Multiple Output SEPIC Converter

Hey,

I'm attempting to design a SEPIC converter using the ADP1621 IC. I am currently in the early stages of development of this project and I thought I would see if anyone has attempted anything like this before, and if so have they run into any difficulties. The parameters I am working with are outlined below:

Vin = 9Vdc to 14Vdc (conceivably up to 17Vdc depending on application)

Vout1 =5.5Vdc

Vout2 =10.5Vdc

Iout1 = 200mA

Iout2 = 650mA

Max Switch Freq = 650 kHz

I would like to 1 magnetic package to achieve this goal (currently waiting on qoutes for custom magnetics), so 1 primary inductor coupled with 2 secondary inductors. The idea would be deriving the control voltage from one of the outputs and allow the coupling of the second magnetic to determine the voltage of the second output. The output of both outputs will be going through LDOs so if the output on the un monitored output would be regulated down.

Regards,

Pete P

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  • 0
    •  Analog Employees 
    on Jan 26, 2012 10:45 PM

    Hi Pete,

    You wrote:  "That was my first attempt which led me to the forum. Unfortunetly that  tool specs that the lower voltage is limited to 90% of the highest."

    If that is indeed the case then you are using the wrong tool.  You are probably using the ADP1621 boost tool, rather than the SEPIC.  If you had plugged in your specs into SImpower you would have come up with the correct ADP1621 Coupled SEPIC tool.  I have attached the correct tool for your application.

    It occurred to me last night that you should probably use 2 coupled inductors rather 3 discreet inductors to test your circuit idea because otherwise you will end up with some resonances that are hard to deal with that will go away when you use coupled inductors.

    Regards,

    Kevin

    ADP1621_CoupledSEPIC_Designer_1_13_12_release.xls
Reply
  • 0
    •  Analog Employees 
    on Jan 26, 2012 10:45 PM

    Hi Pete,

    You wrote:  "That was my first attempt which led me to the forum. Unfortunetly that  tool specs that the lower voltage is limited to 90% of the highest."

    If that is indeed the case then you are using the wrong tool.  You are probably using the ADP1621 boost tool, rather than the SEPIC.  If you had plugged in your specs into SImpower you would have come up with the correct ADP1621 Coupled SEPIC tool.  I have attached the correct tool for your application.

    It occurred to me last night that you should probably use 2 coupled inductors rather 3 discreet inductors to test your circuit idea because otherwise you will end up with some resonances that are hard to deal with that will go away when you use coupled inductors.

    Regards,

    Kevin

    ADP1621_CoupledSEPIC_Designer_1_13_12_release.xls
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