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

[Spehro Pefhany]

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.

Input current should max out around 25A (80% efficiency) so I suppose
MOSFETs will be the way to go. Forward converter?

Anyone feel like putting together a real design? We need to make a
dozen or two of them, so it just has to work right the first time, not
necessarily be particularly cheap.

Best regards,
Spehro Pefhany

 

[Martin Griffith]

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.

Input current should max out around 25A (80% efficiency) so I suppose
MOSFETs will be the way to go. Forward converter?

Anyone feel like putting together a real design? We need to make a
dozen or two of them, so it just has to work right the first time, not
necessarily be particularly cheap.

Best regards,
Spehro Pefhany

You could start of here
http://schmidt-walter.eit.h-da.de/smps_e/spw_smps_e.html
it even suggests transormer thingies


martin

 

[Paul Mathews]

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.

Input current should max out around 25A (80% efficiency) so I suppose
MOSFETs will be the way to go. Forward converter?

Anyone feel like putting together a real design? We need to make a
dozen or two of them, so it just has to work right the first time, not
necessarily be particularly cheap.

Best regards,
Spehro Pefhany

Do you need isolation? Do you care about weight/size? What is the
actual load? Are there EMI compliance requirements? Do you have
airflow?
Paul Mathews

 

[John Larkin]

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.

Polyphase flyback would be interesting. There are controller chips
around nowadays. It devolves to, say, three 80 watt boost converters.

But what about using standard bricks, Vicor or something, with some
opamps or whatever for charging control?


John

 

[Spehro Pefhany]

Do you need isolation?

No. The inputs are isolated- we're using individual Lambda supplies
from line voltage to 12VDC.

Do you care about weight/size?

No, within reason.

What is the actual load?

Approximately 20 to 60V at 0.1 (?) to 4A, programmable by a micro.
Since it's charging batteries, current control is the ultimate goal. A
trickle charge capability is desirable.

Are there EMI compliance requirements?

No, within reason (the chargers can't interact to the point where
performance is affected). There is some commoning of one side of the
output lines, so a synchronized setup would be preferable so that
current and temperature could be measured without interaction. That
may be just a detail-- if it's designed in from the start.

Do you have airflow?

Yes. I have to assume that the environment may not be air conditioned
and could be fairly hot (eg. Africa) or fairly cold (eg. northern
Canada).

Paul Mathews

Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

Polyphase flyback would be interesting. There are controller chips
around nowadays. It devolves to, say, three 80 watt boost converters.

But what about using standard bricks, Vicor or something, with some
opamps or whatever for charging control?

John

Interesting idea.. the voltages are off standard, but might be close
enough for "turn down" capability. Last brick I used had a pretty
simple op-amp/resistor setup for changing the output voltage. I don't
want custom- they have this great web-based quotation setup for custom
voltages, but IME, a real quote never comes back from it... maybe it's
just a black hole for gathering data. ;-)

Best regards,
Spehro Pefhany

 

[John Larkin]

No. The inputs are isolated- we're using individual Lambda supplies
from line voltage to 12VDC.

OK, the obvious question: why 120 to 12 to 60?

John

 

[Bob]

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.

Input current should max out around 25A (80% efficiency) so I suppose
MOSFETs will be the way to go. Forward converter?

Anyone feel like putting together a real design? We need to make a
dozen or two of them, so it just has to work right the first time, not
necessarily be particularly cheap.

Best regards,
Spehro Pefhany

Presumably you have size or efficiency requirements that preclude
plugging together a ready made mains inverter and a ready made
battery charger?

I would be reluctant to bother doing a design for two dozen units.
Plenty of inverters and 48V 3-stage battery chargers available
cheap, delivered direct from Hong Kong or Taiwan.

The closest thing I found off the shelf with a two minute google
search is this;

http://zahninc.com/DCDC1248160SPECSHEET.html

I'm guessing you want to fast charge a nominal 48V stack
of lead acid batterys. 53V is enough for float charging.
It's probably possible to change a resistor and get a few
more volts out.

Bob

 

[Jim Thompson]

Interesting idea.. the voltages are off standard, but might be close
enough for "turn down" capability. Last brick I used had a pretty
simple op-amp/resistor setup for changing the output voltage. I don't
want custom- they have this great web-based quotation setup for custom
voltages, but IME, a real quote never comes back from it... maybe it's
just a black hole for gathering data. ;-)

Best regards,
Spehro Pefhany

I have a universal charger for laptops... changing the connector
changes the FB resistors to set the supply voltage.

...Jim Thompson

 

[Winfield Hill]

Polyphase flyback would be interesting. There are controller chips
around nowadays. It devolves to, say, three 80 watt boost converters.

My personal favorite for high power levels -
to several kW - is an H-bridge driven with a
phase-shift controller. But these designs
can be a bit cantankerous, and might require
rework or several passes before production.
Once working well, they are champs, however.

We know that there are (were?) lots of > 300W
off-line flyback PC power supplies, made in
huge quantities. So they can't be too bad.

But to reduce 12V current ripple, I was going
to suggest using two high-frequency flyback
ICs with two small transformers, but synced
out-of-phase with each other. I'm not sure
which IC would be the easiest to sync that
way, Spef, would you like some suggestions?

Someone else may suggest a sepic converter.

 

[Clifford Heath]

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?

Automotive class D subwoofer amp with DC isolation removed? ;-)

 

[John Larkin]

My personal favorite for high power levels -
to several kW - is an H-bridge driven with a
phase-shift controller. But these designs
can be a bit cantankerous, and might require
rework or several passes before production.
Once working well, they are champs, however.

We know that there are (were?) lots of > 300W
off-line flyback PC power supplies, made in
huge quantities. So they can't be too bad.

But to reduce 12V current ripple, I was going
to suggest using two high-frequency flyback
ICs with two small transformers, but synced
out-of-phase with each other. I'm not sure
which IC would be the easiest to sync that
way, Spef, would you like some suggestions?

Someone else may suggest a sepic converter.

LTC makes polyphase controllers, and now maybe TI, too.

At 5:1 boost, it can be done with inductors, so no custom magnetics.

John

 

[Fred Bartoli]

Winfield Hill a écrit :

My personal favorite for high power levels -
to several kW - is an H-bridge driven with a
phase-shift controller. But these designs
can be a bit cantankerous, and might require
rework or several passes before production.
Once working well, they are champs, however.

We know that there are (were?) lots of > 300W
off-line flyback PC power supplies, made in
huge quantities. So they can't be too bad.

But to reduce 12V current ripple, I was going
to suggest using two high-frequency flyback
ICs with two small transformers, but synced
out-of-phase with each other. I'm not sure
which IC would be the easiest to sync that
way, Spef, would you like some suggestions?

Someone else may suggest a sepic converter.

What I'd consider WRT to input ripple current is to simply eliminate it.

A 50%+50% duty cycle push-pull stepping up the voltage to something like
65-70V followed by a small buck.

Ripple currents are reasonable everywhere.

 

[Paul Mathews]

No. The inputs are isolated- we're using individual Lambda supplies
from line voltage to 12VDC.


No, within reason.


Approximately 20 to 60V at 0.1 (?) to 4A, programmable by a micro.
Since it's charging batteries, current control is the ultimate goal. A
trickle charge capability is desirable.


No, within reason (the chargers can't interact to the point where
performance is affected). There is some commoning of one side of the
output lines, so a synchronized setup would be preferable so that
current and temperature could be measured without interaction. That
may be just a detail-- if it's designed in from the start.


Yes. I have to assume that the environment may not be air conditioned
and could be fairly hot (eg. Africa) or fairly cold (eg. northern
Canada).


Best regards,
Spehro Pefhany

Since you don't need isolation, and boost ratio is not too high, I'd
consider boost, or boost with tapped inductor, if you want to keep it
simple. If you don't go too high in frequency, you can use a powdered
iron core. The most important component choice will be the fast
recovery rectifier.
Paul Mathews

 

[Alice]

OK, the obvious question: why 120 to 12 to 60?

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[Spehro Pefhany]

Presumably you have size or efficiency requirements that preclude
plugging together a ready made mains inverter and a ready made
battery charger?

They mostly don't exist in this voltage range, not that I can find
anyway, and the ones I've tried don't work very well and have
algorithms that have problems.

I would be reluctant to bother doing a design for two dozen units.

Yes, it's not my first choice, that's for sure.

Plenty of inverters and 48V 3-stage battery chargers available
cheap, delivered direct from Hong Kong or Taiwan.

If I could find something industrial strength at an acceptable price,
I'd buy it.

The closest thing I found off the shelf with a two minute google
search is this;

http://zahninc.com/DCDC1248160SPECSHEET.html

That's interesting. Maximum voltage is a bit on the low side, and so
is output power, so it's not quite there.

I'm guessing you want to fast charge a nominal 48V stack
of lead acid batterys. 53V is enough for float charging.
It's probably possible to change a resistor and get a few
more volts out.

Bob

They're NiMH, I want control over the algorithm- thermistor as well as
voltage depression (and discharge) and prefereably the ability to
change battery technology with approximately the same voltage
(currently 33 cells and 16 cells per pack). I also have to deal with
possible charger-charger interaction. Lead acid is definitely not in
the cards, but one of the Li technologies might be, if it can be
proven safe.

Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

OK, the obvious question: why 120 to 12 to 60?

John

To re-use some existing supplies and because they should be isolated,
and because I don't think it's worth trying to make the off-line part
with the safety issues for a handful of pieces. I certainly could use
48 rather than 12, but I'm not sure it would be that much easier.


Best regards,
Spehro Pefhany

 

[Paul Mathews]

My personal favorite for high power levels -
to several kW - is an H-bridge driven with a
phase-shift controller. But these designs
can be a bit cantankerous, and might require
rework or several passes before production.
Once working well, they are champs, however.

Several years ago, I had a conversation with Laszlo Balogh (TI/
Unitrode) about why they don't push the full-bridge phase control
chips much anymore (UC3875/UCC3895), and he admitted that it was
because there are too many pitfalls in the design of those converters,
including problems with flux-walking due to drive asymmetries in
certain conditions (power-up/down, brownout, overload) and various
MOSFET failure modes associated with that control method. There are
lots of interesting papers in the literature about how to overcome
these problems, but I'd caution anyone thinking about putting
something together in a short time. If you do go that route, start out
by at least including a capacitor in series with the primary.
Paul Mathews

 

[Spehro Pefhany]

Several years ago, I had a conversation with Laszlo Balogh (TI/
Unitrode) about why they don't push the full-bridge phase control
chips much anymore (UC3875/UCC3895), and he admitted that it was
because there are too many pitfalls in the design of those converters,
including problems with flux-walking due to drive asymmetries in
certain conditions (power-up/down, brownout, overload) and various
MOSFET failure modes associated with that control method. There are
lots of interesting papers in the literature about how to overcome
these problems, but I'd caution anyone thinking about putting
something together in a short time. If you do go that route, start out
by at least including a capacitor in series with the primary.
Paul Mathews

Doesn't current mode pretty much get rid of those problems?

Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

You could start of here
http://schmidt-walter.eit.h-da.de/smps_e/spw_smps_e.html
it even suggests transormer thingies


martin

Hmm.. nasty, nasty peak currents, >100A.


Best regards,
Spehro Pefhany