TL494 duty cycle control help!

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Manmash

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I'm using TL494 to generate PWM. the max duty cycle is 45% and i need 20% which i am struggling to obtain (datasheet is attached) .... according to the datasheet, I understood that The duty cycle can be controlled by adjusting the voltage on the feedback pin(3) ..... I keep getting the same output 5v, no matter what the voltage at pin 3 is ... wat am I doing wrong??

Any help is highly appreciated .............

MOD: Your attchment was the device datasheet which is found freely on the net. Do not upload anything what you get on the net. Instead a link to the file if mandatory is sufficient. Read rules / announcemnets to avaoid warnings.
 

Manmash said:
... wat am I doing wrong?? Any help is highly appreciated .............
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Instead expecting members look at the device datasheet, you may upload your schematic where the PWM is implimented and expect better responses.
 
If you want to control duty cycle, you must disconnect the feedback loop. Just use open loop configure.
 
One way to control dead time with tl494 is adjust the voltage going to the dtc pin(pin 4). 0v/Gnd on pin 4 is 45% duty and +3.3~+3.35 is 0% duty. The duty cycle is fairly linear in between 0 to 3.35 so some where in the middle of those is 20%. I use the dtc pin for over current and remote turn on so I can use both error amps for other stuff. A simple 10k pot divider network attached to pin 4 and using gnd and vref will get you a good stable adjustable duty cycle.
 

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