Abstract:
A control and power module for a rotating electric machine comprising a bridge of switches, a plurality of driver circuits for driving a bridge of switches, a control circuit and a plurality of communication connections between driver circuits and a control circuit. When the machine is in a rest mode, at least one connection of the plurality of communication connections is used for transmitting signals between the control circuit and the driver circuits for carrying out a function related to the rest mode of the machine, and when the machine is in the operational mode, all connections of the plurality of communication connections are used for transmitting signals between the control circuit and the driver circuits.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention concerns in general terms the control of polyphase rotary electrical machines, in particular the machines of this type that are reversible, such as alternator/starters. 
   The invention finds applications in particular in the field of motor vehicles. It applies more generally to any alternator or alternator/starter, motor/alternator or motor/alternator/starter, having a bridge of switches as voltage rectifying elements, driver circuits (“driver circuits” in English) to drive the switches, and at least one communication link between each driver circuit and a control circuit forming a regulator for the rectified voltage, and providing the control and management of starting. 
   2. Description of the Related Art 
   In a conventional alternator, which generally uses power diodes as voltage rectifying elements, the regulator (driven or not) usually includes a so-called self-starting function (“self-start” in English). This function is used to enable the alternator to output current, even if it has not received the instruction to do so (wire cut, connector broken or removed, etc), while the thermal engine of the motor vehicle is turning, causing the rotation of the alternator. This function may be based on the monitoring of a differential voltage between two phases of the alternator and the detection of a value above a predefined threshold. In the event of such detection, the regulator, which was in idle mode (in order to save on the energy drawn from the vehicle battery) is “woken up”, and the machine is started. 
   In the case of an alternator/starter, a motor/alternator or a motor/alternator/starter, but also an alternator using switches as voltage rectifying elements, it may be wished to use the same method. This method does however have the drawback of requiring two additional connections between the driver circuit and the control circuit. This is because, in order to have available two items of phase information at the control circuit, it is necessary to provide two additional connection terminals on the control or regulating module and also a phase output connection terminal at each power module including the switches. 
   SUMMARY OF THE INVENTION 
   To mitigate these drawbacks, it is proposed to take advantage of the specificities of the application to a machine using switches as voltage rectifying elements. 
   This is because a first aspect of the invention proposes a control and power module for a rotary electrical machine comprising: 
   a switch bridge; 
   a plurality of driver circuits associated with the switch bridge in order to drive the bridge; 
   a control circuit; and 
   a plurality of communication links between the driver circuits and the control circuit; control and power module in which: 
   in an idle mode of the machine, at least one connection of the plurality of connections is used to transmit signals between the control circuit and the driver circuits, useful for performing a function relating to an idle mode of the machine, and 
   in an active mode of the machine, all the connections of the plurality of connections are used to transmit signals, between the control circuit and the driver circuits, useful for performing a function relating to an active mode of the machine. 
   Thus the invention makes it possible to transmit, during the idle mode of the machine, information via communication links existing conventionally between the control circuit and each driver circuit, but previously used solely outside the idle mode (that is to say when the control circuit is awakened) for a function in active mode. 
   Thus the invention makes it possible to avoid the use of the additional interconnection means listed above. 
   In a preferential embodiment, a function relating to idle mode is a phase detection. 
   In addition, during a phase detection, the signals to be transmitted comprise at least a first and second item of phase information to be transmitted respectively via a first and second communication link. Thus the first and second communication links form part of the communication links used in active mode, and it is ensured that two items of phase information about the machine enter the control circuit for fulfilling the self-triggering function. 
   In a preferential embodiment, the first and second communication links are phased synchronization connections, the phased synchronization connections being adapted to transmit, during an active mode, phase synchronization signals to an associated driver circuit. Thus connections are used that already exist for each driver circuit, enabling each item of phase information to be transmitted. 
   In a first preferential embodiment, the plurality of communication links are bi-directional connections. Thus this makes it possible amongst other things to cause a fault to be sent back from a driver circuit to the control circuit by means of the communication circuit during an active mode. 
   In a second embodiment the plurality of communication links are control links. Thus this makes it possible to have driver circuits that are simpler to produce than in the case of bi-directional links, the driver circuits now being only in reception mode and therefore “slave”. 
   In a non-limiting embodiment, each first and second communication link is coupled to a respective end of the phase windings of the machine, an item of phase information issuing from a phase winding; and the associated driver circuit comprises switching means for isolating the link from the phase information outside idle mode. Thus the control circuit has available at least two items of phase information (N in reality, since the N driver circuits are preferably identical) during idle mode. As soon as the control circuit is awakened (by a protocol link, by a wake-up wire, or on detection of the rotation of the machine), the power supply to the driver circuit is activated. The latter are then awakened and inhibit the phase information on the corresponding communication link, thus providing normal functioning of the module. Thus the first and second communication links can transmit other information during active mode, for example phase synchronization signals or fault send-back information. 
   In a non-limiting embodiment, the switching means of the associated driver circuit comprise a controlled switch having: 
   a first main terminal connected to a communication link via a first resistor and to an output of the associated driver circuit intended to be coupled to one end of a phase winding via a second resistor, 
   a second main terminal coupled to an earth terminal, 
   and a control circuit coupled to a supply terminal of the associated driver circuit, the supply terminal receiving a supply voltage solely outside idle mode 
   This embodiment is particularly simple, and takes advantage of the fact that the driver circuit selectively receives a supply voltage, outside idle mode only. 
   In a non-limiting embodiment, the control circuit comprises a detection unit for receiving, at least in idle mode, first and second items of phase information and for sending a wake-up signal in the event of the detection of a phase difference between the first and second items of phase information. Thus the detection unit makes it possible to effect the phase detection and the self-initiation function. 
   In a non-limiting advantageous embodiment, the phase difference is detected by the detection of a differential amplitude between the first and second items of phase information. 
   In addition, in a non-limiting embodiment, the detection unit comprises threshold-type comparator means arranged to send the wake-up signal when the differential amplitude is above a given threshold value. 
   Thus the use of a differential amplitude between two phases makes it possible to obtain self-initiation at a lower engine speed and therefore a lower machine speed. Consequently self-initiation is more rapid than in the case where only one item of phase information is used. This is because, in the case of a single item of phase information, it is necessary to lower the given threshold value and for this it is necessary to use active components that consume additional energy. Moreover, using two items of phase information rather than only one makes it possible to obtain a module affording more stable self-initiation. There is less risk of unwanted self-initiation due to pulse-type disturbance of an item of phase information. 
   In a non-limiting embodiment, the threshold-type comparator means comprise a bipolar transistor. Thus, unlike an active circuit such as a comparator that comprises static consumption due in particular to an attributed power supply, the bipolar transistor consumes only when the given threshold value has been exceeded, ie when the bipolar transistor has a conducting junction. 
   In a non-limiting embodiment, the control circuit comprises switching means for isolating the detection unit from the first and second items of phase information outside idle mode. This thus makes it possible to deactivate the phase detection in active mode. 
   In a non-limiting embodiment, the switching means of the detection unit comprise, for each of the first and second communication links, a controlled switch having: 
   a first main terminal connected to the communication link via a first resistor and to an input dedicated to the detection unit via a second resistor, 
   a second main terminal connected to an earth terminal, and 
   a control terminal connected to a supply terminal of the control circuit via a resistor, the supply terminal receiving a supply voltage only outside idle mode. Thus, here also, particularly simple switching means exploit the fact that the control circuit has elements that are not supplied with power in idle mode. 
   A second aspect of the invention relates to a polyphase rotary electrical machine such as an alternator/starter or motor/alternator or a motor/alternator/starter, which comprises a control and power module according to the first aspect. 
   In a non-limiting embodiment, the rotary electrical machine is reversible. 
   A third aspect of the invention concerns a control method for a rotary electrical machine comprising: 
   a switch bridge; 
   a plurality of driver circuits associated with the switch bridge, for driving the bridge; 
   a control circuit; 
   a plurality of communication links between the driver circuits and the control circuit; the method comprises the steps according to which: 
   in an idle mode of the machine, signals are transmitted between the control circuit and the driver circuits via at least one link of the plurality of links, the signals being useful for fulfilling a function relating to idle mode, and 
   in an active mode of the machine, signals are transmitted between the control circuit and the driver circuits via all the links in the plurality of links, the signals being useful for fulfilling a function relating to active mode. 
   In a non-limiting embodiment, a function relating to idle mode is a phase detection. 
   In a non-limiting preferential embodiment, during a phase detection, at least first and second items of phase information are transmitted respectively via first and second communication links. 
   In a non-limiting preferential embodiment, the control circuit monitors the first and second items of phase information and wakes up in response to a given configuration of the first and second items of phase information. 
   In a non-limiting embodiment, a communication link being coupled to one end of a phase winding of the machine and an item of phase information coming from a phase winding, the communication link is isolated from the phase information outside of idle mode. 
   In a non-limiting embodiment, the method also comprises the steps of: 
   receiving, at least in idle mode, first and second items of phase information via a detection unit of the control circuit, and 
   sending a wake-up signal in the case of the detection of a phase difference between the first and second items of phase information. 
   In a non-limiting preferential embodiment, the phase difference is detected by the detection of a differential amplitude between the first and second items of phase information. 
   In addition, in a non-limiting embodiment, the wake-up signal is sent via the detection unit when the differential amplitude between the first and second items of phase information is greater than a given threshold value. 
   In a non-limiting embodiment, the detection unit being coupled to the first and second communication links, the detection unit is isolated from the first and second items of phase information outside idle mode. 
   These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other aspects, characteristics and advantages of the invention will also emerge from a reading of the following description. This is purely illustrative and must be read with regard to the accompanying drawings, in which: 
       FIG. 1  is a diagram of a polyphase rotary electrical machine according to the third aspect of the invention; 
       FIG. 2  is a partial diagram of an embodiment of a driver circuit included in the control and power module according to the first aspect of the invention; and 
       FIG. 3  is a partial diagram of an embodiment of a control circuit included in a control and power module of  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention will now be described in the context of its application to an alternator/starter, it being understood that it applies in a more general way to any polyphase rotary electrical machine such as those mentioned in the introduction. 
   An alternator/starter can function in starter mode, in order to start the thermal engine of the motor vehicle in which it is installed, or in alternator mode in order to rectify and regulate the voltage generated by the rotation of the thermal engine. The alternator/starter is thus a reversible machine. Outside these two active modes, the alternator/starter is in an idle mode. 
     FIG. 1  shows schematically an alternator/starter  300 . The alternator/starter  300  comprises: 
   an electromechanical part  200 , 
   an electronic part forming a control and power module  100 , the latter comprising a power module  1  and a control circuit  2 , and 
   two power supply terminals  301  and  302  respectively connected to the terminals  401  and  402  of a battery  400 . 
   In a non-limiting example, the battery  400  is, for example, a 12 volt battery. The terminal  401  is its positive terminal and the terminal  402  is its negative terminal. The electrical potentials on the terminals  401  and  402  are respectively denoted B+ and B−. Conventionally, the terminal  402  is connected to the chassis of the vehicle so that the potential B− is merged with the earth potential. The battery voltage, that is to say the difference in electrical potential between the terminals  401  and  402  of the battery  400 , is denoted VBAT. 
   The alternator/starter  300  also comprises a control input  303 , conventionally coupled to a starting switch (position with ignition key closed, not shown) of the vehicle in which the alternator/starter  300  is installed via a control box. When the starting switch is closed, the thermal engine of the vehicle is started. The alternator/starter being driven in rotation by the rotation of the thermal engine, this also causes the rotation of the alternator/starter. The closure of the starting switch normally closes the reception of a starting signal COMM on the input  303  of the alternator/starter  300 . It is to guard against a faulty reception of this signal COMM that the control signal  2  implements a self-initiation functionality. This functionality serves in particular when the machine is running in degraded mode. Thus it is possible to use this self-initiation function to permit, for example, a restarting on a slope, whether the ignition key be open or closed. 
   The electromechanical part  200  comprises: 
   an armature element  201 , and 
   a field winding element  202 . 
   In a non-limiting example, the armature  201  is the stator and the field winding  202  is the rotor. In addition, the stator comprises a given number N of phase windings, where N is preferably an integer number strictly greater than unity. In the example considered here, N is equal to 3. In other words, the alternator/starter according to the present example embodiment is a machine with a rotor field winding and a three-phase stator armature. In the example illustrated in  FIG. 1 , the phase windings of the armature element  201  are disposed in a ring configuration, a mounting in a delta for example. Nevertheless, this is not limiting, a configuration in a star also being able to be envisaged. 
   The control and power module  100  comprises: 
   a power module  1 , and 
   a control circuit  2  that can advantageously can be produced in the form of an ASIC (Application Specific Integrated Circuit). 
   In a non-limiting embodiment, the power module  1  comprises: 
   a switch bridge  3  having three branches, respectively associated with the three phase windings of the armature  201 , and 
   three driver circuits  10 ,  20  and  30  respectively associated with each of the three branches of the power transistor bridge  3 . 
   In a preferential embodiment, a switch comprises at least one power transistor. Loosely speaking, a power transistor bridge will therefore be spoken of hereinafter. 
   The driver circuits  10 ,  20  and  30  serve to drive the branch with which they are respectively associated. Hereinafter, the letters U, V and W, used as a suffix of reference signs or signal names, serve to distinguish each of the three phases of the armature  201 . The driver circuits  10 ,  20  and  30  are preferentially identical to one another, which simplifies the design and therefore the cost of the module  100 . They are for example produced in the form of respective monolithic circuits. 
   For reasons of simplicity, hereinafter and in the figures, the inputs and outputs of the circuit  2  and of the module  100  and the inputs of the driver circuits  10 ,  20  and  30  are referenced as the signals they receive or deliver, according to circumstances. A first branch  101  of the power transistor bridge  3 , associated with the driver circuit  10 , comprises a high MOS transistor MHSU (or “High Side” transistor) in series with a low MOS transistor MLSU (or “Low Side” transistor). These are for example NMOS transistors. The drain, control gate and source of the transistor MHSU are respectively connected to outputs DH, GH and SH of the driver circuit  10 . Likewise, the drain, control gate and source of the transistor MLSU are respectively connected to outputs DL, GL and SL of the driver circuit  10 . In addition, the drain of the transistor MLSU and the source of the transistor MHSU, which are connected together, form the output node of the branch  101 . This output  101  delivers a first phase control signal PHU. 
   Likewise, a second branch  102  of the power transistor bridge  3  comprises a high-side MOS transistor MHSV and a low-side MOS transistor MLSV of the same nature as the transistors MHSU and MLSU, and connected to the driver circuit  20  in the same way as the transistors MHSU and MLSU are connected to the driver circuit  10 . The source of the transistor MLSV and the drain of the transistor MHSV, which are connected together, form the output node of the branch  102 . This output  102  delivers a second phase control signal PHV. 
   Finally, the third branch  102  of the power transistor bridge  3  comprises a high-side MOS transistor MHSW and a low-side MOS transistor MLSW of the same nature as the transistors MHSU and MLSU, and connected to the driver circuit  30  in the same way as the transistors MHSU and MLSU are connected to the driver circuit  10 . The source of the transistor MLSW and the drain of the transistor MHSW, which are connected together, form the output node of the branch  103 . This output  103  delivers a third phase control signal PHW. 
   The phase synchronization signals PHU, PHV and PHW are available on respective outputs of the power module  1 . When the module  100  is installed in the alternator/starter  300 , these outputs are coupled to the phase windings of the armature  201 , via connections respectively  11 ,  12  and  13 . 
   The drain of the high-side transistor of each branch of the power transistor bridge  3 , namely the drains of the transistors MHSU, MHSV and MHSW, are connected to a first supply terminal of the circuit  1 , which receives the potential B+ while being connected to the terminal  301  of the alternator/starter. Likewise, the source of the low-side transistor of each branch of the power transistor bridge  3 , namely the sources of the transistors MLSU, MLSV and MLSW, are connected to a second supply terminal of the circuit  1 , which is at the potential B− while being connected to the terminal  302  of the alternator/starter. In addition, the power circuit  1  comprises a filtering capacitor CF connected between the supply terminals of the circuit  1 . 
   First and second supply terminals of the control circuit  2  are respectively at the potential B+ and at the potential B−, being respectively connected to the input  301  and the input  302  of the alternator/starter. The circuit  2  comprises outputs for delivering signals respectively SCU, SCV, SCW, VA, VD and ALG. These signals are transmitted via a plurality of communication links respectively  21  to  26 , on respective inputs of the power module  1 . Each of the signals VA, VD, and ALG is transmitted simultaneously on respective inputs of the driver circuits  10 ,  20  and  30 . 
   In a first embodiment, the plurality of communication links  21  to  26  are control links. That is to say the inks are used in active mode by the control circuit  2  for generating control signals to the driver circuits, for example the signals SCU, SCV, SCW in starter mode, signals that will be described in more detail below. 
   In a second preferential embodiment, the plurality of communication links  21  to  26  are bi-directional links. That is to say they are used in active mode by the control circuit  2  for transmitting signals to the driver circuits  10 ,  20  and  30  and by the driver circuits for transmitting signals to the control circuit  2 . Thus, for example in alternator mode, it is possible easily to perform a diagnosis function such as a transmission of a fault in which for example phase information is transmitted from a driver circuit to the control circuit in order to check whether or not a phase is short-circuited. 
   It should be noted that the signal VA is active (for example VA=1) in the active mode of functioning as an alternator, and inactive the rest of the time. Conversely, the signal VD is active in the active mode of functioning as a starter, and inactive the rest of its time. 
   When neither one nor other of the signals VA and VD is active, the control and power module  100  is in idle mode. 
   The signal ALG supplies a wake-up instruction to the driver circuit  10 ,  20  and  30  outside idle mode and at the same time it supplies to them a high voltage in active mode of the functioning in alternator or starter mode. This high voltage is equal to approximately 30 volts. 
   The signals SCU, SCV and SCW are phase synchronization signals generated in the active mode of functioning as a starter, to enable the driver circuits  10 ,  20  and  30  to control the phases of the machine appropriately, that is to say to start up and make the machine rotate in the correct direction. To this end, the signals SCU, SCV and SCW are supplied on an input SC of the driver circuits  10 ,  20  and  30  respectively. These signals are generated by the control module  2  according to information on the position of the rotor, which is supplied by position sensors, not shown. 
   In other words, in an active mode, starter or alternator modes in the example taken here of the alternator/starter  300 , all the connections of the plurality of connections  21  to  26  are used to transmit signals between the control circuit  2  and the driver circuits  10 ,  20 ,  30 , useful for fulfilling a function relating to an active mode of the alternator/starter, such as a starting or an output of current in starter or alternator mode. 
   The driver circuits  10 ,  20  and  30  also each comprise a first supply terminal VCC connected to the first supply terminal of the power module  1  for receiving the electrical potential B+, and a second supply terminal GND connected to the second supply terminal of the power module  1  for receiving the potential B−. 
   A multiplexing of at least two of the communication links  21 ,  22  and  23 , for fulfilling the self-initiation function, can be obtained by adapting the driver circuits  10 ,  20  and  30  and the control circuit  2 , as will now be presented with regard to the diagrams in  FIG. 2  and  FIG. 3 . 
   The means of the driver circuits  10 ,  20  and  30  that participate in the implementation of the invention or serve to explain its function will now be described with reference to the diagram in  FIG. 2 . This figure illustrates the case of the driver circuit  10 . However, all the driver circuits preferably being identical, the description that follows is valid for each of them. 
   The driver circuit  10  comprises a control unit  110  having two outputs respectively coupled to the outputs GH and GL of the circuit  10 . Thus the unit  110  generates the signals supplied outside the idle mode on the control gates of the transistors MHSU and MLSU in accordance with the normal active operating mode (starter mode if VD=1, or alternator mode if VA=1). The unit  110  has an input that is connected to the input SC in order to receive the phase synchronization signal SCU, via the communication link  21  connecting the driver circuit  10  to the control circuit  2  in a known fashion. The signal SCU is a logic signal (ie binary). The link  21  is thus a phase synchronization link, such a link making it possible to transmit a phase synchronization signal to the driver circuit  10  during an active mode. 
   Here, in addition, the communication link  21  is coupled to an associated end of the phase windings, phase information coming from a phase winding. To this end, it is coupled to the output SH and/or to the output DL of the driver circuit  10 , via two resistors R 11  and R 12  disposed in series. Thus, in addition to its normal function in starter mode consisting of transmitting a logic phase synchronization signal SCU, the link  21  also serves to transmit phase information issuing from a phase winding, from the circuit  10  to the module  2 , at least during idle mode. In other words, the communication link  21  also forms a phase monitoring link in idle mode. 
   The phase information transmitted is, in the non-limiting example taken here, an analog voltage. More particularly, it is a voltage derived from the phase voltage. In a variant, it will be possible to transmit phase information of another nature, for example a digital signal, but at the cost of complexity of the module  10  and therefore an increased manufacturing cost. 
   When the coupling between the link  21  and the output SH and/or the output DL of the circuit  10  is effected, the driver circuit  10  advantageously comprises switching means for isolating the link  21  from the phase voltage outside idle mode. These switching means are for example disposed between the link  21  and the output SH and/or the output DL of the circuit  10  to which it is coupled. 
   In a non-limiting embodiment, these means comprise a transistor M 12 , for example an NMOS transistor, forming a controlled switch. The drain D 12  of a transistor M 12  is connected to the phase monitoring link  21  via the first resister R 11 , and to the output SH/DL of the driver circuit  10  via the second resistor R 12 , output SH/DL coupled to the end of the associated phase winding. Its source S 12  is connected to the earth terminal GND of the circuit  10 . Finally, its control gate G 12  is coupled to the supply input ALG of the circuit  10 , which receives the supply voltage ALG solely outside idle mode. For example, the gate G 12  is connected to the input ALG via a resistor R 13 . Finally, a resistor R 14  is connected between the output SH and/or the output DL of the circuit  10  on the one hand and its earth terminal GND on the other hand. 
   In a non-limiting example embodiment, the values of the resistors R 11 -R 14  are equal to 10 kΩ. 
   The functioning of the driver circuit is as follows. 
   In idle mode (VA=0 and VD=0), the power supply to the driver circuit is cut off in order to ensure static consumption limited to leakage currents. To this end, the signal ALG corresponds to a zero voltage. As a result the transistor M 12  is off. There is then found on the link  21  a voltage derived from the phase voltage available on the output SH/DL (through the bridge voltage divider formed by the resistors R 11 , R 12  and R 14 ). 
   As soon as the pilot circuit is awakened (on detection of a supply voltage ALG supplied by the control circuit  2 ) the power supply is established. The transistor M 12  is then closed (by the voltage ALG via the “pull-up” resistor R 13  on its control gate G 12 ), thus isolating the link  21  from the phase voltage available on the output SH/DL. The transmission of the phase synchronization signal SCU provided in starter mode can take place. It will be recalled that the phase synchronization signal SCU stems from the rotor position information, the signal generally being in digital form. 
   In the control circuit  2 , means of the same type as the switching means of the driver circuits as presented above are provided for allowing multiplexing of the communication link  21 . This thus allows transmission of a phase information signal (from a driver circuit  10  to the control circuit  2 ) or a phase synchronization signal (from the control circuit  2  to a driver circuit  10 ). 
   In addition, means are provided effecting the awakening of the control or regulating circuit  2  by detection of a potential difference between two phase voltages higher than a threshold voltage Vbe (for example between 0.6 V and 1 V). 
   Thus, in an idle mode, at least one link  21  of the plurality of links  21  to  26  is used for transmitting signals, here phase information, between the control circuit  2  and the driver circuit  10 , useful for fulfilling a function relating to idle mode of the alternator/starter  300 , the function here being a phase detection, and when a phase is detected, the signals to be transmitted comprise first and second items of phase information (voltages) to be transmitted respectively via a first  21  and second communication link  22 . 
     FIG. 3  depicts schematically an example embodiment of the means of the control circuit  2  that participate in the implementation of the invention. 
   As will be seen in detail below, the control circuit  2  is constructed so as, in an idle mode of the machine, to monitor at least first PHU and second PHV items of phase information transmitted by the driver circuits  10 ,  20 ,  30  via respectively first  21  and second  22  phase monitoring links, and to wake up in response to a given configuration of the first and second phase voltages, and in that the first and second phase monitoring links are included in the plurality of communication links used for controlling the driver circuits  10 ,  20 ,  30  in a given active mode. The items of phase information are derived from phase voltages. Thus, during an idle mode, phase voltages PHU, PHV, PHW are transmitted over respective communication links SCU, SCV, SCW existing between the control circuit  2  and each driver circuit  10 ,  20 ,  30 , but previously used solely outside idle mode for controlling driver circuits in active mode. The control circuit then has at least two phase voltages available during idle mode. In the control circuit, a unit for detecting the rotation of the machine monitors them to permit an awakening of the control circuit and self-initiation of the machine. As soon as the control circuit is awakened, the supply voltage ALG of the control circuits is activated. The latter are then awakened and inhibit the phase voltage on the corresponding communication link, thus ensuring normal functioning in active mode. 
   To this end, the circuit  2  comprises: 
   control unit  27 , and 
   a unit  28  for detecting the rotation of the machine. 
   The unit  27  is adapted to ensure the functioning of the machine according to the various active modes thereof. In particular, in the active mode functioning as an alternator, it forms a regulator of the voltage rectified by the branches of the transistor bridge, via means that are not shown, which are known per se. In the active mode of functioning as a starter, it delivers the phase synchronization signals (“sensor signals”) SCU, SCV and SCW, which are transmitted to the driver circuits respectively  10 ,  20  and  30 , via communication links respectively  21 ,  22  and  23 . For reasons of simplicity, only one example embodiment of the means coupling the unit  27  to the links  21  and  22  have been shown, knowing that identical or similar means couple the unit  27  to the link  23 . 
   The function of the unit  28  is to ensure the awakening of the control circuit  2  and therefore to permit the self-initiation of the machine, on detection of the rotation thereof from one or more items of phase information. To this end, the unit  28  is powered even in idle mode, from the battery voltage VBAT. In addition it is constructed so as to send a wake-up signal SWU that is delivered to the control unit  27  in response to a given configuration of the phase information item or items. 
   To this end, the unit  28  can be coupled, at least in idle mode, to two phase monitoring links in order to receive two respective items of phase information. These items of phase information come for example from respective phase windings. It may thus be a case of phase voltages collected at two respective phase windings. In this case, the unit  28  can be constructed so as to generate the wake-up signal SWU in the event of detection of a phase difference between these phase voltages, in particular a phase difference higher than a given threshold. Thus the unit  28  can receive, at least in idle mode, a first PHU and second PHV item of phase information and send a wake-up signal SWU in the event of detection of a phase difference between the first and second items of phase information. 
   In a preferential embodiment, the phase difference is detected by the detection of a differential amplitude between the first and second items of phase information. In addition, the detection unit  28  comprises comparator means with threshold arranged to send the wake-up signal SWU when the differential amplitude is higher than a given threshold value. 
   The unit  28  can then advantageously be strictly the same as for a conventional alternator regulator. 
   In the example embodiment given here, the phase monitoring links are, in idle mode, merged with the phase synchronization links  21  and  22  provided for enabling the control circuit  2  to transmit the sensor signals SCU and SCV to the driver circuits respectively  10  and  20  in starting mode. 
   In addition, in a non-limiting preferential embodiment, the detection unit  28  is here coupled to these links  21  and  22 . In this case, when such coupling is effected, the control circuit  2  comprises switching means for isolating the detection unit  28 , outside idle mode, from the phase information (voltages) possibly present on these links  21  and  22 . 
   In a non-limiting embodiment, for each of the phase monitoring links  21  and  22 , the aforementioned switching means of the unit  28  can comprise a controlled switch MC 12  or MC 22 , in the form for example of an NMOS transistor. The drain respectively DC 12  or DC 22  of this transistor MC 12  or MC 22  is connected to the link respectively  21  or  22 , via a first resistor respectively RC 11  or RC 21 . It is also connected to a dedicated input, respectively  281  or  282 , of the detection unit  28  via a second resistor respectively RC 12  or RC 22 . Its source respectively SC 12  or SC 22  is connected to earth. And its control gate respectively GC 12  or GC 22  is connected to the supply terminal of the control circuit via respectively a resistor RC 13  or RC 23 , the supply terminal receiving a supply voltage Vdd (for example equal to 5 volts) solely outside idle mode. 
   Thus the transistors MC 12  and MC 22  are in a conducting state (switch closed) when the control circuit is powered (Vdd=5 V), that is to say in the active mode of functioning as a starter or alternator. In this way, the inputs  281 ,  282  of the unit  28  are earthed. Conversely, the transistors MC 12  and MC 22  are in an off state (switch open) when the control circuit is not powered (Vdd=0 V), that is to say in idle mode. In this way, the inputs  281  and  282  of the unit  28  receive the phase voltages transmitted by the driver circuits respectively  10  and  20 . 
   In one embodiment, the value of the resistors RC 11 -RC 13  and RC 21 -RC 23  are equal to 10 kΩ. 
   A possible embodiment of the unit  28 , in bipolar technology, will now be described, still with reference to the diagram in  FIG. 3 . In this embodiment, the unit  28  comprises a differential pair of transistors Q 1  and Q 2 , such as npn bipolar transistors. The emitters of the transistors Q 1  and Q 2  are connected to the inputs respectively  282  and  281  of the unit  28 . In addition, the emitter of Q 1  is connected to the base of Q 2  and conversely the emitter of Q 2  is connected to the base of Q 1 . The collectors of Q 1  and Q 2  are at the battery voltage VBAT, via resistors respectively R 3  and R 4 . An output stage comprises a transistor Q 3 , for example a pnp bipolar transistor, the base of which is connected to the collector of Q 2 , the emitter of which is at VBAT and the drain of which is connected to earth via a resistor R 5 . The output of the unit  28 , which delivers the signal SWU, is taken from the collector of Q 3 . The high level of the wake-up signal SWU is regulated via the resistors R 4  and R 5 . For reasons of symmetry, a stage similar to the output stage comprises a transistor Q 4 , also a pnp bipolar transistor, the base of which is connected to the collector of Q 1 , the emitter of which is connected to VBAT and the drain of which is connected to earth via a resistor R 6 . 
   In an example embodiment, the values of the resistors R 3  and R 4  are for example equal to 200 kΩ, and those of the resistors R 5  and R 6  are for example equal to 10 kΩ. 
   Thus arranged, the pair of transistors Q 1  and Q 2  forms a threshold comparator for generating the wake-up signal SWU by detecting the phase difference between the voltages present on the inputs  281  and  282 . In other words, the wake-up signal SWU is generated (here set to the high state) when the differential amplitude between the voltages returned on the inputs  281  and  282  (issuing from the phase windings of the machine) is greater than a given threshold value. This threshold value corresponds here to the voltage Vbe (base-emitter voltage shown in  FIG. 3 ) of the transistors Q 1  and Q 2 . 
   It should be noted that, in this embodiment, the phase information coming from the third driver circuit  30  is not used in idle mode. Nevertheless it is preferable to have identity of the driver circuits respectively associated with the three phases by equipping them all with means for the transmission of the associated phase information. This makes it possible not to introduce asymmetry between the driver circuits, which simplifies their design and testing and promotes symmetry of functioning between the phases of the machine. 
   The invention has been described above in a preferred but non-limiting embodiment. In particular, the phase monitoring links are not necessarily the phase synchronization links SC. It may be a case of all communication links between the control circuit  2  and the driver circuits  10 ,  20  and  30 , used in a known fashion to drive the driver circuits in the active mode of functioning as a starter or alternator. 
   The hardware implementation of the circuit  100  is also not limited to that described with reference to  FIG. 1 . In particular a single monolithic circuit can contain the three driver circuits  10 ,  20  and  30 . 
   Finally, the active mode can comprise other operating modes such as an motor mode in which the machine  300  supplies torque to the thermal engine, the torque being for example used as an aid to the acceleration of the thermal engine 
   While the process and product herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise process and product, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.