Electrosurgical generator with adaptive power control

An electrosurgical generator for treating tissue, the electrosurgical generator electrically connected in a circuit with the tissue for applying an output power to the tissue from an output stage, the tissue presenting a variable impedance to the output power, the electrosurgical generator comprising:

• an impedance measuring circuit electrically connected in circuit with the tissue for producing a measurement of the variable impedance;
• a comparator electrically connected to the impedance measuring circuit for comparing the measurement of the variable impedance to an input signal representative of the desired tissue impedance, the input signal having a cyclic pattern;
• and
• a feedback control system in the electrosurgical generator for adjusting the output power, the feedback control system connected to the impedance measuring circuit and connected to the output stage for cyclically changing the output power in response to a signal from the comparator to cause the variable impedance to cyclically rise and fall.

A method for automatically controlling electrosurgical output power across a load, the load having a variable impedance, the method comprising the steps of:

• generating electrosurgical output power, the output power having an RMS value;
• connecting the output power across the load;
• producing a measurement of the variable impedance;
• and
• controlling the output power in response to the measurement by cyclically raising and lowering the RMS value at a frequency to actively repeatedly raise and lower tissue impedance to vary the range of tissue impedances, wherein the measurement follows the RMS value.

A method for automatically controlling output power from an electrosurgical generator across a load, the load having a variable impedance and a thermal frequency bandwidth, the method comprising the steps of:

• generating electrosurgical output power, the output power having an RMS value;
• connecting the output power across the load;
• continuously measuring the variable impedance of the load;
• and
• inducing multiple oscillations of the load impedance by repeatedly raising and lowering the RMS value in response to the measured impedance,
• wherein said step of inducing is performed at a frequency within the thermal frequency bandwidth, said thermal frequency bandwidth being between 1 and 20 Hz.