Maker Pro
Maker Pro

Simplest latch imaginable

T

Terry Given

Jan 1, 1970
0
Winfield Hill said:
Winfield Hill wrote...

Aha! I found them at 7.8 cents, so there!

Thanks,
- Win

whill_at_picovolt-dot-com (use hill_at_rowland-dot-org for now)

I sit corrected.....but can I buy 5 different parts from 5 different
manufacturers that fit in the same space.....

Great to see examples using specified device ratings. IMO its what
distinguishes the engineer from the hacker, and differentiates the
production success from the nightmare.
 
T

Terry Given

Jan 1, 1970
0
Spehro Pefhany said:
The 2N506x is a jellybean part, made by a bunch of manufacturers.
On Semi, Teccor, Central Semi, ST, Philips (there's 5). They have been
around (and reasonably priced) for maybe 30 years that I know of, and
are still going strong.

Eg. http://www.onsemi.com/pub/Collateral/2N5060-D.PDF

Note: "preferred device"

The only gotcha to be a bit careful with is the Vdrm rating of
30V/usec typical, so a bit of snubbing might be required in some
applications.

voila.


You mean you don't just start production if the prototype works? ;-)

no, not at all. I worked on an existing mil UPS design in the states a few
years back. Many battery failures started occurring, so I looked at the
charger - a simple flyback converter with closed-loop voltage regulation,
and a current limit too. All seemed well. Then I measured its behaviour, and
found appalling line regulation - from 115Vac to 230Vac caused the output
voltage to change dramatically, around 50% IIRC. But at 115Vac in, Vout
happened to be right......obviously load regulation was appalling too.

Feedback was opto via TL431, I forget how the current limit worked exactly,
but through the same opto. how could it not regulate?!? This was designed by
the VP of eng, a twit with an ME from MIT, and no real skill. basically they
turned it on, it didnt explode, the voltage looked right, so they shipped
it!

close examination showed a host of layout problems, but the main culprit was
the ultra-slow rectifier diode (Trr spec anyone?) which successfully managed
to use up all the gain margin in the closed-loop controller.

speaking of which, closing a loop can do some interesting things. If you
think about closed-loop response to a disturbance, you can "inject" that
disturbance anywhere you like - for example a load change. Alternatively,
you can build a "self-disturbing" controller by screwing up the calculations
(or the circuit ;) - effectively injecting a disturbance in a different part
of the loop.

If loop gain is high enough, it will STILL WORK! Of course when doing
transient tests you'll get a worse response, as the control loop is busy
dealing with the self-inflicted problems - hence my comment about gain
margin.can be hard to diagnose, as the system works but with degraded
performance. I did this with a 200kW 3-phase inverter/rectifier controller -
I had a wide variety of screw-ups in my code (sine routines overflowing,
etc) yet it all worked, but not as well as expected. I went thru and
individually calibrated all my maths routines, and found some astonishing
errors - about 20 degrees of my sine calculation overflowed due to crap in a
look-up table, yet my PLL (sync. ref. frame PI controller really) worked
brilliantly, and the UPS wasnt too shabby - 10% load regulation. Given that
the sine routine was used to calculate the PWM switching times, i.e. the
overflow resulting in a burst of incorrect PWM for 20/360 = 5% of the time,
this is quite remarkable!
 
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