AVR-Chat

hi everybody
could anybody help me to know how to switch power semiconductors by 
AVRs???

Which power semiconductors (MOSFET, IGBT, bipolar) ?
How much power (volts, amps, AC, DC) ?
What kind of load (resistive (lights, heaters), inductive (motors,
relays), capacitive (bigger semiconductors)) ?
How fast (2 times a day, 1 000 000 times per second) ?
etc.

For a DC load up to about 80 volts and 5 amps, you can use an IRF510 MOSFET.

Regards,
  JJ

On Sun, Jun 15, 2008 at 8:24 AM, mooodij <mooodij@yahoo.com> wrote:
> hi everybody
> could anybody help me to know how to switch power semiconductors by
> AVRs???
>
> 



-- 
Regards,
 JJ

http://www.pcbgcode.org

I use IRF2804's to switch various current loads up to 50 A, using a Micrel
5014 (or 5015) driver.  The driver can be easily controlled with a signal
directly from the uC.    The control threshold is about 2 V.   The 2804's
have a really low on-resistance, only 2 milli-ohms, and I don't use any heat
sink at all up to 10 A or so.    At 50 A I use a modest heat sink, but have
yet to even feel it get warm.   They are spec'd up to 75 A continuous.
Pretty amazing little gizmos.

 

Steve

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of mooodij
Sent: Sunday, June 15, 2008 5:24 AM
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] avr & power semiconductors

 

hi everybody
could anybody help me to know how to switch power semiconductors by 
AVRs???

 

__________ Information from ESET Smart Security, version of virus signature
database 3191 (20080616) __________

The message was checked by ESET Smart Security.

http://www.eset.com



[Non-text portions of this message have been removed]

Steve - thank you for your info on these two.  What are some 
applications you've used these in?  I'm a newbie, just starting to 
learn, and I appreciate these hardware insights and experiences.  
Would you ever drive the 2804 directly from a uC output pin?  If you 
can discuss the use of the driver a bit, that would be great.  What 
do/would you say to the boss that says "we can't afford that extra 
part"?  Thanks for any further insight you can add to your already 
helpful post.  Info on things that work well for others, especially 
low power/drain components that "do the job" well, are always useful.

Thanks !!

Charlie

--- In AVR-Chat@yahoogroups.com, "Steven Hodge" <stevehodge@...> 
wrote:
>
> I use IRF2804's to switch various current loads up to 50 A, using 
a Micrel
> 5014 (or 5015) driver.  The driver can be easily controlled with a 
signal
> directly from the uC.    The control threshold is about 2 V.   The 
2804's
> have a really low on-resistance, only 2 milli-ohms, and I don't 
use any heat
> sink at all up to 10 A or so.    At 50 A I use a modest heat sink, 
but have
> yet to even feel it get warm.   They are spec'd up to 75 A 
continuous.

> Pretty amazing little gizmos.
> 
>  
> 
> Steve

IRF1324S-7PPBF-ND on Digikey.

1 mOhms @ 160A, 10V
Id 429A
Pulsed rating > 1600A

And this is in a relatively small SMD package!

The Micrel 5014 costs all of $2.05 (smt) or $2.48 (dip), qty 1, at Digi-Key.
It can be used high-side or low-side.   I have only used low-side to date,
figure 2 of the data sheet.   The only other component needed is the usual
bypass capacitor.    It doesn't get much cheaper or easier.

 

As for driving the 2804 directly with uC output, that depends upon the
voltages involved, ie, what supply you are using for the uC and what load
voltage you are switching.   You would have to be switching load voltages no
higher than the Atmel uC's supply voltage max of 5 V or so and that will
severely limit the ability of the 2804 to turn on fully (see the 2804 data
sheet).   Frankly, I would forget about trying to do this.   Just bite the
bullet, add the driver, and things will work beautifully, without any
problems.   

 

My applications are marine-related.  In the particular case of the 50 A
load, it is current for an MSD  ("marine sanitation device"), aka, sewage
treatment.  The current is continuous for 3-5 minutes.  Voltages are 12 VDC.

 

Steve

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of charlieknox
Sent: Tuesday, June 17, 2008 6:53 AM
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] Re: avr & power semiconductors

 

Steve - thank you for your info on these two. What are some 
applications you've used these in? I'm a newbie, just starting to 
learn, and I appreciate these hardware insights and experiences. 
Would you ever drive the 2804 directly from a uC output pin? If you 
can discuss the use of the driver a bit, that would be great. What 
do/would you say to the boss that says "we can't afford that extra 
part"? Thanks for any further insight you can add to your already 
helpful post. Info on things that work well for others, especially 
low power/drain components that "do the job" well, are always useful.

Thanks !!

Charlie






[Non-text portions of this message have been removed]

> Steve - thank you for your info on these two.  What are some
> applications you've used these in?  I'm a newbie, just starting to
> learn, and I appreciate these hardware insights and experiences.
> Would you ever drive the 2804 directly from a uC output pin?  If you
> can discuss the use of the driver a bit, that would be great.  What
> do/would you say to the boss that says "we can't afford that extra
> part"?  Thanks for any further insight you can add to your already
> helpful post.  Info on things that work well for others, especially
> low power/drain components that "do the job" well, are always useful.
>
> Thanks !!
>
> Charlie


Charlie -

How you drive a FET depends on a couple of things. The biggest is whether
it is high-side or low-side. If it is N-channel high-side, or P-channel
low-side, you almost always need some sort of driver. If it is P-channel
high-side, then the issue is whether or not the voltage being controlled
is higher or lower than Vcc of the micro. If the voltage being controlled
is same or lower than Vcc, then you possibly CAN drive it directly from
the micro; otherwise, some interface is needed (though it might be pretty
simple). If it is N-channel low-side, then you very likely CAN drive it
direct from the micro.

All of this is then modified by the question of switching speed. FETs take
a LOT of gate current (sometimes AMPERES) to switch fast. Fast switch
means less power dissipation and more switching cycles per second. If you
application is pretty low speed (40KHz switcher, for example) and load
currents are not huge, then  direct drive from the micro could be just
fine (as bounded by the cases described in the previous paragraph). But,
if you need fast switching, then a good gate driver is in order,

Another limiting factor is the gate threshold of the FET and the Vcc of
the micro. You need the gate threshold to be no bigger in magnitude than
Vcc/2. Thus, driving a FET with a threshold of 2.4V from a 3.3V micro is
asking for big problems. These problems will happen at temperature
extremes and will be most noticeable with higher load currents (as the FET
won't be fully saturated and will have excessive power dissipation).

Hope this helps,

Jim Wagner
Oregon Research Electronics

If you are building a push-pull, H-bridge style driver, look up "shoot
through." That is when you turn the high side off, and the low side
on, or vice-versa. The drivers don't turn off instantly, so you need a
little delay. Without it, you effectively short out the power supply
every time it switches.

Rather than all our speculating, just let us know what you are
driving, voltages, etc. Unless it's an anti-gravity lawnmower, there
is probably some info around about doing it.

Regards,
  JJ

On Wed, Jun 18, 2008 at 4:08 PM,  <wagnerj@proaxis.com> wrote:
>> Steve - thank you for your info on these two. What are some
>> applications you've used these in? I'm a newbie, just starting to
>> learn, and I appreciate these hardware insights and experiences.
>> Would you ever drive the 2804 directly from a uC output pin? If you
>> can discuss the use of the driver a bit, that would be great. What
>> do/would you say to the boss that says "we can't afford that extra
>> part"? Thanks for any further insight you can add to your already
>> helpful post. Info on things that work well for others, especially
>> low power/drain components that "do the job" well, are always useful.
>>
>> Thanks !!
>>
>> Charlie
>
> Charlie -
>
> How you drive a FET depends on a couple of things. The biggest is whether
> it is high-side or low-side. If it is N-channel high-side, or P-channel
> low-side, you almost always need some sort of driver. If it is P-channel
> high-side, then the issue is whether or not the voltage being controlled
> is higher or lower than Vcc of the micro. If the voltage being controlled
> is same or lower than Vcc, then you possibly CAN drive it directly from
> the micro; otherwise, some interface is needed (though it might be pretty
> simple). If it is N-channel low-side, then you very likely CAN drive it
> direct from the micro.
>
> All of this is then modified by the question of switching speed. FETs take
> a LOT of gate current (sometimes AMPERES) to switch fast. Fast switch
> means less power dissipation and more switching cycles per second. If you
> application is pretty low speed (40KHz switcher, for example) and load
> currents are not huge, then direct drive from the micro could be just
> fine (as bounded by the cases described in the previous paragraph). But,
> if you need fast switching, then a good gate driver is in order,
>
> Another limiting factor is the gate threshold of the FET and the Vcc of
> the micro. You need the gate threshold to be no bigger in magnitude than
> Vcc/2. Thus, driving a FET with a threshold of 2.4V from a 3.3V micro is
> asking for big problems. These problems will happen at temperature
> extremes and will be most noticeable with higher load currents (as the FET
> won't be fully saturated and will have excessive power dissipation).
>
> Hope this helps,
>
> Jim Wagner
> Oregon Research Electronics
>
> 



-- 
Regards,
 JJ

http://www.pcbgcode.org