A vessel sealing instrument includes a housing having a shaft extending from a distal end thereof having an end effector assembly including a pair of opposing first and second jaw members operably coupled thereto. A drive assembly is disposed within the housing and is configured to move the jaw members upon actuation thereof between an open position and a closed position for clamping tissue with a closure pressure within the range of about 3 kg/cm2 to about 16 kg/cm2. An anti-backdrive assembly is operably disposed within the housing and includes a drive wedge. A solenoid controller is operably coupled to the drive wedge and is configured to selectively move the drive wedge into the drive assembly upon activation thereof to increase the closure pressure between the jaw members in response to tissue expansion during sealing.