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From: Ian Stirling
Subject: Re: Mosfet and rectifiers
Date: Tue, 10 Sep 2002 15:30:30 +0000 (UTC)
NNTP-Posting-Date: Tue, 10 Sep 2002 15:30:30 +0000 (UTC)
User-Agent: tin/1.5.6-20000803 ("Dust") (UNIX) (Linux/2.4.18 (i686))
> Hi everyone,
> I'm building a 0-90vdc motor speed controller. I have a seperate power supply
> for my motors and for my logic circuit. I have a pair of PIC processors
> outputting PWM into a pair of MOSFets rated at 5amp 400volt. The signal is
> going thru a 7407 with a 10k resistor pulling hi to 12vdc.
> My question is regarding the DC going thru the MOSfets to power the motors. I
> only have a bridge rectifier with no regulator or caps. Will this be a problem
> with the MOSfets? Will this cause noise in my logic circuit?
> As I was assemblingthe board this morning I suddenly noticed that this could be
> a problem.
They shouldn't care.
Assuming that you'r using the two FETs in parallel, and running from bridge
rectified AC, it should work fine.
The body diode will conduct in the reverse direction when the EMF from the
motor is greater than the voltage from the bridge, but this shouldn't
http://inquisitor.i.am/ | mailto:firstname.lastname@example.org | Ian Stirling.
"An enemy will usually have three courses open to him. Of these he will
select the fourth." -- Helmuth von Moltke
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