PWM, H-Bridge and NCO - PIC16F18446

[HenrikOlsson]

Sorry, mode 2 still isn't clear to me.... "2. Bipolar voltage on the load with a rate of 0-50 Hz"
Do you mean...

A) That polarity of the voltage across to the load is switched at 0-50Hz (and power is regulated by the dutycycle of the 1kHz PWM signal) or
B) That polarity of the voltage across to the load is switched at 1kHz (the PWM frequency) and the 1kHz carrier is turned on/off at a rate of 0-50Hz or
C) None of the above meaning I still don't get it :-)

[richard]

Do not know if or how NCO can be steered PWM/CWG module.


Richard, also nice idea about CLC module. I suppose the low freq signal is external of the PIC. Or may be the NCO signal too.

you need to have a good look at the data sheet
valid cwg input's :-
the nco
a clc output
any of the ccp /pwm modules
the dsm output

valid clc input's:-
the nco
any of the ccp /pwm modules
the dsm output

there are many possible methods of modulating a LF osc source with a HF pwm signal with the clc or dsm modules
any of which can be turned into a full bridge signal source with the cwg module , try a few

[Ioannis]

Hope this draw clarifies a bit the problem.

Ioannis

[richard]

so where does the 1khz fit in ?


i expected more like this

[Ioannis]

You are right, I just didn't want to clutter the draw.

Ioannis

[amgen]

looking at your diagrams, seems like you could ..... set up the PWM module for 1KHZ as normal, for the 20HZ part, set up a timer interrupt for the low freq maybe with a couple of roll overs for lower freq.... then on tmr int, only need to switch the Q's and add a little dead time on each switchover.

[Ioannis]

Alain:
The PWM is controlled by a Pot. I could also make a variable power supply and control directly the voltage on a SMPS circuit instead of PWM. More complicated.

Amgen:
It is easier on the unipolar mode. But gets difficult on bipolar drive having software to control both PWM, low freq signal and the control of the 4 MosFets transitors. Including deadtime.
Better, most if not all of this be done on hardware using NCO, CWG, CLC etc.

I believe that it is possible to do this as Richard is confident too. I just need more reading to understand how all these modules will work together.

Ioannis