Quote:
Originally Posted by MPaulHolmes
I would be interested!! I don't really understand though. so, you have a 300v dc input. You pwm that input to make it look like a pwm version of a sine wave. Then you pwm another one with the complement. Then you subtract the results? How do you subtract them?
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The requirement is instead of having complementary PWM outputs for each timer, one needs to have a dedicated output, rather than a complementary mode as they now have.
By default thats not possible with the PIC, but perhaps with a bit of smart coding we could use the interrupts and a look up table to disable one of the channels, so that only the positive or the negative switch can be active at a given time.
For example, assuming an h bridge:
During the positive half cycle, PWM is sent to the high Igbt of leg 1 and the low IGBT of leg 2, so that the voltage is positive (DC-LINK)
During the negative half cycle PWM is sent to the low IGBT of leg 1 and the high IGBT of leg 2, so that the voltage is negative (-DC-LINK)
Here's an example for a single phase inverter using this topology
http://www.journal.au.edu/au_techno/...abstract05.pdf