JP2004194418A - Controller of electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the damage of a switching element by preventing short circuiting current, and to reduce the cost of the controller of an electric motor. <P>SOLUTION: An FET 8 is switched to a connecting state by inputting a gate voltage GV from a pre-driver 5. This gate voltage GV is output from this pre-driver 5 when a command voltage DV is input from a control unit 4 to the pre-driver 5 via the command voltage line 15 of a positive voltage side. A short circuiting line 40 having a diode 42 provided to supply only current directed from the command voltage line 15 to a motor connecting line 13 is connected between the command voltage line 15 and the motor connecting line 13. When a power supply terminal 1a is short circuited to a reference potential, the command voltage DV is drawn to the reference voltage via the short circuiting line 40. The FET 8 becomes a cut-off state to prevent the short circuiting current from being generated. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric motor control device that controls the operation of an electric motor.
[0002]
[Prior art]
2. Description of the Related Art Electric motors are devices that convert current supplied from a power supply into mechanical rotary motion and output the same, and are widely used from automotive parts such as wiper devices to consumer devices such as OA and AV devices. . Conventionally, a motor controller including a drive circuit, a pre-driver and a control unit has been used for controlling such an electric motor.
[0003]
As a drive circuit for such a motor controller, for example, there is a drive circuit using a so-called full bridge circuit that enables bidirectional driving of an electric motor. A full-bridge circuit is also called an H-bridge circuit. A switching element such as two FETs connected in series between a power supply terminal to which a positive power supply voltage of a power supply is supplied and a ground terminal serving as a reference potential. Are provided in parallel with each other. In this case, each power supply terminal of the electric motor is connected to a connection between FETs in each series circuit. Then, in this full bridge circuit, by switching on the FETs located diagonally to each other, a direct current is supplied to the electric motor from one power supply terminal to the other power supply terminal to cause the electric motor to rotate forward, and By using a different combination of FETs for turning on and off, the electric motor can be supplied with a DC current in the opposite direction to rotate the electric motor in the reverse direction.
[0004]
Switching of these FETs is performed by a pre-driver that operates according to a command from the control unit. That is, the pre-driver outputs the gate voltage to a predetermined FET in synchronization with the command voltage output from the control unit, and the FET supplied with the gate voltage is turned on.
[0005]
In such a motor controller, if for some reason the FET located on the positive voltage side, that is, between the power supply terminal and the electric motor is turned on and the power supply terminal connected to the power supply terminal is short-circuited to the reference potential, Means that a short current, that is, a large current that does not pass through a load, flows through this FET. In some cases, the short-circuit current exceeds the capacity of the FET, and the FET may be damaged.
[0006]
Therefore, for example, in a motor controller disclosed in JP-A-2000-194403 or JP-A-10-020001, a detection circuit for detecting a current or a voltage of a power supply terminal is provided, and a current flowing through the power supply terminal is determined by a predetermined value. When the value becomes equal to or more than the value, the FET is switched to the non-conductive state to avoid the occurrence of the short-circuit current.
[0007]
[Problems to be solved by the invention]
However, since such a detection circuit is constituted by a large number of resistors and elements, the number of components is increased, which hinders a reduction in the cost of the control device for the electric motor.
[0008]
An object of the present invention is to prevent a short circuit current and prevent a switching element from being damaged.
[0009]
Another object of the present invention is to reduce the cost of a control device for an electric motor.
[0010]
[Means for Solving the Problems]
An electric motor control device according to the present invention is an electric motor control device that controls an operation of the electric motor by controlling a current supplied from the power supply to the electric motor, wherein a positive power supply voltage is supplied from the power supply. A positive voltage side switching element that is electrically connected between a power terminal and the electric motor, and that switches the electric motor and the power terminal to a connected state when a switching voltage is supplied; A switching element switching means for outputting a switching voltage to the positive voltage side switching element when a command voltage is input; and a switching element switching means electrically connected to the switching element switching means via a command voltage line. Control means for outputting a command voltage to the switching element switching means; and electrically connecting the positive voltage side switching element to the electric motor. A short-circuit line electrically connected between the motor connection line to be connected and the command voltage line, the short-circuit line including a rectifying element that allows only a current flowing from the command voltage line to the motor connection line, and provided on the command voltage line. A resistance element for limiting a current flowing through the short-circuit line, and when the motor connection line is short-circuited to a reference potential, the command voltage is reduced to the reference potential via the short-circuit line, and the positive voltage is reduced. It is characterized in that the side switching element can be switched to a disconnected state.
[0011]
In the electric motor control device according to the present invention, the electric motor is provided with first and second power supply terminals, and the first power supply terminal is connected via a first motor connection line and a first positive voltage side switching element. And electrically connecting the second power supply terminal to the power supply terminal via a second motor connection line and a second positive voltage side switching element. A first and a second reference potential side switching element are respectively provided between the first and second motor connection lines and a ground terminal serving as a reference potential.
[0012]
In the present invention, a short-circuit line having a rectifying element for flowing only a current flowing from the command voltage line to the motor connection line is provided between the motor connection line and the command voltage line. When short-circuited to the reference potential, the command voltage line is short-circuited to the reference potential via the short-circuit line. Therefore, the command voltage output to the switching element is reduced to the reference potential, and the switching element is switched to the non-connection state by the switching element switching means. Therefore, it is possible to prevent the switching element from being damaged by the short-circuit current. it can.
[0013]
Further, in the present invention, since a short-circuit current can be prevented only by adding a short-circuit line between the motor connection line and the command voltage line, a circuit using a large number of electric elements is unnecessary, and components are not required. By reducing the number of points, the cost of the control device for the electric motor can be reduced.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 1 is an explanatory view schematically showing a motor controller according to an embodiment of the present invention.
[0016]
In FIG. 1, reference numeral 1 denotes an electric motor. The electric motor 1 has a first power supply terminal 1a and a second power supply terminal 1b, and supplies a direct current between the power supply terminals 1a and 1b to rotate a not-shown output shaft. It is a brushed motor. The electric motor 1 is rotatable in both directions, and the direction of rotation of the electric motor 1 can be changed by changing the direction of the DC current supplied to the respective power supply terminals 1a and 1b.
[0017]
A motor controller 2 is connected to the electric motor 1 as a control device for the electric motor in order to control the DC current supplied to the power supply terminals 1a and 1b to control the operation, that is, the rotation of the electric motor 1. . The motor controller 2 has a drive circuit 3, a control unit 4, and a pre-driver 5, and controls the electric motor 1 in accordance with a command from a motor switch (not shown) connected to the control unit 4.
[0018]
The drive circuit 3 has a power supply terminal 6 to which a positive power supply voltage is supplied from a power supply (not shown) and a ground terminal 7 serving as a reference potential. The power supply terminal 6 is applied with a positive power supply voltage Va. Four FETs (Field Effect Transistors) 8, 9, 10, and 11 as switching elements are provided between the terminals 6 and 7, and a full bridge is provided by these FETs 8, 9, 10, and 11. A circuit 12 (H bridge circuit) is formed. The full bridge circuit 12 includes a source terminal 8a connected to the power supply terminal 6 as a first positive voltage side switching element FET8 and a drain terminal 9b connected to the ground terminal 7 as a first reference potential side switching element. A series circuit 12a formed by connecting an FET 9 in series, a FET 10 serving as a second positive voltage side switching element having a source terminal 10a connected to a power supply terminal 6 and a drain terminal 11b connected to a ground terminal 7 similarly. And a series circuit 12b in which an FET 11 as a second reference potential side switching element is connected in series, and these series circuits 12a and 12b are connected in parallel with each other. The connection between the FET 8 and the FET 9 is electrically connected to the first power supply terminal 1a via the first motor connection line 13, and similarly, the connection between the FET 10 and the FET 11 is connected to the second motor connection line. 14, it is electrically connected to the second power supply terminal 1b. Therefore, the power supply terminal 1a is electrically connected to the power supply terminal 6 via the motor connection line 13 and the FET 8, the FET 9 is provided between the motor connection line 13 and the ground terminal 7, and the power supply terminal 1b is The FET 11 is provided between the motor connection line 14 and the ground terminal 7 while being electrically connected to the power supply terminal 6 via the connection line 14 and the FET 10.
[0019]
These FETs 8, 9, 10, 11 are connected when the switching voltage, that is, the gate voltage GV is supplied to the gate terminals 8c, 9c, 10c, 11c, that is, in the connection state, that is, from the source terminals 8a, 9a, 10a, 11a to the drain terminal 8b, When the gate terminals 8c, 9c, 10c, and 11c reach the reference potential, they are disconnected, that is, the source terminals 8a, 9a, 10a, and 11a and the drain terminals 8b and 9b are switched. , 10b and 11b are interrupted. For example, when the gate voltage GV is supplied to the gate terminal 8c of the FET 8, the FET 8 is connected and the power supply terminal 6 and the power supply terminal 1a are switched to the connected state.
[0020]
In the drive circuit 3, the supply of the DC current to the electric motor 1 can be cut off by stopping all of the four FETs 8, 9, 10, and 11 to stop the electric motor 1. Further, by switching the connection between the FET 8 on the positive voltage side of one series circuit 12a and the FET 11 on the reference potential side of the other series circuit 12b, a DC current from the power supply terminal 1a to the power supply terminal 1b is supplied to the electric motor 1. The electric motor 1 can be supplied to rotate the electric motor 1 forward. In addition, by switching the FET 10 on the positive voltage side of the other series circuit 12b and the FET 9 on the reference potential side of the one series circuit 12a to a connected state symmetrically with the forward rotation, the current flows from the power supply terminal 1b to the power supply terminal 1a. A direct current can be supplied to the electric motor 1 to cause the electric motor 1 to rotate in the reverse direction. That is, the rotation of the electric motor 1 can be controlled by controlling the gate voltage GV for these FETs 8, 9, 10, and 11.
[0021]
The control of the gate voltage GV for each of the FETs 8, 9, 10, and 11 is performed by the control unit 4 and the pre-driver 5.
[0022]
The control unit 4 as a control means includes a microprocessor (not shown) that calculates a control signal, that is, a command voltage DV, a ROM (not shown) that stores a control program, an arithmetic expression, map data, and the like, and a ROM that temporarily stores data. It is a so-called microcomputer having a RAM or the like that does not have the same configuration. Two systems of command voltage lines 15 and 16 on the positive voltage side corresponding to FETs 8 and 10 on the positive voltage side, and FETs 9 and 11 on the reference potential side respectively. It is electrically connected to the pre-driver 5 via two reference voltage lines 17 and 18 on the reference potential side. Further, a motor switch (not shown) for instructing the operation of the electric motor 1 is connected to the control unit 4, and in response to a command from the motor switch, an output to a command voltage line of a predetermined system is output to an HI output or LO output. Switch to output.
[0023]
The control unit 4 has a power supply terminal 19 connected to a control system power supply (not shown) and a ground terminal 20 connected to a reference potential. The power supply terminal 19 is supplied with a power supply voltage Vb. In the HI output, the control unit 4 outputs the command voltage DV to the pre-driver 5 by supplying the power voltage Vb at the power terminal 19 to the command voltage line. That is, when the output of the control unit 4 becomes the HI output, the command voltage DV is supplied to the pre-driver 5. On the other hand, for the LO output, the control unit 4 uses the command voltage line as the reference potential. That is, when the output of the control unit 4 becomes the LO output, the command voltage DV is not input to the pre-driver 5.
[0024]
Two resistance elements 21 and 22 are provided in series on the command voltage line 15 on the positive voltage side, and two resistance elements 23 and 24 are provided in series on the command voltage line 16 on the positive voltage side. The resistance elements 21 to 24 limit the current flowing through the command voltage lines 15 and 16 to protect the circuit. Further, current limiting resistors 25 and 26 are provided on the command voltage lines 17 and 18 on the reference potential side, respectively, so that the current flowing through these command voltage lines 17 and 18 is limited to protect the circuit. I have.
[0025]
The command voltage DV output from the control unit 4 is higher than the reference potential but lower than the positive power supply voltage Va generated by the drive system power supply, and the FETs 8, 9, 10, and 11 are connected. The value is lower than the switching gate voltage GV. For this purpose, a pre-driver 5 as switching element switching means is provided between the control unit 4 and the FETs 8, 9, 10, 11 and the command voltage DV output from the control unit 4 by the pre-driver 5 is applied to each of the FETs 8, 9,. The voltage is converted into a switching voltage, ie, a gate voltage GV that can perform the switching operation of the switches 10 and 11.
[0026]
The pre-driver 5 is supplied with a power supply voltage Vc from a drive system power supply (not shown) at a power supply terminal 27, and is connected to a reference potential via a ground terminal 28, so that the pre-driver 5 is operated by the power supply voltage Vc. ing. The pre-driver 5 is composed of two systems of positive voltage side gate voltage lines 30 and 31 connected to the positive voltage side FETs 8 and 10, respectively, and two systems of reference voltage FETs 9 and 11 connected to the reference potential side FETs 9 and 11, respectively. And gate voltage lines 32 and 33 on the potential side. Further, current limiting resistors 34 to 37 are provided in the respective gate voltage lines 30 to 33 to prevent an overcurrent for each of the FETs 8, 9, 10, and 11.
[0027]
The output of the pre-driver 5 is switched between the HI output and the LO output and output. In the HI output, the pre-driver 5 outputs the gate voltage GV by supplying the power supply voltage Vc at the power supply terminal 27 to a predetermined gate voltage line, and the gate voltage GV becomes a voltage signal and becomes a predetermined voltage. It is supplied to the FET. Therefore, the FET is switched to the connection state by setting the output of the pre-driver 5 to the HI output. On the other hand, in the LO output, the predetermined gate voltage line is set to the reference potential via the ground terminal 28, and the gate voltage GV is not output to the FET. Therefore, by setting the output of the pre-driver 5 to the LO output, a predetermined FET can be switched to a non-connection state.
[0028]
The switching between the HI output and the LO output for a predetermined FET in the pre-driver 5 is performed according to a command voltage DV input from the control unit 4. That is, the pre-driver 5 sets the output to the HI output for the system to which the HI output is input from the control unit 4 and sets the output to the LO output for the system to which the LO output is input from the control unit 4. It has become. This operation is performed individually for each system.
[0029]
The motor controller 2 is provided with short-circuit lines 40 and 41 to protect the FETs 8 and 10 on the positive voltage side from short-circuit current.
[0030]
One end of the short-circuit line 40 is electrically connected between the respective resistance elements 21 and 22 of the command voltage line 15 on the positive voltage side, and the other end is electrically connected to the motor connection line 13. The short-circuit line 40 is provided with a diode 42 as a rectifying element. With this diode 42, only a current flowing from the command voltage line 15 to the motor connection line 13 can flow through the short-circuit line 40. ing. That is, when the voltage on the command voltage line 15 is lower than the voltage on the motor connection line 13, no current flows through the short-circuit line 40, and when the voltage on the command voltage line 15 becomes higher than the voltage on the motor connection line 13, An electric current flows through the device. Similarly, one end of the short-circuit line 41 is electrically connected between the respective resistance elements 23 and 24 of the command voltage line 16 on the positive voltage side, and the other end is electrically connected to the motor connection line 14. I have. The short-circuit line 41 is provided with a diode 43 as a rectifying element. With this diode 43, only a current flowing from the command voltage line 16 to the motor connection line 14 can flow through the short-circuit line 41. ing. That is, when the voltage on the command voltage line 16 is lower than the voltage on the motor connection line 14, no current flows through the short-circuit line 41, and when the voltage on the command voltage line 16 becomes higher than the voltage on the motor connection line 14, An electric current flows through the device.
[0031]
Next, control of the electric motor 1 by the motor controller 2 will be described.
[0032]
When a motor switch (not shown) is turned off and a command to stop the electric motor 1 is input to the control unit 4, the output of the control unit 4 for each system is LO output. Therefore, the output of the pre-driver 5 to each of the FETs 8, 9, 10, and 11 is an LO output, and the FETs 8, 9, 10, and 11 are maintained in a disconnected state. That is, when a motor switch (not shown) is turned off, the FETs 8, 9, 10, 11 are disconnected, so that the power supply terminals 1a, 1b are disconnected from the power supply terminal 6 and the ground terminal 7, and the electric motor 1 means that the current is not supplied and the stopped state is maintained. At this time, since the output of the control unit 4 is the LO output, no voltage is generated on the command voltage lines 15 and 16 on each positive voltage side, and the voltage is also applied to the power supply terminals 1a and 1b, that is, the motor connection lines 13 and 14. Since no voltage is applied, no current flows through the short-circuit lines 40 and 41.
[0033]
Next, from this state, when a motor switch (not shown) is turned on to the normal rotation side and a command to rotate the electric motor 1 in the normal rotation direction is input to the control unit 4, one of the positive voltage The output for the command voltage line 15 and the command voltage line 18 on one reference potential side is an HI output, and the output for the command voltage line 16 on the other positive voltage side and the command voltage line 17 on the other reference potential side are LO. Output. Accordingly, the output of the pre-driver 5 to the one positive voltage side FET 8 and one reference potential side FET 11 is an HI output, and the other positive voltage side FET 10 and the other reference potential side FET 9 is an LO output. . As a result, the FET 8 and the FET 11 are switched to the connected state by supplying the gate voltage GV to the gate terminals 8c and 11c, and the FET 9 and the FET 10 are disconnected from each other by setting the gate terminals 9c and 10c to the reference potential. Will be maintained as it is. Therefore, the power supply terminal 1a is connected to the power supply terminal 6 via the FET 8, and the power supply terminal 1b is connected to the ground terminal 7 via the FET 11, so that the electric motor 1 is connected from the power supply terminal 1a to the power supply terminal 1b. , And the electric motor 1 rotates forward.
[0034]
At this time, since the command voltage line 15 on the positive voltage side is HI output, the command voltage DV, that is, the power supply voltage Vb is applied, whereas the positive power supply voltage Va of the power supply terminal 6 is applied to the motor connection line 13. Therefore, the voltage on the motor connection line 13 becomes higher than the voltage on the command voltage line 15 and no current flows through the short-circuit line 40. The command voltage line 16 on the positive voltage side has the LO output and therefore has the reference potential, and the motor connection line 14 is connected to the ground terminal 7 and has the reference potential. No current flows.
[0035]
Next, from this state, when a motor switch (not shown) is turned on to the reverse rotation side and a command to rotate the electric motor 1 in the reverse direction is input to the control unit 4, a command on one positive voltage side of the control unit 4 is issued. The output to the voltage line 15 and the command voltage line 18 on one reference potential side is LO output, and the output to the command voltage line 16 on the other positive voltage side and the command voltage line 17 on the other reference potential side is HI output. Is done. Therefore, the output to the one positive voltage side FET 8 and one reference potential side FET 11 of the pre-driver 5 is LO output, and the other positive voltage side FET 10 and the other reference potential side FET 9 output is HI output. . As a result, the gate terminals 8c and 11c of the FET 8 and the FET 11 are maintained in a non-connected state with the reference potential, and the FET 9 and the FET 10 are connected by the supply of the gate voltage GV to the gate terminals 9c and 10c. Will be able to switch. Therefore, the power supply terminal 1b is connected to the power supply terminal 6 via the FET 10, and the power supply terminal 1a is connected to the ground terminal 7 via the FET 9. Thus, the electric motor 1 is connected from the power supply terminal 1b to the power supply terminal 1a. And the electric motor 1 rotates in the reverse direction.
[0036]
At this time, since the command voltage line 16 on the positive voltage side has the HI output, the command voltage DV, that is, the power supply voltage Vb is applied, while the positive power supply voltage Va of the power supply terminal 6 is applied to the motor connection line 14. Therefore, the voltage on the motor connection line 14 becomes higher than the voltage on the command voltage line 16 and no current flows through the short-circuit line 41. Further, the command voltage line 15 on the positive voltage side has the LO output and thus has the reference potential, and the motor connection line 13 is connected to the ground terminal 7 and has the reference potential. No current flows.
[0037]
In the motor controller 2, when the output to the command voltage line 15 on the positive voltage side and the output to the command voltage line 18 on the reference potential side become HI outputs and the electric motor 1 is driven in the forward rotation direction, there is some cause. Accordingly, when the power supply terminal 1a is short-circuited to the reference potential as shown by the dashed line in the figure, the connected FET 8 on the positive voltage side is switched to the non-connection state to prevent short-circuit current. ing. Hereinafter, the operation of preventing short-circuit current of the motor controller 2 will be described.
[0038]
When the power supply terminal 1a is short-circuited to the reference potential, the potential of the motor connection line 13 is reduced to the reference potential. Therefore, the command voltage DV on the command voltage line 15 on the positive voltage side that has become the HI output is higher than the voltage on the motor connection line 13 that has become the reference potential, that is, the reference voltage. A current flowing to the motor connection line 13 flows. The current flowing through the short-circuit line 40 is limited to a predetermined value by the resistance element 21 so as to protect the diode 42 by preventing an overcurrent.
[0039]
As a result, the command voltage line 15 on the positive voltage side is short-circuited to the reference potential via the short-circuit line 42, the motor connection line 13, and the power supply terminal 1a, and the command voltage DV on the command voltage line 15 on the positive voltage side. Is also lowered to the reference potential. Therefore, the reference potential, that is, the LO output is input to the pre-driver 5 via the command voltage line 15 on the positive voltage side, and the pre-driver 5 switches the output for the FET 8 from the HI output to the LO output. Become. Therefore, the FET 8 on the positive voltage side is switched from the connected state to the disconnected state, and cuts off the power supply terminal 6 and the power supply terminal 1a. That is, when the power supply terminal 1a is short-circuited to the reference potential, the FET 8 on the positive voltage side is switched to a non-connected state to cut off the power supply terminal 6 and the power supply terminal 1a, thereby preventing the occurrence of a short-circuit current. Will be.
[0040]
Thus, in the motor controller 2 of the present invention, when the FET 8 on the positive voltage side is in the connected state and the DC current is supplied from the power supply terminal 6 to the power supply terminal 1a, the power supply terminal 1a In this case, the command voltage line 15 on the positive voltage side is short-circuited to the reference potential via the short-circuit line 40, so that the input to the pre-driver 5 via the command voltage line 15 on the positive voltage side is LO. Since the output becomes an output, the FET 8 is switched to the non-connection state, thereby preventing the occurrence of a short-circuit current and preventing the FET 8 from being damaged.
[0041]
Further, since the short-circuit current can be prevented only by providing the short-circuit line 40 between the command voltage line 15 on the positive voltage side and the motor connection line 13, the motor controller 2 having the function of protecting the FET 8 from the short-circuit current can be prevented. Cost can be reduced.
[0042]
Similarly, when the output of the control unit 4 to the command voltage line 16 on the positive voltage side and the output to the command voltage line 17 on the reference potential side become HI outputs and the electric motor 1 is driven in the reverse direction, power is supplied. When the terminal 1b is short-circuited to the reference potential, the command voltage line 16 on the positive voltage side is short-circuited to the reference potential via the short-circuit line 41, the motor connection line 14, and the power supply terminal 1b. The command voltage DV on the command voltage line 16 on the side is also reduced to the reference potential. Therefore, the reference potential, that is, the LO output is input to the pre-driver 5 via the command voltage line 16 on the positive voltage side, and the pre-driver 5 switches the output to the FET 10 from the HI output to the LO output. Become. Therefore, the FET 10 on the positive voltage side is switched from the connected state to the disconnected state, and cuts off the power supply terminal 6 and the power supply terminal 1b. In other words, when the power supply terminal 1b is short-circuited to the reference potential, the FET 10 on the positive voltage side is switched to a non-connected state to cut off the power supply terminal 6 and the power supply terminal 1b, thereby preventing the occurrence of a short-circuit current. Will be.
[0043]
In the present embodiment, the operation for preventing short-circuit current is performed when the power supply terminal 1a or 1b is short-circuited to the reference potential, that is, when the motor connection line 13 or the motor connection line 14 is connected to the power supply terminal 1a or 1b. However, the present invention is not limited to this case. If the electric motor 1 is short-circuited between the electric motor 1 and the FETs 8 and 10 on the positive voltage side, for example, the motor connection lines 13 and 14 may be connected. The same operation is performed even when the signal is directly short-circuited to the reference potential.
[0044]
The present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the scope of the invention. For example, in the above-described embodiment, the drive circuit 3 is a full bridge circuit which is a bidirectional drive circuit, but is not limited to this, and a switching element is provided between the electric motor 1 and the power supply terminal 6. Other driving circuits, such as a unidirectional driving circuit and a half-bridge circuit, may be used as long as they are available.
[0045]
Further, in the above-described embodiment, the electric motor 1 is a DC brush motor having two power supply terminals 1a and 1b. However, the present invention is not limited to this, and a multi-phase brushless motor having two or more power supply terminals. It may be. In this case, the short-circuit line is electrically connected between the switching element provided between the power supply terminal and the power supply terminal and the power supply terminal, and between the switching signal line that outputs a switching signal to the switching element. Will be done.
[0046]
Further, in the above-described embodiment, the switching element is an FET. However, the switching element is not limited to this. Other switching elements may be used as long as they can be switched to the connection state.
[0047]
【The invention's effect】
According to the present invention, when the motor connection line is short-circuited to the reference potential for some reason, the command voltage is reduced to the reference potential by short-circuiting the command voltage line to the reference potential via the short-circuit line. The switching element is switched to the non-connection state by the switching element switching means, thereby preventing the short-circuit current from damaging the switching element.
[0048]
Further, according to the present invention, a short-circuit current can be prevented only by adding a short-circuit line between the motor connection line and the command voltage line, so that a circuit using a large number of electric elements becomes unnecessary, and the number of parts is reduced. And the cost of the control device for the electric motor can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing a motor controller according to an embodiment of the present invention.
[Explanation of symbols]
1 Electric motor
1a First power supply terminal
1b Second power supply terminal
2 Motor controller
3 Drive circuit
4 Control unit
5 Pre-driver
6 Power supply terminal
7 Ground terminal
8,9,10,11 FET
8a, 9a, 10a, 11a Source terminal
8b, 9b, 10b, 11b Drain terminal
8c, 9c, 10c, 11c Gate terminal
12 Full bridge circuit
12a, 12b Series circuit
13 First motor connection line
14 Second motor connection line
15, 16 Positive voltage side command voltage line
17, 18 Reference voltage line on the reference potential side
19 Power supply terminal
20 Ground terminal
21-24 resistance element
25, 26 Current limiting resistor
27 Power supply terminal
28 Ground terminal
30, 31 Gate voltage line on positive voltage side
32,33 Gate voltage line on the reference potential side
34-37 Current limiting resistor
40, 41 Short-circuit wire
42 diode
43 diode
Va Positive power supply voltage
GV gate voltage
DV command voltage
Vb power supply voltage
Vc power supply voltage

Claims (2)

An electric motor control device that controls an operation of the electric motor by controlling a current supplied from the power supply to the electric motor,
A positive voltage side electrically connected between a power supply terminal to which a positive power supply voltage is supplied from the power supply and the electric motor, and switching the electric motor and the power supply terminal to a connected state when a switching voltage is supplied. A switching element;
A switching element switching unit that is electrically connected to the positive voltage side switching element and outputs a switching voltage to the positive voltage side switching element when a command voltage is input;
Control means electrically connected to the switching element switching means via a command voltage line, and outputting a command voltage to the switching element switching means;
A rectifier that is electrically connected between a motor connection line that electrically connects the positive voltage side switching element to the electric motor and the command voltage line, and that allows only a current flowing from the command voltage line to the motor connection line. A short-circuit wire with an element;
A resistance element provided on the command voltage line, for limiting a current flowing through the short-circuit line,
When the motor connection line is short-circuited to a reference potential, the command voltage is reduced to the reference potential via the short-circuit line, and the positive voltage side switching element is switched to a non-connection state. Control device. The control device for an electric motor according to claim 1, wherein the electric motor is provided with first and second power supply terminals, and the first power supply terminal is connected to a first motor connection line and a first positive voltage side switching. And electrically connecting the second power supply terminal to the power supply terminal via a second motor connection line and a second positive voltage side switching element. An electric motor control device, wherein first and second reference potential side switching elements are provided between the first and second motor connection lines and a ground terminal serving as a reference potential, respectively.

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