It was "my bad" to have emulated the main supply with a pulse source... doesn't work that way at all, but I can't show the customer's circuitry.
In actual practice a PFC/PWM chip comes alive and the switcher starts. But that "20V" sags since the charge pump can only support ~24mA.
The switcher takes over at 14.5V (about 250ms into the action), the FET gate is pulled low to shut off the wasted power. The gate resistor is actually 220K, but the demo TL431 won't work (because of Iq) to show how "regulation" might be accomplished.
You are trying to amuse yourself by throwing sand in the air. But you don't understand how it works. Will some first year EE student explain it on Larkin ?:-) ...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 was thinking about that, specifically where that idealized 300 volt-peak full-wave-rectified waveform came from. If it is through diodes, there's no pull-down to pump the series RC thing; if it also drives a 24-volt non-PFC switcher front-end, you won't get that waveform. If the startup circuit has to be working before a main PFC switcher starts up, there are all sorts of interesting tangles. If the switcher starts up on its own, what's this circuit for? Standby power for some controls? It would still have to work when the PFC was down.
Right. ROFF is obviously over-constrained, hence my question about power consumption, which you elected to not answer. There's no ROFF value that works sensibly. A much simpler circuit would work.
Does this rig have to work from 90 to 264 volts AC? That, and the Idss spread, gets interesting.
I understand how it doesn't work. And so far, it doesn't.
You've made a pretty quick transition from "I ended up with this..." to "my bad." But you're not done yet.
ps - the answer is just about 1 watt lost, with your values of R1, R2, the TL431, and ROFF. That is, for the record, about 1000 of your customer's milliwatts.
Keep trying.
--
John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
There's roughly 400mW consumed while bringing up the switcher. Drops to ~1mW when turned off.
If the load is shorted ?:-) 212mW in RDROP, 31.9mW in the FET. See, you clearly don't understand how these things work :-) ...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.
You always brag about designing great circuits without "telling." You troll for ideas, then hide behind "proprietary" when you do settle on something... even if you got the ideas here.
Then you have some other circuitry that specifically turns off the startup supply, that is not shown in the circuit that you posted here. What is it?
Your circuit is complex. Something much simpler would work, and would go to very low power all by itself once the main switcher comes up.
Is that worst-case? The fet Idss is min 20 mA, typ 80, no specified max. There is some value of Idss that results in the maximum power dissipation. What is that value, and what is the dissipation? You should be able to tease Idss to dump around a watt in the fet, which is fine if you heat sink it.
--
John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
What's "complex" about it? I need to support 20V at 15mA-20mA for
250ms.
"should be" is not an engineering term. My wife uses that term "should be" a lot while referring to the present administration. Annoys the hell out of me. We "should be" a Representative Republic, but we're a dictatorship, the other branches of government are sitting on their hands and letting Obama do everything by executive order :-( ...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 has a lot of parts. And you won't address the 1-watt dissipation issue.
You are obligated to find the maximum power dissipation point as a function of possible Idss values, and to heatsink such that nothing catches fire.
If the design is for universal, CE-tested use, AC line voltage can go to 264 RMS. That's 373 peak. In that case, the maximum fet dissipation can be teased well over 1 watt; try it. That fet is rated 1.8 watts max. If you sim one case, with nominal line voltage and typical Idss, you are taking risks. Test lab time is expensive; product recalls and fires are more expensive.
Your sim seems to assume 240 line voltage.
--
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
What 1-Watt dissipation issue? Just because you made up some bull-shit issue doesn't make it real.
Poor baby! Go sit in the corner and suck your thumb. ...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's down-right amusing, YOU lecturing me on rigorous simulation. I often do 45 PVT corners.
YOU, You post nothing but vague crap.
Once I decide on a configuration I'll beat the crap out of it to make sure it's a valid design.
Go sit in the corner and suck your thumb and contemplate how many other ways you can think of to pimp yourself >:-) ...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.
In the PDF that you posted, when the startup circuit is back-fed to 23 volts or so by the main switcher, the parts that I've named dissipate about one watt. ROFF alone burns over 800 mW. If you have a workaround for that, show it.
formatting link
Why can't you see this?
OK, you can't calculate the worst-case fet dissipation.
Hey, spin the design as many times as your customer can stand. And have lots of liability insurance, 'cause you're going to be on the painful end of the expert-witness game. And you're being this sloppy, in public, archived forever.
--
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
--
I'm the idiot???
You claim that people often include a series resistor to limit
transient currents and yet, the circuit you show - which seems to be
susceptible to damage from transients - doesn't include the resistor
you claim should be there.
I know you're a pimp, but I don't think you're dense... just a dense asshole. That's not the real circuit. I walked you thru that this morning. Now go away. ...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 said in plain English that a series resistor might be appropriate. In some cases, like a clean low-voltage AC source, it might not be needed. I've done lots of voltage-doubler type supplies with no series R.
--
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
It's what you "wound up with." It's stupid, so now you say it's "not the real circuit." Of course, you won't reveal the "real" circuit... it's proprietary.
Or more likely it doesn't exist. Or it's full of bugs, too.
--
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
incandescent lamp in series, drops back down to low R afterwards, keeps every one happy :)
Actually, a depletion mode mosfet inseries with a network can act as a current limiter, give you low Ron values when not hitting the current wall. That should make the heat radiator police happy.
--
In this instance, since you identified the input as "AC LINE" and the
thread is about mains driven current limited supplies, your
low-voltage driven doublers are irrelevant.
Also, the cleanliness of the source has very little to do with what
will happen when the mains gets switched into the load at different
angles.
Hey, the Blue Angels are buzzing the building. I'm headed for the roof.
--
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
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.