# BOOST Converter Problems

Discussion in 'General Electronics Chat' started by crazyengineer, Jul 18, 2012.

1. ### crazyengineer Thread Starter Member

Dec 29, 2010
156
2
Hello everyone! I'm trying to implement a Boost converter that can convert 5v to 15v and output 1a. I did the calculations but, when I ran PSPICE simulations, it's no where near what I predicted. I was wondering if anyone knows what am I missing when selecting the MOSFET for boost converter?

Calculations:
V_g=5;
V_o=15;
I_o=1;
fs=10e3;

D =1-(V_g/V_o)=

666.6667e-003

I_L =I_o/(1-D)=

1.5000e+000

i_l =.1*I_L=

150.0000e-003

L =(V_g*D)/(i_l*fs)=

2.2222e-003

v_o ==.1*V_o=

1.5000e+000

C =(I_L-I_o)*(1-D)/(fs*v_o)=

22.2222e-006

R =

30.0000e+000

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
The graph time scale isn't clear - 100nsec...???

Perhaps you need to run the simulation over a much longer period - say 20 milli-seconds. You may need to tweak the Duty to achieve the required average output of 15V DC.

My sim runs OK for the schematic - although using a 1N4148 diode is probably not appropriate being that it would be carrying much more than its rating mean current. Something with a bit more current carrying capability would make sense.

3. ### crazyengineer Thread Starter Member

Dec 29, 2010
156
2
It's 100ms.

where in the datasheet for the 1N4148 talks about the mean current http://www.nxp.com/documents/data_sheet/1N4148_1N4448.pdf ?

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Re the data sheet - see page 3 "Limiting Values" - IF - Continuous forward current - 200mA.

So are you driving the Mosfet with a periodic pulse train rather than a single pulse?

It's probably a matter of image integrity but the schematic looks as if the drain and source of M3 aren't connected to anything.

As I said the simulation I ran with my software worked just fine - albeit with some different devices. I don't have your Mosfet part no. in my library [SIMetrix] and I used another diode type - although I don't think that would matter for the purposes of simulation.

What software are you using? If you post the source file someone may be able to check it if they have the same application installed.