Drive circuit

Abstract

This invention provides a three-phase DC motor drive circuit that reduces the load on components within the circuit even when one of the two terminals receiving power is open. [Solution] The drive circuit 200 is a drive circuit for a three-phase DC motor integrated on a single semiconductor substrate, and includes a control unit 210 capable of controlling a bridge circuit 230 connected to the motor 102, a first power supply terminal VM that receives power supply for motor driving, a second power supply terminal VCC that receives power supply for circuit control, a protection element 250 connected between the first power line 240 and the second power line 242, and a clamp circuit 260 connected between the first power line 240 and the second power line 242. Immediately after the power to the drive circuit 200 is turned on, the control unit 210 maintains a reset state if the potential difference between the first power line VM and the second power line VCC is greater than or equal to a predetermined value, and releases the reset state if the potential difference is less than the predetermined value.

Description

[Technical Field]

[0001] This disclosure relates to a drive circuit. [Background technology]

[0002] A known type of drive circuit for a three-phase DC motor uses two separate power supplies as input: one for driving the motor and another for controlling the circuit. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-129021

[0004] One possibility is to integrate the drive circuit of a three-phase DC motor using two input power supplies into a single integrated circuit (IC) chip on a single semiconductor substrate. In such a case, there was a problem that if, for example, a mounting defect caused one of the power supply terminals to become open, excessive stress could be placed on the elements within the circuit.

[0005] [overview] This disclosure is made in such circumstances, and one exemplary object of a certain aspect thereof is to provide a drive circuit for a three-phase DC motor that can reduce the load on elements in the circuit even when one of the two terminals receiving power is open.

[0006] One aspect of the present disclosure is a drive circuit. The drive circuit is a drive circuit for a three-phase DC motor that is integrally integrated on a single semiconductor substrate, and includes a control unit capable of controlling a bridge circuit connected to the motor, a first power supply terminal that receives power supply for motor drive, a second power supply terminal that receives power supply for circuit control, a protection element connected between a first power supply line connected to the first power supply terminal and a second power supply line connected to the second power supply terminal, and a clamp circuit connected between the first power supply line and the second power supply line. The control unit maintains the reset state if the potential difference between the first power supply line and the second power supply line is greater than or equal to a predetermined value immediately after the drive circuit is powered on, and releases the reset state if the potential difference is less than the predetermined value.

[0007] In addition, combinations of the above components arbitrarily, or components and expressions mutually replaced between methods, apparatuses, systems, etc. are also valid as aspects of the present invention or the present disclosure. Furthermore, the description of this item does not explain all the essential features of the present invention, and therefore, sub-combinations of these described features can also be the present invention.

Brief Description of the Drawings

[0008] [Figure 1] FIG. 1 is a circuit diagram showing a drive circuit 200 in which an input power supply is divided into two systems in a drive circuit for a three-phase DC motor. [Figure 2] FIG. 2 is a circuit diagram showing a drive circuit with a protection element added to the drive circuit shown in FIG. 1. [Figure 3] FIG. 3 is a circuit diagram of a system including a drive circuit according to the first embodiment. [Figure 4] FIG. 4 is a circuit diagram for explaining a current path when the first power supply terminal is open in the drive circuit shown in FIG. 3. [Figure 5] FIG. 5 is a circuit diagram for explaining a current path when the second power supply terminal is open in the drive circuit shown in FIG. 3. [Figure 6] FIG. 6 is a flowchart for explaining an example of the operation of the control unit in the drive circuit shown in FIG. 3. [Figure 7] Figure 7 is a circuit diagram of a system equipped with a drive circuit according to the second embodiment. [Figure 8] Figure 8 is a circuit diagram illustrating the current path when the first power supply terminal is open in the drive circuit shown in Figure 7. [Figure 9] Figure 9 is a circuit diagram illustrating the current path when the second power supply terminal is open in the drive circuit shown in Figure 7.

[0009] [Detailed explanation] (Summary of the embodiment) This section outlines some exemplary embodiments of the present disclosure. This outline is intended to provide a basic understanding of the embodiments and to simplify some concepts of one or more embodiments, serving as a prelude to the more detailed descriptions that follow. It is not intended to limit the scope of the invention or disclosure. This outline is not a comprehensive overview of all possible embodiments, nor is it intended to identify essential elements of all embodiments or to delineate the scope of some or all aspects. For convenience, “one embodiment” may be used to refer to one or more embodiments (examples or variations) disclosed herein.

[0010] A drive circuit according to one embodiment is a drive circuit for a three-phase DC motor integrated on a single semiconductor substrate, comprising: a control unit capable of controlling a bridge circuit connected to the motor; a first power supply terminal that receives power for motor driving; a second power supply terminal that receives power for circuit control; a protection element connected between a first power line connected to the first power supply terminal and a second power line connected to the second power supply terminal; and a clamp circuit connected between the first power line and the second power line. The control unit maintains a reset state immediately after the power to the drive circuit is turned on if the potential difference between the first power line and the second power line is greater than or equal to a predetermined value, and releases the reset state if the potential difference is less than the predetermined value.

[0011] With this configuration, even if one of the power terminals is open due to a mounting defect or other reason, the protective element and clamp circuit can maintain a constant potential difference between the power lines, thereby reducing the load on the components in the circuit. Furthermore, if the potential difference between the power lines is above a predetermined value immediately after power-on, the reset state is maintained, which suppresses the flow of large currents through the clamp circuit, preventing damage to the clamp circuit, preventing abnormal operation, and allowing the operator to recognize that an abnormal condition has occurred.

[0012] In one embodiment, the control unit may keep the reset state released regardless of the potential difference after the reset state is released, while the power to the drive circuit is turned on. In this case, after the reset state is released and the motor is driven, the reset state remains released even if the potential difference between the power lines becomes large while the motor is being driven, so the motor can be driven stably.

[0013] In one embodiment, the protection element may include a protection diode having a forward direction from the second power line to the first power line, and the clamp circuit may include a set in series of a clamp diode having a forward direction from the first power line to the second power line and a Zener diode having a reverse direction from the first power line to the second power line. In this case, even if the first power terminal is open, current flows from the second power line to the first power line through the protection diode, ensuring a potential difference between the power lines, and even if the second power terminal is open, current flows from the first power line to the second power line through the clamp circuit, ensuring a potential difference between the power lines, thus reducing the burden on the elements in the circuit.

[0014] In one embodiment, the protection element may include a first protection diode having a forward direction from the second power line to the first power line, and a second protection diode connected in series with the first protection diode and having a forward direction from the first power line to the second power line. The clamp circuit may include a first set in which a first clamp diode having a forward direction from the first power line to the second power line and a first Zener diode having a reverse direction from the first power line to the second power line are connected in series, and a second set in which a second clamp diode having a forward direction from the second power line to the first power line and a second Zener diode having a reverse direction from the second power line to the first power line are connected in series, and the first set and the second set may be connected in parallel with each other. In this case, even if the first power terminal is open, current flows from the second power line to the first power line through the second set of clamp circuits, ensuring a potential difference between the power lines. Similarly, even if the second power terminal is open, current flows from the first power line to the second power line through the first set of clamp circuits, ensuring a potential difference between the power lines. This reduces the load on the components within the circuit.

[0015] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. Furthermore, the embodiments are illustrative and not limiting to the disclosure and invention, and not all features or combinations thereof described in the embodiments are necessarily essential to the disclosure and invention.

[0016] In this specification, "member A connected to member B" includes cases where member A and member B are physically and directly connected, as well as cases where member A and member B are indirectly connected via other members that do not substantially affect their electrical connection or impair the functions or effects produced by their connection.

[0017] Similarly, "the state in which member C is provided between member A and member B" includes not only cases where member A and member C, or member B and member C, are directly connected, but also cases where they are indirectly connected via other members that do not substantially affect their electrical connection state or impair the functions or effects produced by their combination.

[0018] First, referring to Figures 1 and 2, we will explain the effects of dividing the input power supply into two systems in a three-phase DC motor drive circuit, and the challenges of integrating such a drive circuit onto a single semiconductor substrate.

[0019] Figure 1 is a circuit diagram showing a drive circuit 200A for a three-phase DC motor, in which the input power supply is divided into two systems. The motor 102 connected to the drive circuit 200A is a three-phase brushless DC motor, and the U-phase coil L U V-phase coil L V W-phase coil L W This includes the following: The drive circuit 200A connects to the coil L of the motor 102 via output terminals U, V, W. U ~L W The motor 102 is driven according to the drive signal supplied to it.

[0020] The drive circuit 200A comprises a control unit 210A, a pre-driver 220, and a bridge circuit 230. The drive circuit 200A is a functional IC integrated on a single semiconductor substrate.

[0021] The bridge circuit 230 is a three-phase inverter to be driven, and has U-phase legs, V-phase legs, and W-phase legs. The # phase (#=U,V,W) legs are upper arm Q #-H and lower arm Q #-LIt includes. The upper arm and the lower arm each include a switching element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), or a bipolar transistor, and a freewheeling diode (also called a flywheel diode) connected in parallel with the switching element. As shown in FIG. 1, when a MOSFET is used as the switching element, its body diode (not shown) becomes the freewheeling diode. Hereinafter, an example in which a P-type MOSFET is used as the upper arm and an N-type MOSFET is used as the lower arm will be described.

[0022] The control unit 210A controls the bridge circuit 230 connected to the motor 102. Specifically, the control unit 210A generates a control signal to rotate the motor 102. The control signal generated by the control unit 210A may include six signals indicating the on and off states of the upper-arm Q U-H , Q V-H , Q W-H and the lower-arm Q U-L , Q V-L , Q W-L .

[0023] A rotation speed signal indicating the rotation speed of the motor 102 may be input to the control unit 210A. The rotation speed signal is a pulse signal and has a frequency proportional to the rotation speed of the motor 102. The method for generating the rotation speed signal is not particularly limited. When the motor 102 has a sensor, the rotation speed signal may be generated by converting the output of the Hall element into a rectangular wave using a comparator. When the motor 102 is sensorless, the rotation speed signal may be generated by converting the back electromotive force generated in the coil of the motor 102 into a rectangular wave using a comparator.

[0024] The control method and circuit configuration of the control unit 210A are not particularly limited, and known technologies may be used. Specifically, the control unit 210A may control the motor 102 by wide-angle energization control with an energization angle of 120 degrees or more and less than 180 degrees (for example, 120 degrees, 135 degrees, 150 degrees, etc.), or it may control the motor 102 by 180-degree energization control (also called sinusoidal drive). The control unit 210A may perform wide-angle energization control (for example, 120-degree energization control) immediately after startup when the rotational speed of the motor 102 is low, and then perform 180-degree energization control after the rotational speed of the motor 102 has stabilized. Although not shown in Figure 1, the control unit 210A may change the target rotational speed in response to an external rotational speed control signal or the output signal of a temperature detection element.

[0025] The pre-driver 220 is the upper arm Q of the bridge circuit 230. U-H ,Q V-H ,Q W-H and lower arm Q U-L ,Q V-L ,Q W-L Connected to the gate, the upper arm Q of the bridge circuit 230 is controlled by the control unit 210A based on the control signal. U-H ,Q V-H ,Q W-H and lower arm Q U-L ,Q V-L ,Q W-L It drives the upper arm Q. The pre-driver 220 drives the upper arm Q. U-H and lower arm Q U-L The pre-driver 220U is connected to the gate, and the upper arm Q V-H , and lower arm Q V-L The pre-driver 220V connected to the gate, and the upper arm Q W-H and lower arm Q W-L Includes a 220W pre-driver connected to the gate.

[0026] The drive circuit 200A is capable of accepting two input power supplies. Specifically, the drive circuit 200A includes a first power supply terminal VM that receives power to drive the motor 102, a first power supply line 240 connected to the first power supply terminal VM, a second power supply terminal VCC that receives power to control various elements within the drive circuit 200A, and a second power supply line 242 connected to the second power supply terminal VCC. The first power supply terminal VM may be supplied with a power supply voltage to drive the motor 102 via a reverse-connection prevention diode D1. The second power supply terminal VCC may be supplied with a power supply voltage to control the drive circuit 200A via a reverse-connection prevention diode D2. The first power supply line 240 includes the control unit 210A and the upper arm Q of the bridge circuit 230. U-H ,Q V-H ,Q W-H It is connected to the source. The second power line 242 is connected to the control unit 210A and the pre-driver 220.

[0027] The drive circuit 200A is equipped with a grounding terminal GND. The grounding line 244 connected to the grounding terminal GND is connected to the control unit 210A, the pre-driver 220, and the lower arm Q of the bridge circuit 230. U-L ,Q V-L ,Q W-L It is connected to the drain.

[0028] In general, in a three-phase DC motor drive circuit, if the output of the bridge circuit suddenly becomes high impedance, or if the current flowing into or out of the motor coil (also called coil current) fluctuates abruptly, some of the current may flow into the power line. In such a case, in a drive circuit with only one input power supply, the power supply voltage may rise due to the current flowing into the power line, and a high voltage may be applied to the elements in the drive circuit. On the other hand, in a drive circuit 200A with two input power supplies, when current flows into the first power line 240 via the bridge circuit 230, the potential of the first power terminal VM rises, causing the upper arm Q of the bridge circuit 230 to rise. U-H ,Q V-H ,Q W-HAs the potential of each source increases, a coil current is generated through the bridge circuit 230 by self-regeneration, thus suppressing the rise in potential of the first power supply terminal VM.

[0029] Figure 2 is a circuit diagram showing drive circuit 200B, which is the drive circuit 200A shown in Figure 1 with a protection element 250 added. In Figure 2, components common to Figure 1 are denoted by the same reference numerals, and explanations are omitted as appropriate.

[0030] The drive circuit 200B, like the drive circuit 200A, is a functional IC integrated on a single semiconductor substrate. In addition to the configurations of the drive circuit 200A, it includes a protection element 250 connected between the first power line 240 and the second power line 242. The protection element 250 is a protection element for ESD (Electro-Static Discharge) protection and includes a diode as an example. In the example shown in Figure 2, the protection element 250 includes a protection diode 252 that has a forward direction from the second power line 242 to the first power line 240. That is, the anode of the protection diode 252 is connected to the second power line 242 and the cathode is connected to the first power line 240.

[0031] The drive circuit 200B can achieve ESD protection by incorporating the protection element 250. Furthermore, in the drive circuit 200A shown in Figure 1, if the output terminals U, V, and W are short-circuited to the ground line 244, the potential of the first power supply terminal VM decreases via the bridge circuit 230. At this time, the potential of the second power supply terminal VCC becomes excessively higher than the potential of the first power supply terminal VM, causing the upper arm Q of the bridge circuit 230 to become significantly higher. U-H ,Q V-H ,Q W-H The element may be destroyed if the gate-source breakdown voltage is exceeded. In contrast, in the drive circuit 200B shown in Figure 2, even if the output terminals U, V, and W are shorted to the ground line 244, the protection element 250 prevents the potential difference between the first power supply terminal VM and the second power supply terminal VCC from becoming excessive, thus preventing element destruction.

[0032] In the drive circuit 200A shown in Figure 1, if the first power terminal VM or the second power terminal VCC becomes open due to mounting defects or other reasons, excessive stress may be placed on the components within the drive circuit 200A. Specifically, when the first power terminal VM is open, the potential of the second power terminal VCC becomes excessively higher than the potential of the first power terminal VM, causing the upper arm Q of the bridge circuit 230 to become excessively high. U-H ,Q V-H ,Q W-H The voltage between the gate and source may exceed the breakdown voltage, potentially destroying the element. Furthermore, if the second power supply terminal VCC is open, the potential of the first power supply terminal VM becomes significantly higher than the potential of the second power supply terminal VCC, resulting in the upper arm Q of the bridge circuit 230 being excessively high. U-H ,Q V-H ,Q W-H The element may be destroyed if the gate-source breakdown voltage is exceeded. This problem is also present in the drive circuit 200B shown in Figure 2. In the drive circuit 200B, if the first power supply terminal VM is open, depending on the performance of the protection element 250, it may be possible to prevent the potential difference between the first power supply terminal VM and the second power supply terminal VCC from becoming excessive.

[0033] Thus, when integrating a drive circuit for a three-phase DC motor with two separate input power supplies onto a single semiconductor substrate, there is a problem that if either of the power supply terminals is open, excessive stress can be placed on the components within the circuit. Below, we will describe a three-phase DC motor drive circuit that can reduce the stress on the components within the circuit even if one of the two power supply terminals is open.

[0034] (First Embodiment) Figure 3 is a circuit diagram of a system 100 equipped with a drive circuit 200 according to the first embodiment. The system 100 includes a motor 102 and a drive circuit 200. The motor 102 is, for example, a fan motor, and the system 100 is, for example, a cooling device. Alternatively, the system 100 may be an electronic device comprising a cooling device and a CPU (Central Processing Unit) or the like to be cooled. In Figure 3, components common to Figure 2 are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0035] The drive circuit 200 includes a control unit 210, a pre-driver 220, a bridge circuit 230, a protection element 250, a clamp circuit 260, and a potential difference detection unit 270. The drive circuit 200 is a functional IC integrated on a single semiconductor substrate, similar to drive circuits 200A and 200B. Among the components of the drive circuit 200B, the control unit 210A is replaced with a control unit 210, and the clamp circuit 260 and potential difference detection unit 270 are further included.

[0036] The control unit 210 has the functions described for the control unit 210A. Functions of the control unit 210 that differ from those of the control unit 210A will be described later. The control unit 210 may be configured as a logic circuit, or it may be implemented as a combination of a processor and a software program.

[0037] The clamp circuit 260 is connected between the first power line 240 and the second power line 242. The clamp circuit 260 includes a clamp diode 262 having a forward direction from the first power line 240 to the second power line 242, and a Zener diode 264 having a reverse direction from the first power line 240 to the second power line, connected in series. That is, the anode of the clamp diode 262 is connected to the first power line 240 and the cathode is connected to the second power line 242. The anode of the Zener diode 264 is connected to the second power line 242 and the cathode is connected to the first power line 240.

[0038] The potential difference detection unit 270 is connected to the first power line 240, the second power line 242, and the ground line 244, and detects the potential difference between the first power line 240 and the second power line 242. The potential difference detection unit 270 is, for example, a comparator.

[0039] Figure 4 is a circuit diagram illustrating the current path in the drive circuit 200 when the first power supply terminal VM is open. When the first power supply terminal VM is open, the current input from the second power supply terminal VCC flows from the second power supply line 242 through the protection diode 252 of the protection element 250 to the first power supply line 240. Here, if the forward voltage of the protection diode 252 is VF1, the potential difference between the first power supply line 240 and the second power supply line 242 is VF1. As an example, VF1 is approximately 1V. By appropriately selecting elements with suitable characteristics, the upper arm Q of the bridge circuit 230 can be controlled. U-H ,Q V-H ,Q W-H The potential difference between the gate and source can be kept within the breakdown voltage range, thereby preventing device failure.

[0040] Figure 5 is a circuit diagram illustrating the current path in the drive circuit 200 when the second power supply terminal VCC is open. When the second power supply terminal VCC is open, the current input from the first power supply terminal VM flows from the first power supply line 240 through the clamp diode 262 and Zener diode 264 of the clamp circuit 260 to the second power supply line 242. Here, if the forward voltage of the clamp diode 262 is VF2 and the Zener voltage of the Zener diode 264 is VZ1, then the potential difference between the first power supply line 240 and the second power supply line 242 is VF2 + VZ1. As an example, VF2 is approximately 1V and VZ1 is approximately 5V. By appropriately selecting elements with suitable characteristics, the upper arm Q of the bridge circuit 230 can be controlled. U-H ,Q V-H ,Q W-H The potential difference between the gate and source can be kept within the breakdown voltage range, thereby preventing device failure.

[0041] Thus, in the drive circuit 200, even if the first power terminal VM or the second power terminal VCC is open due to a mounting defect or the like, the protection element 250 and the clamp circuit 260 can maintain a constant potential difference between the power lines, thereby reducing the load on the elements in the circuit.

[0042] Figure 6 is a flowchart illustrating an example of the operation of the control unit 210 in the drive circuit 200. When the power to the drive circuit 200 is turned on (S10), the control unit 210 enables the detection of the potential difference between the first power line 240 and the second power line 242 by the potential difference detection unit 270 (S12). Immediately after the power to the drive circuit 200 is turned on, the control unit 210 is in a reset state and does not drive the motor.

[0043] If the potential difference between the first power line 240 and the second power line 242 is greater than or equal to a predetermined value (Y in S14), the control unit 210 maintains the reset state (S16) and returns to the determination in step S14. Here, the predetermined value of the potential difference used in the determination in step S14 is, for example, less than or equal to VF1 and less than or equal to VF2 + VZ1. As a result, if the first power terminal VM or the second power terminal VCC of the drive circuit 200 is open, the reset state will be maintained.

[0044] If the potential difference between the first power line 240 and the second power line 242 is less than a predetermined value (N in S14), the control unit 210 releases the reset state (S18) and disables the detection of the potential difference between the first power line 240 and the second power line 242 by the potential difference detection unit 270 (S20). In other words, as long as the power to the drive circuit 200 is turned on, the control unit 210 keeps the reset state released after releasing the reset state, regardless of the potential difference between the first power line 240 and the second power line 242. The order in which steps S18 and S20 are executed is not limited, and they may be executed simultaneously.

[0045] As described above, the control unit 210 maintains the reset state if the potential difference between the power lines is greater than or equal to a predetermined value immediately after power-on, thereby preventing abnormal operation. Furthermore, since the reset state is maintained, it suppresses the flow of a large current through the clamp circuit, preventing damage to the clamp circuit 260, and also allows the operator to recognize that the drive circuit 200 is in an abnormal state. In addition, after the reset state is released and the motor 102 is driven, even if the potential difference between the power lines becomes large while the motor 102 is being driven, the reset state remains released, allowing the motor 102 to be driven stably.

[0046] (Second Embodiment) Figure 7 is a circuit diagram of a system 300 equipped with a drive circuit 400 according to the second embodiment. The system 300 includes a motor 102 and a drive circuit 400. In Figure 7, components common to Figure 3 are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0047] The drive circuit 400 includes a control unit 410, a pre-driver 220, a bridge circuit 230, a protection element 250A, a clamp circuit 260A, and a potential difference detection unit 270. The drive circuit 400 is a functional IC integrated on a single semiconductor substrate, similar to the drive circuit 400, and replaces the control unit 210, protection element 250, and clamp circuit 260 of the drive circuit 400 with a control unit 410, protection element 250A, and clamp circuit 260A.

[0048] The protection element 250A is an ESD protection element and is connected between the first power line 240 and the second power line 242. The protection element 250A includes a first protection diode 252A having a forward direction from the second power line 242 toward the first power line 240, and a second protection diode 254 having a forward direction from the first power line 240 toward the second power line 242. That is, the anode of the first protection diode 252A is connected to the second power line 242 and the cathode is connected to the first power line 240. The anode of the second protection diode 254 is connected to the first power line 240 and the cathode is connected to the second power line 242. The first protection diode 252A and the second protection diode 254 are connected in series with each other. In this example, the first protection diode 252A is the same as the protection diode 252 in the first embodiment.

[0049] The clamp circuit 260A is connected between the first power line 240 and the second power line 242. The clamp circuit 260A includes a set (hereinafter referred to as the first set) in which a first clamp diode 262A having a forward direction from the first power line 240 to the second power line 242 and a first Zener diode 264A having a reverse direction from the first power line 240 to the second power line 242 are connected in series, and a second clamp diode 266 having a forward direction from the second power line 242 to the first power line 240 and a second Zener diode 268 having a reverse direction from the second power line 242 to the first power line 240 are connected in series (hereinafter referred to as the second set). In other words, the anode of the first clamp diode 262A is connected to the first power line 240 and the cathode is connected to the second power line 242. The first Zener diode 264A has its anode connected to the second power line 242 and its cathode connected to the first power line 240. The second clamp diode 266 has its anode connected to the second power line 242 and its cathode connected to the first power line 240. The second Zener diode 268 has its anode connected to the first power line 240 and its cathode connected to the second power line 242. The first and second sets are connected in parallel with each other. In this example, the first clamp diode 262A and the first Zener diode 264A are the same as the clamp diode 262 and Zener diode 264 in the first embodiment, respectively.

[0050] The control unit 410 has the functions described for the control unit 210. The functions of the control unit 410 that differ from those of the control unit 210 will be described later. The control unit 410 may be configured as a logic circuit, or it may be implemented as a combination of a processor and a software program.

[0051] Figure 8 is a circuit diagram illustrating the current path in the drive circuit 400 when the first power supply terminal VM is open. When the first power supply terminal VM is open, the current input from the second power supply terminal VCC flows from the second power supply line 242 through the second set of clamp circuit 260A, namely the second clamp diode 266 and the second Zener diode 268, to the first power supply line 240. Here, if the forward voltage of the second clamp diode 266 is VF3 and the Zener voltage of the second Zener diode 268 is VZ2, then the potential difference between the first power supply line 240 and the second power supply line 242 is VF3 + VZ2. As an example, VF3 is approximately 1V and VZ2 is approximately 5V. By appropriately selecting elements with suitable characteristics, the upper arm Q of the bridge circuit 230 can be controlled. U-H ,Q V-H ,Q W-H The potential difference between the gate and source can be kept within the breakdown voltage range, thereby preventing device failure.

[0052] Figure 9 is a circuit diagram illustrating the current path in the drive circuit 400 when the second power supply terminal VCC is open. When the second power supply terminal VCC is open, the current input from the first power supply terminal VM flows from the first power supply line 240 through the first set of clamp circuit 260A, namely the first clamp diode 262A and the first Zener diode 264A, to the second power supply line 242. Here, the forward voltage of the first clamp diode 262A is VF2, and the Zener voltage of the first Zener diode 264A is VZ1, so the potential difference between the first power supply line 240 and the second power supply line 242 is VF2 + VZ1. As an example, VF2 is approximately 1V and VZ1 is approximately 5V. By appropriately selecting elements with suitable characteristics, the upper arm Q of the bridge circuit 230 can be controlled. U-H ,Q V-H ,Q W-H The potential difference between the gate and source can be kept within the breakdown voltage range, thereby preventing device failure.

[0053] Thus, in the drive circuit 400, even if the first power terminal VM or the second power terminal VCC is open due to a mounting defect or the like, the potential difference between the power lines can be kept constant by the protection element 250A and the clamp circuit 260A, thereby reducing the load on the elements in the circuit.

[0054] Furthermore, in this embodiment, as described above, the potential difference between the first power line 240 and the second power line 242 when the first power terminal VM is open is approximately 6V (VF3 + VZ2), while the potential difference in the first embodiment is approximately 1V (VF1). Therefore, the potential difference is easier to detect by the potential difference detection unit 270 in this embodiment. On the other hand, in this embodiment, when the output terminals U, V, and W are shorted to the ground line 244, a large current from the second power terminal VCC flows through the second power line 242, through the second clamp diode 266 and the second Zener diode 268, and into the first power line 240. This puts a particular strain on the second Zener diode 268. For this reason, it is preferable to select either the drive circuit 200 according to the first embodiment or the drive circuit 400 according to the second embodiment depending on the application.

[0055] The control unit 410 in the drive circuit 400 according to this embodiment can perform operations similar to those of the control unit 210 in the first embodiment, as well as the flowchart shown in Figure 6. In this embodiment, the predetermined value of the potential difference used in the determination in step S14 is, for example, less than or equal to VF3 + VZ2 and less than or equal to VF2 + VZ1. As a result, if the first power supply terminal VM or the second power supply terminal VCC of the drive circuit 400 is open, the reset state will be maintained.

[0056] The embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible for each component and each processing process, and that such modifications also fall within the scope of this disclosure or the present invention.

[0057] (Note) This specification discloses the following technologies:

[0058] (Item 1) A drive circuit for a three-phase DC motor, integrated into a single semiconductor substrate, A control unit capable of controlling a bridge circuit connected to a motor, A first power supply terminal that receives power for motor drive, A second power supply terminal that receives power for circuit control, A protective element connected between a first power line connected to the first power terminal and a second power line connected to the second power terminal, The system comprises a clamp circuit connected between the first power line and the second power line, The control unit maintains the reset state immediately after the power to the drive circuit is turned on if the potential difference between the first power line and the second power line is greater than or equal to a predetermined value, and releases the reset state if the potential difference is less than the predetermined value. Drive circuit.

[0059] (Item 2) The control unit, while the power to the drive circuit is turned on, keeps the reset state released regardless of the potential difference after the reset state is released, as described in item 1 of the drive circuit.

[0060] (Item 3) The protection element includes a protection diode having a forward direction from the second power line to the first power line, The clamp circuit includes a set of a clamp diode having a forward direction from the first power line to the second power line and a Zener diode having a reverse direction from the first power line to the second power line, connected in series. The drive circuit described in item 1 or 2.

[0061] (Item 4) The protection element includes a first protection diode having a forward direction from the second power line toward the first power line, and a second protection diode connected in series with the first protection diode and having a forward direction toward the second power line. The clamping circuit is A first set comprising a first clamp diode having a forward direction from the first power line to the second power line and a first Zener diode having a reverse direction from the first power line to the second power line, connected in series, The system includes a second set of a second clamp diode having a forward direction from the second power line to the first power line and a second Zener diode having a reverse direction from the second power line to the first power line, connected in series, The first set and the second set are connected in parallel to each other. The drive circuit described in item 1 or 2. [Explanation of Symbols]

[0062] D1, D2 diodes 100 Systems 102 Motor 200, 200A, 200B drive circuit 210, 210A Control Unit 220 Pre-driver 230 Bridge Circuit 240 First power line 242 Second power line 244 Grounding line 250, 250A protection element 252 protection diodes 252A First protection diode 254 Second protection diode 260, 260A clamp circuit 262 clamp diodes 262A First clamp diode 264 Zener Diode 264A First Zener Diode 266 Second clamp diode 268 Second Zener Diode 270 Potential difference detection unit 300 Systems 400 drive circuit 410 Control Unit

Claims

1. A drive circuit for a three-phase DC motor, which is integrated into a single semiconductor substrate, A control unit capable of controlling a bridge circuit connected to a motor, A first power supply terminal that receives power for motor drive, A second power supply terminal that receives power for circuit control, A protective element is connected between a first power line connected to the first power terminal and a second power line connected to the second power terminal, The system comprises a clamp circuit connected between the first power line and the second power line, The control unit maintains the reset state immediately after the power to the drive circuit is turned on if the potential difference between the first power line and the second power line is greater than or equal to a predetermined value, and releases the reset state if the potential difference is less than the predetermined value. Drive circuit.

2. The drive circuit according to claim 1, wherein the control unit keeps the reset state released regardless of the potential difference after the release of the reset state while the power to the drive circuit is turned on.

3. The protection element includes a protection diode having a forward direction from the second power line to the first power line, The clamp circuit includes a set of a clamp diode having a forward direction from the first power line to the second power line and a Zener diode having a reverse direction from the first power line to the second power line, connected in series. The drive circuit according to claim 1 or 2.

4. The protection element includes a set in which a first protection diode having a forward direction from the second power line toward the first power line and a second protection diode having a forward direction from the first power line toward the second power line are connected in series. The clamping circuit is A first set comprising a first clamp diode having a forward direction from the first power line to the second power line and a first Zener diode having a reverse direction from the first power line to the second power line, connected in series, The system includes a second set of a second clamp diode having a forward direction from the second power line toward the first power line and a second Zener diode having a reverse direction toward the first power line, connected in series, The first set and the second set are connected in parallel to each other. The drive circuit according to claim 1 or 2.

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