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Design conversion PKS604 to TOP266

Posted by: mjscottinnc on

We are converting an existing power supply design which used a PKS604 to a design using TOPS266. We used PI Expert, had the transformers made and I'm getting some strange results. Power up and initial working is good, but after about 3 - 5 seconds all the outputs start to have low frequency voltage hump in the output voltages. this design uses a Resistor/Zener feedback on the bias winding. Schematic attached.

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T1000-5.pdf 8.84 KB

Comments

Submitted by PI-NANO on 10/02/2014

Hi,

 

Could you please send your waveforms.

 

Also could you please attach your old schematic as well.

 

PI-NANO 

 

Submitted by mjscottinnc on 10/02/2014

Waveforms will be a problem, we still use standard cathode ray tube oscilliscopes and the scope camera broke years ago. As for the old schematic, that was lost about a year ago after a laptop crash. Has the primary zener feedback circuit been prototyped with the TOPS parts? I suspect that there is so little load on the Aux winding that the issue is responsiveness

Submitted by PI-NANO on 10/05/2014

Hi,

 

DC Bus capacitor (C1) in your design looks so small. Try increasing that capacitor an see if it makes any difference.

 

Are you supplying the DC input voltage to the converter?

 

How is the DC input voltage derived?

 

Is there a front end AC/DC converter? If yes, can you provide me the complete schematic.

 

Could you please send me your PIExpert design file as well. 

 

Regards,

PI-NANO 

Submitted by mjscottinnc on 10/07/2014

The full schematic I cannot release. This is a system which consists of the controller board (PIExpert side) and a power supply board. In the schematic I supplied you (PIExpert output) C1 is the calculated value from PIExpert. In reality, the circuit has a 180 ufd, 450 volt cap for C1 (C51) and a 2200pf 1kv (C27) noise reduction cap in parallel. The main DC voltage comes from a power supply board with a PFC which takes the line voltage (100 VAC to 255 VAC) rectifies it and steps it up to 350 VDC. The output of the PFC is peak detected with a 470ufd 450 volt capacitor. The power supply board and controller (PIExpert design side) are connected with 8 inch 18 AWG wire through a connector P8 on the controller side and .250 inch quick connect lugs on the power supply side. I have attached the implamentation schematic of the PIExpert design and the PIExpert design files


This is a known working design when using the PKS604 and was in production for over 2.5 years. As you know the PKS604 was discontinued due to patent infringement. 


Submitted by PI-NANO on 10/08/2014

Hi,

 

Can you try by only powering (without powering PFC Stage) TOPSwitch stage by applying DC input voltage with a DC source and see if it makes any difference?

 

And for your information, Peakswitch was discontinued because there were not many customers for this product and not because of any patent imfringement.

 

Regards,

PI-NANO 

Sorry for the delay, I had to travel to Japan on business. We did as you suggested and powered with the PFC off and got exactly the same thing. As for the panent infringement, that is what an email from Power Int to me said about a year and a half ago. If that is not the case, well that would contradict the email I received. In any case it really does not effect the current situation.

Submitted by PI-NANO on 10/29/2014

In reply to by Richard Wright

Hi, 

 

 Feedback loop is the next thing that we shold look at.

 

What is the frequency of the voltage hump that you are observing in the output voltage and what is the magnitude of your output ripple?

 

Can you try using TL431 based optocoupler feedback for debug purpose? And see if it eliminates or minimizes the problem?

 

Regarding Peak switch, 

 

I am an engineer here. I have posted the information whatever was given to me. If you need further clarification, I can refer to our legal department. They can give you the detailed information.

 

If you can provide your email address, I can forward the information to our legal department.

 

Regards,

 

PI-NANO