buck converter with peak current control

- M
- mtourloukis
  
  Contact options for registered users
posted
16 years ago

Wed, Jan 16, 2008 11:14 AM

hi all!

i m building a buck converter with peak current control... so...from a sensing resistor that pass my output current and after a small circuit i get a voltage that has the shape of the current (triangle) and amplitude between 5 and 8 volt... the next step is to add a compensation ramp to this voltage...i made another circuit that produces this sawtooth wave and i have to add it... then the next step is to get an error amplifier and at the input to put a reference for my output voltage (from a zener) and my output voltage after a voltage divider...at the same level of 5 to 8 volts ...and the output of the error amplifier i have to take it to the one input of a comparator, and to the other input of the comparator i have to put the other voltage with the compensation ramp added...

this is how it should be done...but i dont know how... i mean...i dont know how to setup the error amplifier and how i can add the sawtooth to the voltage that is my "current image"...

if you could give me an example to simulate in spice it would be great!

- M
- MooseFET
  
  Contact options for registered users
Vote on answer
posted
16 years ago

Wed, Jan 16, 2008 2:11 PM

ASCII ART:

Input1 ----/\\/\\----- ! Input2 ----/\\/\\-----+----! \\ Comparitor ! >

Input3 ------------------! /

The resistors combine the two signals before comparing. Usually the current sense ramp is combined with the slope compensation ramp and then compared to the error amplifier output.

There is no reason, if the slope is downwards, not to combine this with the error amplifier signal before comparison.

- M
- moutou
  
  Contact options for registered users
Vote on answer
posted
16 years ago

Wed, Jan 16, 2008 7:45 PM

if i understood what you said...there is not difference if you put the sawtooth to the output of the e/a or with the current sense triangle... and how can i have the sawtooth downwards? i cannot simulate now...but with another amplifier by putting the + input with the ground and the - input with the sawtooth will i get the sawtooth going downwards?