Help me with designing duty cycle detector

[RollingEEE]

A duty cycle detector

Hi,

I need a design of an opamp based circuit that takes a PWM signal in, and outputs a voltage, that is proportional to the duty cycle of the inputsignal.

Please help me

 

[E-design]

Re: A duty cycle detector

Integrate the ON part, scale and calibrate

 

[RollingEEE]

Re: A duty cycle detector

nice idea. can you please explain how it works?

 

[E-design]

Re: A duty cycle detector

To provide more information you need to tell more about the application.
Is the frequency fixed?
What will be the max frequency you intend to use?
What type of indication you require. Analog or digital?

 

[hung_wai_ming@hotmail.com]

A duty cycle detector

Typically, what E-design says might be input the signal to the Op-Amp and integrate on a capacitor, with a voltage ratio proportional to the H to L duty cycle, then you can get the result. However, it depends on the input frequency that the Op-Amp can respond and the current it can deliver to the cap that have. Basically, the cap should be large enough to reject the ripples it generate from the switching

 

[RollingEEE]

Re: A duty cycle detector

hi,

I want to make a phase shift detector. I first used 2 level crossing detectors, then used a comparator.

The resultant wave was a PWM output the duty cycle was proportional to the phase shift.

Using the half wave rectifier yields:

Now I need to convert this into something DC. Can any one help me

Added after 9 minutes:

the RC filter gives a regulated DC output but I am not sure if it is linear with pulse width