pwm period synchronization

[htdev]

is it possible to synchronize fp pwm period with an external signal? (I use a a FP-PWM-520)
I would like to start pulses at zero voltage of a current phase.

[steven@ni]

You could do this programmatically.

For example, if you are using an FP-2000, you could embed code to monitor the external signal.

When the external signal drops to 0, you can then write to the FP-PWM-520 to alter the duty cycle and period.

[Aaron_G]

There are different ways that this may be accomplished, but they will be limited in their accuracy. You can programmatically monitor the phase and write a duty cycle to the PWM module (the channel should be at zero duty-cycle before hand). The FP-PWM-520 will then start pulsing on that channel as soon as it has a non-zero duty cycle. This will be limited by the network latency (software latency only in a FP-20XX module running embedded code), and the latency of the FieldPoint inter-module communication bus. The best case with current software on a FP-20XX module would result in a 1 - 2 ms delay at a mininum.

Alternatively, depending upon what sort of pulsing that you are using the FP-PWM-520 for, it may be possible to use a FP-CTR-50X module instead. Look
at the FP-CTR-500 or FP-CTR-502 Operating Instructions for Application Notes on using the Counter modules for pulse generation. You can set the counter module to pulse only when the current phase is low, and since that will be entirely in hardware, the synchronicity will be greater (should be less than 1 ms).

Regards,
Aaron