piclist 2007\12\17\152122a >
Thread: Repost: PV OptoIsolator / MOS Driver Info
www.piclist.com/techref/index.htm?key=optoisolator+mos
face picon face BY : Bob Axtell email (remove spam text)



Martin Klingensmith wrote:
{Quote hidden}

The way the thread began was that someone asked how to drive a MOSFET
directly with an optoisolator.
Of course, you can't really do so unless you have an isolated power
supply floating up there that can be
used to switch the MOSFET input. MOSFET power switches usually need
10-15V at 50uA to turn on a
power MOSFET.

I then told him about the TLP191B, which is a photvoltaic module; its
input is an IR diode junction, and the
output is a pack of PV cells wired in series. The IR excites the PV
cells, thus generating 10-20V or so, dependent
on the input current on the IR diode. My useage is simply ON or OFF, and
the TLP191B does that reliably
directly.  But how would you drive a MOSFET at PWM speeds?

It turns out that the PV cells switch very slowly. I am planning to
simply excite the TLP191B constantly, then use
the 20V "power supply" as the power to switch a FAST standard
optoisloator, such as one of HP's units. Then
a PWM signal can indirectly drive the MOSFET at a reasonable speed (such
as 16Khz).


--Bob
<4766D99A.2090105@cotse.net> 7bit

In reply to: <4766D1D1.4080505@nnytech.net>
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Subject (change) Repost: PV OptoIsolator / MOS Driver Info

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