UCC28C42: Voltage drop

Vishal Kakade

Intellectual 930 points

Part Number: UCC28C42
Other Parts Discussed in Thread: TLV431, TL431

Hello,

I have designed a power supply for following specifications on webench.

Vin: 165V to 265V @ 50Hz

Vout: 12V

I_out_max: 5A

without load I am getting exact 12V at output. But after connecting the load of 2.5A, My voltage is droping to 9.5V.

What are the possible resons for this to happen? I have assembles 4 cards getting issue only in 1 board.

Regards

Vishal Kakade

over 6 years ago

0 Peter Meaney over 6 years ago

TI__Mastermind 31580 points

Hi Vishal,

if you only see the issue on 1 board then it most likely as assembly issue or soldering contact issue on that card. i would inspect the card for defects and compare the voltages in the feedback circuit between a good and bad card.

Regards

Peter

0 Vishal Kakade over 6 years ago in reply to Peter Meaney

Intellectual 930 points

Hello Peter,

I am getting Ref voltage of TLV431 as 1.89V instead of 2.5V.

Regards

0 Peter Meaney over 6 years ago in reply to Vishal Kakade

TI__Mastermind 31580 points

Hi Vishal,

When the voltage on the ref of the TL431 drops is the duty cycle of the PWM gate drive changing to a higher value?

Thanks

Peter

0 Peter Meaney over 6 years ago in reply to Peter Meaney

TI__Mastermind 31580 points

Hi Vishal,

I hope you have made some progress over the last week, if you have more questions please open a new post.

Regards

Peter

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UCC28C42: Voltage drop