LM5180EVM-DUAL: Transformer SPEC

Kai Hsiao

Guru 12675 points

Part Number: LM5180EVM-DUAL
Other Parts Discussed in Thread: LM5180, LM5155, LM5160

Hi Sir

1. Could you kindly help to provide LM5180EVM - dual's Transformer YA8916-BL SPEC?

2. I would like to know how to design this transformer ,just like Pri-DCR and Sec-DCR

3. Below is Transformer calculator result ,may I know turn ratio 4:1:1 is correct or not ?

Copy of LM5180 PSR Flyback Quickstart Calculator r2.xlsx

Thanks

over 5 years ago

0 Timothy Hegarty over 5 years ago

TI__Mastermind 49947 points

~YA8916-BL -- 15V and -8V dual outputs.pdf

Hello Kai,

A 4 : 1 turns ratio sets a really high duty cycle at Vin(min), ~78%. A typical guideline for max duty cycle is 60-70%, otherwise the secondary peak current gets really high. Note that +/-15V at 0.3A is a high output power for the LM5180.

See attached transformer spec.

Regards,

Tim

0 Kai Hsiao over 5 years ago in reply to Timothy Hegarty

Guru 12675 points

Hi Sir

1. I change the turn ratio form 4:1 to 2:1 and keep duty 63% ,but the output power is 7.39W and have red mark

have any idea how to solve this issue ?

2. I have no idea about this case how to design the transformer's DCR ,could you provide your suggestion ?

0 Timothy Hegarty over 5 years ago in reply to Kai Hsiao

TI__Mastermind 49947 points

Hello Kai,

The output power requirement is likely too high for the LM5180. The max output power for a given turns ratio is indicated and the cell turning red means that the required output power is not available at Vin-min.

Please consider a Fly-Buck converter solution such as the LM5160 or alternatively a flyback controller such as the LM5155.

Regards,
Tim

0 Kai Hsiao over 5 years ago in reply to Timothy Hegarty

Guru 12675 points

Hi Tim

I change +/- 15Vout from 0.3A to 0.2A

May I know the transformer can follow below calculator result ? turn ratio 2:1:1 is correct or not ?

0 Timothy Hegarty over 5 years ago in reply to Kai Hsiao

TI__Mastermind 49947 points

Hello Kai,

I recommend using a 1 : 1 : 1 transformer. This enables lower Lmag and DCRs and should provide better leakage inductance. Take a look at the LM5180 dual-output EVM (just change the second output from -8V to -15V).

Regards,
Tim

0 Kai Hsiao over 5 years ago in reply to Timothy Hegarty

Guru 12675 points

Hi Tim

I change the turn ratio to 1:1:1 ,but the max output have red mark

Our requirement is Vout = +/-15V ,May I know what's the "maximum output current" that LM5180 support ? iout1 need to equal Iout2

when design LM5180 for maximum power ,1:1:1 transformer you prefer ,is it correct ?

May I have a real answer for once ?

0 Timothy Hegarty over 5 years ago in reply to Kai Hsiao

TI__Mastermind 49947 points

LM5180-Q1 PSR flyback converter quickstart tool r5 -- 18-36Vin, 15V dual at 0.2A.xlsx

Hi Kai,

Yes, it's marginal at 18V input, but I think you're using an old version of the quickstart file.

See attached. I used 1.5 : 1 : 1 to provide more margin at low Vin.

Regards,

Tim

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LM5180EVM-DUAL: Transformer SPEC