11-19-2013 12:45 PM
Hello Everybody!
I am using a cRIO-9012 with NI-9401Digital I/O module for PWM signal generation with variable Frequency,Duty Cycle and Dead-Time. I am able to vary the duty cycle and frequency with this first VI(PWM_VI.png) but i could not generate the variable dead-time, can anybody help me in this regard, i thank in advance.
I tried with another VI(with_dead_time.png) it is possible to change dead time but there i cannot change the duty cycle in percentage and so accurate. So any help in this regard is in advance appreciated. i attach both VI's.
With Best Regards,
azy
11-20-2013 03:36 AM
Hallo,
Here are the relevant VI's of the above project.
Please help me in this regard, thanx in advance.
Best Regards,
azy
11-20-2013 09:50 AM
Hi,
I dont know what you mean with dead time. But I have found this instruction how to implement a PWM on a FPGA. If this dont helps, please give me an explenation about your dead time.
Developing a PWM Interface using LabView FPGA
http://www.ni.com/white-paper/3254/en/
Kind Regards
Jerry
11-20-2013 10:14 AM
Hallo Jerry,
Thanks very much for your reply, here i am attaching a picture of a high and low side switch waveform of a synchronous dc-dc converter, the dead time means that there is a user controlled delay between the high and low side switch so that both switches cannot turn on at the same time and so we do not have a short circuit situation. The high and low side switching waveforms are exactly 180 degrees out of phase if you run the VI(PWM-VI) you will se there is no dead time between high and low switching so i can have a dangerous short-ckt situation.
Here is the picture you will understand. Thanx in advance..
With Best Regards,
azy
11-21-2013 03:49 AM
Hallo Jerry,
I attached the relevant png's of the dead time , did you see it?
Best Regards,
azy
12-03-2013 07:02 AM
Hi!
Could you fix the problem by the time?
King Regards
Jerry
12-03-2013 08:36 AM
Hallo Jerry,
I could not understand, what do you mean fix by the time? Could you explain please?
Regards.
azy
12-03-2013 08:40 AM
Hi embedded,
Jerry was asking if you still need help. "problem fixed by time" means: your last post is now two weeks ago, so there probably is some advance on your side?
Btw. some pseudocode may help:
pwm loop set DO1 true wait DO1-High-Time set DO1 false wait deadtime set DO2 true wait DO2-High-Time set DO2 false wait deadtime next iteration
12-03-2013 08:58 AM
Hallo GerdW,
Thanx for reply, with VI(PWM_new_22_10_2013) i am able to do this but wit the other VI(PWM_high_low_pulse_control_1_deadtime_test) i cannot do the same because it uses the shift register for generating hig-low signal, the other one generates frequency with True and False constants, i want to do it with the VI with shift registers.
Best Regards,
azy
12-18-2013 04:27 AM
Hello GerdW,
Did you check the other VI?
Best Regards,
azy