- Joined Apr 1, 2016
Connected as u said above, working.
1) Not surprising. Without the MOSFETS switching, the bootstrap circuit won't work correctly.when I testing the circuit without mosfets circuit as #23, it shown the HO had some different waveform
When I tried to using the IRF540.sub you provided, but it won't works and it can't be reedited, so I changed to used the internal provided by Linear.1) Not surprising. Without the MOSFETS switching, the bootstrap circuit won't work correctly.
2) V2 and V3 should be out-of-phase non-overlapping clocks.
3) According to the datasheet the optoisolator outputs should have pull-up resistors when driving CMOS inputs.
4) The circuit in post 24 won't work correctly when the default FETs are used, since they draw only ~1mA and result in VS staying at about 12V. This also prevents the bootstrap working. Shouldn't your .inc directive include the IRF540 sub file?
Thanks.Scott, you need the VS pin switched by the FETs for the bootstrap to work. Unless VB can exceed VS by ~7.5V the under-voltage protection kicks in and prevents HO going high.
Try my .asc in post #18.
I mean that you have to prepare three sets of power, each sets of power providing the isolated power for each h-bridge circuit and its related circuit, otherwise you can't get three isolated ground.Sorry I don' think I understand this ? Could you maybe explain it with bit more details?
It seems there is something wrong with the power of h-bridge, you should be in series from h-bridge 1, h-bridge 2, h-bridge 3, but you in parallel them then the whole h-bridge only can be handle 24V was not 72V, and from the h-bride 1 label ground as gnd1, gnd2 gnd3.
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by Jake Hertz