S.E.D is disappearing

Show me.

No, it's not. But you're not even starting the design.

Nope. It's a flash. The numbers are to make the arithmetic simpler.

Figures. No one really wants a challenge. They just want to BS and bitch about not having enough threads that are on-topic.

It's not surprising that you can't read, either.

Now you're starting to see the problem. How much capacitance is needed? How do you do a 1V current source? There is more than meets the eye here. But obviously the people here aren't up for the challenge.

So, take the two series LEDs and connect 'em in a ring (antiparallel). Feed that from a transformer secondary, and pulse the center-tapped primary with the usual two-phase PWM signal. Allow/add stray inductance on the primary, but you're feeding it AC, and the LEDs are their own catch diodes. Input voltage not critical, just make sure the current limit and turns ratio meets the LED drive requirement.

Inductor and transformer impedance only have to handle circa 3V and 200 us, so a saturation rating in the 1 mV-sec range is generous.

As for me, I'd hate to try to SEE by blinking lights; I've got a perfectly good strobe or three, but only bring 'em out for special occasions.

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ation) into a series combo 6V LED load for 200us (again no precision specif ication) at 100Hz rep rate ( again no precision specification), and then so me mumbo-jumbo about a 250mA average current draw ( with no precision speci fication) and a 7V source (with no precision specification)... and what the heck is a storage specification ( no environmental specification). You're just rambling. Talk about chaos.

What's driving this thing? CMOS compatible input? What VDD?

Sure, why not? GO ahead. Think about the irrelevant, but easy, parts.

Actually, that's an interesting idea. It still doesn't solve the problem.

Would it help if they're IR LEDs? It doesn't change the problem though.

I detect a bridge dweller. If perchance you're serious, you can tell us what you've worked out so far. But it looks to me like a set-up, a situation you use to criticise all offers of the semidefined problem.

NT

So I'll put you in Blobby's group. You have no idea how to do it either.

I don't have the full solution but I've done enough arithmetic to show how it has to be done.

I thought people wanted a challenge but, as you know, I can talk politics, if you'd rather. Just don't bitch about it.

There's not much challenge. 0.5 ohm and a 1F supercap handles the storage and input current smoothing. Add a polymer in parallel if the cap ESR is too high. The LED current limiter is just a mosfet with a

ok, I figured you were trolling.

NT

No, it's a real problem that I have to solve, eventually. The specific circuit I need this week isn't source current limited but the rest is the same. The next version will have limited current. It's a rather tough problem and it appears even the blowhard "experts" here aren't up to the challenge, nor really want to be challenged.

LOL. Yeah, what's the source impedance of your supercap? How long is it going to last at 100Hz?

It does take a while to spot what his little game is. KF'd here on JT's suggestion.

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You are obnoxious. Get someone else to help you understand simple electrical basics.

May I jump in?

I found some 1F, 7.5V supercaps (AVX) in stock at Mouser. The ESR is specified at .180ohm at 1kHz and .360ohm at DC (whatever that means). I don't know how to interpolate between the two.

However, you can use 10 of them in parallel. That results in .018 or .036 ohms ESR which might be reasonable.

The 10 amp pulse at 10% duty results in 1.414A RMS current and that means that the max dissipation in the supercaps will be 720mW or less. But that is divided by 10 so the individual cap dissipation is 72mW.

The peak current is rated over 2A, so that should not be a problem.

This addresses just the storage concern.

If he weren't trolling he'd have answered the questions himself

NT

I will assume that the 7V is just enough to overcome series resistance of wiring, traces, series switch, and LED internal resistance.

To charge the input bulk storage capacitor, I would use either a small processor with a PWM output or a dedicated PWM device with peak current detection for on-time termination to limit the peak current to 250mA.