Re: op amp controlling a mosfet

kell wrote:
Imagine you have a vehicle that receives up to ten amps from a
generator, and with the generator off you need a blocking rectifier to
keep the 12 volt battery from discharging into the generator windings,
so you decide to use the body diode of mosfet as the blocking
rectifier; during charging you can have the mosfet turned on to reduce
dissipation. The blocking has to occur in the positive rail because
ground consists of the vehicle chassis.
What is the best way? I was thinking about something along these
lines:

generator
|
,------------+
| |
| _ _|D
'--|-\ | STP80PF55
LF412| >-+-|| p-channel
,--|+/ | |_ mosfet
| | |S
| 100K |
| | |
| | |
'-------+----+
|
|
battery

Somebody told me the LF412 works with common mode inputs at the
positive rail, but if I should be looking at some other op-amp let me
know.
http://www.national.com/ds/LF/LF412.pdf

I doubt this simple circuit will do. The concept is to drive the gate negative (down to ground) with respect to the source any time the battery is more negative than the generator. So it gets real important what powers the opamp, and that it (both the supply pins and inputs) is protected from voltage spikes. Are you going to power the opamp at all times from the battery?
.

Relevant Pages

  • Re: op amp controlling a mosfet
    ... generator, and with the generator off you need a blocking rectifier to ... keep the 12 volt battery from discharging into the generator windings, ... inputs) is protected from voltage spikes. ...
    (sci.electronics.basics)
  • op amp controlling a mosfet
    ... generator, and with the generator off you need a blocking rectifier to ... ground consists of the vehicle chassis. ...
    (sci.electronics.basics)
  • Re: op amp controlling a mosfet
    ... generator, and with the generator off you need a blocking rectifier to ... keep the 12 volt battery from discharging into the generator windings, ...
    (sci.electronics.basics)
  • Re: op amp controlling a mosfet
    ... generator, and with the generator off you need a blocking rectifier to ... keep the 12 volt battery from discharging into the generator windings, ...
    (sci.electronics.basics)
  • Re: pro user 850w generator opinions?
    ... | would be OK to plug into the van mains input and charge the battery / ... the van powered up, you should give either method several days to ... The power from a wind generator varies as the *cube* of the windspeed, ...
    (uk.rec.caravanning)
Loading