A power control system for controlling the delivery of power to a vessel fusing surgical instrument including an end effector, the power control system comprising: an impedance sensing circuit (390, 392, 394, 395, 388) for detecting impedance from an alternating output voltage and an alternating output current delivered by a power supply to the vessel fusing surgical instrument; a power sequencing module configured to automatically sequence the power delivered by the power supply; wherein the power sequencing module is configured to apply power at a constant power, Pmax, of no less than 7 watts and no more than 35 watts during a period of time of 3 seconds or less, wherein: applying a constant power comprises allowing the current to float between 0.5 and 2 Amperes RMS and the voltage to float below 100 Volts RMS; and the period of time is measured from the beginning of the application of power; monitor the impedance through the impedance sensing circuit during the period of time; and reduce the power when the impedance reaches a set impedance threshold within the period of time; and switch off the power when the period of time has elapsed, wherein the impedance threshold is indicative of the beginning of desiccation of a blood vessel and the step of reducing the power further comprises reducing the power by 60% to 80% to a reduced power, Pmin, for a length of time prior to terminating the flow of power. an impedance sensing circuit (390, 392, 394, 395, 388) for detecting impedance from an alternating output voltage and an alternating output current delivered by a power supply to the vessel fusing surgical instrument; a power sequencing module configured to automatically sequence the power delivered by the power supply; wherein the power sequencing module is configured to apply power at a constant power, Pmax, of no less than 7 watts and no more than 35 watts during a period of time of 3 seconds or less, wherein: applying a constant power comprises allowing the current to float between 0.5 and 2 Amperes RMS and the voltage to float below 100 Volts RMS; and the period of time is measured from the beginning of the application of power; monitor the impedance through the impedance sensing circuit during the period of time; and reduce the power when the impedance reaches a set impedance threshold within the period of time; and switch off the power when the period of time has elapsed, wherein the impedance threshold is indicative of the beginning of desiccation of a blood vessel and the step of reducing the power further comprises reducing the power by 60% to 80% to a reduced power, Pmin, for a length of time prior to terminating the flow of power. applying a constant power comprises allowing the current to float between 0.5 and 2 Amperes RMS and the voltage to float below 100 Volts RMS; and the period of time is measured from the beginning of the application of power; monitor the impedance through the impedance sensing circuit during the period of time; and reduce the power when the impedance reaches a set impedance threshold within the period of time; and switch off the power when the period of time has elapsed, wherein the impedance threshold is indicative of the beginning of desiccation of a blood vessel and the step of reducing the power further comprises reducing the power by 60% to 80% to a reduced power, Pmin, for a length of time prior to terminating the flow of power.