Electronics > Projects, Designs, and Technical Stuff
Lithium Cell Charger / Discharger Half-Bridge PWM current control
(1/1)
gnasirator:
Hi there,
I am currently tinkering with an idea of mine: I would like to build a small pcb that allows MCU controller charge&discharge of a single lithium cell to do capacity and impedance testing.

And I am currently looking into the powerstage design. Requirements are 10A charge and 10A regenerative discharge back into the main power rail. My approach is as follows:

Source

I want to use a current-mode PWM controller and feed a setpoint voltage into the current limit pin to have freely adjustable constant-current charge/discharge mode. I haven't found a controller IC to do that yet, I might have to build that part from discrete components.

The topology in the end would be something along those lines (half bridge to allow buck charge / boost discharge operation):

The voltage control loop for CV operation would run on the MCU and control the current setpoint voltage.
As you can see, this is still in very early draft stage. I first want to get the basic topology right. Of course the shown circuits don't fully work yet ... but I think the principle should be usable.

A first rough test circuit already seems to work:



So the task now is to get a PWM controller IC that gives me the current control parts (opamps + flipflop) in silicon and allows bidirectional control of the half bridge. Can anybody recommend a PWM IC that can do this? Or would I really have to build this discretely?

Maybe hijacking a Buck/Boost PWM controller IC's FB pin is possible, like here:
http://www.ti.com/lit/an/snva829/snva829.pdf
But I haven't completely figured out how to do that for buck and boost mode and I don't want to reinvent the wheel. I'm sure there are plenty of chips out there doing this? I would assume e.g. they are also used in motor inverters? I simply don't know them yet.

I hope this comes across understandably :)
Thanks for your input!

Cheers
Valentin
jbb:
Maybe the ADP1974 would be helpful?  It's designed for this role and includes precession V, I sense amplifiers, CC / CV control and a PWM block. 

While it's probably a bit more expensive than a pile of discrete components, remember that your time has value.
gnasirator:
Awesome! Exactly what I was hoping for.
I will build the first sample following the typical application and once it's all up and running think about replacing the AD8451 with discrete components.

Thanks heaps!
Navigation
Message Index
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod