Motor drive circuit

Abstract

To provide a motor drive circuit that can reduce a standby current in a sleep mode while suppressing the occurrence of a shoot-through current in the sleep mode.SOLUTION: A motor drive circuit 1 includes at least four FETs 5 to 8, four driver circuits 9 to 12 that turn on or off each of the TFTs 5 to 8, a control unit 13, and a through-current prevention switch 14. The through-current prevention switch 14 is provided in a circuit that connects the circuit that outputs the potential to be applied to the gate of the power supply side driver circuit 9 and the ground side. The through-current prevention switch 14 receives a control signal that is output to the ground side driver circuits 11 and 12. When a low signal is input as the control signal, the through-current prevention switch 14 opens the circuit that connects the circuit that outputs the potential to be applied to the gate and the ground side, thereby setting the gate-source voltage of the power supply side FET 5 to approximately 0 V.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a motor drive circuit. [Background technology]

[0002] For example, the drive circuit described in Patent Document 1 configures an inverter circuit that drives an electric motor using a switching element that is turned on when a drive signal is high, that is, an active-high element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-171206 A Summary of the Invention [Problem to be solved by the invention]

[0004] A motor drive circuit that controls the flow of current to an electric motor using field effect transistors (hereinafter referred to as FETs) generally comprises "four FETs," "four driver circuits for turning each of the FETs on or off," and a "control unit that controls the output of the driver circuits, i.e., the potential applied to the gate of each FET."

[0005] Incidentally, if the driver circuits are composed of current-driven transistors, when the sleep mode is entered, the control unit can reduce the standby current in those driver circuits by outputting a low signal to those four driver circuits.

[0006] However, the four driver circuits turn on the FET when the control signal output from the control unit is a low signal, and turn off the FET when the control signal is a high signal, i.e., the control logic of the four driver circuits is active low.

[0007] Therefore, when the control unit outputs a low signal to the four driver circuits to reduce the standby current in sleep mode, all four FETs are turned on, causing a through current to flow through the motor drive circuit and damaging the motor drive circuit.

[0008] In view of the above, the present disclosure discloses an example of a motor drive circuit that can reduce standby current in sleep mode while suppressing the occurrence of shoot-through current in sleep mode. [Means for solving the problem]

[0009] It is desirable for a motor drive circuit for driving the electric motor (3) mounted on a vehicle seat to have, for example, the following components. That is, the constituent elements are: of the four FETs constituting a motor bridge circuit for driving an electric motor (3), two power supply side FETs (5, 6) arranged on the power supply side of the electric motor (3); of the four FETs, two ground side FETs (7, 8) arranged on the ground side of the electric motor (3); two power supply side driver circuits (9, 10) that apply a potential to the gates of the two power supply side FETs (5, 6), the two power supply side driver circuits (9, 10) being configured with current driven transistors; and two ground side driver circuits (11, 12) that apply a potential to the gates of the two ground side FETs (7, 8), the two ground side driver circuits (11, 12) being configured with current driven transistors; The control unit (13) is a microcomputer-type control unit capable of independently controlling the operation of each of the driver circuits (11, 12), and capable of outputting a low signal or a high signal having a higher potential than the low signal as a control signal to the four FETs; and a switch element (14) capable of setting the gate-source voltage of at least one FET (5) of the two power supply side FETs (5, 6) and two ground side FETs (7, 8) to a low voltage when either two FETs (5, 6) are set as FETs to be turned off and the other two FETs (7, 8) are set as FETs to be turned off, the switch element (14) receiving a control signal outputted to a driver circuit (11, 12) corresponding to the FETs to be turned off and operating based on the control signal.

[0010] When the control unit (13) turns on any of the four FETs, it outputs a low signal to the driver circuit corresponding to the FET to be turned on, and when the sleep mode, which is a standby power supply mode, is entered, it outputs a low signal to the four driver circuits, and further, when the low signal is input, the switch element (14) sets the gate-source voltage to a low voltage. Note that the low voltage is a voltage at which the FET is turned off.

[0011] As a result, when the motor drive circuit goes into sleep mode, it outputs a low signal to the four driver circuits, making it possible to reduce the standby current of each driver circuit (9 to 12).

[0012] The switch element (14) operates using the control signal output to the driver circuit (11, 12) corresponding to the non-target FET (7, 8), so that when the sleep mode is entered, a low signal is input to the switch element (14).

[0013] As a result, the gate-source voltage of at least one FET (5) among the FETs (5, 6) to be turned off becomes low, and the FET (5) is turned off, thereby suppressing the occurrence of shoot-through current during the sleep mode.

[0014] Also, when not in the sleep mode, at least one of the control signals input to the driver circuits (11, 12) corresponding to the non-target FETs (7, 8) is a high signal. Therefore, the switch element (14) does not set the gate-source voltage to a low voltage, and the off-target FETs (5, 6) are turned on or off in response to the control signal.

[0015] Furthermore, because the switch element 14 operates using an existing control signal, there is no need to provide a separate output port in the control unit 13 for controlling the operation of the switch element 14. Therefore, by using an existing control unit, it is possible to reduce the standby current in the sleep mode while suppressing the generation of a through current in the sleep mode.

[0016] The motor drive circuit may have the following configuration, for example. That is, the FETs to be turned off are the two power supply side FETs (5, 6), and the non-target FETs are the two ground side FETs (7, 8). The switch element (14) is provided in a circuit provided in the power supply side driver circuit (9,) that connects a circuit that outputs a potential to be applied to the gate and the ground side, and it is desirable that the switch element (14) opens the circuit when a low signal is input.

[0017] It is also desirable to have a configuration including a first board (16) on which the control unit (13) is mounted, and a second board (17) on which four FETs (5-8) and a switch element (14) are mounted, and the control signal is branched within the second board (17) and input to two ground side driver circuits (11, 12) and the switch element (14).

[0018] Incidentally, the symbols in the above parentheses are examples showing the correspondence with the specific configurations etc. described in the embodiments described below, and the present disclosure is not limited to the specific configurations etc. shown by the symbols in the above parentheses. [Brief description of the drawings]

[0019] [Figure 1] 1 is a diagram showing a motor drive circuit according to a first embodiment. [Diagram 2] 1 is a diagram showing a motor drive circuit according to a first embodiment. [Diagram 3] FIG. 2 is a diagram showing a substrate of the motor drive circuit according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The following "embodiment of the invention" shows an example of an embodiment that falls within the technical scope of the present disclosure. In other words, the invention-specific matters described in the claims are not limited to the specific configurations and structures shown in the following embodiment.

[0021] This embodiment is an example in which the motor drive circuit according to the present disclosure is applied to a seat (hereinafter, referred to as a vehicle seat) mounted on a vehicle such as a car. At least one of each member or portion described with a reference symbol is provided, unless otherwise specified by "one".

[0022] (First embodiment) <1. Overview of the motor drive circuit (see Figure 1)> The motor drive circuit 1 according to this embodiment is a motor bridge circuit for driving an electric motor 3 mounted on a vehicle seat (not shown). The electric motor 3 is an electric drive source for a drive device (not shown) such as a slide device or a reclining device.

[0023] 2. Configuration of the motor drive circuit (motor bridge circuit) (see Figure 1) The motor drive circuit 1 includes at least four field effect transistors (hereinafter referred to as FETs) 5-8, four driver circuits 9-12 that turn on or off the TFTs 5-8, a control unit 13, a shoot-through current prevention switch 14, and the like.

[0024] Hereinafter, of the four FETs 5-8, the two FETs 5 and 6 arranged on the power supply side with respect to the electric motor 3 will be referred to as power supply side FETs. Also, of the four FETs 5-8, the two FETs 7 and 8 arranged on the ground side with respect to the electric motor 3 will be referred to as ground side FETs.

[0025] Hereinafter, the driver circuits 9 and 10 that apply a potential to the gates of the power-side FETs 5 and 6 are referred to as power-side driver circuits. The driver circuits 11 and 12 that apply a potential to the gates of the ground-side FETs 7 and 8 are referred to as ground-side driver circuits. The four driver circuits 9 to 12 are composed of current-driven transistors.

[0026] The control unit 13 is a microcomputer type control unit capable of independently controlling the operation of the power supply side driver circuits 9, 10 and the ground side driver circuits 11, 12. The control unit 13 is capable of outputting a low signal or a high signal having a higher potential than the low signal as a control signal to the four FETs 5 to 8.

[0027] The shoot-through current prevention switch 14 (hereinafter referred to as the switch element 14) is a semiconductor switch for setting the gate-source voltage of the power supply-side FET 5 to a low voltage. Note that this "low voltage" is a voltage (approximately 0 V in this embodiment) at which the power supply-side FET 5 is turned off.

[0028] 2, the power supply potential is applied to the source of the power supply FET 5. The switch element 14 can switch the potential that the power supply driver circuit 9 applies to the gate of the power supply FET 5 between a high potential and a low potential.

[0029] The high potential is a potential for making the gate-source voltage of the power supply FET 5 a low voltage, that is, a potential for turning off the power supply FET 5. The low potential is a potential for making the gate-source voltage of the power supply FET 5 a high voltage, that is, a voltage for turning on the power supply FET 5.

[0030] Specifically, the switch element 14 is provided in a circuit that connects a circuit that outputs a potential to be applied to the gate and the ground side in the power supply side driver circuit 9. The switch element 14 receives a control signal outputted to the ground side driver circuits 11 and 12.

[0031] Specifically, the control signal output from the output ports P3 and P4 of the control unit 13 is branched and input to the switch element 14. Diodes 15A and 15B are provided in the circuit of the control signal that is branched and reaches the switch element 14. The diodes 15A and 15B prohibit other control signals from being input to the ground side driver circuits 11 and 12.

[0032] When a low signal is input as the control signal, the switch element 14 opens the circuit connecting the circuit that outputs the potential to be applied to the gate and the ground side, thereby setting the gate-source voltage of the power supply side FET 5 to a low voltage.

[0033] When the control unit 13 turns on any of the four FETs 5 to 8, it outputs a low signal to the driver circuit corresponding to the FET that is turned on, and when the control unit 13 enters the sleep mode, which is the standby power mode, it outputs a low signal to the four driver circuits 9 to 12.

[0034] <3. Implementation of the motor drive circuit (motor bridge circuit)> 3, the control unit 13 is mounted on a first substrate 16. The four FETs 5 to 8 and the switch element 14 are mounted on a second substrate 17. The control signal is branched within the second substrate 17 and input to the two ground side driver circuits 11 and 12 and the switch element 14.

[0035] In this embodiment, the first substrate 16 and the second substrate 17 are arranged in the vehicle seat in a state where they are stacked in the thickness direction of the substrates (specifically, in the vertical direction). Note that, in this embodiment, the first substrate 16 is arranged below the second substrate 17.

[0036] <4. Operation and Features of the Motor Drive Circuit According to the Present Embodiment> When the sleep mode is entered, the control unit 13 outputs a low signal to the four driver circuits 9 to 12. This makes it possible for the motor drive circuit 1 to reduce the standby current of each of the driver circuits 9 to 12 in the sleep mode.

[0037] The switch element 14 operates using the control signal outputted to the ground side driver circuits 11 and 12, so that a low signal is inputted to the switch element 14 when the sleep mode is entered.

[0038] As a result, the gate-source voltage of the power supply FET 5 becomes approximately 0 V, turning off the power supply FET 5. This prevents the occurrence of a shoot-through current in the sleep mode.

[0039] In addition, when not in the sleep mode, at least one of the control signals input to the ground side driver circuits 11, 12 is a high signal. Therefore, the switch element 14 does not set the gate-source voltage to a low voltage of approximately 0 V, and the power supply side FET 5 is turned on or off in response to the control signal.

[0040] Furthermore, since switch element 14 operates using an existing control signal, there is no need to secure a separate output port in control unit 13 for controlling the operation of switch element 14. Therefore, by using existing control unit 13, it is possible to reduce the standby current in the sleep mode while suppressing the occurrence of a through current in the sleep mode.

[0041] The control unit 13 is mounted on a first substrate 16, and the four FETs 5 to 8 and the switch element 14 are mounted on a second substrate 17. The first substrate 16 and the second substrate 17 are arranged in a stacked state in the thickness direction of the substrate (specifically, in the vertical direction). This makes it possible to reduce the layout area of ​​the substrate.

[0042] (Other embodiments) In the above embodiment, the switch element 14 is connected to the power supply side driver circuit 9. However, the present disclosure is not limited to this. That is, the present disclosure may be configured such that the switch element 14 is connected to any one of the driver circuits 10 to 12, for example.

[0043] The sources of the ground driver circuits 11 and 12 are connected to the ground side. Therefore, in a configuration in which the switch element 14 is connected to the ground driver circuits 11 and 12, the switch element 14 opens and closes the circuit connecting the power supply side and the ground driver circuits 11 and 12.

[0044] The switch element 14 according to the above embodiment is configured as a Darlington transistor. However, the present disclosure is not limited to this. That is, the switch element 14 according to the present disclosure may be a switch other than a Darlington transistor as long as it is capable of opening and closing a circuit upon receiving a low signal.

[0045] In the above embodiment, the vehicle seat according to the present disclosure is applied to a vehicle. However, the application of the invention disclosed in this specification is not limited thereto. That is, the disclosure can be applied to, for example, seats used in vehicles such as railroad cars, ships, and aircraft, as well as stationary seats used in theaters, homes, and the like.

[0046] Furthermore, the present disclosure is not limited to the above-mentioned embodiments as long as it is consistent with the gist of the disclosure described in the above-mentioned embodiments. Therefore, the present disclosure may be a configuration in which at least two of the above-mentioned embodiments are combined, or a configuration in which any of the components illustrated or the components described with reference numerals in the above-mentioned embodiments are eliminated. [Explanation of symbols]

[0047] 1. Motor drive circuit 3. Electric motor 5~8… TFT5 9~12… Driver circuit 13... Control section 14...Through current prevention switch (switch element) 15A, 15B... Diode

Claims

1. A motor drive circuit for driving an electric motor mounted on a vehicle seat, Among four FETs constituting a motor bridge circuit for driving the electric motor, two power supply side FETs are arranged on the power supply side with respect to the electric motor; Among the four FETs, two ground-side FETs are arranged on the ground side with respect to the electric motor; two power supply driver circuits for applying a potential to the gates of the two power supply FETs, the two power supply driver circuits being configured with current-driven transistors; two ground driver circuits for applying a potential to the gates of the two ground FETs, the two ground driver circuits being configured with current-driven transistors; a microcomputer-type control unit capable of independently controlling the operation of each of the two power supply driver circuits and the two ground driver circuits, the control unit being capable of outputting a low signal or a high signal having a higher potential than the low signal as a control signal to the four FETs; a switch element capable of setting a gate-source voltage of at least one of the FETs to be turned off to a low voltage when either one of the two power supply side FETs and the two ground side FETs is set to an FET to be turned off and the other two FETs are set to an FET that is not an FET to be turned off, the switch element receiving a control signal outputted to a driver circuit corresponding to the FET that is not an FET to be turned off and operating based on the control signal; When the control unit turns on any one of the four FETs, the control unit outputs a low signal to the driver circuit corresponding to the FET to be turned on, and when the control unit enters a sleep mode, which is a standby power supply mode, outputs a low signal to the four driver circuits; Furthermore, the low voltage is a voltage at which an FET is turned off, and the switch element sets the gate-source voltage to a low voltage when a low signal is input.

2. the off-target FETs are the two power supply side FETs, and the non-target FETs are the two ground side FETs; 2. The motor drive circuit according to claim 1, wherein the switch element is provided in "a circuit provided in the power supply side driver circuit, the circuit connecting a circuit that outputs a potential to be applied to a gate and a ground side," and the switch element opens the circuit when a low signal is input.

3. A first substrate on which the control unit is mounted; a second substrate on which the four FETs and the switch element are mounted, 3. The motor drive circuit according to claim 2, wherein the control signal is branched within the second substrate and input to the two ground side driver circuits and the switch element.

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