2 differents voltage level in 1 complete duty cycle of PWM

Thread Starter


Joined May 5, 2008
Dear All,

im trying to design a system whereby to open a valve using PWM. The only problem with this system is that, it require 2 different voltage levels with the same amount of duty cycle of the PWM. Here i attach as in the diagram below; The valve require 12v to open and remain to open it require just 3v. Can anyone please advise on how can i implement this. i know quite well on how to implement PWM either programmable or analog device but not with 2 voltage in single duty cycle. Please let me know if this is possible. thanks :confused:



Joined Jul 17, 2007
What's your supply voltage?

I think you're really making this more complicated than you need to.

If your supply is 12v, you simply need to provide 100% duty cycle until the valve opens; then around 25%-35% duty cycle to keep the valve open. Use a flywheel diode across the valve's solenoid to provide a current path for when the PWM supply is off.