Electrosurgical generator with high-frequency pulse width modulated feedback power control

An electrosurgical generator which supplies a surgical signal having a series of substantially sinusoidually shaped cycles occurring at a fixed predetermined radio frequency, comprising:

• drive means for creating a periodic series of driving pulses occurring at a predetermined frequency related to the predetermined radio frequency of the surgical signal, each driving pulse having a predetermined energy content related to the time width of the driving pulse;
• surgical signal creating means receptive of the driving pulses for creating the surgical signal from the driving pulses, said creating means creating each cycle of the surgical signal from at least one corresponding driving pulse, said creating means further establishing an energy content of each cycle of the surgical signal in a direct relationship to the energy content of each corresponding driving pulse from which the cycle of the surgical signal was created;
• means responsive to the surgical signal and operative for creating a delivered power signal related to the power content of the surgical signal;
• means for establishing a desired output power signal related to a desired amount of output power for the surgical signal;
• and
• means receptive of the delivered power signal and the desired output power signal and operative for modulating the width of the driving pulses in accordance with a predetermined relationship of the delivered power signal and the desired output power signal to regulate the power content of the surgical signal.

An electrosurgical generator which supplies a predetermined surgical signal to perform a surgical procedure and which regulates the power content of the surgical signal, the surgical signal being a series of individual cycles occurring at a predetermined radio frequency, said generator comprising:

• drive means for creating a drive signal defined by a periodic series of driving pulses occurring at a predetermined frequency and time relationship with respect to each cycle of the radio frequency surgical signal, each driving pulse having a predetermined energy content related to the time width of the driving pulse;
• surgical signal creating means receptive of the driving pulses for creating the surgical signal from the driving pulses, said creating means creating each cycle of the surgical signal from at least one corresponding driving pulse, said creating means further establishing an energy content of each cycle of the surgical signal in a direct relationship to the energy content of each corresponding driving pulse from which the cycle of the surgical signal was created;
• means for creating a current delivered signal related to the RMS current of the surgical signal;
• means for establishing a current limit signal;
• voltage limit means receptive of the current limit signal and the current delivered signal and operative for supplying a first signal corresponding to one of either the current limit signal or the current delivered signal, said voltage limit means operatively supplying the current delivered signal as the first signal when the current delivered signal is greater than the current limit signal and operatively supplying the current limit signal as the first signal when the current delivered signal is less than the current limit signal;
• means for creating a voltage delivered signal related to the RMS voltage of the surgical signal;
• means for establishing a voltage limit signal;
• current limit means receptive of the voltage limit signal and voltage delivered signal and operative for supplying a second signal corresponding to one of either the voltage limit signal or the voltage delivered signal, said current limit means operatively supplying the voltage delivered signal as the second signal when the voltage delivered signal is greater than the voltage limit signal and operatively supplying the voltage limit signal as the second signal when the voltage delivered signal is less than the voltage limit signal;
• multiplier means receptive of the first and second signals and operative for multiplying the first and second signals to create a delivered power signal which is the product of the first and second signals;
• means for supplying a desired output power signal representative of a predetermined amount of power which the surgical signal is desired to contain;
• differential means receptive of the delivered power signal and the desired output power signal and operative for creating an error signal representative of the difference of the delivered power signal with respect to the desired output power signal;
• and
• modulation means receptive of the error signal and operative for controlling said drive means to modulate the width of each driving pulse in a predetermined relation to the error signal, said modulation means operatively changing the predetermined energy content of each driving pulse to regulate the energy content of each cycle of the surgical signal to a level related to the power level represented by the desired output power signal.