TPS61165: Missing/wrong formulas to estimate full Power Dissipation

Hi Attila,

Sorry, we don't provide the detailed parameters such as Qgs, Qgd and Qg you mentioned. 

As for Iq, yes, it includes all internal current consumption.

Thank you very much for your reminder, and I'll let our corresponding colleagues know this. Thanks a lot again!

Robin

Hi Robin,

Sorry, but this thread talk about calculating power dissipation.

Is that all what TI could give as support in this theme?

My target is not resolved, to find tool or formula to determine power dissipation of TPS61165.

Please give me help to calculate/determine power dissipation to recommend a suitable tool or formula.

Or at least to know the parameter of tLH, tHL rising/falling ramp which depend on internal FET. They are mandatory to calculate switching losses.

No feedback about wrong formulas too.

PS: My other ticket has remained open state until this day, included a lot of open questions as here. You did not give suitable response for that. 

(8) TPS61165: Simulation platforms - Power management forum - Power management - TI E2E support forums

Attila

Hi,

Since this is an old device, we really don't have accurate internal parameters of this device.

Robin

If it's convenient, please give me your email and I'll share you with a calculation tool of another device. It may be helpful to you.

Thanks!

Hi Robin,

I am trying to simulate SEPIC design in PSpice for TI and calculate power dissipation there. But I have some problems with this (unstable results, mistic phenomenons).

Could you tell me, TI's TPS61165 model is uptodate and ready to use for SEPIC topology?

What do you think, should TPS61165 be stable with 22uH, 1.6R coupled inductor (Coilcraft LPD4012-223MR)?

The datasheet talks about 10-22uH of inductor range, but it does not talk about SEPIC and coupled inductors. This is a special situation. So I am on boundary with value of 22uH and with type of coupled inductor.

I can not determine, why get I instable simulation results. I need have value of 22uH coupled inductor, because CCM mode have to work reach under between big loading range. I think, errors come from models. I don't think that this design includes any extras.

You said, this is old part. Could you recommended newer alternates?

Problems with Pspice simulation in nutshell:

- I can not use coupled inductor model from Coilcraft (no exist)

- Instable simulation results with 10-22uH inductors with using of internal transformator model, or generic inductor type thought K-statment.

- TPS61165 model does not take attention the Iq. It need have to add Quiescent power dissipation later (Pq).

Reference links for better understanding:

(7) PMP10835: How can I make a coupled inductor in "PSpice for TI" from two uncoupled inductor? - Simulation, hardware & system design tools forum - Simulation, hardware & system design tools - TI E2E support forums

(7) PSPICE-FOR-TI: Understanding of warnings - Simulation, hardware & system design tools forum - Simulation, hardware & system design tools - TI E2E support forums

(7) [Resolved] PSPICE-FOR-TI: Calculating average power loss via S() function - Simulation, hardware & system design tools forum - Simulation, hardware & system design tools - TI E2E support forums

(7) [Resolved] LM3478: The gate drive current IG of the LM3478 - Power management forum - Power management - TI E2E support forums

PS: friendship request sent to you

Hi,

TPS61165 haven't been applied to SPEIC although it could be used in theory.

There is another device, TPS61500, which also supports SPEIC topology. Besides, TI gives its detailed application report, then you can use easily.  Please refer to the attachment.

Robintps61500 SEPIC configuration.pdf

Hi Robin,

I have seen this guide. It is okay, that it describes a lot of things, included power dissipation. BUT, this paper does not talk about power dissipation of IC, which is the main target in my case.

All right, there is not any support for this IC. No usefull pspice model for SEPIC, no formulas, no guides to determine the power dissipation of IC.

We have to go in other direction after this.

Could you tell me estimated dissipation of IC (TPS61165) and efficiency in case of specification below?

VIN(min)=5V

VIN(max)=15V

Vout=10.4V

Iout=200mA

L=22uH, 1.6R (coupled inductor)

L=22uH, 0.4R (coupled inductor as alternate in bigger footprint)

Attila

Hi Attila,

This is a little difficult for me to give you the estimated data since I have no the corresponding EVM for bench test at present.

But, TI provides the efficiency vs. current curve based on the EVM under the conditions that VIN=5V/VOUT=9.5V/L=10uH. It may be helpful to you.

Robintps61165 userguide.pdf

Hi Robin,

I have dropped to buy this board, because this is only BOOST. In my case, I am working with SEPIC. At SEPIC topology, IC has to withstand more stress on SW pin, because voltage and current is much more bigger on internal FET switch to compare to BOOT. It means voltage of VIn+Vout and both of inductor currents (IL1pk+IL2pk) flow throught the pin of SW. And this means much more power dissipation of IC.

Attila

Hi Attila,

We have met few SEPIC applications with this device so far. However, it seems that we need to invest more resources to this aspect.

Robin

Hi Robin,

All right.

As first step, I recommend to revise this guide (and many more), because it used wrong formulas:

Designing DC/DC converters based on SEPIC topology (ti.com)

Equation 14 means Irms of FET switch.

Equation 13 is only valid with using of Dmax, if Irms is cummulative inductor average currents.

As guide uses Irms of FET, so formula for PD is not correct with using of Dmax. Pcond part of PD is failed.

What it means in real aspect, that Pcond is much more then is calculated in this sample application. In this case, it means 40mW more power dissipation for conductive losses.

Note: The more precise formula is to calulate Irms is:

TI's Power Stage Designer calculates very rough results. It could be much more useful, if It does take account FET Rdson and Inductor serial resistance too.

Attila