TPS61099: Low efficiency problem

Lumina Gui

Part Number: TPS61099
Other Parts Discussed in Thread: TPS61299

Hi TI Teams,

One of our customer reported that the efficiency is only 74%~76% with the real load like MCU,small fan and laser (the laser is switched on at 0.5s intervals, and the other loads run continuously). However, the efficiency is above 90% when tested with dummy loads. They also tried adding a 22uH Π filter circuit to the output, which would increase efficiency by 3%, but it didn't meet the requirements. The efficiency difference is only 3% with different inductors.

The schematic and layout is as below:

Do you have any good suggestion for this problem?

Thanks,

Kind Regards

over 2 years ago

0 Nini Zhong over 2 years ago

TI__Genius 14765 points

Hi Lumina,

What do you mean dummy loads?

How much is the actual load? hundreds of mA? What is the input and output voltage ?

0 Dong Liu over 2 years ago in reply to Nini Zhong

Prodigy 20 points

Dummy load: 50R power resistor.
Real load: input voltage 3~3.6V, output 5V, current switches between 20~70mA.

Current reference curve of real load 5V output:

0 Nini Zhong over 2 years ago in reply to Dong Liu

TI__Genius 14765 points

Hi Dong,

It's reasonable the light load efficiency is lower than heavy load. It's hard to achieve high efficiency under ultra light load because the control logic circuit loss counts a lot .

0 Dong Liu over 2 years ago in reply to Nini Zhong

Prodigy 20 points

I think 20~70mA is not small. According to the TPS61099 manual, 90% efficiency can be achieved above 1mA. It should be other reasons that cause the efficiency to be too low. If this model is not suitable for this scenario, are there any other models that you would recommend? In addition, we also tested the TPS61023DRLR, and the results were similar, with a resistive load of 92% and a real load of 40%.

0 Nini Zhong over 2 years ago in reply to Dong Liu

TI__Genius 14765 points

Hi Dong,

From the load current shown by your side, it's load current of pulse load. That means the average current is 20mA and 70mA. The current can be as smaller as uA, the converter is working in transient load conditions, which is different from the normal efficiency test condition : steady state condition, By the way, if the high frequency under such load condition is needed, recomend to use TPS61299 as alternative.

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TPS61099: Low efficiency problem