- For official reference, please read Nyquist rate.
- The relationship between the controller and the sample time is:
Sample Time <= Fastest Settling Time / Minimum Number of Sample - Recommended minimum number of sample is 30. Higher is better.
- Fastest settling time is obtained when the voltage or current used in the controller feedback is within 2% of its final value.
- Example: A buck converter using a PI controller have the fastest settling time of the output voltage around 3 ms. Therefore, the maximum sample time is:
= 30 ms / 30 samples = 100 us
dSPACE sample time for this controller is 25 µs, which is below 100 µs.
Therefore, this controller can be used. - Here what happen to if the sample time is too close to the settling time. The controller produces unstable output, resulting unstable output of the power converter.
