High-frequency surgical instrument

A high-frequency electrosurgical apparatus, said apparatus for producing a high-frequency current for the monopolar cutting or coagulating of biological tissue, said tissue being capable of conducting a low-frequency current which may be produced by one or more low-frequency current sources connected to said tissue or by said electrosurgical apparatus, said apparatus comprising:

• A. transformer means having a primary winding and a secondary winding, each of said primary and secondary windings having first and second teminals;
• B. high-frequency generator means coupled to the first and second terminals of said primary winding;
• C. active electrode means coupled to the first terminal of said secondary winding;
• D. neutral electrode means coupled to the second terminal of said secondary winding, at least one of said active electrode means and said neutral electrode means being coupled by a capacitor to its respective terminal;
• E. current sensing means, said sensing means being connected to provide a conductive path between said second terminal of said secondary winding and ground potential, said sensing means for monitoring said low-frequency current and producing a signal indicative of the magnitude thereof;
• F. first switch means, connected in said conductive path, said first switch means operating to alternately open and close said conductive path in response to a control signal;
• and
• G. control means, coupled to said sensing means, said control means for comparing the signal produced by the sensing means to a preselected reference signal and producing said control signal in response to the difference therebetween.