Abstract:
A device for regulating the voltage at which an automobile battery is charged by an alternator, having a control circuit and a power circuit, as well as an external management unit connected to the control circuit in order to transmit different regulation parameters to it, the power circuit also being connected to the external management unit and including means enabling it to generate by itself an excitation signal when the management unit delivers a control signal, the control circuit being activated to emit an excitation signal only when it detects the start of rotation of the alternator.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a device for regulating the voltage at which an automobile battery is charged by means of an alternator. 
     More particularly, the invention concerns a regulation device which includes—in addition to a regulator proper, which delivers excitation signals to the inductor of the alternator—a management unit external to said regulator and to the alternator, which controls said regulator. 
     BACKGROUND OF THE INVENTION 
     For producing such a regulation device, a structure of the type illustrated in FIG. 1 could be considered. 
     The regulator  1  is composed therein of a control circuit  2  and a power circuit  3 , the latter amplifying the excitation signals delivered by the control circuit  2 . The amplified excitation signals are applied to the inductor  4   a  of the alternator  4  (the rotor) in the form of a voltage Vex causing an excitation current Ies in said inductor  4   a.    
     The control circuit  2  is connected, by means of a wired connection  6 , to a computer  5 —for example that of the engine control—which constitutes the external management unit of the device. 
     With such a device, the regulation function is activated by the signal transmitted to the control circuit  2  by the computer  5 —via the connection  6 . This signal is for example a signal of the type referred to as pulse width modulation or PWM. 
     The control circuit  2  is then activated and transmits a pre-excitation signal to the power circuit  3 . The alternator  4  is consequently magnetised, so that the rotation of the alternator generates a phase signal (a voltage at the terminals of one of the windings). 
     As soon as the control circuit  2  has detected this phase signal, the pre-excitation signal is transformed into an excitation signal in order to regulate the battery voltage. 
     However, such a structure is not fully satisfactory. 
     The connection  2  may be subjected to electromagnetic interference caused by equipment internal or external to the vehicle (a radio telephone for example). Such interference is liable to produce, at the terminals of the connection  6 , overvoltages which may activate the control circuit  2  and, consequently, cause a pre-excitation current discharging the battery when the vehicle is stopped. It will be noted in particular that the discharge current may then be greater than 50 mA. 
     One aim of the invention is to mitigate this drawback and to propose a regulation device of the type which makes it possible to achieve the triggering of the regulator in normal mode and in degraded mode and offers good immunity against electromagnetic interference. 
     The recommended solution consists of magnetising the alternator circuit by means of an excitation current fixed by the control signal delivered by the external management unit, this control unit directly controlling the power stage of the regulator when the alternator is stopped. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention there is provided a device for regulating the voltage at which an automobile battery is charged by an alternator, including on the one hand a control circuit which comprises means for controlling the excitation of the inductor of the alternator as a function of the charging voltage, as well as means for detecting the start of rotation of the alternator, and on the other hand a power circuit which includes means for amplifying the excitation signals which are transmitted to it by the control circuit, said regulation device including an external management unit connected to the control circuit in order to transmit to it different regulation parameters, the power circuit also being connected to the external management unit and having means enabling it to generate by itself an excitation signal when the management unit delivers a control signal, the control circuit being adapted to be activated to emit an excitation signal only when the start of rotation of the alternator is detected. 
     This device is advantageously supplemented by the following different characteristics taken alone or in all their possible combinations: 
     the power circuit includes logic means which are connected to the means of detecting the start of rotation of the alternator, as well as to the external management unit, and which generate an excitation signal, by means of the amplification means, only when the external management unit delivers a control signal and no start of rotation of the alternator is detected; 
     the means of detecting the start of rotation of the alternator comprise a circuit for detecting the appearance of a voltage between two phases of the alternator; 
     the circuit for detecting this phase signal includes a signal detector which generates a high-level signal when the voltage which corresponds to this phase signal is greater than a given threshold, a timing device which receives the signal output from this detector and which is reset to zero when this signal is at its high level, a logic inverter whose input is connected to the output of the timing device and whose output is connected to a computer in the control circuit; 
     the power circuit includes a logic inverter which receives the signal emitted by the external management unit, and a logic NOR gate which receives the output of this logic inverter, as well as that of the logic inverter of the detection circuit; 
     the power circuit also includes a logic OR gate which receives as an input the output of said logic NOR gate, as well as the excitation control signal generated by the computer of the control circuit; 
     the control circuit and the power circuit includes means for regulating, when instructed by the external management unit, the voltage between two phases of the alternator; 
     the logic OR gate also receives as an input a signal generated by the means of regulating the voltage between two phases of the alternator; 
     the power circuit includes a second logic NOR gate whose output is sent as an input to the logic OR gate and which receives as an input a signal output from the computer of the detection circuit, as well as a signal output from the means detecting that the phases of the alternator have crossed one or more given voltage thresholds; 
     these means of detecting the crossing of a threshold or thresholds include a signal detector which generates a low-level signal when the phase voltages take peak values below a given threshold, a timing device which receives the signal output from this detector and which is reset to zero when this signal is at its high level, a logic inverter whose input is connected to the output of the timing device and whose output is transmitted to the second logic NOR gate. 
     According to a further aspect there is provided a device for regulating the voltage at which an automobile battery is charged by an alternator, including on the one hand a control circuit which comprises means for controlling the excitation of the inductor of the alternator as a function of the charging voltage, as well as means for detecting the start of rotation of the alternator, and on the other hand a power circuit which includes means for amplifying the excitation signals which are transmitted to it by the control circuit, said regulation device including an external management unit connected to the control circuit in order to transmit to it different regulation parameters, the power circuit also being connected to the external management unit and having means enabling it to generate by itself an excitation signal when the management unit delivers a control signal, the control circuit being adapted to be awakened to emit an excitation signal only when the start of rotation of the alternator is detected, wherein the power circuit includes logic means which are connected to the means of detecting the start of rotation of the alternator, as well as to the external management unit, and which generate an excitation signal, by means of the amplification means, only when the external management unit delivers a control signal and no start of rotation of the alternator is detected, wherein the means of detecting the start of rotation of the alternator comprise a circuit for detecting the appearance of a voltage between two phases of the alternator, and wherein the circuit for detecting this phase signal includes a signal detector which generates a high-level signal when the voltage which corresponds to this phase signal is greater than a given threshold, a timing device which receives the signal output from this detector and which is reset to zero when this signal is at its high level, a logic inverter whose input is connected to the output of the timing device and whose output is connected to a computer in the control circuit. 
     According to yet another aspect there is provided a device for regulating the voltage at which an automobile battery is charged by an alternator, including on the one hand a control circuit which comprises means for controlling the excitation of the inductor of the alternator as a function of the charging voltage, as well as means for detecting the start of rotation of the alternator, and on the other hand a power circuit which includes means for amplifying the excitation signals which are transmitted to it by the control circuit, said regulation device including an external management unit connected to the control circuit in order to transmit to it different regulation parameters, the power circuit also being connected to the external management unit and having means enabling it to generate by itself an excitation signal when the management unit delivers a control signal, the control circuit being adapted to be awakened to emit an excitation signal only when the start of rotation of the alternator is detected, wherein the power circuit includes logic means which are connected to the means of detecting the start of rotation of the alternator, as well as to the external management unit and which generate an excitation signal, by means of the amplification means, only when the external management unit delivers a control signal and no start of rotation of the alternator is detected, wherein the means of detecting the start of rotation of the alternator comprise a circuit for detecting the appearance of a voltage between two phases of the alternator, and wherein the circuit for detecting this phase signal includes a signal detector which generates a high-level signal when the voltage which corresponds to this phase signal is greater than a given threshold, a timing device which receives the signal output from this detector and which is reset to zero when this signal is at its high level, a logic inverter whose input is connected to the output of the timing device and whose output is connected to a computer in the control circuit, wherein the power circuit includes a logic inverter which receives the signal emitted by the external management unit, and a logic NOR gate which receives the output of this logic inverter, as well as that of the logic inverter of the detection circuit, wherein the power circuit also includes a logic OR gate which receives as an input the output of said logic NOR gate, as well as the excitation control signal generated by the computer of the control circuit, wherein the control circuit and the power circuit includes means for regulating, when instructed by the external management unit, the voltage between two phases of the alternator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other characteristics and advantages of the invention will also emerge from the description which follows. This description is purely illustrated and non-limitative. It must be read in connection with the accompanying drawings in which: 
     FIG. 1 already analysed, is a schematic representation of a regulation device including an external management unit; 
     FIG. 2 is a schematic representation of a regulation device according to one possible embodiment of the invention; 
     FIG. 3 is a diagram illustrating a possible circuit for a device of the type in FIG. 2; 
     FIG. 4 is a diagram illustrating a possible circuit for the phase signal detectors of the device of FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the description like features are referred to by like reference numerals. 
     The regulation device illustrated in FIG. 2 has a regulator  11 , which consists on the one hand of a control circuit  12  receiving a phase signal, which corresponds to a voltage between two phases of the armature  14   b  of the alternator  14  (inputs φ 1  and φ 2 ), and on the other hand of a power circuit  13  which delivers an excitation current to the inductor  14   a  of the alternator  14 . 
     This regulation device also has a management unit  15  which is connected both to the control circuit  12  and to the power circuit  13  (wired connections  16 ). 
     Unlike the regulation device of FIG. 1, the signal emitted by the unit  15  is not used to activate the control circuit  12 . The power circuit  13 , which is directly connected to the management unit  15 , generates by itself, on reception of the signal emitted by the management unit  15 , an excitation signal which magnetises the alternator. 
     As for the control circuit  12 , this is activated by the appearance of the phase signal between the inputs φ 1  and φ 2 , that is to say when the alternator  14  is in rotation—and therefore capable of charging the battery. 
     Thus an interference passing through the connections  16  cannot activate the regulator and cause a discharge of the battery when the alternator is stopped. 
     As long as the alternator  14  is not rotating, the phase signal does not exist and the control circuit  12  cannot be activated. An interference creates only a light excitation current (less than 1 mA) incapable of discharging the battery to an appreciable extent. 
     As soon as the alternator is in rotation and the control circuit  12  is activated, the control circuit  12  emits an excitation signal which is a function of different parameters of the signal emitted by the management unit  15  (frequency, amplitude, cycle ratio etc). Provision can advantageously be made for this signal, during the engine acceleration phase, to be a pre-excitation signal independent of the charging voltage, so as to reduce the torque of the alternator during this phase, the normal regulation of the charging voltage being effected only at the end of this start-up phase. 
     As illustrated in FIG. 3, in a possible embodiment, the control circuit  12  includes a computer  17 , a phase signal detection circuit  18  whose output is connected to an input RS of the computer  17 , a voltage filtering circuit  19  which connects the output voltage of the alternator to an input CAN of the computer  17  via a power supply terminal B+, as well as a phase signal regulation circuit  20 . 
     The computer  17  is connected by an input IN 1  to the management unit  15  by means of the connection  16 . 
     It also receives a clock signal (input CL 3 ). 
     The phase signal detection circuit  18  includes a signal detector  21 , which is described later in detail with reference to FIG.  4 . This detector  21  receives as an input the voltage between the inputs φ 1  and φ 2 . It generates a high-level signal when this voltage is above 0.6 volts. The signal RAZ 1  output from this detector  21  is sent to a timing device TEMP 1  (clock signal input CK 1 ), which is connected in series with a logic inverter Inv 1 , whose output is itself injected onto the input RS of the computer  17 . 
     A frequency divider DIV is connected between the output of the phase signal detector  21  and an input IN 2  of the computer  17 . 
     The filtering circuit  19  consists of a divider bridge (resistors R 1 , R 2  and R 3 ) and a capacitor C 1 . 
     The phase signal regulation circuit  20  also consists of a phase signal detector  22  connected to a timing device TEMP 2  (clock signal input CK 2 ) in series with a logic inverter Inv 2 . The phase detector  22  generates a signal RAZ 2 , which is at a high level when the voltage between the inputs φ 1  and φ 2  is above 7 volts. 
     The power circuit  13  for its part includes a circuit  23  for validating the signal emitted by the management unit  15 , a circuit  24  for validating the phase regulation, a collector  25  for the different excitation signals, as well as a power amplifier  26  which supplies the excitation current Iex to the inductor. This power circuit also includes an amplifier  26 . 
     The circuit  23  includes a logic inverter Inv 3  which receives the signal emitted by the management unit  15 , and a NOR gate (NOR 1 ) which receives on the one hand the signal output from the inverter Inv 3  and on the other hand the signal output from the inverter Inv 1 . 
     The circuit  24  for enabling the phase regulation includes a NOR gate (NOR 2 ), which receives as an input on the one hand the signal output from the inverter Inv 2  and on the other hand a signal emitted by the computer  17  at an output OUT 1 . 
     The collector  25  consists of a logic OR gate which receives the outputs of the gates NOR 1  and NOR 2 , as well as the excitation signal Exc generated by the computer  17 . 
     When the alternator is not rotating, the phase detector  21  does not initiate the timer TEMP 1 , whose output level remains at  1 . The output of the inverter Inv 1  remains at zero and the microcontroller  17  is not activated. Thus, when the management unit  15  delivers a signal PWM, the microcontroller  17  takes no account of it. On the other hand, this signal PWM is reconstituted at the output (Ext) of the gate NOR 1 . At the same time, the output (Exc) of the computer  17  remains at zero since the latter is not activated. For the same reason, the output OUT 1  is at level  1 , which forces the level  0  at the output (Exph) of the gate NOR 2 . The only excitation signal available for the amplifier  26  is therefore the signal PWM reconstituted at the output (Ext) of the gate NOR 1 . Consequently, when the alternator is not rotating, the excitation signal corresponds to the sole signal PWM. 
     When the alternator starts to rotate, the phase detector  21  detects the presence of a phase signal at the inputs φ 1  and φ 2 , and resets the timer TEMP 1  to zero. The output of the inverter Inv 1  goes to 1, as well as the input RS of the computer  17 , which is then activated. At the same time, the output of the gate NOR 1  goes to zero. Thus the computer  17  can deliver an excitation signal at the output Exc in order to control the current Iex in the inductor, via the amplifier  26 . 
     In addition, the computer  17  can, as a function of the signal which it receives from the management unit  15 , for example when the cycle ratio thereof takes a value in a given range, enable a phase regulation at 7 volts by setting the output OUT 1  at the zero level. If the voltage between φ 1  and φ 2  falls below 7 volts, the phase detector  22  does not reset to zero the timer TEMP 2 , whose output goes to the  1  level, which sets to zero the output of the inverter Inv 2 . If the output OUT 1  is also at zero, the output of the gate NOR 1  delivers an excitation signal Exph at the  1  level, which increases the excitation current Iex via the OR gate and the amplifier  26 . 
     The circuit DIV is a frequency divider which enables the computer  17  to use the frequency of the signal more easily as an input parameter. This possibility is used, for example, if the computer has a progressive charging or speed control function, as described notably in the patent FR 2 701 609. 
     FIG. 4 illustrates a possible circuit for the phase signal detectors  21  and  22 . 
     In this circuit, the detector  21  has a first bipolar transistor T 1  of the npn type, whose base is connected to the input φ 1  through a resistor R 1 . The emitter of this transistor T 1  is connected to the input φ 2  through a resistor R 2 . A diode D 1  is connected between the emitter and the base of this transistor T 1 . This diode D 1  conducts from said emitter to said base. 
     The collector of the transistor T 1  is connected to the base of a transistor T 2  of the pnp type, whose emitter is itself connected to a terminal supplying power at the voltage B+ output from the alternator  14 . The base of this transistor T 2  is also connected to said terminal B+ through a resistor R 3 . 
     The collector of the transistor T 2  is connected to earth through a resistor R 4 . It is also connected to a resistor R 5  connected at its other end to the cathode of a Zener diode Z 1 . The signal at the junction point between the Zener diode Z 1  and the resistor R 5  is the signal RAZ 1 , which is injected into the timer TEMP 1 . The Zener voltage of said diode Z 1  is 5 volts. 
     When the alternator is in rotation, the voltage Vφ 1 -Vφ 2  between the inputs φ 1  and φ 2  takes a positive value greater 0.6 volts, and the transistors T 1  and T 2  are conductive, so that the signal RAZ 1  resets the timer TEMP 1  to zero. Conversely, when the alternator is not in rotation, this voltage takes a value below 0.6 volts and said transistors T 1  and T 2  are non-conductive, so that the detector  21  does not re-initiate the timing. 
     The circuit of the detector  22  for its part includes a transistor T 3  of the pnp type, whose base is connected through a resistor R 6  to the input φ 2 . Its emitter is connected to the terminal B+ through a resistor R 7  This emitter is also connected to earth through a Zener diode Z 2 , which is conductive from earth to the terminal B+ and whose Zener voltage is 8.5 volts. As for its collector, this is connected through a resistor R 8  to the base of a transistor T 4 , which base is also connected by a resistor R 9  to the inpt φ 1 . The emitter of this transistor T 4  is connected to earth. Its collector is connected to the terminal B+ through a resistor R 10 . A Zener diode Z 3  is connected between earth and its collector whilst being conductive from earth to said collector. 
     The signal output from the collector of this transistor T 4  is the signal RAZ 2  injected into the timer TEMP 2 . 
     Thus, when the alternator is in rotation, this circuit ensures that the phase alternating signal φ 2  passes, at its peaks, a voltage greater than a given threshold, for example 7 volts. This condition ensures the correct functioning of an electronic tachometer equipping the vehicle and connected to this phase output, in particular in the case of a diesel engine. 
     More precisely, when the voltage at the terminal φ 2  is greater than the voltage of the Zener diode Z 2  less the emitter/base junction voltage of T 3  (that is to say if it is greater than the value of 7 volts cited as an example), then the transistor T 3  is non-conducting. If during this time the voltage at φ 1  is less than the emitter/base junction voltage of T 4 , (0.6 volts for example), then the latter remains non-conducting. The output RAZ 2  is therefore at a logic high level, which signals to the computer  17  that the peaks are passing the threshold of 7 volts and 0.6 volts and that the tachometer can function normally. 
     If on the other hand one of the aforementioned two conditions is no longer verified, T 4  becomes conducting, so that the output RAZ 2  goes to the logic low level, which has the effect, as indicated previously, of increasing the current in the field winding of the alternator so that the thresholds of 7 volts and 0.6 volts are once again passed rapidly. 
     Although preferred embodiments of the invention have been described, it will be understood that the invention is not to be limited to what has been described. Rather the invention extends to the full scope of the appended claims.