LM5181: The reference design for LM5181 PSR Flyback Converter Design Tool

Michiaki Tanii

Expert 4610 points

Part Number: LM5181

Hi team,

Could you kindly give the reference design for LM5181 PSR Flyback Converter Design Tool for the below specifications ?

Input voltage 16V ± 10%

Output voltage 16V ± 10%

Output current Max 50mA, Typ 1mA

Customer has been considering LM5181 but if you have another recommendation, please let me know.

Thank you and best regards,

Michiaki

over 5 years ago

0 Iven Su over 5 years ago

TI__Expert 8245 points

Hi,

Please get all the design parameters by the quick start tool:

https://www.ti.com/tool/LM5181DESIGN-CALC

0 Michiaki Tanii over 5 years ago in reply to Iven Su

TI__Expert 4610 points

Iven

Could you kindly advise how to select the transformer ?

As you can see, typ output current is 1mA and it would be light load.

I would much appreciate I get any information if there is any concerns.

Thank you and best regards,

Michiaki

0 Iven Su over 5 years ago in reply to Michiaki Tanii

TI__Expert 8245 points

Hi,

Please just refer to the detailed transformer deign guide:

https://www.ti.com/lit/an/snva805/snva805.pdf

0 Michiaki Tanii over 5 years ago in reply to Iven Su

TI__Expert 4610 points

Hi Iven,

Please let me confirm the value of transformer-T1

In the datasheet, customer can choose a turns ration based on 60% and following the equation 14, Nps will be around 1.3 in their specification.

My concern is the load is too light of typ 1mA and following the equation 15, LMAG will be so large.

Could you kindly advise if LM5181 can be applied to their specification ?

If no, do you have any recommendation devices for their specification ?

Thank you and best regards,

Michiaki

0 Iven Su over 5 years ago in reply to Michiaki Tanii

TI__Expert 8245 points

Hi,

Please do not use a light current to calculate inductance, just use the maximum load of the device to calculate it. Thanks.

0 Michiaki Tanii over 5 years ago in reply to Iven Su

TI__Expert 4610 points

Hi Iven,

Please let me double confirm the below

- LM5181 could be applied to the application which is load current of 1mA and peak current 50mA

- In the datasheet, the the turns ratio of transformer is supposed to be about 60% at max duty cycle, customer could use 1:1 transformer in their condtion.

Are there any problems on the above ?

Thank you and best regards,

0 Iven Su over 5 years ago in reply to Michiaki Tanii

TI__Expert 8245 points

Hi,

1. LM5181 can support load current of 1mA and peak current 50mA with proper design.

2. 60% is not turns ratio, it's max duty cycle. Please follow Equation 14 in its datasheet or just use quick start tool to calculate proper component values.

https://www.ti.com/tool/LM5181DESIGN-CALC

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LM5181: The reference design for LM5181 PSR Flyback Converter Design Tool