UCC256303: UCC256303 issue confirm

Wenhsiang Lin

Intellectual 520 points

Part Number: UCC256303
Other Parts Discussed in Thread: UCC256403

Hi Team:

Please help to confirm below question , feedback from customer , thanks.

1.What kind of issue cause voltage drop during maybe 1~2 minutes at any output load?

Ch1:Vout voltage , Ch2:LLC current

2. What kind of issue cause VCR over 7V ?

Ch1:VCR , Ch2:LLC current

3. What kind of issue cause LLC current not smooth ?(max load)

over 6 years ago

0 Hong Huang over 6 years ago

TI__Guru 74115 points

Please provide your schematics to help further talk.

0 Wenhsiang Lin over 6 years ago in reply to Hong Huang

Intellectual 520 points

EP1720 SCH for LLC 190626.pdfHi Hong:

Please refer as schematic as attached , thanks.

Regards / Mark

0 Hong Huang over 6 years ago in reply to Wenhsiang Lin

TI__Guru 74115 points

1.What kind of issue cause voltage drop during maybe 1~2 minutes at any output load?

Was the operation with single converter or two converters in parallel?

2. What kind of issue cause VCR over 7V ?

Was VCR over 7V due to output voltage drop?

3. What kind of issue cause LLC current not smooth ?(max load)

One possibility is the gate drive not stable - can be due to the noise. Can you provide HO-HS and LO-GND waveform along with the LLC current?

0 Wenhsiang Lin over 6 years ago in reply to Hong Huang

Intellectual 520 points

Hi Hong:

please refer as below , thanks.

1.What kind of issue cause voltage drop during maybe 1~2 minutes at any output load?

Was the operation with single converter or two converters in parallel? -->only one

2. What kind of issue cause VCR over 7V ?

Was VCR over 7V due to output voltage drop? -->Yes , it was.

3. What kind of issue cause LLC current not smooth ?(max load)

One possibility is the gate drive not stable - can be due to the noise. Can you provide HO-HS and LO-GND waveform along with the LLC current? -->will inform RD to get waveform

0 Hong Huang over 6 years ago in reply to Wenhsiang Lin

TI__Guru 74115 points

1.What kind of issue cause voltage drop during maybe 1~2 minutes at any output load?

It is likely that high noise on ISNS pin causing shutdown. If this is the root cause, you can increase C19 value to be higher to see the shutdown can be resolved.

Another try is to use UCC256403 which is pin-to-pin compatible. UCC256403 is less noise sensitive on its ISNS pin than UCC256303.

0 Wenhsiang Lin over 6 years ago in reply to Hong Huang

Intellectual 520 points

Hi Hong:

Got is and many thanks.

Regards / Mark

Power management

Power management forum

UCC256303: UCC256303 issue confirm