Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Q&A

Comments on Contactor control - Higher voltage PWM

Post

Contactor control - Higher voltage PWM

+2
−0

I have a battery pack that consists of 18650 battery cells(14 cells in series max.). Hence, the voltage of the battery pack will be between 35V and 60V(to be on the safe side)

I am designing a BMS in order to control it with cell monitoring, analog measurements, contactor control, etc. features built-in.

Using the battery HV pack voltage(35-60V), I would like to control a 12V/1.5A coil of a contactor. The reason for that being the fact that the rest of the circuitry could be powered with a 5V/500mA buck converter and not having a 12V/2A supply only for the sake of contactor control would be nice.

Would the following architecture for that purpose work in real life? Is there a better way of doing this? PWM Relay Picture


Here is how the circuit should work. Vpack_analog_input is fed into the micro analog input. The circuit around L1, C1, and D1 serves as a flipped buck converter having an NMOS instead of a PMOS. C2 is providing a low impedance for the switching node because I fear the ringing would cause a significant amount of emissions on the input cable.

The idea is to sense the Vpack and initially allow M2 to be opened for no more than t=L1*Icoil/Vpack , and after that apply PWM to Pwm_Control and limit the duty cycle in order to never have more than a certain threshold of current flowing through L1(to be done through experimenting).

History
Why does this post require moderator attention?
You might want to add some details to your flag.
Why should this post be closed?

1 comment thread

General comments (2 comments)
General comments
coquelicot‭ wrote almost 3 years ago

I'm not sure I understand why you are trying to do. Is the problem the following? : the contactor needs 12 V, 1.5A to switch, but after it has switched, it needs much less current because of hysteresis. So you are trying to design a power saving circuit, using the coil of the contactor as part of a 5V buck convertor, right?

2kind‭ wrote almost 3 years ago

I have a voltage source(35-60V range) and want to control the 12V/1.5A coil of the contactor without designing the 12V/2A buck solely for the purpose of contactor control. Moreover, 1.5A is enough for activating the relay, but I assume the holding current to be in the 300-500mA range.

Skipping 1 deleted comment.