RE: TOP249YN switching issue
Hello sir,
Currently I am using Top249yN in my design to have a various out out of 20v, 15v, -15v and 5v respectively. But the problem I am facing right now is that whenever I am switching ON the power supply it gets burn out the TOP SWITCH.
I am attaching my design lay out with this mail.
Would you mind providing me the more detail regarding the transformer design please. As of now these are the primary and secondary voltage in my circuit.
P1-110v S(12-11) - 20v
S(9-8-10) - +15v and -15v
S(6-7) - 5v
S(4-5) - 15v (This is the more confusing part to me bcz the control switch is driven by the MOC8102 optocoupler)
S(14-15) - 5v
Please have a look on my design and rectify it if needed. Waiting for yours positive reponse.
Files
| Attachment | Size |
|---|---|
| Custom DCDC.pdf | 31.85 KB |
Comments
Hi
Dear PI-LeoDavinci, unfortunately there is no way to verify anything unless the TOP249 starts working.
I think according to data-sheet and application notes there should be blocking zener diode in parallel with RC clamp circuit. I always prefer to use blocking diode even when there is RC clamp.
best regards,
Hi Allahyar,
If that is the case, you can try using zener diode with proper voltage rating. Based on the observation, it seems that the problem is actually on the snubber. If properly designed, it should not impose any problem on the TOP249. One way to verify this is to actually check the drain voltage if it is being exceeded during startup. The way I understand that there is no way to verify is only during the normal operating condition. However, during the failure condition we can still check if the drain voltage is exceeded according to specification. We can only suspect as of now that the snubber is the problem but we need to verify accordingly. If by adding the zener diode, the unit actually worked, then kindly check the drain voltage immediately.
Hi,
Thank you for using TOP249YN. Looking at the schematic it seems everything is in place. To be able to debug the issue we suggest the following:
1. Verify/check the maximum drain voltage especially during turn on condition.
2. Verify/check the drain current especially during turn on condition.
3. Confirm properly if the transformer winding construction is correct.
When verifying the drain voltage and current, first check it at no load condition then if it turns on properly you can slowly increment the load. This is to anticipate if the drain peak voltage has something to do with the load condition. If even at no load, the failure is still being encountered, kindly check transformer construction. Make sure that no the winding polarities are correct. Let us know what are the results and hope this helps.