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XMC™ Forum Discussions

User13217
Level 1
Level 1
We are experimenting with the QR Buck LED Driver XMC14 demo (VD_QR_BUCK_LED_DRIVER_01). The demo does not appear to enter into quasi-resonant switching as designed.

Checking the hardware connections it appears that there is a good signal at the ZCD pin. However, it does not appear to trigger next switching cycle.

Instead the switching cycle is triggered by timeout of maximum off-time.

Can anyone from Infineon comment on this issue? Is the QR Buck LED Driver Example code fully functional?
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User13217
Level 1
Level 1
Answering my own question, it appears that there is an error in the schematic and BOM.

After changing the 56 nF capacitors C39 and C42 to 10 pF the circuit performs as expected. Maybe 56 pF would also work.
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