JP2016163467A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device which can suppress a rush current at the time of power on without adding a new configuration.SOLUTION: A second shutdown mechanism 62 includes: a second FET 66 which, when switched ON, electrically connects a power unit 40 to a battery 80; and a voltage division circuit which applies a divided voltage to the gate of the second FET 66. The constant of a resistor 66R2 which constitutes the voltage division circuit is set in such a manner that the divided voltage obtained by the voltage division circuit has voltage magnitude sufficient to operate the second FET 66 in a saturation region.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a motor control device.

  A brushless DC motor (hereinafter abbreviated as “motor”) used for a blower motor or the like of a vehicle air conditioner includes an inverter circuit using a phase voltage corresponding to the position of the rotor and a FET (field effect transistor) as a switching element. The power unit generates the voltage, and the generated voltage is applied to the motor coil.

  Since the power unit is directly connected to the in-vehicle battery that is the power source, in case of reverse connection where the positive and negative are connected in reverse with the in-vehicle battery or when the power system circuit is short-circuited, the power unit is connected between the power source and the power unit. There is a case where a second shutdown mechanism for cutting off the electrical connection is provided. The second shutdown mechanism is a type of switch using a relay or FET as a switching element, and in response to a command signal from a control unit that is a control device configured with a microcomputer or the like, an electrical power supply and a power unit are electrically connected. Turn the connection on or off.

  Since the second shutdown mechanism is a kind of switch, an inrush current may flow to the power unit when the power source and the power unit are electrically connected. Such an inrush current can damage the elements constituting the circuit related to the motor control device, and can be a cause of generation of electromagnetic waves that adversely affect electronic devices. In particular, when a relay is used as the switching element of the second shutdown mechanism, the relay may be damaged by the inrush current. Therefore, the second shutdown mechanism may be provided with a precharge mechanism for reducing the influence of the inrush current. .

  FIG. 8 is a schematic diagram illustrating an example of a second shutdown mechanism and a precharge mechanism. The second shutdown mechanism 262 is provided between the power unit 40 that drives the motor 52 and the battery 80, and turns on or off the power supplied from the battery 80 to the power unit 40. The precharge mechanism 264 is provided between the battery 80 and the power unit 40 so as to be in parallel with the second shutdown mechanism 262.

  The precharge mechanism 264 shown in FIG. 8 is configured by a resistor, and supplies a minute current to the power unit 40 before the second shutdown mechanism 262 turns on the power supplied from the battery 80 to the power unit 40.

  The electrolytic capacitor 40 </ b> C is charged in the power unit 40 by the minute current supplied through the precharge mechanism 264. By reducing the potential difference between the electrolytic capacitor 40C and the B terminal which is the positive electrode of the battery 80 by such charging, the influence of the inrush current when the second shutdown mechanism 262 is turned on is reduced.

  Patent Document 1 discloses an invention of an electric power steering apparatus including an inrush prevention circuit that suppresses the influence of an inrush current by supplying a minute current to a capacitor of a drive circuit as described above.

JP 2014-172491 A

  However, the electric power steering apparatus described in Patent Document 1 has a problem that the manufacturing cost of the entire motor control apparatus increases due to the addition of the inrush prevention circuit including the precharge mechanism.

  The present invention has been made in view of the above, and an object of the present invention is to provide a motor control device that can suppress an inrush current at the time of power-on without adding a new configuration.

In order to solve the above-mentioned problem, the motor control device according to claim 1 is a drive circuit that generates a voltage to be applied to a terminal of a motor coil, and an electric field that electrically connects the drive circuit and the battery when turned on. An effect transistor and a voltage dividing circuit for applying a divided voltage to a gate of the field effect transistor, and the voltage dividing circuit so that the voltage becomes a voltage large enough to operate the field effect transistor in a saturation region. A switch mechanism that determines the constants of the elements constituting
And a control unit that outputs a control signal for turning on the field effect transistor and that controls the drive circuit based on a command signal from a host control device.

  According to this motor control device, the voltage applied to the gate of the field effect transistor that is a switching element is set to a voltage at which the field effect transistor operates in the saturation region. Since the saturation region is a region having a large on-resistance, it is possible to prevent a sudden energization from the battery to the drive circuit, and as a result, the occurrence of an inrush current is suppressed.

  A voltage dividing circuit is connected to the gate of the field effect transistor, and the field effect transistor is turned on by a voltage applied from the voltage dividing circuit. By determining the constants of the elements constituting the voltage dividing circuit so that the voltage applied to the gate of the field effect transistor by the voltage dividing circuit becomes a voltage large enough to operate the field effect transistor in the saturation region. Inrush current at power-on can be suppressed without adding a new configuration.

  The motor control device according to claim 2 is the motor control device according to claim 1, wherein the field effect transistor is P-type, and the voltage dividing circuit is a voltage of the battery applied to a source of the field effect transistor. Is applied to the gate of the field effect transistor, the first resistor connecting the source and the gate, the second resistor having one end connected to the gate, and the collector being the second resistor. And the control transistor to which the control signal is input to the base, and when the control transistor is turned on by the input of the control signal, the voltage dividing circuit So that the voltage applied to the gate of the field effect transistor is a voltage large enough to operate the field effect transistor in the saturation region. It defines the resistance value of the serial second resistor.

  According to this motor control device, the resistance value of the second resistor is determined so that the voltage applied to the gate of the field effect transistor by the voltage dividing circuit becomes a voltage that causes the field effect transistor to operate in the saturation region. Thus, an inrush current at power-on can be suppressed without adding a new configuration.

  According to a third aspect of the present invention, in the motor control device according to the second aspect, when the control unit outputs a control signal and a predetermined time or more has elapsed, the collector and emitter of the control transistor By changing the control signal so that the current between them increases, the voltage applied to the gate of the field effect transistor by the voltage dividing circuit becomes a voltage large enough to operate the field effect transistor in a linear region. Like that.

  According to this motor control device, by changing the control signal input to the base of the control transistor and increasing the current between the collector and emitter of the control transistor, the second resistor and the control transistor of the voltage dividing circuit The resistance value of the composed combined resistor is reduced. As a result, the voltage applied by the voltage dividing circuit to the gate of the second switching element is reduced to such an extent that the field effect transistor operating in the saturation region can be operated in the linear region. By operating the field effect transistor, which is a switching element, in a linear region with low on-resistance, battery power can be supplied to the drive circuit.

  The motor control device according to claim 4 is the motor control device according to claim 1, wherein the field effect transistor is an N-type, and the voltage dividing circuit is a circuit that divides the control signal to a gate of the field effect transistor. A first resistor having one end connected to the control unit and the other end connected to the gate, a capacitor having one end connected to the gate, and an element connected to the other end of the capacitor. A voltage applied to the gate of the field effect transistor by the voltage dividing circuit when the control signal is input, the voltage applied to the field effect transistor in the saturation region The resistance value of the first resistor is determined so that the voltage is large enough to operate.

  According to this motor control device, the resistance value of the first resistor is determined so that the voltage applied to the gate of the field effect transistor by the voltage dividing circuit is a voltage large enough to operate the field effect transistor in the saturation region. Thus, an inrush current at power-on can be suppressed without adding a new configuration.

  According to a fifth aspect of the present invention, in the motor control device according to the fourth aspect, the capacitance of the capacitor is set so that a time from when the control signal is input until the capacitor is charged is equal to or longer than a predetermined time. ing.

  According to this motor control device, the voltage dividing circuit divides the voltage of the control signal into a voltage at which the field effect transistor operates in the saturation region until the capacitor constituting the voltage dividing circuit is charged. The time from when the control signal is input until the capacitor is charged is the predetermined time from when the control signal is input until the potential difference between the element at the subsequent stage of the switch mechanism and the battery positive electrode can be eliminated. By determining as described above, the field effect transistor can be operated in the saturation region until the potential difference between the subsequent element and the battery positive electrode can be eliminated.

It is the schematic which showed the structure of the motor unit using the motor control apparatus which concerns on the 1st Embodiment of this invention. It is the figure which showed the outline of the motor control apparatus which concerns on the 1st Embodiment of this invention. It is the schematic which showed an example of the 2nd shutdown mechanism which concerns on the 1st Embodiment of this invention. It is the figure which showed the outline of the operation | movement order of the 2nd shutdown mechanism which concerns on the 1st Embodiment of this invention. It is the graph which showed an example of the aspect of ON resistance of FET with respect to the gate source voltage which is a potential difference of the gate of a FET, and a source. It is the schematic which showed an example of the 2nd shutdown mechanism which concerns on the 2nd Embodiment of this invention. It is the figure which showed the outline of the operation | movement order of the 2nd shutdown mechanism which concerns on the 2nd Embodiment of this invention. It is the schematic which showed an example of the second shutdown mechanism and the precharge mechanism.

[First Embodiment]
FIG. 1 is a schematic diagram showing a configuration of a motor unit 10 using a motor control device 20 according to a first embodiment of the present invention. The motor unit 10 according to the present embodiment in FIG. 1 is a so-called blower motor unit used for blowing air from a vehicle air conditioner as an example.

  The motor unit 10 according to the present embodiment relates to a three-phase motor having an outer rotor structure in which a rotor 12 is provided outside a stator 14. The stator 14 is an electromagnet in which a lead wire is wound around a core member, and constitutes three phases of a U phase, a V phase, and a W phase. Each of the U-phase, V-phase, and W-phase of the stator 14 generates a so-called rotating magnetic field by switching the polarity of the magnetic field generated by the electromagnet under the control of the motor control device 20 described later.

  A rotor magnet is provided inside the rotor 12 (not shown), and the rotor magnet rotates the rotor 12 by responding to the rotating magnetic field generated by the stator 14. The rotor 12 is provided with a shaft 16 and rotates integrally with the rotor 12. Although not shown in FIG. 1, in the present embodiment, the shaft 16 is provided with a multi-blade fan such as a so-called sirocco fan, and the multi-blade fan rotates together with the shaft 16, thereby blowing air in the vehicle air conditioner. It becomes possible.

  The stator 14 is attached to the motor control device 20 via the upper case 18. The motor control device 20 includes a substrate 22 of the motor control device 20 and a heat sink 24 that dissipates heat generated from elements on the substrate 22. A lower case 60 is attached to the motor unit 10 including the rotor 12, the stator 14, and the motor control device 20.

  FIG. 2 is a diagram showing an outline of the motor control device 20 according to the present embodiment. The motor control device 20 shown in FIG. 2 includes a power unit 40 including an inverter circuit 44 that generates a voltage to be applied to each terminal of the U-phase coil 14U, the V-phase coil 14V, and the W-phase coil 14W of the stator 14 of the motor 52. And a control unit 32 for controlling the power unit 40.

  The inverter circuit 44 of the power unit 40 includes FETs 44A to 44F that are switching elements. The power unit 40 turns the FETs 44 </ b> A to 44 </ b> F on and off based on the command duty ratio output from the control unit 32, thereby converting DC power supplied from the battery 80 into AC power and supplying the AC power to the motor 52. For example, the FETs 44A and 44D switch power supplied to the U-phase coil 14U, the FETs 44B and 44E switch to the V-phase coil 14V, and the FETs 44C and 44F switch to the W-phase coil 14W.

  The drains of the FETs 44A, 44B, and 44C are connected to the positive electrode of the vehicle-mounted battery 80 via the second shutdown mechanism 62 and the noise removal coil 46. The sources of the FETs 44D, 44E, and 44F are connected to the negative electrode of the battery 80 via the reverse connection prevention FET.

  In the present embodiment, a reverse connection prevention FET 48 and a noise prevention coil 46 are provided between a battery 80 as a power source and the power unit 40. The reverse connection prevention FET 48 is a circuit for protecting elements constituting the motor control device 20 when the positive electrode and the negative electrode of the battery 80 are connected in reverse to the case shown in FIG. As an example, the reverse connection prevention FET 48 includes a so-called diode-connected FET in which its source and gate are connected. The coil 46 is an element for suppressing noise generated by switching of the power unit 40.

  The power unit 40 of the motor control device 20 according to the present embodiment is provided with an electrolytic capacitor 40 </ b> C connected to the battery 80 in parallel with the inverter circuit 44. The electrolytic capacitor 40 </ b> C is used to smooth the voltage of power supplied from the battery 80. Further, the electrolytic capacitor 40C is charged before the second shutdown mechanism 62 is completely turned on in order to suppress the influence of the inrush current when the second shutdown mechanism 62 is turned on, and the potential difference from the positive electrode of the battery 80 is increased. It is also used to relax.

  In the present embodiment, the Hall element 12 </ b> B detects the magnetic field of the rotor magnet 12 </ b> A or the sensor magnet provided coaxially with the shaft 16 as a magnetic field indicating the rotational position of the rotor 12. The control unit 32 detects the rotational speed and position (rotational position) of the rotor 12 based on the magnetic field detected by the Hall element 12B, and controls the switching of the inverter circuit 44 according to the rotational speed and rotational position of the rotor 12. Do.

  The control unit 32 is a control circuit including a microcomputer, and receives a command signal including a speed command value related to the rotational speed of the rotor 12 from an air conditioner ECU 82 that controls the air conditioner in response to an air conditioner switch operation. Further, a voltage dividing circuit 54 constituted by a thermistor 54 </ b> A and a resistor 54 </ b> B, and a current detection unit 56 provided between the inverter circuit 44 and the negative electrode of the battery 80 are connected to the control unit 32.

  Since the resistance value of the thermistor 54 </ b> A constituting the voltage dividing circuit 54 changes according to the temperature of the circuit board 22, the voltage of the signal output from the voltage dividing circuit 54 changes according to the temperature of the circuit board 22. The control unit 32 calculates the temperature of the substrate 22 based on the change in the voltage of the signal output from the voltage dividing circuit 54.

  The current detector 56 has a shunt resistor 56A having a resistance value of about 0.2 mΩ to several Ω and an amplifier 56B that amplifies the potential difference between both ends of the shunt resistor 56A and outputs a voltage value proportional to the current of the shunt resistor 56A as a signal. The signal output from the amplifier 56B is input to the control unit 32. The control unit 32 calculates the current of the inverter circuit 44 based on the signal output from the amplifier 56B.

  In the present embodiment, the signal from the voltage dividing circuit 54 including the thermistor 54A, the signal output from the current detection unit 56, and the signal output from the Hall element 12B are input to the control unit 32. The control unit 32 calculates the temperature of the elements of the substrate 22, the current of the inverter circuit 44, the rotational speed of the rotor 12, and the like based on the input signals. Further, a voltage sensor 58 for measuring the voltage of the battery 80 is connected to the control unit 32.

  For example, when the voltage value of the battery 80 detected by the voltage sensor 58 or the current value detected by the current detection unit 56 is outside a predetermined range, the control unit 32 regards the battery 80 as being reversely connected or a circuit short-circuit, The second shutdown mechanism 62 is turned off to stop energization of the power unit 40.

  FIG. 3 is a schematic diagram illustrating an example of the second shutdown mechanism 62 according to the present embodiment. The second shutdown mechanism 62 shown in FIG. 3 includes a first FET 64 and a second FET 66 that are both P-type FETs, and further includes a control transistor 68.

  The first FET 64 has a drain connected to the positive electrode of the battery 80 and a gate grounded via a resistor 64R. The source of the first FET 64 is connected to the gate via the capacitor 64C. Further, a Zener diode 64D for circuit protection is connected in parallel with the capacitor 64C between the gate and source of the first FET 64.

  The source of the second FET 66 is connected to the source of the first FET 64. The source of the second FET 66 is connected to the gate through the resistor 66R1. Further, a Zener diode 66D for circuit protection is connected in parallel with the resistor 66R1 between the gate and source of the second FET 66.

  The drain of the second FET 66 is connected to the power unit 40, and the gate of the second FET 66 is connected to the collector of the control transistor 68 via the resistor 66R2.

  The emitter of the control transistor 68 is grounded, and the control unit 32 is connected to the base of the control transistor 68. The control transistor 68 is turned on when a control signal is input from the control unit 32.

  The control unit 32 is operated by electric power supplied via an element such as a diode 32D. When a command signal for turning on the vehicle air conditioner is input from the air conditioner ECU 82, the control unit 32 outputs the above-described control signal and performs a second shutdown. Turn mechanism 62 on. In addition, the control unit 32 controls the power unit 40 based on a command signal from the air conditioner ECU 82.

  FIG. 4 is a diagram showing an outline of the operation sequence of the second shutdown mechanism 62 according to the present embodiment. In the second shutdown mechanism 62 shown in FIG. 4, when the ignition switch is turned on, the power of the battery 80 is supplied to the drain of the first FET 64 as shown in (1) of FIG.

  When the energization shown in (1) of FIG. 4 is performed, the power of the battery 80 reaches the source side of the first FET 64 via the parasitic diode 64P of the first FET 64 as shown in (2) of FIG. A potential difference is generated between the source and the gate, and as a result, the first FET 64 is turned on. A part of the current shown in (2) of FIG. 4 reaches the gate of the first FET 64 via the capacitor 64C, but the capacitor 64C and the resistor 64R constitute a kind of voltage dividing circuit.

In the voltage dividing circuit, the relationship of the following formula (1) is established.

The voltage applied to the capacitor 64C from the source of the first FET 64 is V _in , the voltage applied to the gate of the first FET 64 is V _out , the resistance value of the capacitor 64C is R ₁ , and the resistance value of the resistor 64R is R ₂ . According to the above formula (1), the voltage _{V out} applied to the gate of the second 1FET64 is lower than the voltage _{V in} of the 1FET64 sources.

  Therefore, a potential difference is generated between the gate and the source of the first FET 64, and the first FET 64 is turned on. Further, when the capacitor 64C is fully charged, no current flows from the source of the first FET 64 via the capacitor 64C, so that the potential difference between the gate and the source of the first FET 64 increases, and the first FET 64 remains on. .

  Since the first FET 64 is turned on, the power of the battery 80 reaches the source of the second FET 66 as shown in (3) of FIG. As shown in (4) of FIG. 4, when the control signal is output from the control unit 32 and the control transistor 68 is turned on, a part of the power supplied to the source of the second FET 66 is changed to (5B) of FIG. As shown in FIG. 4, the current flows to the ground region through the resistor 66R1, the resistor 66R2, and the control transistor 68, and a part is supplied to the gate of the second FET 66 as shown in (5A) of FIG.

  In FIG. 4, the resistor 66R2 and the control transistor 68 also function as a combined resistor, and the resistor 66R1, and the combined resistor of the resistor 66R2 and the control transistor 68 constitute a kind of voltage dividing circuit. The voltage applied to the source of the second FET 66 is divided as shown in (5A) and (5B) of FIG. 4 according to the resistance values of the resistor 66R1, and the combined resistance of the resistor 66R2 and the control transistor 68. Is done.

In the above equation (1), the voltage applied to the resistor 66R1 from the source of the second FET 66 is V _in , the voltage applied to the gate of the second FET 66 is V _out , the resistance value of the resistor 66R1 is R ₁ , the resistor 66R2, and the control transistor the resistance value of the combined resistance of 68 to _{R 2.} According to the above equation (1), the voltage V _out applied to the gate of the second FET 66 is lower than the voltage V _in of the source of the second FET 66.

  As a result, a potential difference is generated between the source and gate of the second FET 66, so that the second FET 66 is turned on as shown in FIG. 4 (6), and the power of the battery 80 is supplied to the power unit 40.

  The order of operation of the second shutdown mechanism 62 is as described above, but if the first FET 64 and the second FET 66 are suddenly turned on, an inrush current may occur. In the second shutdown mechanism 62 shown in FIG. 4, each switching element is gradually turned on using the operational characteristics of the FET to suppress the occurrence of inrush current. Further, in the second shutdown mechanism 62 shown in FIG. 4, each switching element is gradually turned on to charge the electrolytic capacitor 40C, and each switching element is discharged at the timing when the potential difference between the positive electrode of the battery 80 and the electrolytic capacitor 40C is eliminated. To be fully on.

FIG. 5 is a graph showing an example of an aspect of the on-resistance of the FET with respect to the gate-source voltage that is a potential difference between the gate and the source of the FET. In FIG. 5, the cut-off region 70 is a region in a state where the gate-source voltage is less than the threshold voltage and the FET is turned off. When the gate-source voltage is V _gs and the threshold voltage is V _t , the relationship V _gs <V _t is established.

In the saturation region 72, when the voltage between the drain and the source is V _ds , the relationship V _ds > V _gs −V _t is established. The saturation region 72 is a region in a transitional state where the FET transitions from OFF to ON, and the resistance value of the FET ON resistance changes according to the change of the gate-source voltage. In FIG. 5, as the gate source voltage increases, the value of the FET on resistance decreases.

In the linear region 74, the value of the FET on-resistance does not change greatly even when the gate-source voltage changes in a state where the FET is completely turned on. The relationship V _ds <V _gs −V _t is established.

  In the present embodiment, the first FET 64 and the second FET 66 are operated in the saturation region 72 by making the constants of the capacitor 64C, the resistor 64R, and the resistor 66R2 larger than the normal circuit in which the first FET 64 and the second FET 66 are quickly turned on. To start.

  By making the constant of the capacitor 64C, that is, the capacitance larger than that of a normal circuit, a current can flow from the source of the first FET 64 to the gate of the first FET for a longer time. Further, by increasing the constant of the resistor 64R, that is, the resistance value, the voltage applied to the gate of the first FET 64 by the voltage dividing circuit constituted by the capacitor 64C and the resistor 64R is increased, and the gate and source of the first FET 64 are increased. The potential difference can be suppressed.

In the above formula (1), the voltage applied from the source of the first FET 64 to the capacitor 64C is V _in , the voltage applied to the gate of the first FET 64 is V _out , the resistance value of the capacitor 64C is R ₁ , and the resistance value of the resistor 64R the When _{R 2,} by increasing the resistance value _{R 2} of the resistor 64R, the voltage _{V out} applied to the gate of the 1FET64 has a higher voltage.

  As a result, the first FET 64 can be operated in the saturation region 72 until the capacitor 64C having an increased capacity is fully charged, and the inrush current generated when the first FET 64 is turned on can be reduced. After the capacitor 64C is charged, the potential difference between the gate and the source of the first FET 64 increases as described above, and the first FET 64 remains on in the linear region 74.

  When a control signal is output from the control unit 32, the control transistor 68 is turned on and the second FET 66 is turned on. By increasing the constant of the resistor 66R2, that is, the resistance value, the voltage applied to the gate of the second FET 66 by the voltage dividing circuit composed of the resistor 66R1 and the combined resistance of the resistor 66R2 and the control transistor 68 is increased. The potential difference between the gate and source of the second FET 66 can be suppressed.

In the above equation (1), the voltage applied to the resistor 66R1 from the source of the second FET 66 is V _in , the voltage applied to the gate of the second FET 66 is V _out , the resistance value of the resistor 66R1 is R ₁ , the resistor 66R2, and the control transistor When the resistance value of the combined resistance of 68 to _{R 2,} by increasing the resistance of the resistor 66R2, the resistance value _{R 2} is increased, the voltage _{V out} applied to the gate of the 2FET66 has a higher voltage.

  As a result, the operation of the second FET 66 can be started in the saturation region 72, and the inrush current generated when the second FET 66 is turned on can be reduced. Furthermore, by operating the second FET 66 in the saturation region 72, a minute current is supplied to the electrolytic capacitor 40C, and the potential difference between the electrolytic capacitor 40C and the positive electrode of the battery 80 is relaxed. The influence can be suppressed.

  The second FET 66 starts to operate in the saturation region 72. However, the operation of the second FET 66 can be switched from the saturation region 72 to the linear region 74 by changing the current flowing between the collector and the emitter of the control transistor 68. it can.

  Since the control transistor 68 is an NPN-type bipolar transistor, the current value between the collector and emitter changes in accordance with the current value of the control signal input to the base. For example, if the current value of the control signal input to the base of the control transistor 68 is increased when the second FET 66 is operating in the saturation region 72, more current flows between the collector and emitter of the control transistor 68, As a result, the resistance between the collector and emitter of the control transistor 68 is reduced. In order to increase the current of the control signal input to the base of the control transistor 68, for example, a known amplifier circuit (not shown) using an element such as a bipolar transistor is used.

  Since the voltage dividing circuit that outputs the voltage applied to the gate of the second FET 66 includes the resistor 66R1, and the combined resistance of the resistor 66R2 and the control transistor 68, the resistance between the collector and the emitter of the control transistor 68 is reduced. For example, the combined resistance of the resistor 66R2 and the control transistor 68 is also reduced. As a result, the voltage applied to the gate of the second FET 66 decreases, and the potential difference between the gate and source of the second FET 66 increases.

  If the potential difference between the gate and source of the second FET 66 increases to such an extent that the second FET 66 can operate in the linear region 74, the second FET 66 is completely turned on, and the power of the battery 80 is supplied to the power unit 40. become able to. The timing for amplifying the control signal is after the elapse of a predetermined time from the output of the control signal. During the predetermined time, the electrolytic capacitor 40C is charged by the minute current supplied through the second FET 66 operating in the saturation region 72 from the time when the control signal is output, and the potential difference between the electrolytic capacitor 40C and the positive electrode of the battery 80 can be eliminated. It is time until.

  The electrolytic capacitor 40C, the resistor 64R, the resistor 66R1, the resistor 66R2, the constants of the control transistor 68, the current value of the control signal input to the base of the control transistor 68, and the predetermined time are concretely determined through experiments and experiments using actual machines. To decide. If the specifications of the resistor 66R1 and the control transistor 68 are defined, the second FET 66 can be started to operate in the saturation region 72 by optimizing the constant of the resistor 66R2.

  In the present embodiment, the first FET 64 and the second FET 66 are provided to take measures against energization by the parasitic diode 64P of the first FET 64 and to ensure circuit redundancy. However, if the countermeasure of the parasitic diode 64P and the guarantee of circuit redundancy are not required, the second shutdown mechanism 62 is configured by including the second FET 66, the resistor 66R1, the resistor 66R2, the control transistor 68, and the Zener diode 66D. Also good.

  As described above, according to the present embodiment, after the first FET 64 and the second FET 66 are started to operate in the saturation region 72 by setting the constants of the capacitor 64C, the resistor 64R, the resistor 66R1, and the resistor 66R2, It is possible to operate in the linear region 74. As a result, the generation of inrush current due to the operation of the first FET 64 and the second FET 66 can be suppressed, and the electrolytic capacitor 40C can be charged in advance before the first FET 64 and the second FET 66 operate in the linear region 74. The influence of current can be reduced.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. Although this embodiment is different from the first embodiment in that an N-type FET is used as a switching element, other configurations are the same as those in the first embodiment shown in FIGS. Therefore, detailed description of their configuration is omitted.

  FIG. 6 is a schematic diagram illustrating an example of the second shutdown mechanism 162 according to the present embodiment. The second shutdown mechanism 162 shown in FIG. 6 includes a first FET 164 and a second FET 166 that are both N-type FETs.

  The first FET 164 has a source connected to the positive electrode of the battery 80 and a gate connected to the control unit 32 via a resistor 164R and a Zener diode 168. The source of the first FET 164 is connected to the gate via the capacitor 164C. Further, a Zener diode 164D for circuit protection is connected in parallel with the capacitor 164C between the gate and source of the first FET 64.

  The drain of the second FET 66 is connected to the drain of the first FET 64. The source of the second FET 66 is connected to the gate via the capacitor 166C. Further, a Zener diode 166D for circuit protection is connected in parallel with the capacitor 166C between the gate and source of the second FET 166.

  The source of the second FET 166 is connected to the power unit 40, and the gate of the second FET 166 is connected to the control unit 32 via the resistor 166R.

  FIG. 7 is a diagram showing an outline of an operation sequence of the second shutdown mechanism 162 according to the present embodiment. In the second shutdown mechanism 162 shown in FIG. 7, when the ignition switch is turned on, the power of the battery 80 is energized to the source of the first FET 164 as shown in (1) of FIG.

  When the energization shown in (1) of FIG. 7 is performed, the power of the battery 80 reaches the drain side of the first FET 164 via the parasitic diode 164P of the first FET 164 as shown in (2) of FIG. As shown in (3) of FIG. 7, the drain of the second FET 166 is reached.

  As shown in (4) of FIG. 7, when a control signal is output from the control unit 32 and applied to the gates of the first FET 164 and the second FET 166, the first FET 164 and the second FET 166 are turned on, and the power unit 40 is turned on. The power of the battery 80 is supplied.

  Since the control signal requires a voltage sufficient to turn on the first FET 164 and the second FET 166, the control signal may be boosted using a circuit such as a charge pump as necessary.

  Also in this embodiment, at the start of operation, the first FET 164 and the second FET 166 are operated in the saturation region 72 to suppress the occurrence of inrush current. In the present embodiment, the constants of the capacitor 164C, the resistor 164R, the capacitor 166C, and the resistor 166R are made larger than the normal circuit in which the first FET 164 and the second FET 166 are quickly turned on, so that the first FET 164 and the second FET 166 are saturated. The operation is started at 72.

  When the second shutdown mechanism 162 shown in FIGS. 6 and 7 is supplied with power from the battery 80 as shown in (1) of FIG. 7, the power is supplied to the gate of the first FET 164 via the Zener diode 164D. Also supplied. In such a stage, there is no potential difference between the gate and source of the first FET 164 so that the first FET 164 is turned on.

  The first FET 164 and the second FET 166 are turned on when a control signal output from the control unit 32 is input to each gate. The control signal is input to the gate of the first FET 164 via the resistor 164R and to the gate of the second FET 166 via the resistor 166R. The combined resistance composed of the resistor 164R, the capacitor 164C, the first FET 164, the second FET 166, and the electrolytic capacitor 40C of the power unit 40 constitutes a kind of divided circuit. The resistor 166R and the combined resistor composed of the capacitor 166C and the electrolytic capacitor 40C constitute a kind of divided circuit. Therefore, when a control signal is output from the control unit 32, the voltage divided by the voltage dividing circuit is applied to the gate of each of the first FET 164 and the second FET 166.

In the above equation (1), the voltage applied to the resistor 164R as the control signal is V _in , the voltage applied to the gate of the first FET 164 is V _out , the resistance value of the resistor 164R is R ₁ , and the resistance of the circuit below the capacitor 164C When the value is R ₂ , the voltage V _out applied to the gate of the first FET 164 decreases as R ₁ increases.

Accordingly, the resistance value is a constant of _{R 1} That resistor 164R, is made larger than the normal circuit, reduce the voltage applied to the 1FET164 gate, a first 1FET164 be operated in the saturation region 72 It becomes possible.

  Similarly, by making the resistance value, which is a constant of the resistor 166R, larger than that of a normal circuit, the voltage applied to the gate of the second FET 166 can be reduced, and the second FET 166 can be operated in the saturation region 72. Become.

  In the above-described voltage dividing circuit, when the capacitor 164C and the capacitor 166C are charged, no current flows through the capacitor 164C and the capacitor 166C, and therefore the control signal is not divided. If the control signal is a voltage that allows the first FET 164 and the second FET 166 to operate in the linear region 74, the first FET 164 and the second FET 166 are linear from the saturation region 72 by inputting a control signal that is not divided into the respective gates. The operation is switched to the operation in the area 74.

  As described above, each of the first FET 164 and the second FET 166 can be operated in the saturation region 72 by increasing the resistance value, which is a constant of the resistors 164R and 166R. It is desirable that the operation in the saturation region 72 is continued at least until the charging of the electrolytic capacitor 40C is completed. In the present embodiment, the time from when the control signal is output to when the electrolytic capacitor 40C is charged and the potential difference between the electrolytic capacitor 40C and the positive electrode of the battery 80 can be eliminated is defined as a predetermined time.

  As described above, the voltage division of the control signal is continued until the capacitor 164C and the capacitor 166C are charged. Therefore, by increasing the capacitance, which is a constant of the capacitors 164C and 166C, and setting the time required for each capacitor to charge more than a predetermined time, the first FET 164 and the second FET 166 can be operated in the saturation region 72 for a longer time. it can. The constants and predetermined time of each of the electrolytic capacitor 40C, the capacitor 164C, the resistor 164R, the capacitor 166C, and the resistor 166R are specifically determined through calculations and experiments using actual machines.

  In the present embodiment, the first FET 164 and the second FET 166 are provided for taking measures against energization by the parasitic diode 164P of the first FET 164 and ensuring circuit redundancy. However, the second shutdown mechanism 162 may be configured with the second FET 166, the resistor 166R, the capacitor 166C, and the Zener diode 166D if measures against the parasitic diode 164P and circuit redundancy are not required.

  As described above, according to the present embodiment, after the first FET 164 and the second FET 166 are started to operate in the saturation region 72 by setting the constants of the capacitor 164C, the resistor 164R, the capacitor 166C, and the resistor 166R, It is possible to operate in the linear region 74. As a result, the generation of inrush current due to the operation of the first FET 164 and the second FET 166 can be suppressed, and the electrolytic capacitor 40C can be charged in advance before the first FET 164 and the second FET 166 operate in the linear region 74. Can alleviate the effects.

DESCRIPTION OF SYMBOLS 10 ... Motor unit, 12 ... Rotor, 12A ... Rotor magnet, 12B ... Hall element, 14 ... Stator, 14U ... U-phase coil, 14V ... V-phase coil, 14W ... W-phase coil, 16 ... Shaft, 18 ... Upper case, DESCRIPTION OF SYMBOLS 20 ... Motor controller, 22 ... Board | substrate, 24 ... Heat sink, 32 ... Control part, 32D ... Diode, 40 ... Power part, 40C ... Electrolytic capacitor, 44 ... Inverter circuit, 44A, 44B, 44C, 44D, 44E, 44F ... FET, 46 ... coil, 48 ... reverse connection prevention FET, 52 ... motor, 54 ... voltage divider, 54A ... thermistor, 54B ... resistor, 56 ... current detector, 56A ... shunt resistor, 56B ... amplifier, 58 ... voltage sensor, 60 ... Lower case, 62 ... Second shutdown mechanism, 64 ... First FET, 64C ... Capacitor, 4D ... Zener diode, 64P ... parasitic diode, 64R ... resistor, 66 ... second FET, 66D ... zener diode, 66R2 ... resistor, 66R1 ... resistor, 68 ... control transistor, 70 ... cutoff region, 72 ... saturation region, 74 ... linear Area 80 80 battery 82 air conditioner ECU 162 second shutdown mechanism 164 first FET 164C capacitor 164D zener diode 164P parasitic diode 164R resistor 166 second FET 166C capacitor 166D ... Zener diode, 166R ... Resistance, 168 ... Zener diode, 262 ... Second shutdown mechanism, 264 ... Precharge mechanism

Claims (5)

A drive circuit for generating a voltage to be applied to a terminal of a motor coil;
A field effect transistor that electrically connects the drive circuit and the battery when turned on, and a voltage dividing circuit that applies a divided voltage to the gate of the field effect transistor, the voltage saturating the field effect transistor A switch mechanism in which constants of elements constituting the voltage dividing circuit are determined so that the voltage is large enough to operate in a region;
A control unit that outputs a control signal for turning on the field effect transistor, and that controls the drive circuit based on a command signal from a host controller;
Including a motor control device. The field effect transistor is P-type;
The voltage dividing circuit is a circuit that divides the voltage of the battery applied to the source of the field effect transistor and applies the divided voltage to the gate of the field effect transistor, and a first resistor that connects the source and the gate; A second resistor having one end connected to the gate; a control transistor having a collector connected to the other end of the second resistor, an emitter grounded, and a control signal input to a base;
When the control transistor is turned on by the input of the control signal, the voltage applied to the gate of the field effect transistor by the voltage dividing circuit is a voltage that causes the field effect transistor to operate in the saturation region. The motor control device according to claim 1, wherein the resistance value of the second resistor is determined to be   The control unit changes the control signal by changing the control signal so that a current between a collector and an emitter of the control transistor increases when a predetermined time or more has elapsed after outputting the control signal. 3. The motor control device according to claim 2, wherein a voltage applied to a gate of the field effect transistor by the circuit is a voltage having a magnitude sufficient to operate the field effect transistor in a linear region. The field effect transistor is N-type;
The voltage dividing circuit is a circuit that divides the control signal to the gate of the field effect transistor, a first resistor having one end connected to the control unit and the other end connected to the gate, and one end connected to the gate. A second resistor having a connected capacitor and an element connected to the other end of the capacitor, the terminal of the element being grounded,
When the control signal is input, the voltage applied to the gate of the field effect transistor by the voltage dividing circuit is a voltage that is large enough to operate the field effect transistor in the saturation region. The motor control device according to claim 1, wherein the resistance value is determined.   5. The motor control device according to claim 4, wherein the capacity of the capacitor is set so that a period from when the control signal is input to when the capacitor is charged is equal to or longer than a predetermined time.