High efficiency 3.3V buck converter 200mA

Thread Starter

BrMisha

Joined Aug 13, 2022
32
Hello!
I'm developing BMS 30S based on stm32L with CAN interface. It uses 10mA in an run mode (95% time) and sometimes up to 100 mA.
Which is buck converter better to use in my case for the most efficiency?
Thanks)))
 

Papabravo

Joined Feb 24, 2006
21,225
Hello!
I'm developing BMS 30S based on stm32L with CAN interface. It uses 10mA in an run mode (95% time) and sometimes up to 100 mA.
Which is buck converter better to use in my case for the most efficiency?
Thanks)))
Your question is incomplete. We need to know what input voltage you are working with and your goal for efficiency. When it comes to efficiency, this will be a tradeoff between efficiency and cost. Once you go above 90% each incremental improvement requires a disproportionate increase in expense. You also did not indicate if this will be a purchased item or one that you design and construct.
 

Thread Starter

BrMisha

Joined Aug 13, 2022
32
30S and every cell up to 4.2V.
So i can use 3S, 4S, 5S and more.
About price. Of course i would like to use cheap solution, but with efficiency 90%+
 

Ian0

Joined Aug 7, 2020
9,810
90% efficiency at 10mA is going to be challenging. If your control circuit takes 1mA you have already missed the target, even before you start thinking about switching and conduction losses.
 

ronsimpson

Joined Oct 7, 2019
3,037
MIC23050, or MIC230501 or MIC2285
RP509Z222 There are a series of these. Also RP504Z.....
In this market it is very important to get the parts before you make a PCB. Most of the parts are not in stock. These I can get today.
 

Thread Starter

BrMisha

Joined Aug 13, 2022
32
MIC23050 and the MIC2285 has input voltage 2.7V...5.5V. But min voltage of discharged battery is 2.5. And would not like to use one cell
 

Papabravo

Joined Feb 24, 2006
21,225
MIC23050 and the MIC2285 has input voltage 2.7V...5.5V. But min voltage of discharged battery is 2.5. And would not like to use one cell
Given that you have multiple battery configurations, and various states of discharge on the cells. You want a DC-DC converter that will output 3.3V if the input is between 2.5V and 21V (5 x 4.2), is that correct?

With that kind of input range, a plain vanilla buck converter will not do the job. You may need to look into a SEPIC (Single Ended Primary Inductor Converter)
 

Thread Starter

BrMisha

Joined Aug 13, 2022
32
Given that you have multiple battery configurations, and various states of discharge on the cells. You want a DC-DC converter that will output 3.3V if the input is between 2.5V and 21V (5 x 4.2), is that correct?
2.5×5=12.5V to 4.2×5=21V.
But i can use any cell count from 3 to 30
 

Papabravo

Joined Feb 24, 2006
21,225
The LM2596 has less of 75% efficiency))
And i need chip, not module
On what basis do you make this claim? Is it your position that the chip (LM2596) cannot be used in a converter with greater than 75% efficiency? I think it has more to do with the other components than the chip itself.
 

Ian0

Joined Aug 7, 2020
9,810
BMS has ballasing.
I would like to use 30S but it is to much for converter
Doesn't that mean that it partially discharges some cells whilst it is waiting for the others to get fully charged? Won't it extend the charge time?
Any "ballasting" would reduce the efficiency of the charger.
I've recently used this one:
https://www.analog.com/en/products/ltc3639.html#product-overview
which will work up to 150V and has 12uA quiescent current.
 
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