UCC28740-Q1: Light-load efficiency

Cheng Zhang

Part Number: UCC28740-Q1
Other Parts Discussed in Thread: UCC28740

Tool/software:

HI team,

A quick question on UCC28740, the Vin is 800V/400V DC voltage, output is 10V/2mA very light load, what's the input current for 400V and 800V respectively?

What's the efficiency?

Thanks

over 1 year ago

0 Manuel Alva Hernandez over 1 year ago

TI__Genius 15366 points

Cheng,

Efficiency will depend on your transformer efficiency, conduction losses through the main switch, switching losses through the main switch, stand-by losses. Please, see below a reference design using the UCC28740 controller with a ~80% efficiency. Once the efficiency is estimated, you can calculate your DC input current with the equation Vout*Iload/(efficiency*Vin_DC).

UCC28740EVM-525 Evaluation board | TI.com

Thank you

0 Cheng Zhang over 1 year ago in reply to Manuel Alva Hernandez

Prodigy 120 points

Could you help me the estimated efficiency? Let's say 400V input, 5V output/ 5mA load

What's the estimated input current?

Thanks

0 Manuel Alva Hernandez over 1 year ago in reply to Cheng Zhang

TI__Genius 15366 points

Cheng,

As I mentioned the efficiency will vary depending on the design of your transformer and the selection of your main switch FET. Just as an example, considering an 80% efficiency and Vin_DC=400V, Vout=5V, Iload=5mA then Iin_DC=Vout*Iload/(efficiency*VIN_DC)=78.1uA. This is a very low input current because the load is very low (Iload).

Thank you

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UCC28740-Q1: Light-load efficiency