you're wanting to run it off the ripple? the higher frequency will help a bit, but the voltage swing will be much less, less predictable too I expect.
-- ?? 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Costello :-)
But that's the real problem: egg-chicken-egg... who runs the control loop? ...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 |
I love to cook with wine. Sometimes I even put it in the food.
I used a variation of that to make a 12.6V (DC) tube heater supply from a 30V transformer. I call it a "pulse regulator."
The series cap is still a good idea because the charge pulse is going to be limited by 'something', even if it's only Rdson, and the cap would cut down on the peak current spikes.
Then how about clamping the cap low side to ground after the output filter cap has gotten enough juice? Need another series switch or diode, of course. The power dissipation would be much less doing it that way since i*Rds(on) should be
The series current-limiting cap dissipates no power, so it can be shorted by a low voltage switch. If it drives, say, the input of a bridge rectifier or a 2-diode restore thing, short the input of that. It becomes a bang-bang regulator. If the controller is to be a custom IC, a modest amount of complexity is free, so some intelligent zero-crossing thing would be appropriate. But just dumb bang-bang ought to work.
This is one variation:
The first diode can be the fet's substrate diode, saving one part.
This is like an alternator regulator that shorts the alternator output with a triac, to get regulation.
People often add a series resistor, for spike protection, and that will dissipate some power, but no more than it would with a zener shunt regulator.
Yup, that's pretty much what I had in mind, I don't think you need the left diode- either the body diode or turning the MOSFET on will work (assuming custom ICs are like discretes, which they may not be).
Making the other diode into a synchronous MOSFET rectifier might be worth it.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
that looks just like a charging circuit I tried once, only I didn't have a ripple cap. All I had was a - feed back zener and a bjt with a by pass diode, at the time. I only used a 24V AC source but the idea was to allow it to have a constant short with out internal heating.
I wanted a pulse type of charging instead of constant DC.
10u 600V SI 30 Hz pulse out || -||-+--+------+----+->|-+-+---------------------+ || | | + AC line in | | z Max Voltage limit Diode | | A | | | surge clamp z | | A + HV NPN V Back flow stopper -(diode too) | | - 5 watt + \| | | |+--------+-------+ |
inrush current will destroy it.
-- ?? 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Of course it was the egg that came first. All chickens come from eggs. But not all eggs come from chickens. The first chicken probably emerged from a reptile egg.
Another answer is that neither the egg nor the chicken came first - it was the rooster!
Paul
It came from a bird similar to a chicken.
-- Reply in group, but if emailing add one more zero, and remove the last word.
Where did that bird come from?
From another bird. Dinosaur DNA has latent "feather subroutines" that were "exposed" by evolutionary processes.
-- Les Cargill
...Jim Thompson
I'm sure I remember seeing a chip made for standby supply that did something like that
something real simple maybe, series pfet, clamp gate when input exceeds desired output
-Lasse
As I mentioned, and you snipped, people often include a series resistor to limit transient currents.
C-limited supplies are commonly used for things like LED night-lights. It does take good engineering to do them right.
-- Not quite true, since no dielectric is lossless.
Bad engineering can create grim outcomes. Better to not do that.
Idiot whining again. That's pretty much your skill set.
Idiot whining again.
A 1/4 watt resistor dissipating 1/4 watt in a confined space won't last long. At 240 volts, 2 mA dissipates a half watt.
What an ass you are.
I certainly don't make night lights for production. My stuff sells for kilobucks, not cents. I have done a few for myself, for personal applications.
I assume that JT has some commercial application in mind, with a low vampire power budget, and has no ideas of his own.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
That looks equivalent to a shunt zener. The NPN runs in linear mode and gets hot.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Yep, extremely low power, switcher start-up circuitry, and I certainly do have ideas of my own: controlled surge, then, once switcher starts, auxiliary supply is turned off _completely_, no capacitor current at all... done with a readily available 15 cent part.
Students! What is the beginner's error in this...
Other than it being general Larkin crap ;-) ...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 |
I love to cook with wine. Sometimes I even put it in the food.
It does the same as a single zener, but is more complex.
No, my circuit goes into zero dissipation mode when it doesn't need to charge the cap. The low-voltage shunt mosfet (or NPN) could be integrated into a controller chip. Maybe Jim can patent the idea.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
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