Crest factor

Abstract: Apparatus and method find leakage due to tissue load or transients and has active and return electrodes for RF energy sensed by transformers for a circuit that finds leakage at more than two thousand times per second or a frequency dependent on the phase shift between voltage and current. Software and feedback manage V rms to reduce the voltage or increase the crest factor, which is V rms divided by peak voltage, by pulse width modulation of the RF drive. Voltage and current phase shift changes, angle θ, are compared to a threshold, and when greater, the frequency at which the differences between the active and return current signals are examined is increased. The differences between the active and return currents are examined and when greater than maximum leakage while in coagulation mode, the RF drive pulse width is reduced to maintain voltage wave peaks at a preset value and reduce V rms thereby reducing leakage to the allowable maximum. Reducing the duty cycle or the pulse width of the output wave increases the crest factor. When the differences between active and return currents are greater than a maximum for leakage while in cut or bipolar mode, the V rms is reduced to limit leakage to a maximum level. When the phase angle θ is less than a threshold, the frequency with which leakage is examined is reduced.

Abstract: Methods and apparatus are provided for use in performing electrosurgery, wherein a power supply supplies an electrosurgical instrument with a low voltage power signal having a substantially constant peak-to-peak voltage that is independent of the load impedance and which has a crest factor near unity. A power supply is provided to supply a voltage waveform in accordance with the methods of the invention. A clipping circuit is also provided to permit practice of the methods using conventional electrosurgcial generators and previously known electrosurgical instruments, wherein the voltage amplitude and waveform is modified to the desired regime.

Abstract: Using some results from the recent mathematics literature, we show how to generate signals with perfect low-pass or bandpass spectra which have very low crest factors (under 6 dB). An application to multitone frequency response testing is given.

Abstract: A method for controlling an electrosurgical generator includes generating at least one electrosurgical waveform at a selected energy setting through an RF output stage comprising an RF inverter coupled to a power source. The at least one electrosurgical waveform has a duty cycle and a crest factor. The method also includes adjusting a repetition rate of the at least one electrosurgical waveform based on the selected energy setting to regulate the duty cycle of the at least one electrosurgical waveform. The method also includes applying the at least one electrosurgical waveform to tissue through at least one electrode and measuring an output voltage of the at least one electrosurgical waveform. The method also includes supplying a control signal to the RF inverter based on the repetition rate when the output voltage is increasing to regulate the crest factor of the at least one electrosurgical waveform.