UCC28951-Q1: UCC28951-Q1

Hello Rajashekar

The energy needed to drive the ZVS transition on the 'Left Hand' or 'Passive/Active' leg of the bridge (QA and QB in the Simplified Application Diagram in the UCC28951-Q1 datasheet ) is supplied by the leakage inductance of the transformer primary. Sometimes the transformer leakage inductance is not enough so we have to add an extra inductor in series with the transformer. This extra inductor is called the shim inductor. If for example you need 50uH of inductance to drive the ZVS transition and the transformer has 20uH of leakage inductance then you need a 30uH shim inductor.

The energy to drive the ZVS transition on the 'Right Hand' or 'Active/Passive' leg of the bridge (QC and QB) is supplied by the energy in the leakage+shim inductor plus that in the transformer magnetizing inductance and output inductor so it is much easier to achieve ZVS on the Active/Passive leg than on the Passive/Active leg.

/cfs-file/__key/communityserver-discussions-components-files/196/_7E002400_at-is-the-function-of-the-shim-inductor-and-clamp-diodes-in-the-primary-circuit.docx

Please let me know if you need more information

Regards

Colin

Colin