Phillip Hardwick
Electrician at Uvalda St, Denver, CO

4727874, Mar 1, 1988

Sep 10, 1984

6/649261

William J. Bowers - Aurora CO
Phillip D. Hardwick - Aurora CO

C. R. Bard, Inc. - Murray Hill NJ

A61B 1739

12830313

A pulse width modulation technique regulates the output power of each cycle of a radio frequency surgical signal of an electrosurgical generator. The delivered power of the surgical signal is determined by multiplying the sensed current and the sensed voltage of the surgical signal. An error signal is established by the difference of the actual delivered power with respect to a selected desired output power. The error signal is operatively utilized to modulate the pulse width of each driving pulse which creates the cycles of the surgical signal. Limits on the sensed voltage and sensed current signals are established to limit the output characteristics of the surgical signal. A minimum current limit signal is utilized to limit the maximum output voltage into relatively high impedances. A minimum voltage limit signal is utilized to limit the maximum output current into relatively low impedances. Very rapid response times and very effective power regulation even into relatively high impedance tissues are possible with the pulse width modulation technique.