TPS61163AEVM-564: About efficiency deterioration.

watanabe

Hi,

When the voltage of JP2 (VIN) was increased from 2.8 V to 3.3 V,
The current of J1 (L1) increased, and efficiency got worse.
What is the cause?

Measurement condition,
J1 = 7.4V
JP2 = 3.3V
Iset = 51 kohm
LED = 10 series (*2 parallel)
PWM Duty = 100%

Best regards,

Watanabe

over 8 years ago

0 Angelos Tsiros over 8 years ago

TI__Intellectual 2140 points

Hi,

Conceptually, your observation is not consistent with what I would expect. Just to clarify, you are only measuring the current into the inductor, not the sum of the inductor and VIN currents? Can you provide the magnitude of the currents you are measuring? I will need to make some measurements and try to get an explanation for you.

Regards,

Angelos

0 watanabe over 8 years ago in reply to Angelos Tsiros

Expert 1740 points

Hi,

Thank you for your support.

The measurement results are listed below.

Measurement condition 1,
J1 = 7.4V
J1 = 0.219A
JP2 = 2.8V
JP2 = 0.00121A
VLED = 28.48V
Iset = 51 kohm(0.0248A)
PWM Duty = 100%

WJ1=7.4V×0.219A
WJP2=2.8V×0.00121A
WOUT=0.0248A×2ch×28.48V
Efficiency=WOUT÷(WJ1+WJP2)=87.06％

Measurement condition 2,
J1 = 7.4V
J1 = 0.228A
JP2 = 3.3V
JP2 = 0.00118A
VLED = 28.48V
Iset = 51 kohm(0.0248A)
PWM Duty = 100%

WJ1=7.4V×0.228A
WJP2=2.8V×0.00118A
WOUT=0.0248A×2ch×28.48V
Efficiency=WOUT÷(WJ1+WJP2)=83.6%

Best regards,
Watanabe

0 Angelos Tsiros over 8 years ago in reply to watanabe

TI__Intellectual 2140 points

Hi Watanabe,

I will try to duplicate your conditions and investigate the root cause for this behavior. I should have an update on Monday, January 16.

regards,
Angelos

0 watanabe over 8 years ago in reply to Angelos Tsiros

Expert 1740 points

Hi Angelos,

It was my measurement error.
We confirmed that efficiency will increase.

Please excuse my ignorance.

Best regards,
Watanabe

0 Angelos Tsiros over 8 years ago in reply to watanabe

TI__Intellectual 2140 points

Hi Watanabe,

Thank you for the update. I'm glad this has been resolved.

Best Regards,
Angelos

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TPS61163AEVM-564: About efficiency deterioration.