TPS54335A: Switching loss equation

K.Hamamoto

Guru 12155 points

Part Number: TPS54335A

I have a question about the switching loss on the datasheet.

It is shown as bellow,

I think the switching loss is shown "Ploss = 1/2 * Vin * Iout * (Tr+Tf) * Fsw"

"10^-9" may be (Tr+Tf). I do not understand why "Vin^2" in equation (31) is included. Is that "Vin"?

Best Regards,

Koji Hamamoto

over 7 years ago

0 Shawn Nie over 7 years ago

TI__Genius 10070 points

Hi Koji,

10^(-9) is the sum of 1/SR_rising and 1/SR_falling, that is to say, 10^(-9)*Vin=(1/SR_rising + 1/SR_falling)*Vin=Tr+Tf, this is the rough estimation.

Best Regards,
Shawn Nie

0 K.Hamamoto over 7 years ago in reply to Shawn Nie

Guru 12155 points

Hi Shawn-san,

That is Slew Rate! I understood.

On the other hands, "10^-9 * Vin" is the rough estimation as you mentioned above.
Can we use this estimation(as for Tr/Tf) for other device?
(I understand this value is for the rough estimation only.)

Best Regards,
Koji Hamamoto

0 Shawn Nie over 7 years ago in reply to K.Hamamoto

TI__Genius 10070 points

Hi Koji,

For different devices, the slew rate is different, so the error depends on SR of the device, if you use 10^-9 for other device, I don't know whether you can accept this error.

Best Regards,
Shawn Nie

0 K.Hamamoto over 7 years ago in reply to Shawn Nie

Guru 12155 points

Hi Shawn,

Thank you ! I understood. (I do not use the value for other device.)

Best Regards,
Koji Hamamoto

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TPS54335A: Switching loss equation