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Need Buck Converter with 100% Duty Cycle

SUMIT RANJAN
Expert 2005 points
Other Parts Discussed in Thread: TPS40170

Hi Team,

I am looking for Buck converter for output of 12V@5A with 100% Duty Cycle feature.  My Input voltage will have range of 12VDC~50VDC.

Reason behind to looking for 100% Duty cycle is lower value of input range that is 12VDC. I am okay to get output with drop voltage across RDS and due to inductor resistance at 100% Duty cycle because .

with output of 12VDC we are generating 4.5V, 3.3V, 1.1V etc so we dont have issue if output of buck converter will be less than 12V.

So, based on this please suggest Buck converter.

Requirement:

1) output of 12V@5A

2) Input voltage range 12VDC~50VDC

3)  Feature with 100% Duty Cycle

  • 0
    TI__Mastermind 31580 points
    Hi Sumit,

    Since this is a non-isolated application I will move your post to that forum. Just to let you know that we dont have any general purpose PWM controllers that can produce 100% duty cycle.

    Regards

    Peter
  • 0
    TI__Mastermind 24075 points

    Hi Summit,

    If 12V Vout will be used to genenrate 4.5V, 3.3V, 1.2V and etc, I don't think the buck connverter needs 100% duty cycle.

    Assume the maximum duty circle of buck converter is 85% ducy circle, with 12Vin, the output can be up to around 10V.

    10V is high enough to genenrate 4.5V and etc.

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Expert 2005 points

    HI Qian,

    Thanks for update. Can you please let  me know how can i  calculate output voltage considering duty cycle. ?

    Please share any application note or document if you have.

    Also, share part number with 85%duty cycle.

  • 0 in reply to SUMIT RANJAN
    TI__Mastermind 24075 points

    HI Sumit,

    The Vout of buck concerter can be roughly calculated as Vin*D, where D is the duty circle.

    To get some margin, I think you can convert 12V-50V to around 9V, then use 9V to generate other low voltages.

    TPS40170 can be used to convert 12V-50V to 9V. You can also use Webench design on www.ti.com to select other controller.

    Btw, I'm not supporting TPS40170 and other single phase controler, please submit a new post if you have any question on particular controller.

    Thanks

    Qian

    Under the hood of low-voltage dc-dc converters.pdf

  • 0 in reply to Qian Chen
    Expert 2005 points
    Hi Qian,

    Thanks and understood about output voltage and duty cycle relationship.
    I can not use 9V option because i have to do oring with another 12V which will be generated by POE++. So i can design for 12V but if input will be less then output voltage will be less. Regarding oring with 12V i will think on this.