Electrosurgical unit with regulated output

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention in general relates to electrosurgery, and in particular to an electrosurgical unit having a regulated power output.

2. Description of the Prior Art

Electrosurgical generators which produce high frequency electric currents used for cutting of tissue and coagulation of small blood vessels have been well-known for several generations. Since the amount of cutting or coagulation performed is related to the voltage and power output of the generator, it is also known that it is desirable that the output signal of the generator be regulated. By a regulated output signal it is meant that the signal is controlled so that the fluctuations in the line input voltage do not substantially affect the power output. By substantially, it is meant that the output voltage is sufficiently regulated so that differences in cutting or coagulation are not noticable by the surgeon for normal fluctuation levels within conventional AC voltage lines.

The most common manner of obtaining a regulated output is through the use of regulated power supplies. U.S. Pat. No. 3,963,030 issued David W. Newton, discloses a feedback circuit for regulating the output of an electrosurgical generator. This feedback circuit includes a current sensor which senses the current and the output circuitry and a comparator which compares the output voltage to a reference voltage and which then adjusts the amplifier to account for variations in the amplified signal. Since fluctuations in the amplified signal are proportional to the fluctuations of the supply voltage, this method provides the desired regulation. See also U.S. Pat. No. 4,092,986 issued to Max Schneiderman.

The prior art means for regulating the output of an electrosurgical unit have several disadvantages. A regulated power supply is relatively expensive, bulky, consumes significant electrical energy and produces significant heat. These disadvantages are especially accented when a high output supply, such as the supply used for the power output stages of an electrosurgical generator, are regulated. Since under actual use the output of an electrosurgical unit varies with changing conditions at or between its electrodes, any easily measured output parameter will also vary. For example, the voltage will change with the change in resistance between the electrodes. Thus such output parameters are not generally indicative of the variations in line voltage. As a result the feedback type of circuitry is not as reliable and effective as a feedforward compensated power supply. Moreover, oscillations can occur in output parameters that are controlled by feedback loops.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an electrosurgical generator having a regulated power output that is simpler and more efficient than prior art regulated electrosurgical generators.

It is a further object of the invention to provide an electrosurgical unit that utilizes feedforward circuitry. By feedforward circuitry, it is meant that the voltage fluctuations within the electrosurgical unit are sensed or sampled at a point in the circuitry of the electrosurgical generator that is before (with respect to the direction of current flow) the point at which the power is regulated.

It is a further object of the present invention to provide an electrosurgical generator which meets one or more of the above objects and in which the electrical components that provide the regulation are also components of the amplifier; that is, the amplifier components perform double duty, thus making the design less expensive and simpler.

It is a further object of the invention to provide one or more of the above objects in an electrosurgical unit in which the regulating circuitry accounts for any non-linearity in the amplifier.

It is another object of the invention to provide one or more of the above objects in an electrosurgical unit in which a digital microprocessor controls the electrosurgical output signal.

It is yet another object of the invention to provide a power regulated electrosurgical unit in which the regulation circuitry consumes a minimum amount of electrical energy, thus reducing the heat generated by the system and making the system more acceptable in the surgical environment.

The invention provides an electrosurgical unit comprising a power source, a feedforward means responsive to voltage fluctuations at the power source for producing a regulation signal, and an amplifier means responsive to the regulation signal for producing an electrosurgical output signal that is substantially independent of the voltage fluctuations of the power source. Preferably the feedforward means includes an optoisolator. In another aspect of the invention, preferably the feedforward means includes a microprocessor. In one preferred embodiment of the invention the amplifier means includes a means for pulse modulating the electrosurgical output signal and the feedforward means comprises a means for providing a signal for regulating the duty cycle of the modulated output. In another preferred embodiment of the invention, the feedforward means comprises a means for storing a predetermined signal representative of a desired voltage, and a means responsive to the voltage fluctuations of the source and to the predetermined signal for producing the regulation signal.

In another aspect of the invention, the invention provides an electrosurgical unit comprising a power source, an amplifier means electrically connected to the power source for producing an electrosurgical output signal, and a means for regulating the output signal comprising a means for storing a predetermined signal representative of a desired output signal, and a means responsive to the predetermined signal and to the voltage fluctuations of the power source for regulating the output signal.

In a further aspect of the invention, the invention provides an electrosurgical unit comprising a power source, an amplifier means electrically connected to the power source for producing and electrosurgical output signal, the amplifier including a means for regulating the output signal which includes a means for adjusting for non-linearities in the amplifier. Preferably the means for adjusting includes an optoisolator.

In yet another aspect, the invention provides a power source, a means for storing a predetermined first digital signal representative of a desired output signal, a means for providing a second digital signal representative of an operating characteristic of said unit, and a means communicating with said power source and said means for storing and responsive to said first and second signals for producing said desired output signal.

Numerous other aspects, features, objects and advantages of the invention will now become apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1C are a block diagrammatic illustration of a preferred embodiment of the invention; the full electrosurgical unit may be seen by placing FIG. 1A on the left, FIG. 1B in the center and FIG. 1C on the right, in which positions the interconnections between the Figs. are evident;

FIG. 2 shows an electrical circuit diagram of the basic hybrid cascode amplifier according to the invention;

FIG. 3 is a detailed electrical schematic of the hybrid cascode power amplifier of the preferred embodiment of the invention shown in FIG. 1C;

FIG. 4 is a detailed circuit electrical schematic of the output stage of the embodiment of the invention shown in FIG. 1C;

FIG. 5 shows the core of the bipolar transformer utilized in the embodiment of FIG. 4;

FIG. 6 illustrates the method of winding the primary winding on the core of FIG. 5;

FIG. 7 shows the method of winding of the secondary winding on the core of FIG. 5;

FIG. 8 is a partial sectional view of the monopolar transformer utilized in the embodiment of FIG. 4;

FIG. 9 is an external view of the transformer of FIG. 8;

FIG. 10 is a partial sectional end view of the transformer of FIG. 9;

FIG. 11 is a detailed electrical schematic of a portion of the Power Supply of the embodiment of the invention in FIG. 1A;

FIG. 12 is the power-on reset circuitry of the embodiment of the invention shown in FIG. 1A;

FIG. 13 is a detailed electrical schematic of the lamp/relay register of the embodiment of the circuitry shown in FIG. 1A;