JP6109059B2 - Motor control circuit and motor control circuit short detection method - Google Patents

Description

  The present invention relates to a motor control circuit and a motor control circuit short detection method.

  The active force pedal has a function of performing an operation of increasing the reaction force of the pedal by generating a force in a direction to return the accelerator pedal. According to this active force pedal, it is possible to prevent sudden start and acceleration of the vehicle and to support eco-driving by actively controlling the reaction force of the accelerator pedal. In such an active force pedal, a motor that provides a reaction force to the accelerator pedal is provided, and the reaction force of the accelerator pedal is actively controlled by controlling the torque of the motor.

  In addition, as a motor control circuit for controlling a motor used in such an active force pedal, a switching element such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is used so that a current value flowing through the motor becomes a target value. Therefore, a power supply for controlling the power supplied to the motor by PWM (Pulse Width Modulation) is used. That is, in such a motor control circuit, a target value of the motor torque is determined according to various conditions, and a driving current corresponding to the target value of the motor torque is obtained. Then, the target drive current and the current flowing through the motor are compared, and the duty ratio of the switching signal is controlled according to this comparison output. By such feedback control, the motor is driven with a desired torque.

  Further, as disclosed in Patent Document 1, in the motor control circuit, a shunt resistor is provided in the path of the power source that flows from the power source terminal to the ground terminal via the motor, and a short-circuit is detected by detecting the voltage across the shunt resistor. The state is determined. That is, when a short circuit of the motor occurs, the current flowing from the power supply terminal to the ground terminal via the motor becomes a large current. From this, the current of the path that flows from the power supply terminal to the ground terminal via the motor is detected from the voltage across the shunt resistor, and the detected value of this current is compared with a predetermined threshold value. Determines that a short circuit has occurred. In Patent Document 1, the on-resistance of a semiconductor switch is used as a shunt resistor.

JP 2000-299631 A

  However, in the configuration in which the short-circuit state is detected by comparing the current detection value detected by the shunt resistance in the power supply path to the motor with a predetermined threshold value, the motor has a short circuit with a certain short-circuit resistance (for example, a rare short circuit). When it happens, it is difficult to accurately detect the short-circuit condition.

  That is, when the short-circuit resistance is almost 0Ω, the current in the path to the motor becomes a large current, the current value detected from the voltage across the shunt resistance exceeds the threshold value, and a short state is detected. When a short circuit is detected, the rotation of the motor is stopped and circuit protection is achieved.

  However, when a short circuit having a certain short-circuit resistance occurs, the current detection value increases. Therefore, the pulse width of the switching signal is controlled so that the duty ratio is reduced by the feedback control described above. When the duty ratio of the switching signal is lowered, the current flowing through the path to the motor is reduced, so that the detected current value is lowered and a state where the detected current value does not exceed the threshold value may continue. In this case, there is a possibility that a state in which short detection cannot be performed continues with the technique described above. If a state in which a short circuit cannot be detected continues, a current continues to flow through the motor even during the control thereof, which places a burden on the motor. Also, in this case, the pedaling force when the accelerator pedal is depressed is different from the normal time, which gives the user a sense of discomfort.

  In view of the above problems, the present invention provides a motor control circuit and a motor control circuit short detection method capable of reliably detecting the occurrence of a short even when a short circuit having a certain short circuit resistance occurs. For the purpose.

In view of the above-mentioned problems, the present invention flows through a first switching element provided between a power supply terminal and a motor, a second switching element provided between a ground terminal and the motor, and the motor. A motor control unit that controls a duty ratio of a switching signal that controls on / off of the first and second switching elements according to a detected value of the current, and a path between the power supply terminal and the motor. If the first larger threshold detection value reaches a predetermined current flowing determines the short detection circuit determines that you output an overcurrent detection signal, when receiving the overcurrent detection signal is short-circuited a motor control circuit comprising a short judging unit, wherein the short determination unit, the duty ratio of the switching signal is smaller than the prescribed duty ratio, and, prior to Determining that a short circuit has occurred when the detected value of the current flowing in the path between the power supply terminal and the motor is greater than a second threshold value set to a value lower than the first threshold value. Features.

  According to the present invention, in the motor control circuit described above, the motor control unit stops the operation of the motor when it is determined by the short determination unit that a short circuit has occurred.

In the motor control circuit described above, the present invention is connected to a first shunt resistor provided in a path between the power supply terminal and the motor, and between the first shunt resistor and the motor. And the short determination unit uses the detected value of the current flowing in the path between the power supply terminal and the motor detected by the first shunt resistor to detect the short circuit. The motor control unit controls the duty ratio of the switching signal using a detected value of the current flowing through the motor detected by the second shunt resistor. Features.

In the motor control circuit according to the present invention, a free-wheeling diode is provided between the drain of the first switching element and the drain of the second switching element .

In the motor control circuit described above, the duty ratio of the switching signal is smaller than the specified duty ratio, and the detected value of the current flowing in the path between the power supply terminal and the motor is further provided. Has a timer unit that measures a time when the switching signal is greater than the second threshold , and the short determination unit has a duty ratio of the switching signal smaller than the specified duty ratio, and the power supply terminal and the motor when the detected value of the current flowing through the path between has duration magnitude Kunar time than the second threshold value is predetermined, and judging with the short circuit occurs.

Further, the present invention includes a first switching element provided between the power supply terminal and the motor, a second switching element provided between the ground terminal motor, is provided before SL motor detecting a current flowing through, according to the detected value of the current flowing in the motor, the short detection of the motor control circuit for controlling the duty ratio of the first and the second switching signal to the switching element oN / oFF controlled A method of detecting a current flowing in a path between the power supply terminal and the motor, wherein the detected value of the detected current is greater than a preset first threshold, or the switching smaller than the duty ratio of the signal is defined duty ratio, and, set to a value lower than the detection value of the first threshold value of the current flowing through the path between the power supply terminal motor Shi Yoto to and determines that has occurred in the case of any of greater than a second threshold value that is.

  According to the present invention, a short circuit occurs when it is detected that the duty ratio of the switching signal is equal to or less than a predetermined value and the detected value of the current flowing in the path between the power source and the motor is equal to or greater than the reference current value. Detected what happened. Thereby, even when a short circuit having a certain short circuit resistance occurs, the occurrence of the short circuit can be detected with high accuracy.

1 is a block diagram illustrating a configuration of a motor control circuit according to a first embodiment of the present invention. 1 is a functional block diagram of a motor control circuit according to a first embodiment of the present invention. It is a graph which shows the relationship between the duty ratio of a switching signal, and the detected current value from an upper stage current detection circuit. It is a flowchart used for description of the motor control circuit which concerns on the 1st Embodiment of this invention. It is a functional block diagram of the motor control circuit which concerns on the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a motor control circuit 1 according to the first embodiment of the present invention. As shown in FIG. 1, the motor control circuit 1 according to the first embodiment of the present invention includes MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) 11 and 12, resistors 13 and 14, a diode 15, A control circuit 30, an upper stage current detection circuit 31, a short detection circuit 32, a lower stage current detection circuit 33, and drive circuits 35 and 36 are provided.

  A resistor 13, a MOSFET 11, and a resistor 14 are connected in series between the power supply terminal 18 and the motor terminal 16. The MOSFET 12 is connected between the motor terminal 17 and the ground terminal 19. A DC power supply from the battery is supplied between the power supply terminal 18 and the ground terminal 19. A diode 15 is connected between the drain of the MOSFET 12 and the drain of the MOSFET 11 so that its anode is connected to the drain of the MOSFET 12 and its cathode is connected to the drain of the MOSFET 11. The diode 15 is for forming a closed circuit for the resistor 14 to detect the motor current during circulation or power generation.

  The MOSFETs 11 and 12 are switching elements that perform PWM (Pulse Width Modulation) control on the drive power supply of the motor 10. Switching signals are supplied to the gates of the MOSFETs 11 and 12 from the control circuit 30 via the drive circuits 35 and 36, respectively. The MOSFETs 11 and 12 are on / off controlled by this switching signal. The diodes 21 and 22 connected in parallel with the MOSFETs 11 and 12 are diodes for preventing backflow.

  The resistor 13 is a shunt resistor for detecting a short circuit. The voltage across the resistor 13 is supplied to the upper stage current detection circuit 31. The upper stage current detection circuit 31 detects the value of the current flowing through the path between the power supply terminal 18 and the ground terminal 19. The output of the upper stage current detection circuit 31 is supplied to the short detection circuit 32 and also supplied to the AD (Analog to Digital) input port of the control circuit 30. The resistor 41 and the capacitor 42 constitute an integration circuit that averages the current detection value from the upper stage current detection circuit 31. The short detection circuit 32 compares the current detection value from the upper stage current detection circuit 31 with the first threshold value Vr1, and performs short detection. The output of the short detection circuit 32 is supplied to the control circuit 30.

  The resistor 14 is a motor current detection shunt resistor for performing feedback control of the motor torque. The voltage across the resistor 14 is supplied to the lower current detection circuit 33. The lower stage current detection circuit 33 detects a current flowing through the motor 10. The current detection value from the lower stage current detection circuit 33 is supplied to the AD input port of the control circuit 30. The resistor 43 and the capacitor 44 constitute an integration circuit that averages the current detection values from the lower stage current detection circuit 33.

  As described above, in the motor control circuit 1 according to the first embodiment of the present invention, the two shunt resistors 13 and 14 are provided in the path between the power supply terminal 18 and the ground terminal 19. ing. The resistor 13 and the upper stage current detection circuit 31 detect the value of the current flowing through the path between the power supply terminal 18 and the ground terminal 19 in order to detect a short circuit. The resistor 14 and the lower-stage current detection circuit 33 detect the current flowing through the motor 10 in order to set the torque of the motor 10 to a target value.

  First, torque control in the motor control circuit 1 according to the first embodiment of the present invention will be described with reference to the functional block diagram of FIG.

  FIG. 2 is a functional block diagram showing parts necessary for the explanation of the operation from the motor control circuit 1 according to the first embodiment of the present invention shown in FIG. That is, in the configuration of the motor control circuit 1 shown in FIG. 1, portions unnecessary for the description of the operation, such as the resistor 41 and the capacitor 42, the resistor 43 and the capacitor 44, are deleted in FIG. MOSFETs 11 and 12 are shown as switch circuits based on their operation. The control circuit 30 is shown as a functional block based on its operation.

  The motor control circuit 1 according to the first embodiment of the present invention is used to control the motor 10 for applying a reaction force to the pedal, for example, in an active force pedal. The control circuit 30 contains a CPU (Central Processing Unit), a memory, an AD (Analog to Digital) converter, a DA (Digital to Analog) converter, and the like. The control circuit 30 performs various controls according to a program. . As shown in FIG. 2, when the control circuit 30 is blocked based on its function, it can be represented by a motor control unit 51, a short determination unit 52, and AD conversion units 53 and 54.

  The target torque value Sa is acquired from an upper control circuit (not shown) of the vehicle and is sent to the motor control unit 51. The motor control unit 51 calculates the target value of the drive current for the motor 10 based on the target torque value Sa obtained from the host control circuit.

  As described above, the current flowing through the motor 10 is detected by the lower-stage current detection circuit 33 from the voltage across the resistor 14. The current detection value Sb of the lower stage current detection circuit 33 is digitized by the AD conversion unit 53 and sent to the motor control unit 51.

  The motor control unit 51 compares the current detection value Sb from the lower stage current detection circuit 33 with the target value of the drive current set based on the target torque value Sa, and based on this comparison output, the pulse of the switching signal Controls the width (duty ratio). The switching signals Sc1 and Sc2 are supplied to the gates of the MOSFETs 11 and 12 via the drive circuits 35 and 36. Thereby, feedback control is performed such that the current value flowing through the motor 10 becomes a desired current, and the motor 10 can be rotated with a target torque.

  That is, when the current detection value Sb from the lower-stage current detection circuit 33 is smaller than the target value, the motor control unit 51 controls the pulse width of the switching signal so that the duty ratio of the switching signal is increased. Thereby, the electric current which flows through the motor 10 increases, and the torque of the motor 10 is raised. On the other hand, when the current detection value Sb from the lower-stage current detection circuit 33 is larger than the target value, the motor control unit 51 controls the pulse width of the switching signal so that the duty ratio of the switching signal becomes small. . Thereby, the electric current which flows through the motor 10 reduces, and the torque of the motor 10 is reduced. By such feedback control, the motor 10 can be rotated with a target torque.

  Next, short detection control in the motor control circuit 1 according to the first embodiment of the present invention will be described with reference to the functional block diagram of FIG.

  In FIG. 2, when a short circuit occurs in the motor 10, the resistance between the terminals of the motor 10 decreases, and an overcurrent flows in the path from the power supply terminal 18 to the ground terminal 19. Thereby, the detection current value from the upper stage current detection circuit 31 becomes large.

  As described above, the short detection circuit 32 compares the current detection value from the upper stage current detection circuit 31 with the first threshold value Vr1, and performs short detection. When the resistance between the motor terminals is almost 0Ω, such as when the motor terminal 16 and the motor terminal 17 are in contact, the current flowing through the path between the power supply terminal 18 and the ground terminal 19 is a large current. Thus, the current detection value from the upper stage current detection circuit 31 is larger than the first threshold value Vr1. Even when the motor terminal 16 becomes a ground fault, the current flowing through the path between the power supply terminal 18 and the ground terminal 19 becomes a large current, and the current detection value from the upper stage current detection circuit 31 is the first value. Greater than the threshold value Vr1. When the detected current value from the upper stage current detection circuit 31 becomes larger than the first threshold value Vr1, the overcurrent detection signal Sd is output from the short detection circuit 32.

  The overcurrent detection signal Sd from the short detection circuit 32 is sent to the short determination unit 52. When the short determination unit 52 receives the overcurrent detection signal Sd from the short detection circuit 32, the short determination unit 52 determines that it is in a short state and transmits a short detection signal Se to the motor control unit 51. Upon receiving the short detection signal Se from the short determination unit 52, the motor control unit 51 operates the drive circuits 35 and 36 to stop the operation of the motor 10.

  Thus, when the short-circuit resistance is almost 0Ω, the detected current value from the upper stage current detection circuit 31 exceeds the first threshold value Vr1. For this reason, the overcurrent detection signal Sd is output from the short detection circuit 32, thereby detecting a short state.

  However, when there is a certain amount of short-circuit resistance as in the case where the motor 10 has caused a short circuit, the short detection circuit 32 may not be able to detect an overcurrent due to a short circuit. The rare short is a state in which the windings are short-circuited due to melting of the insulating film of the windings.

  That is, when a short circuit having a certain amount of short circuit resistance occurs between the motor terminal 16 and the motor terminal 17 as in the case of a rare short circuit, the current detection value of the lower stage current detection circuit 33 increases. For this reason, the current detection value of the lower stage current detection circuit 33 becomes larger than the target value of the drive current, and the motor control unit 51 controls the pulse width of the switching signal so that the duty ratio decreases. When the duty ratio of the switching signal is lowered, the current flowing through the path from the power supply terminal 18 to the ground terminal 19 decreases. For this reason, the detection current value from the upper stage current detection circuit 31 decreases, and the detection current value from the upper stage current detection circuit 31 does not exceed the first threshold value Vr1. Therefore, a state in which a short cannot be detected by the short detection circuit 32 continues.

  This will be further described with reference to the graph of FIG. FIG. 3 is a graph showing the relationship between the duty ratio of the switching signal and the current detection value from the upper stage current detection circuit 31, the horizontal axis shows the duty ratio of the switching signal, and the vertical axis shows from the upper stage current detection circuit 31. The detected current value is shown. In FIG. 3, a curve A1 is a characteristic under a condition where the current value is maximum, a curve A2 is a characteristic at a standard value, and a curve A3 is a characteristic under a condition where the current value is minimum. The first threshold value Vr1 of the short detection circuit 32 is set to 8A, for example. If the short-circuit resistance is almost 0Ω, the detected current value from the upper-stage current detection circuit 31 at the time of occurrence of a short circuit exceeds the first threshold value Vr1 (for example, 8A).

  However, if there is a certain amount of short-circuit resistance, such as when a rare short occurs, the detected current value from the upper stage current detection circuit 31 may not exceed the first threshold value Vr1 when a short occurs. In this case, since the current detection value of the lower-stage current detection circuit 33 is larger than the target value of the drive current, the pulse width is feedback-controlled, and the duty ratio of the switching signal is 40% or less, for example. When the duty ratio of the switching signal is lowered, the current flowing through the path from the power supply terminal 18 to the ground terminal 19 decreases. For this reason, the detected current value from the upper stage current detection circuit 31 does not exceed the first threshold value Vr1 (for example, 8A), and the short detection circuit 32 continues to be in a state where the occurrence of a short circuit cannot be detected.

  In this way, when there is a certain short-circuit resistance, the duty ratio of the switching signal is lowered, and the current flowing through the path from the power supply terminal 18 to the ground terminal 19 is reduced. Cannot be detected.

  Therefore, in the first embodiment of the present invention, the duty ratio of the switching signal is equal to or less than a specified duty ratio (hereinafter also referred to as a predetermined value), and the current detection value of the upper stage current detection circuit 31 is equal to a reference current value (hereinafter referred to as In this case, it is determined that a short circuit has occurred. That is, when there is a certain amount of short circuit resistance, such as when a rare short circuit occurs, the duty ratio of the switching signal is reduced by the feedback control as described above. In the normal state, by reducing the duty ratio of the switching signal, the current detection value of the upper-stage current detection circuit 31 decreases to a predetermined value or less according to the characteristics shown in FIG. Even if the duty ratio of the switching signal is lowered, the current detection value of the upper stage current detection circuit 31 does not fall below a predetermined value. Therefore, when the duty ratio of the switching signal is a predetermined value (for example, 40%) or less and the current detection value of the upper stage current detection circuit 31 is the second threshold value Vr2 (for example, 5 A) or more, a short circuit has occurred. Can be judged.

  Here, the second threshold value Vr2 can be set based on the graph of FIG. That is, since the second threshold value Vr2 detects an overcurrent that cannot be detected by the short detection circuit 32, the second threshold value Vr2 is lower than the first threshold value Vr1 (for example, 8A). Further, the second threshold value Vr2 needs to be a value larger than the current detection value of the upper stage current detection circuit 31 at the normal time when the duty ratio is equal to or less than a predetermined value. From the graph of FIG. 3, the maximum value of the detected current value at the normal time when the duty ratio is 40% or less is about 2.5A. Therefore, in this example, the second threshold value Vr2 is set to 5A, for example.

  In FIG. 2, the current detection value Sf of the upper stage current detection circuit 31 is digitized by the AD conversion unit 54 and supplied to the short determination unit 52. Further, the duty ratio signal Sg of the switching signal is supplied from the motor control unit 51 to the short determination unit 52. When the duty ratio of the switching signal is equal to or less than a predetermined value (for example, 40%) and the current detection value is equal to or greater than the second threshold value Vr2 (for example, 5A), the short determination unit 52 determines that the short state is present. Then, a short detection signal Se is transmitted to the motor control unit 51. Upon receiving the short detection signal Se from the short determination unit 52, the motor control unit 51 operates the drive circuits 35 and 36 to stop the operation of the motor 10.

  FIG. 4 is a flowchart showing a short detection process in the motor control circuit 1 according to the first embodiment of the present invention.

  In FIG. 4, the short determination unit 52 determines whether or not the overcurrent detection signal Sd from the short detection circuit 32 is received (step S1), and when the overcurrent detection signal Sd is received (step S1: Yes), it determines with it being in a short state, transmits short detection signal Se to motor control part 51 (Step S2), and motor control part 51 stops operation of motor 10 (Step S3).

  When the overcurrent detection signal Sd is not received (step S1: No), the short determination unit 52 determines whether the duty ratio of the switching signal is equal to or less than a predetermined value based on the duty ratio signal Sg from the motor control unit 51. (Step S4), and when the duty ratio is equal to or less than a predetermined value (step S4: Yes), it is determined whether or not the current detection value Sf from the upper stage current detection circuit 31 is equal to or greater than the second threshold value Vr2 (step S4). Step S5). If the duty ratio of the switching signal is not less than the predetermined value (step S4; No), or if the current detection value is not equal to or greater than the second threshold value Vr2 (step S5: No), the short determination unit 52 It determines with having not generate | occur | produced, and returns a process to step S1.

  In step S4, it is determined that the duty ratio of the switching signal is equal to or less than a predetermined value (step S4: Yes), and in step S4, the current detection value from the upper stage current detection circuit 31 is greater than or equal to the second threshold value Vr2. Is determined (step S5: Yes), the short determination unit 52 determines that the short state has occurred, and transmits a short detection signal Se to the motor control unit 51 (step S2). 10 is stopped (step S3).

  As described above, in the first embodiment of the present invention, it is detected that the duty ratio of the switching signal is not more than a predetermined value and the detected current value of the upper stage current detection circuit 31 is not less than the second threshold value Vr2. The occurrence of a short circuit is detected. Thereby, even when there is a certain amount of short-circuit resistance, such as when a rare short occurs, the occurrence of a short can be detected. Further, in the motor control circuit 1 according to the first embodiment of the present invention, there is no short circuit that has a certain short-circuit resistance, such as when a short circuit occurs, without providing a circuit that detects the rotation of the motor. The state can be detected. Further, in the first embodiment of the present invention, it is determined whether or not the duty ratio of the switching signal is equal to or less than a predetermined value, or whether or not the detected current value of the upper stage current detection circuit 31 exceeds the second threshold value Vr2. Since this is performed by the software of the control circuit 30, it is easy to optimize the threshold value.

  In the motor control circuit 1 according to the first embodiment of the present invention, two shunt resistors, the resistor 13 and the resistor 14, are provided in the path between the power supply terminal 18 and the ground terminal 19 to detect short circuit. Current detection for performing and current detection for performing torque control of the motor are performed separately. Therefore, the dynamic range of the current detection value in the upper stage current detection circuit 31 and the dynamic range of the current detection value in the lower stage current detection circuit 33 can be set optimally. In this case, since the lower-stage current detection circuit 33 can be set to detect the current value within the range of the normal current value, the motor current can be accurately detected and the motor torque can be controlled. Furthermore, in the motor control circuit 1 according to the first embodiment of the present invention, between the drain of the MOSFET 12 and the drain of the MOSFET 11, the anode is connected to the drain of the MOSFET 12 and the cathode is connected to the drain of the MOSFET 11. Since the diode 15 is connected, the motor current can be accurately detected during circulation or power generation.

<Second Embodiment>
FIG. 5 is a functional block diagram of the motor control circuit 101 according to the second embodiment of the present invention. In FIG. 5, motor 110, MOSFETs 111 and 112, resistors 113 and 114, diode 115, motor terminals 116 and 117, power supply terminal 118, ground terminal 119, control circuit 130, upper stage current detection circuit 131, short detection circuit 132, lower stage current. The detection circuit 133, the drive circuits 135 and 136, the motor control unit 151, the short determination unit 152, and the AD conversion units 153 and 154 are the motor 10, the MOSFETs 11 and 12, and the resistor 13 in the first embodiment shown in FIG. And 14, diode 15, motor terminals 16 and 17, power supply terminal 18, ground terminal 19, control circuit 30, upper current detection circuit 31, short detection circuit 32, lower current detection circuit 33, drive circuits 35 and 36, motor control unit 51, short determination unit 52, AD conversion units 53 and 54 The same, the description thereof is omitted.

  As shown in FIG. 5, in the motor control circuit 101 according to the second embodiment of the present invention, a timer unit 155 is provided for the short determination unit 152. The timer unit 155 counts the duration of a period in which the duty ratio of the switching signal is equal to or less than a predetermined value and the current detection value from the upper stage current detection circuit 131 is equal to or greater than the second threshold value Vr2. Then, the short determination unit 152 continues a period in which the duty ratio of the switching signal is equal to or less than a predetermined value and the current detection value from the upper stage current detection circuit 131 is equal to or greater than the second threshold value Vr2 for a predetermined time (for example, 100 milliseconds) In such a case, it is determined that a short circuit has occurred, and a short detection signal is transmitted to the motor control unit 151 to stop the operation of the motor 110.

  As described above, in the second embodiment of the present invention, the period during which the duty ratio of the switching signal is equal to or smaller than the predetermined value and the detected current value of the upper stage current detection circuit 31 is equal to or greater than the second threshold value Vr2 is predetermined. Since it is determined that a short circuit has occurred when the time continues, it is possible to prevent erroneous detection of a short circuit due to noise.

A program for realizing all or part of the functions of the motor control circuits 1 and 101 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. The processing of each part may be performed as necessary. Here, the “computer system” includes an OS and hardware such as peripheral devices.
Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” is a program that dynamically holds a program for a short time, like a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the above-described functions, or may be a program that can realize the above-described functions in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1,101 Motor control circuit 10,110 Motor 13,14,113,114 Resistance 15 Diode 18,118 Power supply terminal 19,119 Ground terminal 30,130 Control circuit 31,131 Upper stage current detection circuit 32,132 Short detection circuit 33, 133 Lower-stage current detection circuits 35, 36, 135, and 136 Drive circuits 51 and 151: Motor control units 52 and 152: Short determination units 53 and 154: AD conversion units

Claims (6)

A first switching element provided between the power supply terminal and the motor;
A second switching element provided between a ground terminal and the motor;
A motor control unit that controls a duty ratio of a switching signal that controls on / off of the first and second switching elements according to a detection value of a current flowing through the motor;
If the first is greater than the threshold detection value of the current flowing in the path is predetermined between said power supply terminal and the motor, and a short detection circuit you output an overcurrent detection signal,
A short determination unit that determines that a short state occurs when the overcurrent detection signal is received;
A motor control circuit comprising:
The short determination unit is configured such that a duty ratio of the switching signal is smaller than a specified duty ratio, and a detected value of a current flowing in a path between the power supply terminal and the motor is lower than the first threshold value. A motor control circuit, characterized in that it is determined that a short circuit has occurred when the second threshold value is greater than the second threshold value.   The motor control circuit according to claim 1, wherein the motor control unit stops the operation of the motor when it is determined by the short determination unit that a short circuit has occurred. A first shunt resistor provided in a path between the power supply terminal and the motor;
A second shunt resistor connected between the first shunt resistor and the motor;
The short determination unit determines whether or not the short has occurred using a detection value of a current flowing in a path between the power supply terminal and the motor detected by the first shunt resistor. ,
The motor according to claim 1, wherein the motor control unit controls a duty ratio of the switching signal using a detected value of a current flowing through the motor detected by the second shunt resistor. Control circuit. 4. The motor control circuit according to claim 1, wherein a free-wheeling diode is provided between the drain of the first switching element and the drain of the second switching element. 5. . Further, it measures the time during which the duty ratio of the switching signal is smaller than the specified duty ratio and the detected value of the current flowing in the path between the power supply terminal and the motor is larger than the second threshold value. Having a timer part,
The short determination unit has a duty ratio of the switching signal smaller than the specified duty ratio, and a detected value of a current flowing in a path between the power supply terminal and the motor is larger than the second threshold value. The motor control circuit according to any one of claims 1 to 4, wherein when the time continues for a predetermined time, it is determined that the short circuit has occurred. A first switching element provided between the power supply terminal and the motor, and a second switching element provided between the ground terminal and the motor, and detecting a current flowing through the motor; A short detection method for a motor control circuit for controlling a duty ratio of a switching signal for controlling on / off of the first and second switching elements according to a detection value of a current flowing through the motor,
Detecting a current flowing in a path between the power supply terminal and the motor;
When the detected value of the detected current is larger than a preset first threshold value, or the duty ratio of the switching signal is smaller than a specified duty ratio, and between the power supply terminal and the motor It is determined that a short circuit has occurred in any of the cases where the detected value of the current flowing in the path is larger than the second threshold value set to a value lower than the first threshold value. Control circuit short detection method.

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