Looking for pulse-rated zener.

[Winfield Hill]

colin wrote...

Winfield Hill wrote ...

This active-zener method works well with low-voltage power MOSFETs,
such as under 100V, but it's dangerous with high-voltage FETs, 200V
and up, because they have a bad tendency to go into RF oscillation.
This is a high-power RF oscillation at frequencies of 15 to 40MHz,
which is very difficult to damp with external parts such a ferrite
beads, gate resistors, etc. That's because the RF oscillation is
internal to the FET, employing its inductance and self capacitance.
The required linear properties occur whenever a high current flows
while the drain-source voltage is higher than 10 to 20V. The latter
condition causes the FET capacitances to drop to the levels where RF
amplification is efficient.

If the RF feedback path is wholy internal how would this affect the
method of using a higher gate drive resistance to slow the current
fall to limit the voltage to less than the breakdown voltage?

Two different effects... The slowing of the turnoff means the
coil can flyback and dI/dt discharge as it's doing so, without
reaching the avalanche voltage, if carefully done.

or does the zener just add more parasitics to make the difference?

You're asking if oscillation doesn't happen in the event of a
slowed transition, as in the zener case? It certainly can with
high-voltage MOSFETs, although the dV/dt slewing output helps to
hide it, on the one hand, and perhaps to dampen it, on the other.


--
Thanks,
- Win

 

[Jim Thompson]

On 22 Jun 2005 12:59:47 -0700, Winfield Hill
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Western houses don't eschew basements... it just requires blasting...
the ground here at my location is layered rock.

The son's always ask, "Dad, What'd you like for father's day?"

I always reply, "Dig me a wine cellar."

Then they grimace ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[keith]

On Wed, 22 Jun 2005 12:59:47 -0700, Winfield Hill wrote:

Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Yes, but here in the North and East we have to dig down past frost for a
foundation anyway. It's cheap to add the basement, once the hole is
there. In the South and West one doesn't worry much about frost, so it's
usually cheaper just to add the space on the main floor. Those areas of
the West that do have frost often have basements.

--
Keith

 

[Mike Monett]

Winfield Hill wrote:

[...]

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Thanks,
- Win

Yes, but watch out for mold. I already had exposure to mold before I
moved to Ottawa, but the house I moved to had a great deal in the
basement and in the carpets throughout the house.

I inspected it before signing the lease, but didn't spot the mold. It was
the same color as the concrete and only grew about 1/2 or 3/4 inch high.
The only way to see it was to shine a flashlight parallel to the wall and
look into the beam.

It seemed harmless at the time, but it completely destroyed my health for
years. I am only now learning how to overcome the effects.

The family with a baby girl that moved in after me got very ill, and a
neighbour and her son who lived in an identical home with the same
problem also got very sick. The problem is you don't realize how much
damage has occurred until it's too late.

The landlord denied any responsibility, of course. And it would be
impossible to demonstrate to a jury how the mold made you sick. A good
attorney would rip your argument to shreds.

So don't make the same mistake we made. If you have any indication that
mold is growing in your home, don't ignore it. Take it very seriously -
it can ruin your health. You would not believe how easy it can happen.

Mike Monett

 

[Jim Thompson]

On Wed, 22 Jun 2005 17:29:28 -0400, keith <krw@att.bizzzz> wrote:

On Wed, 22 Jun 2005 12:59:47 -0700, Winfield Hill wrote:

Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Yes, but here in the North and East we have to dig down past frost for a
foundation anyway. It's cheap to add the basement, once the hole is
there. In the South and West one doesn't worry much about frost, so it's
usually cheaper just to add the space on the main floor. Those areas of
the West that do have frost often have basements.

And land is cheap (compared to the East). My living space is 3650
sq.ft. on a single level.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Charlie Edmondson]

Winfield Hill wrote:

Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...


I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.


Yeah, Win,

But you then have the expense of digging it, instead of just leveling
out the site and digging a little trench for your foundation. When most
houses are built as part of big developments, they make it as cheap as
they can.

Also, they have what they call Grading Permits, and it gets a lot more
expensive if you have to move more than a yard or two of earth for your
lot...

Charlie

 

[Apostrophe Police]

On Wed, 22 Jun 2005 13:42:54 -0700, Jim Thompson wrote:

On 22 Jun 2005 12:59:47 -0700, Winfield Hill
hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Western houses don't eschew basements... it just requires blasting...
the ground here at my location is layered rock.

The son's always ask, "Dad, What'd you like for father's day?"
^^^^^

I always reply, "Dig me a wine cellar."

Then they grimace ;-)

...Jim Thompson

Plurals do not use apostrophes, except some acronyms.
--
Rich Grise, Self-Appointed Chief,
Apostrophe Police

 

[Winfield Hill]

Mike Monett wrote...

Winfield Hill wrote:

[...]

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Yes, but watch out for mold. I already had exposure to mold before I
moved to Ottawa, but the house I moved to had a great deal in the
basement and in the carpets throughout the house.

I inspected it before signing the lease, but didn't spot the mold. It was
the same color as the concrete and only grew about 1/2 or 3/4 inch high.
The only way to see it was to shine a flashlight parallel to the wall and
look into the beam.

It seemed harmless at the time, but it completely destroyed my health for
years. I am only now learning how to overcome the effects.

The family with a baby girl that moved in after me got very ill, and a
neighbour and her son who lived in an identical home with the same
problem also got very sick. The problem is you don't realize how much
damage has occurred until it's too late.

The landlord denied any responsibility, of course. And it would be
impossible to demonstrate to a jury how the mold made you sick. A good
attorney would rip your argument to shreds.

So don't make the same mistake we made. If you have any indication that
mold is growing in your home, don't ignore it. Take it very seriously -
it can ruin your health. You would not believe how easy it can happen.

One question, Mike. Did the house have a good gutter system, with
drainpipes, to keep roof drainage away from the basement walls?


--
Thanks,
- Win

 

[Rich Grise]

On Wed, 22 Jun 2005 15:39:11 -0700, Charlie Edmondson wrote:

Winfield Hill wrote:
Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

But you then have the expense of digging it, instead of just leveling
out the site and digging a little trench for your foundation. When most
houses are built as part of big developments, they make it as cheap as
they can.

Also, they have what they call Grading Permits, and it gets a lot more
expensive if you have to move more than a yard or two of earth for your
lot...

It's the difference between tornadoes and earthquakes. In tornado country,
you hide in the basement while all of the debris (cows, cars, water
heaters) swirl about in the aether - in earthquake country, you go
outside and watch your house collapse onto the slab.

After the earthquake, you get a front-loader, scoop up the debris, and
toss it into the landfill. After picking out the kid-pix, of course.

After the tornado, you have to bail all of the water out of the basement,
and hire a crane to haul up all of the house debris to ground level,
and then you _still_ need to sort out the debris to figure out which
is whose.

Now, the recent landslides introduce an entirely different variable
into that equation - does that make this a three-pronged thing? Earthquake
vs. Tornado vs. Landslide?

Then again, can't forget volcanoes, hurricanes, and tsunami! ;-)

Ooh! And Meteors! There's Meteors! And Asteroids! And Gamma Rays!

Damn! We all gonna die, might as well get high. %-}

Want Some?
Rich

 

[Jim Thompson]

On Thu, 23 Jun 2005 01:54:59 GMT, Apostrophe Police
<sendspamhere@111.111.111.111> wrote:

On Wed, 22 Jun 2005 13:42:54 -0700, Jim Thompson wrote:

On 22 Jun 2005 12:59:47 -0700, Winfield Hill
hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Western houses don't eschew basements... it just requires blasting...
the ground here at my location is layered rock.

The son's always ask, "Dad, What'd you like for father's day?"
^^^^^

I always reply, "Dig me a wine cellar."

Then they grimace ;-)

...Jim Thompson

Plurals do not use apostrophes, except some acronyms.

Gawwwd! I thought I had all your persona killed. Plonk!

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Robert Baer]

Ian Stirling wrote:

In sci.electronics.design Winfield Hill <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Winfield Hill wrote...

Lasse Langwadt Christensen wrote...

snip

I've seen an app-note, onsemi I think, that stated that the
fets could handle more power with the active clamping

snip

The predictability of an added gate-zener function may be desirable.

Actually, there is another possible reason. Higher inductor flyback
voltages mean shorter inductor discharge times. Dissipating a fixed
amount of energy in a shorter time means higher junction temperatures
because the heat can't diffuse as far through metal frames, and into
the heatsink, etc. So that's an argument both for lower FET clamping
voltages and for more predictable voltages.


Not in a microsecond or shorter (the time in question).
Then it's stuck in the few microns outside junction.

An "ugly" 1000V FET like the IRFBG20 Can easily swithc on and then

off in under 0.5uSec, so what is the beef?

 

[Robert Baer]

Apostrophe Police wrote:

On Wed, 22 Jun 2005 13:42:54 -0700, Jim Thompson wrote:


On 22 Jun 2005 12:59:47 -0700, Winfield Hill
hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:


Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Western houses don't eschew basements... it just requires blasting...
the ground here at my location is layered rock.

The son's always ask, "Dad, What'd you like for father's day?"

^^^^^

I always reply, "Dig me a wine cellar."

Then they grimace ;-)

...Jim Thompson


Plurals do not use apostrophes, except some acronyms.
That is acronym's if mis-spelled the way all of the other crap is

mis-spelled (CD's, DVD's, CPU's etc etc & etc aka Yul Bynner the King
and I).

 

[Robert Baer]

Rich Grise wrote:

On Wed, 22 Jun 2005 15:39:11 -0700, Charlie Edmondson wrote:

Winfield Hill wrote:

Jim Thompson wrote...


archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.


But you then have the expense of digging it, instead of just leveling
out the site and digging a little trench for your foundation. When most
houses are built as part of big developments, they make it as cheap as
they can.

Also, they have what they call Grading Permits, and it gets a lot more
expensive if you have to move more than a yard or two of earth for your
lot...


It's the difference between tornadoes and earthquakes. In tornado country,
you hide in the basement while all of the debris (cows, cars, water
heaters) swirl about in the aether - in earthquake country, you go
outside and watch your house collapse onto the slab.

After the earthquake, you get a front-loader, scoop up the debris, and
toss it into the landfill. After picking out the kid-pix, of course.

After the tornado, you have to bail all of the water out of the basement,
and hire a crane to haul up all of the house debris to ground level,
and then you _still_ need to sort out the debris to figure out which
is whose.

Now, the recent landslides introduce an entirely different variable
into that equation - does that make this a three-pronged thing? Earthquake
vs. Tornado vs. Landslide?

Then again, can't forget volcanoes, hurricanes, and tsunami! ;-)

Ooh! And Meteors! There's Meteors! And Asteroids! And Gamma Rays!

Damn! We all gonna die, might as well get high. %-}

Want Some?
Rich


....my Gamma is a *real* RAY of sunshine...

 

[Robert Baer]

Winfield Hill wrote:

Mike Monett wrote...

Winfield Hill wrote:

[...]


I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Yes, but watch out for mold. I already had exposure to mold before I
moved to Ottawa, but the house I moved to had a great deal in the
basement and in the carpets throughout the house.

I inspected it before signing the lease, but didn't spot the mold. It was
the same color as the concrete and only grew about 1/2 or 3/4 inch high.
The only way to see it was to shine a flashlight parallel to the wall and
look into the beam.

It seemed harmless at the time, but it completely destroyed my health for
years. I am only now learning how to overcome the effects.

The family with a baby girl that moved in after me got very ill, and a
neighbour and her son who lived in an identical home with the same
problem also got very sick. The problem is you don't realize how much
damage has occurred until it's too late.

The landlord denied any responsibility, of course. And it would be
impossible to demonstrate to a jury how the mold made you sick. A good
attorney would rip your argument to shreds.

So don't make the same mistake we made. If you have any indication that
mold is growing in your home, don't ignore it. Take it very seriously -
it can ruin your health. You would not believe how easy it can happen.


One question, Mike. Did the house have a good gutter system, with
drainpipes, to keep roof drainage away from the basement walls?


...As well as a sump pump to keep the water table (in the basement

area) at least 5 feet below the basement floor?
A sump pump, i understand, will do that for a radius of 25 feet or so.

 

[Mike Monett]

Winfield Hill wrote:

[...]

One question, Mike. Did the house have a good gutter system, with
drainpipes, to keep roof drainage away from the basement walls?

Thanks,
- Win

Very astute question, Win. The drainage was very poor. The gutters were
full of leaves and warped so they wouldn't drain properly, and water
just spilled over in the middle. But you don't notice these things until
the first storm, after you have signed the lease and moved in.

The downspouts were normally connected to drainage pipes to take the
water away from the house, but these had been removed to make cutting
the grass easier. So the water stayed along the exterior walls.

The basement wasn't sealed - the concrete was bare. After the first
storm, there was several inches of water in the basement. A great deal
of wood that was stored lying flat on the floor turned out to have mold
underneath.

The landlord promised to fix everything but it never happened. Then
winter set in and it became impossible to do anything. Ottawa had an
extremely low vacancy rate at the time, and the landlords could get away
with anything. You counted yourself lucky if there was a roof over your
head. Some of the places I looked at were just incredible.

All these things were against city code. But lack of enforcement meant
doing the best to try to fix things myself. This turned out to be
impossible. An amateur with a paintbrush cannot seal a concrete
basement. It takes professionals with the proper equipment, and it
should have been done when the house was built.

I tried to leave as soon as the first symptoms started, but a vacancy
rate of 0.3% in the middle of winter meant there was nowhere else to go.

My big mistake was underestimating what mold can do to your health. The
worst symptoms didn't really show up until after I moved. By then it was
too late.

Since then I have found many basements that are sealed properly but may
have accumulated cardboard boxes full of paper or clothes. Even if the
basement doesn't leak, the cardboard accumulates moisture and provides
an excellent place for mold to grow.

So if you can smell a musty odor after returning from shopping, mold is
growing somewhere and it should be corrected.

Mike Monett

 

[Mike Monett]

Robert Baer wrote:

Winfield Hill wrote:

[...]

One question, Mike. Did the house have a good gutter system, with
drainpipes, to keep roof drainage away from the basement walls?


...As well as a sump pump to keep the water table (in the basement
area) at least 5 feet below the basement floor?
A sump pump, i understand, will do that for a radius of 25 feet or so.

Yes, there was a sump pump. I believe the hole was 3 or 4 feet deep. The pump
didn't work, and the hole was plugged with silt. I fixed both problems, but
the first storm overwhelmed the pump and the basement flooded.

This was a clear sign something was wrong. But with the low vacancy rate in
Ottawa, there were few places to move to. And the places that were available
were in much worse condition!

Mike Monett

 

[Paul Burke]

Apostrophe Police wrote:

Plural's do not use apostrophe's, except some acronym's.

You discriminate against greengrocer's. I say put astropope's where you
feel like!

 

[Winfield Hill]

Paul Burke wrote...

Apostrophe Police wrote:

Plural's do not use apostrophe's, except some acronym's.

You discriminate against greengrocer's. I say put astropope's
where you feel like!

Astro-popes, certainly, if you wish.


--
Thanks,
- Win

 

[Watson A.Name - \"Watt Su]

"Winfield Hill" <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote in
message news:d9cfvj0su1@drn.newsguy.com...

Jim Thompson wrote...

archive storage (I rent an off-site, air-conditioned, 10'x10'
storage "cell" that I have filled with file drawers) ...

I never could understand why Western houses eschew basements.
A full basement is a VERY useful thing to have. Get double
or half-again the floor area of the house in one quick step.

Well, some areas of the coutnry have to have basements because of the
tornadoes. But here in So. Calif, we seldom have basements, I'm
guessing the reasons are:

Because the dwelling is on a sandy soil that has a shallow water table,
so the basement would be easily flooded.

Because most of the housing built after WW2 used a poured cement slab
for the floor.

Because in a bad earthquake, the rest of the house would fall into the
basement.

Because it's cheaper to build a second story out of wood than dig a hole
and pour concrete walls, needed for earthquake reasons. Also since it
doesn't get cold here, the insulation doesn't have to be that great, so
the second story is even cheaper.

Probably a combination of the above.

I think that this place has a cool basement.
http://www.earth-house.com/Homes_4_Sale/Atlas_E_Silo/atlas_e_silo.html

--
Thanks,
- Win

 

[Winfield Hill]

colin wrote...

The same thing would happen with the simpler RC snubber accros a single
switch as was suggested before, but put a diode in series with the inductor
so that when the current stops the diode blocks the voltage acros the
capacitor causing current in the reverse direction through the coil.

when the switch opens the current travels through the resistor and
(discharged) capacitor, initialy creating the necessary voltage across
the R, then when the curent drops the voltage acros the resistor falls
and the voltage across the capacitor has risen keeping the voltage high
enough all the time the current is flowing for a fast fall time/peak
voltage, when the switch next closes it discharges the capacitor through
the resistor as it turns on the current to the coil.

o
|
C|
C| coil
C| L
|
|
V diode
-
| R
+-----/\/\----+
| |
| D | C
||-+ ---
||<- ---
o-----||-+ |
| S |
-+-------------+-

Yes, that's good. One must be careful not to select R too small,
because then the FET's current at switch-on might be excessive.
And one musn't selecting R too high, because then it'll develop too
much voltage from the inductor's current at switch-off, forcing us
to use an artificially-high-voltage FET. Selecting R so its maximum
voltage drop equals the maximum capacitor voltage sounds promising.

Applying this to Mark Becker's 8uH 15A 1us shutoff requirement, with
C = 33nF and R = 7.5 ohms, we get a snappy 0.7us coil-current switch-
off, a maximum FET voltage of 190V, and a maximum FET current of only
19A for 0.5us at switch-on. The coil is slow to get up to its 15A
current, saving the FET any extra stress.

We need a high-current diode rated for more than 200V. I used both
halves of a MUR3040, but despite being a fast-recovery part it still
suffers from a reverse-recovery-time delay. This means the inductor
rings badly (at 4MHz, 380Vp-p in my model) unless its damped. Adding
0.01uF plus 150 ohms in parallel does the job nicely, and also reduces
the FET's Vd-max to 180V and Id-max to 18A.

One big downside to this approach to capturing the inductor's energy
is another 15W of power continuously dissipated in the series diode.


--
Thanks,
- Win