Hi

Hi, did you noticfy some componets broken on the failed power supply? Would you please attached the schematic, and transformer spec?  

Thanks for reply,

No any component/physical damage seen on card.

smps which are not getting on that smps also powered ON automatically after 2 hours. Now all smps are working fine.

as per your request i am sending you schematic & Transformer sheet. 

Hi,

Thanks for the file. I did not see any significant issue to cause the power on issue from the schematic.

Are you saying there is no issue now?  

HI,

Yes, all smps are working ok now. But we not getting why large no. of power supply gets off at same time & gets on after 20 to 30 mins.  

What will be efftect of harmonics on power supply?? Because of harmonics this type of problems can occure in smps??

How much is the hysterisis voltage for line overvoltage protection??

Hi,

I agree, it is not normal to have the power supply start to work after 20 to 30 minutes. Does the problem still exist when you say all the smps are working ok now?

Depending on your resistor on the V pin, it will have differnt overvoltage protection, you can refer to the data sheet or application note to detail calculation. But this is nothing to do with the harmonic voltage.  

In which smps we observed problem previously that smps are working fine now.

But same problem seen in anather 18 smps (all 18 smps are in same panel) i.e. all smps gets off at same time and resumes after 2 hours. Also we checked Aux. supply which is 255Vac when smps gets OFF and TOP switch temp near about ambient temperature only.

We not getting what is the problem exactly. 

Hi,

If all the 18 power supplies, which has issue, are from the same panel, you may check if any components that put on the board is  with wrong value.

Especially check the resistor value on the OV pin, this is what I can think. You could try to use different resistor value of the V pin, seeif the power supply is off at 255Vac or not. Based on your calculation, what is the voltage level that th power supply supposes to get off?

Resistor values are Okay i.e. 3.44M, As per design at no load it turns off at 275Vac & gets ON at 265Vac but at load condition it gets off at 300Vac & turn on at 270Vac. Why OV protection behaviour is different for no load & load condition?

We not able to try out anything on these smps as all are at site and in panel.

Are there any possibilities that this type of problem can occur because of problem in Aux. supply or in source? 

Hi,

For my understanding, the two facts may cause the different OV protection behavior at no load & high load condition. 1. At no load and full load, the junction temperature will be different, the OV levle may be changed because of the temperature, there is one curve figure 24 in the data sheet. 2. The bias winding voltage is different at light load and full load, there leakage current through the zener, diode and resistor from the bias winding to the V pin may be different because of different bias winding voltage.  

Okay. This both facts are playing role in different OV protection at no load & full load.

I think OV protection is not problem for power supply getting turn off. What else thing because of power supply getting off?

Are there any possibilities that this type of problem can occur because of problem in Aux. supply or in source i.e. supply is not proper?  

Hi, 

Sorry, what do you mean by problem in Aux. supply or in source?

I guess it depends how you define the "get off". With the OV/UV or overtemperature, the power supply will off, (disabling the switch of the MOSFET). Under some other fault condition, like output short circuit, or feedback loop open, the power supply will enter into auto restart...

I mean large numbers of SMPS getting off at same time in a panels what are chances of getting off because of any problem in source?

Or what will the problem because of power supply getting off same time?

Such a behavior will be most like caused by the test setup. Do you have a chance to measure the bulk capacitor volttage or drain voltage of the mosfet for each of the power supply when the power supply got off? I am suspecting the input voltage just get disconnected if the power supplies under test has independed loads.

Are the power supplies share the same load during the test? If it does, the load shorted will cause all the power supply went to auto restart mode, there will be no output voltage in this case. Please check 

It is not possible to measure bulk capacitor voltage as all power supplies in panel and at site (field). This problem we have not observed continously, this we have observed 4 to 5 times and before 20 daysafter that it not observed again.

Every power supply has different load. When all power supplies are off at same time we have measured supply voltage with multimeter it is near about 245Vac that means input supply not get disconnected.

After that we have monitored input supply on dso and we found distortion in input supply (All power supply has same input voltage). But this we have monitored when power supply ON (As we not found power supply off again).

If seen noise level increases above overvoltage threshold can it will go in shutdown? i.e. because of noise/spikes in input supply power supplies are getting off? 

Also we try to simulate overvoltage protection found that when power supply gets off because of overvoltage it takes 10 sec to resume after normalization of inpot voltage & in between if overvoltage condition comes again it will remain is off for anather 10 secs.

Hi,

If the same input voltage used for all the units in the panel, and all of them went to shut off at the same time, mostly likely the power supply shut off by overvoltage, under voltage or disconnection of the input voltage. How bad is the noise or spike of the input voltage that you mentioned, you will need use the scope to monitor it.

As there is a relatively big capacitor on the DC bus, normally very short period of noise will not creat too high bus voltage, which directly related to the overvoltage or under voltage protection. So it is all about the bus voltage, if the voltage spike or noise is high and constantly appears, then it may cause the bus voltage rise higher than the over voltage protection level, which will shut down the power supply.  

Hi

Is this problem solved? if solved then how?

I have same problem. I have two TOPswitch in one SMPS (TOP265EG & TOP264EG).

Same input line supply but only TOP264 gets off in SMPS.

Problem not found in all SMPS but happens in full load operation.

After Off & On; SMPS works fine. after that no problem founds.

Please help if anything you suggest.

Is this fault of false triggering at V pin?

Can i add Output overvoltage shutdown circuit.i.e. 5k1 resistor & 1N4148 diode between V pin & bias o/p winding.

Hi,

Thank you for reaching out to us through this page. Upon checking, I think you also posted the similar inquiry on this link https://www.power.com/community/forum/ac-dc-conversion-forum/2021/top264eg-randomly-gets

We acknowledge your inquiry and it has now been delegated to our support group. They will attend to your inquiry the soonest possible time. Thank you for patiently waiting.

Best regards,

PI-Lupin the Third