I need to design a circuit which generates a PWM signal from DC voltage with adjustable duty cycle. The thing is I can't use the 555timer according to rules. The frequency is not important but it must not change with changing the duty cycle.
Creating PWM Signal with different Duty cycles using Opamp
- Thread starter Fatih Çalış
- Start date
Actually it is a homework project of the circuit course. In the project we are supposed to design a circuit which measure the temperature and compare it with the desired temperature and starts to run fan or heater. We are supposed to enter the desired temperature with a square waveform with different duty cycles, like D=%50 corresponds to 0C', while D=%0 corresponds -50C' and D=%100 corresponds to 50C' but I have problems to obtain different duty cycles
One way is to generate a fixed-frequency triangle wave, which can be done with a square-wave circuit driving an opamp integrator to get the triangle signal.
This can be done with two opamps in a feedback loop, with the triangle wave output going to a comparator (with hysteresis) to generate the square-wave (which is fed back to the integrator input).
The triangle output also goes to one input of another comparator.
The temperature signal goes to the other comparator input.
The output of this comparator is thus a square-wave with duty-cycle proportional to the signal voltage.
I'll leave the details as a exercise for the reader.
This can be done with two opamps in a feedback loop, with the triangle wave output going to a comparator (with hysteresis) to generate the square-wave (which is fed back to the integrator input).
The triangle output also goes to one input of another comparator.
The temperature signal goes to the other comparator input.
The output of this comparator is thus a square-wave with duty-cycle proportional to the signal voltage.
I'll leave the details as a exercise for the reader.
Last edited:
(me speechless)One way is to generate a fixed-frequency triangle wave, which can be done with a square-wave circuit driving an opamp integrator to get the triangle signal.
This can be done with two opamps in a feedback loop, with the triangle wave output going to a comparator (with hysteresis) to generate the square-wave (which is fed back to the integrator input).
The triangle output also goes to one input of another comparator.
The temperature signal goes to the other comparator input.
The output of this comparator is thus a square-wave with duty-cycle proportional to the signal voltage.
I'll leave the details as a exercise for the reader.
This, Right There, explains why uC are so darn popular.
And that somehow surprises you?
LEDs, 555s, Flashers, and Light Chasers
Tyere are ltsofways to make a reiangle withoutusibg a555
Tyere are ltsofways to make a reiangle withoutusibg a555
