wide range supply

Could get a bit toasty providing +1V at 100 mA. (I assume that "10 watts" doesn't include 1V @ 10A.) ;)

You could maybe put a buck before the boost, and at low voltage, let the current pass through the boost inductor with the converter turned off.

A PFET in parallel with the buck would let you avoid loss of efficiency at higher voltages, and right near +24, you could run both to avoid any holes in the adjustment range due to the wall wart sagging a bit, for instance.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

If the pulse generator drives an external 50 ohm load, 1 volt is only

20 mA! It's at higher output voltages that I'll really need a power limit. I'd probably have a uP so we could do all sorts of presumably intelligent DAC-programmed limits.

At 20 volts into the output stage, my 50 ohms and the customer's 50 ohms is 100, so my internal dissipation is only 2 watts. But 100 volts into a customer short is different. They could drive a bar laser stack or something with low drop too.

(On my cute new all-analog pulse generator, the intelligence comes from a thermistor!)

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

fredag den 21. august 2020 kl. 23.57.05 UTC+2 skrev snipped-for-privacy@highlandsniptechnology.com:

buck-boost,boost or sepic set for 100V output, pfet with source-gate across linear regulator(maybe with a divider to increase voltage) shunting the upper set resistor on the switcher

Phil's buck-into-a-boost is attractive. Here's a nuttier idea--you could convert a buck into a boost with external switches when needed, or revert to buck mode when that's appropriate.

(conceptual boost-mode operation) Synchronous Buck L1 .----. .-.-.-. D1 +24V >---| |--+--' ' ' '---+--->|---+---> +24..100V | | | | | | | | Q1 ||-' --- | | | ||

Fun!

I wonder if there are any sync bucks simple enough that that would work stably. The feedback would have to be really slow to avoid the unstable zero in CCM boost mode. ISTM it makes the volt-second problem a bit worse, since in boost operation the left end of the inductor is at ground instead of +24V.

We really need a fast synchronous version of the uA78S40 or MC34060 to play these sorts of games with. I bet the inventor of the buck regulator didn't think of the trick of grounding the output and letting it pump its ground pin negative.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

The cheap potted LM78xx replacements will do that. They are really slick, for a few dollars.

I have persuaded the LTM8078 dual synchronous switcher brick to make

+24 into -2.5 and -5, or to make +5 and -5.

My original problem here seems to be non-trivial, especially if I want to put maybe 5 on a board.

Sepics maybe? Over a 100:1 output range?

These things are fun to design, but you never know if anybody would want to buy them. It's not enough that *I* think it's cool.

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

Curious specification. You want 10A at 1v and 100mA at 100V?

The different channels need to deliver bigger current pulses into lower output voltages?

--
Bill Sloman, Sydney

I would do it with a boost first, then a buck

Boost has higher efficiency at high output voltage Buck is easier to stabilize, so you can turn down the crossover for the boost

If you start off the AC lines and move down?

In the lab supplies I use I hear clicking sounds when certain voltage points are crossed. They must have more than one internal configuration

On a sunny day (Fri, 21 Aug 2020 14:56:56 -0700) it happened snipped-for-privacy@highlandsniptechnology.com wrote in :

When I need higher voltage AC 60Hz I use my audio amp and a mains transformer in reverse.. PC as signal generator, 50 Hz mains here. (to drive cryo cooler for example) Depending on the step up transformer you could go to several kHz my smaller amp is about 60 W, the bigger 300W.. both are linear, not much RFI. Simple rectifier filter at kHz, use a current sensor to pull volume down (JFET or something). Volume control is output voltage adjustment. There must be some 24 DC audio amp modules around, else a few transistors, classic. Efficiency? important at 10W?

We very rarely connect to the AC lines. Most of our stuff runs off

24VDC from a wall-wart. The better warts are cheap and work really well and are plastered with compliance stickers, presumably real. It's easier to write up a CE conformance report if you use a wart.

Our new rackmount AC source uses a MeanWell 48V, 1KW metal-box supply. I hope no customer asks for a CE sticker on that one! That would take some creative writing.

My new tiny pulse generator uses a 48V wart. The wart accepts worldwide line voltages and comes with a set of international plug adapters. I just linear regulate down from 48, to get +44 to +1, but that's inefficient and won't scale for voltage or more channels.

The abstract problem is, what's a good way to get quiet 1 to 100 volts DC in a couple of square inches of PCB area?

Some of ours do that. They are the heavy ones that probably have a line-frequency power transformer, and they are switching taps with relays.

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

I used to make electric meters, and we did that to test them. I got a gigantic PA amp from a music store (Peavey, 800 watt stereo) and ran a big power transformer backwards for voltage, and used a 190-amp filament transformer to make current.

Ordinary power transformers seem to work fine over the audio range, or more.

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

Do you have any fave bucks that will survive 100V on the supply pin, or even half that?

I'm frequently in need of a decent buck that'll run at 500 kHz or more and handle >40V on the input, generally on account of wanting to make

-18 or so from +24. I usually buck down to ~+13, then invert from there. (It's also an OK rail to make logic supplies from--mine usually don't take a lot of current.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Their only problem for that use is that the input reservoir cap gets returned to the negative output instead of ground, so you have to put in an outboard reservoir.

Nice.

Dunno. Never done any SMPSes fancier than a flybuck or an auxiliary HV output based on the free AC at the switch node.

Customers are so annoying. Fortunately if you ignore them, they go away. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

We've done some SEPICs with the cheap dual inductors. They are a nice boost-buck thing at small additional expense.

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

For a miniature laser driver board, I've used AOZ1282CI-2 (400 mA, 1 MHz, SOT23) for an inverting buck to make -14 from +5, LMR23630 (2 MHz,

3A) for the class-H TEC driver, and TPS61175 (2 MHz, 3A) to make +15. That boost won't take 24V input, but the whole works fit inside a 1" x 1.5" x 1/4" board-level shield can (Leader Tech SMS-205 series).

The board is credit-card sized, stuffed both sides, and cooled via a 5 W/m/K gap pad.

With all those volt-seconds to deal with, your gizmo will probably need a larger-volume inductor for the boost, and to make +100V I expect you'll need a controller chip plus outboard FET, but on the plus side you only need two supplies rather than three.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Rather than battling the high voltage multiple times, I just go down to 12 and split off from there. A couple of people make the little

3-pin things that will work from 72 volts.

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

Yeah, I've come to the same conclusion. Those LMR23630s are pretty good medicine if you don't mind the 650-ps edges. ;) (I always put them in a Faraday cage, so I don't care very much.)

I have this little discrete Schmitt trigger circuit for startup purposes--it runs the +3.3 linear supply for the MCU off +24 until the low-voltage rail comes up. One dual NPN, one BSS84, a diode, and four resistors. That way I can just have the micro deal with the supply sequencing as it likes. (Since Simon has got so good at it, we put Cortex M0+ or M4F/M0+ micros in lots of things that would have been all-analogue previously.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

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boost

LM5164 ?