17mm buck-boost driver (TPS63020 and LT6106)

[foulmist]

I received the 2 boards from Kent. One with a blown TPS and the other had the TPS a little bit not properly soldered. anyway I fixed them and tested them... Here are some results (mostly in videos but I will try to explain what is happening in them).

One thing that needs to be changed in the layout is the Zener diode.. It's messing the ouput a lot causing all kinds of oscillations at different voltage input and output ranges. And some spikes even. After removing it the output is almost perfect. Only few problems arise at output current less than 250mA causing some oscillations and in buck mode at maximum current and input voltage of 5.5V. But those are rare cases that I think no one here will ever meet.

First video is showing the tests with the original design featuring the 5.6V (~5.3V) Zener diode which is considered to be for OVP (overvoltage protection) BUT it's absolutely not necessary as the TPS already features a built-in one at ~6.8V. It caused a lot of problems at the output.

Second video is showing tests with the zener diode removed. Also I tried a A123 3.6V LiFePo4 Battery which is Ok for currents upto 1.6A but in order to meet the full output ~1.9A to ~2.1A a 3000mAh 3.7V Li-Ion battery was used.

Ripple Current in boost mode at maximum output is almost 60mA which is pretty good!!! It lowers with decreasing the output current.

Ripple Current in buck mode is almost 20mA. Awesome!

I didn't take a shot at the startup but there aren't any spikes at all.
Only with the zener the startup was oscillating a bit before it stablelized (how the hell is that word spelled )

Ok I will try to explain with bubbles in the videos: here goes...

Video with Zener:

Video without Zener:

Thanks for watching.
My Overall opinion is this driver (without the zener) is pretty good (and expensive ). With the common ground and pot for adjusting the current it beats all the drivers til now.

Great job Luke. The force is strong with you :wave:

 

[tsteele93]

Yep there the bridged pins.. I think with this IC you dont even have to put paste on the pins. Just a couple ribbons underneath it and it will push the solder onto the pads as it sinks. I tried to put it on each seperate pad on the ic there is 2 on the cap side and 3 singles on the inside of the ic the rest is easy cuz there bridged pads.


Ya know here is a thaught... Brainfart... If they put an extra layer of epoxy or whatever they use on the top coat just revealing the pads with a .01 or .02 they could essentially make the board with the stencil made into it. no need to syringe it onto the pads just smear it on and squeeje it off.

I HATE this chip. But I am trying to work with it and some of its brothers. I wish TI would make an easier version!

 

[AnthoT]

Wow, that looks very promising especially without the Zener

 

[gillza]

Great! One more driver to our arsenal!
I was wondering, this gigantic potentiometer could potentially be changed to a smaller version or a fixed resistor right?

 

[foulmist]

yes you can use a value between 0 and 200ohm resistance

 

[gillza]

yes you can use a value between 0 and 200ohm resistance

Thank you.

I am trying to understand the diagram (noob alert) and wanted to ask if when the zener diode is removed the V+ and Out pins on LT6106 need to be bridged?

Thank you for help!

 

[foulmist]

Thank you.

I am trying to understand the diagram (noob alert) and wanted to ask if when the zener diode is removed the V+ and Out pins on LT6106 need to be bridged?

Thank you for help!

No nothing is bridged just the zener is out..

 

[Kizdawg]

Kewl! looks great... but yes dem bugger chips to solder.. I am working on my 405nm stensil maker still just waiting on some kapton film and some info on how to drive it with the arduino.. I hope it works ok I think it is capable..

 

[laserluke]

Great job Luke. The force is strong with you :wave:

Many thanks :beer:
Now you should try to left open the output with no load and measure the maximum output voltage limited by the TPS63020. If it's reasonable we are ok and you can safely remove the zener, but if it's too high and dangerous for the output capacitors (C4, C5 and C6), you must remount the zener and compensate it's intrinsic capacitance by changing the values of R5 and C7 to suppress any residual oscillation.
-Luke

 

[foulmist]

Many thanks :beer:
Now you should try to left open the output with no load and measure the maximum output voltage limited by the TPS63020. If it's reasonable we are ok and you can safely remove the zener, but if it's too high and dangerous for the output capacitors (C4, C5 and C6), you must remount the zener and compensate it's intrinsic capacitance by changing the values of R5 and C7 to suppress any residual oscillation.
-Luke

Hey luke, the OVP voltage by the TPS is 6.8V or 6.9V. I have already measured it. The caps don't seem to fail with a no load. Are those 6.3V caps? I think they can withstand the little above voltage at least for some time. What do you think?

 

[laserluke]

Hey luke, the OVP voltage by the TPS is 6.8V or 6.9V. I have already measured it. The caps don't seem to fail with a no load. Are those 6.3V caps? I think they can withstand the little above voltage at least for some time. What do you think?

Ok, good news... i think that it should go, so the zener can be safely removed
-Luke

 

[tsteele93]

I have been away from this discussion, so I am not sure if this has been mentioned.

PDF Different Methods to Drive LEDs Using TPS630xx Buck-Boost Converters PDF

 

[laserluke]

I have been away from this discussion, so I am not sure if this has been mentioned.

PDF Different Methods to Drive LEDs Using TPS630xx Buck-Boost Converters PDF

Hi Tom,
nice to hear you again
The application report that you are mentioning contains three circuits:
"circuit 1"- TPS63020 and a shunt resistor (very poor efficiency and high thermal dissipation due to shunt's power loss);
"circuit 2"- improved version of "1" but the output current is not constant because it partially depends upon the diode's forward voltage;
"circuit 3"- improved version of "2" but with the need of an external voltage reference (other components...)
Moreover none of the three proposed circuits is adjustable neither supports a grounded load
-Luke

 

[Kizdawg]

I'm going to buy a couple more.. try again. I need a better way to aplicate the solder paste...

I baught some of that red tacky flux but I really dont know how to use it.. but I assume it is for this work somehow..

 

[laserluke]

To anyone interested:
the driver's output current is given by the following equation:
Iout=(R4+R2)/100
For example, if you choose R4=100ohm the output range will be 1A to 3A.
However the output maximum current is limited by the TPS63020 capabilities
-Luke

 

[Kizdawg]

Can we actually get these into the 3A range? I'm sure Toma said the 2A ish was all we could hope for because of the TSP. I do have some 100ohm 0605 1/10W from the ben boosts with OVP I could give it another go.. I would think that I could be happy with 2.2A-2.4A.