TPA2011D1: Asking for the TPA2011 effiency measurement without inductor conditions

SHH

Part Number: TPA2011D1

Hi Team,

customer has question about TPA2011's efficiency measurement without inductor.
The efficiency that customer perform without 33uH is only 59%.

In TPA2011 d/s, efficiency is 88% under conditions 2W/4Ω +33uH, Vdd=5V.

Questions:
1. Do you think that loading RL=4Ω without 33uH inductor measurement can resulted in the lower efficiency?

2. Customer would like to know why efficiency is difference between RL=4Ω +33uH, RL=4Ω ??
Is that right to explain as below , could you please help to make sure whether it is right as below ?
Z=√(R²+X²)=√(4²+XL²)
XL=ωL=2πf*33uH=62.201Ω(f=300KHz)
∴Z=√(4²+62.2²)=8.84Ω
P=V²/R
If R(4Ω +33uH)= 8.84Ω is bigger than R=4Ω resistor
∴P (4Ω +33uH ) will be less than P(4Ω). So efficiency(4Ω +33uH ) is better than efficiency (4Ω)

Efficiency experiment
Condition as below Play -3dB sine wave , Vdd=5.12V ,Gain=3.14 ,R=4Ω (resistor)
1. Input signal voltage =0.707 Vrms , Gain=3.14
2. Output voltage =2.22Vrms
3. Output power= V²/R=2.22²/4ohm=1.23W (speaker)
4. Pin=V*I= 5.12V *0.407A=2.084W (when play -3dB sine wave ,TPA2011 input power )
5. Efficiency =1.23W/2.084W=0.59 =59%

Thanks,
SHH

over 7 years ago

0 José Luis over 7 years ago

TI__Mastermind 20085 points

Hi SHH,

1) I think so, the efficiency increases when the resistance is higher. You can refer the figure 1 and 2 of the amplifier's datasheet to observe this behavior.
2) The efficiency decreases with lower loads due to the power dissipation will increase.

Best Regards
José Luis Figueroa
Audio Applications Engineer

0 SHH over 7 years ago in reply to José Luis

TI__Mastermind 32206 points

Hi Jose,

Customer would like to know why TPA2011 power consumption is different between 4ohm resistor & 4ohm speaker. Could you please help to explain?

Could you also measure the 4ohm loading on TPA2011 to see the power consumption from your side base on the following conditions??

Vdd=5.12V ,Gain=3.14 ,R=4Ω (resistor)

Input signal voltage =0.707 Vrms , Gain=3.14

Output voltage =2.22Vrms

thanks,

SHH

0 SHH over 7 years ago in reply to SHH

TI__Mastermind 32206 points

Hi Jose,
Could you please help for the questions?

Thanks,
SHH

0 José Luis over 7 years ago in reply to SHH

TI__Mastermind 20085 points

Hi Scott,

I am waiting for the EVMs to make the test. I will be responding soon with further information.

Best Regards
José Luis Figueroa
Audio Applications Engineer

0 SHH over 7 years ago in reply to José Luis

TI__Mastermind 32206 points

Hi Jose,

Efficiency test condition is RL=4Ω+33uH and TPA2011 switching frequency is 300KHz.

Assuming figure 2 efficiency chart is playing 1KHz 0dB sine wave to measure, customer would like to know Z value of RL=4Ω+33uH , should customer input frequency with 1KHz or 300KHz??

Z=√(R²+X²)=√(4²+XL²)

XL=ωL=2πf*33uH=62.201Ω(f=300KHz)

∴Z=√(4²+62.2²)=8.84Ω

Thanks,

SHH

0 José Luis over 7 years ago in reply to SHH

TI__Mastermind 20085 points

Scott,

You should use the switching frequency F=300kHz in order to calculate the output impedance.

Best Regards
José Luis Figueroa
Audio Applications Engineer

0 SHH over 7 years ago in reply to José Luis

TI__Mastermind 32206 points

Hi Jose,
Thanks for help. Please kindly let me know the efficiency result once you have the EVM.

Thanks,
SHH

0 SHH over 7 years ago in reply to SHH

TI__Mastermind 32206 points

Hi Jose,
When will you receive the TPA2011 EVM for test?

Thanks,
SHH

0 José Luis over 7 years ago in reply to SHH

TI__Mastermind 20085 points

Scott,

I have received the EVM and made the test. I got an output voltage of 2.2 Vrms

Best Regards
José Luis Figueroa
Audio Applications Engineer

0 SHH over 7 years ago in reply to José Luis

TI__Mastermind 32206 points

Hi Jose,
Thanks for confirm.
What is the efficiency result from the customer's conditions? 59%?

Thanks,
Scott

0 José Luis over 7 years ago in reply to SHH

TI__Mastermind 20085 points

Scott,

Keep in mind that a speaker is used as the load for the filter-free class-D because it has the inductance that helps to provide the high class-D efficiency. A purely resistive load is not a true indicator of the operating environment of the filter-free class-D and does not provide accurate efficiency numbers.
You can refer the next application report: Guidelines for Measuring Audio Power Amplifier Performance to find further information about performing the measurements.

Best Regards
José Luis Figueroa
Audio Applications Engineer

Audio

Audio forum

TPA2011D1: Asking for the TPA2011 effiency measurement without inductor conditions