I'd like to design a PWM with a sawtooth wave output, the on time being half the off time with variable output. Would anybody have any ideas on how to accomplish this?

Thanks

 

Hello,

You could do this with a triggerable sawtooth generator, like the ones used in an oscilloscope.

Greetings,
Bertus

 

Maybe Something like these???

 

Hello,

The right one from the first dwawing, you can convert to a one shot.
This can be done by taking pin 2 free and give startpulses on it.

Greetings,
Bertus

 

Or better yet, what about this?

 

Do you mean a waveform like this? This is the result of a simulation of a circuit I designed.

 

Do you mean a waveform like this? This is the result of a simulation of a circuit I designed.

Yes, this is what I was initially looking for, but thought that the capacitive charge curve would be the kindest for the purposes of charging a 1,5V battery with a PWM scheme.

 

yes, can i do this using a 555 timer ic???...

 

Pin 5 on a 555 is a neat VCO input if look at correctly, then work from there. Something like the function generator I was working on only using pin 5 as a input.

http://forum.allaboutcircuits.com/showthread.php?t=12405

There would be some interesting problems though, amplitude change is one of them.