Good day,

Can Push-pull go Bi-directonal?

I need help with a circuit where I can switch Battery DC power into a transformer (Ferrite/Toroidal) Primary so that it gives higher/twice voltage on the Secondary (AC) and when a higher potential AC is fed to the Secondary, the power is reversed and the battery gets charged instead.

Thanks.

 

It might be possible, but you'd need a lot more circuitry than just a push-pull semiconductor pair and a transformer. For starters you would need a proper battery management system to ensure the battery was correctly charged according to its chemistry, plus means to regulate/limit the input AC, plus means to reconfigure the push-pull pair as synchronous rectifiers.
It would be a lot simpler and cheaper just to buy an off-the-self DC-AC inverter and universal switch-mode power-supply

 

It would be a lot

It might be possible, but you'd need a lot more circuitry ensure the battery was correctly charged according to its chemistry.

Thank you Alec. But you didn't really understand my need.

The AC on the Secondary isn't used to power any load. The circuit is to be connected to a battery cell. So I can have multiple cells in series, the circuits can then be connected in parallel on the transformer Secondary. Any higher voltage cell is gets it power fed back into the lower ones. Even if the batteries are been charged as a pack.

 

But you didn't really understand my need.

I'm sorry but I still don't. The arrangement you describe in post #3 seems quite different from the arrangement in post #1.
Please post a diagram/schematic which clearly sets out what you have in mind.

 

What an odd idea. I suppose it is possible by isolating the inverter circuit from the charger circuit via electronic switching, but one has to wonder why. A lot of trouble to share a transformer.

 

Any higher voltage cell is gets it power fed back into the lower ones. Even if the batteries are been charged as a pack.

That's know as "lossless cell balancing" isn't it? There are ICs that can do that for cells within a pack.

 

That's know as "lossless cell balancing" isn't it? There are ICs that can do that for cells within a pack.

That right Lan0, I don't know if "Lossless" is the rigth term for it... But its actually an "Active Balance" process.

The cells work in series as a battery and BMS manages it. But the circuit individually connects them in Parallel via the Transformer Secondary. Even when the battery is been charged via the BMS, the balance circuit works as it's only concerned with the equalization of the Voltage on the Secondary rail.

Can you please point to any circuit or ICs that can do this.

Thanks.

 

Now I am convinced none of us understands what he is asking for. What could this possibly mean:

So I can have multiple cells in series, the circuits can then be connected in parallel on the transformer Secondary.

No, you cannot have the cells in series on the primary and in parallel on the secondary. If that is what you mean.

 

Now I am convinced I dont understands what he is asking for.

Okay then!

I'll wait for someone who does.

 

That right Lan0, I don't know if "Lossless" is the rigth term for it... But its actually an "Active Balance" process.

The cells work in series as a battery and BMS manages it. But the circuit individually connects them in Parallel via the Transformer Secondary. Even when the battery is been charged via the BMS, the balance circuit works as it's only concerned with the equalization of the Voltage on the Secondary rail.

Can you please point to any circuit or ICs that can do this.

Thanks.

No, but Mr. Google can.
https://www.ti.com/sitesearch/en-us...l balancing&sort=relevancy&numberOfResults=25

 

Okay then!

I'll wait for someone who does.

You quoted my post, changing my words. That is very dishonest. Why did you do that?

 

Okay then!

I'll wait for someone who does.

how about a schematic / drawing of what you want
the old adage of a picture is worth 1000 words work here,

 

Good day,

Can Push-pull go Bi-directonal?

I need help with a circuit where I can switch Battery DC power into a transformer (Ferrite/Toroidal) Primary so that it gives higher/twice voltage on the Secondary (AC) and when a higher potential AC is fed to the Secondary, the power is reversed and the battery gets charged instead.

Thanks.

Hello,

I think a regular transistor H bridge will provide this function. Possibly with a push pull setup too. There would just be two other issues to think about and control.

During normal output voltage, the transistors will be supplying PWM to the primary.
During a higher secondary voltage period, the back EMF diodes across the transistors will allow full wave rectification back into the DC buss. Since the buss would be the battery, it would get charged. How much and at what rate would have to be controlled with a charging circuit. During this time the transistors would probably have to all be turned off.
This actually happens already with many transistor H bridge converters because the diodes sometimes conduct current around the transistors, and when that happens the energy is put back into the DC buss and stored in the input capacitors temporarily. That's a natural occurrence though as the transistors switch on and off so there is no need to purposely turn them off just for that. With the back fed power scheme, you most likely have to force them to turn off while the secondary feeds the primary which feeds the DC buss.
Also, sometimes some of the energy is forced back into the DC buss instead of dissipating it and this would be done with one or more diodes also.

 

how about a schematic / drawing of what you want
the old adage of a picture is worth 1000 words work here,

Here's a pictorial description of what I mean.

The circuit is a Bi-directonal synchronous setup. It is connected to individual cell A,B,C which are connected in series to power a load. The individual circuit switches each cell into the primary of a transformer, the secondary of the transformers are connected in Parallel.

As described in the picture, cell C with the highest voltage will definitely have the highest voltage on Secondary rail and because the switching is Bi-directonal, the lower voltage cells A and B gets charged from the power of Cell C.

I hope this explains it.

 

You quoted my post, changing my words. That is very dishonest. Why did you do that?

Sorry if you took it wrong but it's just me typing what I understand your reply to be.

I migth not have that big know with designing electronics from scratch but I think I know when something is possible. You continuously telling it's not possible just seems you don't understand what I need yet.

 

Your Block-Diagram/Picture is a good start on a full explanation,
but it does not contain enough information to understand EXACTLY what You are trying to do.

It is not a proper Circuit-Schematic which would show all of the details.

Input-Voltage, and the source of that Voltage,
Plus the expected Peak, and Average, Battery-Load-Current,
are also required specifications.

I think I know what You are thinking about,
but it is far more expensive, and bulky, to use Transformers,
but it may be slightly more Power-Efficient.

There are also no provisions shown for discharging the Cells down to a safe "Storage-Voltage",
but maybe your Battery will be in continuous use, so You don't need this important feature.
.
.
.

 

Sorry if you took it wrong but it's just me typing what I understand your reply to be.

I migth not have that big know with designing electronics from scratch but I think I know when something is possible. You continuously telling it's not possible just seems.

I did not take it wrong, YOU quoted it wrong. When you claim to be quoting someone, you MUST use their exact words, not your interpretation of them. That is what it means to quote. Do not do that again, it is basically lying about what someone said.

Now let’s look at your second paragraph. Where did I say something was not possible? You are again lying about what I have said.

 

Here's a pictorial description of what I mean.

The circuit is a Bi-directonal synchronous setup. It is connected to individual cell A,B,C which are connected in series to power a load. The individual circuit switches each cell into the primary of a transformer, the secondary of the transformers are connected in Parallel.

As described in the picture, cell C with the highest voltage will definitely have the highest voltage on Secondary rail and because the switching is Bi-directonal, the lower voltage cells A and B gets charged from the power of Cell C.

I hope this explains it.

Hi again,

Sorry, but i do not think you are describing this well enough. There does not seem to be anything that is "bidirectional".

The drawing shows C is charging A and B batteries, and that looks ok. The load is taken across A, B, and C, and that looks ok.
The question is, what charges C then?

Of course when I say one is charging the other, I presume that the charging regimen is appropriate for that battery chemistry. This is a very important aspect of the system.

 

Do not do that again.

Now let’s look at your second paragraph. Where did I say something was not possible? You are again lying about what I have said.

Sorry about that.

 

Hi again,

Sorry, but i do not think you are describing this well enough. There does not seem to be anything that is "bidirectional".

The drawing shows C is charging A and B batteries, and that looks ok. The load is taken across A, B, and C, and that looks ok.
The question is, what charges C then?

Of course when I say one is charging the other, I presume that the charging regimen is appropriate for that battery chemistry. This is a very important aspect of the system.

The battery(cells ABC) are charged through the BMS connected to them which have nothing to do with the circuit.

The circuit isn't controlled by anything, you connect to the cell and it does its thing irrespective of what cycle (charge/discharge) the cells are on.

The circuit only stops working when the cells gets to the minimum voltage that can power the switching IC used.