TL494 duty cycle adjustment
When in doubt, resort to the datasheet, specifically page 8:

As you can see, they tied all the inputs of the error amplifiers to ground, and then used the DTC and the FEEDBACK pins for testing, which is shown below, in the datasheet, as waveforms. However, as mentioned in the comments, it's a rather convoluted way of getting a PWM, unless you already had the chip at hand (or want to go further with the design) -- otherwise the classic comparator with ramp input would make a better choice.