12V->60V @3-4A SMPS design

Spehro Pefhany schrieb:

Hi Spehro -

Do you received my private email?

Regards - Henry

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Spehro Pefhany wrote: > To make a battery charger circuit that will run from a 12VDC > regulated supply and produce (up to) 60V at 3-4A, what SMPS topology > would be recommended? I've gotten the suggestion of a flyback, but > 240W seems a bit on the high side for that. >

The absolute simplest power control scheme would be hysteretic current control of the the boost topology, which can be paralleled in constant current mode. This brings up that 20-60V output at 0.1-4A output current. You need to translate this to constant current mode programmable from IL->IU with what compliance, and float charge constant voltage programmable from VL->VU over what current range. Usually a table or graph required here. That is the easy part. The hard part is tying in all the charging algorithms and fault protection as a function of battery chemistry. TI has that BQXXXX series of multi-chemistry battery charging control IC's. You're going to need something like that as either the finished IC or embedded/emulated in a PIC controller or something. The finished circuit will be simple enough, but the design effort will be non-trivial.

Yes...

I'm really not worried about the algorithm.. it's less than a page of C to implement the most complex NiMH algorithm used by chip makers, including recovery from over-discharge, which the present micro-based "commercial" units don't properly implement. The battery manufacturers also publish (somewhat incomplete) information which is useful for charge termination parameters for a given cell.

Iout = f(Vcell(t), t, T(t), ncells)

Agreed. But not a crazy amount of work.

Best regards, Spehro Pefhany

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Yes, Henry, thanks. I'm going to look at your German patent over breakfast. ;-)

German Patent office-- Fusball & Technik?

Best regards, Spehro Pefhany

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Go with the fashion, "digital power". Compute PWM of the boost converter drive(s) based on measurements.

John

If you can't get OTS then the best topology is the Boost, similar to a flyback but no custom transformer, the push pull and forward converters have discontinuous input current and custom transformers. Any resonate topology is not viable at low voltages. Your 25A input current is better handled with two interleaved boost channels 180D out of phase. The UCC2820 will handle all the drive functions at about 200KHz PWM.

If the input inductors are still two big, go to three or four channels at

120D each, the inductors would be OTS. This would cut your output storage caps in half. It is always a good idea to use more silicon and spread the heat. At 90% efficiency, that is 27 watts of power loss. This can be increased to about 93% with synchronous rectifiers for the high side diodes.

YMMV Harry

So long as a glitch doesn't cause smoke, I'd be happy to do so.

Given the voltage range, I'm not sure about the boost converter topology though. I can't go much under 12V without running into problems at the low end with a simple boost converter. Best regards, Spehro Pefhany

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Thanks very much, Harry, we'll take a close look at doing just that.

Best regards, Spehro Pefhany

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Spehro Pefhany schrieb:

I don't know how you reached there :-)

You can either use:

-

or better there:

-

Maybe you get a session timeout. Start over.

From espacenet there is a auto-translation link. Translation looks good for being automatic. I let translated it there:

Hope that helps.

cu - Henry

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I did a 12V car battery, to 50V at 3Amps boost, for a stepper motor supply. Uses an ETD44 with 10 turns of 6mm tri-rated. Single BUKxxx (can't read it) with 2"x3" heatsink. PWM gate drive and seperate current sense resistor and comparitor to kill the gate on any overcurrent. Took about an hour to design and build. Sadly, this was before I learned that these things are far too complicated to be designed so casually and I lost confidence. Still running after 6 years though.

I need to do something casual like that sometime soon, to drive a servo'd rcar rooftop antenna rotator... so if you could casually answer a couple of questions I'd appreciate it.

Did you do a boost, flyback or some other topology?

On what is tri-rated wire actually rated?

Clifford Heath.

[Sounds interesting project!] 'Tis a standard 'Boost' ie, Supply > Inductor > Fet > deck. Best I remember it, is that "Tri-rated" is multistand wire with insulation rated for a working temperature range up to 105 degC and has some approval details printed along it's length. (as cable, nothing special).

The other week and suspicious of the size of some "10mm^2 tri rate", I miked up the cores, counted 'em and did the sums. Turns out it was 7mm^2. Looks like the world Copper shortage is having an effect. Got to keep stuff casual as SMPS topics seem to intrude on a lot of jealously protected turf and delicate egos. Hence It'd be tantamount to iconoclasm to dare mention how straightforward my recent design was for a customer's 1400W boost :)

Thanks John. I'm not familiar with working at these power levels. Though I think I understand most of the theory, I'm sure in practise that learning layout skills will be interesting.

. We go transmitter-hunting once a month. A number of teams have power-rotated antennas with all kinds of DSP hooked up to the RSSI, but when you get an intermittent transmitter they often miss the pulse simply because they're pointing the wrong way. Hand-rotated antennas work well, but need to be smaller in size.

My notion is to build a rotator that can hunt and circle near a manual (or maybe even automatically detected) likely direction, potentially synchronizing with a periodically-pulsing transmitter. Computer control means it can be made not to wind up the cable (no more than one turn each way), so no slip-ring coupling is needed, and compass information from the GPS means it'll keep on target as the car turns corners. I have a nice 18:1 worm-drive gearbox with a 1" output shaft, and a powerful DC servomotor from an old HP 7978 tape drive - about

2Kg, driven by a linear amp from +-45V supplies! I'll use PWM not the linear, but just need more than 12V.

When you get close, you jump out and run with a hand-held Yagi+sniffer. One of the local guys builds this nice bit of kit: . This is the device that requires the dual-gate GaAs-FET I was asking about recently, for its combination of sensitivity, low noise performance, and huge dynamic range.

Clifford Heath.