LinkSwitch-PL question
Hi,
With reference to the LinkSwitch-PL datasheet, I am still unable to understand the relation between the FB voltage and Phase angle. Besides that, what determines the thresholds (phi OS) and (phi OL)? A further explanation on the feedback voltage vs phase angle dimming characteristics is much appreciated.
Thank you.
Comments
Hi Cochrane,
Thank you for you explanation above.
However, I would like to clarify another point. Does the statement "The FEEDBACK pin voltage adjustment is initiated at approximately 20% of the main half-cycle duration." in page 4 of the datasheet refers to the feedback pin being adjustable after the phi OS threshold which is about 45 degrees?
By the way, I have another question regarding the cycle skipping mode operation of the LinkSwitch PL. What does it mean by "skipping cycles"? How is the feedback pin cycle skipping threshold being reduced to limit the output delivery? I hope you can further elaborate on what happen exactly when cycle skipping mode is triggered.
Thank you.
Yes, the two statements refer to the same point. I estimated the 20% as approximately 45 degrees (actually works out to 36 degrees).
If the feedback pin voltage exceeds the "Cycle Skipping" threshold, the device will stop switching.
Z. Cochrane
phi OS threshold is approximately 45 degrees and phi OL is approximately 135 degrees where 0 degrees is full half sine wave conduction and 180 degrees is no conduction. The Feedback Threshold is typically 290 mV from 0 to 45 degrees. The threshold is linearly reduced to (290/4)mV at 135 degrees. After 135 degrees the threshold remains at 290/4 mV and the feedback goes open loop (the on time and frequency remains constant).
Z. Cochrane