This invention relates to an electrosurge, and more particularly to an electrosurgical device which provides an unmodulated RF signal for tissue cutting procedures, and a modulated RF signal for coagulation procedures.
Electrosurge units are well known in the prior art for utilization in the field of surgery. Such units typically include an oscillator which provides an output at an RF frequency. Modulation means are included which can be selectively operated to modulate the oscillation output. With the RF energy modulated, it has been found that the output is effective in coagulating blood vessels. Without the modulation, the continuous RF signal itself is effective in cutting tissue and can be utilized as an electrosurgical device during an operating procedure. Typically, a handpiece such as a probe or forceps is utilized to apply the modulated and/or unmodulated output to the patient during an operation.
The electrosurgical units of the prior art have been described in numerous patents. One effective electrosurgical unit has been described in U.S. Pat. No. 4,051,855, assigned to the assignee of the present invention which describes an electrosurgical unit utilizing vacuum tube devices and producing an ungrounded output to avoid hazards such as burns which can occur if the patient would touch a grounded output unit.
Another electrosurge unit has been described in U.S. Pat. No. 4,092,986, also assigned to the assignee of the present invention, and which also utilizes a vacuum tube oscillator and includes a level adjustment device to provide a constant output electrosurge voltage. Still a further electrosurgical unit is described in U.S. Pat. No. 4,301,801 also assigned to the assignee of the present invention which further adds a fail-safe system to the circuit so as to disconnect the power supply to the electrosurge generator in the event of a failure at the output.
While all of these, as well as many other electrosurges, have been found effective, all these devices include a power transformer between the power supply and the electrosurge unit, where many of these devices use vacuum tubes. This power transformer provides isolation at the input of the unit as well as providing the necessary conversion of voltage needed to operate the electrosurge unit itself. With the availability of transistors, it is now possible to avoid the use of a vacuum tube oscillator. However, utilization of a power transformer has still caused transformer losses to the system which substantially reduced its efficiency. Furthermore, it has increased the size, cost and weight of the unit, and made it both bulky and awkward in design.
It is noted, that in order to market the electrosurgical devices, these devices must have the ability to withstand the conventional UL/C.S.A. 2500 volt dielectric strength test, which is well known in the art.