Motor drive unit

Abstract

The motor brake is quickly activated in the event of a power outage. [Solution] The motor drive device comprises an inverter circuit that generates a multi-phase motor drive signal for driving a motor by switching a switching element; a relay switch unit that can short-circuit all phase signal lines of the multi-phase motor drive signal by a relay switch; an inverter drive circuit that generates an inverter drive signal for driving the switching of the switching element from a DC power supply; a relay drive circuit that outputs a short-circuit instruction to short-circuit the all phase signal lines by the relay switch unit when the motor brake is activated; and a backup power supply circuit that, in the event that the power supply from the DC power supply stops, uses a backup power supply that maintains a predetermined voltage for at least the period from the short-circuit instruction until the relay switch unit short-circuits the all phase signal lines to short-circuit the all phase signal lines by the switching element.

Description

Technical Field

[0001] The present invention relates to a motor drive device.

Background Art

[0002] In recent years, a motor drive device is known in which drive signal lines of each phase of a motor such as a brushless motor are short-circuited between phases by a relay switch to apply dynamic braking to the motor (see, for example, Patent Document 1). In such a conventional motor drive device, further, a technique is known in which, during a period until the relay switch becomes conductive, the drive signal lines of each phase are short-circuited using switching elements of an inverter circuit to shorten the period until dynamic braking is applied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, for example, in applications used in in-vehicle products, since power is supplied from a battery, in the above-described conventional motor drive device, during a power failure when power supply from the battery stops, it is impossible to short-circuit between phases of the drive signal lines by the switching elements of the inverter circuit, and there is a possibility that dynamic braking cannot be quickly activated.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a motor drive device that can quickly activate the brake of a motor even when the power supply stops.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the present invention is a motor drive device comprising: an inverter circuit that generates a multi-phase motor drive signal for driving a motor by switching a switching element; a relay switch unit that can short-circuit all-phase signal lines of the multi-phase motor drive signal by a relay switch; an inverter drive circuit that generates an inverter drive signal for driving the switching of the switching element in the inverter circuit from power supplied from a DC power supply; a relay drive circuit that outputs a short-circuit instruction to short-circuit the all-phase signal lines by the relay switch unit when the brake of the motor is activated; and a backup power supply circuit that charges power supplied from the DC power supply and, when the power supply from the DC power supply stops, uses a backup power supply that maintains a predetermined voltage for at least the period from the short-circuit instruction until the relay switch unit short-circuits the all-phase signal lines to short-circuit the all-phase signal lines by the switching element.

[0007] Furthermore, in one aspect of the present invention, the motor drive device described above, the backup power supply circuit may include a power storage device that charges power supplied from the DC power supply, and a reverse current prevention element that prevents reverse current of the power supplied from the DC power supply, and the backup power supply that maintains the predetermined voltage capable of driving the switching element for at least the period, and a short-circuit drive circuit that uses the backup power supply to output a short-circuit drive signal that short-circuits the all-phase signal lines by the switching element when the power supply from the DC power supply stops or when a fault requiring the motor to brake is detected.

[0008] Furthermore, in one aspect of the present invention, the motor drive device described above may be a capacitor.

[0009] Furthermore, in one aspect of the present invention, the reverse current prevention element in the motor drive device described above may be a diode.

[0010] Furthermore, in one aspect of the present invention, the motor drive device described above includes a control unit that controls the inverter drive circuit and the relay drive circuit, and the control unit may stop the control of the switching element by the inverter drive circuit when the voltage of the DC power supply falls below a threshold or when it detects a fault requiring the motor to brake, output the short-circuit instruction to the relay drive circuit, and short-circuit the all-phase signal line by the switching element in the short-circuit drive circuit.

[0011] Furthermore, in one aspect of the present invention, in the motor drive device described above, the inverter circuit is provided with multiple sets of first and second switching elements connected in series between a first power line on the high potential side that supplies drive power to the motor and a second power line on the low potential side that is lower than the potential of the first power line, and the backup power circuit may short-circuit all the phase signal lines by making all of the second switching elements connected to the second power line conductive.

[0012] Furthermore, in one aspect of the present invention, the relay switch in the motor drive device described above may be a normally closed switch that becomes conductive when the power supply from the DC power source is stopped.

[0013] Furthermore, in one aspect of the present invention, the motor in the motor drive device described above may be a three-phase brushless motor. [Effects of the Invention]

[0014] According to the present invention, when the power supply from the DC power source is interrupted, the backup power supply circuit uses a backup power supply that maintains a predetermined voltage from the time of the short-circuit instruction that short-circuits all phase signal lines of at least multiple phases of motor drive signals until the relay switch unit short-circuits all phase signal lines, and short-circuits all phase signal lines using the switching elements of the inverter circuit. As a result, the motor drive device can quickly activate the motor brake even when the power supply is interrupted. [Brief explanation of the drawing]

[0015] [Figure 1] A block diagram showing an example of a motor drive device according to this embodiment. [Figure 2] This is a circuit diagram illustrating an example of a short-circuit drive circuit in this embodiment. [Figure 3] This flowchart shows an example of the operation of the motor drive device according to this embodiment. [Figure 4] This is a timing chart showing an example of the operation of the motor drive device according to this embodiment. [Figure 5] This is a timing chart showing an example of the operation of a conventional motor drive system. [Modes for carrying out the invention]

[0016] A motor drive device according to one embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a block diagram showing an example of a motor drive device 1 according to this embodiment.

[0017] As shown in Figure 1, the motor drive unit 1 comprises an inverter circuit 2, an inverter drive circuit 11, a relay drive circuit 12, a control unit 13, a backup power supply circuit 14, and a relay switch unit 30. The motor drive unit 1 is a drive unit that drives a motor 3, for example, in an electric vehicle.

[0018] Motor 3 is, for example, a three-phase brushless motor and is driven by three-phase (U-phase, V-phase, W-phase) motor drive signals (SU, SV, SW) output by inverter circuit 2.

[0019] The inverter circuit 2 generates motor drive signals (SU, SV, SW) of a plurality of phases (for example, three phases) for driving the motor 3 by switching the switching elements 20 (211 to 213, 221 to 223) described later. The inverter circuit 2 includes switching elements (211 to 213, 221 to 223) and shunt resistors (23 to 25). Note that the inverter circuit 2 is disposed between a first voltage power source for driving the motor 3 (for example, the same voltage as the battery power source VBAT) and the ground line via the switch SW1.

[0020] In this embodiment, each of the switching elements 211 to 213 has the same configuration and corresponds to the high-side (high potential side) switching element 21 (first switching element) in the inverter circuit 2. Each of the switching elements 211 to 213 is described as the high-side switching element 21 (first switching element) when indicating any high-side switching element included in the inverter circuit 2 or when not particularly specified.

[0021] Also, each of the switching elements 221 to 223 has the same configuration and corresponds to the low-side (low potential side) switching element 22 (second switching element) in the inverter circuit 2. Each of the switching elements 221 to 223 is described as the low-side switching element 22 (second switching element) when indicating any low-side switching element included in the inverter circuit 2 or when not particularly specified.

[0022] Also, each of the high-side switching element 21 and the low-side switching element 22 is described as the switching element 20 when indicating any switching element included in the inverter circuit 2 or when not particularly specified.

[0023] The inverter circuit 2 is equipped with three sets of high-side switching elements 21 and low-side switching elements 22 connected in series between a high-potential (high-side) power line L1 (first power line) that supplies drive power to the motor 3 and a low-potential (low-side) power line L2 (second power line) that is lower in potential than power line L1, for each phase (an example of multiple phases).

[0024] The switching elements 20 (211-213, 221-223) are semiconductor switches such as NMOS (N-channel Metal-Oxide Semiconductor) transistors and IGBTs (Insulated Gate Bipolar Transistors).

[0025] Switching element 211 and switching element 221 are connected in series between power line L1 and power line L2 (ground line), and a U-phase motor drive signal SU is output from node N1, which is the midpoint between switching element 211 and switching element 221.

[0026] Furthermore, switching elements 212 and 222 are connected in series between power line L1 and power line L2 (ground line), and a V-phase motor drive signal SV is output from node N2, which is the midpoint between switching elements 212 and 222.

[0027] Furthermore, switching element 213 and switching element 223 are connected in series between power line L1 and power line L2 (ground line), and a W-phase motor drive signal SW is output from node N2, which is the midpoint between switching element 213 and switching element 223.

[0028] Furthermore, power line L1 is connected to a first voltage power supply (for example, the same voltage as the battery power supply VBAT) for driving motor 3. The high-side switching elements 21 (211-213) are connected to the power line L1 (first power line) of the first voltage power supply (VBAT) that supplies power to the motor 3, and the low-side switching elements 22 (221-223) are connected to the power line L2 (second power line) of the low-potential power supply (ground).

[0029] The shunt resistor 23 detects the current flowing through the U-phase switching element 20 (switching element 211 and switching element 221). The shunt resistor 23 is connected between the switching element 221 and the power line L2 (ground line).

[0030] Furthermore, the shunt resistor 24 detects the current flowing through the V-phase switching elements 20 (switching elements 212 and 222). The shunt resistor 24 is connected between the switching element 222 and the power line L2 (ground line).

[0031] Furthermore, the shunt resistor 25 detects the current flowing through the W-phase switching element 20 (switching element 213 and switching element 223). The shunt resistor 25 is connected between the switching element 223 and the power line L2 (ground line).

[0032] The relay switch unit 30 can short-circuit all phase signal lines (nodes N1 to N3) of the three-phase (an example of multiple phases) motor drive signal (SU, SV, SW) using relay switches (31, 32). The relay switch unit 30 short-circuits all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW) in response to a short-circuit instruction output by the relay drive circuit 12, which will be described later. The relay switch unit 30 includes relay switch 31 and relay switch 32.

[0033] Relay switches 31 and 32 are normally closed switches that become conductive (on) when the power supply from the battery power supply VBAT (second voltage power supply) is stopped, or when a fault requiring brake control of motor 3 is detected. The relay switch 31 can short-circuit the signal line (node ​​N1) for the U-phase motor drive signal SU and the signal line (node ​​N2) for the V-phase motor drive signal SV in response to a short-circuit instruction.

[0034] Furthermore, the relay switch 32 can short-circuit the signal line (node ​​N2) for the V-phase motor drive signal SV and the signal line (node ​​N3) for the W-phase motor drive signal SW in response to a short-circuit instruction. Note that the battery power supply VBAT (an example of a DC power supply) is a power supply provided by a battery, such as a Li-ion (lithium-ion) battery. In this embodiment, an example is described in which the battery power supply VBAT (second voltage power supply) and the first voltage power supply for driving the motor 3 are the same voltage, but the first voltage power supply and the second voltage power supply may be different voltages.

[0035] The inverter drive circuit 11 generates inverter drive signals (DS1 to DS6) that drive the switching of the switching elements 20 of the inverter circuit 2 from power supplied from the battery power supply VBAT. Based on the control signals (S1 to S6) from the control unit 13, the inverter drive circuit 11 outputs inverter drive signals (DS1 to DS6) that drive the switching of the switching elements (211 to 213, 221 to 223) to the inverter circuit 2.

[0036] When the relay drive circuit 12 activates the brake of the motor 3, the relay switch unit 30 outputs a short-circuit instruction that short-circuits all phase signal lines (nodes N1 to N3). When the motor 3 is not in the brake state and is in a normal control state, the relay drive circuit 12 outputs a high state to the short-circuit instruction signal line, for example, and outputs a low state as a short-circuit instruction due to control by the control unit 13 or power failure of the battery power supply VBAT.

[0037] The backup power supply circuit 14 charges power supplied from the battery power supply VBAT, and in the event of a power outage (power failure), uses the backup power supply 40 to short-circuit all phase signal lines (nodes N1 to N3) using the switching element 20. The backup power supply circuit 14 comprises the backup power supply 40 and the short-circuit drive circuit 50.

[0038] The backup power supply 40 is a power supply that maintains a predetermined voltage for at least the period from the short-circuit instruction of the relay drive circuit 12 until the relay switch unit 30 short-circuits all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW). Here, the predetermined voltage is, for example, a voltage that can drive the switching element 20 to the ON state. The backup power supply 40 includes a capacitor 42 (energy storage device) that charges the power supplied from the battery power supply VBAT, and a diode 41 (reverse current prevention element) that prevents reverse current of the power supplied from the battery power supply VBAT.

[0039] Diode 41 (an example of a reverse current prevention element) has its anode terminal connected to the battery power supply VBAT and its cathode terminal connected to node N4. Diode 41 prevents reverse current of the charging voltage of capacitor 42 in the event of a power failure of the battery power supply VBAT.

[0040] Capacitor 42 (an example of an energy storage device) is placed between node N4 and the ground line and charges with power supplied from the battery power supply VBAT. The power charged in capacitor 42 is also used as driving power for a switching element 20 that short-circuits all phase signal lines (nodes N1 to N3) of the motor drive signals (SU, SV, SW) in the event of a power failure of the battery power supply VBAT.

[0041] The short-circuit drive circuit 50 outputs a short-circuit drive signal using the backup power supply 40 and the switching element 20 to short-circuit all phase signal lines (nodes N1 to N3) of the motor drive signals (SU, SV, SW) when the power supply from the battery power supply VBAT stops or when a fault requiring brake control of the motor 3 is detected. The short-circuit drive circuit 50 outputs a short-circuit drive signal to the inverter circuit 2 when the battery power supply VBAT fails to supply power or when the control unit 13 requests a short-circuit to short-circuit all phase signal lines (nodes N1 to N3). The detailed configuration of the short-circuit drive circuit 50 will be described later with reference to Figure 2.

[0042] The control unit 13 is, for example, a microcontroller including a CPU (Central Processing Unit), and comprehensively controls the motor drive device 1. The control unit 13 controls the inverter circuit 2 via the inverter drive circuit 11 to output motor drive signals (SU, SV, SW), and controls the drive of the motor 3.

[0043] Furthermore, the control unit 13 uses the relay drive circuit 12 and the backup power supply circuit 14 to control the motor 3 into a braking state. The control unit 13 controls the relay drive circuit 12 and the backup power supply circuit 14 to short-circuit all phase signal lines (nodes N1 to N3) of the motor drive signals (SU, SV, SW).

[0044] Furthermore, when the voltage of the battery power supply VBAT falls below a threshold (below threshold Vth), the control unit 13 stops the control of the switching element 20 by the inverter drive circuit 11, outputs a short-circuit instruction to the relay drive circuit 12, and short-circuits all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW) by the switching element 20 to the short-circuit drive circuit. Here, the threshold Vth is, for example, lower than the minimum rated voltage of the battery power supply VBAT and is a voltage at which the control unit 13 can operate.

[0045] Next, with reference to Figure 2, the detailed configuration of the short-circuit drive circuit 50 described above will be explained. Figure 2 is a circuit diagram illustrating an example of a short-circuit drive circuit 50 in this embodiment.

[0046] As shown in Figure 2, the short-circuit drive circuit 50 includes a resistor 51, a resistor 52, an NPN transistor 53, resistors 54 to 56, an NMOS transistor 57, a resistor 58, a resistor 59, and a PMOS transistor 60.

[0047] The resistor 51 is placed between the signal line of the control signal S7 of the control unit 13 and node N5, and generates the base current of the NPN transistor 53. In addition, the resistor 51 keeps node N5 in a high state when the control signal S7 is in a high state.

[0048] Resistor 52 is placed between node N5 and the ground line and functions as a pull-down resistor to keep node N5 in a low state when the control signal S7 is low or the battery power supply VBAT is lost power.

[0049] The NPN transistor 53 is an NPN bipolar transistor, with its collector terminal connected to node N6, its base terminal to node N5, and its emitter terminal to the ground line. The NPN transistor 53 is ON (conducting) when the control signal S7 is high, and OFF (non-conducting) when the control signal S7 is low or when the battery power supply VBAT is lost.

[0050] Resistor 54 is connected between node N4, which is the output terminal of the backup power supply voltage of the backup power supply 40, and node N6, and functions as a pull-up resistor for the backup power supply voltage. Resistor 54 holds node N6 at the backup power supply voltage of the backup power supply 40 when the NPN transistor 53 is in the off state.

[0051] Resistor 55 is placed between nodes N6 and N7. Resistor 56 is placed between node N7 and the ground line. Resistors 55 and 56 function as voltage divider resistors, and the resistance ratio of resistors 55 and 56 generates the drive voltage for the NMOS transistor described later from the backup power supply voltage of the backup power supply 40.

[0052] The NMOS transistor 57 is an N-channel MOS transistor, with its drain terminal connected to node N9, its gate terminal to node N7, and its source terminal to the ground signal line. The NMOS transistor 57 is turned off when node N7 is low while the NPN transistor 53 is ON. Conversely, the NMOS transistor 57 is turned on when node N7 is high while the NPN transistor 53 is OFF.

[0053] Resistor 58 is placed between node N4, which is the output terminal of the backup power supply voltage of the backup power supply 40, and node N9, and functions as a pull-up resistor for the backup power supply voltage. Resistor 58 holds node N9 at the backup power supply voltage of the backup power supply 40 when the NMOS transistor 57 is in the off state.

[0054] Resistor 59 is placed between node N8, which is the drain terminal of the NMOS transistor 57, and node N9, and limits the current flowing through the NMOS transistor 57. The resistance value of resistor 59 is adjusted so that when the NMOS transistor 57 is ON, node N9 is low, and when the NMOS transistor 57 is ON, node N9 is high.

[0055] The PMOS transistor 60 is a P-channel MOS transistor, with its drain terminal connected to node N10, its gate terminal to node N9, and its source terminal to node N4, which is the output terminal for the backup power supply voltage of the backup power supply 40. The PMOS transistor 60 is off when node N9 is high. Conversely, the PMOS transistor 60 is on when node N9 is low, and outputs the backup power supply voltage of the backup power supply 40 to node N10.

[0056] Node N10, which is the output terminal of the short-circuit drive circuit 50, is connected to the gate terminal (control terminal) of the switching element 221 via resistor 61 and diode 62. Similarly, node N10 is connected to the gate terminal (control terminal) of the switching element 222 via resistor 63 and diode 64, and also to the gate terminal (control terminal) of the switching element 223 via resistor 65 and diode 66.

[0057] When the PMOS transistor 60 is turned on and the backup power supply voltage of the backup power supply 40 is supplied to node N10, the low-side switching elements 22 (221~223) are turned on, short-circuiting all phase signal lines (nodes N1~N3) of the motor drive signals (SU, SV, SW).

[0058] Resistor 61 limits the current flowing from node N10 to the gate terminal of the switching element 221. Diode 62 is connected in series with resistor 61, with its anode terminal connected to one end of resistor 61 and its cathode terminal connected to the gate terminal of the switching element 221, so that the current flows forward from node N10 to the gate terminal of the switching element 221. Diode 62 prevents current from flowing back from the gate terminal of the switching element 221 to the short-circuit drive circuit 50.

[0059] Furthermore, resistor 63 limits the current flowing from node N10 to the gate terminal of switching element 222. Diode 64 is connected in series with resistor 63, with its anode terminal connected to one end of resistor 63 and its cathode terminal connected to the gate terminal of switching element 222, so that the current flows forward from node N10 to the gate terminal of switching element 222. Diode 64 prevents current from flowing back from the gate terminal of switching element 222 to the short-circuit drive circuit 50.

[0060] Furthermore, resistor 65 limits the current flowing from node N10 to the gate terminal of switching element 223. Diode 66 is connected in series with resistor 65, with its anode terminal connected to one end of resistor 65 and its cathode terminal connected to the gate terminal of switching element 223, so that the current flows forward from node N10 to the gate terminal of switching element 223. Diode 66 prevents current from flowing back from the gate terminal of switching element 223 to the short-circuit drive circuit 50.

[0061] When the inverter circuit 2 is normally controlled by the inverter drive circuit 11, the inverter drive circuit 11 outputs inverter drive signals DS1 to DS6 in accordance with the control signals S1 to S6 output from the control unit 13.

[0062] The signal line for inverter drive signal DS1 is connected to the gate terminal of switching element 211. The signal line for inverter drive signal DS2 is connected to the gate terminal of switching element 212. The signal line for inverter drive signal DS3 is connected to the gate terminal of switching element 213.

[0063] Furthermore, the signal line for the inverter drive signal DS4 is connected to the gate terminal of the switching element 221 and the cathode terminal of the diode 62. The signal line for the inverter drive signal DS5 is connected to the gate terminal of the switching element 222 and the cathode terminal of the diode 64. The signal line for the inverter drive signal DS6 is connected to the gate terminal of the switching element 223 and the cathode terminal of the diode 66.

[0064] Next, the operation of the motor drive device 1 according to this embodiment will be described with reference to the drawings. First, with reference to Figure 2, the operation of the short-circuit drive circuit 50 of the backup power supply circuit 14 will be explained.

[0065] In the short-circuit drive circuit 50 shown in Figure 2, under normal operating conditions when power is supplied normally from the battery power supply VBAT, the control unit 13 sets the control signal S7 to high, causing node N5 to go high and NPN transistor 53 to turn on. Next, as NPN transistor 53 turns on, node N7 goes low and NMOS transistor 57 turns off.

[0066] Next, when the NMOS transistor 57 turns off, node N9 goes high, and the PMOS transistor 60 turns off. As a result, the short-circuit drive circuit 50 is not affected by the operation of the low-side switching element 22 of the inverter circuit 2 during normal operation.

[0067] Furthermore, in the short-circuit drive circuit 50, if a power supply loss occurs, such as when the battery is disconnected and power is not supplied from the battery power supply VBAT, the operation of the control unit 13 stops and the voltage of the control signal S7 drops, node N5 goes low due to resistor 52, turning off the NPN transistor 53. Next, as the NPN transistor 53 turns off, node N7 goes high, and the NMOS transistor 57 turns on.

[0068] Next, when the NMOS transistor 57 turns on, node N9 goes low, and the PMOS transistor 60 turns on. As a result, node N4 of the backup power supply 40 is connected to node N10, and the switching elements 22 (221~223) are turned on. In this way, when a power supply loss occurs, the short-circuit drive circuit 50 turns on the switching elements 22 on the low side of the inverter circuit 2, short-circuiting all phase signal lines (nodes N1~N3) of the motor drive signals (SU, SV, SW).

[0069] Next, with reference to Figure 3, the operation of the control unit 13 of the motor drive device 1 will be described. Figure 3 is a flowchart illustrating an example of the operation of the motor drive device 1 according to this embodiment. Here, we will explain the operation of the control unit 13 when the motor drive device 1 detects a voltage drop in the battery power supply VBAT, for example, due to a power failure.

[0070] As shown in Figure 3, the control unit 13 of the motor drive unit 1 first determines whether the voltage of the battery power supply VBAT is below the threshold Vth, or whether it has detected a fault requiring the motor 3 to brake (step S101). The control unit 13 detects the voltage of the battery power supply VBAT using, for example, an ADC (Analog to Digital Converter) not shown. If a fault requiring the motor 3 to brake is detected, it corresponds to a brake control instruction from the control unit 13. If the voltage of the battery power supply VBAT is below the threshold Vth, or if a fault requiring the motor 3 to brake is detected (step S101: YES), the control unit 13 proceeds to step S102. If the voltage of the battery power supply VBAT is greater than the threshold Vth, or if a fault requiring the motor 3 to brake has not been detected (step S101: NO), the control unit 13 returns to step S101.

[0071] In step S102, the control unit 13 stops controlling the switching elements 20 of the inverter circuit 2. The control unit 13 controls the control signals S1 to S6 so that all switching elements 20 are in the OFF state and the inverter drive signals DS1 to DS6 are in the low state, and outputs these signals to the inverter drive circuit 11.

[0072] Next, the control unit 13 executes the process of step S103 and the process of step S104 in parallel. In step S103, the control unit 13 causes the relay drive circuit 12 to output a short-circuit instruction. The control unit 13, using a control signal, causes the relay drive circuit 12 to output a short-circuit instruction, and the relay switch unit 30 short-circuits all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW). Furthermore, in response to a short-circuit instruction, the relay switch section 30 does not immediately close the relay switches (31, 32), but requires a certain period of time (for example, several tens of milliseconds) before closing.

[0073] Furthermore, in step S104, the control unit 13 short-circuits the entire phase signal line (nodes N1 to N3) using the low-side switching element 22. The control unit 13 instructs the short-circuit drive circuit 50 by control signal S7 to short-circuit the entire phase signal line (nodes N1 to N3) using the low-side switching element 22, and the short-circuit drive circuit 50 turns on the low-side switching element 22 (221 to 223) to short-circuit the entire phase signal line (nodes N1 to N3) of the motor drive signal (SU, SV, SW). After processing in steps S103 and S104, the control unit 13 terminates the process.

[0074] Next, with reference to Figure 4, the operation of the motor drive device 1 according to this embodiment will be described. Here, the overall operation of the motor drive device 1 when the battery power supply VBAT is lost power while the motor 3 is in a brake control state by instruction from the control unit 13 will be described.

[0075] Figure 4 is a timing chart showing an example of the operation of the motor drive device 1 according to this embodiment. In Figure 4, the horizontal axis represents time, and the vertical axis, from top to bottom, shows the waveform W1 of the battery power supply VBAT, the waveform W2 of the backup power supply 40 (voltage at node N4), the control state of the low-side switching element 22 of the short-circuit drive circuit 50, the control state of the inverter circuit 2, the state of the relay switch section 30, and the state of the motor 3.

[0076] The example shown in Figure 4 illustrates a case where the battery power supply VBAT experiences a power failure immediately after switching from normal drive control to brake control of the inverter circuit 2. In Figure 4, in the initial state, the control state of the low-side switching element 22 of the short-circuit drive circuit 50 is off, the control state of the inverter circuit 2 is in the normal drive control state, the state of the relay switch section 30 is open, and the motor 3 is in the torque control state.

[0077] Next, at time T1, the control unit 13 changes the inverter circuit 2 to a brake control state and instructs the relay drive circuit 12 to output a short-circuit instruction to the relay switch unit 30. The control unit 13 stops the control of the switching element 20 by the inverter drive circuit 11 and turns off the control state of the inverter circuit, and uses the control signal S7 to short-circuit all phase signal lines (nodes N1 to N3) with the low-side switching element 22 of the short-circuit drive circuit 50. At time T1, since it takes a certain amount of time for the relay switches (31, 32) to close, the state of the relay switch unit 30 has not yet transitioned to the closed state.

[0078] Next, at time T2, when a power failure occurs in the battery power supply VBAT and the voltage of the battery power supply VBAT drops (see waveform W1), the control unit 13 stops the control of the switching element 20 by the inverter drive circuit 11 and maintains the control state of the inverter circuit in the off state. At the same time, the control signal S7 maintains the state in which the low-side switching element 22 of the short-circuit drive circuit 50 short-circuits all phase signal lines (nodes N1 to N3). As a result, the control state of the low-side switching element 22 of the short-circuit drive circuit 50 is maintained in the on state.

[0079] Furthermore, if the battery power supply VBAT drops to a level where the control unit 13 cannot operate, the control signal S7 will go low. In this case, since the short-circuit drive circuit 50 can operate using the voltage of the backup power supply 40 (voltage at node N4), the switching element 22 may be kept in the ON state, thereby maintaining the electromagnetic brake state of the motor 3.

[0080] Next, at time T3, the relay switch unit 30 switches to the closed state, and both the relay switch unit 30 and the short-circuit drive circuit 50 short-circuit all phase signal lines (nodes N1 to N3).

[0081] Next, at time T4, if the voltage of the backup power supply 40 (voltage at node N4) drops to a level that cannot drive the low-side switching element 22, the short-circuit drive circuit 50 will no longer be able to maintain the ON state of the switching element 22, and the control state of the switching element 22 will turn OFF. However, since the relay switch section 30 has normally closed relay switches (31, 32), all phase signal lines (nodes N1 to N3) are maintained by the relay switches (31, 32).

[0082] Next, for comparison with the motor drive device 1 of this embodiment, the operation of a conventional motor drive device that does not include the backup power supply circuit 14 of this embodiment will be described with reference to Figure 5. Figure 5 is a timing chart showing an example of the operation of a conventional motor drive system.

[0083] In Figure 5, the horizontal axis represents time, and the vertical axis, from top to bottom, shows the voltage waveform W3 of the battery power supply VBAT, the control state of the inverter circuit 2, the state of the relay switch unit 30, and the state of the motor 3.

[0084] The example shown in Figure 5 illustrates a scenario similar to Figure 4, where a power failure occurs in the battery power supply VBAT immediately after switching from normal drive control to brake control in the inverter circuit 2. In Figure 5, in the initial state, the control state of the inverter circuit 2 is assumed to be the normal drive control state, the state of the relay switch unit 30 is the open state, and the motor 3 is in the torque control state.

[0085] Next, at time T11, the control unit 13 changes the inverter circuit 2 to a brake control state and causes the relay drive circuit 12 to output a short-circuit instruction to the relay switch unit 30. The control unit 13 changes the inverter drive signals DS1 to DS3 to a low state and the inverter drive signals DS4 to DS6 to a high state via the inverter drive circuit 11, thereby putting the motor 3 into an electromagnetic brake state. At time T11, since it takes a certain amount of time for the relay switches (31, 32) to close, the state of the relay switch section 30 has not yet transitioned to the closed state.

[0086] Next, at time T12, when the battery power supply VBAT experiences a power failure and its voltage drops (see waveform W3), the control unit 13 becomes inoperable, the switching element 22 can no longer be kept in the ON state, and the motor 3 becomes free.

[0087] Next, at time T13, the relay switch unit 30 switches to the closed state, and both the relay switch unit 30 and the short-circuit drive circuit 50 short-circuit all phase signal lines (nodes N1 to N3). As a result, the motor 3 enters the electromagnetic brake state.

[0088] Thus, in conventional motor drive systems, there is a period of free state (free period FT1) during which the brake state of motor 3 is temporarily released. In contrast, in the motor drive device 1 of this embodiment, as shown in Figure 4, there is no period of free state for the motor 3 (free period FT1) as in conventional motor drive devices.

[0089] As described above, the motor drive device 1 according to this embodiment comprises an inverter circuit 2, a relay switch unit 30, an inverter drive circuit 11, a relay drive circuit 12, and a backup power supply circuit 14. The inverter circuit 2 generates multi-phase motor drive signals (SU, SV, SW) to drive the motor 3 by switching the switching elements 20 (211~213, 221~223). The relay switch unit 30 can short-circuit all phase signal lines (nodes N1~Node N3) of the multi-phase motor drive signals (SU, SV, SW) using relay switches (31, 32). The inverter drive circuit 11 generates inverter drive signals (DS1~DS6) to drive the switching of the switching elements 20 in the inverter circuit 2 from power supplied from a battery power supply VBAT (DC power supply). When the brake of the motor 3 is activated, the relay drive circuit 12 outputs a short-circuit instruction via the relay switch unit 30 to short-circuit all phase signal lines (nodes N1~Node N3). The backup power supply circuit 14 uses the backup power supply 40 to short-circuit all phase signal lines (nodes N1 to N3) using the switching element 20. The backup power supply 40 charges power supplied from the battery power supply VBAT and maintains a predetermined voltage for at least the period from the short-circuit instruction until the relay switch unit 30 short-circuits all phase signal lines (nodes N1 to N3) when the power supply from the battery power supply VBAT stops.

[0090] As a result, the motor drive device 1 in this embodiment uses the backup power supply 40 to short-circuit all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW) using the switching element 20 of the inverter circuit 2. Therefore, the motor drive device can quickly activate the brake of the motor 3 even if the power supply is interrupted.

[0091] In this embodiment, the backup power supply circuit 14 includes a backup power supply 40 and a short-circuit drive circuit 50. The backup power supply 40 includes an energy storage device (capacitor 42) that charges power supplied from the battery power supply VBAT and a reverse current prevention element (diode 41) that prevents reverse current of the power supplied from the battery power supply VBAT, and maintains a predetermined voltage capable of driving the switching element 20 for at least the period from the short-circuit instruction until the relay switch unit 30 short-circuits all phase signal lines (nodes N1 to N3). The short-circuit drive circuit 50 outputs a short-circuit drive signal using the backup power supply 40 to short-circuit all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW) using the switching element 20 (low-side switching element 22).

[0092] As a result, the motor drive device 1 according to this embodiment, equipped with a backup power supply 40 and a short-circuit drive circuit 50, can reliably and quickly activate the brake of the motor 3 even if the power supply is interrupted.

[0093] In this embodiment, the energy storage device is a capacitor 42. The reverse current prevention element is a diode 41. As a result, the motor drive device 1 according to this embodiment can realize a backup power supply 40 with a simple configuration using a diode 41 and a capacitor 42.

[0094] Furthermore, the motor drive device 1 according to this embodiment includes a control unit 13 that controls the inverter drive circuit 11 and the relay drive circuit 12. When the voltage of the battery power supply VBAT falls below a threshold, or when the control unit 13 detects a fault requiring the motor 3 to be braked, it stops the control of the switching element 20 by the inverter drive circuit 11, outputs a short-circuit instruction to the relay drive circuit 12, and short-circuits all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW) by the switching element 20 to the short-circuit drive circuit 50.

[0095] As a result, in this embodiment, the motor drive device 1, after the control unit 13 stops the control of the switching element 20 by the inverter drive circuit 11, short-circuits all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW) with the short-circuit drive circuit 50. Therefore, in this embodiment, the motor drive device 1 can avoid a conflict in the control of the switching element 20 between the inverter drive circuit 11 and the short-circuit drive circuit 50, and can safely short-circuit all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW) to quickly activate the brake of the motor 3.

[0096] Furthermore, in this embodiment, the inverter circuit 2 is equipped with multiple sets (for example, three sets) of high-side switching elements 21 (first switching element) and low-side switching elements 22 (second switching element) connected in series between a high-potential power line L1 (first power line) that supplies drive power to the motor 3 and a low-potential power line L2 (second power line) that is lower in potential than power line L1. The backup power supply circuit 14 turns on all the low-side switching elements 22 connected to power line L2, thereby short-circuiting all phase signal lines (nodes N1 to N3) of the motor drive signals (SU, SV, SW).

[0097] As a result, the motor drive device 1 according to this embodiment uses the low-side switching element 22 to short-circuit all phase signal lines (nodes N1 to N3) of the motor drive signal (SU, SV, SW), allowing the motor 3 to be properly braked with a simpler configuration.

[0098] Furthermore, in this embodiment, the relay switches (31, 32) are normally closed switches that become conductive when the power supply from the battery power supply VBAT is stopped. As a result, in this embodiment, the motor drive device 1, since the relay switches (31, 32) are normally closed switches, can reliably short-circuit all phase signal lines (nodes N1 to N3) when the power supply is interrupted, thereby putting the motor 3 into a braking state.

[0099] Furthermore, in this embodiment, motor 3 is a three-phase brushless motor. As a result, the motor drive device 1 according to this embodiment can quickly activate the brake of the motor 3 in various devices using a three-phase brushless motor (for example, an electric vehicle) when the power supply is interrupted or when there is an instruction from the control unit due to other fault detection.

[0100] It should be noted that the present invention is not limited to the embodiments described above, and can be modified without departing from the spirit of the invention. For example, in the above embodiment, the backup power supply circuit 14 is shown to turn on all the low-side switching elements 22 of the inverter circuit 2 and short-circuit all phase signal lines (nodes N1 to N3) of the motor drive signals (SU, SV, SW), but it is not limited to this. The backup power supply circuit 14 may also turn on all the high-side switching elements 21 instead of the low-side switching elements 22 and short-circuit all phase signal lines (nodes N1 to N3) of the motor drive signals (SU, SV, SW).

[0101] Furthermore, although the above embodiment describes an example where motor 3 is a three-phase brushless motor, it is not limited to this and may be other motors. Motor 3 may be, for example, a motor that uses four or more phase motor drive signals.

[0102] Furthermore, although a circuit example of the backup power supply circuit 14 (backup power supply 40 and short-circuit drive circuit 50) was described using Figure 2 in the above embodiment, the circuit is not limited to this and may have other configurations. For example, the backup power supply 40 may use another energy storage device such as a secondary battery instead of the capacitor 42. Also, the backup power supply 40 may use another reverse current prevention element such as a thyristor instead of the diode 41.

[0103] The motor drive device 1 described above has a computer system inside. The processing steps of the control unit 13 described above are stored in program form on a computer-readable recording medium, and the above processing is performed when the computer reads and executes this program. Here, a computer-readable recording medium refers to a magnetic disk, magneto-optical disk, CD-ROM, DVD-ROM, semiconductor memory, etc. Alternatively, this computer program may be distributed to a computer via a communication line, and the computer that receives the distribution may execute the program. [Explanation of Symbols]

[0104] 1. Motor drive unit 2. Inverter Circuit 3 motors 11. Inverter drive circuit 12 Relay drive circuit 13 Control Unit 14. Backup power supply circuit 51, 52, 54, 55, 56, 58, 59, 61, 63, 65 Resistors 41, 62, 64, 66 diodes 20, 211, 212, 213, 221, 222, 223 switching elements 21 High-side switching element 22 Low-side switching element 23, 24, 25 Shunt resistors 30 Relay switch section 31, 32 Relay switches 40 Backup power supply 42 Capacitors 50 Short-circuit drive circuit 53 NPN transistors 57 NMOS transistors 60 PMOS transistors

Claims

1. An inverter circuit that generates multi-phase motor drive signals to drive a motor by switching switching elements, A relay switch unit that can short-circuit all phase signal lines of the multi-phase motor drive signals using a relay switch, An inverter drive circuit that generates an inverter drive signal for driving the switching of the switching elements of the inverter circuit from power supplied from a DC power supply, A relay drive circuit that, when activating the brake of the motor, outputs a short-circuit instruction via the relay switch unit to short-circuit the all-phase signal lines, A backup power supply circuit that charges with power supplied from the DC power supply and, when the power supply from the DC power supply stops, maintains a predetermined voltage for at least the period from the short-circuit instruction until the relay switch unit short-circuits the all-phase signal lines, and short-circuits the all-phase signal lines using the switching element, A motor drive device equipped with the following features.

2. The aforementioned backup power supply circuit is A backup power supply comprising a power storage device that charges power supplied from the DC power supply, and a reverse current prevention element that prevents reverse current of the power supplied from the DC power supply, and which maintains the predetermined voltage capable of driving the switching element for at least the period of time, If the power supply from the DC power supply is interrupted, or if a fault requiring the motor's brakes is detected, a short-circuit drive circuit is provided that uses the backup power supply to output a short-circuit drive signal that short-circuits the entire phase signal line using the switching element. A motor drive device according to claim 1, comprising:

3. The energy storage device is a capacitor. The motor drive device according to claim 2.

4. The reverse current prevention element is a diode. The motor drive device according to claim 2.

5. The system includes a control unit that controls the inverter drive circuit and the relay drive circuit, When the voltage of the DC power supply falls below a threshold, or when the control unit detects a fault requiring the motor to brake, it stops the control of the switching element by the inverter drive circuit, outputs the short-circuit instruction to the relay drive circuit, and instructs the short-circuit drive circuit to short-circuit the entire phase signal line using the switching element. The motor drive device according to claim 2.

6. The inverter circuit includes multiple phases of a set of first and second switching elements connected in series between a first power line on the high-potential side that supplies drive power to the motor and a second power line on the low-potential side that is lower than the potential of the first power line. The backup power supply circuit short-circuits the entire phase signal line by making all of the second switching elements connected to the second power line conductive. A motor drive device according to any one of claims 1 to 5.

7. The relay switch is a normally closed switch that becomes conductive when the power supply from the DC power source is interrupted. A motor drive device according to any one of claims 1 to 5.

8. The motor is a three-phase brushless motor. A motor drive device according to any one of claims 1 to 5.

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