Three-phase DC motor drive circuit, cooling device and electronic device using the same

Abstract

To provide a driving circuit capable of stopping operation in short time.SOLUTION: A bridge circuit 230 is connected to a fan motor 102. A control logic circuit 210, in response to a stop instruction, fixes an upper arm of a source phase off where current outflows in the bridge circuit 230, and keeps states of other upper arms and lower arms (φ11). The control logic circuit 210 fixes the upper arms and the lower arms of all the bridge circuit 230 off (φ12).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to fan motor driving technology. [Background technology]

[0002] Fan motors for temperature control are installed in information processing devices such as laptop computers, desktop computers, and workstations, entertainment devices such as game consoles, projectors and security cameras, home appliances such as microwave ovens and refrigerators, automobiles, etc. Fan motors are used to blow air directly onto heat sources such as CPUs (Central Processing Units), or to draw fresh air from the outside to the inside of a housing, or to exhaust warm air.

[0003] In some applications where there is a strong demand for reducing power consumption, fan motors are frequently switched between stopped and rotating. When considering reducing the power consumption of the entire system, the fan motor drive circuit is required to stop operation as soon as possible when it receives a stop command from the upper controller. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-191992 Summary of the Invention [Problem to be solved by the invention]

[0005] Now, suppose that when the drive circuit receives a stop command, it immediately turns off all arms of the bridge circuit connected to the fan motor. If a coil current flows through the fan motor at this time, this coil current returns to the power supply side, causing the power supply voltage to jump up. This jump in power supply voltage can have a negative effect on the reliability of the circuit elements that make up the bridge circuit and other circuits. In addition, the jump in power supply voltage can cause the overvoltage protection to malfunction.

[0006] It should be noted that the same problem is not limited to fan motors, but may occur in a variety of applications.

[0007] The present disclosure has been made in consideration of the above problems, and one objective of an embodiment of the present disclosure is to provide a motor drive circuit that can stop operation in a short period of time. [Means for solving the problem]

[0008] An embodiment of the present disclosure relates to a drive circuit for a three-phase DC motor. The drive circuit includes a control logic circuit that controls a bridge circuit connected to the three-phase DC motor. In response to a stop command, the control logic circuit fixes an upper arm of a source phase from which current flows in the bridge circuit to off, maintains the states of the other upper arms and lower arms, and then fixes the upper arms and lower arms of all phases of the bridge circuit to off.

[0009] Another embodiment of the present disclosure also relates to a drive circuit for a three-phase DC motor. The drive circuit includes a control logic circuit that controls a bridge circuit connected to the three-phase DC motor. In response to a stop command, the control logic circuit fixes the lower arm of the sink phase into which current flows in the bridge circuit to off, and then fixes the upper arms and lower arms of all phases of the bridge circuit to off.

[0010] Any combination of the above components, and mutual substitution of the components and expressions of the present disclosure between methods, devices, systems, etc. are also valid aspects of the present invention. Effect of the Invention

[0011] According to an aspect of the present disclosure, the motor drive circuit can be stopped in a short period of time. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a circuit diagram of a cooling device including a drive circuit according to an embodiment. [Diagram 2] FIG. 2 is a waveform diagram showing the three-phase output and the coil current of the drive circuit in 180-degree conduction. [Diagram 3] 3(a) and (b) are diagrams showing the current paths of the bridge circuit. [Figure 4] 4(a) to (c) are circuit diagrams illustrating the first stop sequence. [Diagram 5] FIG. 5 is a waveform diagram illustrating the first stop sequence in the 120-degree energization control. [Figure 6] FIG. 6 is a waveform diagram illustrating the first stop sequence in the 150-degree energization control. [Figure 7] 7(a) to (c) are circuit diagrams illustrating the second stop sequence. [Figure 8] FIG. 8 is a waveform diagram illustrating the second stop sequence in the 120-degree energization control. [Figure 9] FIG. 9 is a waveform diagram illustrating the second stop sequence in the 150-degree energization control. [Figure 10] 10(a) to (c) are circuit diagrams illustrating the third stop sequence. [Figure 11] FIG. 11 is a waveform diagram of the two-phase modulation lower type of 180-degree conduction control. [Figure 12] 12(a) to (c) are circuit diagrams illustrating the fourth stop sequence. [Figure 13] FIG. 13 is a waveform diagram of the two-phase modulation up / down method of 180-degree conduction control. [Figure 14] 14(a) to (c) are circuit diagrams illustrating the fourth stop sequence. [Figure 15] FIG. 15 is a waveform diagram of the two-phase modulation up / down method of the 180-degree conduction control. [Figure 16] FIG. 16 is a perspective view of a computer equipped with a cooling device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Overview of the embodiment) A summary of some exemplary embodiments of the present disclosure will be described. This summary is intended to provide a simplified summary of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the detailed description that follows, and is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not intended to be a comprehensive overview of all possible embodiments, nor is it intended to limit essential components of the embodiments. For convenience, the term "one embodiment" may be used to refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed in this specification.

[0014] A drive circuit for a three-phase DC motor according to one embodiment includes a control logic circuit that controls a bridge circuit connected to the three-phase DC motor. In response to a stop command, the control logic circuit fixes off an upper arm of a source phase from which current flows in the bridge circuit, maintains the states of the other upper arms and lower arms, and then fixes off the upper arms and lower arms of all phases of the bridge circuit.

[0015] With this configuration, by fixing the upper arm of the source phase, from which current flows out of the bridge circuit, off, a loop is formed that includes multiple lower arms and the motor coil. Then, by passing a coil current through this loop, the coil current can be reduced in a short time. Then, after the coil current becomes sufficiently small, all arms are turned off, thereby preventing a jump in the power supply voltage.

[0016] In one embodiment, the control logic circuit can control a three-phase DC motor with wide-angle energization control, and a predetermined width starting from switching of a sink phase into which current flows in a bridge circuit may be defined as a first prohibited section. When a stop command is detected during the first prohibited section in the wide-angle energization control, the control logic circuit may wait for the end of the first prohibited section and fix the upper arm of the source phase into which current flows out in the bridge circuit to be off. By avoiding the first prohibited section, it is possible to prevent the coil current from flowing into the power supply line via the body diode (freewheel diode) of the upper arm.

[0017] In one embodiment, when the control logic circuit detects a stop command during the first prohibited section in the wide-angle energization control, the control logic circuit may fix the lower arm of the sink phase into which current flows in the bridge circuit to off, and then fix the upper arms and lower arms of all phases of the bridge circuit to off. Fixing the lower arm of the sink phase of the bridge circuit to off forms a loop including multiple upper arms and the coil of the motor. Then, by passing a coil current through this loop, the coil current can be reduced in a short time. Then, by turning off all the arms after the coil current becomes sufficiently small, it is possible to prevent a jump in the power supply voltage. In this case, there is an advantage that it is not necessary to wait for the end of the first prohibited section. In this specification, the "wide-angle energization control" refers to control in which the energization angle is 120 degrees or more and less than 180 degrees, and includes control of any energization angle such as 135-degree energization control and 150-degree energization control in addition to 120-degree square wave control.

[0018] In one embodiment, the control logic circuit may be capable of controlling a three-phase DC motor in a two-phase modulation mode with 180-degree conduction control, and a period in which the number of source phases is two may be defined as a first permitted interval. When the control logic circuit detects a stop command outside the first permitted interval during operation in the two-phase modulation mode, the control logic circuit may wait until the next first permitted interval and fix the upper and lower arms of the two source phases to off.

[0019] The first permitted section may have a predetermined width including the timing at which the output voltages of the two phases outputting a non-low voltage cross. By defining the first permitted section around the timing at which the output voltages of the two phases cross, the possibility that the number of source phases becomes 1 during the first permitted section can be reduced.

[0020] In one embodiment, the control logic circuit may be capable of controlling a three-phase DC motor in a two-phase modulation up / down method with 180-degree conduction control, and a period in which the number of source phases is two may be defined as the second permitted section. When the control logic circuit detects a stop command outside the second permitted section during operation in the two-phase modulation up / down method, the control logic circuit may wait until the next second permitted section and fix the upper arms and lower arms of the two phases from which current flows out of the bridge circuit to be off.

[0021] The second permitted section may have a predetermined width including the timing at which the output voltages of the two phases outputting a non-low voltage cross. By defining the second permitted section around the timing at which the output voltages of the two phases cross, the possibility that the number of source phases will be 1 during the second permitted section can be reduced.

[0022] A drive circuit for a three-phase DC motor according to one embodiment includes a control logic circuit that controls a bridge circuit connected to the three-phase DC motor. In response to a stop command, the control logic circuit fixes the lower arm of the sink phase into which current flows in the bridge circuit to off, and then fixes the upper arms and lower arms of all phases of the bridge circuit to off.

[0023] In this configuration, a loop including multiple upper arms and the motor coil is formed by fixing the lower arm of the sink phase into which current flows in the bridge circuit to off. Then, by passing a coil current through this loop, the coil current can be reduced in a short time. Then, after the coil current becomes sufficiently small, all arms are turned off, thereby preventing a jump in the power supply voltage.

[0024] In one embodiment, the control logic circuit may be capable of controlling a three-phase DC motor with wide-angle energization control, and a predetermined width starting from switching of an upper arm of a source phase from which a current flows out of a bridge circuit may be defined as a second prohibited section. When a stop command is detected during the second prohibited section in the wide-angle energization control, the control logic circuit may wait for the end of the second prohibited section and fix the lower arm of the sink phase to off.

[0025] By avoiding the second prohibited section, the coil current can be prevented from flowing into the power line via the body diode (freewheel diode) of the lower arm.

[0026] In one embodiment, the control logic circuit is capable of controlling a three-phase DC motor with a two-phase modulation up / down method with 180-degree energization control, a period during which current flows in from two phases is defined as a third permitted section, and when the control logic circuit detects a stop command outside the third permitted section while operating in the two-phase modulation up / down method, it may wait until the next third permitted section and fix the upper arms and lower arms of the two phases into which current flows in the bridge circuit to off.

[0027] In one embodiment, the third permission section may have a predetermined width including the timing at which the output voltages of the two phases outputting non-HIGH voltages cross each other. By defining the third permission section around the timing at which the output voltages of the two phases cross each other, the possibility that current is flowing out of the two phases outputting non-LOW voltages can be reduced.

[0028] In one embodiment, the drive circuit may further include a bridge circuit.

[0029] In one embodiment, the driving circuit may be monolithically integrated on a single semiconductor substrate. "Monolithic integration" includes cases where all of the circuit components are formed on a semiconductor substrate, and cases where the main components of the circuit are monolithically integrated, and some resistors and capacitors for adjusting the circuit constants may be provided outside the semiconductor substrate. By integrating the circuit on a single chip, the circuit area can be reduced and the characteristics of the circuit elements can be kept uniform.

[0030] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing are given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, the embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0031] In this specification, "a state in which component A is connected to component B" includes not only a case in which component A and component B are directly physically connected to each other, but also a case in which component A and component B are indirectly connected to each other via other components that do not substantially affect the electrical connection state between them or that do not impair the function or effect achieved by their combination.

[0032] Similarly, "a state in which component C is provided between components A and B" includes not only the case in which components A and C, or components B and C, are directly connected to each other, but also the case in which they are indirectly connected to each other via other components that do not substantially affect the electrical connection between them or that do not impair the functions or effects achieved by their combination.

[0033] 1 is a circuit diagram of a cooling device 100 including a drive circuit 200 according to an embodiment. The cooling device 100 includes a fan motor 102 and a drive circuit 200. The fan motor 102 is a three-phase brushless DC motor, and includes a U-phase coil L U , V-phase coil L V , W-phase coil L WThe driving circuit 200 includes a coil L of the fan motor 102. U ~L W The drive signal V U ~V W In response to this, the fan motor 102 is driven.

[0034] The driving circuit 200 is a functional IC integrated on a single semiconductor substrate, and includes a control logic circuit 210, a pre-driver 220, a bridge circuit 230, and a position detection circuit 240. The driving circuit 200 includes an enable terminal EN, and is switched between operating and stopped in response to a signal supplied to the enable terminal EN.

[0035] The bridge circuit 230 is a three-phase inverter to be driven, and has a U-phase leg, a V-phase leg, and a W-phase leg. The #-phase (#=U, V, W) leg is an upper arm Q #-H and lower arm Q #-L Each of the upper arm and the lower arm includes a switching element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an IGBT, or a bipolar transistor, and a freewheeling diode (also called a flywheel diode) connected in parallel with the switching element. When a MOSFET is used as the switching element as in FIG. 1, its body diode (not shown) serves as the freewheeling diode.

[0036] A power supply line 232 of the bridge circuit 230 is connected to a power supply terminal (power supply pin) VCC, and a power supply voltage is supplied from the outside. A ground line 234 of the bridge circuit 230 is grounded. A power supply voltage V CC may be provided.

[0037] The position detection circuit 240 detects the position of the rotor of the fan motor 102. For example, the position detection circuit 240 may be a back electromotive force detection circuit that detects the rotor position based on the back electromotive force generated at the coil end of the fan motor 102. Alternatively, the position detection circuit 240 may be a Hall detection circuit that detects the rotor position based on the output of a Hall element attached to or embedded in the fan motor 102. The position detection circuit 240 may be any known technology, and its configuration and type are not limited. The position detection circuit 240 outputs a position detection signal POS that indicates the rotor position.

[0038] The control logic circuit 210 controls the bridge circuit 230 connected to the three-phase DC motor in response to the output POS of the position detection circuit 240. Specifically, when an enable signal input to an enable terminal EN indicates an enable state, the control logic circuit 210 generates a control signal Sctrl to rotate the fan motor 102. The control signal Sctrl is U-H ,Q V-H ,Q W-H and lower arm Q U-L ,Q V-L ,Q W-L It may include six signals indicating whether the following is on or off:

[0039] Although not shown in FIG. 1, the control logic circuit 210 may change the target rotation speed in response to an external rotation speed control signal or an output signal from a temperature detection element.

[0040] The control method and circuit configuration of the control logic circuit 210 are not particularly limited, and may be any known technology. Specifically, the control logic circuit 210 may control the fan motor 102 by wide-angle energization control with an energization angle of 120 degrees or more and less than 180 degrees (e.g., 120 degrees, 135 degrees, 150 degrees, etc.), or may control the fan motor 102 by 180-degree energization control (also called sine wave drive). The control logic circuit 210 may perform wide-angle energization control (e.g., 120-degree energization control) immediately after start-up when the rotation speed of the fan motor 102 is low, and perform 180-degree energization control after the rotation speed of the fan motor 102 has stabilized.

[0041] The pre-driver 220 controls the upper arm Q of the bridge circuit 230 based on the control signal Sctrl generated by the control logic circuit 210. U-H ,Q V-H ,Q W-H and lower arm Q U-L ,Q V-L ,Q W-L Drives.

[0042] In this embodiment, the control logic circuit 210 executes a characteristic stop sequence in response to a stop instruction to the drive circuit 200. The stop instruction is typically associated with a transition of an enable signal input to an enable terminal EN to low, but is not limited to this, and there may be a terminal for inputting a stop signal in addition to the enable terminal EN.

[0043] Problems that may occur when the operation of the drive circuit 200 stops will be described.

[0044] 2 is a waveform diagram showing the three-phase output and coil current of the drive circuit in 180-degree conduction. Hatching indicates a state in which a high voltage (non-zero) is output. When a current flows out of the bridge circuit 230 toward a coil of a certain phase (source), the coil current is positive, and conversely, when a current flows in from a coil of a certain phase to the bridge circuit 230 (sink), the coil current is negative.

[0045] Figures 3(a) and (b) are diagrams showing the current path of the bridge circuit 230. Figure 3(a) shows the state of the arms and the current path of the bridge circuit 230 in the time section Ta in Figure 2. In the state of Figure 3(a), a current flows from the power line to the ground line via the upper arms of the U and W phases, the motor coil, and the lower arm of the V phase.

[0046] Fig. 3(b) shows the current path when all arms are turned off simultaneously from the state shown in Fig. 3(a). In this state, current flows from the ground line through the U-phase and W-phase body diodes, the motor coil, and the V-phase body diode to the power supply line 232. As a result, the potential of the power supply line 232 jumps up significantly.

[0047] A stop sequence capable of suppressing a jump in the power supply line 232 of the bridge circuit 230 will be described below.

[0048] (First stop sequence) When the control logic circuit 210 detects a stop command, it fixes the upper arm of the source phase from which the current of the bridge circuit 230 flows out to OFF, and maintains the states of the other upper arms and lower arms (first state φ 11 After that, the control logic circuit 210 fixes the upper and lower arms of all phases of the bridge circuit 230 to the off state (second state φ 12 ).

[0049] 4(a) to 4(c) are circuit diagrams for explaining the first stop sequence. FIG. 4(a) shows a normal state before a stop command is issued to the bridge circuit 230 in the wide-angle energization control. Here, the U-phase upper arm Q U-H and V-phase lower arm Q V-L is on, and U-phase coil L U A positive coil current flows through the V-phase coil L V A negative coil current flows in the

[0050] FIG. 4B shows the first state φ of the bridge circuit 230 after the detection of the stop command. 11 When a stop command is detected (FIG. 4(a)), a current flows out of the U-phase output of the bridge circuit 230, so that the U-phase becomes the source phase. Therefore, when the control logic circuit 210 detects a stop command, it turns the upper arm Q U-H The control logic circuit 210 maintains the previous state (FIG. 4(a)) for the other upper arms and lower arms.

[0051] The first state φ in Fig. 4(b) 11 In this case, the body diode D U-L , U-phase coil L U , V-phase coil L V and the lower arm Q of the V phase V-L A loop is formed that includes the coil current passing through the ground line 234 and returning to the ground line 234. As the coil current flows through this loop, it decreases in a short time. Typically, the coil current decreases to substantially zero on a time scale equivalent to about 30 to 60 electrical degrees, or at most 90 electrical degrees.

[0052] The bridge circuit 230 is in the first state φ 11 When the coil current becomes sufficiently small, the second state φ 12 The second state φ 12 So, all upper arms Q U-H ,Q V-H ,Q W-H and all lower arm Q U-L ,Q V-L ,Q W-L is fixed to off. The coil current being sufficiently small means that even if the coil current flows into the power supply line 232, the increase in the voltage of the power supply line is small enough that it does not cause a problem.

[0053] The control logic circuit 210 is in the first state φ 11 After a predetermined time has elapsed since the transition to the second state φ 12 Alternatively, the control logic circuit 210 may transition to the first state φ 11 After the time corresponding to a predetermined electrical angle has elapsed since the transition to the second state φ 12 may transition to

[0054] Alternatively, state transitions may be permitted at intervals of a predetermined electrical angle (30°), such as electrical angles of 0°, 30°, 60°, 90°, . . . , 300°, 330°, and 360°. 11For example, assume that the minimum duration of the electric angle φ is set to 30°. In this case, if a stop command is received at the timing of 20°, the state immediately transitions to the first state, and the state transitions to the second state φ at the next transition permitted timing of 60°, not at 50° after 30°. 12 may transition to

[0055] Alternatively, if a stop command is received at the timing of 20°, the first state φ 11 Then, at the transition permission timing of 60° after 30° has elapsed, the second state φ 12 may transition to

[0056] Alternatively, in the case where the drive circuit 200 is provided with a circuit for detecting the coil current, when the detected current amount falls to a threshold value near zero, the drive circuit 200 enters the second state φ 12 may transition to

[0057] 5 is a waveform diagram illustrating a first stop sequence in the 120-degree conduction control, in which a predetermined width starting from the switching of the sink phase into which the current flows is surrounded by a dashed line.

[0058] Fig. 6 is a waveform diagram illustrating the first stop sequence in the 150-degree conduction control. As in Fig. 5, a predetermined width starting from the switching of the sink phase into which the current flows is enclosed by a dashed line.

[0059] 5 and 6, if the upper arm is turned off in accordance with the first shutdown sequence during the interval surrounded by the dashed line, the coil current will flow into the power line. Therefore, in the first shutdown sequence, the range surrounded by the dashed line is defined as the first prohibited interval Ta.

[0060] In wide-angle energization control such as 120-degree energization control or 150-degree energization control, when a stop command is detected during the first prohibited section Ta, the control logic circuit 210 waits for the end of the first prohibited section Ta and then switches to the first state φ 11, and fixes to off the upper arm of the source phase from which current flows out of the bridge circuit 230. By providing the first prohibited section Ta, it is possible to prevent the coil current from flowing into the power supply line.

[0061] The above is the first stopping sequence. According to this stopping sequence, the first state φ 11 After the coil current is reduced, the coil current is reduced in the second state φ 12 By transitioning to the second state φ, it is possible to prevent current from flowing into the power line. 12 After this, the entire drive circuit 200 is disabled, making it possible to reduce power consumption significantly.

[0062] This stop sequence should not be confused with braking. Braking is a control that is primarily aimed at stopping the rotation of the rotor, and the coil current continues to flow through the coil. In contrast, the stop sequence in this embodiment is a control that is primarily aimed at reducing the coil current, and if the coil current is reduced, the second state φ 12 The rotor may continue to spin freely at this time. The brake and stop sequence makes a big difference in the situation where a start command is received immediately after a stop command is received.

[0063] When the drive circuit 200 receives an operation start instruction (enable of the enable terminal), it starts rotating the fan motor 102 according to a predetermined startup sequence. Generally, the startup sequence first monitors whether the fan motor 102 is rotating idly, and at this time, all arms of the bridge circuit 230 are turned off.

[0064] When stopping by braking, there is a possibility that the coil current will remain when the start command is received. In this case, if all arms of the bridge circuit 230 are turned off to detect slipping, the remaining current may flow into the power line, inducing a voltage jump.

[0065] On the other hand, when the stop sequence is performed, all the arms are turned off, so there is no need to transition the state of the bridge circuit 230 to detect slippage. Also, because the coil current is very small, there is no need to worry about voltage jumps on the power line.

[0066] (Second stop sequence) When the control logic circuit 210 detects a stop command, it fixes the lower arm of the sink phase into which the current of the bridge circuit 230 flows (referred to as the sink phase) to off, and maintains the states of the other upper and lower arms (first state φ 21 After that, the control logic circuit 210 fixes the upper and lower arms of all phases of the bridge circuit 230 to the off state (second state φ 22 ).

[0067] 7(a) to (c) are circuit diagrams for explaining the second stop sequence. FIG. 7(a) shows a normal state before a stop command is issued to the bridge circuit 230 in the wide-angle energization control. Here, the U-phase upper arm Q U-H and V-phase lower arm Q V-L is on, and U-phase coil L U A positive coil current flows through the V-phase coil L V A negative coil current flows in the

[0068] FIG. 7B shows the first state φ of the bridge circuit 230 after the detection of the stop command. 21 When a stop command is detected (FIG. 7(a)), a current flows into the bridge circuit 230 from the V-phase output, so that the V-phase becomes the sink phase. Therefore, when the control logic circuit 210 detects a stop command, it turns the lower arm Q V-L The control logic circuit 210 maintains the previous state (FIG. 7(a)) for the other upper arms and lower arms.

[0069] The first state φ in Fig. 7(b) 21 In this case, the power supply line 232 is the starting point, and the upper arm of the U phase, the U phase coil L U, V-phase coil L V and the upper arm Q of the V phase V-H Body diode D V-H A loop is formed that includes the coil current passing through the power supply line 232 and returning to the power supply line 232. As the coil current flows through this loop, it decreases in a short time. Typically, the coil current decreases to substantially zero on a time scale equivalent to about 30 to 60 electrical degrees, or at most 90 electrical degrees.

[0070] The bridge circuit 230 is in the first state φ 21 When the coil current becomes sufficiently small, the second state φ 22 The second state φ 22 So, all upper arms Q U-H ,Q V-H ,Q W-H and all lower arm Q U-L ,Q V-L ,Q W-L is fixed to off.

[0071] In the second stopping sequence, the first state φ 21 to the second state φ 22 The method of switching to the first stop sequence is the same as that described in the first stop sequence.

[0072] 8 is a waveform diagram illustrating a second stop sequence in the 120-degree conduction control, in which a predetermined width having a starting point of switching of the source phase from which the current flows out is surrounded by a dashed line.

[0073] 9 is a waveform diagram illustrating the second stop sequence in the 150-degree conduction control, in which a predetermined width starting from the switching of the source phase from which the current flows out is surrounded by a dashed line.

[0074] If the lower arm is turned off in accordance with the second shutdown sequence during the section enclosed by the dashed line in Figure 8 or Figure 9, the coil current will flow into the power line. Therefore, in the second shutdown sequence, the range enclosed by the dashed line is defined as a second prohibited section Tb.

[0075] In wide-angle energization control such as 120-degree energization control or 150-degree energization control, when a stop command is detected during the second prohibited section Tb, the control logic circuit 210 waits for the end of the second prohibited section Tb and then switches to the first state φ 21 , and the lower arm of the sink phase into which the current of the bridge circuit 230 flows is fixed to off. By providing the second prohibited section Tb, it is possible to prevent the coil current from flowing into the power supply line.

[0076] (Combination of the first and second stop sequences) The second stop sequence and the first stop sequence can be used in combination. For example, the first stop sequence can be the main sequence and the second stop sequence can be the sub sequence. In this case, if a stop instruction is detected outside the first prohibited section Ta, the first stop sequence can be executed, and if a stop instruction is detected within the first prohibited section Ta, the second stop sequence can be executed.

[0077] Conversely, the second stop sequence may be the main sequence and the first stop sequence may be the sub sequence. In this case, if a stop command is detected outside the second prohibited section Tb, the second stop sequence may be executed, and if a stop command is detected within the second prohibited section Tb, the first stop sequence may be executed.

[0078] By combining two stop sequences, the first state φ 11 Or the first state φ 21 It is possible to transition to

[0079] (Third stop sequence) The control logic circuit 210 can control a three-phase DC motor by a two-phase modulation method of 180-degree conduction control. In the third stop sequence, the state of the source phase is switched first, as in the first stop sequence.

[0080] 10(a) to (c) are circuit diagrams for explaining the third stop sequence. Fig. 10(a) shows a normal state before a stop command is issued for the bridge circuit 230 operating under 180-degree conduction control (sine wave drive). In the two-phase modulation method, one phase of the three-phase output of the bridge circuit 230 outputs a low voltage (0V), and the remaining two phases output non-low voltages. The upper arm and the lower arm of the phase outputting the non-low voltage are PWM-controlled and switched complementarily so as to obtain the equivalent output voltage shown in Fig. 11.

[0081] In FIG. 10(a), the V phase outputs a low voltage, and the U and W phases output non-low voltages by PWM control. U and W-phase coil L W A positive coil current flows through the V-phase coil L V A negative coil current flows in the

[0082] FIG. 10B shows the first state φ of the bridge circuit 230 after the detection of the stop command. 31 When a stop command is detected (FIG. 10(a)), current flows out from the U-phase output and W-phase output of the bridge circuit 230, so the U-phase and W-phase become source phases, and the number of source phases is two. When the control logic circuit 210 detects a stop command, it turns on the upper arms Q of the U-phase and W-phase, which are the source phases. U-H , Q W-H Turn off the lower arm Q U-L , Q W-L In other words, the outputs of the U and W phases are set to high impedance. The control logic circuit 210 keeps the remaining V phase in the output state just before (FIG. 10(a)), that is, the low output (upper arm Q V-H is off, lower arm Q V-L (ON) shall be maintained.

[0083] The first state φ in Fig. 10(b) 31 In this case, a lower loop is formed starting from the ground line 234 and passing through the lower arm transistor or the lower arm body diode. When the coil current flows through this loop, the coil current decreases in a short time.

[0084] The bridge circuit 230 is in the first state φ 31 When the coil current becomes sufficiently small, the second state φ 32 The second state φ 32 So, all upper arms Q U-H ,Q V-H ,Q W-H and all lower arm Q U-L ,Q V-L ,Q W-L is fixed to off.

[0085] In the third stopping sequence, the first state φ 31 to the second state φ 32 The method of transition to is the same as that described in the first stop sequence.

[0086] Figure 11 is a waveform diagram of the two-phase modulation lower type of 180-degree conduction control. From the top, Figure 11 shows the coil current, equivalent output voltage, the state of the upper arm and lower arm of each phase, and the state of the stop command (EN\) bridge circuit. The period surrounded by dashed lines is the period when current flows out from two phases, that is, the period when the number of source phases is two. In other periods, the number of source phases is one.

[0087] In the third shutdown sequence, in the section (outside the dashed line) where the number of source phases is 1, the bridge circuit 230 is switched to the first state φ 31 , no loop is formed and current flows into the power line. Therefore, in the third shutdown sequence, the first permission section Tc is defined within the area surrounded by the dashed line. If the first permission section Tc is defined to coincide with the dashed line, even a slight shift in timing will result in the number of source phases being 1 in the first permission section Tc. Therefore, although the first permission section Tc may coincide completely with the dashed line, it is preferable to define it narrower than that.

[0088] For example, the first permission interval Tc may be a predetermined width including the timing at which the output voltages of two phases outputting a non-low voltage cross (electrical angles of 60°, 180°, and 300° in this example), and this predetermined width is set to be narrower than 60°. By setting the first permission interval Tc centered on the timing at which the output voltages of two phases cross, it is possible to reduce the possibility that the number of source phases will be 1 during the first permission interval Tc.

[0089] In the above explanation, the section where the number of source phases is two is indirectly detected based on the output voltage of two phases, but this is not limited to the above. The coil currents of three phases may be monitored to directly detect the section where the number of source phases is two. The currents of the three phases may be detected individually, or, taking advantage of the fact that the sum of the three-phase currents is zero, only the currents of two phases may be detected and the current of the remaining phase may be calculated.

[0090] As shown in FIG. 11, when the control logic circuit 210 detects a stop command outside the first permission interval Tc at time t0 while operating in the two-phase modulation up / down method, the control logic circuit 210 may wait until time t1 included in the next first permission interval Tc, and fix the upper and lower arms of the two source phases outputting a non-low voltage to off.

[0091] (4th stop sequence) The control logic circuit 210 can control a three-phase DC motor by a two-phase modulation up / down method of 180-degree energization control. In the two-phase modulation up / down method, one of the three-phase outputs of the bridge circuit 230 outputs a low voltage (0 V) and the remaining two phases output a non-low voltage, or one of the three-phase outputs outputs a high voltage (V CC ) while the remaining two phases are outputting non-high voltages. In the fourth shutdown sequence, similar to the third shutdown sequence, the states of the two source phases are switched in advance during the period when one phase is outputting a low voltage.

[0092] 12(a) to 12(c) are circuit diagrams illustrating the fourth stop sequence. Fig. 12(a) shows a normal state before a stop instruction is issued for the bridge circuit 230 operating under 180-degree energization control (sine wave drive).

[0093] In FIG. 12(a), the V phase outputs a low voltage. In the U and W phases, which output non-low voltages, the upper and lower arms are PWM-controlled and switched complementarily to obtain the equivalent output voltage shown in FIG. 13. The U phase coil L U and W-phase coil L W A positive coil current flows through the V-phase coil L V A negative coil current flows in the

[0094] FIG. 12B shows the first state φ of the bridge circuit 230 after the detection of the stop command. 41 When a stop command is detected (FIG. 12(a)), current flows out from the U-phase output and W-phase output of the bridge circuit 230, so the U-phase and W-phase become source phases, and the number of source phases is two. When the control logic circuit 210 detects a stop command, it turns on the upper arms Q of the U-phase and W-phase, which are the source phases. U-H , Q W-H Turn off the lower arm Q U-L , Q W-L In other words, the outputs of the U and W phases are set to high impedance. The control logic circuit 210 keeps the output state of the remaining phase, the V phase, in the previous state (FIG. 12(a)), that is, the low output (upper arm Q V-H is off, lower arm Q V-L (ON) shall be maintained.

[0095] The first state φ in Fig. 12(b) 41 In this case, a lower loop is formed starting from the ground line 234 and passing through the lower arm transistor or the lower arm body diode. When the coil current flows through this loop, the coil current decreases in a short time.

[0096] The bridge circuit 230 is in the first state φ 41 When the coil current becomes sufficiently small, the second state φ 42 The second state φ 42 So, all upper arms Q U-H,Q V-H ,Q W-H and all lower arm Q U-L ,Q V-L ,Q W-L is fixed to off.

[0097] In the fourth stopping sequence, the first state φ 31 to the second state φ 32 The method of transition to is the same as that described in the first stop sequence.

[0098] Figure 13 is a waveform diagram of the two-phase modulation up / down method of 180-degree conduction control. The period surrounded by the dashed line is the period when current flows out from two phases, that is, the period when the number of source phases is 2. In other periods, the number of source phases is 1.

[0099] In the fourth shutdown sequence, in the section (outside the dashed line) where the number of source phases is 1, the bridge circuit 230 is switched to the first state φ 41 , no loop is formed and current flows into the power line. Therefore, in the fourth shutdown sequence, the second permission section Td is defined within the area surrounded by the dashed line. If the second permission section Td is defined to coincide with the dashed line, even a slight shift in timing will result in the number of source phases being 1 in the second permission section Td. Therefore, although the second permission section Td may coincide completely with the dashed line, it is preferable to define it narrower than that.

[0100] For example, the second permission interval Td may be a predetermined width including the timing at which the output voltages of two phases outputting non-low voltages cross (electrical angles of 30°, 150°, and 270° in this example), and this predetermined width is set to be narrower than 60°. By setting the second permission interval Td centered on the timing at which the output voltages of two phases cross, it is possible to reduce the possibility that the number of source phases will be 1 during the second permission interval Td.

[0101] When the control logic circuit 210 detects a stop command outside the second permission interval Td while operating in the two-phase modulation upper and lower method, it waits until the next second permission interval Td and fixes the upper arm and the lower arm of the two source phases of the bridge circuit 230 to off.

[0102] (5th stop sequence) Similar to the fourth stop sequence, the control logic circuit 210 can control the three-phase DC motor with the two-phase modulation up / down method of 180-degree energization control. In the fifth stop sequence, contrary to the fourth stop sequence, the states of the two sink phases are switched in advance during the period when one phase is outputting a high voltage.

[0103] 14(a) to 14(c) are circuit diagrams illustrating the fourth stop sequence. Fig. 14(a) shows a normal state before a stop instruction is issued for the bridge circuit 230 operating under 180-degree energization control (sine wave drive).

[0104] In FIG. 14(a), the U phase outputs a high voltage. In the V and W phases, which output non-high voltages, the upper and lower arms are PWM-controlled and switched complementarily to obtain the equivalent output voltage shown in FIG. 15. The U phase coil L U A positive coil current flows through the V-phase coil L V and W-phase coil L W A negative coil current flows in the

[0105] FIG. 14B shows the first state φ of the bridge circuit 230 after the detection of the stop command. 51 When a stop command is detected (FIG. 14(a)), current flows from the V-phase output and W-phase output of the bridge circuit 230, so the V-phase and W-phase become sink phases, and the number of sink phases is two. When the control logic circuit 210 detects a stop command, it outputs the upper arms Q of the V-phase and W-phase, which are sink phases. V-H , Q W-H Turn off the lower arm Q V-L , Q W-LIn other words, the outputs of the V and W phases are set to high impedance. The control logic circuit 210 keeps the output state of the remaining U phase (FIG. 14(a)) in the previous state, that is, high output (upper arm Q U-H On, lower arm Q U-L (OFF).

[0106] The first state φ in FIG. 14(b) 51 In this case, a loop is formed that starts at the power supply line 232 and passes through the upper arm transistor or the upper arm body diode. When a coil current flows through this loop, the coil current decreases in a short time.

[0107] The bridge circuit 230 is in the first state φ 51 When the coil current becomes sufficiently small, the second state φ 52 The second state φ 52 So, all upper arms Q U-H ,Q V-H ,Q W-H and all lower arm Q U-L ,Q V-L ,Q W-L is fixed to off.

[0108] In the fifth stopping sequence, the second state φ 51 to the second state φ 52 The method of transition to is the same as that described in the first stop sequence.

[0109] Figure 15 is a waveform diagram of the two-phase modulation up / down method of 180-degree conduction control. The period surrounded by the dashed line is the period when current flows in from two phases, that is, the period when the number of sink phases is 2. In other periods, the number of sink phases is 1.

[0110] In the fifth stop sequence, in the section (outside the dashed line) where the number of sink phases is 1, the bridge circuit 230 is set to the first state φ 51, no loop is formed and current flows into the power line. Therefore, in the fifth shutdown sequence, the third permission interval Te is defined within the area surrounded by the dashed line. If the third permission interval Te is defined to coincide with the dashed line, even a slight shift in timing will result in the number of sink phases being one in the third permission interval Te. Therefore, although the third permission interval Te may completely coincide with the dashed line, it is preferable to define it narrower than that.

[0111] For example, the third allowed interval Te may be a predetermined width including the timing at which the output voltages of two phases outputting non-HIGH voltages cross, and this predetermined width is set to be narrower than 60°. By setting the third allowed interval Te around the timing at which the output voltages of two phases cross (electrical angles of 90°, 210°, and 330° in this example), it is possible to reduce the possibility that the number of sink phases will be 1 during the third allowed interval Te.

[0112] When the control logic circuit 210 detects a stop command outside the third permission interval Te while operating in the two-phase modulation up / down method, it waits until the next third permission interval Te and fixes the upper and lower arms of the two sink phases of the bridge circuit 230 to off.

[0113] (Combination of 4th and 5th stop sequences) The fourth stop sequence and the fifth stop sequence can be used in combination, and if a stop instruction is detected during the second permitted section Td, the fourth stop sequence may be executed, and if a stop instruction is detected during the third permitted section Te, the fifth stop sequence may be executed.

[0114] (Modification) The embodiment has been described above. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present invention. Such modifications will be described below.

[0115] In the embodiment, the control logic circuit 210, the pre-driver 220, and the bridge circuit 230 are integrated into one semiconductor chip, but this is not limited thereto. For example, the bridge circuit 230 may be configured with discrete elements. Furthermore, only the control logic circuit 210 may be an independent IC (Integrated Circuit).

[0116] (Application) Finally, the use of the drive circuit 200 will be described. Fig. 16 is a perspective view of a computer including a cooling device 100. The cooling device 100 includes a fan motor 102 and the drive circuit 200 of Fig. 1. The computer 500 includes a case 502, a CPU 504, a motherboard 506, a heat sink 508, and a plurality of cooling devices 100_1 and 100_2.

[0117] The CPU 504 is mounted on a motherboard 506. The heat sink 508 is in close contact with the upper surface of the CPU 504. The cooling device 100_1 is provided opposite the heat sink 508 and blows air onto the heat sink 508. The cooling device 100_2 is installed on the rear surface of the housing 502 and draws air from outside the housing 502 into the inside or exhausts air from the inside to the outside.

[0118] The cooling device 100 according to the embodiment can start the fan motor 102 in a short time, and therefore can quickly cool the object to be cooled.

[0119] The cooling device 110 can be mounted in various electronic devices such as a workstation, a notebook computer, a television, a refrigerator, etc., in addition to the computer 500 in FIG.

[0120] Furthermore, the application of the drive circuit 200 according to this embodiment is not limited to driving a fan motor, but can be used to drive various other motors.

[0121] The embodiments described using specific terms merely illustrate the principles and applications of the present invention, and many modifications and changes in arrangement are permitted in the embodiments without departing from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0122] 100 Cooling device 102 Fan motor 200 Drive circuit 210 Control logic circuit 220 Pre-driver 230 Bridge Circuit 240 Position detection circuit

Claims

1. A drive circuit for a three-phase DC motor, comprising: a control logic circuit for controlling a bridge circuit connected to the three-phase DC motor; the control logic circuit is capable of controlling the three-phase DC motor with wide-angle energization control; a predetermined width starting from a switching of a sink phase into which a current flows in the bridge circuit is defined as a first prohibited section; the control logic circuit, when detecting a stop command during the first prohibited section in the wide-angle energization control, fixes off the lower arm of a sink phase into which current flows in the bridge circuit, and then fixes off the upper arms and lower arms of all phases of the bridge circuit.

2. The control logic circuit is capable of controlling the three-phase DC motor in a two-phase modulation mode with 180-degree conduction control; A period in which the number of source phases is two is defined as a first permission section, 2. The drive circuit according to claim 1, wherein when the control logic circuit detects the stop instruction outside the first permitted interval during operation in the two-phase modulation method, the control logic circuit waits until the next first permitted interval and fixes the upper arm and the lower arm of the two source phases to off.

3. 3. The drive circuit according to claim 2, wherein the first permission section has a predetermined width including a timing at which the output voltages of the two phases outputting non-low voltages cross each other.

4. The control logic circuit is capable of controlling the three-phase DC motor by a two-phase modulation up / down method with 180-degree energization control; A period in which the number of source phases is two is defined as a second permission section, The drive circuit according to claim 2 or 3, characterized in that when the control logic circuit detects the stop instruction outside the second permitted interval during operation in the two-phase modulation upper and lower method, it waits until the next second permitted interval and fixes the upper arm and the lower arm of the two source phases to off.

5. 5. The drive circuit according to claim 4, wherein the second permission section has a predetermined width including a timing at which the output voltages of the two phases outputting non-low voltages cross each other.

6. 6. The drive circuit according to claim 1, further comprising the bridge circuit.

7. 7. The drive circuit according to claim 1, wherein the drive circuit is monolithically integrated on a single semiconductor substrate.

8. 8. The drive circuit according to claim 1, wherein the three-phase DC motor is a fan motor.

9. A fan motor; A drive circuit for driving the fan motor according to any one of claims 1 to 8; A cooling device comprising:

10. A processor; a fan motor for cooling the processor; A drive circuit for driving the fan motor according to any one of claims 1 to 8; An electronic device comprising:

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