Figure 43.
PFC tuning: determining TSW limits
Finally, the GUI computes the PFC parameters.
Figure 44.
PFC tuning: PFC min./max. pin and DCM power
11.4.6
Step 4: skipping area threshold
The forth step consists in setting the skipping area power threshold (below this threshold, the system will apply
power skipping, i.e. shutdown PFC operation before/after the peak of AC cycle, like PWM).
This improves the overall efficiency but obviously degrades the THD/PF figures: for this reason, it has to be
performed at low power.
The threshold is up to the customer.
To determine the skipping area threshold, the GUI:
•
enables PFC mode change (both PFC frequency and estimated power-based)
•
sets the DC load to match the desired power
•
measures the estimated power at various AC voltages
The threshold is the average of the measured values.
UM2342
Step by step calibration example
UM2342
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Rev 1
page 37/57
