POV: You're Current in an H-Bridge Inverter

Lesson notes

Key points

• You leave the DC bus positive rail, and switches S1 and S4 are on, so you flow left to right through the load.
• Suddenly S1 and S4 switch off, and after a short dead time S2 and S3 turn on instead.
• Now you cross the load right to left, so the load sees negative voltage: you have just made alternating current.
• Guess why the dead time matters: if S1 and S2 were on together, you would short the DC bus, called shoot-through.

Definitions

Shoot-through

Both switches in one leg conduct at once, shorting the DC supply and destroying devices.

Takeaway: An H-bridge flips diagonal switch pairs to turn DC into AC.

Positive halfDead timeNegative halfShoot-through