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From: Jim Thompson on 12 Jul 2010 21:45
On Tue, 13 Jul 2010 11:41:24 +1000, Grant <omg(a)grrr.id.au> wrote:

>On Mon, 12 Jul 2010 17:17:32 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote:
>
>...
>>There should be a wrap setting in your newsreader, in the same section
>>where you set quote (>>>) marks.
>
>Yes, I have it set to 250 to suit another place (lkml) ;) Even though
>Linux CodingStyle specifies max 80 char lines, if somebody exceeds it,
>one cannot rewrap that line, as the meaning of the code would change.

I'm an 80 character kind-a-guy ;-) So I set my wrap at 70 to leave
room for multiple re-quotes before weird wraps screw up the content.

>
>I'm quite happy putting in manual newlines, been doing that writing
>code for so many years, it is second nature ;)
>
>Occasionally I'll break the convention on Usenet when reporting or
>responding to stuff that exceeds 80 cols and looks totally messed up
>if line-wrapped.
>
>Current nature of usenet is pretty messed up anyway, probably because
>self-moderation doesn't exist for lot's of people?
>
>Grant.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Obama isn't going to raise your taxes...it's Bush' fault: Not re-
newing the Bush tax cuts will increase the bottom tier rate by 50%
From: Jan Panteltje on 13 Jul 2010 10:01
On a sunny day (Mon, 12 Jul 2010 17:28:44 -0500) it happened "Tim Williams"
<tmoranwms(a)charter.net> wrote in <AGM_n.7670$Zp1.1223(a)newsfe15.iad>:

>"Jan Panteltje" <pNaonStpealmtje(a)yahoo.com> wrote in message
>news:i1g15t$l60$1(a)news.albasani.net...
>> I really have not tried any HV MOSFETS other then BUZ44A (400V) many
>> years ago.
>
>Odd. A shame, I guess? 500 and 800V FETs are handy for
>around-the-world supplies, 500V for PFC and forward converters, and
>800-1000V for flybacks.

Yes, but one cannot do everything at the same time ..


>IGBTs are better than FETs above 300V, and are cheaper per amp, but good
>luck finding any inbetween 600V and 1200V, those seem to be the most
>popular voltages for some reason. They aren't all that popular for
>lower currents, where FETs still dominate AFAIK. They also seem to be
>more fragile, not tolerating excess voltage in forward or reverse
>(co-pack IGBTs, with diode, solve the reverse problem for the most
>part). It's kind of weird, they're rated for avalanche breakdown
>voltage (at a current of like 1mA), but I have never seen an energy
>rating on them (like FETs have). As far as I know, more than a few mA
>causes destruction for some reason.

Have not used IGBTs either.... IIRC the early ones could latchup, enough to keep me away.




>> OK, let me try to explain my way of thinking, maybe bit vague for
>some,
>> but it goes like this:
>> It is much easier to keep a pendulum going then moving it fast left to
>right
>> or forward backward, takes less energy.
>> I like resonant, way of least resistance.
>> As you have capacitance in the transformer windings plus lots of other
>places,
>> why not make use of it and tune things.
>
>Ah, but how much energy do you really burn in switching? In general I
>mean. And note that, in general, "tuning" (which I guess does refer to
>resonant or quasi-resonant snubbers, tuned circuits, that sort of thing)
>is not possible, and obviously enough it increases reactive current,
>which may be troublesome. A generalization can't be made, but it might
>be anywhere from the miniscule amount of q C * deltaV or Phi L *
>deltaI parasitics, to several times load current typical of LLC circuits
>and etc.

'Not possible' is a bit strong statement perhaps.


>The thing about tuning, and something you absolutely must remember: it
>doesn't *help* you. If it's there unavoidably, you should take
>advantage of it; but don't be under any illusion that adding reactive
>components will make a circuit work better.
>
>Two extremes make a great example. One, a high voltage generator with
>huge capacitive secondary, and the other, a forward converter with
>essentially resistive behavior.
>
>For the HV generator, you could drive it with a single transistor (as
>your laser supply does), with the disadvantages of: turn-on transient
>switches full capacitance big current spike, frequency and duty
>cycle must be set to maintain class E operation, leakage inductance must
>be low enough (or primary capacitance high enough) to minimize overshoot
>at the primary (otherwise you need voltage peak snub), and the extra
>reactive current causes increased heating in the supply filter cap, some
>amount of current in the transistor and now-required damper diode, and
>additional heating in both the primary and secondary due to that
>capacitive reactance.


To clarify things a bit, that TIP140 is a darlington, with build in resistors
and it also shows a reverse diode.
I did mention 'look up boost diode' in a previous reply in this thread.
So what happens is a bit different scenario then you describe here,
how else would you explain the parabolic waveform on that collector?
Especially with regard to the drive signal.
The fact that it is a darlington is what makes it possible to drive it directly from a 555.


>Further advantage could be taken by driving the transformer with a
>[dynamic] current source, i.e., an inductor. This doesn't work very
>well in half wave, but it does work well in full wave, e.g. PP or full
>bridge. You get a Royer oscillator, where the voltage swings in
>sinusoidal humps, both transistors operate in ZVS, with no reactive
>current flowing through the supply (it's all squashed by the series
>inductor, which can be arbitrarily large), and the output is a fairly
>clean sine wave, limited only by Q and switching speed (during zero
>crossing, when both transistors are on simultaneously, a flat spot
>occurs).

I did one once with 2 thyristors, couple of 100 amps, transformer the size
of a small PC, 50 Hz :-)
It had a good magnetic fuse, when overloaded the thyristors would not switch off reliably.
Was just a lab experiment.
Ran from a 48 V, 1 kA, size of a small room, NiCad
:-)


>The basic point is, since you have capacitance, you might as well use
>it. This might involve cancelling the reactance with inductors, or using
>a capacitor-friendly approach, like CC drive.

I am glad we agree, that was my point also.


> Keep in mind that, by
>increasing absolute current and voltage, you are increasing losses,
>maybe not as much as an explicit snubber, but some nonetheless.
>
>The forward converter, on the other hand, works like this: the
>transistor turns on, current shoots up proportionally, then it turns off
>and current goes to zero. There is nothing to "swing" and start the
>cycle, nor anything to end it; timing is arbitrary. Whereas the
>mechanical analogy of a pendulum seems to be easier, this example is
>more like dragging a weighted block across the floor: voltage (velocity)
>doesn't go anywhere until you apply a certain amount of current (force,
>static coefficient of friction). When you apply that voltage in either
>direction, a proportional current (including direction) flows. It
>doesn't help you to apply reactive forces (vibration, hammer taps,
>etc.), because friction is friction (note: the dynamic coefficient of
>friction is always lower than static, but in this electronic analogy,
>they are equal). So either way, you have to apply the work, and yes it
>takes some effort to get up to that level of force/velocity, but you
>don't have anything to help you, and it's a completely lossy system
>anyway, so it won't even 'feel' right. You'll have to apply so much
>reactive energy that you'll definitely increase losses trying to reach
>an underdamped (feels-kinda-resonant) system.

Well, conservation of energy hold of course, unless you go nuculear
and convert some from - to - mass. E = m.c^2


>Now, this is all obvious to us, but it's amazing that it escapes the
>overunity types.

If you want to rant about perpetuum motion machines?


> They are quite fond of two things:
>rotating/oscillating machinery and circuitry, and anything that seems to
>operate on little enough power that it "feels" lossless to the hand.
>One silly example uses several miliwebers of seriously strong
>supermagnets, arranged without any pole pieces whatsoever, in a ring
>glued to a disc, such that the magnetic field on the periphery seems to
>ramp up, going around the disc. The result is, when another magnet is
>held near the disc, the magnets in the ring push away, and as the field
>ramps down, the ring is propelled. Obviously, it won't be propelled a
>whole revolution, because there's a step where the ramp begins again.
>The astute operator just happens to nudge his wrist at this moment, thus
>apparently making a "magnetic motor" that rotates without "any" energy
>input whatsoever; the magnets seem to push themselves around! I expect
>the two effects at work apparently convincing this operator of the
>energy arises from 1. the force being almost entirely radial ( force
>that does no work), except for an imperceptible tangential force (doing
>the actual work), and 2. because the amount of force required to spin a
>disc on a bearing is small, the energy input (that nudge of the wrist)
>is also small, perhaps being imperceptible as well, giving rise to the
>illusion that it happens of its own energy.
>
>And apparently Tesla himself was convinced of this fallacy.

Well you must be aware that now you are attacking very respected people....


>Reactive
>power is energy, not power. It is fundamentally impossible to
>accumulate energy in a resonant system -- it will always come to
>equilibrium for constant power input! Such belief has even been
>professed on this newsgroup from time to time -- Jim Thompson once spoke
>of an LC sinewave oscillator he constructed which required no "gain
>correction", like the classic HP Wein bridge oscillator has.

But that person is a politically supported great designer who even designed chips for Garmin 20 years ago.
You must be wrong.
Do you not think the laws of nature make an exception for him?


>This is of
>course another fallacy, since a true linear oscillator will grow without
>bound, but given a sufficiently high Q, a small constant-current nudge
>(of constant amplitude -- not a linear system!) to a parallel resonant
>tank will appear as linear (low distortion) as anything else. The same
>is true of a series resonant circuit and small constant voltage
>stimulus, but series resonant tanks are harder to implement on the small
>signal level; for a resonant voltage of 5V and Q 100, you have to
>drive the thing with a perfect voltage source of only 50mV, whereas the
>parallel resonant, carrying 10mA reactive, can be tweaked with only
>0.1mA.

I think I lost you here, but am not too worried about it.
Just one question: Do you have a theory on gravity too?

Anyways Tim, take it easy.
Did you read this paper on quasi-resonant and resonant converters?
http://www.powerdesignindia.co.in/STATIC/PDF/200901/PDIOL_2009JAN21_PMNG_TA_01.pdf?SOURCES=DOWNLOAD

From: Jan Panteltje on 13 Jul 2010 11:58
On a sunny day (Tue, 13 Jul 2010 08:09:06 -0700) it happened Fred Abse
<excretatauris(a)invalid.invalid> wrote in
<pan.2010.07.13.08.58.18.421396(a)invalid.invalid>:

>On Mon, 12 Jul 2010 23:38:15 +0000, Jan Panteltje wrote:
>
>> To clarify things some more,
>> for example IIRC in the TV the HV coil is tuned to the 3rd harmonic of the
>> H frequency, 3 x 15625 Hz.
>
>Common misapprehension.
>
>The *leakage inductance* of the HV transformer is tuned to either the
>third, (early monochrome), or fifth (color) harmonic of the *flyback*
>frequency, ie. three or five times the reciprocal of twice the flyback time.
>
>For a 10 microsecond flyback time, that's 3 or 5 times 50kHz.

OK, I stand corrected:-)

>The effect is to flatten the peaks of the (half-sine) flyback pulses.
>
>At one time, it was done by winding a few turns under the HV winding, and
>connecting an adjustable LC circuit to that. Latterly it was done by clever management
>of interwinding capacitance, hence self-resonant frequency.
>
>It's surprising how many "authoritative" texts get this wrong.
>
>--
>"For a successful technology, reality must take precedence
>over public relations, for nature cannot be fooled."
> (Richard Feynman)
>
From: Jon Kirwan on 13 Jul 2010 13:56
On Mon, 12 Jul 2010 21:24:02 GMT, Jan Panteltje
<pNaonStpealmtje(a)yahoo.com> wrote:

>No clue what 'OLE' is

You've missed out on Microsoft culture! It is "Object
Linking and Embedded" and is related to the IOleObject
interface.

Jon
From: Jan Panteltje on 13 Jul 2010 18:13
On a sunny day (Tue, 13 Jul 2010 10:56:57 -0700) it happened Jon Kirwan
<jonk(a)infinitefactors.org> wrote in
<c2ap36dqcvcsjg9r633kt7fjkki5p4jckm(a)4ax.com>:

>On Mon, 12 Jul 2010 21:24:02 GMT, Jan Panteltje
><pNaonStpealmtje(a)yahoo.com> wrote:
>
>>No clue what 'OLE' is
>
>You've missed out on Microsoft culture!

True, I burned my xp disk :-)


>It is "Object
>Linking and Embedded" and is related to the IOleObject
>interface.
>
>Jon

Well I do not know what that is either, and am happy that way :-)
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