LLC resonant converter

Hi Aradhyasambhu,

The efficiency of a diode bridge rectifier depends on the rectified voltage, rms currents, etc. Diode bridge rectifier losses are not the same for every design and therefore the efficiency will vary depending on the design. Which design are you referring to?

Best Regards,

Ben Lough

Hi Ben,

I am referring to diode bridge rectifier at the secondary side of LLC converter. 

Hi Ben,

As per the data sheet of UCC25640EVM, the output power is 180 W with a DC output voltage of 12 V. 

This indicates the average output current would be then (180/12) = 15 A.

Assuming the average current flowing through output filter capacitor is negligible, the average current through each diode will be 7.5 A. 

In that case the total power loss would be = 4*7.5*0.5 = 15 W (Min. loss)

Please correct me if I am wrong. 

HI Ben,

In case of LLC converter, the output current is also sinusoidal. The average output current from the full wave rectifier is equal to (2*Im/Pi) and the average current through each diode is (Im/Pi). 

Hi Ben,

As per the design procedure mentioned in the UCC256404 datasheet, the secondary side is connected to a center tapped full bridge rectifier and the diode currents are assumed with an 110 % overload condition. 

The average output current is 15 A. Considering an overload factor of 110 %, the current becomes 16.5 A.

So 16.5 A is (2*sqrt(2)*Is/Pi), where Is is the secondary rms current. 

Hence the diode current is sqrt(2)*Is/Pi = 8.25 A. 

As the configuration is center tapped, so two diodes (with a forward drop of 0.5 V).

Power loss in the present case = 2*0.5*8.25 = 8.25 W. 

My calculation is based on assuming the configuration to be a full wave rectifier without a center tap transformer with 4 diodes. 

Assuming the same diodes i:e a forward drop voltage of 0.5 V, the power loss will be 4*0.5*8.25 = 16.5 W.