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TPS53015 Efficiency and Time Constant

Taha Akyol
Prodigy 20 points
Other Parts Discussed in Thread: TPS53015

Hi everyone,

I have built a buck converter using TPS53015. Input voltage is 24 Vdc, output voltage is set to 5 Vdc and desired maximum output current is 15 A.  However, the efficiency of the built system is approximately 77 % at full load. Obviously, it is very low and this number comes with serious heating problem as I use both passive and active cooling for the manufactured PCB.

When I look at the TPS4530015EVM-126; input :8-22V  output : 1.05 V  and output current: up to 8 A. In the user's guide, the efficiency  plot is given for different conditions and it is seen that the efficiency of the board is between approximately 84% -78%  at maxiumum load. After that observation,I started to think TPS53015 is not suitable for my operating point. Moreover ,it is stated that typical applications of TPS53015 is POL regualiton in Low-Power systems. Since Low-Power systems is not quantitativewhat do I understad from this phrase?  Can you give some quantitative explanation for Low-Power systems?

TPS53015 utilizes DCAP2 control method and in this method ripple injection is provided IC itself. From below document, it can be seen that ripple injection circuit  consists of a Time Constant bloack and compression block. Since I am not able to get experimental data plot of Bode-Plot, can I learn the Time-Constant of the TPS53015? http://www.ti.com/lit/an/slva546/slva546.pdf                            

I appreciate with your help.

Regards,

Taha AKYOL

  • 0
    TI__Guru**** 191445 points

    "low power" is a pretty general term, it depends on your context.  The front page of the datasheet is generally considered as "marketing material" and the terms used my be even more generic and in this case I think the bullet points are from English as second language author.  I normally consider low power to be maybe less than 5 W, see the TPS60k series of devices.  In this case, I think TPS53015 is generally targeted for 25 W or less.  I do not see a specific upper bound but it is limited by your external FET selection and the gate drive capability of the IC.  Most of the power dissipation should occur in the external FETs.  You should be able to heat sink them if required.

    It is possible to measure the closed loop response if you want to break the loop at the usual location between Vout and the upper voltage set point resistor. 

    Generally, the internal circuitry of DCAP2 is proprietary.  I may be able to get the time constant value, but I do not have easy access to it.  Do you have an NDA with TI?  That generally makes it easier to get information.