| 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! |
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