# 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
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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
1,217
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
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Hi Lestraveled,

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
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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
4,685
1,297
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

Mar 15, 2016
11
0