UC1825-SP: Fixed duty open loop push-pull

Hey Ottavio,

The EVM User's guide talks about how to generally design a push-pull, however the use case you are talking about is unique.

Most open loop, or at least primary side regulated devices are usually flyback converters.
Flyback converters are also popular at low currents, multiple output rails, and can save on having to use 2 switches.

Either way we do not have an application note on the subject.

Thanks,
Daniel

Hi Daniel,

thanks for your quick replay. Ok for Flyback, I already have one in the design.

For this application instead, if I stay on open loop push-pull, I have to validate the solution.

I will take this decision. Just one quick question before close the issue: 

I guess it's possible to roughly set a value of duty cycle on UC1825-SP if working in open loop. Is this correct ?

I was thinkig to set it at 40% roughly, just to have some margin against the maximum 50% in order not to incur in flux build up. 

Thanks, Ottavio

Hey Ottavio,

Its possible to set the value of the duty cycle but controlling the output of the error amplifier.
Figure 1 of this application note shows the behavior of they output duty cycle given a ramp and error signal:
https://www.ti.com/lit/an/snva555/snva555.pdf?ts=1730782861022

The duty cycle value will entirely depend on the ramp signal and output of the error amplifier.

Thanks,
Daniel

Welcome

Thanks,
Daniel