all home built solar system

Author	Message
wiseguy Guru Joined: 21/06/2018 Location: Australia Posts: 1261	Posted: 05:27pm 04 May 2021         nickskethisniks said   Wiseguy did a very beautiful compact layout with the nano power inverter, roll your own style. But I have a small problem with the gatedrive routing, it's running parallel to the battery busbar wich carries a lot of current. This is probably not an issue for his design parameters but when used under verry high load, you can have inductive coupling on the gatewires and potentially cause problems. There is also no separate return path either which is not ideally. But the area between the gate and return path is low, important to make no antenna. Also the resistive path of the power conductors is not symmetric, the inner fets will have a higher current to carry because they are placed closest to the battery and AC terminals. The mosfets on the outside will carry less current. But then again perfectly for his design parameters. This could be easily solved when the ac output terminals were replaced to the outside of the board, this would create an equally path for each mosfet. Sometimes it's just not possible and designing is also looking for a trade of between different things. Wiseguy I hope I didn't offend you. When I batched all my FETs for on resistance I installed ones with the higher on resistance closer to the centre and the ones with less to the outside - you shouldn't make too many assumptions without being in possession of all the facts, you might be surprised at the lengths I go to in my attempts to get things right. I find it hard to fathom why you are cherry picking what you consider faults or issues with my design, which I might add worked first time, has never blown a FET & has one of the best gate drive results published on this forum to date, and at 2kW output runs a few degrees above ambient with no fan. It also now has the automatic precharge/soft start that I was so canned for when I first suggested it. I cannot agree with you that the MAD board is definitely the way to go, there were valid reasons why I did not copy it (probably similar reasons as to why you are designing a totally different approach). I applaud the fact that there are a number out there working well & for long periods but it seems sometimes they can go bang for unexplained reasons sometimes multiple times before they behave. You are suggesting theoretical and possible perceived issues of my design which are not actual issues that I have seen any evidence of. The difference in energy and time to go from -5 to + 12 compared to 0-12 is negligble. Do the sums: delta 5V 30nF 10A+ of drive current 2R2 resistor no miller effect to fight until you get to ~ 5V positive and we are talking at most a handful of nanoseconds.  In the data sheet with a 6ohm resistor and 10V gate drive, the turn on delay was 28nS and the rise time 18nS whilst fighting 40V of Miller through ~ 1nF. If 1A flows for 1 second we have 1 coulomb, the gate charge of the HY4008 is 200nano coulombs 1/5,000,000 of a coulomb by my sums. Even at 20kHz switching I think that translates to ~ 5mA ? I will read the rest of your post more carefully in the morning it is after 2.30am and I'm turning in now.