Guru
Joined: 09/08/2007
Location: AustraliaPosts: 4406
| Posted: 11:18am 28 Mar 2017 |
One thing that needs mentioning is that there are three totally different types of drive waveforms used to drive bridge type inverters with pwm, and that can make quite a difference.
The Power Jacks appear to drive the upper two mosfets with only a 50 Hz square wave, so the upper pair turn on alternately at only 50 Hz. Then only one of the lower drive mosfets is PWM'd and the other lower mosfet remains off for half a cycle.
I have never had a Power Jack to play with myself, so am not absolutely certain of that but it is a perfectly valid way to do it.
A second way to do it is to drive a diagonal pair together, where one diagonal pair is PWM'd for half a cycle, and then is turned fully off for the other half cycle.
A third way to do it is to drive all four mosfets continuously with pwm, but have the duty cycle of all of them hit 50% together at the zero crossing points.
There are all kinds of advantages and disadvantages with each each of these methods. I rather gather that the 8010 board continuously PWMs all four mosfets, so its fundamentally very different to the Power Jack.
Cheers, Tony.