distortion of SW CAD III

SkyChu · 14th June 2004, 01:45 AM

I'm trying to simulate circuit by LTC SWCAD III . But the 3rd (Odd)distortion of input voltage source is too high when I use FFT simluation (V1, see attached files). the transient is ".tran 0 15m 1m 0.1u".
How can I reduce the distortion ?

SkyChu · 14th June 2004, 01:48 AM

The FFT:

jcx · 14th June 2004, 03:51 PM

have you turned off compression? expecting long sims of switching power regulator circuits LtSpice compresses the sim output data files by default - Tools>Control Panel>Compression - clik off all the boxes every time you open LtSpice

more recent versions accept a spice directive:

.options plotwinsize=0

in the fft menu i increase length to 131072 and use the Blackman window, keep averaging low or off(=1) since it is a digital low pass filter appiled to your data - i think mine defaults to 5

DarkOne · 14th June 2004, 04:15 PM

You have feedback attached only to "negative" half of the circuit

SkyChu · 14th June 2004, 06:17 PM

Thanks Jcx ! It can work !

SkyChu · 14th June 2004, 06:30 PM

Quote:

Originally posted by DarkOne
You have feedback attached only to "negative" half of the circuit

Yes ! Is it "feedback" ? !

thanh · 19th June 2004, 08:11 AM

Quote:

You have feedback attached only to "negative" half of the circuit

Ok! I have a agreement with Darkone
Skychu! you have to feedback attached only to "negaitve" half of the circuit

14th June 2004, 06:17 PM	#5
SkyChu diyAudio Member Join Date: May 2002 Location: Taiwan	Thanks Jcx ! It can work ! __________________ Sky Chu

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14th June 2004, 03:51 PM	#3
jcx diyAudio Member Join Date: Feb 2003 Location: ..	have you turned off compression? expecting long sims of switching power regulator circuits LtSpice compresses the sim output data files by default - Tools>Control Panel>Compression - clik off all the boxes every time you open LtSpice more recent versions accept a spice directive: .options plotwinsize=0 in the fft menu i increase length to 131072 and use the Blackman window, keep averaging low or off(=1) since it is a digital low pass filter appiled to your data - i think mine defaults to 5

14th June 2004, 04:15 PM	#4
DarkOne diyAudio Member Join Date: Oct 2001 Location: Bratislava	You have feedback attached only to "negative" half of the circuit