| 摘要 |
An electrosurgical generator for supplying RF power to an electrosurgical instrument for cutting or vaporising tissue has an RF output stage (42) with an RF power bridge (Q1, Q2, Q3, Q4), a pair of output lines (74) and a serie s- resonant output network (48). The output impedance of the output stage (42) at the output lines (74) is less than 200/.sqroot.P ohms, where P is the maximu m continuous RF output power of the generator. The generator offers improved cutting and vaporising performance, especially in relation to the reliabilit y with which an arc can be struck when presented with an initial low impedance load. Overloading of the output stage is prevented by rapidly operating protection circuitry responsive to a predetermined electrical condition such as a substantial short-circuit across the output lines. In the preferred embodiment, the output stage is capable of maintaining output pulses at leas t 1kW peak by supplying the power bridge from a large reservoir capacitor (60) . Pulsing is dynamically variable in response to load conditions by controllin g the maximum energy per pulse in response to the reservoir capacitor voltage.
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