How to protect for Surge Voltage and Current in DC

Dear All,

I'm facing a issue in the below attached circuit, Here the diode D200 a TVS Diode was broken frequently i don't know the exact reason but it may broken due to any surge voltage. Please suggest me to solve the issue.


Regards,
Kumar.

Hi,

Please tell us your maximum DC input voltage at VB, with all expectable drifts and errors.

According datasheet, the stand off voltage of the TVS diode is 38.1V. You should never go beyond to this value at normal operating conditions.

Please do a measurement at this node at different load conditions. In worst case your (undamped) LC filter causes some ringing with voltages beyond the 38.1V. (Maybe cused by the switcher, in normal or burst mode)
I personally don't like these undamped LC circuits, because they may generate a high resonance voltage.
At least by connecting/disconnecting power.
I recommend to add a RC damping circuit.

As long as you continously are below 38.1V during normal operating conditions I see no reason for the TVS diode to fail.

Btw: what's the meaning of "NC" or "OM" at the capacitor symbols?

Klaus

Hi,

Worst condition Maximum Input Voltage at VB is 28V DC but normal operating voltage is 24V DC. This too also works fine more than 5lakh cycles suddenly got damaged due to the unexpected reason. I'm not able to find the exact reason for broken that diode(TPSMC47A). Is there any way to protect the circuit by using any external circuit to arrest surge /high voltage/ reverse current?

According datasheet, the stand off voltage of the TVS diode is 38.1V. You should never go beyond to this value at normal operating conditions.

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Input voltage slightly above stand-off level can be well tolerated, problem is enduring overvoltage above Vbr that causes overheating of the TVS diode. TVS is good to absorb µs or even ms surge voltage but can't protect against too high DC level. Reverse voltage should be safely suppressed by the series diodes.

A SCR crow-bar in combination with a fuse or a MOSFET disconnect switch with sufficient voltage rating can help.

You didn't tell yet about the primary power source, what is it?

FvM said:

You didn't tell yet about the primary power source, what is it?

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Working environment of the device is welding industry through stabilizer, MCB finally from the SMPS getting power to this device.

No idea how the SMPS can supply overvoltage. Is there a possibility that welding current flows through the circuit ground?

Hello dsanthosh67,
You could try inserting a 4.7 ohm 5 Watt resistor between the power IN and C254 to be used
as a surge limiter, as was used in a lot of earlier CRT televisions.
Regards,
Relayer

Relayer said:

Hello dsanthosh67,
You could try inserting a 4.7 ohm 5 Watt resistor between the power IN and C254 to be used
as a surge limiter, as was used in a lot of earlier CRT televisions.
Regards,
Relayer

Click to expand...

Thanks for your suggestion, I will try that surely. I have an alternate idea too please comment about that how much it will helpful to me. It was connecting ground terminal with the earth, I don't know exactly how it will work. Awaiting for your valuable feedback's..

Hello dsanthosh67,
I don't think you should connect the SMPS grounds to earth.
I think its should be a floating supply. You don't really have any isolation on it. Its hard
to say without seeing the rest of the schematic diagram.
Where is the input voltage derived from? I doubt it would be from a transformer supply.
Please let us know.
Regards,
Relayer