with a 2N2222A bears that out quite nicely.  I do
> agree that a driver is better.  Certainly if you attend one of the
> Microchip seminars where they talk about their FET driver product you'd
> walk away convinced.  For the FETS that require a full 12V to switch I
> do agree you need a decent proper driver but the 5V switched FETs don't
> have the same gate capacitance.

The original "get away with" was in the context of a high speed PWM power
drive circuit.  In such a case the switching speed is important, and you
want a driver that can slam the gate to either extreme as quickly as
possible.  A single 2N2222 is going to be much slower in one direction at
least, or draw a large quiescent current.  Certainly you can use a single
bipolar transistor to drive a FET gate.  If switching speed is not that
important or the switching frequency is low, then it can be just fine.


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2002\04\14@180052 by David P. Harris

picon face
Hi-
Could someone (I would, but I'm not qualified) make up a webpage with three,
say, circuits with specs fro driving Mosfets. Say:
 1/ simple, but slow, don't expect this to switch faster than 10kHz=100us,
but you might experience heating because of teh slow turnon;
 2/ middle-of-the-road, good to 1MHz, 1us;
 3/fast, this baby is good to 1ns, but beware it is sensitive to noise;
I have seen drivers using transistors, cmos gates (CD40106), and dedicated
driver chips.
Thanks in advance! ;-)
David

Olin Lathrop wrote:

{Quote hidden}

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