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Discussion Groups | BasicX | Need some help with Power MOSFET driver
Discussion forum for the BasicX family of microcontroller chips.
Need some help with Power MOSFET driver - "James R. Parish" - Mar 11 11:47:00 2008
I'm using DACPIN out of the BX24 to drive an opamp. The opamp then
drives a MOSFET. This circuit works but the heatsink gets very hot,
like 150 degrees F pushing 1.25 amps. I have read that MOSFETs will
run cooler using PWM. I'm running the MOSFET in its linear region is
why all the unnecessary heat. Does anyone have a quick-n-easy way to
change this circuit to a PWM output feeding the MOSFET?
I have one opamp left unused in the LM324. This is my (sadly to say)
first attempt to use opamps, I have spent a lot of time in the digital
domain, I have no excuse.
I'm reading the current through a shunt with the BX24 and have DACPIN
running in a small task. I adjust the VAR in the task as needed to set
the current, it works really well.
Thanks, JP
http://www.trn.net/drive.bmp
[Non-text portions of this message have been removed]
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RE: Need some help with Power MOSFET driver - "James R. Parish" - Mar 11 18:17:11 2008
BIG Heatsink. But I will be charging at 5.5A or about 1400 watts.
Since the battery will only be at 50% DOD the 5.5 amps will only be
drawn during the BULK charge. The Absorption stage will hold the
voltage at 290V until the current drops by 75%. Then float at 276V.
From: b...@yahoogroups.com [mailto:b...@yahoogroups.com] On Behalf
Of r...@aol.com
Sent: Tuesday, March 11, 2008 12:11 PM
To: b...@yahoogroups.com
Subject: Re: [BasicX] Need some help with Power MOSFET driver
Hi,
I do not see any problem the transistor getting hot because the load is
pulling out. By doing some calculation watts = V I and 260 volts * 1.25
amps is equal to 325 watts. 325 watts it will going to get hot. You may
need to increase the heat sink area. Normally? once the battery is
charged? the battery needs only a trickle charge so can lower the
charging current. What type of heat sink you are using right now? You
may need a bigger heat sink for the load the transistor is handling.
rosarite
-----Original Message-----
From: Tom Becker
Sent: Tue, 11 Mar 2008 10:25 am
Subject: Re: [BasicX] Need some help with Power MOSFET driver
> ... Charging a 260VDC battery.
Can you show us the high-voltage power supply and load circuit you're
using now?
In general, PWM is very easy since it is digital and the processor will
do most of the timing work for you, but high-voltage needs some
consideration. If you were charging a 6v battery it would be very easy.
Tom
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
Since the battery will only be at 50% DOD the 5.5 amps will only be
drawn during the BULK charge. The Absorption stage will hold the
voltage at 290V until the current drops by 75%. Then float at 276V.
From: b...@yahoogroups.com [mailto:b...@yahoogroups.com] On Behalf
Of r...@aol.com
Sent: Tuesday, March 11, 2008 12:11 PM
To: b...@yahoogroups.com
Subject: Re: [BasicX] Need some help with Power MOSFET driver
Hi,
I do not see any problem the transistor getting hot because the load is
pulling out. By doing some calculation watts = V I and 260 volts * 1.25
amps is equal to 325 watts. 325 watts it will going to get hot. You may
need to increase the heat sink area. Normally? once the battery is
charged? the battery needs only a trickle charge so can lower the
charging current. What type of heat sink you are using right now? You
may need a bigger heat sink for the load the transistor is handling.
rosarite
-----Original Message-----
From: Tom Becker
Sent: Tue, 11 Mar 2008 10:25 am
Subject: Re: [BasicX] Need some help with Power MOSFET driver
> ... Charging a 260VDC battery.
Can you show us the high-voltage power supply and load circuit you're
using now?
In general, PWM is very easy since it is digital and the processor will
do most of the timing work for you, but high-voltage needs some
consideration. If you were charging a 6v battery it would be very easy.
Tom
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
Re: Need some help with Power MOSFET driver - Tom Becker - Mar 11 20:37:24 2008
> ... 1400 watts is a lot.
Well understated, Rosarite. 1400 Watts of wasted power is a space
heater! He needs another method, methinks.
Tom
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
Well understated, Rosarite. 1400 Watts of wasted power is a space
heater! He needs another method, methinks.
Tom
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
Re: Need some help with Power MOSFET driver - rosa...@aol.com - Mar 11 20:46:08 2008
Hi,
1400 watts is a lot. I do not see any problem as long you are within the specification of the mosfet in amps and voltages.? You need to find out on how to dissipate the heat and stay in the mosfet heat working specification. You may need a heat sink like the one used in SCR.
Did you try adding a fan to cool it?
Which mosfet your are using right now.
?
rosarite
-----Original Message-----
From: James R. Parish
To: b...@yahoogroups.com
Sent: Tue, 11 Mar 2008 4:13 pm
Subject: RE: [BasicX] Need some help with Power MOSFET driver
BIG Heatsink. But I will be charging at 5.5A or about 1400 watts.
Since the battery will only be at 50% DOD the 5.5 amps will only be
drawn during the BULK charge. The Absorption stage will hold the
voltage at 290V until the current drops by 75%. Then float at 276V.
From: b...@yahoogroups.com [mailto:b...@yahoogroups.com] On Behalf
Of r...@aol.com
Sent: Tuesday, March 11, 2008 12:11 PM
To: b...@yahoogroups.com
Subject: Re: [BasicX] Need some help with Power MOSFET driver
Hi,
I do not see any problem the transistor getting hot because the load is
pulling out. By doing some calculation watts = V I and 260 volts * 1.25
amps is equal to 325 watts. 325 watts it will going to get hot. You may
need to increase the heat sink area. Normally? once the battery is
charged? the battery needs only a trickle charge so can lower the
charging current. What type of heat sink you are using right now? You
may need a bigger heat sink for the load the transistor is handling.
rosarite
-----Original Message-----
From: Tom Becker
>
To: b...@yahoogroups.com
Sent: Tue, 11 Mar 2008 10:25 am
Subject: Re: [BasicX] Need some help with Power MOSFET driver
> ... Charging a 260VDC battery.
Can you show us the high-voltage power supply and load circuit you're
using now?
In general, PWM is very easy since it is digital and the processor will
do most of the timing work for you, but high-voltage needs some
consideration. If you were charging a 6v battery it would be very easy.
Tom
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
Re: Need some help with Power MOSFET driver - rosa...@aol.com - Mar 13 5:43:46 2008
Hi,
For your information.
http://www.mpoweruk.com/chargers.htm
I found this article very interesting on how to charge batteries. I think maybe you can use the pulse method that they explained here.
rosarite
-----Original Message-----
From: James R. Parish
To: b...@yahoogroups.com
Sent: Tue, 11 Mar 2008 4:13 pm
Subject: RE: [BasicX] Need some help with Power MOSFET driver
BIG Heatsink. But I will be charging at 5.5A or about 1400 watts.
Since the battery will only be at 50% DOD the 5.5 amps will only be
drawn during the BULK charge. The Absorption stage will hold the
voltage at 290V until the current drops by 75%. Then float at 276V.
From: b...@yahoogroups.com [mailto:b...@yahoogroups.com] On Behalf
Of r...@aol.com
Sent: Tuesday, March 11, 2008 12:11 PM
To: b...@yahoogroups.com
Subject: Re: [BasicX] Need some help with Power MOSFET driver
Hi,
I do not see any problem the transistor getting hot because the load is
pulling out. By doing some calculation watts = V I and 260 volts * 1.25
amps is equal to 325 watts. 325 watts it will going to get hot. You may
need to increase the heat sink area. Normally? once the battery is
charged? the battery needs only a trickle charge so can lower the
charging current. What type of heat sink you are using right now? You
may need a bigger heat sink for the load the transistor is handling.
rosarite
-----Original Message-----
From: Tom Becker
>
To: b...@yahoogroups.com
Sent: Tue, 11 Mar 2008 10:25 am
Subject: Re: [BasicX] Need some help with Power MOSFET driver
> ... Charging a 260VDC battery.
Can you show us the high-voltage power supply and load circuit you're
using now?
In general, PWM is very easy since it is digital and the processor will
do most of the timing work for you, but high-voltage needs some
consideration. If you were charging a 6v battery it would be very easy.
Tom
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )
For your information.
http://www.mpoweruk.com/chargers.htm
I found this article very interesting on how to charge batteries. I think maybe you can use the pulse method that they explained here.
rosarite
-----Original Message-----
From: James R. Parish
To: b...@yahoogroups.com
Sent: Tue, 11 Mar 2008 4:13 pm
Subject: RE: [BasicX] Need some help with Power MOSFET driver
BIG Heatsink. But I will be charging at 5.5A or about 1400 watts.
Since the battery will only be at 50% DOD the 5.5 amps will only be
drawn during the BULK charge. The Absorption stage will hold the
voltage at 290V until the current drops by 75%. Then float at 276V.
From: b...@yahoogroups.com [mailto:b...@yahoogroups.com] On Behalf
Of r...@aol.com
Sent: Tuesday, March 11, 2008 12:11 PM
To: b...@yahoogroups.com
Subject: Re: [BasicX] Need some help with Power MOSFET driver
Hi,
I do not see any problem the transistor getting hot because the load is
pulling out. By doing some calculation watts = V I and 260 volts * 1.25
amps is equal to 325 watts. 325 watts it will going to get hot. You may
need to increase the heat sink area. Normally? once the battery is
charged? the battery needs only a trickle charge so can lower the
charging current. What type of heat sink you are using right now? You
may need a bigger heat sink for the load the transistor is handling.
rosarite
-----Original Message-----
From: Tom Becker
>
To: b...@yahoogroups.com
Sent: Tue, 11 Mar 2008 10:25 am
Subject: Re: [BasicX] Need some help with Power MOSFET driver
> ... Charging a 260VDC battery.
Can you show us the high-voltage power supply and load circuit you're
using now?
In general, PWM is very easy since it is digital and the processor will
do most of the timing work for you, but high-voltage needs some
consideration. If you were charging a 6v battery it would be very easy.
Tom
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )