Abstract:
An electronically commutated DC motor comprises a stator comprising at least one stator winding ( 22, 24, 26 ), a rotor ( 28 ) electromagnetically interacting with the stator, a positive and a negative DC voltage line ( 76, 78 ) for supplying power to the motor ( 20 ), in particular from a battery ( 77 ), a full bridge circuit ( 74 ) for controlling the current in the at least one stator winding ( 22, 24, 26 ), which full bridge circuit ( 74 ) comprises a plurality of bridge arms that each comprise an upper bridge transistor ( 66, 80, 86 ) for controlling the current from the positive DC voltage line ( 76 ) to an associated terminal ( 68; 82; 88 ) of that stator winding ( 22, 24, 26 ) as well as a lower bridge transistor ( 70, 84, 90 ) for controlling the current from the relevant terminal of the stator winding to the negative DC voltage line ( 78 ). The motor further comprises an arrangement for generating a plurality of rotor position signals, and an arrangement for controlling a predetermined bridge transistor by logical combination of rotor position signals associated therewith, there being provided, for logical combination of those rotor position signals, a control transistor ( 60 ) to whose base a first rotor position signal (H 1 ) is conveyable and to whose emitter a second rotor position signal (H 2 ) is conveyable, and whose collector signal serves to control the predetermined bridge transistor ( 66 ). A circuit comprising a half bridge is also described.

Description:
CROSS REFERENCE 
   This application is a section 371 of PCT/EPO3/03067, filed 25 Mar. 2003 and published 16 Oct. 2003 in the German language as WO 03-085808-A1. The international application claims priority from German application DE 102 15 895.9, filed 11 Apr. 2002, which is incorporated by reference. 

   FIELD OF THE INVENTION 
   The invention concerns an electronically commutated DC motor comprising a full bridge circuit. 
   BACKGROUND 
   In such a motor, a plurality of rotor position signals are generated, and the individual semiconductor switches of the full bridge circuit are controlled by combinations of those rotor position signals. If a first rotor position signal is designated H 1  and a second signal H 2 , then (as an example) one semiconductor switch of the full bridge must be switched on when the one signal H 1  has the value 1 and the other signal H 2  has the value 0. On the other hand, a different semiconductor switch of the full bridge must be switched on, for example, when H 2  has the value 1 and H 1  the value 0. 
   For known motors of this kind, signals H 1  and H 2  are required in non-inverted form, i.e. as H 1  and H 2 , and they are required in inverted form, i.e. as /H 1  and /H 2 . Conjunctive logical combination elements are furthermore needed in order to combine these signals, and a PWM signal often must additionally be taken into account. AND elements are usually used for this purpose. 
   This results in complex circuits having many components, making it difficult, in the context of small motors, to accommodate the circuit board in the motor housing, and raising the cost of manufacturing the circuit boards (and therefore the motors), since multi-layer circuit boards are required. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to make available a new electronically commutated motor having a full bridge circuit. 
   According to the invention, this object is achieved by providing a control transistor serving to logically combine the rotor position signals, a first rotor position signal being applied to the base of the control transistor, a second rotor position signal being applied to the emitter, and the collector signal serving to control the current in an associated stator winding. The control transistor effects a logical combination of two rotor position signals in simple fashion and without separate signal inversion, can additionally serve as a level converter as necessary, and allows reciprocal locking of the upper and lower bridge transistors of a bridge arm. The circuit is simplified by way of the invention in such a way that the requisite circuit board can be manufactured easily and inexpensively even for small motors; and installation space is obtained, as applicable, for additional motor functions. 
   A particularly simple way of achieving the stated object is to use a bridge circuit to control the current in the stator winding phases, at least one transistor in a bridge arm controlling the current from DC voltage supply lines to the respective associated stator winding phase, with the bridge circuit transistors being driven by logically combining rotor position signals. This is a very simple commutation circuit for a low-output three-phase motor, with which the motor can be operated in one predetermined rotation direction. 
   Further details and advantageous refinements of the invention may be inferred from the exemplary embodiments, in no way to be understood as a limitation of the invention that are described below and depicted in the drawings. 

   
     BRIEF FIGURE DESCRIPTION 
       FIG. 1  shows a first embodiment of an electronically commutated DC motor according to the invention, two variants of the invention being depicted in  FIG. 1 ; 
       FIG. 2  shows a second embodiment of a motor according to the present invention; 
       FIG. 3  contains diagrams to explain the invention; 
       FIG. 4  shows a modification of  FIGS. 1 and 2  that allows low-loss operation particularly in instances where the operating voltage U B  of the motor fluctuates within relatively wide limits; 
       FIG. 5  shows a third embodiment of a motor according to the present invention; 
       FIG. 6  shows a circuit according to the present invention having a three-phase half bridge; and 
       FIG. 7  shows a circuit having a three-phase full bridge in which the logic transistors are simultaneously used as output stage transistors. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows, at the right, an electronically commutated motor  20  having three stator winding phases  22 ,  24 ,  26  and a symbolically indicated permanent-magnet rotor  28 , depicted with two poles, around which three rotor position sensors  30 ,  32 ,  34  are arranged at intervals of 120° el. and furnish signals H 1 , H 2 , H 3 . These three sensors are also depicted at the far left in FIG.  1 . They are connected in series. Lower sensor  34  is connected via a resistor  36  to ground  38 , while upper sensor  30  is connected via a resistor  40  to a positive potential, e.g. to a regulated auxiliary voltage of +5 V. Resistors  36  and  40  are usually identical in size. Sensors  30 ,  32 ,  34  are normally Hall sensors, but any other sensors would also be possible, e.g. optical sensors. 
   The two output signals of Hall sensor  30  are conveyed to the inputs of a comparator  42  whose output  44  (with open collector) is connected via a pull-up resistor  46  to an auxiliary voltage of e.g. +12 V, thus providing at output  44  a signal H 1  that has, depending on the position of rotor  28 , either the potential of ground  38  or a potential of approx. +12 V. It is very advantageous that this potential can be selected based on the requirements of motor  20 . Output  44  is connected via a high-resistance positive feedback resistor  45  to the positive input of comparator  42 . 
   In the same fashion, the two outputs of Hall sensor  32  are connected to the two inputs of a comparator  50  whose output  52  (with open collector) is connected via a pull-up resistor  54  to a defined positive potential, e.g. +12 V, thus providing at output  52  a signal H 2  that has, depending on the position of rotor  28 , either the potential of ground  38  or a positive potential. Output  52  is connected via a high-resistance positive feedback resistor  53  to the positive input of comparator  50 . 
   The two output signals of Hall sensor  34  are conveyed to the inputs of a comparator  55  whose output  57  (with open collector) is connected via a high-resistance positive feedback resistor  59  to the positive input. Signal H 3  is obtained at output  57 . 
   Output  44  is connected via a resistor  56  to the base of an npn control transistor  60  whose emitter is connected to output  52  and whose collector is connected via a resistor  62  and a node  63  to the base of an upper bridge transistor  66 , which is depicted as a pnp transistor but alternatively, as indicated, can also be a p-channel MOSFET  66 ′. Node  63  is connected via a resistor  64  to operating voltage U B . The emitter of transistor  66  is likewise connected to operating voltage U B ; its collector is connected via a node  68  to the collector of an npn transistor  70  serving as a lower bridge transistor, whose emitter is connected via a small resistor  72  (for current measurement) to ground  38 . 
   Bridge transistors  66  and  70  constitute one arm of a full bridge circuit  74  whose positive DC voltage line is labeled  76  and whose negative DC voltage line is labeled  78 , and which can be connected, for example, to a battery  77  in the manner depicted or to a DC link circuit. Full bridge circuit  74  also contains a pnp transistor  80  that is connected via a node  82  to an npn transistor  84 , and contains a pnp transistor  86  that is connected via a node  88  to an npn transistor  90 .  FIG. 1  explicitly shows only the manner in which transistors  66  and  70  are driven. Transistors  80  and  84 , and  86  and  90 , are driven in entirely similar fashion but with different corresponding combinations of the output signals of sensors  30 ,  32 , and  34 , as explained explicitly in FIG.  3 . 
   According to  FIG. 1 , winding phase  22  is connected between nodes  68  and  82 , winding phase  24  between nodes  82  and  88 , and winding phase  26  between nodes  68  and  88 . This corresponds to a delta winding configuration. A Y-configured circuit would likewise be possible. 
   The positive DC voltage line  76  (+U B ) is connected via a resistor  64  to the base of transistor  66 . 
   Output  52  of comparator  50  is connected to the emitter of a pnp control transistor  94  whose base is connected via a resistor  96  to output  44 , and whose collector is connected (in  FIG. 1 ) to the base of bridge transistor  70  and, via a resistor  98 , to ground  38 . This collector is also connected to the anode of a diode  100  whose cathode is connected to a PWM generator  102 . The latter is also connected via a diode  104  to the base of lower bridge transistor  84 , and via a diode  106  to the base of lower bridge transistor  90 . 
   As indicated schematically in  FIG. 1 , upper bridge transistors  66 ,  80 ,  86  can be replaced by p-channel MOSFETs  60 ′,  80 ′,  86 ′; and lower bridge transistors  70 ,  84 ,  90  can similarly be replaced by n-channel MOSFETs  70 ′,  84 ′,  90 ′. 
   This is depicted in  FIG. 1  for MOSFETs  66 ′ and  70 ′. For MOSFET  66 ′, source S is connected to line  76 , drain D to node  68 , and gate G to connecting point  63 . For MOSFET  70 ′, drain D is connected to node  68 , source S to line  78 , and gate G to the collector of control transistor  94 . 
   Preferred Values For Components in  FIG. 1   
   k=kilohm, M=megohm. The component values refer to bipolar bridge transistors  66 ,  70 ,  80 ,  84 ,  86 ,  90  depicted in  FIG. 1 , at a U B  of 18 to 33 V. 
                                               Hall sensors 30, 32, 34   HW101A           R 36, 40   200 ohms           Comparators 42, 50, 55   LM2901           R 45, 53, 59     1 M           R 46, 54   2.2 k           R 56, 96    47 k           Transistor 94   BC847BPN           Transistor 60   BC847B           R 62, 64, 98   4.7 k           Diodes 100, 102, 104   RB731U           Bridge transistors 66, 80, 86   BD680           Bridge transistors 70, 84, 90   BD679           Resistor 72    56 mOhm           Alternatively:           MOSFETs 66′, 70′, 80′, 84′, 86′, 90′   IRF7343                        
Mode of Operation of  FIG. 1   
     FIG. 3  shows at a), b), and c), for explanatory purposes, the three Hall signals H 1 , H 2 , H 3  during one revolution of rotor  28  through 360° el. 
     FIG. 3   g ) shows examples of the logical values of the Hall signals for rotor positions  1  (30° el.) and  2  (90° el.) through  6  (330° el.). 
     FIG. 3   h ) shows that in the rotational position range between 0° and 120° el., transistor  66  is switched on because H 1 =1 and H 2 =0, i.e. /H 2 =1. Similarly, in the rotational position range between 0 and 60° el., lower transistor  84  is switched on because /H 2 =1 and H 3 =1. In the rotation angle range from 0° el. to 60° el., current therefore flows from positive DC voltage line  76  through bridge transistor  66 , winding phase  22 , bridge transistor  84 , and resistor  72  to ground  38 . Correct commutation is performed for each rotational position range in accordance with the table in  FIG. 3   h ), as is known to one skilled in the art. 
   In the rotational position range between 0 and 120° el., output  44  of comparator  42  is high-resistance, so that this output, and with it the base of transistor  60 , receives a positive potential Hi through resistor  46 . 
   In this rotational position range, output  52  of comparator  50  is connected via comparator  50  internally to ground  38 , so that the emitter of transistor  60  is grounded. 
   Transistor  60  is thus conductive, and a current is obtained through resistors  64  and  62 . The voltage drop at resistor  64  is sufficiently large that upper bridge transistor  66  is reliably switched on. 
   In the angle range between 180° el. and 300° el., /H 1 =1 and also H 2 =1, so that lower bridge transistor  70  is switched on. 
   In this case comparator  50  is high-resistance, so that the emitter of transistor  94  is connected via pull-up resistor  54  to a suitable positive voltage, for example +12V, i.e. H 2 =1. 
   In the angle range 180 through 300° el., output  44  of comparator  42  is connected internally to ground  38  so that H 1 =0 (therefore /H 1 =1); through resistor  96 , the base of transistor  94  acquires approximately the potential of ground  38 , so that this transistor  94  conducts and a corresponding voltage drop occurs at resistor  98 , switching on lower bridge transistor  70  completely, i.e. with a low internal resistance. 
   When the output of PWM generator  102  is positive, diodes  100 ,  104 ,  106  are blocked, and the gate potentials of lower bridge transistors  70 ,  84 ,  90  are not influenced. If that output is at ground potential, however, diodes  100 ,  104 ,  106  become conductive and pull the potentials at the bases of lower bridge transistors  70 ,  84 ,  90  to a low value, so that the these bridge transistors are blocked. 
   Particular advantages include: 
   It is no longer necessary to generate inverted control signals (/H 1 , /H 2 ). 
   The circuit can be implemented more easily and more inexpensively on small circuit boards. 
   Space is obtained on the circuit board for additional motor functions. 
   Less-expensive components can be used; for example, a two-layer circuit board often is sufficient. 
   Generation of the control signals for the upper bridge transistor no longer requires an additional transistor (“level converter” transistor). 
   The lower bridge transistors can be optimally driven. With a MOSFET, the optimum voltage U GS  for switching on can be, for example, 15 to 20 V, and corresponding control currents are required. If these values are optimized, as is possible with the invention, the switching-on resistance of lower MOSFET&#39;s  70 ′,  84 ′,  90 ′ can then be reduced by 10 to 12%, thus decreasing losses and increasing the motor&#39;s efficiency. 
   A full bridge circuit automatically results in reciprocal locking of the upper and lower bridge transistors, e.g. transistors  66  and  70  or  66 ′ and  70 ′. 
   The use of bipolar transistors  66 ,  70  results in an extremely simple output stage configuration. 
   If the combination of Hall sensor  30  and comparator  42  is used, a very inexpensive electronic system is obtained and it is often possible to work without a multi-layer circuit board, i.e. with only two layers. If Hall ICs plus multiple layers are used, circuit boards for even smaller motors can then be implemented. 
     FIG. 2  shows a variant depicting substantially only the parts that differ from FIG.  1 . Parts identical, or functioning identically, to ones in  FIG. 1  are therefore not described again. 
   The potential at the collector of transistor  94  is here conveyed to the bases of an npn transistor  110  and a pnp transistor  112 , the emitters of which are connected to one another and, via a resistor  114 , to gate G of lower transistor  70 ′. 
   The collector of transistor  110  is connected, for example, to +12 V, and the collector of transistor  112  is connected to ground  38 . 
   When transistor  94  conducts, transistor  110  acquires a positive potential at its base and switches on, while transistor  112  is blocked. As a result, transistor  70  is quickly switched on. 
   When transistor  94  is blocked, transistor  110  is also blocked, and transistor  112  acquires a potential of 0 V at its base so that it switches on, thereby pulling gate G of transistor  70  to ground  38  and quickly switching off transistor  70 ′. 
   The circuit according to  FIG. 2  is especially suitable when the PWM generator is operating at a high frequency, since at 25 kHz the gate capacitance of transistor  70 ′ must be charged and discharged 25,000 times per second; the requisite rapid charge reversal with high currents can be achieved without difficulty by way of the two transistors  110 ,  112 , resulting in a fast switchover and low power loss in lower transistor  70 ′. 
   If a bipolar transistor is used for bridge transistor  70 ′, its base can be driven at low resistance, so that the charge carriers are rapidly conveyed to and from the base. The result is a fast switchover with low losses, i.e. good motor efficiency. 
   Preferred Values for Components in  FIG. 2   
   Values conforming to those in  FIG. 1  are not listed. 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               Transistors 60, 94, 110, 112 
               BC847BPN 
             
             
                 
               R 98 
               100 k 
             
             
                 
               R 114 
               100 ohms 
             
             
                 
               R 54, 64 
                10 k 
             
             
                 
                 
             
           
        
       
     
   
     FIG. 4  shows a variant for upper control transistor  60 . This variant can be used in  FIGS. 1 and 2 . Identical or identically functioning parts are labeled with the same reference characters as therein, and usually are not described again. 
   Here the collector of upper npn control transistor  60  is connected directly to gate G of upper p-channel MOSFET  66 ′, and via a resistor  64 ′ to positive DC voltage line  76 . 
   The emitter of control transistor  60  is moreover connected via an emitter resistor  120  to output  52  of comparator  50 , i.e. to signal H 2 , so that transistor  60  acts as a constant-current source when H 2 =0 and H 1 =1. 
   When operating voltage U B  fluctuates, as is normally the case in the context of a vehicle battery  77 , the collector current of control transistor  60  remains largely constant because of resistor  120 , so that the voltage drop U SG  at resistor  64 ′ is also largely constant. That voltage drop can therefore be set, by selecting resistor  64 ′, to a value only slightly lower than the maximum permissible voltage U SG  (e.g. 20 V) for switching on p-channel MOSFET  66 ′. With bipolar bridge transistors, the emitter-base voltage can be set to a value sufficiently high for reliable switching operation. Transistor  60  operates here in the analog range and is therefore faster than if it were operated in saturated mode, thus reducing losses in motor  20 . 
   Preferred Values for Components in  FIG. 4   
   U B =18 to 33 V 
   Signals H 1 , H 2 =+5 V amplitude 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               R 64′ 
                 2 k 
             
             
                 
               Current I 
               4.2 mA 
             
             
                 
               R 56 
                10 k 
             
             
                 
               R 120 
                 1 k 
             
             
                 
               U SG   
               8.4 V 
             
             
                 
                 
             
           
        
       
     
   
     FIG. 5  shows a commutation circuit for a so-called single-phase motor  130  having a permanent-magnet rotor  132  that controls a Hall sensor  134 , which is depicted again at the far left in FIG.  5  and whose output signals are conveyed to two inputs  136 ,  138  of a microcontroller  140 . This circuit is particularly suitable for economical low-output (i.e. low-current) fans. 
   Rotor  132  interacts with a single-phase stator winding  142  that is connected between two connection points  144 ,  146  of an H-bridge  148 . The latter has a positive terminal  150  to which an operating voltage +U B  is conveyed, and a negative DC voltage terminal  152  that is connected to ground  38  via a low-resistance measuring resistor  154 . 
   A p-channel MOSFET  156  is located between positive DC voltage terminal  150  and connection point  144  as an upper bridge transistor; a p-channel MOSFET  158  is likewise present between positive DC voltage terminal  150  and connection point  146 . 
   An n-channel MOSFET  160  is located between connection point  144  and negative DC voltage terminal  152  as a lower bridge transistor, and an n-channel MOSFET  162  is present between connection point  146  and negative DC voltage terminal  152 . Drains D of the two bridge transistors  156  and  160  are connected to one another, likewise drains D of bridge transistors  158  and  162 . 
   A resistor  166  is located between positive DC voltage terminal  150  and gate G of p-channel MOSFET  156 . A resistor  170  is located between gate G of bridge transistor  156  and the collector of an npn control transistor  168 . The emitter of transistor  168  is connected directly to output B of microcontroller  140 , and via a resistor  171  to gate G of bridge transistor  160 . The base of transistor  168  is connected via a resistor  172  to an output A of microcontroller  140 . 
   Gate G of bridge transistor  158  is connected via a resistor  176  to line  150 , and via a resistor  178  to the collector of an npn control transistor  180  whose emitter is connected directly to output A and via a resistor  182  to gate G of bridge transistor  162 . 
   The base of transistor  180  is connected via a resistor  184  to output B of processor  140 . 
   Preferred Values for  FIG. 5   
   (k=kilohm) 
                                               Hall sensor 134   HW101A           R 172    22 k           Control transistors 168, 180   BC847B           R 166, 176   3.3 k           R 170, 178   4.7 k           R 171, 182     1 k           R 154    56 mOhm           MOSFETs 156, 158, 160, 162   IRF7343                        
Mode of Operation of  FIG. 5   
   When microcontroller  140  is operating normally, outputs A and B are alternately high, i.e. when A is high, B is low, and when B is high, A is low. 
   When output A has a high potential, control transistor  180  is blocked, so that upper bridge transistor  158  is blocked and lower bridge transistor  162  conducts. Output B then has approximately the potential of ground  38 , so that control transistor  168  is conductive and a current flows from positive DC voltage terminal  150  through resistors  166 ,  170  and transistor  168  to output B. As a result, upper bridge transistor  156  acquires a high enough voltage between source and gate to switch it on. 
   Since output B is grounded, in this case lower bridge transistor  160  receives a low signal at its gate G and becomes blocked. 
   When output B becomes high and output A low, control transistor  168  is then blocked so that upper bridge transistor  156  is likewise blocked. Lower bridge transistor  160 , on the other hand, now receives a positive signal at its gate G and becomes conductive. Control transistor  180  becomes conductive so that upper bridge transistor  158  becomes conductive, while lower bridge transistor  162  is blocked because of the low potential at A. 
   If a fault in microcontroller  140  or its program causes output B to switch to high while A is still high, lower bridge transistor  160  can then be switched on only during the rising edge of the (incorrect) signal at output B, while upper bridge transistor  156  is still conductive because, directly thereafter, the base and emitter of control transistor  168  acquire the same potential, so that control transistor  168  becomes blocked and upper bridge transistor  156  switches off. The same applies to bridge transistors  158  and  162  on the right side of H-bridge  148 . 
   A current pulse can therefore flow through both bridge transistors  156 ,  160  only very briefly before control transistor  168  switches off upper bridge transistor  156 . This short current pulse does not result in the destruction of bridge transistor  156  and  160 , i.e. in the event of a fault in microcontroller  140  or its program, motor  130  remains at a standstill and is not destroyed, because the left-hand control transistor  168  additionally acts in this case as an interlock between MOSFETs  156  and  160 . The same is true of right-hand control transistor  180 . 
     FIG. 6  shows a circuit for a three-phase half bridge. The three phases  22 ,  24 ,  26  of motor  20  are Y-configured. Star point  198  is connected to +U B . 
   Motor  20  has a permanent-magnet rotor  28 , depicted with two poles, which controls three Hall ICs  30 ,  32 ,  34  that are arranged around rotor  28  at intervals of 120° el. These Hall ICs are depicted again at the left in FIG.  6 . Three identical power Hall ICs are preferably used here; for example, Hall IC  30  contains a Hall sensor  200  whose two output signals H 1  and /H 1  are generated by respective comparators  202  and  204  (with open collector). Power Hall ICs of this kind can deliver at their outputs  206 ,  208  a current of 150 mA when a voltage of +5 V is applied to positive terminal  210 , and 100 mA at +12 V. 
   In  FIG. 6 , as depicted, only outputs  206 ,  212 , and  214  are used. 
   Output  206  is connected via a pull-up resistor  216  to a voltage of, for example, +12 V, and directly to the base of an npn control transistor  218 , so that this base receives signal H 1  from sensor  30 . The emitter of transistor  218  receives signal H 2  from output  212  of sensor  32 , so that, as indicated, the collector of transistor  218  receives the logically combined signal H 1 */H 2  with which phase  22  is controlled directly; in other words, when output  212  has a low potential and output  206  a high potential, transistor  218  becomes conductive and a current flows from +U B  through phase  22 , control transistor  218 , and Hall IC  32  to ground  38 . 
   Output  212  of sensor  32  is connected via a pull-up resistor  220  to +12 V, and output  214  of sensor  34  is likewise connected via a pull-up resistor  222  to +12 V. 
   Phase  24  receives its current through a control transistor  226 , and phase  26  through a control transistor  228 . 
   The base of transistor  226  receives its control signal H 2  from output  212 . Its emitter receives signal H 3  from output  214 , so that the signal combination H 2 */H 3 , in whose presence a current flows through phase  24 , is obtained at the collector of transistor  226 . 
   The base of transistor  228  receives its control signal H 3  from output  214 , and its emitter receives signal H 1  from output  206 , so that the signal combination H 3 */H 1 , in whose presence a current flows through phase  26 , is obtained at the collector of transistor  228 . 
   This is therefore a very simple commutation circuit for a three-phase motor, with which a low-output motor can be operated in one predetermined rotation direction. Control transistors  218 ,  226 ,  228 , which provide logical combination of the signals, are here used simultaneously as output stage transistors that control the currents in the three stator phases  22 ,  24 ,  26 . Hall ICs  30 ,  32 ,  34  are in this case connected in parallel to a common power supply  210 . 
     FIG. 7  shows a similar circuit but for a motor  20 ′ whose three-phase stator winding can here be operated, as depicted, in a delta configuration. A connection of the three phases in a Y configuration is also depicted as a variant. 
   Motor  20 ′, its rotor  28 , its winding phases  22 ,  24 ,  26 , and its three Hall sensors  30 ,  32 ,  34  bear the same designations as in FIG.  6  and are therefore not described again. Sensors  30 ,  32 ,  34  are depicted again on the left in FIG.  7  and conform to  FIG. 6 , i.e. are power Hall ICs, so that the reader is referred to the description there; the same applies to pull-up resistors  216 ,  220 ,  222 . 
   The circuit according to  FIG. 7  is a full bridge circuit for a three-phase motor in which the logical combination transistors not only combine the sensor signals but also directly control the current in motor  20 ′, the motor current flowing as described below through the pull-up resistors and the internal comparators  202  etc. 
   Output  212  of Hall IC  230  is connected to the bases of an npn control transistor  250  and a pnp control transistor  252 , the emitters of which are connected to one another and to output  206 . Their collectors are likewise connected to one another and to a node  254  to which phases  22  and  26  are connected. 
   Output  214  of Hall IC  34  is connected to the base of an npn control transistor  256  and to the base of a pnp control transistor  258 , the emitters of which are connected to one another and to output  212 . Their collectors are likewise connected to one another and to a node  260  to which phases  22  and  24  are connected. 
   Output  206  of Hall IC  30  is connected to the base of an npn control transistor  262  and to the base of a pnp control transistor  264 , the emitters of which are connected to one another and to output  214 . Their collectors are connected to a node  266  to which phases  24  and  26  are connected. 
   If motor  20 ′ is to be operated in a Y configuration, the windings are connected in accordance with the variant shown at the right in  FIG. 7 , and node  254  becomes node  254 ′, node  256  becomes node  256 ′, etc., as is known to one skilled in the art of electromechanical engineering. 
   Mode of Operation of  FIG. 7   
   Control transistor  250  becomes conductive when output  212  (signal H 2 ) is high and output  206  (signal H 1 ) is low. As shown in  FIG. 3 , this corresponds to the rotation angle range 180-240° el., in which output  214  (signal H 3 ) is low so that control transistor  258  also conducts, since the condition H 2 */H 3  is met. 
   A current therefore flows through resistor  220  and transistor  258  to node  260 , from there through phase  22  to node  254 , and on through transistor  250  and comparator  202  of Hall IC  30  to ground  38 , so that winding phase  22  therefore receives current in this rotation angle range. At the same time, a current also flows through series-connected winding phases  24  and  26 . Commutation otherwise follows the pattern according to  FIG. 3 , to which the reader is therefore referred. 
   This circuit is particularly suitable for low-output motors in which a largely constant torque is required, as is characteristic of three-phase six-pulse motors. Since in this case the logic transistors are simultaneously the output stage transistors of the full bridge circuit, three power Hall ICs  30 ,  32 ,  34  and six transistors  250 ,  252 ,  256 ,  258 ,  262 ,  264  are sufficient, and the outlay in terms of components is therefore very low for a three-phase six-pulse motor with a full bridge circuit. It is thus possible either to accommodate the components on a very small circuit board or to implement additional functions on a somewhat larger circuit board, as demanded in each individual case by the customer. 
   Many variants and modifications are of course possible within the scope of the present invention, for example with the use of different transistor types in the power circuit, etc.