I have completed a sophisticated Highly Efficient Qi Lime Pi ProtoShield. The boards are on their way! The Qi Lime Pi is a Qi/Battery powered and prototyping shield for the Raspberry Pi.
Presenting the Qi Lime Pi..In Red, Green, Black and Moldy Purple!
Front and Back:
My Entry! A Qi Lime Pi - A Qi Powered Raspberry Pi Plate
Qi Lime Pi Booting up!
Qi Lime Pi mounted on the Raspberry Pi powered via the transmitter and receiver coils!
Voltage is a very good Regulated 5V!
Qi Lime Pi Booting up off a Custom SD Card Image.
The battery charging circuit works as well but for my purposes I didn't need the battery charging circuit. I wanted the Raspberry Pi to shut off like a light switch when I pull it off the Qi Transmitter. With the battery the Qi Lime Pi keeps charging the battery until full and then powers the Raspberry Pi until the battery is dead when pulled off the transmitter.
This Qi Lime Pi shield has the following:
Full Evaluation Board Qi Receiver- Has a solder jumper to allow for either a Qi 5V pass through voltage or battery charging functions, comes with lots of test points!
Battery Charger with a GUI Using I2C-A complete charger module for charging compact, flexible, high efficiency, switch-mode charge management for single-cell, Li-ion and Li-polymer batteries.
GUI-Yes this has a GUI. You can download and look at it now right from TI.com! bq2427xEVM_SW_V0001.zip
IC Controlled NexFET Power MOSFET-The NexFET power MOSFET has been designed to minimize losses in power conversion load management applications. The SON 3x3 package offers excellent thermal performance for the size of the package! I had to custom make a SON-8 package for Eagle!
Low Input Voltage Synchronous Boost Converter with 1.3A Switches-More than 90% efficient, Automatic Transition between Boost Mode and Down Conversion Mode, Quiescent Current less than 55 uA. Operating Range from 0.3V to 5.5V, Output short circuit protection under all operating conditions, Power Save Mode, Overtemperature Protection.
I will say it again, It isn't just a battery charger, it is a complete High-Efficiency Switch Mode Charger with Separate Power Path Control!
What is Power Path Management,
-It allows the device to power the system from a high efficiency DC to DC converter while simultaneously and independently charging the battery. The charger monitors the battery current at all times and reduces the charge current when the system load requires current above the input current limit. This allows for proper charge termination and timer operation. The system voltage is regulated to the battery voltage and will not drop below 3.5V. This minimum system voltage support enables the system to run with a defective or absent battery pack and enables instant system turn on even with a totally discharged battery or no battery! Try that with your iPhones or Droids! The power path management architecture also permits the battery to supplement the system current requirements when the adapter cannot deliver the peak system currents. This enables the use of a smaller adapter.
-The battery is charged in three phases:
---conditioning, constant current, and constant voltage
The charger also offers the a voltage based battery pack thermistor monitoring input (TS) that monitors battery temperature for safe charging.
Here are the details if you want or just skip ahead:
-Instantly Startup the system from a deeply discharged battery or no battery
-Integrated FETs for up to 2.5A charge rate, even though I limited this rate to 1A
-Highly integrated Battery N-Channel MOSFET controller for Power Path Management
-Safe and accurate battery management functions
----0.5% Battery Regulation Accuracy
----10% Charge Current Accuracy
-Voltage based, NTC monitoring input (TS) for measuring the temperature of the battery, I also used a solder jumper for this option to be either enabled or disabled
-Thermal regulation protection for output current control
-Battery Short Circuit Protection
-Soft start feature to reduce inrush current
-Thermal shutdown and protection
-Battery charging status LEDs and signal LEDs
Best of all I included the connections for a USB kit from Ti so you can program your own battery charger from the default settings and monitor the battery charging process on a computer. So with this Qi Lime Pi shield you are basically getting a BQ24272 Evaluation Module from Ti embedded on a Pi shield.
This Qi Lime Pi Shield isn't for everyone! This is a kit for the people that want to experiment with different battery types, different charging patterns, different voltages, efficiencies, etc. I wanted to make a kit that includes two of the most efficient, best products that TI has on the market right now. I wanted to include functionality to expand to other devices if needed. This board and design will be easy to transfer over to other designs and boards such as the BeagleBone Cape, in which I will show you in my next post! The Hot Qi Dog Cape officially working!
The Qi Lime Pi Slice Shield has arrived and will be put together as soon as I can get my hands on the BQ51050B that will have just a basic Qi Receiver/battery charger and buck boost for simplicity.
I will post my design files for this Slice version in a later post when I have fully tested this design and have a fully working prototype! Again, The boards have arrived!
Thank you TI for most of the hard work on making Great Eval Boards and Great Documentation!