Programmable tracking pulse supply.

On 20 May 2015 15:13:03 -0700, Winfield Hill Gave us:

Only bifilar. At that frequency, I would use a Litz wire. Plenty of cloth wrapped stuff real cheap out there. Huge performance gain.

Awesome numbers! 300mA @ +/- 15V... I can use some of those.

George H.

Arrgh! Leessee, the Inverse SEPIC, or zeta converter topology accomplishes that goal, moving the ripple from the output capacitor to the input capacitor. But it also requires moving the switch, which breaks the cute single-switch scheme of the SEPIC + Cuk design. You have something else in mind, I imagine.

My mistake, sorry, my test limit was 100mA. To go to 300mA you'd want a smaller inductor, 33 uH, etc.

I'm a huge fan of litz & have a good stock of various types I've special ordered. But this isn't a high-power app, high Q isn't important, and stocked (Mouser) off-the-shelf transformers are a big plus. The good 0.1% performance data is a clue that further enhancement isn't needed. My converter has a 0.45W loss at 3.3W out, 84% efficient, but my application (1ms, 40W pulses, once a second) consumes 40mW average power and the 84% efficiency will only cost 6 milliwatts.

Wow, that's an expensive part, the LPT4545. Looks like 1.5USD. You can make an entire separate supply for a lot less than that price

Something like an inverting boost, perhaps MHz switching device

Cheers

Klaus

Use iso-optulator?

Yes, it is expensive, $10 at Mouser qty 100, and $5 at Avnet, qty 1k. Don't know why, ask Vishay Dale. But I like its low leakage inductance (and I had gotten 30 of them on eBay for a song). The LM2671 is $1.50 and my preferred NCV8852 is $1.44 This design is for folks with no electronics experience, so I want off-the-shelf parts. Clinical app where cost doesn't matter much, pulsed AC electroporation.

I have a new favorite candidate controller IC, TI's TPS40200. It has a programmable soft start.

And, I've discovered that moving the diode to the other side of the secondary, and adding a capacitor, would turn the positive side into a zeta converter, see TI app note slyt372.

Taking feedback from the zeta converter side would eliminate a RHP zero, allowing for simpler, faster loop compensation than a SEPIC.

Or an iso-oculator.

Or a couper-optler.

piglet

Here's an update, with unbalanced-load measurements.

Executive summary, performance: With matched loads, 0.1% at 5mA, < 0.4% to 100mA. With unbalanced loads, observe -1.2% and +0.5% at 55mA mismatch, -2% and +1% at 125mA mismatch.

(In both cases a small balanced load (10-20mA) was required to tame the beast; with no neg load, un-reg pos side sagged -7% with a 100mA load.)

Much better than my 5% goal and a predicted >10%.

This shows it's possible to make an reasonably- accurate dual tracking supply with just a single switcher IC. The inductor must have low leakage inductance to its secondary, < 1%, and a modest minimum load (5 to 10% of max) must be employed.

- W> Joerg wrote...