smps using TOP 224y switch
Dear Sir,
Ive designed an smps with TOP224YN ckt. Pri. snubber is capacitor of 4.7nf and r=6.8ohms. Top was blowing off, i had 4007 diode in bias circuit. i replaced it with in4148. now th etop does not blow but it does not start either. voltage at the control pin is high. transformer primary inductance is 730uh.
kindly advice.
Seema Mahbubani
KEJE ELECTRIC CO.,
Comments
Thank you so much for your reply. Am attaching a schematic. Input of 300V dc. Can i test the ckt at 32 Vdc to check the operation of the circuit. What are the test points?
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| schematic_for_PI.png (10.18 KB) | 10.18 KB |
Dear Sir,
I applied 48 Vdc. voltage across drain and source is 48V and voltage across control and source terminal is 0.
So, what is the problem. What should i check next?
Regards,
Hi Kejearc,
Where did you get the schematic? It is not a conventional way to control your flyback circuit.
Here are my few observations.
1.We have previously discussed the value of the snubber.
Have you already changed the values? The values are not that clear.
2.Feedback. It is not also clear on what you are using on ZD4 and R44 and what voltage you are trying to regulate.
3. Control in your FET switch is a pull-up every time ZD4 is conducting. I think there should be also a resistor across gate and source to force the FET to turn-off during secondary conduction.
My advice to you is to first use conventional IC control just to check your circuit and then you can switch to Hard switching control if you are already sure that everything is already working.
Regards.
Hi,
We have to make sure that the snubber is no a problem anymore.
You can remove the snubber first and see if it would be working. just make sure to work on the lower range of your input voltage due to high spikes on the switch without the snubber.
Question: where is the 6.8ohms placed? Is it parallel to the cap? If not what is the value of the resistor in parallel with the cap? Or you can send the schematic..
Regards