UCC28070: Icout calculation for slua479b application note

Satoshi

Guru 19645 points

Part Number: UCC28070

Question about slua479b application note(attached below), Page-5 equation (15).

Icout_hf become minus current on the condition of Pout: 3300W, Vin_min: 180V, Vout:390V.

(Icout_lf is 6.83A by equation (14))

When above case, which UCC28070 operation ① or ②?

①Actually, Icout_hf flow 0A current.

②Icout_hf should not become minus current, this is no recommended condition.

　⇒If correct is ②, please let me know operation principle.

Best regards,

Satoshi

over 7 years ago

0 John Griffin1 over 7 years ago

TI__Mastermind 34465 points

Hello Satoshi-san,
It look like this is an error in the SLUA479B document.
Please use the equation 49 in the UCC28070 datasheet to calculate the low frequency capacitor ripple.
I will check with the original systems engineer at TI and see if we have an equation for calculating the high frequency ripple.
Thank you for pointing out this error.
Regards
John

0 Satoshi over 7 years ago in reply to John Griffin1

Guru 19645 points

John-san

Thank you for reply,
I looking forward any update.

Addition, UCC28070 design tool(sluc114) is also using error equation.
Is there revision schedule for sluc114?

Best regards,
Satoshi

0 John Griffin1 over 7 years ago in reply to Satoshi

TI__Mastermind 34465 points

Hello Satoshi-san,
The equation is only valid for a universal 85Vac to 265Vac input.
That is one reason the calculator tool (SLUC114) locks the input voltage.
For a non-universal input voltage I was able to find this document :
e2e.ti.com/.../predicting-output-capacitor-ripple-in-a-ccm-boost-pfc-circuit
and it shows how a valid method of calculating the ripple current for a 180Vac min line as in your application.

I cannot say how long it will take for the changes to be published. That process involves many tasks that are beyond my control.
Regards
John

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UCC28070: Icout calculation for slua479b application note