Preventing Shoot Through Current in an H Bridge

Shoot through current usually leads to catastrophic damage in an H Bridge. Shoot through happens when both the High Side and Low Side Power MOSFETs or IGBTs are ON at the same time.

Even in well-designed systems logic propagation, delays and MOSFET gate capacitances can create a situation where both the High and Low Side devices are concurrently switched ON. When this condition occurs the current flows directly to ground and bypasses the load.

For more information please read Application Notes AN896, AN893, and AN857 which provide descriptions of techniques useful in preventing shoot through current.

The PWM modules on some Microchip devices, such as the dSPICxxGS and dsPICxxMC families, have built-in features to prevent shoot through.

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