Input Circuit creates overshoot
When building a switched mode power supply based on a LNK623 we used the input circuit from your application EPR-85. While testing the prototype the chip was blown after several power on/offs.
Doing some investigations on the reason I figured out that using an inductance in series with the capacitor can lead to high voltages when the circuit is connected to power due to resonance effects. The series resistor should not fall below a specific value (aperiodic case).
How is it possible, that the LNK564 can handle this?
Please also see simulation in attached file.
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Since the schematic simulation seems to produce instabilites when simulating the diode I did a math simulation that shows the exact situation. The highest voltage is about 460V which is really a lot.
| 첨부 파일 | 파일 크기 |
|---|---|
| Math Simulation (108.41 KB) | 108.41 KB |
Hi Peterpan314,
Thank you for your interest in using our LinkSwitch ICs.
May ask what is your input votage and can you share with me your complete schematic? At startup using the LNK564 what is the voltage across the Vds of the primary switch? This should be less than 700V. If less than 700V then the IC should not get damaged. If you remove the series inductor what then will be the max votage at startup in your simulation?
Regards,
PI-Picard
Any ideas?