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Offline Full bridge SMPS control ic's do not have output overload protection?

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treez

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The following are the most common current mode full-bridge SMPS control chips in the world for 90-265VAC input SMPS’s….

UCC3808, LM5030, LM5037 , UC3846, LTC3721-1

None of these chips has output overload protection. By “output overload protection”, I mean that if the error amplifer internal to them is railed high for more than 1 second, then these chips do *not* latch off.

Most offline flyback smps chips have this facility, so why do none of the full-bridge smps chips have this?

LM5030
http://www.ti.com/lit/ds/symlink/lm5030.pdf

LM5037
**broken link removed**

LTC3721
http://cds.linear.com/docs/en/datasheet/37211fs.pdf

UCC3808
http://www.ti.com/lit/ds/symlink/ucc3808-2.pdf

UC3846
http://www.ti.com/lit/ds/symlink/uc3846.pdf
 

Correct, sometimes you want full power....!
 
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..Those chips can give full power. What we wonder is why no offline full-bridge controller has output overload protection, or output short circuit protection?
 

The features of the chip itself can be exploited in many unusual ways by a clever designer.

They all have some kind of current limit function, and the soft start pin can also be used as a duty cycle limiting feature quite independent of the normal current limit pin.

Its usual to provide a current limit for the switching devices, but there is no reason why an output current limit cannot also be fitted in addition to that,
 
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Thanks, here is our fault protection circuit, for use with these "unprotective" chips...
 

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