Pulse control circuit for electrosurgical units

• US 3,923,063 A
• Filed: 07/15/1974
• Issued: 12/02/1975
• Est. Priority Date: 07/15/1974
• Status: Expired due to Term

• Current Assignee: MDT Incorporated, Santa Barbara Research Center Goleta CA
• Original Assignee: Stanley Woltosz, Stephen William Andrews
• Inventors: Andrews, Stephen William, Woltosz, Stanley
• Primary Examiner(s): Gaudet, Richard A.
• Assistant Examiner(s): Cohen, Lee S.
• Application Number:
  US05/488,281
• Time in Patent Office: 505 Days
• Field of Search: 128/303.14,303.13,303.17,303.18,21P
• US Class Current: 606/38
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00726 Duty cycle

Abstract

A control circuit for electrosurgical units establishes a particular output signal to patient electrodes in response to condition of the patient electrodes. The duty cycle of the output signal is reduced when the patient electrodes are not in contact with the patient so as to prevent unwanted cutting and the duty cycle is increased when both patient electrodes are in contact with the patient so as to maximize the coagulation effect.

Claims

1. In combination with an electrosurgical unit having a plurality of patient electrodes and RF generating means for providing an output voltage across said electrodes, a pulse control circuit connected to said electrosurgical unit for pulse modulating said output signal and controlling the duty cycle of said pulse modulated output signal applied to said plurality of patient electrodes, said pulse control circuit comprising:

voltage circuit means for sampling the magnitude voltage between said patient electrodes;

threshold circuit means for generating a threshold signal when the magnitude of said voltage between said patient electrodes exceeds a predetermined level, and modulator circuit means for pulse modulating said output signal at a first duty cycle in the absence of said threshold signal and at a second duty cycle in response to said threshold signal.

2. A pulse control circuit as defined with claim 1 which further includes:

control circuit means for producing a control signal; and

enabling circuit means interposed between said threshold circuit means and said modulating circuit means, said enabling circuit means being in communication with said control circuit means and responsive to said control signal for connecting said threshold signal with said modulating circuit means.

3. A pulse control circuit as defined in claim 1 wherein, said voltage circuit means includes two capacitors connected in series between said patient electrodes.

4. A pulse control circuit as defined in claim 1 wherein said modulator circuit means includes:

a transistor, and sawtooth generating means for supplying a periodic sawtooth signal to said transistor, said transistor also being coupled with said threshold circuit means whereby the conductive state of said transistor is determined by said sawtooth signal and said threshold signal;

wherein said electrosurgical unit includes RF signal amplifier means connected to said transistor and controlled as said transistor so that when said transistor is conductive said RF signal amplifier means is operative.

5. A pulse control circuit as defined as claim 1 wherein said first duty cycle is higher than said second duty cycle.