Abstract:
A six-phase 12 step firing circuit for brushless DC controllers to independently distribute current in six motor stator windings of a six-phase brushless DC motor, the firing circuit receives hall sensor rotor position signals in conjunction with a drive start signal and pulse width modulation commands driving a six-phase power bridge assembly fired at 30 degree intervals to produce a sequence for rotation of the motor.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Provisional Patent Application No. 61/210,445 which was filed on Mar. 19, 2009 by the present inventor. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to brushless motor controls, more specifically a firing circuit method for distributing current independently to the six stator windings of a brushless DC motor. 
         [0004]    2. Description of the Related Art 
         [0005]    Brushless DC systems today are more efficient, better speed/torque characteristics, higher response and speed ranges, plus they operate more quietly compared to conventional DC systems and AC inverters. In three-phase brushless DC systems of today two windings are excited at a time to create a rotating electrical field. 
         [0006]    Comparing six-phase brushless DC controllers to three-phase brushless DC controllers, in a six-phase design the motor is wired in a split 2 wye or split 2 delta for six independently wired stator windings which four windings are excited at a time to create a rotating electrical field. The currents in each winding are half of the prior art plus distributes the motor torque more evenly for a smoother operation. Attributes of this present art are smaller line and motor wires, smaller start-up and stall currents, less demand on the power grid, better speed/torque characteristics, better response, improve positioning, quieter operation, reduced torque ripple, and higher system reliability. This present distribution of motor current will deliver a more even ratio of torque to the motor helping in applications where weight and space are critical factors. 
         [0007]    U.S. Pat. No. 4,758,768 discloses a 12 step commutation device for an electric motor. The device is designed to reduce torque ripple and increase motor efficiency in a three phase brushless DC motor by adding 6 additional commutation steps occurring between each of the original 6 steps using additional hall-effect sensors. The prior art uses a three-phase brushless DC motor and a three-phase power bridge. 
         [0008]    U.S. Pat. No. 6,956,341 discloses two inverters (INV 1 , INV 2 ) supply phase currents to three-phase coils (Y 1 , Y 2 ). This system is used to reduce the number of phase currents to be measured as a result of an observer for phase current estimation. This prior art does not mention a six-phase firing circuit for brushless DC controls. 
         [0009]    Both of these prior arts does not disclose reduction of motor current by 50%, a six-phase firing circuit receiving hall sensor feedback signals for positioning control or connected to a 6-phase power bridge assembly comprising of a six-phase brushless DC motor firing at 30 electrical degrees for a 360 degree electrical cycle. 
       BRIEF SUMMARY OF INVENTION 
       [0010]    It is the object of the present invention to independently distribute current in the six windings of a six-phase brushless DC motor every 30 electrical degrees, and thereby reducing the motor current in half of the prior art. This will help in large horse power systems, low voltage applications and battery source applications by the reduction of motor currents for the same given horse power. To achieve this object, one embodiment of the present invention is a six-phase power bridge assembly comprising of twelve power switching devices connected to a six-phase brushless DC motor. 
         [0011]    A second embodiment of the present invention is coupled to the hall sensor inputs from the motor to provide rotor position signals to a analog switch to sequence six-phase power bridge assembly switching devices Q 1 -Q 2 -Q 3 -Q 4 -Q 5 -Q 6 . 
         [0012]    A third embodiment of the present invention provides a comparator circuit coupled to the hall effect sensors inputs to reset the decade counter and provide input frequency to a phase lock loop. The decade counter and the phase lock loop will provide a clock signal to a flip-flop to deliver the rotor position signals for a second analog switch to sequence six-phase power bridge assembly switching devices Q 7 -Q 8 -Q 9 -Q 10 -Q 11 -Q 12 . 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a schematic diagram of a six-phase power bridge assembly. The diagram comprises of the + and − DC buss bars with twelve power switching devices wired to the six-phase brushless DC motor windings connected in a split two wye. 
           [0014]      FIG. 2  is a schematic diagram of a six-phase 12 step firing circuit. It comprises of an analog switch and or gates to sequence six-phase power bridge assembly switching devices Q 1 -Q 2 -Q 3 -Q 4 -Q 5 -Q 6 . A comparator, decade counter, phase lock loop, flip-flop, analog switch and or gates to sequence six-phase power bridge assembly switching devices Q 7 -Q 8 -Q 9 -Q 10 -Q 11 -Q 12 . 
           [0015]      FIG. 3  is a timing graph showing the majors waveforms for a 360 electrical degree cycle. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0016]    Refer to  FIG. 1 ,  FIG. 2 ,  FIG. 3  and TABLE 1 for the full explanation of the Detailed Description. TABLE 1 is located below. 
         [0017]    The signal input X of IC 5  and IC 6  is a +15 volt drive start signal for activation of top six-phase power bridge switching devices Q 1 -Q 2 -Q 3 -Q 7 -Q 8 -Q 9 . 
         [0018]    The signal input Y of IC 5  and IC 6  are interfaced to the pulse width modulation signal for activation of bottom six-phase power bridge switching devices Q 4 -Q 5 -Q 6 -Q 10 -Q 11 -Q 12 . 
         [0019]    The sequencing inputs of analog switches IC 5  and IC 6  are weighted with A=1, B=2, and C=4 to produce motor rotation. The hall sensor voltage is supplied from resistor network R 5  and interfaced to analog switch IC 5  to sequence six-phase power bridge switches Q 1 -Q 2 -Q 3 -Q 4 -Q 5 -Q 6  for steps  1 ,  3 ,  5 ,  7 ,  9 , and  11 . These steps will transition at degrees 0-60-120-180-240-300. 
         [0020]    The exclusive nor gate IC 1  will trigger on hall sensor transitions. The hall sensors provide a rotor position signal transition every 60 electrical degrees at degrees 0-60-120-180-240-300 that will reset the decade counter IC 2  plus provide a frequency input to the phase lock loop IC 3 . 
         [0021]    The phase lock loop IC 3  will clock the decade counter IC 2  six times before the decade counter Q 5  provides a signal to the phase detector of IC 3 . The output of the phase detector is a voltage that represents the error between the rotor position signal and the phase of the divided down by 6 voltage-control oscillator signal. This error signal is filtered with R 2 , R 3  and C 2  then used to control the frequency of the voltage-controlled oscillator forcing it to track the rotor position signals. The center frequency range of the voltage-controlled oscillator is set by C 3 , the maximum frequency is set by R 4 . Q 3  output of the decade counter IC 2  will clock the flip-flop IC 4  and the rotor position signals will transfer from the flip-flop IC 4  to the analog switch IC 6  to sequence six-phase power bridge switching devices Q 7 -Q 8 -Q 9 -Q 10 -Q 11 -Q 12  for steps  2 ,  4 ,  6 ,  8 ,  10 , and  12 . These steps will transition at degrees 30-90-150-210-270-330. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Power Bridge Sequencing Steps for Motor Rotation 
               
             
          
           
               
                 Step 
                 Electrical Degrees 
                 Power Bridge Switches 
               
               
                   
               
             
          
           
               
                 1 
                 0 
                 1-6 
               
               
                 2 
                 30 
                  7-12 
               
               
                 3 
                 60 
                 2-6 
               
               
                 4 
                 90 
                  8-12 
               
               
                 5 
                 120 
                 2-4 
               
               
                 6 
                 150 
                  8-10 
               
               
                 7 
                 180 
                 3-4 
               
               
                 8 
                 210 
                  9-10 
               
               
                 9 
                 240 
                 3-5 
               
               
                 10 
                 270 
                  9-11 
               
               
                 11 
                 300 
                 1-5 
               
               
                 12 
                 330 
                  7-11 
               
               
                   
               
             
          
         
       
     
         [0022]    Using  FIG. 3 , HS 1 , HS 2  and HS 3  are hall sensor signals from the motor. Each step preformed below, can also be verified using  FIG. 2  and  FIG. 3 . 
         [0023]    With the rotor at 0 electrical degrees, HS 1  is high, HS 2  is low and HS 3  has transitioned from high to low. This halitensor value of one applied to the sequence inputs of analog switch IC 5  will select channel X 1  to drive or gate IC 7  output for operation of six-phase power bridge switching device Q 1  and select channel Y 1  to drive or gate IC 8  output for operation of six-phase power bridge switching device Q 6  (step 1 ). 
         [0024]    With the rotor at 30 electrical degrees, Q 3  of the decade counter IC 2  will clock flip-flop IC 4  and transfer a hall sensor value of one to the sequence inputs of analog switch IC 6 . This will select channel X 1  to drive or gate IC 8  output for operation of six-phase power bridge switching device Q 7  and select channel rt to drive or gate IC 9  output for operation of six-phase power bridge switching device Q 12  (step  2 ). 
         [0025]    With the rotor at 60 electrical degrees, HS 1  is high, HS 2  will transition from low to high applying a hall sensor value of three to the sequence inputs of analog switch IC 5 . This will select channel X 3  to drive or gate  107  output for operation of six-phase power bridge switching device Q 2  and select channel Y 3  to drive or gate IC 8  output for operation of six-phase power bridge switching device Q 6  (step  3 ). 
         [0026]    With the rotor at 90 electrical degrees, Q 3  of the decade counter IC 2  will clock flip-flop IC 4  and transfer hall sensor value of three to the sequence inputs of analog switch IC 6 . This will select channel X 3  to drive or gate IC 8  output for operation of six-phase power bridge switching device Q 8  and select channel Y 3  to drive or gate IC 9  output for operation of six-phase power bridge switching device Q 12  (step  4 ). 
         [0027]    With the rotor at 120 electrical degrees, HS 1  will transition low and HS 2  is high applying a hall sensor value of two to the sequence inputs of analog switch IC 5 . This will select channel X 2  to drive or gate IC 7  output for operation of six-phase power bridge switching device Q 2  and select channel Y 2  to drive or gate IC 7  output for operation of six-phase power bridge switching device Q 4  (step  5 ). 
         [0028]    With the rotor at 150 electrical degrees, Q 3  of the decade counter IC 2  will clock flip-flop IC 44  and transfer hall sensor value of two to the sequence inputs of analog switch IC 6 . This will select channel X 2  to drive or gate IC 8  output for operation of six-phase power bridge switching device Q 8  and select channel Y 2  to drive or gate IC 9  output for operation of six-phase power bridge switching device Q 10  (step  6 ). 
         [0029]    With the rotor at 180 electrical degrees, HS 2  is high and HS 3  will transition high applying a hall sensor value of six to the sequence inputs of analog switch IC 5 . This will select channel X 6  to drive or gate IC 7  output for operation of six-phase power bridge switching device Q 3  and select channel Y 6  to drive or gate IC 7  output for operation of six-phase power bridge switching device Q 4  (step  7 ). 
         [0030]    With the rotor at 210 electrical degrees, Q 3  of the decade counter IC 2  will clock flip-flop IC 4  and transfer hall sensor value of six to the sequence inputs of analog switch IC 6 . This will select channel X 6  to drive or gate IC 9  output for operation of six-phase power bridge switching device Q 9  and select channel Y 6  to drive or gate IC 9  output for operation of six-phase power bridge switching device Q 10  (step  8 ). 
         [0031]    With the rotor at 240 electrical degrees, HS 2  will transition low and HS 3  is high applying a hall sensor value of four to the sequence inputs of analog switch IC 5 . This will select channel X 4  to drive or gate IC 7  output for operation of six-phase power bridge switching device Q 3  and select channel Y 4  to drive or gate to IC 8  output for operation of six-phase power bridge switching device Q 5  (step  9 ). 
         [0032]    With the rotor at 270 electrical degrees, Q 3  of the decade counter IC 2  will clock flip-flop IC 4  and transfer hall sensor value of four to the sequence inputs of analog switch IC 6 . This will select channel X 4  to drive or gate IC 9  output for operation of six-phase power bridge switching device Q 9  and select channel Y 4  to drive or gate IC 9  output for operation of six-phase power bridge switching device Q 11  (step  10 ). 
         [0033]    With the rotor at 300 electrical degrees, HS 1  will transition high and HS 3  is high applying a hall sensor value of five to the sequence inputs of analog switch  105 . This will select channel X 5  to drive or gate  107  output for operation of six-phase power bridge switching device Q 1  and select channel Y 5  to drive or gate IC 8  output for operation of six-phase power bridge switching device Q 5  (step  11 ). 
         [0034]    With the rotor at 330 electrical degrees, Q 3  of the decade counter IC 2  will clock flip-flop IC 4  and transfer hall sensor value of five to the sequence inputs of analog switch IC 6 . This will select channel X 5  to drive or gate  108  output for operation of six-phase power bridge switching device Q 7  and select channel Y 5  to drive or gate IC 9  output for operation of six-phase power bridge switching device Q 11  (step  12 ). 
         [0035]    This present art is designed for pulse width modulation input to the firing circuit. Simply modifications can be made to the firing circuit to accept sinusoidal wave forms for motor rotation. 
         [0036]    This present art can be easily modified for 12-phase  24  step operations and 24-phase  48  step operations. 
         [0037]    It will be appreciated and apparent by those skilled in the art that changes, modifications, variations and substitutions of the invention may be made without departing from the inventive concepts and principles in performing the same functions in the aforementioned descriptions and drawings. It is not intended that the invention is limited in nature to the illustrative embodiment described herein. It is intended that all such changes, modifications, variations and substitutions be included within the scope of the invention defined by the appended claims and their equivalents. Special needs are intended to accommodate all horsepower ranges, motor positioning feedback systems and power bridge assembly devices.