Phase Shifting of Pwm signal for driving IGBT Gate's

[Karrar Hussain]

For driving the Gate's of the IGBT's ,the pwm signals are generated but 120 degrees phase shifted from Each other .
How can i implement this phase shifter in Avr Microcontroller .
Any suggestion or hint ?

 

[kappa_am]

you want to shift saw-tooth waves?
use a look-up table refer to it using timer interrupt. for other waves with 120 degrees disposition just add a number to reference location.
for example suppose your look-up table has 360 position (stored value)
first interrupt=1 lookup[1]
for other wave just add it by 120 and lookup[121]

good luck

 

[Karrar Hussain]

The gates of six transistor inverters are driven by pwm signal ,which is generated by Microcontroller .Those pwm signals are given to inverters gates through Gate drivers .The problem in three phase inverter is that it needs to switch on or off the switches about 120 degrees apart from each other . So i need to shift the pwm signal not the sawtooth .
Look up table idea is a good one but what should be the contents of my look-up table ?

 

[kappa_am]

I thought you are working on Phase shifting PWM of a multilevel inverter.
for a regular PWM control of graetz bridge:
first generate a saw-tooth wave form use a time you do not need look-up table for this. the half value of your timer will be amplitude of your saw-tooth. it mean you have shift your saw-tooth by a dc offset , since you cannot have negative values by timer.
use a look-up table for a sine-wave. store a sine wave values in a look up table. you can use matlab to generate these values. for example every 1 degree.so you have 360 point. use the method I said in afore-posted reply.
comparison of three sine-wave you obtained with saw-tooth can generate pulses you need to control 3 legs of you inverter.

 

[Karrar Hussain]

Can i generate these control signals ,by using the Pwm module of microcontroller without that procedure you said ? If yes ,then how ?
And
Can microcontroller produce sawtooth wave without look up table ??