voltage regulator
- From: "kell" <kellrobinson@xxxxxxxxxxxx>
- Date: 21 Jan 2006 12:34:48 -0800
This is the voltage regulator I asked for suggestions about current
limiting. The diagram shows the prototype without current limiting.
+-----------------+------+-----O +Batt
| | |
_/ | |
7.5v /^ 1K - blocking
| | ^ diode
| | |
| | |
| | +-----O Armature
| | |
| | |
| | - freewheel
| | ^ diode
| | |
V +---100K---------+-----O Field
- | | |
| | | |
: | | |
1N4148 : | | |
X10 : | | _|
| | .01 | |
V +----||---+---|| N channel
- | | |_ mosfet
| | | |
| | c/ |
+---R---+-------| NPN |
| e\ |
Rtrim | |
| | |
+-----------------+------+------O Ground
The 100 K resistor and the 0.1 uF cap are for hysteresis, to keep heat
down in the mosfet; I'm putting this circuit into a small, flat
enclosure without fins so it can be installed in a motorcycle's battery
compartment. The string of 1N4148 diodes are there so the regulator
will have a temperature coefficient matching the charging
characteristic of the battery. And that's another reason to keep heat
down in the circuit. Similarly, I used a schottky for the blocking
diode, which has to conduct all the charging current.
Generator configuration:
One of the armature brushes is grounded. The other brush is wired to
the A terminal on the outside of the generator and is also connected to
one end of the field coils. The other end of the field is connected to
the F terminal on the outside of the generator. It's called a floating
field or "type A" arrangement, common on the old GM vehicles and
Harleys.
Any current limiting scheme will probably involve a sense resistor in
series with the blocking diode. Some discretes or an op amp will send
a current the base of the NPN transistor controlling the mosfet that
conducts field current, diverting the pullup resistor current and
lowering the Vgs, thus reducing field current.
I'm still debating the easiest way to do it. I got some great ideas
from Win and the others in the previous thread about this subject. But
my failure to elucidate how how the regulator and generator work
resulted in some confusion and I decided to post an explanation.
.
- Prev by Date: Re: small hv fet
- Next by Date: Re: project advice - video -> ADC -> radio -> PC
- Previous by thread: Bluetooth Suggestions?
- Next by thread: Pressure sensor for magnets?
- Index(es):
Relevant Pages
|
