- Support for Vpp up to 80v
- Support for Ibat (output) up to 25a
- CAN (Stuffable optional)
- Dual bank, one can be depopulated to save for $ and cut current out in half.
I have been playing with efficiency modeling some more, and the current components represent the best mix I have come up with yet. While calculating the input capacity losses I had to bring the operating frequency from 50K to 100K in order to get the Iripple down to manageable level. At 50Khz I was getting over a 1W loss in the input caps. At 100K, and limiting configurations to realistic ones I can keep Iripple under 4A, and the input cap losses under 180mW. Here are the 4 configurations I expect folks to run at:
- 1x panel (Vp ~ 32v) --> 12v battery
- 1x panel (Vp ~ 32v) --> 24v battery
- 2x panel (Vp ~ 64v) --> 24v battery
- 2x panel (Vp ~ 64v) --> 48v battery
The worst case combination is actually #1, 1 panel and a 12v battery. With the core switching efficiency of 97.8% at max load. Adding in the cap losses of 75mW, and an estimated uC + CAN loss of 150mW = 225mW total additional loss. This will bring the total system efficiency down to an estimated 97.4%
For a .pdf copy of this, click here:
A few notes:
- Need to scrub all components, recalculating again things.
- Current Best FETs are: Vashrey - SiS468DN. Low cost!, but also PQFN - SMT packaging...
- Need to verify idea of taking controller power from solar panels as opposed to battery and/or both..
- I used a LDO regulator to get g om10v to 5v as opposed to another switcher. Reason is during deep-sleep the uC power is in the uA range, and switchers are very inefficient there. Plus, the LDO will help make a quieter voltage source for the uC's A/Ds
- Want to look at adding simple l/c for the uC's A/D voltage source, to twy and quiet things down.
- There is still no input filtering on the solar panel side....
- Still want to look at FETs, worried about PQFN parts. . . .