Boost converter Design spreadsheet error ?

Discussion in 'General Electronics Chat' started by freefireant, Mar 16, 2016.

  1. freefireant

    Thread Starter New Member

    Mar 15, 2016
    11
    0
    Hi all,

    Very new at designing switching power supplies so please be kind !

    I am using the spreadsheet http://www.onsemi.com/PowerSolutions/supportDoc.do?type=tools&category=981
    NCL1608 Design Worksheet.

    When I put in Target Output Voltage Vout=155 (which is the voltage I want out of the curcuit.

    It gives

    MAX Calculated Inductor Value L(MAX)_C =-11450

    Can you please explain why this is a negative value ?






     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    Hello and welcome to the forum.

    If you just enter an output voltage that is lower than the input voltage for a step up converter, you will get bad numbers out. Enter all of your parameters.
     
    freefireant likes this.
  3. freefireant

    Thread Starter New Member

    Mar 15, 2016
    11
    0
    Hi Lestraveled,
    Thanks for your super quick reply.

    The design has to be able to run on 115vac and 240vac.

    Soooo.... if that is the case I need to just use a voltage divider to get the voltage I want ?
    Or is there a better way ?

    Cheers,

    Phill
     
  4. freefireant

    Thread Starter New Member

    Mar 15, 2016
    11
    0
    I was thinking of a capacitor divider. ?

    Or a tapped transformer before the rectifier that is at a lower voltage than the 155v output I need ?

    Any help at all much appreciated.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,544
    1,251
    90 Vac (from your other thread) = 127 Vp. 240 Vac = 340 Vp. Because 155 V is in between, it sounds like you want a system that will switch automatically between boost and buck as needed. One approach is a tapped transformer, with switching controlled by a voltage monitor circuit (or a simple physical switch). Another approach is all electronic and is called ... wait for it ... a buck/boost circuit. Linear Technology makes control chips for this, but they are intended to more common low voltages.

    What is this for? Is a custom transformer an option? Is a voltage adjust switch an option, or is automatic self-adjusting required?

    ak
     
  6. freefireant

    Thread Starter New Member

    Mar 15, 2016
    11
    0
    Hi AK and thanks for your reply.
    Buck/Boost is what I am looking for ! .. did not even know they made this kind of thing.
    This is to supply a lot of nixie tubes I am making a clock and need 60 tubes drawing 12ma each at 155vdc on the anode.
    Transformer is out because of regulation issues.
    I would prefer it to be automatic adjustment as I want to be able to run off 110vac or 240vac But I guess a switch would be fine also, like in older cheaper ATX power supplies.
     
Loading...