Solar powered mobile phone charger - need help finding suitable parts

[Slobodan]

Can someone help me find chips that i can use to design solar powered mobile phone charger?

It should work something like this:
Solar panel powering battery charging chip with integrated MPPT, which would charge the battery, which would power the DC/DC boost regulator, wich gives 5V at the output.
Simple.

I would use a 6V solar panel (2,4W). Umpp=about 5V.

The battery is single cell Li-Poly 1800mAh (3.7V nominal).

First chip should be LiPoly charger controler (single cell, 3.7V) that has to have integrated MPPT (maximum power point tracking).

Second chip should be DC/DC boost converter with 5V@500mA output, that can deliver with an input voltage of 3V or less. With the highest possible efficiency for 2,8 or 3V to 4,2V input.


First, i have tried to design it using 3 chips.
1. LTC3105 (DC/DC boost controler optimised for "solar harvesting" aplications) which i thought of paralleling two of them to achieve suitable power output. But, this chip just doesn't work. It should regulate the output current in order to maintain the input voltage at a set level, but i doesn't.
2. MCP73861/3 (Li-Ion/Poly charger controler) which would be powered from the LTC3105. This chip works just fine.
3. SP6641B DC/DC boost regulator (5V@500mA output) which should be powered from the LiPoly battery. This chip doesn't work, becouse the output voltage falls to about 3,5V@500mA.


Then, at my second attempt, i have made a big mistake. I have chosen 4 chips (2 each) that are in the packages that doesn't have pins. They are DFN8, QFN20, SON10 (or WSON10, or something like that).
Those chips are:
LTC3529 boost converter (DFN8 2x3mm)
TPS61026 boost converter (SON10 or DFN10 3,25x3,25mm)
BQ24210 battery charger controler vith MPPT (SON10 2x3mm)
MCP73871 battery charger controler with Voltage Proportional Current Control (QFN20 4x4mm)

I have spend a lot of time searching for adapter boards so i can solder this chips on them and experiment with them on the breadboard. I couldn't find them so i had to design them myself and get them made (wich cost me 40 euros).
Now i have the adapter boards and a have tried many times to solder the chips on them, but i just can not. I mean, they are "soldered" but who who knows how meny pins are left unsoldered...

So, i am asking for help finding parts that are in "normal" packages (with pins, so i can solder them easily).
I have spent a lot of money on this already, so it would be good that this chips are not expensive. And it would be good that i can buy them from Farnell.

Men, i have spent about an hour writing this with a help from google translator.

P.S. These are the adapter boards.



And, i know, i screw up the third one.


P.P.S. By the way, this is for my school, what you call, "senior project", so it is important for me. I known it is "to simple for the senior project", but i wanted to do the simplest thing that they will accept and i known how to design.

[steaky1212]

Slobodan,

This is in the Uk so I dont know how different it is but...
For my final year project you were allowed to work in pairs. We decied to construct an analogue electronic drum kit plus amplifier. All of the sounds were generated using inputs from piezo transducers and fed through various circuits. The snare was the best as we needed to combine the drum sound with a white noise source for the rattle. As it turned out one of the drum sounds kept going intermittent when hit and of course it failed to sound in our demonstration.

Someone else on my course did a low powered water activated flashing light for use on a life-preserver (he had plans of entering the Royal Navy). Sure it worked, but it was "just" a flashing LED project.

My main point is that it doesnt matter about how complex or simple your project is (or if it works or not) - surprisingly. If you can justify your decisions, and keep decent documentation then you should be fine.

If you read the datasheet before buying the part then you should see what are solderable - SOT, DIP and TQFP are all hand solderable without much drama.

Also, it might be worth going direct to the manufacturer as they might offer free samples (especially to students).

Good luck

[Slobodan]

If you read the datasheet before buying the part then you should see what are solderable - SOT, DIP and TQFP are all hand solderable without much drama.

Well, i thought that i will be able to solder them "dead bug" stile, but i was wrong.



I have searching for the new parts and I have found SPV1040, which is a battery charger with MPPT, but it doesn't say what type of batteries can it charge, so i am still searching.

I have also found TPS61032 (boost converter), which i think it will work.

[Slobodan]

I think i am gonna go with TPS61032 boost converter.

I am still searching for the MPPT chip for charging Li-Po battery so if you known about such chip please let me known. It can even be DC/DC conwerter with MPPT (like this one LTC3105) and a seperate battery charger chip.

[NiHaoMike]

What about a low power microcontroller with built in ADC and PWM?

[Slobodan]

I don't know programing, so i want to use a dedicated chip.

[Slobodan]

I have been searching on manufacturers sites for hours and found nothing.

Is it possible that this is the only one?

Texas Instruments BQ24210         
http://www.ti.com/lit/ds/symlink/bq24210.pdf



There is also Microchip MCP73871, that can be used with solar panels       
http://ww1.microchip.com/downloads/en/DeviceDoc/22090b.pdf



And i found this one to SPV1040, but it can only charge NiMh, NiCd and Lead acid batteries.   
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00287506.pdf

[bfritz]

I think you should talk to a professor or whoever runs the electronics lab there.  The packages you have listed are not that difficult to solder.

I would suggest solder paste.  A small dab on each pad.  If you don't have paste, you can use some solder, and just put the solder on the bare board without the part, until the solder forms a very small mound on the pads.  Then use some flux, preferably paste flux rather than liquid, and put that on the pads, and set the part into the paste flux on top of the small mounds of solder on the pads.  A hot air rework tool that allows you to control air flow and temperature is preferred, and just heat till the solder reflows, and the capillary action of the solder will move the part perfectly into place.  If you don't have a hot air rework tool, I've used a hot plate, and placed the pcb down on the hot plate and allowed the heat to heat through pads, solder, and pins through the pcb.  Watch and remove the pcb carefully with tweezers when the solder melts, and forms a nice fillet to the pins.

I would really try and use what you've done.  Why not try?  Right now you've resigned the boards as a failure, so what is to lose?  They look like they should work to me. 

[NiHaoMike]

I don't know programing, so i want to use a dedicated chip.

C (or C++) is very easy to learn. I would suggest using either a low power PIC or an underclocked Arduino (AVR).

[Slobodan]

I think you should talk to a professor or whoever runs the electronics lab there.  The packages you have listed are not that difficult to solder.

I would suggest solder paste.  A small dab on each pad.  If you don't have paste, you can use some solder, and just put the solder on the bare board without the part, until the solder forms a very small mound on the pads.  Then use some flux, preferably paste flux rather than liquid, and put that on the pads, and set the part into the paste flux on top of the small mounds of solder on the pads.  A hot air rework tool that allows you to control air flow and temperature is preferred, and just heat till the solder reflows, and the capillary action of the solder will move the part perfectly into place.  If you don't have a hot air rework tool, I've used a hot plate, and placed the pcb down on the hot plate and allowed the heat to heat through pads, solder, and pins through the pcb.  Watch and remove the pcb carefully with tweezers when the solder melts, and forms a nice fillet to the pins.

I would really try and use what you've done.  Why not try?  Right now you've resigned the boards as a failure, so what is to lose?  They look like they should work to me. 

Thanks. I have tried all that. I have been in school and nobody there can solder those chips. They say the only way to solder them is in reflow oven. I own a hot air station, and tried several times to solder them with it, but the pads are to smal that practicly no solder is sticking to them (even with a lot of flux, licquid, but still...).

If i don't find suitable ICs in the easy to solder packages, i will have to use this ones.

[Slobodan]

I don't know programing, so i want to use a dedicated chip.

C (or C++) is very easy to learn. I would suggest using either a low power PIC or an underclocked Arduino (AVR).

I will learn C, but not right now, i don't have time. And plus, i don't wont this project to be "software based".

[mikeselectricstuff]

This project may be useful :
http://www.adafruit.com/products/390

[Slobodan]

Thanks Mike, I know. That's why i wanted to try MCP73861/3.

[Slobodan]

I have received the TPS61032 switching regulator. In datasheet it says that thermal pad should be connected to PGND pin, but i can not physically solder them (i have tried) so i just connected it on the breadboard and it works (it gives 5V at the output). But, one chip just stopped working (maybe it vas ESD, someone mention this on the TI site, that it is realy sensitive to ESD). So i soldered another one, i connected the load (10omhs or 500mA) and mesured the voltage ripple. When i disconnected the load, white (magic) smoke came out. I have only tested it for a few minutes, and the chip did not get hot.

I have only one chip left, and i dont know whether i destroyed it with EDS, or it is becouse thermal pad isn't connected to the PGND pin (it is connected internaly), or what is...

Do you know what else could it be?

[Slobodan]

Anyone?