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
    Hi all,

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

    I am using the spreadsheet
    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
    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
    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 ?


  4. freefireant

    Thread Starter New Member

    Mar 15, 2016
    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
    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?

  6. freefireant

    Thread Starter New Member

    Mar 15, 2016
    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.