JP2016158443A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict a current in a motor control device in which a PWM control is performed by effectively detecting an overcurrent.SOLUTION: A motor control device comprises: a current supply circuit (110) that is controlled by a PWM signal and supplies a current to a motor; an overcurrent detection circuit (170) that outputs a signal indicating whether or not it is in an overcurrent state on the basis of the current flowing in the current supply circuit; a filter circuit (160) that outputs a signal inputted from the overcurrent detection circuit by delaying for a predetermined filter period; a variable resistance circuit (130) that is connected into a path of the current flowing in the current supply circuit; and a resistance control circuit (150) that increases the resistance of the variable resistance circuit on the basis of the signal inputted from the filter circuit and indicating the overcurrent state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor control device.

  Patent Document 1 discloses an overcurrent detection circuit provided in a motor control device. The overcurrent detection circuit includes a resistor that detects overcurrent, a filter circuit that is connected across the resistor, and a signal that stops driving the motor when the output voltage of the filter circuit exceeds a reference value. And a comparison circuit for outputting. The resistor has a time constant determined by the resistance value of the resistor and the leakage inductance. Since this time constant changes the current waveform flowing through the resistor, it affects the detection accuracy of the overcurrent. The overcurrent detection circuit of Patent Document 1 compensates the time constant of the resistor with the time constant of the filter circuit, thereby approximating the waveform of the current flowing through the resistor and the waveform of the output voltage of the filter circuit, thereby detecting the overcurrent. Accuracy can be increased.

  Patent Document 2 discloses a control device for an electric retractable door mirror using a resistance element such as a PTC (Positive Temperature Coefficient) element as overcurrent detection means. When the current flowing through the PTC element increases due to the occurrence of an overcurrent, the resistance value of the PTC element increases and the potential at the connection point of the PTC element rises. When this potential increase is detected, the drive current of the door mirror motor is cut off by the electronic switch.

JP 2004-312955 A JP 2002-347522 A

  PWM (Pulse Width Modulation) control is widely performed as a motor control method. Patent Document 1 and Patent Document 2 do not disclose a technique for detecting an overcurrent and a problem at that time in a motor control device that performs PWM control. On the other hand, a motor control device that performs PWM control is also required to perform overcurrent detection more effectively.

  An object of this invention is to provide the motor control apparatus by PWM control which can detect an overcurrent more effectively and can limit an electric current.

  According to an embodiment of the present invention, a current supply circuit that is controlled by a PWM signal and supplies a current to the motor, and a signal indicating whether or not an overcurrent state is present based on the current flowing through the current supply circuit. An overcurrent detection circuit for outputting, a filter circuit for delaying and outputting a signal input from the overcurrent detection circuit by a predetermined filter period, and a variable resistance circuit connected in a path of a current flowing through the current supply circuit And a resistance control circuit that increases the resistance of the variable resistance circuit based on a signal input from the filter circuit and indicating an overcurrent state.

  ADVANTAGE OF THE INVENTION According to this invention, the motor control apparatus by PWM control which can detect an overcurrent more effectively and can limit an electric current is provided.

It is a block diagram which shows the structure of the motor control apparatus which concerns on 1st Embodiment. It is a drive timing diagram of the motor which concerns on 1st Embodiment. It is a graph which shows the time change of the electric current in the case of a low resistance state, and the case of a high resistance state. It is a block diagram which shows the structure of the motor control apparatus which concerns on a comparative example. It is a figure explaining the operation | movement of the overcurrent restriction | limiting in the motor control apparatus of a comparative example. It is a figure explaining the operation | movement of the overcurrent restriction | limiting in the motor control apparatus of this embodiment. It is a block diagram which shows the structure of the motor control apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the motor control apparatus which concerns on 3rd Embodiment. It is a block diagram which shows the structure of the motor control apparatus which concerns on 4th Embodiment. It is a block diagram which shows the structure of the motor control apparatus which concerns on 5th Embodiment.

  Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, unless otherwise specified, the scope of the present invention is not limited to the form specifically described in the embodiments described below. In the drawings described below, components having the same functions are denoted by the same reference numerals, and repeated description thereof may be omitted.

<First Embodiment>
FIG. 1 is a block diagram illustrating a configuration of the motor control device according to the first embodiment. The motor control device of this embodiment is a control device for controlling ON / OFF, rotation speed, rotation direction, and the like of the motor 120. In the present embodiment, the motor 120 is a three-phase brushless DC motor as an example, but the present invention can be applied to any motor in which PWM control is performed.

  The motor control device includes a current supply circuit 110, a PWM signal generation circuit 140, a resistance control circuit 150, a filter circuit 160, and an overcurrent detection circuit 170. The current supply circuit 110 is a circuit that supplies a drive current for operating the motor 120, and includes PMOS transistors P1, P2, and P3, NMOS transistors N1, N2, and N3, and three variable resistance circuits 130.

  The power supply voltage Vdd is input to the sources of the PMOS transistors P1, P2, and P3. A PWM signal is input from the PWM signal generation circuit 140 to the gates of the PMOS transistors P1, P2, and P3. The input terminal of the variable resistance circuit 130 is connected to the drains of the PMOS transistors P1, P2, and P3.

  Each variable resistance circuit 130 includes resistance elements Rx1 and Rx2 and switches SW1 and SW2. Hereinafter, the reference numerals attached to the resistance elements indicate the resistance values of the resistance elements. That is, the resistances of the resistance elements Rx1 and Rx2 are Rx1 and Rx2, respectively. One ends of the switches SW1 and SW2 are connected in common and constitute an input end of the variable resistance circuit 130. The other ends of the switches SW1 and SW2 are connected to one ends of the resistance elements Rx1 and Rx2, respectively. The other ends of the resistance elements Rx1 and Rx2 are connected in common and constitute an output end of the variable resistance circuit 130. The switches SW1 and SW2 are controlled by a control signal from the resistance control circuit 150. The switches SW1 and SW2 are composed of, for example, MOS transistors.

  When the switch SW1 is turned on and the switch SW2 is turned off, the resistance of the variable resistance circuit 130 becomes Rx1. When the switch SW1 is turned off and the switch SW2 is turned on, the resistance of the variable resistance circuit 130 is Rx2. When both the switches SW1 and SW2 are turned on, the resistance of the variable resistance circuit 130 is (Rx1 × Rx2) / (Rx1 + Rx2). In this way, by switching on and off the switches SW1 and SW2 and switching the connection relationship, one resistance value can be selected from among a plurality of resistance values for the resistance of the variable resistance circuit 130. The number of resistance elements and switches is not limited to two, but may be one or three or more.

  The drains of the NMOS transistors N1, N2, and N3 are connected to the output terminal of the variable resistance circuit 130, respectively, and further connected to the input / output terminal of the motor 120.

  A PWM signal is input from the PWM signal generation circuit 140 to the gates of the NMOS transistors N1, N2, and N3. The drains of the NMOS transistors N1, N2, and N3 are connected to the overcurrent detection circuit 170. The grounded resistance element R1 is connected to the drains of the NMOS transistors N1, N2, and N3.

  As shown in FIG. 1, the motor 120 can be expressed as an equivalent circuit using three equivalent inductances Lm and three equivalent resistances Rm connected in a delta connection. Hereinafter, the symbol attached to each equivalent inductance represents the value of the inductance. If the nodes to which the NMOS transistors N1, N2, and N3 are connected are nodes U, V, and W, respectively, an equivalent inductance Lm and an equivalent resistance Rm are connected in series between the node U and the node V. Similarly, another equivalent inductance Lm and equivalent resistance Rm are connected in series between the node V and the node W and between the node W and the node U. In this embodiment, a delta connection circuit is shown as an equivalent circuit of the motor 120, but a star connection circuit may be used.

  The overcurrent detection circuit 170 is a circuit that measures the voltages of the drain nodes of the NMOS transistors N1, N2, and N3 and outputs a signal indicating whether or not the current is equal to or greater than a predetermined threshold. The overcurrent detection circuit 170 can be configured by, for example, a comparator circuit that compares the magnitude relationship between the input voltage and the threshold voltage. When the current supplied from the current supply circuit 110 to the motor 120 is I1, the voltage V1 measured by the overcurrent detection circuit 170 is a voltage drop (I1 × R1) due to the resistance element R1. For this reason, the overcurrent detection circuit 170 can detect whether or not an overcurrent flows through the motor 120 by measuring the voltage V1. The overcurrent detection circuit 170 determines whether or not the measured voltage V1 is greater than or equal to a predetermined threshold value. The overcurrent detection circuit 170 outputs to the filter circuit 160 a high level signal indicating an overcurrent condition when the threshold value is greater than or equal to the threshold value, and a low level signal indicating that no overcurrent condition exists when the value is less than the threshold value. To do.

  The filter circuit 160 is a circuit for filtering a short-time current fluctuation so that an overcurrent is not erroneously detected when the current instantaneously exceeds a threshold due to noise such as ringing. The filter circuit 160 realizes this function by delaying the signal input from the overcurrent detection circuit 170 by a predetermined filter period Tf and outputting the delayed signal. As an example of a specific configuration, the filter circuit 160 includes a delay circuit having a time constant corresponding to a predetermined filter time, an on-delay timer circuit that outputs a signal delayed by a predetermined delay time with respect to the input signal, and the like. Can be done. An output signal from the filter circuit 160 is input to the PWM signal generation circuit 140 and the resistance control circuit 150.

  The PWM signal generation circuit 140 controls a current supplied to the motor 120 by outputting a PWM signal to the gates of the PMOS transistors P1, P2, and P3 and the NMOS transistors N1, N2, and N3. When a signal indicating that an overcurrent is detected from the overcurrent detection circuit 170 via the filter circuit 160 is input to the PWM signal generation circuit 140, the PWM signal generation circuit 140 stops supplying current to the motor 120. Alternatively, each transistor is controlled to decrease.

  When a signal indicating that an overcurrent has been detected is input from the overcurrent detection circuit 170 via the filter circuit 160, the resistance control circuit 150 switches each switch SW1 and SW2 of each variable resistance circuit 130 to change each variable. The resistance of the resistance circuit 130 is increased. As an example, Rx1 <Rx2 is set, and in a normal operation, only the switch SW1 is turned on and a low resistance state is set. When an overcurrent is detected, the switch SW1 is turned off and the switch SW2 is turned on. The resistance may be increased by setting the resistance state. As another example, during normal operation, both the switches SW1 and SW2 are kept in a low resistance state, and when an overcurrent is detected, one of the switches SW1 and SW2 is turned off. The resistance can be increased by setting the state.

  Next, a method for driving the motor 120 by the current supply circuit 110 and a current flowing through the current supply circuit 110 will be described with reference to FIGS.

  FIG. 2 is a drive timing chart of the motor 120 according to the first embodiment. This drive timing diagram schematically shows the level of the control signal input from the PWM signal generation circuit 140 to the gates of the PMOS transistors P1, P2, and P3 and the NMOS transistors N1, N2, and N3 and the current flowing through the motor 120. Is. For ease of understanding, the control signals input to the PMOS transistors P1, P2, and P3 are illustrated by inverting the high level and the low level from the actually input voltage. That is, for each control signal, the high level corresponds to the on state of the transistor, and the low level corresponds to the off state of the transistor. In the figure, I (U−V), I (U−W), and I (V−W) represent currents from the node U to V, the node U to W, and the node V to W of the motor 120, respectively.

  In the period T1, the PMOS transistor P1 and the NMOS transistor N2 are on. As a result, a current from node U of motor 120 toward V flows. The control signal for each transistor is a PWM signal that repeatedly turns on and off at a predetermined PWM frequency and duty ratio.

  In the period T2, the NMOS transistor N2 is turned off and the NMOS transistor N3 is turned on. As a result, the current flowing through the motor 120 changes in the direction from the node U to W. Hereinafter, in the period from T3 to T6, the transistors to be turned on are sequentially switched, and the current flowing through the motor 120 is also sequentially changed. After time T6, the state returns to the same state as time T1. Thus, the motor 120 operates with six states as one cycle.

  Next, the current flowing through the motor 120 will be described. In each period from the period T1 to the period T6, the direction of the current is changed, but the magnitude of the current is almost constant, so the case of the period T1 will be described.

  The on-resistances of the PMOS transistor P1 and the NMOS transistor N2 are Rp and Rn, respectively. The combined resistance Rma of the motor is Rma = 2 / 3Rm. Similarly, the combined inductance Lma of the motor is Lma = 2 / 3Lm. In the following description, it is assumed that only the switch SW1 is on in a normal state where no overcurrent is detected, and only the switch SW2 is on when an overcurrent is detected. Further, Rx1 <Rx2.

  In a normal state where no overcurrent is detected, the combined resistance Ra1 of all paths through which current flows is Ra1 = (Rp + Rx1 + Rma + Rn + R1). At this time, the current In (t) supplied from the motor 120 by the current supply circuit 110 is expressed by the following equation. In addition, t is the time after the voltage is applied, and In (t) indicates the time change of the current after the voltage is applied.

  Here, when an overcurrent is detected and only the switch SW2 is turned on, the combined resistance Ra2 of all paths through which the current flows is Ra2 = (Rp + Rx2 + Rma + Rn + R1). At this time, the current Io (t) supplied from the motor 120 by the current supply circuit 110 is expressed by the following equation.

  FIG. 3 is a graph showing changes in current over time in a low resistance state and a high resistance state. The curve indicated by the alternate long and short dash line is the current In (t) corresponding to the low resistance state, and the curve indicated by the solid line is the current Io (t) corresponding to the high resistance state. From the graph, the current Io (t) is lower than the current In (t) at both the rising edge of the current and the time when the current is saturated.

  As described above, when a signal indicating that the current is equal to or greater than the predetermined threshold is input, the resistance control circuit 150 increases the resistance value of the variable resistance circuit 130 from Rx1 to Rx2. Thereby, the current supplied to the motor 120 when an overcurrent is generated can be reduced.

  Next, with reference to FIG. 4 to FIG. 6, the effect of overcurrent detection and limitation by the configuration of the present embodiment will be described in comparison with the present embodiment and a comparative example.

  FIG. 4 is a block diagram illustrating a configuration of a motor control device according to a comparative example. The motor control device of FIG. 4 is different from the motor control device shown in FIG. 1 in that the variable resistance circuit 130 and the resistance control circuit 150 are not provided. In the motor control apparatus of the comparative example, the supply of current to the motor 120 is limited only by the PWM signal. That is, when a signal indicating that an overcurrent is detected from the overcurrent detection circuit 170 via the filter circuit 160 is input to the PWM signal generation circuit 140, the PWM signal generation circuit 140 supplies the current to the motor 120. Each transistor is controlled to stop or decrease. On the other hand, since the motor control device according to the comparative example does not include the variable resistance circuit 130 and the resistance control circuit 150, the current is not limited by increasing the resistance.

  FIG. 5 is a diagram for explaining an overcurrent limiting operation in the motor control device of the comparative example. FIG. 5 shows the drive current flowing through the motor 120, the output voltage of the overcurrent detection circuit 170, the output voltage of the filter circuit 160, and the output voltage from the PWM signal generation circuit 140. With reference to FIG. 5, changes in the drive current when the drive current applied to the motor 120 increases and exceeds the overcurrent detection threshold when a PWM signal is input to each transistor will be described. Note that the duty ratio of the PWM signal is shown as 50%, but the same applies to different values.

  During the period from time t1 to time t2, the PWM signal is at a high level, and current is supplied from the current supply circuit 110 to the motor 120. As a result, the drive current increases during the period from time t1 to time t2. During the period from time t2 to time t3, the PWM signal is at a low level, and current supply from the current supply circuit 110 to the motor 120 is stopped. Therefore, the drive current decreases from time t2 to time t3. At time t3, the PWM signal becomes high level again and the drive current starts to increase. Thus, the current is repeatedly turned on and off by the PWM signal, and the motor 120 is PWM-controlled. Since the drive current does not exceed the overcurrent detection threshold set in the overcurrent detection circuit 170 during the period from the time t1 to the time t3, the output of the overcurrent detection circuit 170 is at a low level, and the overcurrent is limited. Is not performed.

  At time t4, the drive current exceeds the overcurrent detection threshold. As a result, the output of the overcurrent detection circuit 170 becomes high level. However, since the filter circuit 160 has the filter period Tf, the output of the filter circuit 160 remains at the low level at the time t4. Therefore, the PWM signal does not change at time t4.

  At time t5 after the filter period Tf has elapsed from time t4, the output of the filter circuit 160 becomes high level. As a result, the PWM signal becomes low level, and the drive current starts to decrease. A portion indicated by a broken line in the PWM signal in the figure shows a PWM signal waveform corresponding to a duty ratio of 50% output when no overcurrent is detected for reference.

  At time t6, the output of the overcurrent detection circuit 170 becomes low level. This operation is to prevent the PWM signal generation circuit 140 from malfunctioning due to the overcurrent detection circuit 170 during normal operation. The reason why this operation is necessary will be described. When the PWM signal rises from a low level to a high level, a large inrush current may instantaneously flow through the circuit. Unlike the above-described overcurrent, the inrush current is considered to occur within the range of normal operation, and thus does not necessarily require detection. On the other hand, if the overcurrent detection circuit 170 is operating at the rising edge of the PWM signal, the overcurrent is detected every time the PWM signal becomes high level, and the supply of current may be stopped. Can affect. From such a background, the motor control device that performs PWM control stops the detection of the overcurrent detection circuit 170 before and after the PWM signal becomes high level in order to prevent the PWM signal generation circuit 140 from malfunctioning during normal operation. It is configured as follows. The time t6 is a time corresponding to the detection stop of the overcurrent detection circuit 170. Since it is necessary to stop overcurrent detection at time t7 when the PWM signal becomes high level, the timing at time t6 is set to be about the filter period Tf of the filter circuit 160 before time t7. The

  At time t7, the PWM signal becomes high level. For the above-described reason, the output of the overcurrent detection circuit 170 becomes low level at time t6, so that the output of the filter circuit 160 becomes low level at time t7. As a result, current starts to be supplied again from the current supply circuit 110 to the motor 120. That is, although the drive current exceeds the overcurrent detection threshold, the drive current increases during a period from time t7 to time t8 corresponding to the filter period Tf.

  Immediately after the PWM signal at time t7 becomes high level, the detection of the overcurrent detection circuit 170 is resumed. Since the drive current exceeds the overcurrent detection threshold, the output of the overcurrent detection circuit 170 becomes high level.

  At time t8 after the filter period Tf has elapsed from time t7, the output of the filter circuit 160 becomes high level. As a result, the PWM signal becomes low level, and the drive current decreases until time t9, which is the rise time of the next PWM signal. As shown in FIG. 5, the amount of increase in drive current during the period from time t7 to time t8 is greater than the amount of decrease in drive current during the period from time t8 to time t9. Thereafter, the same driving is repeated for each period of the PWM signal, so that the driving current continues to increase with time.

  In the motor control device of the comparative example, even if the drive current exceeds the overcurrent detection threshold because the overcurrent detection stops at the rising edge of the PWM signal and the filter period 160 is set by the filter circuit 160. A phenomenon in which the drive current increases may occur. In particular, when the increase amount of the drive current becomes larger than the decrease amount as shown in FIG. 5, the drive current continuously increases even after the overcurrent detection threshold is exceeded. Therefore, in the comparative motor control device that does not include the variable resistance circuit 130 and the resistance control circuit 150, it may be difficult to suppress overcurrent.

  The motor control device of the present embodiment can reduce the occurrence of problems as in the comparative example described above. FIG. 6 is a diagram for explaining the overcurrent limiting operation in the motor control apparatus of this embodiment. FIG. 6 shows the output current of the resistance control circuit 150 in addition to the drive current flowing through the motor 120, the output of the overcurrent detection circuit 170, the output voltage of the filter circuit 160, and the output voltage from the PWM signal generation circuit 140. Yes. Here, when the output voltage of the resistance control circuit 150 is at a low level, the switch SW1 is on and the switch SW2 is off. At this time, the resistance is Rx1. When the output voltage of the resistance control circuit 150 is high, the switch SW1 is off and the switch SW2 is on. At this time, the resistance is Rx2. Further, Rx1 <Rx2. Hereinafter, the operation of the motor control device of the present embodiment will be described in the same manner as the comparative example of FIG. 5, but the description of the overlapping portions will be simplified or omitted.

  The operation during the period from time t1 to time t5 is the same as that in the comparative example. During this period, the output of the resistance control circuit 150 is at a low level. Therefore, the resistance of the variable resistance circuit 130 is Rx1.

  At time t5, the output of the filter circuit 160 becomes high level. As a result, the PWM signal becomes low level, and the drive current starts to decrease. In response to this output signal, the output of the resistance control circuit 150 also goes high. As a result, the resistance of the variable resistance circuit 130 increases from Rx1 to Rx2.

  At time t7, the PWM signal becomes high level. As a result, current starts to be supplied again from the current supply circuit 110 to the motor 120. Since the resistance of the variable resistance circuit 130 increases during the period from the time t7 to the time t8, the increase rate of the drive current (in FIG. 6, the slope of the drive current during the period from the time t7 to the time t8) is higher than that in the comparative example. Has also been reduced. The increase rate of the drive current during this period is set so that the increase amount of the drive current does not become larger than the decrease amount. Therefore, in the configuration of the present embodiment, when the drive current temporarily exceeds the overcurrent detection threshold, the problem that the drive current continuously increases after the overcurrent detection threshold is exceeded is suppressed.

  At time t10, the drive current becomes less than the overcurrent detection threshold. As a result, the output of the overcurrent detection circuit 170 becomes low level. At time t11 after the elapse of the filter period Tf from time t10, the output of the filter circuit 160 becomes low level, and accordingly, the output of the resistance control circuit 150 also becomes low level. As a result, the resistance of the variable resistance circuit 130 returns from Rx2 to Rx1.

  In the configuration of the present embodiment described above, the condition for the resistance of the variable resistance circuit 130 to return from Rx2 to Rx1 is that the output of the filter circuit 160 becomes low level at a timing other than the rise of the PWM signal. However, this condition is not limited to the above condition and can be modified as appropriate.

  For example, the resistance of the variable resistance circuit 130 may be configured to return from Rx2 to Rx1 when the output of the filter circuit 160 is at a low level for a predetermined time or longer. As a result, the current can be more reliably limited.

  In another example, a recovery condition threshold smaller than the overcurrent detection threshold may be set separately, and the resistance of the variable resistance circuit 130 may return from Rx2 to Rx1 when the drive current becomes less than the recovery condition threshold. Good. As a result, the current can be more reliably limited.

  As described above, according to the motor control device of the present embodiment, the problem that the drive current continuously increases even after the drive current exceeds the overcurrent detection threshold, which may be a problem in the configuration of the comparative example, is suppressed. Further, when the drive current does not exceed the overcurrent detection threshold, the resistance value is set low, so that normal operation is not affected. Therefore, a motor control device that can detect an overcurrent and limit the current more effectively is provided.

<Second Embodiment>
FIG. 7 is a block diagram illustrating a configuration of a motor control device according to the second embodiment. In this embodiment, the circuit configuration of the variable resistance circuit 730 is different from that of the first embodiment. The variable resistance circuit 730 includes a resistance element Rx1 and a switch SW1. That is, the number of resistance elements and switches included in the variable resistance circuit 730 is reduced as compared with the case of the first embodiment. When the switch SW1 of the variable resistance circuit 730 is on, the resistance of the variable resistance circuit 730 is only a wiring resistance and an on-resistance of the switch SW1, and thus has a sufficiently small value. When the switch SW1 of the variable resistance circuit 730 is off, the resistance of the variable resistance circuit 730 is Rx1. Therefore, also in the configuration of the present embodiment, the resistance of the variable resistance circuit 730 can be switched so as to select one value from two values, and the same control as in the first embodiment is possible.

  Therefore, according to the present embodiment, a motor control device that provides the same effects as those of the first embodiment is provided. In addition, since the number of switches and resistance elements is reduced, this embodiment is effective for downsizing, cost reduction, and simplification of the control method.

<Third Embodiment>
FIG. 8 is a block diagram illustrating a configuration of a motor control device according to the third embodiment. This embodiment is different from the first embodiment in that one variable resistance circuit 130 is provided between the sources of the NMOS transistors N1, N2, and N3 and the resistance element R1. The circuit configuration of the variable resistance circuit 130 is the same as that of the first embodiment. That is, the number of variable resistance circuits 130 is reduced as compared with the case of the first embodiment. Also in the configuration of the present embodiment, the resistance value can be controlled as in the first embodiment.

  Therefore, according to the present embodiment, a motor control device that provides the same effects as those of the first embodiment is provided. In addition, since the number of switches and resistance elements is reduced, this embodiment is effective for downsizing, cost reduction, and simplification of the control method.

<Fourth Embodiment>
FIG. 9 is a block diagram illustrating a configuration of a motor control device according to the fourth embodiment. This embodiment is different from the first or third embodiment in that one variable resistance circuit 130 is provided between the sources of the PMOS transistors P1, P2, and P3 and the power supply voltage Vdd. The circuit configuration of the variable resistance circuit 130 is the same as that of the first or third embodiment. That is, the number of variable resistance circuits 130 is reduced as compared with the case of the first embodiment. Also in the configuration of the present embodiment, the resistance value can be controlled as in the first embodiment.

  Therefore, according to the present embodiment, a motor control device that provides the same effects as those of the first embodiment is provided. In addition, the present embodiment can reduce the number of switches and resistance elements, and thus is effective for downsizing, cost reduction, control method simplification, and the like.

<Fifth Embodiment>
In the first to fourth embodiments, a three-phase brushless DC motor is exemplified as the motor 120. For example, the motor 120 may be a single-phase motor or a motor having four or more phases. Good. Hereinafter, as a fifth embodiment, an application example of the present invention when a single-phase motor is driven by an H-bridge circuit will be described.

  FIG. 10 is a block diagram illustrating a configuration of a motor control device according to the fifth embodiment. The motor control device of this embodiment controls a single-phase motor 1020 in place of the three-phase motor of the first to fourth embodiments. The current supply circuit 1010 includes PMOS transistors P1 and P2, NMOS transistors N1 and N2, and two variable resistance circuits 130. Since the current supply circuit 1010 of this embodiment is obtained by deleting the variable resistance circuit 130 including one phase of transistors from the configuration of the first to fourth embodiments, detailed description of the circuit configuration is omitted.

  Therefore, according to the present embodiment, a single-phase motor control device that provides the same effects as those of the first embodiment is provided. That is, the present invention is applicable to motors other than three-phase brushless DC motors.

<Other embodiments>
The motor control devices according to the first to fifth embodiments described above can be suitably used for controlling a vehicle-mounted motor to which a large current can be input. An example of such an in-vehicle motor is a water pump driving motor. The drive current flowing through the water pump drive motor is as large as about 20A. In such applications, problems such as transistor failure may occur if overcurrent is not reliably detected. The present invention can be used more suitably in controlling a motor that can receive such a large current.

  However, the present invention is not limited to such an application, and can be applied to control of any motor. For example, the present invention may be applied to a drive motor such as a vehicle opening / closing body or a slide seat. By applying the present invention to these applications, overcurrent can be detected more reliably in situations where a large amount of current can flow through the motor, such as when the motor is started, when the drive unit is caught. it can.

  In the motor control devices according to the first to fifth embodiments described above, the number of resistance values that can be varied by the variable resistance circuit is two or three. However, a larger number of resistance values can be set. A large number of resistance elements may be arranged so that As a result, the current can be limited in a plurality of stages, and the overcurrent can be detected more reliably. Furthermore, the design of one power supply circuit can be shared by changing the resistance according to the performance of the motor. Further, even if the motor is changed at the design stage, it is not necessary to redesign the motor control device. Therefore, the design cost is reduced.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, two or more configurations shown in the first to fifth embodiments may be arbitrarily selected and combined. The above embodiments are merely examples of some aspects to which the present invention can be applied, and do not prevent appropriate modifications and variations from being made without departing from the spirit of the present invention.

110 current supply circuit 120 motor 130 variable resistance circuit 140 PWM signal generation circuit 150 resistance control circuit 160 filter circuit 170 overcurrent detection circuit

Claims (7)

A current supply circuit controlled by a PWM signal to supply current to the motor;
An overcurrent detection circuit that outputs a signal indicating whether or not an overcurrent state based on a current flowing through the current supply circuit;
A filter circuit that outputs a signal input from the overcurrent detection circuit with a delay of a predetermined filter period; and
A variable resistance circuit connected in a path of a current flowing through the current supply circuit;
A motor control device comprising: a resistance control circuit that increases a resistance of the variable resistance circuit based on a signal that is input from the filter circuit and indicates an overcurrent state.   The motor control device according to claim 1, wherein the overcurrent detection circuit outputs a signal indicating an overcurrent state when a current flowing through the current supply circuit is equal to or greater than a first threshold.   After the resistance control circuit increases the resistance of the variable resistance circuit, the resistance control circuit determines the resistance of the variable resistance circuit based on a signal that is input from the filter circuit and indicates that it is not in an overcurrent state. The motor control device according to claim 1, wherein the motor control device is decreased.   After the resistance control circuit increases the resistance of the variable resistance circuit, the resistance control is performed when a signal input from the filter circuit indicating that it is not in an overcurrent state is continuously input for a predetermined time or more. The motor control device according to claim 1, wherein the circuit reduces a resistance of the variable resistance circuit.   After the resistance control circuit increases the resistance of the variable resistance circuit, based on a signal that is input from the filter circuit and indicates that the current is less than a second threshold value that is smaller than the first threshold value. The motor control device according to claim 2, wherein the resistance control circuit decreases a resistance of the variable resistance circuit.   The motor control device according to claim 1, wherein the variable resistance circuit is configured to be able to select one resistance value from at least two resistance values. The variable resistance circuit is:
At least one resistive element;
And at least one switch for switching the connection relationship of the resistance elements,
The motor control device according to claim 1, wherein the resistance control circuit controls a resistance of the variable resistance circuit by switching each of the at least one switch.

Images