LM5023: LM5023 POWER SUPPLY, snubber Resistor heating,

SATHISHKUMAR vishwanatha

Part Number: LM5023

Hi,

We are designing a LM5023 POWER SUPPLY, Here the snubber resistor is heating,

Find the attached schematic.

In schematic R3,R4 resistance value is 50K/2W, D2 is UF4007, Across R3,R4 parallel connected TVS diode 1.5KE200CA connected,

Mosfet and Secondary diode is no-heating,

Kindly suggest the appropriate snubber resistor value.

Input: 84V -264 Vac

Output: 24Vdc, 4.2A

Transformer destails,

L= 239uH, Primary : 40T, Sec= 7T , Aux= 4T

Regards,

Sathishkumar V

over 6 years ago

0 Mike O' over 6 years ago

TI__Guru* 86286 points

Hello,

Please note that you are referring too RCD leakage clamp resistors. The resistance on this clamp is generally in the magnitude of 511k ohms where your design is using two 15 k ohms in parallel.

Please note the power dissipated by your resistor is P = (V^2/R). To keep the resistor from getting hot I would recommend selecting a resistor for this application that dissipated less than 125 mW. Please note that V in the above equation is roughly Vout*Np/Ns.

Regards,

0 SATHISHKUMAR vishwanatha over 6 years ago in reply to Mike O'

Intellectual 495 points

Hello Mike O'

511K snubber resistor is working,

Suggest the snubber capacitor Value, Because the Mosfet Vds voltage is going to very high peak to peak voltage.

Regards,

Sathishkumar V

0 SATHISHKUMAR vishwanatha over 6 years ago in reply to SATHISHKUMAR vishwanatha

Intellectual 495 points

Hello Mike O,

Can you send the calculation how you calculate the snubber resistor and capacitor value.

It is help us in future.

Awaiting for your reply,

Regards,

Sathishkumar V

0 SATHISHKUMAR vishwanatha over 6 years ago in reply to SATHISHKUMAR vishwanatha

Intellectual 495 points

Hello Mike O,

Kindly share your email address, We can discus in the email.

Awaiting for your response.

Regards,

Sathishkumar V

0 Mike O' over 6 years ago in reply to SATHISHKUMAR vishwanatha

TI__Guru* 86286 points

Hello,

We try to have all technical support on the e2e remain on the e2e. So all can gain knowledge from the technical support.

If you require more aid than the e2e can support please contact your local TI sales and local field applications may be able to provide support.

The answer to your question in regards to setting up a snubber. I searched the TI website and could not find any information on how to setup and RCD clamp. However, I found the following Web article that discusses how to do this in detail which you might find helpful.

Regards,

Mike

0 Mike O' over 6 years ago in reply to Mike O'

TI__Guru* 86286 points

Did you have a chance to review the link on how to properly setup the snubber. It should help with your design.

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LM5023: LM5023 POWER SUPPLY, snubber Resistor heating,