JP5447261B2 - Vehicle generator - Google Patents

Description

  The present invention relates to a vehicular generator mounted on a passenger car, a truck, or the like.

  The vehicular generator supplies charging power and operating power to a battery and various electric loads via a charging line connected to an output terminal. If the output terminal or the battery terminal is disconnected during the power generation operation of this vehicle generator, a transient high voltage called a load dump is generated. The voltage generated at this time may reach 100 V or more depending on the output current or the like. The high voltage generated in this way causes damage to various elements in the electric load and the vehicular generator, and some measures are required. As a conventional technique for taking such measures, for example, a low-side element of a bridge circuit of a vehicle generator is configured by a MOS transistor, and when a phase voltage of the vehicle generator exceeds a reference voltage when a load dump occurs, 2. Description of the Related Art A vehicular generator is known in which a protection operation for suppressing generation of a high voltage is performed by turning on a MOS transistor (see, for example, Patent Document 1). In this vehicular generator, when the MOS transistors as the low-side elements of the bridge circuit are turned on to turn the phase voltage below the reference voltage again, the MOS transistors are turned off again, and the normal rectification operation by the bridge circuit is resumed. It has become so.

  In addition, as another conventional technique for suppressing the high voltage when a load dump occurs, the control mode of the power MOSFETs on the upper arm side (high side side) and the lower arm side (low side side) are reversed in phase when high voltage is detected. There is known a vehicular generator that is changed (see, for example, Patent Document 2). When the high voltage at the time of load dump occurrence is eliminated, the control mode is returned from the reverse phase to the normal state.

JP-A-9-219938 (page 5-9, FIG. 1-14) JP 2003-244864 A (page 4-10, FIG. 1-16)

  By the way, in the vehicular generator disclosed in Patent Document 1, when the phase voltage exceeds the reference voltage, the MOS transistor as the low-side element is turned on, so that this phase voltage is temporarily reduced, and this phase voltage is reduced. When the voltage falls below another reference voltage, the MOS transistor is turned on again. This on / off of the MOS transistor is repeated until the energy of the G pulse voltage is sufficiently consumed. Thus, repeating ON / OFF of the MOS transistor cuts off the current flowing in the stator coil connected to the MOS transistor, so that a high voltage is generated in the stator coil. Since the voltage also exceeds the reference voltage, there is a problem that the generation of the high voltage cannot be terminated quickly. Further, in the vehicle generator disclosed in Patent Document 1, when the phase voltage exceeds the reference voltage, the MOS transistor as the low-side element is turned on / off faster than the period of the rectification operation. There is a problem that it takes time until the energy of the voltage is sufficiently consumed. Also in this respect, the generation of the high voltage could not be terminated quickly.

  Further, in the vehicular generator disclosed in Patent Document 2, the on / off state of each of the power MOSFETs of the upper arm and the lower arm is switched when the protection operation is started when the load dump occurs or when the protection operation is canceled. Therefore, there is a problem that a surge voltage is generated at the time of switching if a current flows through the stator coil to which these power MOSFETs are connected. In particular, the on / off switching timings of the power MOSFETs of the upper arm and the lower arm vary somewhat from element to element, and when they are simultaneously turned off, the current flowing through the stator coil is cut off. A high surge voltage will be generated.

  The present invention was created in view of the above points, and an object of the present invention is to provide a vehicular generator that can quickly terminate the generation of a high voltage during load dump.

  In order to solve the above-described problems, a vehicle generator according to the present invention includes an armature winding having two or more phase windings and a plurality of lower arms configured by switching elements having diodes connected in parallel. A switching unit that rectifies the induced voltage of the armature winding, a control unit that instructs on / off of the switching element, and an output voltage of the switching unit, the output voltage being a first threshold value When the voltage exceeds the voltage, the control unit is instructed to turn on the switching element constituting the lower arm, and the output voltage is lower than the first threshold voltage after exceeding the first threshold voltage. When the voltage becomes lower than the second threshold voltage, the control unit is instructed to turn off the switching element constituting the lower arm after waiting for the arrival of a timing suitable for suppressing the generation of the surge voltage. A load dump protection determination unit; and an on-resistance setting unit that sets an on-resistance of the switching element in accordance with a magnitude of a current that flows through the switching element when the switching element is turned on exceeding the first threshold voltage The load dump protection determination unit determines whether the timing is suitable for suppressing the occurrence of surge voltage based on the voltage across the switching element for which the on-resistance is set by the on-resistance setting unit. Yes.

  When performing a protective operation to prevent the occurrence of high voltage during load dump by turning on the switching element of the lower arm when a load dump occurs, the operation to cancel the protective operation after the occurrence of high voltage is suppressed By waiting for the timing suitable for suppressing the generation of surge voltage, normal rectification operation can be resumed avoiding the timing of surge voltage generation, and high voltage generation at load dump can be quickly It becomes possible to end. In addition, since the on state of the lower arm switching element is maintained until the output voltage decreases, the switching element does not frequently turn on / off, and no high voltage is generated due to repeated on / off. In addition, the energy generated in the phase winding can be quickly extinguished, and the generation of a high voltage at the time of load dump can be terminated quickly. Furthermore, since the ON resistance of this switching element is variably set according to the magnitude of the current flowing through the switching element, when determining the timing suitable for suppressing the occurrence of surge voltage based on the voltage across the switching element, An appropriate voltage at both ends can be obtained regardless of the magnitude of the current, and the timing suitable for suppressing the occurrence of the surge voltage can be reliably determined.

  Further, it is desirable that the above-described on-resistance setting unit sets the on-resistance to be small when the current flowing through the switching element is large, and sets the on-resistance to be large when the current flowing through the switching element is small. As a result, it is possible to obtain a voltage at both ends suitable for timing determination regardless of the magnitude of the current.

  In addition, the above-described on-resistance setting unit desirably detects the magnitude of the current flowing through the switching element by observing the voltage across the switching element. Since the voltage across the switching element changes depending on the current flowing through the switching element, the magnitude of the current flowing through the switching element can be easily detected by observing the voltage across the switching element.

  Further, the above-described on-resistance setting unit has the magnitude of the excitation current and the number of rotations of the exciting current flowing in the field winding that magnetizes the field pole of the rotor immediately before the switching element is turned on exceeding the first threshold voltage. It is desirable to estimate the magnitude of the current flowing through the switching element based on the height. The value of the return current flowing through the switching element when the lower arm switching element is turned on corresponds to the exciting current and the rotational speed of the vehicular generator immediately before the occurrence of the load dump. Therefore, the magnitude of the current flowing through the switching element can be easily estimated by acquiring the immediately preceding excitation current and the rotational speed.

  In addition, the load dump protection determination unit described above configures the lower arm after detecting that the output voltage has exceeded the first threshold voltage and waiting for the arrival of a timing suitable for suppressing the occurrence of the surge voltage. It is desirable to instruct the control unit to turn on the switching element. As a result, not only when the protection operation is cancelled, but also when shifting to the protection operation, the protection operation can be performed while avoiding the timing at which the surge voltage is generated.

  The timing for suppressing the generation of the surge voltage described above is a timing other than the timing at which current flows from the phase winding connected to the switching element to the switching element when the switching element constituting the lower arm is turned on. It is desirable that In particular, the timing for suppressing the generation of the surge voltage described above is the timing at which current flows from the switching element to the phase winding connected to the switching element when the switching element constituting the lower arm is turned on. Is desirable. Thereby, interruption | blocking of the electric current which flows into the phase winding connected to the switching element in which an on-off state switches, and sudden change can be prevented, and it can suppress that a high surge voltage generate | occur | produces in a phase winding.

  Further, the switching element described above is a MOS transistor, and the load dump protection determination unit includes a MOS voltage detection unit that detects the source-drain voltage of the MOS transistor, and the MOS based on the detected source-drain voltage. An energization direction detection unit that detects the direction of current flowing through the MOS transistor when the transistor is turned on, and a timing determination unit that determines a timing for suppressing generation of a surge voltage based on a detection result by the energization direction detection unit; It is desirable to provide. Since the MOS transistor has a predetermined source-drain voltage even when it is turned on, it is possible to detect the direction of the current by detecting this voltage, and to reliably determine the timing for suppressing the generation of the surge voltage. it can.

  The on-resistance setting unit described above preferably changes the channel resistance of the source / drain voltage by variably setting the voltage of the drive signal input to the gate of the MOS transistor. By configuring the switching element with a MOS transistor, the channel resistance of the source / drain voltage as the on-resistance can be easily variably set by varying the voltage (gate voltage) of the drive signal input to the gate.

  The timing for suppressing the occurrence of the surge voltage is preferably the timing when the source-drain voltage of the MOS transistor with respect to the source side becomes 0 V or less. This makes it possible to reliably and easily determine the direction of the current flowing through the MOS transistor. Further, since it is not necessary to add a shunt resistor for current detection in series with the MOS transistor, there is no loss due to the shunt resistor, and the power generation efficiency during normal power generation can be increased accordingly.

  The timing for suppressing the generation of the surge voltage is preferably a timing delayed for a predetermined period after the source-drain voltage of the MOS transistor with respect to the source side becomes 0 V or less. In particular, the above-described predetermined period is desirably a period corresponding to ¼ of the period of the induced voltage of the phase winding. Due to the LC component of the circuit, there may be a phase shift between the detected voltage and current. Specifically, even when the source-drain voltage is 0 V, the current may be 0 A or more. Even in such a case, it is possible to reliably release the protection operation at the timing when the current flows from the source to the drain.

  The timing for suppressing the generation of the surge voltage described above is such that the direction of the current flowing through the switching element after the output voltage exceeds the first threshold voltage and the switching element constituting the lower arm is turned on is It is desirable that the timing be synchronized with a cycle of timing that changes from the direction of flowing from the phase winding to the switching element to the direction of flowing from the switching element toward the phase winding. As a result, even if the output voltage drops and becomes lower than the second threshold voltage, it is possible to suppress the generation of the surge voltage even when the determination cannot be made at a timing at which the generation of the surge voltage can be suppressed. can do.

  In addition, the load dump protection determination unit described above instructs the control unit to forcibly turn off the switching element constituting the lower arm when the arrival of the timing suitable for suppressing the occurrence of the surge voltage cannot be detected. It is desirable to do this. Even if the on-resistance of the switching element is variably set, if the arrival of a timing suitable for suppressing the occurrence of surge voltage cannot be detected, the switching element is forcibly turned off and the protection operation is released. In such a case, since the current that is cut off is small even when the switching element is turned off at any timing, a large surge voltage is not generated, and as a result, the surge voltage is suppressed and the high voltage during load dumping It is possible to end the occurrence quickly. In addition, by forcibly turning off the switching element, the protection operation can be terminated early and the power generation operation (rectification operation) can be resumed, leading to an improvement in power generation efficiency.

  The timing for forcibly issuing the instruction is after the output voltage becomes lower than the second threshold voltage lower than the first threshold voltage after exceeding the first threshold voltage. It is desirable that a predetermined time has elapsed. By setting the timing for forcibly releasing the protection operation to be after a predetermined time, the protection operation can be surely terminated and the normal rectification operation can be performed.

  The predetermined time described above is preferably a variable value. By setting the predetermined time to a variable value, it is possible to use an appropriate value in the situation at that time. Alternatively, the predetermined time described above is preferably a fixed value. By setting the predetermined time to a fixed value, it is easy to determine the timing when the predetermined time has elapsed.

  Further, it is desirable that the predetermined time described above is set to a long value at a low rotation and a short value at a high rotation. The timing suitable for suppressing the occurrence of surge voltage arrives at a cycle corresponding to the rotation speed, so by setting the length of the predetermined time according to the rotation speed, it is possible to set a short time considering the rotation speed, and early The protection operation can be terminated.

  The load dump protection determination unit described above preferably detects the rotational speed based on the voltage of the phase winding. This eliminates the need to add parts to detect the number of revolutions and to input / output signals to / from the power generation control device that controls the excitation current, thus simplifying the configuration and wiring and reducing the size. It becomes.

  In addition, the above-described predetermined time is such that the field winding that magnetizes the field pole of the rotor before the output voltage exceeds the first threshold voltage and an instruction to turn on the switching element constituting the lower arm is issued. It is desirable to set a short value when the exciting current flowing through the electrode is large and a long value when the exciting current is small. The fact that the excitation current before entering the protection operation is large means that much energy is generated during load dump. Therefore, it is considered that the current flowing through the phase winding increases, and it becomes easier to detect the timing suitable for suppressing the generation of the surge voltage. On the contrary, the fact that the exciting current before entering the protection operation is small means that the energy generated during load dumping is so small that it is difficult to detect the timing suitable for suppressing the generation of the surge voltage. Considering these, by setting the length of the predetermined time according to the excitation current, it is possible to set a short time in consideration of the excitation current, and the protection operation can be terminated early.

It is a figure which shows the structure of the generator for vehicles of one Embodiment. It is a figure which shows the structure of a rectifier module. It is a figure which shows the detailed structure of a control circuit. It is a figure which shows the transition state which transfers to protection operation at the time of load dump occurrence, and returns to normal rectification operation | movement again after that. It is a figure which shows the phase voltage of the generator for vehicles. It is a figure which shows the structure of a load dump protection determination part. It is a figure which shows the relationship between an output voltage and the determination result by a threshold voltage determination part. It is a figure which shows the relationship between the source-drain voltage and a reference voltage. It is explanatory drawing which shows the operation | movement principle which variably sets the gate-source voltage Vgs by a Vgs setting part. It is a figure which shows the relationship between the exciting current and rotation speed immediately before shifting to protection operation, and the current which flows into the MOS transistor after shifting to protection operation. It is a figure which shows the structure of the modification using the Vgs setting part which acquires an exciting current and rotation speed, and operate | moves. It is a figure which shows the specific example of the output of a MOS voltage detection part when only one rectifier module transfers to protection operation. It is a figure which shows the modification of the load dump protection determination part which cancels | releases protection operation | work forcibly. It is a figure which shows the other modification of a load dump protection determination part. It is a figure which shows the other modification of a load dump protection determination part. It is a figure which shows the other modification of a load dump protection determination part.

  Hereinafter, a generator for vehicles of one embodiment to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a vehicle generator according to an embodiment. As shown in FIG. 1, the vehicle generator 1 of this embodiment includes two stator windings (armature windings) 2, 3, a field winding 4, two rectifier module groups 5, 6, and power generation. A control device 7 is included. Two rectifier module groups 5 and 6 correspond to a switching unit.

  One stator winding 2 is a multiphase winding (for example, a three-phase winding composed of an X-phase winding, a Y-phase winding, and a Z-phase winding), and is wound around a stator core (not shown). It is disguised. Similarly, the other stator winding 3 is a multi-phase winding (for example, a three-phase winding composed of a U-phase winding, a V-phase winding, and a W-phase winding). The stator winding 2 is wound at a position shifted by 30 degrees in terms of electrical angle. In the present embodiment, a stator is constituted by these two stator windings 2 and 3 and the stator core.

  The field winding 4 is wound around a field pole (not shown) disposed opposite to the inner peripheral side of the stator core to constitute a rotor. The field pole is magnetized by passing an exciting current. The stator windings 2 and 3 generate an alternating voltage by a rotating magnetic field generated when the field pole is magnetized.

  One rectifier module group 5 is connected to one stator winding 2 to form a three-phase full-wave rectifier circuit (bridge circuit) as a whole, and the alternating current induced in the stator winding 2 is converted into direct current. Convert to current. The rectifier module group 5 includes rectifier modules 5X, 5Y, and 5Z corresponding to the number of phases of the stator winding 2 (three in the case of a three-phase winding). The rectifier module 5 </ b> X is connected to the X-phase winding included in the stator winding 2. The rectifier module 5 </ b> Y is connected to a Y-phase winding included in the stator winding 2. The rectifier module 5Z is connected to the Z-phase winding included in the stator winding 2.

  The other rectifier module group 6 is connected to one stator winding 3 to form a three-phase full-wave rectifier circuit (bridge circuit) as a whole, and the alternating current induced in the stator winding 3 is converted into direct current. Convert to current. The rectifier module group 6 includes a number of rectifier modules 6U, 6V, and 6W corresponding to the number of phases of the stator winding 3 (three in the case of a three-phase winding). The rectifier module 6U is connected to a U-phase winding included in the stator winding 3. The rectifier module 6V is connected to a V-phase winding included in the stator winding 3. The rectifier module 6 </ b> W is connected to the W-phase winding included in the stator winding 3.

  The power generation control device 7 is an excitation control circuit that controls the excitation current that flows through the field winding 4, and the output voltage of the vehicle generator 1 (the output voltage of each rectifier module) is adjusted by adjusting the excitation current. The voltage is controlled to be Vreg. For example, the power generation control device 7 stops supplying the excitation current to the field winding 4 when the output voltage becomes higher than the adjustment voltage Vreg, and the field when the output voltage becomes lower than the adjustment voltage Vreg. By supplying an exciting current to the magnetic winding 4, the output voltage is controlled to become the adjustment voltage Vreg. The power generation control device 7 is connected to the ECU 8 (external control device) via a communication terminal and a communication line, and uses bidirectional serial communication (for example, a LIN (Local Interconnect Network) protocol) with the ECU 8. LIN communication) and transmit or receive a communication message.

  The vehicle generator 1 of the present embodiment has such a configuration, and details of the rectifier module 5X and the like will be described next.

  FIG. 2 is a diagram illustrating a configuration of the rectifier module 5X. The other rectifier modules 5Y, 5Z, 6U, 6V, and 6W have the same configuration. As shown in FIG. 2, the rectifier module 5X includes two MOS transistors 50 and 51 and a control circuit 54. The MOS transistor 50 has an upper arm (high side) whose source is connected to the X-phase winding of the stator winding 2 and whose drain is connected to the electrical load 10 and the positive terminal of the battery 9 via the charging line 12. Switching element. The MOS transistor 51 is a switching element on the lower arm (low side) whose drain is connected to the X-phase winding and whose source is connected to the negative terminal (earth) of the battery 9. A series circuit composed of these two MOS transistors 50 and 51 is arranged between the positive terminal and the negative terminal of the battery 9, and an X-phase winding is connected to the connection point of these two MOS transistors 50 and 51. A diode is connected in parallel between the source and drain of each of the MOS transistors 50 and 51. This diode is realized by a parasitic diode (body diode) of the MOS transistors 50 and 51, but a diode as another component may be further connected in parallel. Note that at least one of the upper arm and the lower arm may be configured using a switching element other than a MOS transistor.

  FIG. 3 is a diagram showing a detailed configuration of the control circuit 54. As shown in FIG. 3, the control circuit 54 includes a control unit 100, a power source 102, a battery voltage detection unit 110, an operation detection unit 120 and 130, a load dump protection determination unit 140, a temperature detection unit 150, drivers 170 and 172, and a communication. A circuit 180 is provided.

  The power supply 102 starts operation when a predetermined phase voltage is generated in the X-phase winding of the stator winding 2 as the engine is started, and supplies the operating voltage to each element included in the control circuit 54. This operation itself is the same as the operation conventionally performed in the power generation control device 7, and can be realized by using the same technique.

  The driver 170 has an output terminal (G1) connected to the gate of the high-side MOS transistor 50, and generates a drive signal for turning on and off the MOS transistor 50. Similarly, the driver 172 has an output terminal (G2) connected to the gate of the low-side MOS transistor 51, and generates a drive signal for turning the MOS transistor 51 on and off. In this embodiment, at least the driver 172 corresponding to the low-side MOS transistor 51 has not only an on / off instruction, but also a voltage level (gate-source voltage Vgs) of a drive signal applied to the MOS transistor 51. Setting / change is performed by the control unit 100. A specific example of setting / changing the gate-source voltage Vgs will be described later.

  The battery voltage detection unit 110 (battery voltage detection means) includes a differential amplifier and an analog-digital converter (AD) that converts the output into digital data. The output terminal of the vehicular generator 1 and the charging line 12 outputs data corresponding to the voltage of the positive terminal of the battery 9 connected via the terminal 12.

  The operation detection unit 120 includes a differential amplifier and an analog-to-digital converter (AD) that converts the output into digital data, and the source-drain voltage of the high-side MOS transistor 50 (FIGS. 2 and 2). 3 corresponding to the voltage between the B and C terminals 3). Based on this data, the control unit 100 monitors the operating state of the MOS transistor 50 corresponding to the driving state of the driver 170, and appropriately controls the MOS transistor 50 and detects a failure.

  The operation detection unit 130 includes a differential amplifier and an analog-digital converter (AD) that converts the output into digital data. The operation detection unit 130 includes a source-drain voltage (FIGS. 2 and 3) of the MOS transistor 51 on the low side. Data corresponding to the voltage between the C and D terminals). Based on this data, the control unit 100 monitors the operating state of the MOS transistor 51 corresponding to the driving state of the driver 172, and appropriately controls the MOS transistor 51 and detects a failure.

  The load dump protection determination unit 140 monitors the output voltage (B terminal voltage) of the vehicular generator 1 (rectifier module groups 5 and 6), and the B terminal voltage is a first threshold voltage for determining the occurrence of load dump. An instruction (protection start instruction) to start the protection operation after exceeding V1 (for example, 20V) is performed, and then the B terminal voltage is lowered by this protection operation and is lower than the first threshold voltage V1. After falling below the threshold voltage V2 (for example, 16.5 V), an instruction to stop the protection operation and resume normal rectification operation (rectification resumption instruction) is issued. For example, the load dump protection determination unit 140 is preferably configured by an analog circuit in which various active elements and passive elements are combined because it is necessary to perform quick processing. The control unit 100 executes the protection operation and the rectification operation after the protection operation is released in accordance with the protection start / rectification restart instruction from the load dump protection determination unit 140. Details of the configuration and protection operation of the load dump protection determination unit 140 will be described later.

  The temperature detection unit 150 includes a constant current source, a diode, a differential amplifier, and an analog-digital converter (AD) that converts the output into digital data, and copes with a forward voltage drop of the diode that changes with temperature. Output data. The control unit 100 detects the temperature of the rectifier module 5X based on this data.

  The communication circuit 180 is a communication unit that performs communication similar to that of the power generation control device 7, and is commonly connected to a communication terminal and a communication line that connect between the power generation control device 7 and the ECU 8, and the ECU 8 and other rectifiers. Bidirectional serial communication (for example, LIN communication using the LIN protocol) is performed with the module, and a communication message is transmitted or received.

  For example, considering a case where a communication message is transmitted / received to / from the ECU 8 at a communication frequency of about 20 ms per communication, communication can be performed 50 times per second. Therefore, even if six communication modules 5X and the like are added in this embodiment and the transmission / reception of communication messages therefor increases, communication messages and diagnostic information including the power generation state between the power generation control device 7 and the ECU 8 are displayed. It can be said that there is no problem in power generation control for transmitting and receiving communication messages.

  The rectifier module 5X and the like according to the present embodiment have such a configuration. Next, details of the protection operation when a load dump occurs and the operation of returning from the protection operation to the normal power generation (rectification) state will be described. .

  FIG. 4 is a diagram showing a transition state in which the operation shifts to the protection operation when a load dump occurs and then returns to the normal rectification operation. In FIG. 4, “rectification” indicates a rectification operation performed in a normal time when no load dump occurs, and “protection” indicates a protection operation performed when a load dump occurs. FIG. 5 is a diagram showing the phase voltage of the vehicular generator 1. FIG. 5 (A) shows the normal phase voltage, and FIG. 5 (B) shows the phase voltage when the load dump occurs. It is shown.

  When the terminal voltage of the battery 9 (the output voltage of the vehicle generator 1) is Vbatt, and the source-drain voltage when the MOS transistors 50 and 51 are on is α, in normal time when no load dump occurs, for example, the X phase Synchronous rectification is performed in which the high-side MOS transistor 50 is turned on when the phase voltage Vx of the winding exceeds Vbatt + α, and the low-side MOS transistor 51 is turned on when the phase voltage Vx drops below −α. (FIG. 5A).

In such a state, when the connection between the output terminal of the vehicle generator 1 and the charging wire 12 or the connection between the positive terminal of the battery 9 and the charging wire 12 is disconnected, the stator winding of the vehicle generator 1 A load dump in which the phase voltages of 2 and 3 are temporarily increased occurs (FIG. 5B). Since the phase voltage V _{LD at} this time is higher than the terminal voltage Vbatt of the battery 9 (for example, 100 V or more), the rectifier module 5X in the vehicular generator 1, the power generation control device 7, or various electric loads 10 are applied. In order to protect, after going through the procedure of “Preparation for protection”, it shifts to a protection operation (FIG. 4).

  Specifically, the process proceeds to the “protection preparation” procedure when the phase voltage exceeds the first threshold voltage V1. This protection preparation is an operation for determining an optimum timing for entering the protection operation, and a protection start instruction is issued in accordance with a timing at which generation of a surge voltage when entering the protection operation can be suppressed. Further, assuming that a lead storage battery having a rated voltage of 12V is used as the battery 9, the first threshold voltage is set to 20V, for example. The first threshold voltage V1 is set to a value at which the electric load 10 does not cause an abnormality such as a failure. Even if the output voltage temporarily rises to the first threshold voltage, the electric load 10 10 can maintain normal operation.

  In the present embodiment, when the output voltage VB of the rectifier module 5X (= the output voltage of the vehicle generator 1) exceeds 20 V when a load dump occurs, the low-side MOS transistor 51 is turned on, and at the same time, the high-side MOS The transistor 50 is turned off and the protection operation is performed. Thereafter, the off / on states of these MOS transistors 50 and 51 are continued until the high voltage associated with the load dump is eliminated. During this protection operation, the phase voltage shifts in the range of −α to + α (−0.1 V to +0.1 V) as indicated by Vp in FIG.

  In the range indicated by A in FIG. 5, the high-side MOS transistor 50 is on and the low-side MOS transistor 51 is off before the protection operation shifts. If the switch is turned off instantaneously, a large surge voltage may be generated in the phase winding. For example, the on / off switching timing of the MOS transistors 50 and 51 actually varies from element to element, and if only the timing for turning off the high-side MOS transistor 50 that has been turned on becomes slightly earlier, A large surge voltage is generated because the current that is flowing is interrupted.

  In the range indicated by B in FIG. 5, no current flows through the phase winding, but the potential difference between the source and drain is large in the low-side MOS transistor 51, and when the MOS transistor 51 is turned on, the current instantaneously Therefore, a large surge voltage is generated against the change in the phase current.

  As described above, since there is a possibility that a large surge voltage is generated when the protection operation is started when the protection operation is in the ranges indicated by A and B in FIG. 5, in the present embodiment, it is included in the range indicated by C in FIG. 5. After confirming that this is done, the protection operation is started. In “protection preparation”, when it is within the range indicated by C, it is determined that it is the optimum timing to enter the protection operation.

  On the other hand, when the high voltage generated at the time of load dump is eliminated and the normal operation is restored from the protection operation, the procedure of “recovery preparation” is similarly performed. Specifically, when the output voltage of the rectifier module 5X, which has become a high voltage at the time of load dump, drops again and falls below the second threshold voltage, the procedure proceeds to the “recovery preparation” procedure. This recovery preparation is an operation for determining an optimum timing for entering a normal rectification operation, and a rectification restart instruction is issued in accordance with a timing at which generation of a surge voltage upon entering the rectification operation can be suppressed. When the commutation restart instruction is issued, the control unit 100 turns off the low-side MOS transistor 51, and then the normal rectification operation (synchronous rectification control operation) by the control unit 100 is performed.

  Incidentally, during the protection operation, the low-side MOS transistor 51 is always on, and a phase voltage indicated by Vp in FIG. 5B is generated. In this state, turning off the low-side MOS transistor cuts off a large phase current that has been flowing through the MOS transistor 51 in the range indicated by A and B. Occur. Therefore, in the present embodiment, the normal rectification operation is started after confirming that it is included in the range indicated by C in FIG. In “recovery preparation”, when it is within the range indicated by C, it is determined that it is the optimum timing to enter the rectifying operation.

  Next, details of the load dump protection determination unit 140 that performs the protection preparation operation and the recovery preparation operation will be described. FIG. 6 is a diagram illustrating a configuration of the load dump protection determination unit 140. As shown in FIG. 6, the load dump protection determination unit 140 includes a B voltage detection unit 141, a threshold voltage determination unit 142, a MOS voltage detection unit 143, a conduction direction detection unit 144, timing determination units 145 and 146, and a Vgs setting. Part 190 is provided.

  The B voltage detector 141 detects the output voltage VB of the rectifier module 5X (the output voltage of the vehicle generator 1). The threshold voltage determination unit 142 determines whether or not the output voltage VB is higher than the first threshold voltage V1, and the output voltage VB once higher than the first threshold voltage V1 is the second threshold voltage. It is determined whether or not the voltage has become lower than the threshold voltage.

  FIG. 7 is a diagram illustrating the relationship between the output voltage VB and the determination result by the threshold voltage determination unit 142. In FIG. 7, the horizontal axis represents the output voltage VB, and the vertical axis represents the determination result of the threshold voltage determination unit 142. As shown in FIG. 7, the threshold voltage determination unit 142 changes the output from a low level (L) to a high level when the output voltage VB increases and exceeds a first threshold voltage V1 (for example, 20 V). Switch to level (H). Further, when the output voltage VB once exceeding V1 becomes low and becomes lower than the second threshold voltage V2 (for example, 16.5 V), the output is switched from the high level to the low level.

  The MOS voltage detector 143 detects the source-drain voltage Vds (voltage between the C-D terminals in FIGS. 2 and 3) of the low-side MOS transistor 51. The energization direction detector 144 determines the direction of the current flowing between the source and drain when the MOS transistor 51 is turned on based on the source-drain voltage Vds of the MOS transistor 51 detected by the MOS voltage detector 143. .

In a state when a load dump occurs and before the protection operation is started (before the low-side MOS transistor 51 is turned on), the phase voltage V _LD corresponding to the range indicated by A or B in FIG. Become. Therefore, if it is desired to know whether or not it is in the range indicated by C (whether or not current flows in the direction opposite to the forward direction of the diode connected in parallel to the MOS transistor 51 when the MOS transistor 51 is turned on), What is necessary is just to check whether or not the phase voltage V _LD , that is, the source-drain voltage Vds of the MOS transistor 51 is lower than a predetermined reference voltage Vref lower than 0V. That the source-drain voltage Vds is lower than the reference voltage Vref indicates that the phase voltage V _LD is in the range indicated by C in FIG. 5. In this case, the output of the energization direction detection unit 144 is Become high level.

  Actually, the MOS voltage detector 143 accurately detects a voltage in the range of −0.1 to +0.1 V, and the energization direction detector 144 uses the reference voltage Vref near 0 V to accurately compare the voltages. Is difficult. For this reason, the MOS voltage detection unit 143 outputs the voltage Vds ′ after the detected source-drain voltage Vds is amplified with a predetermined gain to convert the voltage level, and the energization direction detection unit 144 outputs the voltage Vds ′. Is used to compare the voltage.

  FIG. 8 is a diagram showing the relationship between the source-drain voltage Vds 'and the reference voltage Vref'. In FIG. 8, the vertical axis indicates the converted voltage Vds', and the horizontal axis indicates the source-drain voltage Vds before conversion. Since the voltage comparison range in the energization direction detection unit 144 is the source-drain voltage Vds included in the range of −0.1 to +0.1 V, this range is amplified, for example, 20 times. In the example shown in FIG. 8, −0.1 V corresponds to 0 V, +0.1 V corresponds to +5 V, and the voltage therebetween linearly corresponds to 1: 1. When the source-drain voltage Vds is lower than −0.1 V or higher than +0.1 V, the output voltage of the MOS voltage detector 143 is clipped (fixed) to 0 V or +5 V. ). For example, the reference voltage Vref ′ = 2.5V (Vds = 0V) is set. In order to accurately determine the timing included in the range indicated by C in FIG. 5, the reference voltage Vref 'needs to be set to a value close to + 5V.

  The energization direction detection unit 144 compares the output voltage Vds ′ of the MOS voltage detection unit 143 with the reference voltage Vref ′, and sets the output to a high level when Vds ′ is lower than Vref ′, and sets the output to a low level when Vds ′ is high. To. Note that the energization direction detection unit 144 may delay the timing for setting the output to a high level for a predetermined period. In general, a phase shift may occur between the detected source-drain voltage Vds and the actual current flowing between the source and drain due to the LC component of the circuit such as the rectifier module 5X. Specifically, even when the source-drain voltage is 0 V, the current may be 0 A or more. In consideration of such a case, the timing of changing to the high level may be delayed for a predetermined period. As the predetermined period, for example, a period corresponding to ¼ of the period of the induced voltage (phase voltage) of the phase winding is used.

  One timing determination unit 145 changes the output of the energization direction detection unit 144 to a high level after the output of the threshold voltage determination unit 142 changes from a low level to a high level, that is, with the occurrence of a load dump. When the output voltage VB becomes higher than the first threshold voltage V1 and is determined to be in the range indicated by C in FIG. 5B, the output is set to the high level. The high level output of the timing determination unit 145 corresponds to the “protection start instruction”, and when this protection start instruction is output, the control unit 100 drives the driver 170 to perform the high-side MOS transistor 50. Is turned off and the driver 172 is driven to turn on the low-side MOS transistor 51, thereby starting a protection operation when a load dump occurs.

  The other timing determination unit 146 changes the output of the energization direction detection unit 144 to a high level after the output of the threshold voltage determination unit 142 changes from a high level to a low level, that is, with the occurrence of a load dump. When it is determined that the output voltage VB once exceeding the first threshold voltage V1 is again lower than the second threshold voltage V2 and is within the range indicated by C in FIG. To high level. The high level output of the timing determination unit 146 corresponds to the “rectification resumption instruction”. When this rectification resumption instruction is output, the control unit 100 drives the driver 172 to activate the low-side MOS transistor 51. Turn off. Thereafter, the control unit 100 resumes the synchronous rectification control operation.

  Note that the case where the timing at which the output of the energization direction detection unit 144 changes to the high level is delayed for a predetermined period is intended to be the timing corresponding to the vicinity of the center of the range indicated by C in FIG. In this regard, at least one of the timing determination units 145 and 146 has a function of delaying the timing of changing to the high level for a predetermined period, which is applicable to both of the two timing determination units 145 and 146. You may make it change.

  Incidentally, as shown in FIG. 5, when the MOS transistor 51 is turned on, the source-drain voltage Vds of the MOS transistor 51 alternately changes between −0.1 V and +0.1 V. When the current Id flowing through the capacitor is large, and the current Id decreases, the amplitude value of the source-drain voltage Vds decreases. When the amplitude value of the source-drain voltage Vds becomes small, it becomes difficult to determine the energization direction in the energization direction detection unit 144, although it depends on the set value of the reference voltage Vref '. Assuming such a case, in the present embodiment, a Vgs setting unit 190 as an on-resistance setting unit is provided.

  The Vgs setting unit 190 shifts to a protection operation when a load dump occurs and the MOS transistor 51 is turned on according to the magnitude of the current flowing between the source and drain of the MOS transistor 51 when the MOS transistor 51 is turned on. The channel resistance between the source and the drain, which is the on-resistance, is variably set. Specifically, the channel resistance is variably set by changing the voltage (gate-source voltage) Vgs of the drive signal input to the gate of the MOS transistor 51. When the gate-source voltage Vgs is set by the Vgs setting unit 190, the control unit 100 instructs the driver 172 to set the gate-source voltage Vgs, and a drive signal having the gate-source voltage Vgs is generated. The MOS transistor 51 is turned on by being supplied from the driver 172 to the MOS transistor 51.

  FIG. 9 is an explanatory diagram showing the operation principle of variably setting the gate-source voltage Vgs by the Vgs setting unit 190. For example, the gate-source voltage Vgs when turning on the MOS transistors 50 and 51 in a normal rectifying operation is set to 10 V, and the same gate-source voltage Vgs is set when the protection operation is performed when a load dump occurs. When the MOS transistor 51 is turned on, the source-drain voltage Vds ′ changes in the range of 0V to 5V when the current flowing between the source and drain of the MOS transistor 51 is greater than or equal to a predetermined value. . Two types of reference voltages Vref1 and Vref2 are set, which are separated from the center of the amplitude of the source-drain voltage Vds' by Δ1, Δ2 (Δ1 <Δ2). When the current flowing between the source and drain of the MOS transistor 51 is large, the voltage Vds ′ changes beyond the two reference voltages Vref1 and Vref2, but the current flowing between the source and drain of the MOS transistor 51 is different. When the voltage Vds ′ becomes smaller and the amplitude of the voltage Vds ′ becomes smaller, the voltage Vds ′ changes beyond one reference voltage Vref1, but the voltage Vds ′ is always smaller than the other reference voltage Vref2.

  In this way, when only the magnitude relationship between the voltage Vds ′ and the reference voltage Vref1 periodically changes, and the magnitude relationship between the voltage Vds ′ and the reference voltage Vref2 does not change periodically, the Vgs setting unit 190 performs the MOS The voltage Vgs of the drive signal input to the transistor 51 is changed to a new value (for example, 1V lowered to 9V) lower than the previous 10V by a predetermined value. By reducing the voltage Vgs, the channel resistance between the source and drain of the MOS transistor 51 increases, so that the magnitude relationship between the voltage Vds ′ and the reference voltages Vref1 and Vref2 changes periodically. When the current flowing between the source and drain of the transistor 51 is further reduced, the voltage Vgs is lowered again based on the same operation principle.

  In addition to decreasing the voltage Vgs multiple times as the current decreases, Vgs may be decreased only once. For example, there is a case where the voltage Vgs is changed to 6.5 V when Vgs is set to 10 V in the initial state of shifting to the protective operation and then the current flowing between the source and drain of the MOS transistor 51 becomes small. Conceivable.

  As described above, the vehicular generator 1 according to this embodiment is a case where a protection operation is performed to prevent the generation of a high voltage at the time of load dump by turning on the low-side MOS transistor 51 at the time of load dump. The operation to cancel the protection operation after the occurrence of high voltage is suppressed is performed after the arrival of the timing suitable for suppressing the generation of surge voltage, so that the normal rectification operation can be performed avoiding the timing at which the surge voltage occurs. It is possible to resume the operation, and it is possible to quickly terminate the generation of a high voltage during load dump. In addition, since the ON state of the lower-arm switching element is maintained until the output voltage VB decreases, these MOS transistors 50 and 51 do not repeat ON / OFF frequently, and the high level associated with repeated ON / OFF is high. There is no voltage generation, and energy generated in the phase winding can be quickly extinguished, and high voltage generation at the time of load dump can be terminated quickly. Further, since the ON resistance of the MOS transistor 51 is variably set according to the magnitude of the current flowing through the MOS transistor 51, the timing suitable for suppressing the occurrence of surge voltage is determined by the voltage across the MOS transistor 51 (source / drain). When performing based on the inter-voltage Vds), it is possible to obtain an appropriate voltage between both ends regardless of the magnitude of the current, and to reliably determine a timing suitable for suppressing the occurrence of the surge voltage.

  The Vgs setting unit 190 decreases the on-resistance when the current flowing through the MOS transistor 51 is large (increases the gate-source voltage Vgs), and increases the on-resistance when the current flowing through the MOS transistor 51 is small (gate · Since the source-to-source voltage Vgs is set to be low, a voltage at both ends suitable for timing determination can be obtained regardless of the magnitude of the current.

  Also, the Vgs setting unit 190 easily detects the magnitude of the current flowing through the MOS transistor 51 by observing the voltage across the MOS transistor 51 (source-drain voltage Vds), specifically by observing the change in amplitude. can do.

  Also, not only when the protection operation is released, but also when switching to the protection operation, the presence or timing of the protection operation transition is determined for each rectifier module corresponding to each phase winding, and the timing at which a surge voltage is generated individually It is possible to perform protection operation while avoiding the above.

  Further, as a timing for suppressing the generation of the surge voltage, when the MOS transistor 51 is turned on, a current flows from the phase winding connected to the MOS transistor 51 to the MOS transistor 51 (A and B in FIG. 5). A timing other than the range shown in (1) is set. As a result, it is possible to prevent the current flowing through the phase winding connected to the MOS transistor 51 whose ON / OFF state is switched or a sudden change from occurring, and to suppress the occurrence of a high surge voltage in the phase winding.

  Further, since the MOS transistor 51 has a predetermined source-drain voltage even when it is turned on, it is possible to detect the direction of the current by detecting this voltage, and to reliably determine the timing for suppressing the generation of the surge voltage. can do.

  By the way, in this embodiment, the Vgs setting unit 190 detects the magnitude of the current flowing through the MOS transistor 51 based on the output voltage Vds ′ of the MOS voltage detection unit 143. You may make it determine the magnitude of.

  For example, the Vgs setting unit 190 is based on the magnitude of the excitation current If (Duty value or current instruction value) flowing through the field winding 4 and the level of the rotation speed N immediately before the transition to the protection operation when a load dump occurs. Thus, the magnitude of the current flowing through the MOS transistor 51 after the transition to the protection operation is estimated.

  FIG. 10 is a diagram showing the relationship between the duty value (on-duty value) and the rotational speed N of the exciting current If just before the transition to the protection operation and the current flowing through the MOS transistor 51 after the transition to the protection operation. . As shown in FIG. 10, there is a close relationship between the excitation current If (Duty value) and the rotation speed N and the current value. By obtaining the excitation current If and the rotation speed N, the MOS is transferred after the protection operation is shifted. The value of the current flowing through the transistor 51 can be estimated.

  FIG. 11 is a diagram showing a configuration of a modified example using the Vgs setting unit 190A that operates by obtaining the excitation current If and the rotation speed N. Since the control unit 100 performs the synchronous rectification control operation based on the output data of the operation detection units 120 and 130 before entering the protection operation, the control unit 100 detects the rotational speed N necessary for the control operation.

  The Vgs setting unit 190A takes in the rotation speed N immediately before the protection operation detected by the control unit 100, and supplies the excitation current If (duty value or current instruction value) immediately before the protection operation via the control unit 100 and the communication circuit 180. After taking in from the power generation control device 7 and estimating the magnitude of the current flowing through the MOS transistor 51 after shifting to the protective operation based on the taken-in rotation speed N and excitation current If, the MOS transistor 51 is based on the estimated magnitude of the current. The channel resistance between the source and the drain, which is the on-resistance, is variably set. Note that the variable setting of the channel resistance (variable setting of the gate-source voltage Vgs) in this case is continuous in correspondence with the rotational speed N and the excitation current If, in addition to the case where the variable is variable in two or more stages. The case where it is variable is conceivable. Thus, by obtaining the excitation current If and the rotation speed N immediately before the transition to the protection operation from the control unit 100, the magnitude of the current flowing through the MOS transistor 51 can be reduced without adding a special configuration for current detection. Can be easily estimated.

  In the present embodiment, since the transition timing to the protection operation is determined for each rectifier module, a defective portion (for example, the output terminal of the vehicle generator 1 is disconnected or the battery 9 Depending on whether the positive terminal is disconnected) or the magnitude of the phase current at that time, only one rectifier module corresponding to the one-phase phase winding may shift to the protective operation. For example, when one stator winding 2 is considered, only the rectifier module 5X may shift to the protective operation, and the other rectifier modules 5Y and 5Z may not shift to the protective operation. During the protection operation in such a case, only the low-side MOS transistor 51 of the rectifier module 5X is turned on, and the low-side MOS transistors 51 of the other rectifier modules 5Y and 5Z continue to be in the off state. For this reason, in the lower arms (low side) of the rectifier modules 5Y and 5Z in the off state, a current flows only through the diode connected in parallel with the MOS transistor 51, and the rectifier module 5X in the on state. For the MOS transistor 51, a phenomenon has been confirmed in which current does not flow in the direction from the source to the drain (the direction in which the current flows from the MOS transistor 51 toward the X-phase winding). In such a case, the source-drain voltage Vds of the MOS transistor 51 that is turned on becomes 0 V or more.

FIG. 12 is a diagram illustrating a specific example of the output of the MOS voltage detection unit 143 when only one rectifier module shifts to the protection operation. As shown in FIG. 12, when the output voltage VB exceeds the first threshold voltage V1 at t _{0 and} only one rectifier module shifts to the protection operation, the output voltage Vds ′ of the MOS voltage detector 143 is always 2 .5V (0V for Vds) or more is maintained. Assuming such a case, the reference voltage Vref ′ used in the energization direction detection unit 144 may be replaced with a reference voltage Vref ″ higher than 2.5V. Thus, even when only one rectifier module shifts to the protection operation, even when the B terminal voltage exceeding the first threshold voltage V1 becomes equal to or lower than the second threshold voltage V2, it is normal. It is possible to return to the rectifying operation.

  In addition, the phenomenon in which the protection operation by only one rectifier module described above is performed may occur when the protection operation is canceled and the normal rectification operation is restored. That is, since the timing for returning to the normal rectifying operation is also determined for each rectifier module, when the protective operation is canceled first for two of the three rectifier modules, only the remaining one rectifier module is protected. Will be maintained. In this way, it has been confirmed that the source-drain voltage Vds of the MOS transistor 51 of the rectifier module maintaining the protective operation may not be lower than 0V.

  Even in such a case, since the output voltage VB is already lower than the second threshold voltage V2, if it is clear that it is in the range of C shown in FIG. The normal rectification operation may be restored. For example, during the protection operation by all the rectifier modules, the timing at which the output of the energizing direction detection unit 144 alternately repeats the high level and the low level and changes from the low level to the high level is indicated by C in FIG. Corresponds to the vicinity of the left end of the range. The rotation speed before and after releasing the protection operation can be considered to be substantially constant for several rotations. Therefore, the timing determination unit 146 detects and holds the period T in which the output of the energization direction detection unit 144 changes to a high level, and immediately before the B terminal voltage becomes lower than the second threshold voltage V2. A timing is determined by determining when a cycle T or an integral multiple (2T, etc.) has elapsed from the timing when the output of the energization direction detection unit 144 changes from low level to high level (when Vds ′ becomes lower than Vref ′). The output of the determination unit 146 may be changed to a high level (a rectification restart instruction is output). Similarly, the timing determination unit 145 detects and holds the period T in which the output of the energization direction detection unit 144 changes to a high level, and energizes immediately before the output voltage VB exceeds the first threshold voltage V1. Timing determination is performed by determining when the period T or an integral multiple (2T, etc.) has elapsed from the timing when the output of the direction detection unit 144 changes from low level to high level (when Vds 'becomes lower than Vref'). The output of the unit 145 may be changed to a high level (a protection start instruction is output).

  By the way, when the phase current flowing during the protection operation is small (when the excitation current just before entering the protection operation is small or when the rotation speed is low), the phase voltage Vp as shown in FIG. Thus, it is difficult to determine the return timing based on the phase voltage Vp. In such a case, in this embodiment, the Vgs setting unit 190 variably sets the on-resistance of the MOS transistor 51. However, when it is still difficult to determine the return timing (causes a load dump to occur). The protection operation may be forcibly released in the case where the output voltage is disturbed and it is difficult to determine depending on the defective part or the electric load 10 connected at that time.

  FIG. 13 is a diagram illustrating a modification of the load dump protection determination unit that forcibly releases the protection operation. The load dump protection determination unit 140A illustrated in FIG. 13 includes a B voltage detection unit 141, a threshold voltage determination unit 142, a MOS voltage detection unit 143, a conduction direction detection unit 144, timing determination units 145 and 146, a timer 147, and a Vgs setting. Part 190 is provided. The load dump protection determination unit 140A is different from the load dump protection determination unit 140 shown in FIG. 6 in that a timer 147 is added.

  In the example shown in FIG. 5B, the source-drain voltage Vds when the MOS transistor 51 is on changes in the range of −0.1 V to +0.1 V, but the output voltage is disturbed. It is conceivable that the source-drain voltage Vds ′ does not become lower than the reference voltage Vref ′ when preparing for recovery. Then, the output of the energization direction detection unit 144 does not change to a high level, the output of the timing determination unit 146 also maintains a low level, and a rectification restart instruction is not issued. In consideration of such a case, a timer 147 is added.

  The timer 147 starts measurement when the output of the threshold voltage determination unit 142 changes from high level to low level, and outputs a time-up signal when a predetermined time has elapsed (for example, the output is changed from low level to high level). To change). Basically, the timing determination unit 146 outputs a commutation restart instruction when the output of the energization direction detection unit 144 becomes high level after the output of the threshold voltage determination unit 142 changes from high level to low level. However, when the time-up signal is output from the timer 147 even if the output of the energization direction detection unit 144 does not become high level, the commutation restart instruction is output.

  For example, a fixed value is used as the predetermined time measured by the timer 147. As apparent from the voltage waveform shown in FIG. 5, after the output of the threshold voltage determination unit 142 changes from the high level to the low level, the period of C or D always comes within one period T of the phase voltage. It should be. Therefore, a value equal to or greater than one period T (for example, one period of the phase voltage corresponding to idling rotation) assuming the longest period is set as the predetermined time. Thus, by using a fixed value as the predetermined time, it is easy to determine the timing when the predetermined time has elapsed.

  In the above description, a fixed value is used as the predetermined time. However, in order to quickly release the protection operation, it is desirable that the predetermined time is as short as possible. The value of the predetermined time may be variably set.

  FIG. 14 is a diagram illustrating another modification of the load dump protection determination unit. 14 is different from the load dump protection determination unit 140A illustrated in FIG. 13 in that a timer time setting unit 148 is added. The timer time setting unit 148 variably sets the time (predetermined time) at which the timer 147 outputs the time-up signal. Specifically, the timer time setting unit 148 captures the period of the signal output from the energization direction detection unit 144 during the protection operation (for example, the period when the high level changes to the low level) and takes the time (predetermined) Time) setting. This cycle is a cycle of the phase voltage, and the rotation speed of the vehicle generator 1 is detected based on the phase voltage. The timer time setting unit 148 sets the predetermined time longer when the rotation is low (when the cycle is long), and conversely sets the predetermined time short when the rotation is high (when the cycle is short). The variable setting of the predetermined time may be continuously and smoothly changed according to the rotation speed (cycle), or may be changed discontinuously in a staircase pattern.

  The timing suitable for suppressing the occurrence of surge voltage arrives at a cycle corresponding to the rotation speed, so by setting the length of the predetermined time according to the rotation speed, it is possible to set a short time considering the rotation speed, and early The protection operation can be terminated. In particular, it is necessary to add components for detecting the number of revolutions by detecting the level of the number of revolutions based on the phase voltage, and to input / output signals to / from the power generation control device 7 that controls the excitation current. Therefore, the configuration and wiring can be simplified and downsized.

  FIG. 15 is a diagram illustrating another modification of the load dump protection determination unit. A load dump protection determination unit 140B 'of the modification shown in FIG. 15 is obtained by replacing the timer time setting unit 148 in the load dump protection determination unit 140B shown in FIG. 14 with a timer time setting unit 148'. Since the control unit 100 performs the synchronous rectification control operation based on the output data of the operation detection units 120 and 130 before entering the protection operation, the control unit 100 detects the rotational speed N necessary for the control operation. The timer time setting unit 148 ′ takes in the rotation speed N detected by the control unit 100 and sets the time (predetermined time) of the timer 147. Specifically, similar to the timer time setting unit 148 shown in FIG. 14, the predetermined time is set to be long at the time of low rotation, and conversely, the predetermined time is set to be short at the time of high rotation. In addition, the variable setting of the predetermined time may be continuously and smoothly changed according to the rotation speed, or may be changed discontinuously in a stepped manner.

  FIG. 16 is a diagram illustrating another modification of the load dump protection determination unit. The load dump protection determination unit 140C of the modification shown in FIG. 16 is different in that a timer time setting unit 149 is added to the load dump protection determination unit 140A shown in FIG. The timer time setting unit 149 variably sets the time (predetermined time) at which the timer 147 outputs the time-up signal. Specifically, the timer time setting unit 149 takes in the excitation current If (Duty value or current instruction value) immediately before the protection operation from the power generation control device 7 via the control unit 100 and the communication circuit 180, and sets the time of the timer 147 ( (Predetermined time) is set. The timer time setting unit 149 sets the predetermined time longer when the excitation current If is small, and conversely sets the predetermined time short when the excitation current If is large. The variable setting of the predetermined time may be continuously and smoothly changed according to the excitation current If, or may be changed discontinuously in a stepped manner.

  The fact that there is a lot of excitation current before entering the protection operation means that much energy is generated during load dump. Therefore, it is considered that the current flowing through the phase winding increases, and it becomes easier to detect the timing suitable for suppressing the generation of the surge voltage. On the contrary, the fact that the exciting current before entering the protection operation is small means that the energy generated during load dumping is so small that it is difficult to detect the timing suitable for suppressing the generation of the surge voltage. Considering these, by setting the length of the predetermined time according to the excitation current, it is possible to set a short time in consideration of the excitation current, and the protection operation can be terminated early.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. For example, in the above-described embodiment, the two stator windings 2 and 3 and the two rectifier module groups 5 and 6 are provided. However, the vehicle including one stator winding 2 and one rectifier module group 5 is provided. The present invention can also be applied to power generators.

  Further, in the above-described embodiment, the case where the rectifying operation (power generation operation) is performed using each rectifier module 5X or the like has been described. However, it is applied from the battery 9 by changing the on / off timing of the MOS transistors 50 and 51. The generated DC current may be converted into an AC current and supplied to the stator windings 2 and 3 to cause the vehicle generator 1 to perform an electric operation.

  In the above-described embodiment, each of the two rectifier module groups 5 and 6 includes three rectifier modules. However, the number of rectifier modules may be other than three.

  Further, in the above-described embodiment, the timing at which the source-drain voltage Vds of the MOS transistor 51 is detected and the protection operation is shifted based on the detected value, or the timing at which the protection operation is canceled and the normal rectification operation is shifted. However, the same timing determination may be performed by directly detecting the direction and value of the current flowing through the MOS transistor 51. For example, a current detection element (such as a resistor) may be inserted on the source side or drain side of the MOS transistor 51, and the same determination may be made based on the voltage across the element. In this case, the timing at which current flows into the phase winding through the MOS transistor 51 or a diode connected in parallel with the MOS transistor 51 (range indicated by D in FIG. 5) is reliably detected to shift to the protection operation or to perform the protection operation. Release can be made. Thereby, interruption | blocking and sudden change of the electric current which flows into a phase winding can be prevented, and it can suppress that a high surge voltage generate | occur | produces in a phase winding.

  In the embodiment described above, MOS transistors are used for both the upper arm and the lower arm. However, only the lower arm may be a MOS transistor, and the upper arm may be formed of a diode.

  Further, in the above-described embodiment, for each rectifier module corresponding to each phase winding, the load dump protection determination unit 140 shown in FIG. 6 and the configuration for on / off control of the MOS transistors 50 and 51 at the time of synchronous rectification are provided. However, in the configuration other than the configuration necessary for the protection operation at the time of load dumping (configuration necessary for synchronous rectification), it is not provided for each rectifier module, but one unit or a group of rectifier modules 5 and 6 as a whole. One may be provided for each.

  In addition, in the modified example of the load dump protection determination unit shown in FIGS. 13 to 16, the timer 147 and the like are added to the configuration shown in FIG. 6, but the timer 147 and the like are added to the configuration shown in FIG. You may make it do.

  In the above-described embodiment, the load dump protection determination unit 140 and the like include the Vgs setting unit 190 and the like. However, the Vgs setting unit 190 and the like may be provided in the control unit 100, the load dump protection determination unit 140 and the like. It may be provided separately from the circuit 100.

  As described above, according to the present invention, when the MOS transistor 51 of the lower arm is turned on at the time of load dump, a protective operation for preventing the generation of a high voltage at the time of load dump is performed. The operation to cancel the protection operation after the suppression of the voltage is stopped after the arrival of the timing suitable for suppressing the generation of the surge voltage, so that the normal rectification operation can be resumed avoiding the timing at which the surge voltage occurs. It is possible to quickly end the generation of high voltage during load dump. Further, since the ON state of the MOS transistor 51 of the lower arm is maintained until the output voltage of the series circuit composed of the upper arm and the lower arm is lowered, the switching element does not repeat ON / OFF frequently, and the ON / OFF state is not repeated. There is no generation of a high voltage due to repeated off, and energy generated in the phase winding can be quickly extinguished, and generation of a high voltage at the time of load dump can be terminated quickly. Further, since the ON resistance of the MOS transistor 51 is variably set according to the magnitude of the current flowing through the MOS transistor 51, the timing suitable for suppressing the occurrence of surge voltage is determined by the voltage across the MOS transistor 51 (source / drain). When performing based on the inter-voltage Vds), it is possible to obtain an appropriate voltage between both ends regardless of the magnitude of the current, and to reliably determine a timing suitable for suppressing the occurrence of the surge voltage.

DESCRIPTION OF SYMBOLS 1 Vehicle generator 2, 3 Stator winding 4 Field winding 5, 6 Rectifier module group 5X, 5Y, 5Z, 6U, 6V, 6W Rectifier module 7 Power generation control apparatus 8 ECU
DESCRIPTION OF SYMBOLS 9 Battery 10 Electric load 12 Charging line 50, 51 MOS transistor 54 Control circuit 100 Control part 140 Load dump protection determination part 141 B voltage detection part 142 Threshold voltage determination part 143 MOS voltage detection part 144 Current direction detection part 145,146 Timing determination unit 147 Timer 148, 148 ′ 149 Timer time setting unit 170, 172 Driver 190, 190A Vgs setting unit

Claims (20)

An armature winding having two or more phase windings;
A switching circuit having a bridge circuit including a plurality of lower arms configured by switching elements having diodes connected in parallel, and rectifying an induced voltage of the armature winding;
A control unit that instructs on / off of the switching element;
The output voltage of the switching unit is monitored, and when the output voltage exceeds a first threshold voltage, an instruction to turn on the switching element constituting the lower arm is given to the control unit, Suitable for suppressing generation of surge voltage when the output voltage becomes lower than the second threshold voltage lower than the first threshold voltage after exceeding the first threshold voltage Waiting for the timing to arrive, a load dump protection determination unit that instructs the control unit to turn off the switching element constituting the lower arm;
An on-resistance setting unit configured to set an on-resistance of the switching element according to a magnitude of a current flowing through the switching element when the switching element is turned on exceeding the first threshold voltage;
The load dump protection determination unit determines whether it is a timing suitable for suppressing the occurrence of a surge voltage based on the voltage across the switching element for which the on-resistance is set by the on-resistance setting unit. A vehicular generator. In claim 1,
The on-resistance setting unit sets the on-resistance small when the current flowing through the switching element is large, and sets the on-resistance large when the current flowing through the switching element is small. In claim 1 or 2,
The on-resistance setting unit detects a magnitude of a current flowing through the switching element by observing a voltage between both ends of the switching element. In claim 1 or 2,
The on-resistance setting unit includes a magnitude of an excitation current flowing in a field winding that magnetizes a field pole of a rotor immediately before the switching element is turned on exceeding the first threshold voltage, and a high or low rotation speed. Based on the above, the magnitude of the current flowing through the switching element is estimated. In any one of Claims 1-4,
The load dump protection determination unit configures the lower arm after detecting that the output voltage has exceeded the first threshold voltage and waiting for a timing suitable for suppressing the occurrence of a surge voltage. A vehicular generator, wherein the controller is instructed to turn on the switching element. In any one of Claims 1-5,
The timing for suppressing the generation of the surge voltage is a timing other than the timing at which current flows from the phase winding connected to the switching element to the switching element when the switching element constituting the lower arm is turned on. A vehicular generator characterized by that. In claim 6,
The timing for suppressing the generation of the surge voltage is the timing at which current flows from the switching element to the phase winding connected to the switching element when the switching element constituting the lower arm is turned on. A vehicular generator. In claim 6 or 7,
The switching element is a MOS transistor;
The load dump protection determination unit is configured to detect a MOS voltage detector that detects a source-drain voltage of the MOS transistor, and to turn on the MOS transistor when the MOS transistor is turned on based on the detected source-drain voltage. A vehicle comprising: an energization direction detection unit that detects a direction of a current flowing through the vehicle; and a timing determination unit that determines a timing for suppressing the generation of the surge voltage based on a detection result by the energization direction detection unit. Generator. In claim 8,
The on-resistance setting unit changes a channel resistance of a source / drain voltage by variably setting a voltage of a drive signal inputted to a gate of the MOS transistor. In claim 8,
The vehicular generator is characterized in that the timing of suppressing the generation of the surge voltage is a timing at which the source-drain voltage of the MOS transistor with respect to the source side becomes 0 V or less. In claim 9,
The vehicular generator is characterized in that the timing of suppressing the generation of the surge voltage is a timing delayed by a predetermined period after the source-drain voltage of the MOS transistor with respect to the source side becomes 0 V or less. In claim 11,
The vehicle generator according to claim 1, wherein the predetermined period is a period corresponding to a quarter of a period of the induced voltage of the phase winding. In any one of Claims 1-5,
The timing for suppressing the generation of the surge voltage is such that the direction of the current flowing through the switching element after the output voltage exceeds the first threshold voltage and the switching element constituting the lower arm is turned on. A vehicle generator characterized by having a timing synchronized with a cycle of a timing that changes from a direction flowing from the phase winding to the switching element to a direction flowing from the switching element to the phase winding. In any one of Claims 1-4,
The load dump protection determination unit instructs the control unit to forcibly turn off the switching element constituting the lower arm when the arrival of a timing suitable for suppressing the occurrence of surge voltage cannot be detected. A vehicular generator characterized by In claim 14,
The timing for forcibly giving the instruction is after the output voltage becomes lower than a second threshold voltage lower than the first threshold voltage after exceeding the first threshold voltage. A vehicular generator characterized in that a predetermined time has elapsed. In claim 15,
The vehicle generator according to claim 1, wherein the predetermined time is a variable value. In claim 15,
The vehicle generator according to claim 1, wherein the predetermined time is a fixed value. In claim 16,
The vehicle generator is characterized in that the predetermined time is set to a long value at a low rotation and a short value at a high rotation. In claim 18,
The load dump protection determination unit detects the level of rotation speed based on the voltage of the phase winding. In claim 16,
The field winding for magnetizing the field pole of the rotor before the output voltage exceeds a first threshold voltage and an instruction to turn on the switching element constituting the lower arm is issued for the predetermined time. The vehicle generator is characterized in that it is set to a short value when the exciting current flowing through the coil is large and to a long value when the exciting current is small.

Images