Controlling DC/DC from microcontroller

[mare69]

Is is a good idea to put microcontroller in the DC/DC feedback ?

I was thinking to play with one small cortex M0 with ADC, PWM timer and DAC adjustable voltage comparator. The freescale kinetis "E" series (5V tolerant cortex M0, 12bit ADC) in easy solderable SO package is best fit.

What I would like to gain with such approach is flexibile and cheap programmable DC/DC, either boost or buck (not both at the same time) for supplying smaller loads with possibility to play with feedback regulation within software. Typically a load would be some small circuit or LED, supplied from single Li-xx cell.

Has anyone done such (hopefully not stupid) thing? Any thoughts / suggestion?

Thanks!

M.

[robotai]

It should be workable to use MCU to drive DC/DC circuit. However, I think pure DC/DC controller chip should be much cheaper and easy to use.

Here is a reference on Microchip website similar to what you want.
http://ww1.microchip.com/downloads/en/AppNotes/00216a.pdf

[bigtoy]

Yes, you absolutely can do this. This is exactly how bigger DC-DC converters are commonly made these days. (By bigger I mean multi-kW.) Writing the s/w is not trivial, in that it's important to loop as quickly as possible - this determines your response time to changes in the line or load. If your goal is to become a power electronics engineer, this would be an excellent starting / learning point.

[Gallymimu]

Microchip 16F1xxx are designed to do this.  They have core independent peripherals which will run a SMPS control without any software.  (PWM, Comparator to gate the falling edge, opamp for current sense).  It's really cool and easy.  Pulse by pulse current mode control with almost no effort.

[StackPointer]

From atmel side you can use At90 PWM series and few other MCUs from mega and tiny family, and of course ATXMega series. Few years ago I successfully built low power buck DC-DC converter based MPPT solar charger using Attiny861 (with 4.8W solar panel). It is decent low power chip that has advanced 8/10bit timer1 with three independent PWM outputs each with complementary output and common dead time generator. Timer can be run from 64MHz PLL which can provide 1MHz PWM with 6bit resolution down to 62.5KHz PWM with full 10bit resolution. MCU monitored input and output current and voltage, and run incremental conductance algorithm for MPPT and PID algorithm for regulating battery charging voltage.