PMP7579 circuit

Dear Sir,

Please help us for the above issues.

Thanks & Regards,

Rajasekaran.S

Dear Sir,

Please help us for the above issues.

Thanks & Regards,

Rajasekaran.S

Dear Sir,

Please help us for the above issues.

Regards & Thanks

S.Rajasekaran

Dear Sir,

Please help us for the above issues.

Regards & Thanks

S.Rajasekaran

Dear Sir,

Why no one is not answering my questions from Ti?
The issue is pending for a long time since August 2014.

Thanks
S.Rajasekaran

Rjasekaran:
Please check the transformer. Sometimes poor transformer contruction can lead to those failures. Did you use the same transformer as the one used in the reference design?
David Zhang

Dear David Zhang,

Thanks for your reply.

We used the same transformer suggested for this design.

The transformer issues for which problems sl.no.1 or 2

Regards,
Rajasekaran.S

Rajasekaran:
Poor transformer constructiion leads to snubber failure due to high leakage inductance. I don't see how C13 can fail.
David Zhang

Dear Sir,

Thanks for your suggestion.

We will check with the transformer supplier for constructions.

How to avoid the failure of capacitor C13 ( 1uF).

Thanks  & Regards,

S.Rajasekaran

 

   Please use high quality X7R ceramic capacitor with voltage rating 16V or higher for C13.

 

David Zhang

Dear Sir,

We are using the Yageo make capacitor for 50V and X7R type, Part No. CC1206KKX7R9BB105

Thanks & Regards,
S.Rajasekaran

Dear Sir,

We are using the Yageo make capacitor for 50V and X7R type, Part No. CC1206KKX7R9BB105

Thanks & Regards,
S.Rajasekaran

Rajasekaran:
Then this capacitor should not get damaged because there is no voltage higher than 50V across this cap. Can you try a capacitor from TDK or Murata?
David Zhang

Dear David,

We are trying with the options for C13 capacitor suggested in the previous mail.

In the same circuit now facing a new problem, the failure of capacitor - C15 (10uF/25V) - Bias supply capacitor.

Solutions required.

Thanks & Regards,

S.Rajasekaran

Rajasekaran:
Can you please check the voltage on C15? If it is too high, you need to reduce the number of turns of the transformer secondary bias winding.
David Zhang

Dear David,

Thanks for the solutions.

I wrongly mentioned the capacitor reference instead of C5.

The problem in C5 primary bias capacitor, we used the value - 47uF/50V.

According to your need the measured voltage at the capacitor C5 - Positive - 13V to 15Vdc.

Thanks & Regards,

S.Rajasekaran.

Rajasekaran:
In the schematic you posted, C5 is not a 47uF/50V cap. Did you mean C6? Can you please clarify? Did the IC also get damaged when C6 failed?
David Zhang

Dear David,

Capacitor - C6 - 47uF/50V.

IC is not failling but the output of the driver load is flickering, when replaced with new capacitor its working fine.

Thanks & Regards,

S.Rajasekaran

Rajasekarn: What is the part number of the capacitor you are using?
David Zhang

Dear David,

Capacitor Part Number - IT1H47013BM, Make - Incap, Series - IT series, 105deg, 2000hrs, Value - 47uF/50V, Size - 6.3x11.

One More Questions, we have two different types of Layout for PMP7579,

1. For the First Layout i am getting A-THD = 4 to 5%, at 100nF for capacitor - C4.

2. For the Second Layout i am getting A-THD = 50%, at 100nF for capacitor - C4, when we increasing the capacitor from 100nF to 2uF it starts reducing.

3. For the above statement -Capacitor C4 - 100nF = A-THD - 50%, at 1uF - 18% and at 2uF - 9%

First Layout - Below

 

Second Layout - Below

There is a difference in the legends between PMP7579 and the above attached layout.

If you need a gerber file for checking, please send a mail - id.

Thanks & Regards,

S.Rajasekaran

Rajasekaran:
I can not find this capacitor maker Incap. Can you try some high quality low ESR electrolytic cap? Increasing C4 basically slows the feedback loop. If the feedback loop is too fast, you don't get good power factor correction and the THD is high.
The first layout looks good. The second layout is not as good as the first one. It does not have clear spacing between primary and scondary. The switching circuits are too close to the input and it may affect the EMI.
David Zhang

Dear David,

Thanks for the suggestion.

What is the maximum value we can go up for the capacitor - C4.

If any performance will be affected due to capacitor C4 - high value, because we giving warranty for the product.

Please find the new layout and have your comments.

Rajasekaran:
You don't want C4 value too high. If C4 value is too high, the feedback loop will be too slow and there will be overshoot/undershoot of LED current during input voltage change.
David Zhang

Dear David,

1. Have your comments on the Third Layout attached in the previous mail. (Whether the Ground Track is OK).

2. We are limiting to 2.2uF for C4 capacitor and due to this when the input voltage is 100Vac, the output current is 345mA (Reduced from 380mA).

3. Above 110Vac, the output current is 380mA that is stable.

4. We planned to use snubber as - 27K & 10nF, instead of 11K & 22nF - Whether the values are OK for 27K & 10nF

Thanks & Regards,

S.Rajasekaran

Dear David,

1. Have your comments on the Third Layout attached in the previous mail. (Whether the Ground Track is OK).

2. We are limiting to 2.2uF for C4 capacitor and due to this when the input voltage is 100Vac, the output current is 345mA (Reduced from 380mA).

3. Above 110Vac, the output current is 380mA that is stable.

4. We planned to use snubber as - 27K & 10nF, instead of 11K & 22nF - Whether the values are OK for 27K & 10nF

Thanks & Regards,

S.Rajasekaran

Rajasekaran: This layout looks good.David Zhang

Dear Sir,

Now we are facing a problem after a long time in the production line.

Failure of Capacitor (C6 in the pcb board - it connects from optocoupler to ground)  C4 - 0.1uF/50V due to that output current is LOW.

If we change the capacitor C4 too new one or if we resoldering it starts working.

Please let me know the reason for the failures.

Thanks & Regards,

S.Rajasekaran

Dear David Zhang,

Awaiting for your reply.

Dear David Zhang,

Awaiting foe your reply.

Dear David,

What will happen if we use a optocoupler - PC817C instead of PC817A.