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LM5023: LM5023 POWER SUPPLY, Load regulation problem

SATHISHKUMAR vishwanatha
Intellectual 495 points
Part Number: LM5023

Hi,

We are designing a LM5023 POWER SUPPLY, Output voltage decreased when increasing LOAD.

Find the below test results,

When we applying Input voltage Above 210Vac output voltage decreased. 

100W PSU TESTING RESULTS
SL.NO INPUT AC voltage in volts  At no-load At 1A Load At 2A Load At 3A load
Output Voltage  Voltage pk-pk @ Vds Output Voltage  Voltage pk-pk @ Vds Output Voltage  Voltage pk-pk @ Vds Output Voltage  Voltage pk-pk @ Vds
1 85 24.08 312 24.03 316 23.96 324 23.84 336
2 110 24.07 344 23.98 352 23.95 360 23.89 372
3 150 24.08 392 23.9 402 23.89 404 23.86 412
4 180 24.06 416 23.84 448 23.83 452 23.82 464
5 210 24.03 460 23.35 488 23.58 500 23.75 500
6 230 24.03 488 22.96 512 23.14 520 23.25 524
7 254 24.02 524 22.51 544 22.59 548 22.8 564
8 265 24.02 540 22.32 556 22.44 564 22.6 568
9 274 24.02 548 22.14 570 22.22 580 22.32 584

Input: 84V -264 Vac 

Output: 24Vdc, 4.2A

Transformer destails,

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

Find the attached schematic.

 Kindly suggest the to overcome this issue,

Regards,

Sathishkumar.V

100W PSU TESTING RESULTS
SL.NO INPUT AC voltage in volts  At no-load At 1A Load At 2A Load At 3A load
Output Voltage  Voltage pk-pk @ Vds Output Voltage  Voltage pk-pk @ Vds Temp °c @ 1Min Output Voltage  Voltage pk-pk @ Vds Temp °c @ 1Min Output Voltage  Voltage pk-pk @ Vds Temp °c @ 1Min
1 85 24.08 312 24.03 316 54 23.96 324 73 23.84 336 100 (@30 sec) 
2 110 24.07 344 23.98 352 57 23.95 360 78 23.89 372  
3 150 24.08 392 23.9 402 55 23.89 404 82 23.86 412  
4 180 24.06 416 23.84 448 55 23.83 452 80 23.82 464  
5 210 24.03 460 23.35 488 50 23.58 500 90 23.75 500  
6 230 24.03 488 22.96 512 48 23.14 520 88 23.25 524  
7 254 24.02 524 22.51 544 63 22.59 548 88 22.8 564  
8 265 24.02 540 22.32 556 59 22.44 564 85 22.6 568  
9 274 24.02 548 22.14 570 59 22.22 580 81 22.32 584  
  • 0
    TI__Guru* 78486 points

    Hello,

    Do you think the design might be hitting cycle by cycle peak current limit.  Try reducing R13 and R14 to see if it resolves the issue.

    I would also recommend double checking your transformer turns ratio.

    Regards,