LM5046: phase shift full bridge

rizwan ali1

Part Number: LM5046
Other Parts Discussed in Thread: LM5045, UCC28950

Hi TI Team,

I have to design a power supply for one of my client with following specifications;-

TI IC used = LM5046
input voltage range = 37v to 57v
output voltage/power = 30v/1000W
switching frequency = 256kHz
efficiency = ~95%

Please resolve my following query;

a. Do you have any reference design fulfilling above specification? If yes then please share.
b. Do you have any excel based design calculation sheet for LM5046 ic? If yes then please share.
c. Do you have any design guide for same? If yes then please share.

d. I have checked and compared the datasheets of LM5045 and LM5046. It seems both are having almost same parameters, pin to pin match and same package. Is it possible to replace lm5045 with lm5046 keeping rest other BOM same?

Eagerly waiting for the reply

best regards
Rizwan Ali

over 3 years ago

0 Eric Reicher over 3 years ago

TI__Expert 7900 points

Hello Rizwan,

a. We have a similar reference design, but it does not use the LM5046. It uses the UCC28950 phase-shifted full-bridge controller: 38V-60V input, 54Vout, 30Aout (1620W), efficiency greater than 96%. See the documentation here https://www.ti.com/tool/PMP6712.

b. There is no Excel based tool for the LM5046. However, there is a Mathcad Design Calculator, and a Pspice model: https://www.ti.com/product/LM5046?keyMatch=LM5046&tisearch=search-everything&usecase=GPN.

c. Other than the information in the data sheet I did not find a design guide. There are a few other technical documents that may help, including an LM5046 evaluation board and a couple of Application Notes:

https://www.ti.com/tool/LM5046EVAL

https://www.ti.com/lit/an/snva474b/snva474b.pdf?ts=1627666917149&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM5046%253FkeyMatch%253DLM5046%2526tisearch%253Dsearch-everything%2526usecase%253DGPN

https://www.ti.com/lit/an/snva610/snva610.pdf?ts=1627666935209&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM5046%253FkeyMatch%253DLM5046%2526tisearch%253Dsearch-everything%2526usecase%253DGPN

d. According to the web site description, the LM5045 can only operate to 50% duty cycle while the LM5046 can operate up to 100%.

I also see a difference in the block diagrams just before the Delay Timers and Driver Logic.

LM5045;

LM5046;

Regards,

Eric

0 rizwan ali1 over 3 years ago in reply to Eric Reicher

Prodigy 70 points

Hi Eric

Thanks for the valuable information. I have started the design but need your support on my further queries.

1. Do we have any Design guide/document/calculation sheet for the PSFB transformer : L_leakage, L_prim and its other parameters calculation/selection ? If yes then please share.

2. Do we have any Design guide/document/calculation sheet for the PSFB primary and secondary MOSFETs loss calculation? If yes then please share.

waiting for your reply.

regards

Rizwan Ali

0 Eric Reicher over 3 years ago in reply to rizwan ali1

TI__Expert 7900 points

Hello Rizwan,

TI has not prepared calculation sheets for the transformer or MOSFETs. However, there is a 30 page detailed design guide for a 600W PSFB using the UCC28950. This guide does cover the transformer and MOSFET equation in detail: https://www.ti.com/lit/an/slua560c/slua560c.pdf?ts=1627911289843&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DSLUA560C%2526nr%253D81

Regards,

Eric

0 rizwan ali1 over 3 years ago in reply to Eric Reicher

Prodigy 70 points

Hi Eric,

Thanks for the support, you are really helpful but I need more help on clarity of below query.

If I am having working solution based on LM5045 with full bridge primary and full bridge synchronous secondary then is it possible to replace LM5046 without any other change?

Although thanks for sharing the architectural difference of LM5045 and LM5046 with us.

positively waiting for you response.

Regards
Rizwan Ali

0 Eric Reicher over 3 years ago in reply to rizwan ali1

TI__Expert 7900 points

Hi Rizwan,

I tracked down someone more familiar with the LM parts and asked him about swapping the controllers. His response:

"There should not be an issue swapping the parts. The EVMs are similar except for the current limit implementation. Placing the current sense in series with the power transformer for the LM5046 PSFB adds some uncoupled inductance for the resonant transition."

The EVMs have a difference but it sounds OK to swap parts for your application.

Regards,

Eric

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LM5046: phase shift full bridge