UCC28704: PMP11600 / pmp11612 /pmp40228 - UCC28704EVM-724 Voltage Sense

Lu Ha

Part Number: UCC28704
Other Parts Discussed in Thread: PMP11612

hello,

i design actually an inwall power supply and need a stable 5v source.

i decided to use the ucc28704 and read some reference designs and manuals about this chip.

regarding to official sheet i should use RS1 115kOhm and RS2 36,5kOhm, but i am wondering all official reference design except evaluation module

use 68kOhm instead of 115kOhm?

over 5 years ago

0 Benjamin Lough over 5 years ago

TI__Mastermind 26215 points

Hi Lu,

Thanks for your interest in UCC28704. RS1 and RS2 values depend on your input voltage range, primary to auxiliary turns ratio and secondary to auxiliary turns ratio. I would suggest following section 7.3.1.3 of the UCC28704 datasheet to determine your RS values: www.ti.com/.../ucc28704.pdf

Best Regards,
Ben Lough

0 Lu Ha over 5 years ago in reply to Benjamin Lough

Prodigy 150 points

hello,

i use this transformer:

WD1 (0.16mm, 60T) 1..3 | WD4(4T, TEX, 0.8mm)
WD3 (0.23mm, 8.5T) 5..2 |
WD2 (0.23mm, 19T)

input range: 90V-264VAC

and use 68k / 40.2k for Voltage Sense, but get 6V at no load condition.

0 Benjamin Lough over 5 years ago in reply to Lu Ha

TI__Mastermind 26215 points

Lu,

Could you share your schematic? Also what is the total output power of your converter?

Best Regards,
Ben Lough

0 Lu Ha over 5 years ago in reply to Benjamin Lough

Prodigy 150 points

0 Lu Ha over 5 years ago in reply to Lu Ha

Prodigy 150 points

we need only 3-4 watts on longterm, maybe few high consumption spikes up to 7watts.

0 Lu Ha over 5 years ago in reply to Lu Ha

Prodigy 150 points

we use a customized transformer based on this sheet

e2e.ti.com/.../Sumida-transformer_5F00_10349_2D00_T048_2D00_EXT_2800_EE1617_29002D00_VER4.pdf

0 Benjamin Lough over 5 years ago in reply to Lu Ha

TI__Mastermind 26215 points

Hi Lu,

I would suggest increasing the value of RS2. Also are you using WD2, WD3 or both for the bias winding?

Best Regards,
Ben Lough

0 Lu Ha over 5 years ago in reply to Benjamin Lough

Prodigy 150 points

hello, WD2 is used like in PMP11612 and only connected to GND for improved emi-performance (?). but we dissassembled one custom transformer and figured out, they are made wrong. WD2 were connected only to Pin5 and floating. after removing WD2 from PIN5 the circuit showed different behavior. but we will change the IC and verify again

0 Lu Ha over 5 years ago in reply to Lu Ha

Prodigy 150 points

issue is resolved. error was based on wrong made transformer and damaged ucc28704.

Power management

Power management forum

UCC28704: PMP11600 / pmp11612 /pmp40228 - UCC28704EVM-724 Voltage Sense