I have this simulation set up in Every Circuit. It can be viewed here:
http://everycircuit.com/circuit/5875415639916544
For right now I have turned off M3 by jumpering M3's gate to the ground nearby. Simulating with an 18V solar panel and a 12V battery I can see in Every Circuit that when M1 and M2 are on there are some milliamps flowing to the positive terminal of the 12V battery through inductor L1. Those ma's are on M1&2's conduit.
So the software switches between HO and LO. Is VS just a ground or does some current come out of VS when HO or LO is on? The data sheet must say but I don't know where to look.
I think I understand already that D3 and C5 and R2 are for the excess charge built up in inductor L1 and a path is provided for that power to flow and dissipate when polarity is reversed on L1.I've gone through a simple buck converter in Every Circuit so I think I understand L1's diode assembly. Perhaps the concept for the diode assembly D3,C5,R2 are similar to the concept (A Buck Converter):
http://everycircuit.com/circuit/6539292895608832
I've been told that C2 is a bootstrap cap for M2 however from the schematic I see that C2 is connected to M2's source not its gate as I thought it should be (or am I wrong on this?). So how does C2 bootstrap M2's gate if it is connected to M2's source pin?
I'm not sure I understand yet why in my simulation that there is no power flowing through the bootstrap cap or the bootstrap caps diode? I made a small edit where I connected that cap to the VS line.
Thank you
schematic is here: http://freechargecontroller.org/images/a/ab/Charge_controller_4_04b.pdf
P.S. I've made an attempt at integrating what might happen when IR2104 is working:
http://everycircuit.com/circuit/4572109894320128
In my sim software I have the option to apply a frequency so I'm thinking I can use a logic gate and two frequency voltage sources to sim the IC2. This is a lot of new stuff to me.
Screenshot (http://i.imgur.com/Pk2EsXa.png) :
Best Answer
I cannot answer questions about that websim because I'm unfamiliar with it, so I'll address just "how does C2 bootstrap M2's gate if it is connected to M2's source pin?" There are several (free) appnotes that explain how that works. I see no point in parroting one, so here's a relevant excerpt from Fairchild's "AN-6076 Design and Application Guide of Bootstrap Circuit for High-Voltage Gate-Drive IC".