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LM5026: Duty

Jamie Tseng
Intellectual 2405 points
Part Number: LM5026

Hi Team,

My customer apply LM5026 in their new project, but the duty cannot meet their expectation.

The current situation is that DUTY cannot be fully expanded to the size we need.
The DUTY in the specification can reach 80%. In the case of 9VIN, its duty = 72~78%.
Since the actual application will reach DUTY = 76%, Please help analyze why the duty cycle is reduced.

CH1: VIN CH2: UVLO PIN CH3: DUTY
The figure below shows the value measured by the LM5026 control board, VULO = 1.377V and its duty cycle = 74.608%

The figure below is to adjust the UVLO of the control board to 1.25V to obtain the maximum DUTY of 77.35%

The figure below shows the value measured by another control board UVLO=1.373V DUTY=78.128%

The figure below is to adjust the UVLO of the control board to 1.253V to obtain the maximum DUTY 78.13%

Thanks and best regards,

Jamie

  • 0
    TI__Mastermind 31580 points

    Hi Jamie,

    The datasheet only specifies a typical value of 80%, in practice this lowest value value can be as low as 71%.

    I would suggest that your customer change the transformer turns ratio in the design to allow for this lower value of duty cycle at the 9Vin input level.

    Regards

    Peter