Does the upper switch have a definite V differential between gate and emitter when it is supposed to turn on?
If the gate needs to see a low-impedance path to ground via the emitter, is there a path to ground?
As said, the waveform looks like no load resistor connected (or a rather large value, surely not 22 ohm).
I changed the load for a resistor of 6.2 ohms. Now it seems that the high side don't have problem, but the low side looks bad. I know that the resistor is well connected because is warming up and the voltage source shows current consumption (almost 5 amperes).
Yes, it can't but react with the high side gate signal when you make the half bridge source an output current.Is looking bad. Now there is a delay not just at turn off but at turn on (in fact is turning on before the gate signal!! it seems like is reacting with the Vge signal of high side).
Very true. Both Vce measurements are basically showing the same switching waveform, differing by the constant bus voltage, and one shown inverted.And the problem remains when i look Vce of both signals.
Working well isn't the right term. It's normal operation, that the commutation (switchover of output curent between low and high side transistor) timing varies with output current sign and magnitude. The effect becomes more complex if you change to inductive loads and different load power factors, e.g. in an AC motor inverter.Is normal that the inverter works well with very small load values like 6.2 ohms, or 10 ohms (with this value works too) but doesn't work with 22 ohms?
" Use a second low-ESR capacitor from VCC to COM.we recommend a value at least ten times higher than CB."
Cb= C10= 25 uF
Ccom= C9= 1 uF
Your caps are reversed ;O
Correct driver bypassing is recommended anyway.
Without a load resistor, the output voltage does not change during dead time, when the IGBT is turned off. The output node is floating respectively keeps the voltage due to transistor capacitances.
According to the original waveforms, you have implemented plenty of deadtime in the gate signal generation. There's no reason to assume it's not suffcient.I have to be sure that always T1 than T2 are ON right? because if they don't there could be a short circuit problem with T1 and T4 (T1 doesn't turn off until T4 turns on due to transistor capacitances). How can i do that?
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