Hello,
I have just started with programming on micro controller . I am working on variable frequency drives . I need to implement SVPWM on TMS570 LS3137. I am having some basic questions as follows
Problems:
1. How to create center aligned PWM?
2. Out of 6 PWM signals - 3 non inverted center aligned PWM + 3 inverted PWM , how to implement inverted PWM with respect to non inverted in case of center aligned?
3. How to define variable duty cycle ?
Thank you in advance.
Regards ,
Suyog
Hello Charles ,
I am having few doubts as follows :
1. Why havn't you used only XOR logic for symmetrical PWM (explained in attachment ) ? Is it necessary to set up with up-down counter ?
2. Suppose, we make XOR logic on 2 pins. What is the expected output waveform - edge aligned / center aligned ?
Regards,
Suyog
What do you meant I 'have not' use the XOR logic? If you look at the comment in the file it says " The output of the two pins are XORed together will produce a symmetrical PWM. In order to use XOR feature, the two pins to be selected must be an even/odd pair adjacent to each other."
The NHET natively can not produce symmetrical PWM because it does not implement a up/down counter. Instead the counter is only a up counter resulting an asymmetrical PWM. In order to produce a symmetrical PWM, you generate two asymmetrical PWM signals and XOR them together.
Below is an illustration of symmetrical PWM generation using XOR feature base on an earlier generation of the HET in the R1x family of MCUs. The concept is similar for the NHET implemented in the LS3137.
