Electronics > Beginners
controlling Buck module from mcu
hsn93:
Hello,
i want to fast design a product that has buck converter i want to control from arduino
so what I've chosen
300W buck converter module
https://www.aliexpress.com/item/300W-20A-DC-DC-Buck-Converter-Step-down-Module-Constant-Current-LED-Driver-Power-Step-Down/32821840536.html
its based on LM25116
anyway, there is CV which is variable resistor that goes to the buck controller and i wanted to control it so this is what i though of:
to use:
MCP4725 I2C DAC Breakout module development board
https://www.aliexpress.com/item/MCP4725-I2C-DAC-Breakout-module-development-board/32821744967.html
and
npn transistor MMBTA42LT1G
https://www.onsemi.com/pub/Collateral/MMBTA42LT1-D.PDF
the plan is to connect npn transistor like this:
Note: R1 is inside the buck module so i will make jumper wire.
do you think this is good idea? will it work effectively? accurate (+/- 50mV)?
any other ideas?
i've seen this also which seems good it has 64 values need accuracy right?
https://www.analog.com/media/en/technical-documentation/data-sheets/AD5171.pdf
mikerj:
No, this will not work. I'm assuming terminal 2 of R1 provides feedback to the switchmode regulator device?
You DAC output will do nothing until the voltage is high enough to start turning on the transistor, so maybe 0.0-0.55v does nothing. Then there will be a small voltage range over which the transistor switches on and saturates maybe 0.55-0.7v and then any further voltage will make no difference. This means you have a tiny range of your DAC output that will do anything, when when operating in this range it will be very temperature sensitive, so will drift.
What is the reference voltage of the switchmode device, and what is the reference voltage of your DAC? Typically you would wire this so the DAC sinks or sources current into the feedback node (terminal 2 of R1) which may be as simple as a resistor between the DAC and R1, but you need to calculate this this.
perieanuo:
Hi,
Just like this no.
First you need a precise mechanism to start the dcdc module with zero output or disabled.this means controlling enable pin of dcdc converter if he has one.
Then put your reference made with the DAC on dcdc reference module, wait some ms then enable the dcdc.
Any other way is risky and amateur-like.
Best regards,Pierre
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ogden:
--- Quote from: mikerj on December 10, 2018, 10:05:52 am ---No, this will not work.
--- End quote ---
It won't work indeed. DAC you mention is buffered meaning you may build control circuit like this:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/818
perieanuo:
--- Quote from: ogden on December 10, 2018, 11:00:05 am ---
--- Quote from: mikerj on December 10, 2018, 10:05:52 am ---No, this will not work.
--- End quote ---
It won't work indeed. DAC you mention is buffered meaning you may build control circuit like this:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/818
--- End quote ---
Yep, this can do.
Envoyé de mon iPad en utilisant Tapatalk
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