Abstract:
A brush-to-brushless motor controller adapter for use with a two-wire output signal from a medical console consists of a small enclosure containing a circuit board and has a short cable terminating in a two-wire connector which plugs into the two-wire controller output of the medical console and a connector jack for an electrical connection to a surgical instrument having a brushless D.C. motor. The brush-to-brushless motor controller generates a stable voltage for the adapter internal electronics (i.e., 12 to 15 volts), from a varying input voltage (i.e., 2.5 to 30 volts D.C.). The surgical instrument brushless D.C. motor speed is controlled as a function of the console output signal drive voltage amplitude and the adapter accepts pulsed inputs from a high power two-wire motor controller (e.g., 10 watts and up). The adapter accepts bipolar drive signals and is adapted to reverse the surgical instrument brushless D.C. motor direction in response to a change in input voltage polarity from the two-wire medical console controller circuit. The adapter circuit of the present invention eliminates the need for a negative supply voltage by creating a positive bias in the control loop such that the control signal is nominally 2.5V above ground (i.e., zero volts) and the adapter internal positive voltage supply level. The adapter may be calibrated to provide a given top motor speed for different consoles by adjusting speed gain and speed offset voltages and so can work with consoles having different maximum speed voltage signals. The instrument including the brushless D.C. motor is preferably, but not necessarily, a surgical instrument such as a shaver or resector and may be used in conjunction with ancillary equipment such as a selectively switchable pump.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for connecting a surgical instrument to a medical console and, more particularly, to an electrical adapter for connecting a new surgical instrument having a brushless direct current (D.C.) motor to an existing medical console having a two-wire controller designed for connection to brushes in a commutated D.C. motor. 
     2. Discussion of the Related Art 
     Brushless D.C. motors are becoming commonplace in many medical applications, especially ear, nose and throat (ENT) surgery, due to advantages such as increased reliability, increased life expectancy and reduced radio frequency emissions or interference (RFI). Brushless motors do not include parts associated with mechanical commutation (e.g., brushes) and so arcing is eliminated. One difficulty encountered in using brushless D.C. motors in surgical instruments, such as shavers, is that many of the medical consoles presently in use in hospitals and other medical facilities have controller circuits adapted for use with two-wire, commutated D.C. motors, and replacement of existing medical consoles would require an unacceptable expense. Medical consoles with two-wire controllers apply voltage in one of two possible polarities. For a first polarity, the commutated D.C. motor spins clockwise (CW) and with the opposite polarity voltage applied, the motor spins counter clockwise (CCW). 
     Brushless D.C. motors do not have brushes to commutate the motor, and a motor controller for use with brushless D.C. motors must sense the position of the motor rotor and commutate (i.e., control the direction and position) the motor electronically. Accordingly, the brushless motor controllers of the prior art are incompatible with and more complex than the two-wire motor controllers used in the existing medical consoles. 
     In the past, the high RFI emissions associated with arcing brushes in commutated D.C. motors were of little concern to surgical instrument designers or users. In the modern ENT surgical facility, however, computers and a wide variety of wireless communications devices are employed and can be impaired by emissions from any device having poor RFI performance. As an example, new ENT stereotactic surgical imaging systems incorporate sensors and computers with little tolerance for RF emissions, and use of a surgical instrument with a commutated D.C. motor is more likely to compromise imaging system performance. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a primary object of the present invention to overcome the above-mentioned difficulties by providing an electrical adapter including an electrical circuit for electrically connecting a traditional two-wire controller (as is used in many medical consoles) to a surgical instrument having a brushless D.C. motor. 
     Another object of the present invention is providing a brush-to-brushless motor controller adapter enabling operating room personnel to use existing traditional medical consoles, thereby avoiding replacement of a familiar and expensive piece of equipment. 
     Yet another object of the present invention is to efficiently transferring power from a two-wire controller to a surgical instrument having a brushless D.C. motor, sensing the desired motor drive direction and controlling motor speed, and so avoiding excessive RFI in the surgical environment. 
     Another object of the present invention is to calibrate or adjust an adapter to accomodate various medical consoles providing various input signals. 
     The aforesaid objects are achieved individually and in combination and it is not intended that the present invention be construed as requiring two or more objects to be combined unless expressly required by the claims attached hereto. 
     The electrical adapter of the present invention permits use of a surgical handpiece having a brushless D.C. motor driving a surgical implement with a medical console of the type designed for connection to brushes in a commutated D.C. motor and, thus, provides new uses for existing consoles. A method according to the present invention includes the steps of coupling the adapter to a medical console of the type having a two-wire controller for connection to brushes in a commutated D.C. motor, connecting an output of the adapter to a brushless D.C. motor in a surgical handpiece for driving a surgical implement and controlling operation of the surgical handpiece via the medical console. 
     In accordance with the present invention, a brush-to-brushless motor controller adapter for use with a two-wire output signal from a medical console includes a small enclosure containing a circuit board. The adapter has a short cable terminating in a two-wire connector for plugging into the medical console two-wire controller output and an eight-wire connector for connection to an ENT surgical instrument, or the like, having a brushless D.C. motor. The brush-to-brushless motor controller adapter of the present invention generates a stable voltage for supplying the adapter circuit board (i.e., 12 to 15 volts), from the medical console two-wire output (i.e., a varying voltage of 2.5 to 30 volts D.C.). The ENT surgical instrument brushless D.C. motor speed and direction are controlled as a function of the medical console output signal&#39;s voltage amplitude and polarity, respectively, and the adapter can accept pulsed inputs from a high power two-wire motor controller (e.g., at ten or more watts). The adapter controller operates with as little as 2.5 volts D.C. input by employing Schottky diodes (for minimal rectifier loss), a step-up voltage converter circuit (for maintaining a stable supply voltage, even with an input voltage as low as 2.0 volts D.C.) and a MOSFET driving stage (the MOSFET&#39;s turn on with as little as 2.0 volts D.C. between the gate and source). The adapter contains all the electronics required for driving a three-phase brushless D.C. motor from a two-wire D.C. motor controller drive signal and has input filtering for operability with pulse width modulated, pulse frequency modulated or linear two-wire controller outputs. Commercially available brushless D.C. motor controller, three-phase brushless motor driver and D.C.-D.C. converter integrated circuits are employed to provide an economical adapter circuit of small size. The adapter is calibratable to provide a top brushless motor speed of 3000 RPM by adjusting &#34;full speed gain&#34; voltage and &#34;start speed offset&#34; voltage through adjustable resistors and so can accommodate and work when connected to medical consoles having different maximum speed voltage signals; for example, a first medical console may have an operating range of zero to twelve volts and a second console may have an operating range of zero to twenty-five volts. By adjusting the two calibration adjustable resistor settings, the adapter accommodates either console. 
     The adapter drive electronics transmit the entire adapter input voltage to the output drive stage P channel field effect transistors (FETs), at the gate to source junction, in order to turn on the transistors when the adapter input signal voltage is approximately 12 volts or below but reduces the gate to source drive voltage applied when the adapter input exceeds 12 volts D.C. and thus allows optimum efficiency when operating with low input voltages but limits the voltage applied to the output drive stage FET gate to source junctions to under 20 volts for adapter input voltages of up to 30 volts, an important consideration since the output drive stage P channel FETs gate-to-source junction have a maximum gate-to-source voltage (V gs ) rating of 20 volts. The adapter accepts bipolar drive signals and reverses the surgical instrument brushless D.C. motor direction in response to a change in input voltage polarity from the two-wire medical console controller circuit. The adapter circuit of the present invention eliminates the need for a negative supply voltage by creating a positive bias in the control loop such that the control signal is nominally 2.5 volts above the ground or return rail level and the adapter internal positive voltage supply rail level. Positive bias is needed in order to permit a bipolar drive signal without a negative voltage supply and so a control signal op-amp has inverting and non-inverting inputs connected between the rails (i.e., rail- to-rail) in the speed control loop of the motor controller adapter. 
     The electrical adapter of the present invention is designed for use in combination with a surgical instrument of the type having a handpiece housing a brushless D.C. motor for driving a surgical implement, such as shavers, resectors, burs and the like used in arthroscopic and ENT procedures. In addition, the adapter can be used to drive ancillary equipment such as a selectively switchable vacuum pump or irrigation pump. 
     In operation, the adapter of the present invention is connected to the two-wire controller from the console and a direction sensing circuit is used to sense the polarity of the console output and generate a direction signal. A rectifier bridge and filter are used to filter the two-wire input signal and the filtered input signal is applied to a three-phase MOSFET bridge connected directly to a surgical instrument handpiece including the brushless D.C. motor. The filtered output is also applied across an op-amp, the output of which is input to a summing circuit, along with an offset voltage, to generate a speed signal for input to a conventional three-phase motor controller circuit. The direction sensing circuit also has an input into the three-phase motor controller electronics and provides speed and direction input signals to the three-phase motor controller electronics. The three-phase motor controller electronic circuit has an output connection to the handpiece having the brushless D.C. motor. The three-phase motor controller also has an output signal selectively connectable to an auxiliary pump circuit, such that the pump can operate at a speed appropriate to operation of the brushless D.C. motor in the surgical instrument (e.g., the micro resector or shaver). 
     The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of a specific embodiment thereof, particularly when taken in conjunction with the accompanying drawings, wherein like reference numerals in the various figures are utilized to designate like components. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a functional block diagram of the electrical adapter of the present invention. 
     FIG. 2a is an overhead view in partial cross section of the adapter assembly. 
     FIG. 2b is a distal end view of the adapter housing of the present invention. 
     FIG. 2c is a distal end view of the adapter output electrical connector. 
     FIG. 2d is an internal wiring diagram of the electrical adapter of the present invention. 
     FIGS. 3a, 3b, 3c and 3d are connected segments of the electrical schematic diagram for the adapter circuit. 
     FIG. 4a is an exploded view, partly in section, of a powered handpiece for use with the adapter of the present invention. 
     FIG. 4b is a broken side view, partly in section, of a proximal portion of the handpiece and the adapter of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring specifically to FIG. 1 of the accompanying drawings, a functional block diagram illustrates a brush-to-brushless electrical motor control adapter 8 in accordance with the present invention, including an input electrical connector J1 for making a two-wire connection to a medical console 9. Medical console 9 provides a two-wire bipolar analog output and can be, for example, one of the Stryker Corp. models, such as the &#34;Hummer&#34;, the &#34;SE3&#34;, or the &#34;SE4&#34;. Adapter connector J1 receives an input signal from the medical console and includes a first conductor MTR+ and a second conductor MTR- connected to the input of a main power rectifier bridge 10, a direction sensing circuit 14 and a speed sensing circuit 16. Rectifier bridge circuit 10 is a two-port circuit having a two-wire output connected to the input of a two-port filter circuit 12. The output of filter circuit 12 are the Vbridge and RTN (return) lines connected to the inputs of the three-phase motor controller electronics integrated circuit 20, including chip 20a (e.g., U7, shown in FIG. 3c, a Motorola (TM) MC33035) and the three-phase MOSFET bridge integrated circuit chip 22 (e.g., U8, a National Semiconductor (TM) NDM3000). Direction sensing circuit 14 has a first input connection to the MTR+ line from the J1 connector and a second input connection to the MTR- line from the J1 connector and produces an output signal indicative of forward or reverse direction &#34;F/(not)R&#34;. The output signal of direction sensing circuit 14 is an input to the three-phase motor controller electronics chip 20a at pin 3 (FwdRev). 
     Speed sensing circuit 16 is part of a speed control loop and has a first input connection to the MTR+ line from the J1 connector and a second input connection to the MTR- line from the J1 connector via a half-bridge rectifier 16d providing an input to a non-inverting (+) input of a differential amplifier 16a. An offset voltage from a reference voltage source 16b is summed with the output from the differential amplifier 16a in summing circuit 16c to form the speed command output signal. The speed command output signal is input to the three-phase motor controller electronics chip 20a at pin 11 (Error Amp noninverting input). A DC to DC converter circuit 18 has first and second inputs across the output of filter 12 (i.e., the Vbridge and return lines). DC to DC converter circuit 18 produces a stable output supply voltage of approximately 12 volts for use in the adapter circuitry; the 12 volt supply is also provided to the three-phase motor controller electronics chip 20a. Three-phase motor controller electronics chip 20a is also connected to the three-phase MOSFET bridge chip 22 (U8) and to an output connector J2 for connection to an instrument having a three-phase brushless D.C. motor. Another output from the three-phase motor controller electronics chip 20a is a &#34;speed out&#34; signal provided to amplifier 24 and, via a switch 25, to a second output connector J3 for connection to an accessory such as a suction pump or the like. 
     Turning now to FIGS. 2a and 2b there is illustrated an overhead view and a side view, respectively, of a housing 40 having a cable terminated in an electrical connector, J1external, for connection to medical console 9. A first exterior output connector, J2external, is disposed on a first side wall 42 of housing 40 and is adapted for connection to a surgical instrument handpiece. A second exterior output connector, J3external, is situated on a second side wall 44 of housing 40 for connection to a suction pump or the like. In the example of FIGS. 2a and 2b, housing 40 is a box made of ABS plastic and having a removable top 46, has a wall thickness of 0.138 inches, a length of 2.52 inches, a width of 2.28 inches and a height of 1.38 inches. Preferably, at least three rubber feet 48 are disposed on the bottom surface 50 as illustrated in FIG. 2b for stability. A cable 52 is terminated in a four conductor electrical connector, J1external , is eight inches long (for example) and is attached via a strain relief fitting in a third side wall 54 and connected to circuit board 60 via another electrical connector, J1internal, on the interior of adapter housing 40. Similarly, as shown in FIG. 2a, J2internal is an internal PC board electrical connector wired to J2 external. Optional connector J3external is adapted for connection to an optional accessory, as described below, and is wired directly to the internal PC board of adapter 8. 
     Turning now to FIG. 2c, a distal end view of output connector J2external shows twelve female pin receiving sockets J2-1, J2-2, J2-3, J2-4, J2-5, J2-6, J2-7, J2-8, J2-9, J2-10, J2-11 and J2-12, wired internally as shown in the wiring diagram of FIG. 2d. Specifically, pin J2-1 of the J2external (Lemo) connector is internally wired to the J2internal (Molex) connector pin 1 and is used for conducting the brushless motor phase A drive signal. Pin J2-2 of the J2external (Lemo) connector is internally wired to the J2internal (Molex) connector pin 2 and is used for conducting the brushless motor phase B drive signal. Pin J2-3 of the J2external (Lemo) connector is internally wired to the J2internal (Molex) connector pin 3 and is used for conducting the brushless motor phase C drive signal. Pin J2-4 of the J2external (Lemo) connector is internally wired to the J2internal (Molex) connector pin 4 and is used for conducting the brushless motor hall excitation signal. Pin J2-5 of the J2external (Lemo) connector is internally wired to the J2internal (Molex) connector pin 5 and is used for conducting the brushless motor first hall sensor signal. Pin J2-6 of the J2external (Lemo) connector is internally wired to the J2internal (Molex) connector pin 6 and is used for conducting the brushless motor second hall sensor signal. Pin J2-7 of the J2external (Lemo) connector is internally wired to the J2internal (Molex) connector pin 7 and is used for conducting the brushless motor third hall sensor signal. Pin J2-8 of the J2external (Lemo) connector is internally wired to the J2internal (Molex) connector pin 8 and is used for conducting the brushless motor hall sensor return signal. Pin J2-9 of the J2external (Lemo) connector is internally wired to the J1external (Fischer) connector pin 1 and is used for conducting the motor HP sense (+) signal. Pin J2-10 of the J2external (Lemo) connector is internally wired to the J1external (Fischer) connector pin 2 and is used for conducting the motor HP sense (-) signal. Pin 3 of the J1external (Fischer) connector is internally wired to the J1 internal (Molex) connector pin 1 and is used for conducting the commutated motor (+) signal. Pin 4 of the J1external (Fischer) connector is internally wired to the J1internal (Molex) connector pin 2 and is used for conducting the commutated motor (-) signal. 
     Turning now to FIGS. 3a-3d, there is illustrated at connector J1internal line 1 and line 2 (i.e., J1:1 and J1:2) conductors for the MTR+ and MTR- input connections to main power full-wave rectifying bridge 10 including diodes D1, D2, D3 and D4. Bridge 10 is connected in cascade with active filter circuit 12 including NPN transistor Q1 connected at its base with the cathode of 27V zener diode VR1. Zener diode VR1 is connected at its anode to ground (i.e., return). The output of filter 12 is Vbridge, a voltage not exceeding 25 volts, and is taken from the emitter of transistor Q1 
     Also connected to the MTR+ and MTR- signal lines is the direction sensing circuit 14 including comparator U1. The output of direction sensing circuit 14 is the F/(not)R signal and is taken from the output of comparator U1 for connection to pin 3 (FWD/REV) of three-phase motor controller electronics chip 20a, as shown traversing FIGS. 3a and 3c; see discontinuous line B. 
     Speed sensing and control circuit 16 has inputs coupled through half bridge 16d including diode pair D5 attached to the MTR+ and MTR- lines. Differential amplifier 16a generates the input to summer circuit 16c (including op-amps U2:B, U2:C and U2:D with reference voltage source circuit 16b) for generating a speed command signal input to the three-phase motor controller electronics chip 20a at pin 11 (line &#34;D&#34; traversing FIGS. 3b and 3c). The speed of the brushless motor (not shown) is sensed and a speed feedback signal is received in the closed loop motor control integrated circuit U5 (e.g., a Motorola (TM) MC33039D) via connector J2 lines 5, 6 and 7 (i.e., J2:5, J2:6 and J2:7). The closed loop motor control (I.C. U5 generates a feedback signal for input to summer circuit 16c. The adapter speed sensing and control circuit 16 works in conjunction with adjustable resistors RT1 and RT2 (as shown in FIG. 3b). Adaptor 8 is calibratable to provide a maximum selected brushless motor speed (e.g., approximately 3000 RPM) by adjusting &#34;full speed gain&#34; voltage through adjustable resistor RT1 and &#34;start speed offset&#34; voltage through adjustable resistor RT2, and so can accommodate and work when connected to medical consoles having differing maximum speed voltage signals; for example, a first medical console may have an output signal operating range of zero to twelve volts and a second console may have an output signal operating range of zero to twenty-five volts. By adjusting the two calibration adjustable resistor (RT1, RT2) settings, adapter 8 accommodates either console. 
     Three-phase motor controller chip 20a is a subset of the three-phase motor controller electronic circuitry identified generally as 20 in the schematic in FIG. 3c. As noted above, three-phase MOSFET bridge 22 is implemented on a single integrated circuit chip U6 and comprises the three-phase adapter output for connection to the brushless motor through connector J2. 
     DC to DC converter 18 is illustrated in FIG. 3d and includes a connection to the output of filter 12, Vbridge, and includes a twelve volt, 500 mA LDO regulator U3 (e.g., a National Semiconductor (TM) LM2937ET-12) and a step-up DC to DC converter U6 (e.g., a Maxim (TM) MAX761CSA) to provide a regulated output of twelve volts DC (i.e., +12V). 
     The components of the adapter 8 are summarized in the parts list of Table 1 as follows: 
     
                                           TABLE I__________________________________________________________________________QTY   Part No.  Alt. Part No.                 Description        Reference                                             Manufacturer__________________________________________________________________________1  MBRS140T  SK14     40 V 1A SMT Schottky                                    D7       Motrla/Diodes Inc4  MBRS340T  SK34     40 V 3A SMT Schottky                                    D1-D4    Motrla/Diodes Inc4  MMBD6100LT1        Gen. Purpose Diode-dual, common cathode                                    D5, D8, D9, D10                                             Motrla/Diodes Inc3  MMBT2222ALT1       Gen. Purpose NPN transistor                                    Q3, Q5, Q7                                             Motrla/Diodes Inc3  NDS351N            N-Ch. MOSFET       Q4, Q6, Q8                                             National Semi1  PO.51W-28K        PO.47W-28K                 0.51 ohm, 5%, 2 Watt axial resistor                                    R1       Panasonic1  640456-2  22-23-2021                 2-pin header connector w/locking ramp                                    J1 internal                                             Amp/Molex1  640456-8  22-23-2081                 8-pin header connector w/locking ramp                                    J2 internal                                             Amp/Molex1  RE2-34V221M        35 V 220 uF Alum Elec Capacitor                                    C1       Elna1  742-083-R101CT-ND  100 ohm resistor array (4 isolated)                                    RP3      CTS1  3266W-1-202        3296Y-1-202                 2 k ohm trimmer, 12 or 25 turn                                    RT1      Bourns1  742-083-R332CT-ND  3.3 k ohm resistor array (4 isolated)                                    RP6      CTS1  742-163-R104CT-ND  100 k ohm resistor array (8 isolated)                                    RP2      CTS1  742-163-R105CT-ND  1 M ohm resistor array (8 isolated)                                    RP1      CTS1  742-083-R104CT-ND  100 k ohm resistor array (4 isolated)                                    RP5      CTS9  ECU-V1H104KBW        89F5965  0.1 uF ceramic chip cap X7R                                    C3, C7, C11, C15                                             Panasonic/Kemet                                    C17, C18, C21-234  ECU-V1H103KBV      0.01 uF ceramic chip cap X7R                                    C4, C5, C19, C20                                             Panasonic1  C1206C102J5GAC        93F2368  1000 pF ceramic cap (NPO)                                    C12      Kemet1  TIP122             NPN Darlington Transistor                                    Q1       Motorola3  ECU-V1H152KBV      1500 pF ceramic chip cap                                    C8, C9, C10                                             Panasonic1  MC78L05ACD        L78L05ACD                 5 Volt Regulator   U4       Motorola/SGS1  LM311D    LM311N   Comparator         U1       Motorola/TI/SGS1  LMC6494B  LM6494A  Quad Rail-to-Rail Op Amp                                    U2       National Semi1  LM2937ET-12        12 V 500 ma LDO Regulator                                    U3       National Semi1  MC33039D           Closed Loop Motor Control IC                                    U5       Motorola1  CTX20-3P           20 uH              L1       CoilTronics/GFS1  MAX761CSA MAX761ESA                 Step-Up DC/DC Conv U6       Maxim1  293D686X96RD2T        93F2704  68 uF 6.3 V Solid Tantalum Capacitor                                    C6       Sprague1  293D685X9035D2T        89F2727  6.8 uF 35 V Solid Tantalum Capacitor                                    C2       Sprague2  293D336X9016D2T        93F2693  33 uF Solid Tantalum Capacitor 25 V (16                                    C14, C16 Sprague1  MC33035DW          Brushless Motor Control IC                                    U7       Motorola1  LM4040E1M3-2.5-ND  2.5 V reference    U9       National Semi1  NDM30001  LR2512R100F        3-Phase MOSFET Bridge                                    U8       National Semi1  CRCW 1206 622 J        96F7809  0.1 ohm 1 W Sense resistor                                    R13      IRC1  RT1                6.2 K Film Resistor, 1/8 W, 5%                                    R4       Dale3  CRCW 1206 102 J    1 K Film Resistor, 1/8 W, 5%                                    R26, R33, R40                                             Dale   RT13  CRCW 1206 681 J    680 ohm Film Resistor, 1/8 W, 5%                                    R28, R35, R42                                             Dale   RTI1  CRCW 0603 122 J    1.2 k ohm Film resistor, 1/16 W, 5%                                    R2       Dale   RT12  P2.4KGCT-ND        2.4 k ohm Film resistor, 1/16 W, 5%                                    R20, R21 Panasonic11 CRCW 0603 103 J    10 k ohm Film resistor, 1/16 W, 5%                                    R18-19, R22-R24,                                             Dale   RT1                                   R29-R31, R36-R38                                             Dale1  P10.0kHCT-ND       10 k ohm Film resistor, 1/16 W, 1%                                    R15      Panasonic1  P7.5kGCT-ND        7.5 k ohm Film resistor, 1/16 W, 5%                                    R9       Dale3  P51kGCT-ND         51 K ohm Film resistor, 1/16 W, 5%                                    R25, R32, R39                                             Dale1  P75kHCT-ND         75 K ohm Film resistor, 1/16 W, 1%                                    R16      Dale1  P150kGCT-ND        150 k ohm Film resistor, 1/16 W, 5%                                    R14      Dale1  P200kHCT-ND        200 K ohm Film resistor, 1/16 W, 1%                                    R8       Dale1  BZX84C27LT1        BZX84C27DICT-                 27 V zener SMT     VR1      Motrla/Diodes Inc        ND3  BZX84C4V7LT1        BZX84C4VDICT-                 4.7 V zener SMT    VR2-VR4  Motrla/Diodes Inc        ND3  BZX84C12LT1        BZX84C12DICT-                 12 V zener SMT     VR5-VR7  Motrla/Diodes Inc        ND   NO STUFF                              R3, R5, R7, U10,                                    U11   NO STUFF                              U12, TP1-TP10,                                    RT21  AN-1302G           Gray NEMA-4-Enclosure       Bud1  JG02               PWB, Hummer 1               United Circuits1  JBXER2G12FCSD        EGG.2B.312.CLM                 Panel mount receptacle connector-crimp                                    J2 external                                             JBX/Lemo1  S102-A053-13714.7-S                 4-pin Plug connector w/male pins                                    J1 external                                             W. W. Fischer4  TBD                #6 screw                    TBD4  RN-6-375A          1/4&#34; 0.D. nylon spacer 3/8&#34;; #6 screw                                             SPC Tech1  3203               Cable, 26 awg, 4-conductor, shielded,                                             Alpha1  GCA.2S.255.LT      Lug, Solder for 2S or 2B Lemo                                             Lemo1  TBD                Tie wrap1  SJ3551             Fastener, Dual Lock, black, self adhesive                                             3M1  TBD                Clamping Grommet-black      Heyco1  640442-2           2-pin 26 awg receptacle IDC connector                                             Amp1  640441-8           8-pin 24 awg receptacle IDC connector                                             Amp__________________________________________________________________________ 
    
     The embodiment of FIGS. 3a-3d and the parts list of Table 1 are merely examples; a person of ordinary skill in the art will recognize that modifications and substitutions can be made. 
     In operation, the NPN darlington transistor Q1 of filter 12 transmits the entire adapter input voltage (as V bridge) to the P channel MOSFETS in the three-phase motor controller 20a (of FIG. 3c) and output drive stage 22 when the adapter input signal voltage is twelve volts or below but reduces the gate-to-source voltage (V gs ) to a resistor ratio (e.g., R26/R28) when the adapter input exceeds twelve volts DC, due to operation of a voltage sensing circuit including zener diodes (e.g., VR5) in motor controller 20. The P channel FETs are internally connected to pins 2,1 and 24 of controller chip 20a (i.e., U7). Using one section of circuit 20 as an example, when Vbridge is above a selected threshold level (e.g., twelve volts) zener diode VR5 is conductive, transistor Q3 is switched off and FET Q4 is off, so Vbridge is reduced across the series combination of R26 and R28 connected to pin 2 of controller chip 20a. However, when Vbridge is below twelve volts, zener diode VR5 is non-conductive, transistor Q3 is switched on, FET Q4 is on and effectively short circuits R28 so Vbridge is reduced across only R26 connected in series to pin 2 of controller chip 20a. The operation of controller 20 thus allows optimum efficiency when operating with low input voltages but limits V gs  (e.g. at pins 2,1, and 24 of chip 20a) to under 20 volts for the range of input voltages up to 30 volts, thereby protecting the P channel MOSFETs in the output stage of controller 20. Such protection is required since the maximum rating of MOSFET V gs  is typically twenty volts or less. 
     Adapter 8 accepts bipolar drive signals over the J1 inputs MTR+ and MTR- and reverses the brushless DC motor direction in response to a change of input voltage polarity from the two-wire medical console controller circuit input at J1. The adapter circuit 8 eliminates the need for a negative supply voltage by creating a positive bias in the control loop such that the control signal is nominally 2.5V above ground (i.e., the level of the RTN output of filter 12). Positive bias or offset is provided by the reference voltage circuit 16b in summer circuit 16c (as shown in FIG. 3b) and bipolar drive signal generation without a negative voltage supply. Op-Amp 16a in speed control circuit 16 has a non-inverting input connected via half bridge 16d as illustrated in FIG. 1 and FIGS. 3a and 3b (by traversing connection A), thereby forming a speed or velocity control loop for motor controller adapter 8. 
     Turning now to FIGS. 4a and 4b, there is illustrated a surgical instrument handpiece 70 having an interior cavity 71 within which brushless motor 72 is removably disposed. Brushless motor 72 drives a surgical implement (e.g., a burr or blade for use in ENT surgery or the like) detachably attached at the handpiece distal end 75. As illustrated in FIG. 4b, handpiece 70 includes, at its proximal end 73 a handpiece connector 74 removably attached to a distal cable connector 78 affixed to a flexible cable 76 for receiving a handpiece brushless motor driving signal as an input from the adapter 8. Opposite distal cable connector 78 and affixed to cable 76 is proximal cable connector plug 80 removably connected to electrical connector J2external of adapter 8. Mating connectors (80 and J2external) include cable connector plug 80 with twelve conductive elongate pins slidably, rectilinearly received within the conductive pin receiving sockets J2-1 through J2-12. The conductive pins of plug 80 are slidably received (with a friction conductive fit) in the pin receiving sockets 120 of output connector J2 external, thereby providing a sterile and fluid-tight seal to the electrical connection made thereby. 
     The adapter 8 of the present invention permits use of a handpiece (e.g., 70) having a brushless D.C. motor driving a surgical implement with a medical console 9 of the type designed for connection to brushes in a commutated D.C. motor and, thus, provides new uses for existing consoles. Accordingly, a method according to the present invention includes the steps of coupling adapter 8 to medical console 9 of the type having a two-wire controller for connection to brushes in a commutated D.C. motor, connecting an output of the adapter to a brushless D.C. motor in a handpiece for driving a surgical implement and controlling operation of the surgical handpiece via the medical console. Optionally, an operator may adjust the &#34;full speed gain&#34; voltage through adjustable resistor RT1 and &#34;start speed offset&#34; voltage through adjustable resistor RT2, to calibrate the operating speed of the instrument motor for use with a given medical console. 
     Having described preferred embodiments of a new and improved adapter and circuit, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teaching set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention as defined by the appended claims.