Hello, i am having serious problem with an inverter im trying make. The driving method is SVM on 23KHz.
The 12V for opto/driver testing is coming from Mastech HY3005F-3 . I cant apply voltage to bridge cause acts like short circuit.
Used a programmable power supply to safe apply voltage on bridge and check the current (if has short-circuit) . Graph its ofc without load.
I have 3 PWM from Mega32 that fed into my optocouplers, then to my drivers and mosfets.
The problem: The output from driver is going to Mosfets gate , is realy changed and as you can see with 200Ω resistor i have some "capacity"
problem on gate.
Reduce the resistor to 20Ω or remove it fixs a lot my signal but i could have 'ringing' problem.
Circuit schematic (a part of it cause too large to embed it. If need i can attach it)
[ Bootstrap capacitors are Tantalum capacitors ]
Signal from driver's legs:
You can see that signals arent so clear but at least they dont mix ! Also you can see the 0.5uSec DeadTime the drivers is adding to signal.
Signal that i measure on mosfet gate with 200Ω resistors:
Its clear that signal mixes and that gate signal isnt the same as driver's . Seems like capacity problem
Yellow gate signal without resistor or with 20 Ω
Signal is getting realy better compared to blue signal which has 200Ω on gate.But i may have ringing problems
The circuit is on PCB as you see below:
If i give 1KHz PWM signals (via fuction genarator) to optocouplers and i remove Gate resistors : Mosfets stay cold , current drawn of bridge is 30-40mA. (without LOAD)
If i increase frequency >4Khz with above setup the problems starts again.
Distance may add parasitic industance , specially on those Power-Switching circuits. But even on so low frequency ?
If i missed any serious info about circuit/driving/componets. Just ask