Electrosurgical generator with adaptive power control
First Claim
1. An electrosurgical generator for applying output power to a load having an electrical impedance, the output power having an RMS value, the electrosurgical generator comprising:
- an impedance measurement circuit electrically connected to the load for producing a measurement indicative of the electrical impedance;
an RF output stage connected to the load for applying output power to the load, the RF output stage having an RF input stage for adjusting the RMS value;
a controller electrically connected to the impedance measurement circuit and electrically connected to the input, wherein the controller induces multiple oscillations of the electrical impedance to cause cycling of the impedance by adjusting the input in response to the measurement.
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Abstract
An electrosurgical generator has an output power control system that causes the impedance of tissue to rise and fall in a cyclic pattern until the tissue is desiccated. The advantage of the power control system is that thermal spread and charring are reduced. In addition, the power control system offers improved performance for electrosurgical vessel sealing and tissue welding. The output power is applied cyclically by a control system with tissue impedance feedback. The impedance of the tissue follows the cyclic pattern of the output power several times, depending on the state of the tissue, until the tissue becomes filly desiccated. High power is applied to cause the tissue to reach a high impedance, and then the power is reduced to allow the impedance to fall. Thermal energy is allowed to dissipate during the low power cycle. The control system is adaptive to tissue in the sense that output power is modulated in response to the impedance of the tissue.
2149 Citations
23 Claims
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1. An electrosurgical generator for applying output power to a load having an electrical impedance, the output power having an RMS value, the electrosurgical generator comprising:
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an impedance measurement circuit electrically connected to the load for producing a measurement indicative of the electrical impedance; an RF output stage connected to the load for applying output power to the load, the RF output stage having an RF input stage for adjusting the RMS value; a controller electrically connected to the impedance measurement circuit and electrically connected to the input, wherein the controller induces multiple oscillations of the electrical impedance to cause cycling of the impedance by adjusting the input in response to the measurement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. 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:
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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. - View Dependent Claims (10, 11)
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12. A method for automatically controlling electrosurgical output power across a load, the load having a variable impedance, the method comprising the steps of:
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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. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. 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:
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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. - View Dependent Claims (20, 21, 22, 23)
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Specification