I have been using a SIMetrix simulation for conducting investigation on a simple full bridge inverter. I expect the waveform to be bipolar but I keep getting the unipolar waveform as shown below. I am aware that voltage waveform should be bipolar but it is not happening on my simulation. Please tell where did I go wrong?
PWM - 1kHz
Voltage - 200V
Voltage input to each MOSFET - 5V (Offset - 2.5V)
Duty Cycle = 50%
Rise Time = 0 (On every MOSFET)
Fall Time = 0 (On every MOSFET)
Q1 and Q4 - Inverted Square waveform
Q2 and Q3 - Non-inverted Square waveform
You cannot drive the gates of upper two FETs WITH RESPECT TO GROUND unless V4 and V5 are +205V!!! (Not a practical way to do it). They have to be driven with respect to their own Sources. Your basic H bridge is not correct.
You cannot drive the gates of upper two FETs WITH RESPECT TO GROUND unless V4 and V5 are +205V!!! (Not a practical way to do it). They have to be driven with respect to their own Sources. Your basic H bridge is not correct.
Its a trade off!! You can use 4 NFETs and have a horribly-complicated Gate driver for the top two, or you can use PFETs for the top two devices and have a simpler gate driver for the top two; or you can use split -100V and +100V supplies, and have the simplest gate driver...
You could also use a pulse transformer to control the high side but it will only work for AC voltages and there can't be any net DC e.g. the duty cycle needs to be 50%.
You could also use a pulse transformer to control the high side but it will only work for AC voltages and there can't be any net DC e.g. the duty cycle needs to be 50%.
That's true for a DC coupled circuit. But you can use any duty cycle with a transformer if you couple the signal through a series capacitor to keep the average dc current at zero. Of course, the DC level signal at the transformer output will be at whatever is the average value of the signal waveform. From that you likely can use a clamp circuit to restore the DC level to whatever you need.