TPS62147: Inductor ripple current: Equation(12)

Shota Mago

Part Number: TPS62147

Hi team,

My customer will use TPS62147 and he is asking question. As for equation(12), what does "100ns(2.5MHz)/200ns(1.25MHz)" mean?

It looks like on time. But it should be equation(1) or (2). Why100ns/200ns(25% of duty cycle) are used for equation of inductor current ripple?

Best regards,

Shota Mago

over 3 years ago

0 Shuai Fan over 3 years ago

TI__Genius 13451 points

Our team will reply you next Monday!

sHUAI

0 Nancy Zhang over 3 years ago in reply to Shuai Fan

TI__Mastermind 49370 points

Hi Shota,

The equation 12 is derived from equation 3 and 4. 100ns/200ns is not regular on time and the regular on-time are from equation 3 and 4. 100/200 are internal parameters to adjust on time in power save mode depending on input voltage and output voltage to maintain highest efficiency. This is for AEE feature(Automatic efficiency enhancement).

Hope this helps,

Thanks,

Nancy

0 Shota Mago over 3 years ago in reply to Nancy Zhang

TI__Expert 8110 points

Hi Nancy,

Thanks for your reply.

Nancy Zhang said:
100/200 are internal parameters to adjust on time in power save mode

If the device works in Forced PWM mode, equation 12 doesn't apply, right? Also, even if the device works in PFM/PWM mode, it works in PWM(CCM) mode around max output current for many application. The purpose of equation 12 is to estimate current rating of inductor. But why ripple current equation of power save mode is used?

Best regards,

Shota Mago

0 Shuai Fan over 3 years ago in reply to Shota Mago

TI__Genius 13451 points

Hi Shota!

Nancy will reply you tomorrow!

Shuai

+1 Nancy Zhang over 3 years ago in reply to Shuai Fan

TI__Mastermind 49370 points

Shota,

Yes, you are right. For forced PWM mode, equation 12 doesn't apply. You can use regular ripple current equation to estimate inductor ripple current.

The purpose of equation 12 is to estimate the max current rating of inductor. Because AEE feature lowers the switching frequency to increase efficiency, so the inductor ripple current may increase. That is why this equation is used since most customer used AEE feature. Please refer to below link for more detail for AEE feature.

AEE Boosts Efficiency for Lower-Output-Voltage Step-Down Converters | Electronic Design

Hope this helps,

Thanks,

Nancy

0 Shota Mago over 3 years ago in reply to Nancy Zhang

TI__Expert 8110 points

Hi Nancy,

I understood, Thanks for clarification!

Best regards,

Shota Mago

Power management

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TPS62147: Inductor ripple current: Equation(12)