Why is excellent SMPS feedback IC so rare?

[treez]

Hello

Why is their virtually no literature , or mention of this feedback ic?.....

UC3901:
https://www.ti.com/lit/ds/symlink/uc3901.pdf

..UC3901 drives a pulse transformer to transfer an error voltage (feedback signal) across the isolation boundary in an isolated SMPS.

Is it because people would just prefer to use a PWM controller IC instead, in its place?

 

[FoxyRick]

Is it because people would just prefer to use a PWM controller IC instead, in its place?

This chip does not replace the PWM controller, it replaces the feedback optocoupler only with the ability to use a small transformer in its place. Although it can also drive an optocoupler, presumably with improved characteristics.

I would guess it's not seen much because using an optocoupler is generally sufficient, cheaper and the circuitry is well established.

Interesting part though... makes me wonder if it has 'other' potential uses...

 

[treez]

sorry FoxyRick, i did not explain myself properly....i meant still using a pwm controller on the primary side, but using another pwm controller to literally drive the pulse transformer...........and due to its varying duty cycle it can transfer signal across boundary.

this is seen in book by raymond Mack...."demystifying smps"

 

[FvM]

Although this is an interesting part, most designers will probably question the advertising statement "Low-Cost Alternative to Optical Couplers" for general applications.

 

[mtwieg]

Optocouplers are usually the cheapest and simplest solution for isolated feedback (aside maybe from back EMF feedback for flybacks). In general you only go for other methods if you need extraordinary reliability (which seems to be one things cheap optocouplers can't offer), that's when you'd go for galvanic isolation. For those specific applications, this IC is probably a great convenience, but I'm surprised it's not well known because those specific cases aren't common.