APPARATUS FOR ESU LEAKAGE CURRENT CONTROL AND RELEVANT METHOD

摘要

An apparatus (10) and method to find leakage due to tissue load or transients at the start or end of electrosurgery. Active and return electrodes (11 and 16) between a patient and an ESU (13) pass RF energy sensed by inductive transformers (17 and 19). A circuit finds leakage at more than two thousand times per second; that frequency depends on the phase shift (23) between voltage and current. Software and feedback (26) manage RMS voltage to reduce the peak voltage of the output wave or increase the crest factor by pulse width modulation of the RF drive. Phase shift (23) changes of the active and return current signals (18 and 20) and peak voltage and current are found. The phase angle theta is compared to a threshold and if greater than the frequency at which the differences (22) between the active and return current signals (18 and 20) are examined is increased. The differences (22) between the active and return current signals (18 and 20) are examined and if greater than a maximum for leakage while the mode selected is in coagulation then the pulse width of the RF drive is reduced to hold voltage wave-form peaks at a predetermined value while the RMS voltage is reduced to lower the leakage to a maximum or the frequency at which the leakage current is calculated is held to a maximum level until the phase angle theta is smaller than the threshold. If the difference (22) is greater than a maximum for leakage while the mode is cut or bipolar then the Vrms is reduced to a maximum level or the level remains high until the phase angle theta is smaller than a threshold. The crest factor is increased by reducing the duty cycle or the pulse width of the output wave shape.