eem2am1
Junior Member level 1
Hello,
I notice that in the very thin , flat-panel TV’s that the back-light SMPS (even when only at 50 Watts) is being done with an LLC resonant converter, rather than a dual-phase flyback.
-The dual phase flyback would be just as efficient as the LLC resonant converter, and cost less overall……also, the dual phase flyback gives better LED current regulation right down to low LED currents, if used as a single stage to regulate the LED current.
So, do you know why LLC resonant converters are favoured above dual-phase flybacks in such cases?………….
……..….it is after all, rare to hear of a bridge converter being used for just 50W.
…one theory is that in the new , very thin profile, flat-panel TVs, the SMPS transformer would have to be very flat (obviously).
-and very flat transformers tend to have very short bobbin spindle lengths…which in turn means that they end up having a high leakage inductance………..
-and it is the high leakage inductance in the transformer that favours LLC resonant converter above flyback converters……….
-because you can “integrate” the transformer leakage inductance usefully into the LLC converter’s transformer……………whereas leakage inductance is never useful in a flyback.
So is this correct?…………………
Do short-spindle bobbin transformers give overly high leakage inductance?
I notice that in the very thin , flat-panel TV’s that the back-light SMPS (even when only at 50 Watts) is being done with an LLC resonant converter, rather than a dual-phase flyback.
-The dual phase flyback would be just as efficient as the LLC resonant converter, and cost less overall……also, the dual phase flyback gives better LED current regulation right down to low LED currents, if used as a single stage to regulate the LED current.
So, do you know why LLC resonant converters are favoured above dual-phase flybacks in such cases?………….
……..….it is after all, rare to hear of a bridge converter being used for just 50W.
…one theory is that in the new , very thin profile, flat-panel TVs, the SMPS transformer would have to be very flat (obviously).
-and very flat transformers tend to have very short bobbin spindle lengths…which in turn means that they end up having a high leakage inductance………..
-and it is the high leakage inductance in the transformer that favours LLC resonant converter above flyback converters……….
-because you can “integrate” the transformer leakage inductance usefully into the LLC converter’s transformer……………whereas leakage inductance is never useful in a flyback.
So is this correct?…………………
Do short-spindle bobbin transformers give overly high leakage inductance?