Power inverter H bridge drive signal design.

Thread Starter


Joined Oct 15, 2020
Hello, I am currently designing a modified sine wave inverter using SG3525 as push-pull and ATMEGA238P as H-bridge drive signal generator and for other monitoring purposes. I don't want to use an H-bridge driver ICs so I want to implement some part of this design by Texas instruments: ti.com/lit/ug/slva578/slva578.pdf (the schematic starts on page 10) I am a bit confused about two parts of this schematic:

1. What are the J3 and J4 coils? Are they wrapped on to the transformer T1 or driven separately. Also, they are for providing the shifted voltage drive signal for the upper two MOSFETs? (J3 and J4 don't seem to be in the BOM)

2. I noticed that the two grounds are separated before and after the transformer, I know this is to provide isolation. But how does the MCU measure the battery voltage and the 3.3V reg work if their grounds are not referenced to the battery GND? Also, what is the purpose of putting the MCU grounds after the transformer if in the design the High voltage feedback and H bridge are isolated by optocouplers?

Thank you very much!