Motor driver

Abstract

A motor driver for driving a motor includes: a half-bridge output section configured from a high-side transistor and a low-side transistor to which the motor is connected at a connection terminal where the high-side transistor and the low-side transistor are connected; and a control circuit that monitors a terminal voltage of the connection terminal. The control circuit starts a braking mode in which the motor is stopped by turning off the high-side transistor and turning on the low-side transistor, and in the braking mode, when the terminal voltage is lower than a first set voltage, the high-side transistor and the low-side transistor are turned off, and when the terminal voltage is lower than the first set voltage, the high-side transistor and the low-side transistor are turned off, the low-side transistor is turned on. The connection terminal is connected to a potential capable of maintaining a stopped state of the motor. As a result, it is possible to maintain the stop state of the motor drive at a low current consumption.

Description

Technical Field

[0001] The invention relates to a motor driver. Background Art

[0002] As a motor driver for driving a brushed DC motor, a motor driver having a brake mode for stopping the driving of the motor is known (see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent document 1: Japanese Patent Application Publication No. 2021-29084. Summary of the invention

[0006] In the motor driver described in Patent Document 1, when the mode is changed to a braking mode for stopping the driving of the motor, the high-side driving circuit driving the high-side transistor of the H-bridge circuit is turned off, and the low-side transistor is turned on. Since the low-side transistor is turned on, a circuit current of several mA level flows through a circuit such as an internal power supply driving the low-side transistor, thereby generating a consumption current.

[0007] An object of the present invention is to provide a motor driver capable of maintaining a stopped state of motor driving with a low current consumption.

[0008] In order to solve the above problems, one embodiment of the present invention is a motor driver for driving a motor, comprising: a half-bridge output section, which is composed of a high-side transistor and a low-side transistor, and the motor is connected to a connection terminal where the high-side transistor and the low-side transistor are connected; and a control circuit that monitors the terminal voltage of the connection terminal. The control circuit starts a braking mode for stopping the motor by turning off the high-side transistor and turning on the low-side transistor. In the braking mode, when the terminal voltage is lower than a first set voltage, the connection terminal is connected to a potential that can maintain the stopped state of the motor while the high-side transistor and the low-side transistor are turned off. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a structural diagram of a motor driver according to an embodiment.

[0010] Figure 2 This is a circuit diagram of a brake circuit provided in a control circuit of a motor driver according to an embodiment.

[0011] Figure 3 The diagram shows the relationship between the terminal voltage V1 of the motor and the signal voltage V2 input to the inverting input terminal of the comparator provided in the braking circuit in the braking mode of the motor driver according to the embodiment.

[0012] Figure 41 is a diagram showing a relationship between a terminal voltage V1 of a motor and an output voltage V3 of a comparator provided in a braking circuit in a braking mode of the motor driver according to the embodiment. DETAILED DESCRIPTION

[0013] Hereinafter, the motor driver of the embodiment will be described in detail with reference to the accompanying drawings. In addition, the embodiments described below represent general or specific examples. The numerical values, shapes, materials, components, locations of the components, and connection methods shown in the following embodiments are examples, and the main purpose is not to limit the present invention. In addition, the components not recorded in the independent claims representing the highest concepts among the components of the following embodiments are described as arbitrary components. In addition, the dimensional ratios of the drawings are exaggerated for the sake of convenience of explanation, and sometimes differ from the actual ratios. In addition, in the following embodiments and their modified examples, the same components are sometimes included, and the same components are marked with common figure marks, and repeated descriptions are omitted.

[0014] Reference Figure 1 , a basic structure of the motor driver 1 according to the embodiment will be described.

[0015] The motor driver 1 includes an H-bridge circuit for driving a brushed DC motor M (hereinafter referred to as a motor M) and a control circuit 10 for controlling the H-bridge circuit and the motor M.

[0016] The motor M is, for example, a motor for use in a vehicle and is used to drive vehicle windows, seats, seat belts, mirrors, wipers, and the like.

[0017] The H-bridge circuit includes: a first half-bridge output section composed of a first high-side transistor QH1 and a first low-side transistor QL1; and a second half-bridge output section composed of a second high-side transistor QH2 and a second low-side transistor QL2. The first high-side transistor QH1, the first low-side transistor QL1, the second high-side transistor QH2, and the second low-side transistor QL2 can use, for example, N-channel MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors).

[0018] The first electrode (e.g., drain) of the first high-side transistor QH1 and the first electrode (e.g., drain) of the second high-side transistor QH2 are connected to a terminal VB, which is connected to a DC power supply for driving the motor M. The second electrode (e.g., source) of the first high-side transistor QH1 is connected in series to the first electrode (e.g., drain) of the first low-side transistor QL1. The second electrode (e.g., source) of the second high-side transistor QH2 is connected in series to the first electrode (e.g., drain) of the second low-side transistor QL2. The second electrode (e.g., source) of the first low-side transistor QL1 and the second electrode (e.g., source) of the second low-side transistor QL2 are connected to a ground potential (ground potential) GND. The connection point between the first high-side transistor QH1 and the first low-side transistor QL1 is connected to the + terminal of the motor M, and the connection point between the second high-side transistor QH2 and the second low-side transistor QL2 is connected to the - terminal of the motor M.

[0019] The control circuit 10 includes high-side drive circuits 11-1 and 11-2, low-side drive circuits 12-1 and 12-2, and a brake circuit 13. The high-side drive circuit 11-1 is connected to the control electrode (e.g., gate) of the first high-side transistor QH1 via the terminal GH1 to control the on / off of the first high-side transistor QH1. The high-side drive circuit 11-2 is connected to the control electrode (e.g., gate) of the second high-side transistor QH2 via the terminal GH2 to control the on / off of the second high-side transistor QH2. The low-side drive circuit 12-1 is connected to the control electrode (e.g., gate) of the first low-side transistor QL1 via the terminal GL1 to control the on / off of the first low-side transistor QL1. The low-side drive circuit 12-2 is connected to the control electrode (e.g., gate) of the second low-side transistor QL2 via the terminal GL2 to control the on / off of the second low-side transistor QL2. The brake circuit 13 is connected to the + terminal of the motor M via the connection terminal BR1, and is connected to the - terminal of the motor M via the connection terminal BR2.

[0020] When the motor M is rotated in the forward direction, the control circuit 10 controls the motor in such a way that the first high-side transistor QH1 and the second low-side transistor QL2 are turned on, and the second high-side transistor QH2 and the first low-side transistor QL1 are turned off. In addition, when the motor M is rotated in the reverse direction, the control circuit 10 controls the motor in such a way that the second high-side transistor QH2 and the first low-side transistor QL1 are turned on, and the first high-side transistor QH1 and the second low-side transistor QL2 are turned off. A more detailed control method for the rotation action of the motor M can be achieved using existing methods such as the method described in patent document 1 (Japanese Patent Gazette No. 2021-29084), so the description is omitted here.

[0021] Next, refer to Figure 2, the configuration of the brake circuit 13 provided in the control circuit 10 of the motor driver 1 according to the embodiment will be described. Figure 2 : is a circuit diagram of the brake circuit 13. The brake circuit 13 is used to perform short-circuit braking by connecting the + terminal and the - terminal of the motor M to the ground potential GND in a brake mode for stopping the rotation of the motor M, thereby maintaining the stopped state of the motor M. In addition, the potential connecting the + terminal and the - terminal of the motor M is not limited to the ground potential GND, as long as it is a potential that can maintain the stopped state of the motor M.

[0022] exist Figure 2 In the embodiment, the half-bridge output section has a common structure in the first half-bridge output section and the second half-bridge output section, so for Figure 1 The description is simplified as a high-side transistor QH, a low-side transistor QL, a connection terminal BR, a terminal GH, and a terminal GL. A high-side drive circuit 11 for controlling the high-side transistor QH is connected to the terminal GH connected to the control electrode of the high-side transistor QH. A low-side drive circuit 12 for controlling the low-side transistor QL is connected to the terminal GL connected to the control electrode of the low-side transistor QL. The connection point between the high-side transistor QH and the low-side transistor QL is connected to the connection terminal BR and the terminal of the motor M.

[0023] The brake circuit 13 is constructed as described below. The first electrode of the first switch S1 is connected to the connection terminal BR via the resistor R7, and the second electrode of the first switch S1 is connected to the ground potential GND. The output terminal of the comparator C1 is connected to the control electrode of the first switch S1. The first electrode of the second switch S2 is connected to the control electrode of the first switch S1, and the second electrode of the second switch S2 is connected to the ground potential GND. The control electrode of the second switch S2 is connected to the terminal EN via the inverter 21. The series circuit of resistors R4, R5, and R6 is connected between the connection terminal BR and the ground potential GND. The first electrode of the third switch S3 is connected to the connection point of the resistor R5 and the resistor R6, the second electrode is connected to the ground potential GND, and the control electrode is connected to the output terminal of the comparator C1. For example, N-channel MOSFETs can be used for the first switch S1, the second switch S2, and the third switch S3. The series circuit of resistors R1, R2, and R3 is connected between the terminal SB and the ground potential GND. The first electrode of the fourth switch S4 is connected to the ground potential GND, the second electrode is connected to the connection point of the resistor R4 and the resistor R5 and the inverting input terminal - of the comparator C1, and the control electrode is connected to the connection point of the resistor R1 and the resistor R2. The fourth switch S4 can use a P-channel MOSFET, for example. The connection point of the resistor R2 and the resistor R3 is connected to the non-inverting input terminal + of the comparator C1. The positive power supply terminal of the comparator C1 is connected to the terminal SB via the DC current source 22, and the negative power supply terminal is connected to the ground potential GND.

[0024] The setting circuit 20 includes the comparator C1, the third switch S3, the fourth switch S4, and the resistors R1 to R6 configured as described above. The setting circuit 20 monitors the terminal voltage V1 input from the connection terminal BR to the brake circuit 13, and controls the on and off of the first switch S1 according to the terminal voltage V1.

[0025] Next, refer to Figure 2 and Figure 3 , Figure 4 , the operation of the braking mode of the motor driver 1 is described. Figure 3 1 is a diagram showing the relationship between the terminal voltage V1 in the braking mode of the motor driver 1 and the signal voltage V2 input to the inverting input terminal - of the comparator C1. Figure 4 3 is a diagram showing the relationship between the terminal voltage V1 and the output voltage V3 of the comparator C1 in the braking mode of the motor driver 1 .

[0026] When the motor driver 1 is operated in the braking mode, the operation switching voltage Ven input to the terminal EN is Vh2 (HI potential, for example, 5 V), and a predetermined control voltage Vsb is input to the terminal SB.

[0027] The action switching voltage Ven becomes Vh2, and the action switching voltage Ven is inverted by the inverter 21, and the voltage V4 input to the control electrode of the second switch S2 becomes zero (LO potential), so the second switch S2 is turned off. When the second switch S2 is turned off, the first switch S1 and the third switch S3 are controlled by the output voltage V3 of the comparator C1.

[0028] When a predetermined control voltage Vsb is input to the terminal SB, a predetermined reference voltage Vr=Vsb×R 3 / (R1+R2+R3) is input to the non-inverting input terminal + of the comparator C1. In addition, Vsb×(R2+R3) / (R1+R2+R3) is input to the control electrode of the fourth switch S4. Thus, the maximum value of the signal voltage V2 input to the inverting input terminal - of the comparator C1 can be suppressed by the clamp voltage Vc=Vsb×(R2+R3) / (R1+R2+R3)+Vs4. Here, Vs4 is the threshold voltage of the fourth switch S4. In this way, by setting the clamp voltage Vc, the brake circuit 13 can be protected from the influence of high voltage. In addition, when it is not necessary to set the clamp voltage Vc, the fourth switch S4 can be omitted.

[0029] Then, in order to start the braking mode, the control circuit 10 turns off the high-side drive circuit 11 to turn off the high-side transistor QH, and turns on the low-side transistor QL through the low-side drive circuit 12. As a result, the terminal voltage V1 decreases toward zero, and the rotation of the motor M stops. If the terminal voltage V1 starts to decrease, the control circuit 10 turns off the low-side transistor QL through the low-side drive circuit 12.

[0030] When the terminal voltage V1 is large and V1×(R5+R6) / (R4+R5+R6) is greater than the clamping voltage Vc, Figure 3 As shown in the interval (1), the voltage value of the signal voltage V2 is suppressed by the clamp voltage Vc. And, when the terminal voltage V1 further decreases and V1×(R5+R6) / (R4+R5+R6) becomes less than the clamp voltage Vc, as shown in Figure 3 As shown in the interval (2), the signal voltage becomes V2 = V1×(R5+R6) / (R4+R5+R6).

[0031] And, when the terminal voltage V1 drops to the first set voltage Vth1, the signal voltage V2 becomes smaller than the reference voltage Vr input to the non-inverting input terminal + of the comparator C1. Figure 4 As shown, the output voltage V3 of the comparator C1 switches from zero (LO potential) to Vh1 (HI potential, for example, 5V), thereby turning on the first switch S1 and the third switch S3. When the first switch S1 is turned on, the connection terminal BR is connected to the ground potential GND via the resistor R7, the terminal voltage V1 becomes zero, and the motor M becomes a short-circuit braking state.

[0032] In addition, when the third switch S3 is turned on, Figure 3 As shown in the interval (3), the signal voltage V2 input to the inverting input terminal - of the comparator C1 is switched to V2 = V1 × R5 / (R4 + R5). As a result, when the terminal voltage V1 rises, a second set voltage Vth2 greater than the first set voltage Vth1 is set as a set voltage capable of turning off the first switch S1. By setting the first set voltage Vth1 and the second set voltage Vth2 to different values, when the output voltage V3 of the comparator C1 is switched from zero to Vh1 or from Vh1 to zero, oscillation can be prevented from occurring in the output voltage V3.

[0033] According to the brake circuit 13, the connection terminal BR is connected to the ground potential GND via the resistor R7, thereby maintaining the short-circuit brake of the motor M when the low-side transistor QL is turned off. If the short-circuit brake of the motor M is maintained by turning on the low-side transistor QL, the internal power supply or gate drive circuit and other circuits used to turn on the low-side transistor QL are operated, thereby generating a consumption current of several mA. In contrast, the brake circuit 13 can maintain the short-circuit brake of the motor M when the low-side transistor QL is turned off, thereby suppressing the consumption current caused by the operation of the low-side transistor QL.

[0034] In addition, when the terminal voltage V1 is a large value, if the first switch S1 composed of an N-channel MOSFET is turned on and suddenly connected to the ground potential GND, the first switch S1 may be destroyed. Therefore, the setting circuit 20 turns on the first switch S1 when the terminal voltage V1 drops to a predetermined first setting voltage Vth1, thereby suppressing the destruction of the first switch S1.

[0035] Next, the operation when the braking mode of the motor driver 1 is released will be described.

[0036] When the braking mode is released and the action mode for actuating the motor M is entered, the action switching voltage Ven input to the terminal EN is set to zero (LO potential). By setting the action switching voltage Ven to zero, the action switching voltage Ven is inverted through the inverter 21, and the voltage V4 input to the control electrode of the second switch S2 becomes a HI potential (e.g., 5V), so the second switch S2 is switched on. When the second switch S2 is turned on, the control electrodes of the first switch S1 and the third switch S3 are connected to the ground potential GND, so no matter what the output voltage V3 of the comparator C1 is, the first switch S1 and the third switch S3 are always turned off, and the switch action is invalid. Therefore, in the action mode, no matter what the value of the terminal voltage V1 is, the action of the brake circuit 13 is invalid, which can prevent the motor M from becoming a short-circuit braking state.

[0037] And, when the high-side transistor QH is turned on, the terminal voltage V1 starts to rise from zero. Figure 3 As shown in the interval (3), the signal voltage V2=V1×R5 / (R4+R5) is input to the inverting input terminal − of the comparator C1.

[0038] When the terminal voltage V1 rises to a second set voltage Vth2 greater than the first set voltage Vth1, the signal voltage V2 becomes greater than the reference voltage Vr input to the non-inverting input terminal + of the comparator C1. Then, the output voltage V3 of the comparator C1 switches from Vh1 (HI potential) to zero (LO potential).

[0039] In addition, the value of the control voltage Vsb and the resistance values ​​of the resistors R1 to R7 can be arbitrarily set according to the values ​​of the desired clamp voltage Vc, signal voltage V2, reference voltage Vr, first setting voltage Vth1, and second setting voltage Vth2. In addition, as the setting circuit 20, an example is shown in which the control voltage Vsb is divided by resistors R1 to R3 to generate the reference voltage Vr and the clamp voltage Vc, and the terminal voltage V1 is divided by resistors R4 to R6 to generate the signal voltage V2, but it is not limited to this. The setting circuit 20 only needs to turn on the first switch S1 when the terminal voltage V1 drops to the specified first setting voltage Vth1, and its structure can be arbitrarily determined by the designer.

[0040] According to the motor driver 1 of the embodiment, in the braking mode, in the braking circuit 13, by turning on the first switch S1, the connection point between the high-side transistor QH and the low-side transistor QL, that is, the connection terminal BR is connected to the ground potential GND via the resistor R7. The connection terminal BR is connected to the ground potential GND via the resistor R7, thereby enabling the motor M to be in a short-circuit braking state. Therefore, the high-side transistor QH and the low-side transistor QL can be turned off to suppress the consumption current, so that the stop state of the drive of the motor M can be maintained with a lower consumption current.

[0041] According to the motor driver 1 of the embodiment, in the braking mode, in the braking circuit 13, the setting circuit 20 turns on the first switch S1 when the terminal voltage V1 drops to the predetermined first setting voltage Vth1. This can suppress the destruction of the first switch S1.

[0042] The brake circuit 13 can be built into a pre-driver IC (Integrated Circuit) used to drive an H-bridge circuit, for example. By building the brake circuit 13 into the pre-driver IC, the mounting area can be reduced, and the current consumption and manufacturing cost can be reduced compared to configuring the brake circuit 13 only as an IC.

[0043] (Note 1)

[0044] The motor driver 1 driving the motor M includes: a half-bridge output section, which is composed of a high-side transistor QH and a low-side transistor QL, and the motor M is connected to a connection terminal BR where the high-side transistor QH and the low-side transistor QL are connected; and a control circuit 10 that monitors a terminal voltage V1 of the connection terminal BR. The control circuit 10 starts a braking mode for stopping the motor M by turning off the high-side transistor QH and turning on the low-side transistor QL. In the braking mode, when the terminal voltage V1 is lower than a first set voltage Vth1, the connection terminal BR is connected to a potential that can maintain the stopped state of the motor M while the high-side transistor QH and the low-side transistor QL are turned off.

[0045] In the braking mode, the connection terminal BR is connected to a potential capable of maintaining the motor M in a stopped state while the high-side transistor QH and the low-side transistor QL are turned off, thereby maintaining the stopped state of the motor M with a low current consumption.

[0046] (Note 2)

[0047] In the motor driver 1 described in Supplement 1, the control circuit 10 includes a brake circuit 13 for maintaining the stopped state of the motor M. The brake circuit 13 includes: a switch S1, whose first electrode is connected to the connection terminal BR via the resistor R7, and whose second electrode is connected to the ground potential GND; and a setting circuit 20, which controls the on and off of the switch S1 according to the terminal voltage V1. In the brake mode, the setting circuit 20 turns on the switch S1 when it is detected that the terminal voltage V1 drops to the first setting voltage Vth1.

[0048] When the setting circuit 20 detects that the terminal voltage V1 has dropped to the first setting voltage Vth1 in the braking mode, the switch S1 is turned on to connect the connection terminal BR to the ground potential GND via the resistor R7 , thereby maintaining the stopped state of the motor M.

[0049] (Note 3)

[0050] In the motor driver 1 described in Note 2, the setting circuit 20 turns on the switch S1 in the braking mode when it is detected that the terminal voltage V1 drops to the first setting voltage Vth1, and sets a second setting voltage Vth2 that is larger than the first setting voltage Vth1 as a setting voltage capable of turning off the switch S1 when the terminal voltage V1 rises.

[0051] By setting the second setting voltage Vth2 to a value greater than the first setting voltage Vth1 , it is possible to prevent oscillation from occurring when the switch S1 is switched between off and on.

[0052] (Note 4)

[0053] In the motor driver 1 described in Supplementary Note 2 or 3, the control circuit 10 turns off the switch S1 when the braking mode is released.

[0054] By turning off the switch S1 in the brake release mode, the short-circuit brake state of the motor M is released.

[0055] (Note 5)

[0056] In the motor driver 1 described in Supplementary Note 4, the switch S1 is always turned off in the operation mode in which the braking mode is released.

[0057] By keeping the switch S1 always off in the operation mode, even if the setting circuit 20 is operated in the operation mode, it is possible to prevent the motor M from being in a short-circuit braking state.

[0058] (Note 6)

[0059] In the motor driver 1 according to any one of Supplementary Notes 1 to 5, the control circuit 10 includes a high-side drive circuit 11 that drives the high-side transistor QH. When the control circuit 10 shifts to the braking mode, the high-side drive circuit 11 is turned off to reduce the terminal voltage V1 toward zero.

[0060] The present invention has been described in detail above, but for those skilled in the art, the present invention is certainly not limited to the embodiments described in the present invention. The present invention can be implemented as a modification and variation without departing from the gist and scope of the present invention determined by the technical solution. Therefore, the description of the present invention is for the purpose of illustration and does not have any limiting meaning for the present invention.

Claims

1. A motor driver for driving a motor, characterized in that: include: A half-bridge output section, which is composed of a high-side transistor and a low-side transistor, and the motor is connected to a connection terminal where the high-side transistor and the low-side transistor are connected; and a control circuit that monitors a terminal voltage of the connection terminal, The control circuit Initiating a braking mode for stopping the motor by turning off the high-side transistor and turning on the low-side transistor, In the braking mode, when the terminal voltage is lower than a first set voltage, the connection terminal is connected to a potential capable of maintaining the motor in a stopped state while the high-side transistor and the low-side transistor are turned off.

2. The motor driver according to claim 1, characterized in that: The control circuit includes a brake circuit for maintaining the motor in a stopped state. The braking circuit comprises: a switch having a first electrode connected to the connection terminal via a resistor and a second electrode connected to a ground potential; and a setting circuit, which controls the on and off of the switch according to the terminal voltage, The setting circuit turns on the switch when detecting that the terminal voltage drops to the first setting voltage in the braking mode.

3. The motor driver according to claim 2, characterized in that: The setting circuit turns on the switch when detecting that the terminal voltage drops to the first setting voltage in the braking mode, and sets a second setting voltage greater than the first setting voltage as a setting voltage capable of turning off the switch when the terminal voltage rises.

4. The motor driver according to claim 2 or 3, characterized in that: The control circuit turns off the switch when the braking mode is released.

5. The motor driver according to claim 4, characterized in that: In the operation mode in which the braking mode is released, the switch is always turned off.

6. The motor driver according to claim 1, characterized in that: The control circuit includes a high-side driving circuit that drives the high-side transistor. When the control circuit shifts to the braking mode, the control circuit turns off the high-side drive circuit to reduce the terminal voltage toward zero.

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