How are waveforms during TLD5542-1QV fast discharge phase?
The TLD5542-1QV has a fast discharge feature that allows to quickly discharge the output capacitor. During a fast discharge phase the ouput capacitor is getting discharged to the input capacitor and therefore causing a small reverse input current.
The figure below shows the switching pattern and waveforms during this fast discharge phase.
Read more on fast discharge in the datasheet https://www.infineon.com/dgdl/Infineon-TLD5542-1QV-DataSheet-v01_10-EN.pdf?fileId=5546d4626fc1ce0b01... on pages 27 and 28.