Abstract:
A method for minimizing current draw on a power source for an electrosurgical system includes the step of generating a first pulse signal from a master device to electrically cooperate with a first floating power supply configured to create an electrical connection between one or more first loads and a power supply. The method also includes the step of triggering an ensuing pulse signal from a slave device based on the first pulse signal to electrically cooperate with a subsequent floating power supply configured to create an electrical connection between one or more subsequent loads and the power supply.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an electrosurgical system and method and, more particularly, to pulse sequencing to minimize current draw on a shared power supply. 
     2. Background of the Related Art 
     Energy-based tissue treatment is well known in the art. Various types of energy (e.g., electrical, ohmic, resistive, ultrasonic, microwave, cryogenic, laser, etc.) are applied to tissue to achieve a desired result. Electrosurgery involves application of high radio frequency electrical current to a surgical site to cut, ablate, coagulate or seal tissue. In monopolar electrosurgery, a source or active electrode delivers radio frequency energy from the electrosurgical generator to the tissue and a return electrode carries the current back to the generator. In bipolar electrosurgery, one of the electrodes of the hand-held instrument functions as the active electrode and the other as the return electrode. The return electrode is placed in close proximity to the active electrode such that an electrical circuit is formed between the two electrodes (e.g., electrosurgical forceps). In this manner, the applied electrical current is limited to the body tissue positioned between the electrodes. 
     Typically, multiple isolated power supplies are connected to the active terminals of the electrosurgical generator to power analog circuits associated with components connected to the electrosurgical generator (e.g., bipolar instruments, monopolar instruments, footswitches, etc.). For example, analog circuits configured to detect connected components and/or switching thereof may be included within the generator or within the connected components. Often, these isolated power supplies share the same low voltage power source. This is problematic when multiple supplies draw power from the shared power source substantially simultaneously, thereby maximizing the peak current draw on the shared power source. For example, the combined primary currents generated by certain isolated power supplies activated substantially simultaneously may be large enough to cause a decrease in output of the shared power source due to its output impedance or internal resistance. This decrease in output may cause output noise on the analog circuits drawing power therefrom, if those analog circuits do not have adequate power supply rejection bandwidth at the switching frequency of the isolated power supply to which they are connected. 
     SUMMARY 
     According to an embodiment of the present disclosure, a method for minimizing current draw on a power source for an electrosurgical system includes the step of generating a first pulse signal from a master device to electrically cooperate with a first floating power supply configured to create an electrical connection between one or more first loads and a power supply. The method also includes the step of triggering an ensuing pulse signal from a slave device based on the first pulse signal to electrically cooperate with a subsequent floating power supply configured to create an electrical connection between one or more subsequent loads and the power supply. 
     According to another embodiment of the present disclosure, a method for minimizing current draw on a power source for an electrosurgical system includes the steps of generating a first pulse signal and activating a first floating power supply based on the first pulse signal. The first floating power supply is configured to deliver power from a power source to one or more first loads. The method also includes the steps of generating a second pulse signal based on the first pulse signal and activating a second floating power supply based on the second pulse signal. The second floating power supply is configured to deliver power from the power source to one or more second loads. The method also includes the steps of generating an ensuing pulse signal based on a previously generated pulse signal and activating a subsequent floating power supply based on the ensuing pulse signal. The subsequent floating power supply is configured to deliver power from the power source to one or more additional loads. 
     According to another embodiment of the present disclosure, an electrosurgical system includes an electrosurgical generator adapted to supply electrosurgical energy to tissue and a power source operably coupled to the electrosurgical generator and configured to deliver power to one or more loads connected to the electrosurgical generator. The system also includes a master device configured to generate an initial pulse signal. The initial pulse signal electrically cooperates with a first floating power supply configured to create an electrical connection between one or more first loads and the power source. A plurality of slave devices are connected in series to the master device. A first slave device is configured to generate a subsequent pulse signal based on the initial pulse signal. The subsequent pulse signal electrically cooperates with a second floating power supply configured to create an electrical connection between one or more second loads and the power source. The subsequent pulse signal is configured to cause an ensuing slave device to generate an additional pulse signal. The additional pulse signal electrically cooperates with a corresponding floating power supply configured to create an electrical connection between at least one additional load and the power source. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the present disclosure are described herein with reference to the drawings wherein: 
         FIG. 1A  is a schematic block diagram of a monopolar electrosurgical system in accordance with an embodiment of the present disclosure; 
         FIG. 1B  is a schematic block diagram of a bipolar electrosurgical system in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a schematic block diagram of a generator in accordance with an embodiment of the present disclosure; 
         FIG. 3  is a schematic block diagram of specific components of the generator of  FIG. 2  in accordance with an embodiment of the present disclosure; and 
         FIG. 4  is a circuit diagram of a power supply according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. 
     The generator according to the present disclosure can perform monopolar and bipolar electrosurgical procedures, including vessel sealing procedures. The generator may include a plurality of outputs for interfacing with various electrosurgical instruments (e.g., a monopolar active electrode, return electrode, bipolar electrosurgical forceps, footswitch, etc.). Further, the generator includes electronic circuitry configured for generating radio frequency power specifically suited for various electrosurgical modes (e.g., cutting, blending, division, etc.) and procedures (e.g., monopolar, bipolar, vessel sealing). 
       FIG. 1A  is a schematic illustration of a monopolar electrosurgical system according to one embodiment of the present disclosure. The system includes an electrosurgical instrument  2  (e.g., monopolar) having one or more electrodes for treating tissue of a patient P (e.g., electrosurgical cutting, ablation, etc.). More particularly, electrosurgical RF energy is supplied to the instrument  2  by a generator  20  via a supply line  4 , which is connected to any one of a plurality of active terminals  30   a ,  30   b ,  30   c , . . .  30   m  (see  FIG. 2 ) of the generator  20 , allowing the instrument  2  to coagulate, seal, ablate and/or otherwise treat tissue. The energy is returned to the generator  20  through a return electrode  6  via a return line  8  at a return terminal  32  (see  FIG. 2 ) of the generator  20 . The active terminals  30   a ,  30   b ,  30   c , . . .  30   m  and the return terminal  32  are connectors configured to interface with plugs (not explicitly shown) of the instrument  2  and the return electrode  6 , which are disposed at the ends of the supply line  4  and the return line  8 , respectively. 
       FIG. 1B  is a schematic illustration of a bipolar electrosurgical system according to the present disclosure. The system includes a bipolar electrosurgical forceps  10  having one or more electrodes for treating tissue of a patient P. The electrosurgical forceps  10  includes opposing jaw members  11  and  13  having an active electrode  14  and a return electrode  16 , respectively, disposed therein. The active electrode  14  and the return electrode  16  are connected to the generator  20  through cable  18 , which includes the supply and return lines  4 ,  8  coupled to the active terminals  30   a ,  30   b ,  30   c , . . .  30   m  and return terminal  32 , respectively (see  FIG. 2 ). The electrosurgical forceps  10  is coupled to the generator  20  at a connector  21  having connections to the active terminals  30   a ,  30   b ,  30   c , . . .  30   m  and return terminal  32  (e.g., pins) via a plug disposed at the end of the cable  18 , wherein the plug includes contacts from the supply and return lines  4 ,  8 . 
     The generator  20  includes suitable input controls (e.g., buttons, activators, switches, touch screen, etc.) for controlling the generator  20 . In addition, the generator  20  may include one or more display screens for providing the user with variety of output information (e.g., intensity settings, treatment complete indicators, etc.). The controls allow the user to adjust power of the RF energy, waveform parameters (e.g., crest factor, duty cycle, etc.), and other parameters to achieve the desired waveform suitable for a particular task (e.g., coagulating, tissue sealing, intensity setting, etc.). 
       FIG. 2  shows a schematic block diagram of the generator  20  having a controller  24 , a DC power supply  27 , and an RF output stage  28 . The power supply  27  is connected to a conventional AC source (e.g., electrical wall outlet) and includes a low voltage power supply  29  (“LVPS”) and a high voltage power supply (not explicitly shown). The high voltage power supply provides high voltage DC power to an RF output stage  28 , which then converts high voltage DC power into RF energy. RF output stage  28  delivers the RF energy to the plurality of active terminals  30   a ,  30   b ,  30   c , . . .  30   m  separately through a single-input multiple output multiplexer  35 . The energy is returned thereto via the return terminal  32 . The LVPS  29  provides power to various components of the generator (e.g., input controls, displays, etc.), as will be discussed in further detail below. 
     The generator  20  may include a plurality of connectors to accommodate various types of electrosurgical instruments (e.g., instrument  2 , electrosurgical forceps  10 , etc.). Further, the generator  20  may be configured to operate in a variety of modes such as ablation, monopolar and bipolar cutting coagulation, etc. The generator  20  may also include a switching mechanism (e.g., relays) to switch the supply of RF energy between the connectors, such that, for example, when the instrument  2  is connected to the generator  20 , only the monopolar plug receives RF energy. 
     The controller  24  includes a microprocessor  25  operably connected to a memory  26 , which may be volatile type memory (e.g., RAM) and/or non-volatile type memory (e.g., flash media, disk media, etc.). The microprocessor  25  includes an output port that is operably connected to the power supply  27  and/or RF output stage  28  allowing the microprocessor  25  to control the output of the generator  20  according to either open and/or closed control loop schemes. Those skilled in the art will appreciate that the microprocessor  25  may be substituted by any logic processor (e.g., control circuit) adapted to perform the calculations discussed herein. 
     A noise reduction circuit  40  is operably coupled to the controller  24  and is configured to control power drawn on the LVPS  29  by one or more isolated floating power supplies  50 ,  52 ,  54 , . . . “m”. Each supply  50 ,  52 ,  54  . . . “m” may be an isolated power converter such as, for example, a so-called “flyback converter” electrically connected to the LVPS  29  and configured to power a load  51 ,  53 ,  55 , . . . “x”, respectively (see  FIG. 3 ). Load  51 ,  53 ,  55 , . . . “x” may be, for example, one or more low-signal-level analog circuits configured to detect switching of a handset (e.g., instrument  2 , forceps  10 , etc.) connected to one of the plurality of connectors of generator  20  and/or drawing energy from RF output stage  28  via any one of active terminals  30   a ,  30   b ,  30   c , . . .  30   m . As shown in the illustrated embodiment of  FIG. 2 , supplies  50 ,  52 ,  54 , . . . “m” float at corresponding active terminals  30   a ,  30   b ,  30   c , . . .  30   m  and share the same low voltage power source (e.g., LVPS  29 ). This is problematic when multiple supplies draw power from LVPS  29  substantially simultaneously, thereby maximizing the peak current draw from LVPS  29 . In the scenario wherein supplies  50 ,  52 ,  54 , . . . “m” are embodied as flyback converters, for example, the combined primary currents generated by flyback converters activated substantially simultaneously may be large enough to cause a drop in output of LVPS  29  due to the output impedance or internal resistance of LVPS  29 . This drop in output of LVPS  29  may cause output noise on circuits (e.g., load  51 ,  53 ,  55 , . . . “x”) drawing power therefrom especially if those circuits do not have adequate power supply rejection bandwidth at the switching frequency of the power supply (e.g., supplies  50 ,  52 ,  54 , . . . “m”). 
       FIG. 3  shows a circuit schematic of the noise reduction circuit  40 . Noise reduction circuit  40  includes a master device  42  and one or more slave devices  44 ,  46 , . . . “n” connected in series therewith. Master device  42  and each of slave devices  44 ,  46 , . . . “n” may be an integrated circuit such as, for example, a 555 timer having an RC network (not shown). In a so-called “monostable mode,”  555  timers act as a “one-shot” pulse generator. The one-shot pulse initiates when the 555 timer receives a trigger signal (e.g., a one-shot pulse from a previous 555 timer). Upon receiving the trigger signal, the 555 timer outputs the one-shot pulse as a function of a time constant of the RC network. In a scenario wherein a 555 timer is sequenced or chained to ensuing 555 timers, this configuration has the effect of each ensuing 555 timer receiving, as input, a one-shot pulse generated by the previous 555 timer to trigger a one-shot pulse output as a function of the time constant. That is, for a given 555 timer, a time delay exists between the reception of a trigger pulse and an output pulse as dictated by the time constant of the RC network of that 555 timer. In this manner, the one-shot pulses generated by a chain of 555 timers are sequenced or chained in accordance with the time constant of the RC network for each 555 timer, thereby minimizing the peak current draw on the common power source (e.g., LVPS  29 ) to which they are connected. 
     With this scenario in mind, master device  42  is configured to generate a pulse signal (e.g., a master switching frequency) that operates to cause a load  51  connected to supply  50  to draw power from LVPS  29 . The pulse signal generated by master device  42  triggers slave device  44  to subsequently generate a one-shot pulse, as discussed above with respect to monostable mode of operation for a 555 timer, that operates to cause a load  53  connected to supply  52 , to draw power from LVPS  29 . Further, the one-shot pulse generated by slave device  44  triggers ensuing slave device  46  to generate a one-shot pulse that operates to cause a load  55  connected to supply  54  to draw power from LVPS  29 . Further, the one-shot pulse generated by slave device  46  triggers an ensuing slave device “n” to operate in like manner to the previous slave devices  44  and  46 . That is, each ensuing slave device “n” connected in series with master device  42  is configured to receive a triggering one-shot pulse from a previous slave device “n- 1 ” and, in turn, subsequently generate a one-shot pulse to cause a load “x” connected to an ensuing supply “m” to draw power from LVPS  29 . In this manner, a sequenced or chained activation of supplies  50 ,  52 ,  54 , . . . “n” (as opposed to substantially simultaneous activation thereof), minimizes the peak current draw on LVPS  29 . This, in turn, minimizes output noise on loads  51 ,  53 ,  55 , . . . “x” connected to supplies  50 ,  52 ,  54 , . . . “n”, respectively, as discussed hereinabove. 
     In other embodiments, each of slave devices  44 ,  46 , . . . “n” may be a so-called “tapped delay line” configured to simulate an echo of a source signal generated by master device  42  to sequentially activate supplies  50 ,  52 ,  54 , . . . “n”. 
     By way of example,  FIG. 4  illustrates a circuit diagram of a flyback converter  70  including a transformer  60  having a primary winding  61   a  and a secondary winding  61   b . Primary winding  61   a  is connected in series with a switching component  68  (e.g., a transistor). Secondary winding  61   b  is connected in series with a diode  62 , both of which are in parallel with a capacitor  64  and a load  66  (e.g., analog circuit). In operation, a pulse signal generated by master device  42 , or any one of ensuing slave devices  42 ,  44 ,  46 , . . . “n”, closes or turns on switching component  68 . When switching component  68  is on or closed, the primary coil  61   a  of inductor  60  is directly connected to the LVPS  29 , resulting in an increase of magnetic flux in the transformer  60  and a positive voltage across the secondary winding  61   b  of transformer  60 . This positive voltage across the secondary winding  61   b  causes diode  62  to be forward-biased and, as a result, the energy stored in transformer  60  is transferred to the capacitor  64  and/or the load  66 . When the switching component  68  is off or open, as shown in  FIG. 4 , the transformer  60  induces a negative voltage across secondary winding  61   b  sufficient to cause diode  62  to be reverse-biased (or blocked) and, as a result, the capacitor  64  supplies energy to the load  66 . 
     While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.