12V Reg Input 460VAC

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Hi,

 

I have designed 12V, 1Amp (using maximum load 250mA) with 230V to 480VAC.

 

I have see frontend section is started burning including the cable connectors in some case. Th efailure rate is 30%.

 

I am using TNY278 device in this design with stak MOSFET.

 

Can you please suggest if TNY278 can take care of this high voltages.

 

I am using 1N4007 diodes for bridge rectifier for 3 phase. Should I add two diode inseris to increase the reverse break voltage?

 

 Thanks,

Siva 

Tiny Switch design specs is up to 264Vac. From your discription, is your system overloaded so things are buring? What is your output power?

Hi,

I am using stackFET addition to TNY278, output is designed to 12V, 1Amp. But my application maximum I am drawing 250mA on 12VDC.

The Input voltage can be between 320V to 480VAC.

Since I am using StackFET is it ok to continue. Can you please let me know the cause for failure on fusible resistor and cable connector to be burnt.

When I check on dailed device nothing is happend to the PIN device, stackFET, and all. Only front components fusible resistor, connector cables burnt. I am thinking if the PI device is missbehaved at this voltage and caused for the load on front components.

Please reply ASAP. I have attached the drawing.

Siva

Hello,

I need your reply ASAP. I have product already with TNY278 device as recomended by one of your application engineering partene.

If TNY278 with stackFET doesnt work, I have big problem to respin the board. Please confirm me asap. 

Siva

Dear Siva:

First of all, the stackFET addition to TNY278 solution can be working under 480Vac with proper design. There is no need to change the rectifier diodes since they are rated at 1000V.

From what you discribed, basically the burning of connector cable or fusiable resistors are caused by over current (Thermal issue because of the high input current). I would recommand you to do following actions:

1. Check the drain voltage and the primary current see if they are working correctly. Make sure the transformer is not satuated during normally working condition.

2. Measure the input current, see if the current is abnormal, especially during the burning condition.

3. Check the PCBA carefully, make sure the right components put on the PCB are correct.

4. Check if the output short circuit protection is working properly. (check what happen if you overload the power supply.)

I did not see a obivious mistake on the schematic, but the burning of the connector and fusiable resistors is not normal, you will need to check step by step to see what happen during this burning. Also make sure you select the good fusiable resistor and connector power rating.

Hope these will be helpful.  

If you can send me the transformer design file, I can have further check.

Please find attached transformer design that is proposed by one of PI representative. Please let me know if there is any issues with that.

Siva

Hi, Siva:

Thanks for the information. You are right, the voltage rating for the diodes have to be higher.

Did you try to do the tests I recommanded, do you have any results on that?

By the way, what is the minimum working voltage for the power supply you designed? The primary current is the higher during the minimum working voltage.

Thank you for reply.

I have attached the transformer details. Pleasef ind the same.

I understand diode peak should be rated 1200V i.e. for three phase is 6 * VRMS = 1126V. (vrms is 460V phase to phase)

Siva

Hi,

I am using stackFET addition to TNY278, output is designed to 12V, 1Amp. But my application maximum I am drawing 250mA on 12VDC.

The Input voltage can be between 320V to 480VAC.

Since I am using StackFET is it ok to continue. Can you please let me know the cause for failure on fusible resistor and cable connector to be burnt.

When I check on dailed device nothing is happend to the PIN device, stackFET, and all. Only front components fusible resistor, connector cables burnt. I am thinking if the PI device is missbehaved at this voltage and caused for the load on front components.

Please reply ASAP. I have attached the drawing.

Siva