WEBENCH® Tools/TPS63051: would like to know the current drawn by the regulator

Hi Pragash:

The drawn current could be calculated as Iin=Io*Vout/Vin/Efficiency.  There are some typical efficiency curves in datasheet for reference, as Firgure 10-19. Besides, you could also do the simulation with Webench. 

May I know if I got your point. If not, please don't hesitate to tell me. 

hi Minqiu,

thanks for your reply. I presume Iin is input current to the regulator, Io is output current from the regulator.  I'm asking the current draw of the regulator, meaning current consumed by the regulator while regulating. every system consumes power to do a job. there is no system exist with 100% efficiency, without any current draw/energy lost. 

Hi Pragash:

For the DC/DC converter, the current draw couldn't stand for the power loss well. 

The equation I shared with take the efficiency into considered. As "Iin=Io*Vout/Vin/Efficiency". You could use this equation to calculate the input current.  For the power loss, it could be calculated as "Loss=Vin*Iin-Vout*Io"

Then for the data of efficiency could check the datasheet for reference.

I hope I answer the question this time...If not, just dig it out together. 

we are close now. Ploss = Vin*Iin - Vout*lo

Ploss = Vloss*lloss

i want to know the IIoss.

1) how can i calculate IIoss?

2) where can i find the IIoss in the datasheet? 

3) Is IIoss = Iq (Quiescent current of the regulator)?

4) i believe "Ploss = Vin*Iin - Vout*lo" is equation for LDO. how about switching regulators? do you have the formula to calculate power loss in switching regulator?

Hi Pragash:

So sorry, there is no a equation for switch power shows "Ploss=Vloss*Iloss" As the Vloss and Iloss is no meaning. The Ploss could be calculated as Pinput –Poutput and equals to Vin*Iin–Vout*Iout.

For datasheet, there is no data directly shows the Ploss, but you could calculate it as Ploss=Pin–Pout=Pout/Eff–Pout=Pout*(1/Eff–1). And as I mentioned, there are some typical curves in datasheet about the efficiency, and could be a reference.

Let's back to your questions:

1) how can i calculate IIoss? There is no meaning for Iloss on this case.

2) where can i find the IIoss in the datasheet?  As I metioned above, no Iloss. But could calculate the Ploss with efficiency.

3) Is IIoss = Iq (Quiescent current of the regulator)?

No.

4) i believe "Ploss = Vin*Iin - Vout*lo" is equation for LDO. how about switching regulators? do you have the formula to calculate power loss in switching regulator?

Yes, it's the same. Just check the above.

hi Minqiu,

i really appreciate your time to answer my lengthy questions. however, i really feel we are missing something. the regulator has Ploss so it should have Iloss. if you have any detailed application notes on regulators, please share. I would like to read for my knowledge.

im doing battery life calculation for the embedded system so I will use Iq = Iloss (loss of the regulator). i feel it is better than assuming the regulator is lossless! 

Hi Pragash:

I just think of the Webench maybe another way to help you find the data if the calculation is not so importance. You could do the simulation to get a result. http://www.ti.com/product/TPS63051 (Middle right side at this page.)

If it's needed, we could offer some typical data for you. Please share us more details about your system especially the Vin range, Vout target, and the Load condition.

For the Iq, there is a application note. You could check it. But actually, the Iloss and Iq are not same things. (Sorry that I still have no ideal how to explain the Iloss is ... no practical meaning for power switch. If you want, you could assume a value named Iloss and calculated it with some ways. But as far as I know, it's not a normal way.)  

"IQ: What it is, what it isn’t, and how to use it": http://www.ti.com/lit/an/slyt412/slyt412.pdf