Electrosurgical generator and system
First Claim
1. An electrosurgical generator for supplying radio frequency power to an electrical instrument, the generator comprising a radio frequency output stage having at least a pair of electrosurgical output lines for the delivery of radio frequency power to the instrument, a power supply coupled to the output stage for supplying power to the output stage, and control circuitry including sensing means for deriving a sensing signal representative of the radio frequency peak output voltage developed across the output lines, wherein the output stage comprises a series-resonant output circuit coupled to the output lines and switching means coupled to the resonant output circuit, and wherein the control circuitry is operable to vary the switching intervals of the switching means to reduce the delivered radio frequency power in response to a predetermined condition of the sensing signal.
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Accused Products
Abstract
A radio frequency generator for an electrosurgical system is provided, the system including an electrode assembly having two electrodes for use immersed in an electrically conductive fluid. The generator has control circuitry for rapidly reducing the delivered radio frequency output power by at least 50% within at most a few cycles of the peak radio frequency output voltage reaching a predetermined threshold limit. In this way, tissue coagulation can be performed in, for example, saline without significant steam generation. The same peak voltage limitation technique is used in a tissue vaporisation or cutting mode to limit the size of the steam pocket at the electrodes and to avoid electrode burning. The generator has a push-pull output stage with a series-resonant output circuit, the output stage being driven by a radio frequency oscillator at a frequency which, in general, differs from the resonant frequency of the resonant output circuit. Power control is achieved by varying the ON-time of switching transistors forming the push-pull output pair and by altering the frequency spacing between the excitation frequency and the resonant frequency of the series-resonant output circuit. In an alternative embodiment, a bridge configuration using two push-pull pairs is used, yielding a further power control variable: the relative phase of the driving signals to the respective transistor pairs.
1777 Citations
26 Claims
- 1. An electrosurgical generator for supplying radio frequency power to an electrical instrument, the generator comprising a radio frequency output stage having at least a pair of electrosurgical output lines for the delivery of radio frequency power to the instrument, a power supply coupled to the output stage for supplying power to the output stage, and control circuitry including sensing means for deriving a sensing signal representative of the radio frequency peak output voltage developed across the output lines, wherein the output stage comprises a series-resonant output circuit coupled to the output lines and switching means coupled to the resonant output circuit, and wherein the control circuitry is operable to vary the switching intervals of the switching means to reduce the delivered radio frequency power in response to a predetermined condition of the sensing signal.
- 17. An electrosurgical system including a generator for generating radio frequency power and an electrosurgical instrument having at least one electrode for use immersed in a conductive liquid, wherein the generator comprises an output stage including at least one radio frequency power device, a series-resonant output circuit, and at least a pair of output connections arranged to receive radio frequency power from the power device, one of the pair of connections being connected to the said electrode, and wherein the generator further comprises a control stage operable to reduce the conduction time of the power device during individual radio frequency cycles in response to a sensing signal representative of the peak output voltage across the output connections exceeding a predetermined sensing signal threshold value, whereby the radio frequency power delivered to the electrode structure is rapidly reduced when the conductive liquid is vaporised.
- 24. An electrosurgical generator for supplying radio frequency power to an electrosurgical instrument, the generator comprising a radio frequency output stage having at least a pair of electrosurgical output connections for the delivery of radio frequency power to the instrument, a radio frequency oscillator for feeding a radio frequency signal to the output stage, and control circuitry including sensing means for deriving a sensing signal representative of the radio frequency signal delivered from the output connections, wherein the output stage comprises a series-resonant output circuit coupled to the output connections, the resonant frequency of the series-resonant output circuit being different from the operation frequency of the oscillator, and wherein the control circuitry provides a feedback signal for controlling the delivered radio frequency power.
Specification