Which pin is which?

Go To Last Post
6 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I tested this example - "Buck Converter Controller - Closed Loop Voltage Control" of Microchip Studio on AVR128DB48 Curiosity Nano, it was said in "main.c":

 

/*                 External connections                        */
/*                      PD5 -> PD2                                */
/*               Triangle Wave -> PD0                        */
/*                 Feedback -> PD7                            */
/*           ErrorAmp out -> PD5                            */
/*                      Switch -> PA7                            */

 

and I found this photo for buck convertor:

my question is: I know "Switch" connect to gate of the FET, "Feedback" to the Positive of LOAD,  how about "ErrorAmp out" and "Triangle Wave"? Should I input "Triangle Wave" from a Signal Generator? If so, what's its function, for compare?

This topic has a solution.
Last Edited: Mon. Apr 19, 2021 - 02:00 AM
This reply has been marked as the solution. 
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

MianQi wrote:
Should I input "Triangle Wave" from a Signal Generator?
No

MianQi wrote:
If so, what's its function, for compare?
Yes

Closed Loop Voltage Control using Core Independent Peripherals | Buck Converter Design and Feedback Controller Using Core Independent Peripherals

[bottom]

Figure 3. Error Amplifier Compensation Network and Ramp Generator

 

"Dare to be naïve." - Buckminster Fuller

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You need a way to drive the fet gate, often a pulldown transistor & pullup resistor (for P-fet)

 

Say Vin is 12V, and you use a P-Fet, then when the fet is off Vgate will be 12V & when the fet is on Vgate will be less than , say 7V (for a 5V gate drive).

 

If using an N-fet, you have a harder time, since the gate voltage needs to go above Vin...so for 12V Vin, the gate will be at 12V when  N-fet is off  and, say, 17V when N-fet is on (for a 5V gate drive).

Since you don't have 17V to apply to the fet gate, you have to create it using a charge pump, or other means (such as booster chip).  You can make a cheapo charge pump using an io pin & some diodes (doubler).

 

To adjust the Vout, you "simply" vary the duty cycle of your PWM applied to the fet gate.  A 50% duty will reduce the output close to 50% of Vin (12Vin ---> 6Vout) , 20% will reduce the output to 20% of Vin (12Vin ---> 2.4Vout), etc.  In order to account for losses & transients, you can make the PWM control fancier, but it is enough to start & hook up your multimeter to see variable output levels.

Switchers work by these golden rules (here is a $1000 seminar in 2 sentences):

  The avg ideal inductor voltage is always zero

  The avg ideal capacitor current is always zero

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Mon. Apr 19, 2021 - 01:10 AM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 1

Thanks, valuable suggestions.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

The way to learn about buck DC converters is NOT to build one yourself because the voltages on the prototype can be dangerous- or- your equipment will probably not be good enough to get an accurate reading -or- you may not be skilled enough in electronics to understand the readings that your equipment is giving you.

 

Instead spend about $10 and buy several different types of buck DC converter module boards on eBay.  Download the data sheets for the various driver ICs and then view the oscilloscope waveforms present on various points of each of the module boards under different loads and test conditions.  Review between the datasheets, the tutorials on youtube about switching power supplies, and your measured results on the module boards until you understand what is going on and why.

 

Then you should start designing your own switching power supply circuits.   Here are some examples from eBay:

MP2307 module board: https://www.ebay.com/itm/2pcs-Mi...
MP2307 datasheet:   https://cdn-shop.adafruit.com/da...

LM2596 module board: https://www.ebay.com/itm/Buck-St...
LM2596 datasheet:https://www.ti.com/lit/ds/symlin...

 

Last Edited: Mon. Apr 19, 2021 - 03:39 PM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

" Download the data sheets for the various driver ICs and then view the oscilloscope waveforms present on various points of each of the module boards under different loads and test conditions.  Review between the datasheets, the tutorials on youtube about switching power supplies, and your measured results on the module boards until you understand what is going on and why. "

 

yes