File:Three PWM types.png

Summary

Three methods to generate an intersective pwm: leading edge modulation, trailing edge modulation or centered modulation. The reference signal is a sine wave, not plotted. See Image:Pwm.svg for more information.

Created in maxima using the following code.

trailsignal(t) := t - floor(t); leadsignal(t) := ceiling(t)-t; centersignal(t) := 2*abs(t-floor(t-1/2)-1); freq : 0.05; sinesignal(t) := (1/2) + (499/1000)*sin(2*%pi*freq*t); pwmlead(t) := (if(leadsignal(t) > sinesignal(t)) then 0.0 else 1.0); pwmtrail(t) := (if(trailsignal(t) > sinesignal(t)) then 0.0 else 1.0); pwmcenter(t) := (if(centersignal(t) > sinesignal(t)) then 0.0 else 1.0); load(draw); draw(terminal=svg,file_name="Three_PWM_types",

   gr2d(yrange=[-0.25,1.25],nticks=20,grid=true,
       user_preamble="set mxtics;set format x "";
            set origin 0,0.67; set size 1,.3;set bmargin 0; 
            set tmargin 0",font="Times",
       ylabel="lead",ytics={0,1},axis_bottom=false,
       color=green,explicit(leadsignal(x),x,0,19),
       color=blue,explicit(pwmlead(x),x,0,19)),
   gr2d(yrange=[-0.25,1.25],nticks=20,grid=true,
       user_preamble="set mxtics;set format x "";
            set origin 0,0.37",font="Times",
       ylabel="trail",ytics={0,1},axis_bottom=false,
       color=green,explicit(trailsignal(x),x,0,19),
       color=blue,explicit(pwmtrail(x),x,0,19)),
   gr2d(yrange=[-0.25,1.25],nticks=20,grid=true,
       user_preamble="set mxtics;set format x "%1.0f T";
            set origin 0,.07",font="Times",
       ylabel="center",ytics={0,1},
       color=green,explicit(centersignal(x),x,0,19),
       color=blue,explicit(pwmcenter(x),x,0,19))
   );

Author Three_types.png: Cyril BUTTAY derivative work: Krishnavedala (talk)

Licensing

This work is licensed under the Creative Commons Attribution-ShareAlike 2.5 License. https://creativecommons.org/licenses/by-sa/2.5/CC-BY-SA-2.5Creative Commons Attribution-ShareAlike 2.5truetrue