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TPS61291EVM-569: .

Tae Rim Park
Prodigy 85 points
Part Number: TPS61291EVM-569

Hello, TI,

I just bought and tested TPS61291EVM.

I found that the bypass mode was so good. It is quite close to the case without the boost converter. 

But, the efficiency of the boost mode is very disappointing.

I used several registers from 660K to 65K. Vin was 3.0V and Vout is set to 3.3V.

When the register was 660K, the efficiency was 35.65%. But it is OK since I'll use BYPASS mode in that case.

The efficiency was increased when I used smaller value registers.

But, when the register was changed from 300 to 65 ohm, the efficiency was decreased from 72.07 to 72.08 (current was 64mA).

Did I make something wrong? The datasheet shows the efficiency over 90% until current reach to 100mA.

Is there any way to improve the efficiency?

Thanks, 

  

  • 0
    TI__Mastermind 21565 points

    Hi Tae：

    Thanks for choosing TI part.

    May you show a picture of your test bench? Especially about the equipment's setup and connection. 

  • 0 in reply to Minqiu Xie
    Prodigy 85 points

    Hi Minqiu,

    I don't have the picture of whole environment.  

    But following picture is the device I made for the test.

    I made 3V input with my power supply. The current limit was 1A.

    The 3V is provided to the EVM through a multi-meter to measure current.   

    The values of chip registers are 660K, 297K, 100K, 60K, 30K, 3K, 300, and 65 ohm.

    The current using BYPASS mode were in uA,

    4.44 10.00 29.81 50.59 99.09 968.70 9897.00 45375.00

    The values were so good.

    The current using Boost mode (after the changing jumper in EVM) were

    12.70 20.02 46.04 73.45 137.83 1385.70 13215.00 64260.00

     

  • 0 in reply to Tae Rim Park
    TI__Mastermind 21565 points

    Hi Tea:

    Did you measure the Vin, Vout at sense pin？

    It doesn't make sense, if Vout=3.3V.  For example, 65 ohm.*64260.00uA=4.16V

  • 0 in reply to Minqiu Xie
    Prodigy 85 points

    Hi Minqiu,

    I know I also think that was quite strange.

    I just wondered I made some mistake. So, I did that again just before. 

    Here is my env. 

    I'm using Fluke multi meter to measure the current, and ITECH power supply.

    Before starting, I measured the resister value. It was 62.5ohm.

    Here is the results.

    Vout was 3.352V and current was 66.21mA.

    Vin is dropped to 2.851V.

    Can you tell me where my problem was?  

    Thanks,

    Taerim

  • 0 in reply to Tae Rim Park
    TI__Mastermind 21565 points

    Hi Taerim:

    Does the resistance value change with temperature? How about connect it with the DC supply with 66mA, and measure the voltage. 

    And how did you measure the input current? The efficiency should be Vout*Io/Vin/Iin, and it's recommended to measure these values at the same time.

  • 0 in reply to Minqiu Xie
    Prodigy 85 points

    Hi Minqiu,

    I guess temperature is not the issue.

    I connected like the following order.

    (1) Power supply -> (2) current meter --> (3) (Vin) 61291 EVM (Vout) --> (4) Load(registers).

    66mA means the displayed value in (2).

    I measured Vin, Vout, current at the same time (at least within 3 seconds).

    For me, efficiency is comparison of current consumption of two circuits, one is with booster the other is without that at the point of (2).

    The thing, I don't understand neither is that (3)Vout is 3.352. 

    Then, when I add the load of 62,5 ohm, in some place, some load is added in parallel.

    I can not find where. Is there any possibility that some parallel register is added in EVM? 

    Can you make the same condition in TI?

    Taerim 

  • 0 in reply to Tae Rim Park
    Prodigy 85 points

    HI Minqiu,

    Is it possible to email you directly? New design in my project is ready without this problem.

    The process discussing through this web takes time. 

    I guess I misunderstood and made something wrong while I'm using the booster.

    So, in this case, i think exchanging emails will be better to resolve this issue quickly. 

    After resolving the issue I can summarize the result in the web.

    My email address is taerimpark@ino-on.com.

    Thanks.

  • 0 in reply to Tae Rim Park
    TI__Mastermind 21565 points

    Hi  Taerim:

    It's glad to know that. I will contact you with email. Please allow me close this post for a easy maintain. 

  • 0 in reply to Minqiu Xie
    Prodigy 85 points

    Hi Minqiu,

    I really thank you for your response on this site and email.
    Today, I reviewed all my experiments and I found one big mistake. 
    I wanted to use similar power while boosting voltage.
    But, the load was fixed. That means higher voltage and higher current were derived by the booster. 
    If I compare the systems with and without the booster, the system with the booster uses more power  
    because I boosted up the voltage. 
    For the booster, in my exp. the efficiency was 94% it was excellent. 
    Vin and Iin were 3V and 64.26mA, respectively. Vout and R were 3.352V and 62 ohm.
    As a result, the efficiency was 181.22/192.78=94%.
    I'm not sure my real system consumes the same current on different input voltage, yet. 
    Currently, I have to boost up system voltage to 3.3V for wireless communication. 
    I hope my system finish work quickly or reduce current consumption 
    when it compared with the system without booster.
    Otherwise, now I understand I have the accept increased power consumption to provide
    the higher voltage. 
    Thank you, again.
    Taerim