Author Topic: Looking for Buck regulator IC digital controlled Vout  (Read 946 times)

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Offline SowlakiTopic starter

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Looking for Buck regulator IC digital controlled Vout
« on: August 05, 2019, 05:46:07 am »
Hello fellow EEvbloggers,

I am building a USB PD 2.0 compliant PSU (Source) and need a buck regulator that can output voltages in the range 20V - 5V with a current of 5A at full load. However I am unsure how to control the output of the regulator since many of these buck ICs tend to be feedback controlled with a voltage divider network pulled by the Voutput of the regulator. Do you know any ICs with PWM control or I2C for example. The design will include a STM32 Cortex M0 for USB PD transactions.

Thanks for any replys.
 

Offline dazz1

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Re: Looking for Buck regulator IC digital controlled Vout
« Reply #1 on: August 05, 2019, 08:01:32 am »
Hi
If you cant find a programmable device, you could put a DAC in the feedback loop.  Instead of using a Vref voltage, you use the feedback output of the converter.  The DAC then acts like a digital controlled potentiometer.    You could also try digitally controlled potentiometer devices, often used in audio equipment.

Dazz
Dazz

Over Engineering: Why make something simple when you can make it really complicated AND get it to work?
 

Offline ledtester

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Re: Looking for Buck regulator IC digital controlled Vout
« Reply #2 on: August 05, 2019, 08:21:58 am »
Here's a Maxim app note describing how to inject current into the controller's feedback input using a DAC:

https://www.maximintegrated.com/en/app-notes/index.mvp/id/5058
 

Online voltsandjolts

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Offline ledtester

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Re: Looking for Buck regulator IC digital controlled Vout
« Reply #4 on: August 05, 2019, 09:11:12 am »
An interesting project which modifies cheap LM2596 modules into programmable power supplies:

https://github.com/TG9541/stm8ef/wiki/Board-CN2596
 

Offline SowlakiTopic starter

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Re: Looking for Buck regulator IC digital controlled Vout
« Reply #5 on: August 05, 2019, 09:25:21 am »
Hi
If you cant find a programmable device, you could put a DAC in the feedback loop.  Instead of using a Vref voltage, you use the feedback output of the converter.  The DAC then acts like a digital controlled potentiometer.    You could also try digitally controlled potentiometer devices, often used in audio equipment.

Dazz

Yeah I was thinking about that, like manipulating the FB pin and have a separate voltage divider from Vout connected to an ADC on the MCU to make sure the voltage is correct. The digital pot seems like a very good choice too.

Edit: I use Farne11 as my supplier and have to buy from their somewhat limited supply of PMIC. I figure I will go with a integrated MOSFET buck regulator that can output 20V/5A, like 3£ but seems like a reasonable price for what I get.
« Last Edit: August 05, 2019, 09:31:50 am by Sowlaki »
 


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