How does one go about making a variable duty cycle square wave in TINA TI?
For a fixed PWM frequency, one possible implementation is to have a triangle carrier being compared to an input reference as depicted in the figure below,
In SPICE the triangle wave can be implemented as an pulsed source with symmetrical rise/fall times and very short ( 0 s) duration. The input signal can be either DC or like in the example of the open loop class D shown above it can be a sine wave. I have attached a TINA test bench to get you started. Should you have any questions feel free to re-post.
Here is another way to create a variable duty cycle square wave using TINA-TI and the Controlled Source Wizard. The attached file has two inputs, a sine wave generator and a battery. The voltage values are compared and the output from the controlled source block is the square wave. You can set up the voltage sourec to be swept (as in this example and sweep the value to see the impact on the duty cycle.
You can also use the piecewise waveform input to set the duty cycle of the square wave and repeat the cycles.
I would like to ask a question related to this if you don't mind.
I want to see the frequency content of the output PWM signal. I tried to use the T & M -> Signal Analyzer.
But i guess this would not help, for
1. It tells me "Only one input is allowed"
2. I think this scope sweeps the circuit with frequency.
Actually, I just want to see the content of the signal at hand in frequency spectrum and not interested in a sweep.
Can you guys help me with this issue ?
Thanks a lot.
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