This series is really cool:
Depending on which of the pins you ground, it will convert a positive input to a positive or negative output.
-- John Larkin Highland Technology, Inc lunatic fringe electronics jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
well, a buck and a buck-boost are kind of similar
==== (1)----. .--+---mmmm-+--(3) ---- | | ---. | | | | | `----------magic | | `--|
Of course, the same is true of the $1.50 eBay buck converters. To make a negative supply, you ground the output apply power between there and the +in wire, and let it pump its 'ground' pin negative. (You knew that already.)
Cheers
Phil Hobbs
73-2-ND/4006941
_oscillator1.htm
If it existed.
We were talking about transformers rather than inductors. Even with inducto rs one has to be aware that a small 100uH inductor will saturate or burn ou t rather earlier than a larger (and more expensive) part. If you know enoug h to be aware of self-resonant frequencies, the situation gets even more co mplicated.
If you put in a little more effort you might be able to find a coil winder who didn't take weeks.
We were talking about transformers, rather than inductors. Even so "tons" i sn't a useful measure.
If they provide the performance you need, fine. +48V from +5V USB doesn't s eem to be a mass market application.
This thread doesn't seem to have thrown up a specific "standard switcher" f or bitrex's application.
Vapour-ware is so much easier to generate.
-- Bill Sloman, Sydney
Does that always work? I hadn't thought it through.
Given this horrible flu thing that I have, there are lots of things I'm not thinking through. I think I'll draw a schematic; that's easy.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Den onsdag den 22. juli 2015 kl. 19.37.31 UTC+2 skrev John Larkin:
it is shown in some datasheets/appnotes
-Lasse
I do it a fair amount with 150 kHz Simple Switchers (my fave) and have never had a problem. You design a buck that goes from Vin-Vout to
-Vout. The two issues are:
Get well soon!
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
It's well past midnight for me, sorry excuse, but a cap multiplier inside a DC loop in a buck or boost , what the heck is that?
Cheers
Klaus
Capacitance multipliers are amazingly good at cleaning up SMPSes, but they're a bit squishy on the DC regulation.
If you close the DC loop of an LM2594 (or something like that) around the emitter of the cap multiplier, and the AC loop around from the switcher's output, you get the best of all worlds: decent efficiency and very very low noise.
It's pretty simple: normal buck + cap multiplier, FB pin driven by a resistor from the cap multiplier output (to keep the regulation reasonable) and a capacitor from the FB pin to the SMPS output (to keep the loop stable).
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Ok, but for the efficiency, you loose some power in the capacitance multiplier. Like those made for class A amplifiers, right?
Cheers
Klaus
Don't know about class A amplifiers, at least if you mean audio. A cap multiplier is just an emitter follower hung on an N-pole RC lowpass.
For what I do, the tradeoff is generally between losing a bit of efficiency on a switcher, or having to use a shunt-regulated cap multiplier as a linear regulator, because switcher noise is intolerable.
As I often repeat, "there's SMPS quiet and then there's instrument quiet."
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Oh, and if you're desperate for that last half a volt, you can use a low-sat NPN and source a little current into the RC from the input supply. That'll reduce the dropout voltage. You do have to keep enough headroom for V_CEsat plus the peak-to-peak ripple.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
-- As if it wasn't self-serving: "The circuit is probably best known from Jim Williams' series of application notes for Linear Technology, on high frequency inverters for driving cold cathode back-lights used in laptop computers (application notes AN45, AN49, AN51, AN55, AN61, AN65)." These apparently were Linear Technology's most popular application notes for quite a while.
so
so?
tbe
lock
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-2-ND/4006941
you
tuctor - would work well. MOS-FET transistors do a bit better than bipolar t ransistors, but Baxandall's paper rather pre-dates them.
cillator1.htm
eb-site
The point was that what I was putting forward wasn't my low distortion osci llator, but rather Peter Baxandall's Class-D oscillator, which has been a s uccess story in a coupe of applications.
out > >the Baxandall label.
Someone from the UK e-mailed me the story about giving the Baxandall circui t to a Linear Technology rep to answer a question that Jim Williams had had the reps put around. They weren't prepared to make a big revelation out of the story, which was old - Linear Technology's AN45 was published in 1991 and the Baxandall style cold-cathode driver is figure 36 amongst a bunch of other circuits, so it goes back 25 years, and Jim Williams is dead.
rent mirror rather than the feed inductor, but that's not the low distortio n oscillator I'm working on at the moment.
Completeness.
e an idiot, but you really don't have to do it quite as often as you do.
Your famous difficulties with comprehending complex sentences may influence that point of view.
And why post something now? You are reacting to a post I made on the 19th J uly 2015. You are slow, but six weeks is a long time.
-- Bill Sloman, Sydney
The Royer and Jensen circuits go back to 1954 and 1957 respectively and so predate Baxandall. Both were still known in the late 70s textbooks. Are you saying that Jim Williams got the idea from Baxandall but credited Royer?
piglet
ithout > >the Baxandall label.
rcuit to a Linear Technology rep to answer a question that Jim Williams had had the reps put around. They weren't prepared to make a big revelation ou t of the story, which was old - Linear Technology's AN45 was published in 1
991 and the Baxandall style cold-cathode driver is figure 36 amongst a bunc h of other circuits, so it goes back 25 years, and Jim Williams is dead.current mirror rather than the feed inductor, but that's not the low distor tion oscillator I'm working on at the moment.
The difference between Royer and Baxandall is the inductor in series with t he centre-tap.
Royer doesn't have it, and produces square waves (usually with spikes at th e switching transitions).
The Baxandall class-D oscillator produces sine waves. They aren't perfect s ine waves, but a couple of percent of third order harmonic and progressivel y less higher order harmonics beat the pants off a Royer inverter.
makes the Jensen inverter a variant of the Royer approach.
Royer's paper, which I did see once, back in 1970, made a lot of fuss about using saturating transformer cores and driving them into saturation, which isn't actually necessary nor a good idea. Letting the drive transistors co me out of saturation works just as well.
As far as I can tell, Jim Williams was given a copy of a schematic of a Bax andall inverter, but no reference to Baxandall's 1959 paper, and cited Roye r's paper as the closest thing he knew about to prior art. It was a bit sil ly.
-- Bill Sloman, Sydney
Yes, I think it is a tricky topology to get pure sine waves from. When voltage fed you have to ensure a small non-conducting dead time when both transistors are off. When current fed (by inductor) that dead time would be lethal and instead an overlapping conduction time is necessary but that places both transistors as a dead short across the resonant tank. Is that why you are trying a current source instead of inductor?
piglet
ct sine waves, but a couple of percent of third order harmonic and progress ively less higher order harmonics beat the pants off a Royer inverter.
The Baxandall circuit doesn't bother about non-conducting dead time - it pr edates MOS-FET swtiches, and doesn't care much about both BJT transistors b eing slightly on - but not saturated - at cross-over.
Life gets more complicated with MOS-FET swtiches.
describes as circuit that's guaranteed to start-up (note the worst-case Vgs difference between the switching transistor models) and not draw too much current when it's working. It's not something I'd build in real life, but i t works in LTSpice. The .asc file is on the web-site.
The current mirror delivers a tolerably pure half-sine wave current into th e centre tap, which the inductor doesn't. There's nothing more to it than t hat.
-- Bill Sloman, Sydney
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