JP2012016245A - Motor driving device and cooling device using the same, and method for generating rotational frequency signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor driving device which can generate rotational frequency signals for a six-pole motor.SOLUTION: In a motor driving device, a rotation detection signal S3 asserted for every electric angle of 60 degrees is generated by comparing electromotive force generated in each end of coils of star-connected U, V, and W phases with mid-point voltage generated in a common connection node of the three coils. A first counter 22 is reset every time the rotation detection signal S3 is asserted to measure a cycle of the rotation detection signal S3. A comparison part 24 generates a first signal S11 which is asserted every time a count value D1 of the first counter 22 matches a value D2 indicating 1/2 of the cycle measured earlier. A second counter 30 generates a rotation frequency signal FG which is asserted every time the rotation detection signal S3 and the first signal S11 are counted a prescribed number of times.

Description

  The present invention relates to a motor driving technique.

  A drive device that drives the motor generates a rotation number (FG) signal indicating the current rotation number of the motor. In the field of fan motors, this rotational speed signal is asserted twice for each motor rotation, that is, every 180 degrees of mechanical angle (also called motor angle) (level transition or edge is generated). It is common.

The three-phase motor has U-phase, V-phase, and W-phase coils that are star-connected. The driving device for the three-phase motor includes a comparator provided for each of the U-phase, V-phase, and V-phase coils, and coil voltages (back electromotive force) V _U , V _V , V _W generated at one end of the corresponding phase coil. Is compared with the midpoint voltage V _COM generated at the common connection node of the three coils. These comparators generate a rotation detection signal (also referred to as a back electromotive force detection signal) that is asserted every 60 degrees of electrical angle.

The number of poles of the motor to be driven varies from 4 poles, 6 poles, and 8 poles. FIG. 1 is a time chart showing counter electromotive forces V _U , V _V , and V _W generated in U-phase, V-phase, and V-phase coils, rotation detection signals, and 4-pole, 6-pole, and 8-pole rotation speed signals. .

Japanese Patent Laid-Open No. 5-137379 JP 2008-022692 A

  The rotational speed signal changes every 180 electrical degrees for a 4-pole motor and every electrical angle 360 degrees for an 8-pole motor. Therefore, in a 4-pole or 8-pole motor, a rotation speed signal can be generated by counting rotation detection signals asserted every 60 degrees of electrical angle.

  However, in a 6-pole motor, it is necessary to change the rotational speed signal every electrical angle of 270 degrees. That is, the rotation speed signal cannot be generated by counting the rotation detection signal as in the case of 4 poles or 8 poles. Conventionally, in order to generate a rotation speed signal of a 6-pole motor, it has been necessary to generate a signal equivalent to the rotation speed signal by calculation processing in a microcomputer outside the motor driving device.

  The present invention has been made in such a situation, and one of exemplary purposes of an embodiment thereof is to provide a motor driving device capable of generating a rotation speed signal suitable for a 6-pole motor.

  One embodiment of the present invention relates to a driving device for a three-phase six-pole motor. The motor drive device compares the back electromotive force generated at one end of each of the U, V, and W phase coils that are star-connected to the motor with the midpoint voltage that is generated at the common connection node of the three coils. A counter electromotive force detection circuit that generates a rotation detection signal that is asserted at a time, a first counter that is reset each time the rotation detection signal is asserted, and a count value of the first counter that measures the period of the rotation detection signal. A comparison unit that generates a first signal that is asserted each time it matches a value that represents a half of a previously measured period, and a rotation that is asserted each time a predetermined number of rotation detection signals and first signals are counted. A second counter for generating a number signal.

  The first signal is asserted with a period of 60 electrical degrees and a phase delayed by 30 electrical degrees with respect to the rotation detection signal. Therefore, by counting the first signal and the rotation detection signal, an electrical angle of 270 degrees can be detected, and a rotation speed signal suitable for a 6-pole motor can be generated.

The comparison unit may include a register that holds the latest period measured by the first counter, and a comparator that compares a half value of the period stored in the register with the count value of the first counter. Good.
In this case, the rotation detection signal can be updated every cycle, and the first signal can be generated following the change even when the rotation speed of the motor changes abruptly.

The second counter may include a combining unit that receives the rotation detection signal and the first signal and generates a second signal that is asserted when at least one is asserted, and a counter that counts the second signal.
The second signal is asserted with a period of 30 electrical degrees. Therefore, the electrical angle of 270 degrees can be detected by counting the second signal nine times.

  Another aspect of the present invention relates to a motor drive device that drives any one of three-phase four-pole, three-phase six-pole, and three-phase eight-pole motors. The motor drive device compares the back electromotive force generated at one end of each of the U, V, and W phase coils that are star-connected to the motor with the midpoint voltage that is generated at the common connection node of the three coils. A counter electromotive force detection circuit that generates a rotation detection signal that is asserted at a first rotation number and a first rotation number that generates a first rotation speed signal that is asserted every time a predetermined number of rotation detection signals are counted when the motor has four poles When the motor has 6 poles, the second rotation speed signal generation section that generates the second rotation speed signal when the motor has 6 poles, and when the motor has 8 poles, it is asserted every time a predetermined number of rotation detection signals are counted. And a selector that selects and outputs one of the first to third rotational speed signals according to the number of poles of the motor to be driven. . The second rotation number signal generation unit matches the first counter that measures the period in which the rotation detection signal is asserted, and the count value of the first counter coincides with a value that indicates 1/2 of the period that was measured before that. A comparator that generates a first signal that is asserted every time, and a second counter that asserts a second rotation speed signal each time a predetermined number of rotation detection signals and first signals are counted.

The first signal is asserted with a period of 60 electrical degrees and a phase delayed by 30 electrical degrees with respect to the rotation detection signal. Therefore, by counting the first signal and the rotation detection signal, an electrical angle of 270 degrees can be detected, and a rotation speed signal suitable for a 6-pole motor can be generated.
According to the motor drive device of this aspect, it is possible to generate an appropriate rotation speed signal corresponding to the number of poles, regardless of whether 4 poles, 6 poles, or 8 poles are connected.

  Another aspect of the present invention further includes a lock alarm signal generation circuit that monitors the rotation detection signal and generates a lock alarm signal that is asserted when a period in which the rotation detection signal continues at a certain level exceeds a predetermined time. Also good. The selector may select and output one of the first to third rotation speed signals and the lock alarm signal.

  Yet another embodiment of the present invention is a cooling device. The cooling device includes a fan motor and the motor driving device according to any one of the above-described modes for driving the fan motor.

  Yet another embodiment of the present invention relates to a method of generating a rotation speed signal when driving a three-phase six-pole motor. This method compares the back electromotive force generated at one end of each of the U, V, and W phase coils that are star-connected to the motor with the midpoint voltage that is generated at the common connection node of the three coils. Generating a rotation detection signal to be asserted, measuring a cycle in which the rotation detection signal is asserted using the first counter, and a count value of the first counter matches a value indicating ½ of the cycle. Generating a first signal that is asserted every time, and generating a rotation speed signal that is asserted every time a predetermined number of rotation detection signals and first signals are counted using a second counter.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to the present invention, a rotation speed signal suitable for a 6-pole motor can be generated.

It is a time chart which shows the counter electromotive force and rotation detection signal which arise in the coil of U phase, V phase, and V phase, and the rotation speed signal of 4 poles, 6 poles, and 8 poles. It is a block diagram which shows the structure of an electronic device provided with the cooling device which concerns on embodiment. It is a block diagram which shows the structure of the rotation speed signal generation circuit which concerns on embodiment. 3 is a time chart showing the operation of the rotation speed signal generation circuit of FIG. 2. It is a block diagram which shows the structure of the rotation speed signal generation circuit which concerns on a modification. It is a time chart which shows operation | movement of a lock alarm signal generation circuit.

  An embodiment of the present invention will be described by taking as an example a fan motor drive device that is mounted on an electronic computer such as a personal computer or a workstation and drives a fan motor for cooling a CPU or the like.

  First, the overall configuration of the driving apparatus 100 according to the embodiment will be described with reference to FIG. The driving device 100 is mounted on a cooling device having a fan motor, and drives the fan motor. FIG. 2 is a block diagram illustrating a configuration of the electronic apparatus 1 including the cooling device 4 according to the embodiment.

  The electronic device 1 is a personal computer, a computer such as a workstation, or a home appliance such as a refrigerator or a television, and includes a cooling target, for example, a CPU 2. The cooling device 4 cools the CPU 2 by blowing air.

  The cooling device 4 includes a driving device 100 and a fan motor 6. The fan motor 6 is disposed close to the CPU 2 to be cooled. The driving device 100 drives the fan motor 6 based on a control input signal (hereinafter simply referred to as a control signal) S1 for instructing the torque (rotational speed) of the fan motor 6. The cooling device 4 is modularized and marketed and distributed.

The fan motor 6 is a three-phase AC motor and includes star-connected U-phase, V-phase, and L-phase coils L _U , L _V , and L _W and a permanent magnet (not shown). In the present embodiment, the number of poles of the fan motor 6 is six.

  The driving device 100 is a functional IC (Integrated Circuit) integrated on one semiconductor substrate. A power supply voltage is supplied to the power supply terminal ICVDD, and a ground voltage is supplied to the ground terminal ICGND.

  An input signal S1 from the outside is input to the input terminal PWM. In the present embodiment, the input signal S1 is a PWM signal that is pulse width modulated in accordance with the target torque of the motor. The input signal S1 may be an analog voltage corresponding to the ambient temperature Ta obtained using a thermistor or the like, or may be a digital signal from a host processor such as a CPU.

  The drive device 100 includes a back electromotive force (BEMF) detection circuit 10, an external PWM input circuit 12, a drive signal synthesis circuit 14, a drive circuit 16, and a rotation speed signal generation circuit 20.

  The external PWM input circuit 12 is an interface circuit that receives the input signal S1. The external PWM input circuit 12 generates a control signal S2 corresponding to the input signal S1.

The BEMF detection circuit 10 connects the back electromotive forces V _U , V _V , and V _W generated at one end of the U, V, and W phase coils L _U , L _V , and L _{W that} are star-connected in common to the three coils. Compared with the midpoint voltage V _COM generated at the node N1, a rotation detection signal S3 that is asserted every 60 electrical angles is generated. For example, the BEMF detection circuit 10 includes a comparator (not shown) provided for each of the U, V, and W phases. Each comparator compares the coil voltages (back electromotive force) V _U , V _V , V _W generated at one end of the corresponding phase coil with the midpoint voltage V _COM and generates a signal indicating the comparison result. A rotation detection signal S3 is generated by logically synthesizing signals output from the comparators of the respective phases. The configuration of the BEMF detection circuit 10 is not limited.

The drive signal synthesis circuit 14 receives the rotation detection signal S3 and the control signal S2, synthesizes them, and generates a drive control signal S4. Since a known technique may be used for the drive signal synthesis circuit 14, detailed description thereof is omitted here. The drive circuit 16 applies a drive voltage to one end of each of the coils L _U , L _V , and L _W according to the drive control signal S4. The drive circuit 16 may drive the fan motor 6 by BTL or may perform PWM drive according to the input signal S1.

  The rotation speed signal generation circuit 20 generates a rotation speed signal FG that changes every 180 degrees of the mechanical angle (motor angle) of the fan motor 6, that is, every 1/2 rotation of the fan motor 6, and outputs it from the FG terminal.

FIG. 3 is a block diagram showing a configuration of the rotation speed signal generation circuit 20 according to the embodiment.
The rotation speed signal generation circuit 20 includes a first counter 22, a comparison unit 24, and a second counter 30.

  The first counter 22 receives the rotation detection signal S3 and the clock signal CLK. The first counter 22 is a counter that counts up (or counts down) according to the clock signal CLK, and outputs a count value D1. The first counter 22 is reset every time the rotation detection signal S3 is asserted. The count value D1 immediately before being reset indicates the period τ of the rotation detection signal S3. That is, the first counter 22 measures the period τ of the rotation detection signal S3.

The comparison unit 24 generates a first signal S11 that is asserted every time the count value D1 of the first counter 22 matches a value D2 indicating 1/2 of the period τ measured before that.
The comparison unit 24 includes a register 26 and a comparator 28. The register 26 holds the count value D1 at the timing when the rotation detection signal S3 is asserted. The count value D1 held by the register 26 indicates the cycle τ of the rotation detection signal S3. The register 26 doubles the count value D1 and outputs data D2 indicating the half cycle of the rotation detection signal S3. To multiply the binary data by 1/2 is equivalent to shifting the data downward by 1 bit. Therefore, the register 26 may hold a value obtained by bit-shifting the count value D1.

The comparator 28 compares the current count value D1 of the first counter 22 with a half value of the count value corresponding to the period τ measured before that, that is, the data D2, and each time they match. A first signal S11 that is asserted at is generated. The comparator 28 can be composed of a logic gate that performs bit comparison between the count value D1 and the data D2.
The first signal S11 generated by the comparison unit 24 has the same period of 60 electrical degrees as the rotation detection signal S3 and is asserted with a phase delayed by 30 electrical degrees from the rotation detection signal S3.

  The second counter 30 receives the rotation detection signal S3 and the first signal S11. The second counter 30 generates the rotation speed signal FG by counting those signals.

  The second counter 30 includes a combining unit 32 and a counter 34. The synthesizer 32 receives the rotation detection signal S3 and the first signal S11 and generates a second signal S12 that is asserted when at least one is asserted. The second signal S12 generated in this way has a period of 30 electrical angles. The synthesizer 32 can be composed of, for example, a logical sum (OR) gate. The counter 34 asserts the rotation speed signal FG every time the second signal S12 is counted nine times. The rotation speed signal FG generated in this way has a cycle of an electrical angle of 270 degrees.

The above is the configuration of the rotation speed signal generation circuit 20. Next, the operation will be described. FIG. 4 is a time chart showing the operation of the rotation speed signal generation circuit 20 of FIG. Each time the coil voltages (back electromotive forces) V _U , V _V , and V _W cross the midpoint voltage V _COM , the rotation detection signal S3 is asserted.

The first counter 22 is reset every time the rotation detection signal S3 is asserted, and repeats the counting operation. The count value D1 immediately before the reset indicates the cycle τ of the rotation detection signal S3. A count value D1 _i indicating the period τ _i of the rotation detection signal S3 in the i-th cycle is held in the register 26, and is used to generate data D2 _{i + 1} used in the subsequent (i + 1) -th cycle. Specifically, D2 _{i + 1} = D1 _i × 1/2. When the count value D1 _{i + 1} of the first counter 22 matches the data D2 _{i + 1} in the (i + 1) th cycle, the first signal S11 is asserted. The first signal S11 is a signal that is delayed by a half cycle, that is, an electrical angle of 30 degrees with respect to the rotation detection signal S3. The synthesizer 32 synthesizes the first signal S11 and the rotation detection signal S3 to generate the second signal S12. The second signal S12 has a period of 30 electrical degrees. The counter 34 generates the rotation number signal FG by counting the second signal S12.

  As described above, the rotation speed signal generation circuit 20 of FIG. 2 can generate the rotation speed signal FG suitable for the three-phase 6-pole motor.

  FIG. 5 is a block diagram showing a configuration of a rotation speed signal generation circuit 20a according to a modification. The rotation speed signal generation circuit 20a is provided in place of the rotation speed signal generation circuit 20 of FIG. 2 in a motor driving device that drives any one of three-phase four-pole, three-phase six-pole, and three-phase eight-pole motors.

The rotation speed signal generation circuit 20a receives the rotation detection signal S3. The rotation speed signal generation circuit 20a includes a first rotation speed signal generation circuit 42, a second rotation speed signal generation circuit 44, a third rotation speed signal generation circuit 46, a lock alarm signal generation circuit 48, and a selector 50.
The first rotation speed signal generation circuit 42 becomes active when the motor to be driven has four poles, and the first rotation speed signal FG that changes in level every time the rotation detection signal S3 is counted a predetermined number, specifically three times. ₁ is generated.
The second speed signal generating circuit 44 becomes active when driven motor is six poles, for generating a second speed signal FG _2. The second rotation speed signal generation circuit 44 is the rotation speed signal generation circuit 20 of FIG.
The third rotation speed signal generation circuit 46 becomes active when the motor to be driven has 8 poles, and a third rotation speed signal that changes in level every time the rotation detection signal S3 is counted a predetermined number, specifically, 6 times. FG ₃ is generated.

The lock alarm signal generation circuit 48 monitors the rotation detection signal S3, and the period during which the rotation detection signal S3 continues at a certain level (for example, low level) exceeds a predetermined first time (referred to as a lock alarm detection period _TAL ). A lock alarm signal AL that is asserted is generated. The lock alarm signal generation circuit 48 negates the lock alarm signal AL when it continuously detects the rotation detection signal S3 for a predetermined second time (motor rotation return confirmation period T _REC ).

FIG. 6 is a time chart showing the operation of the lock alarm signal generation circuit 48. Prior to time t1, the motor is rotating. At time t1, foreign matter is caught in the motor, and the rotation of the motor stops (locked state). The rotation detection signal S3 has a cycle according to the number of rotations of the motor, and takes a certain level when the motor is stopped. Therefore, the lock alarm signal generation circuit 48 can detect the locked state of the motor by monitoring the rotation detection signal S3. When the rotation detection signal S3 is not generated, that is, when the constant level continues for the lock alarm detection period _TAL , the lock alarm signal AL is asserted (time t2).

When the factor that locks the motor is removed at time t3, the motor rotates again, and the rotation detection signal S3 is generated. When the rotation detection signal S3 is continuously detected during the motor rotation return confirmation period _TREC , the lock alarm signal generation circuit 48 negates the lock alarm signal AL and notifies that the lock alarm state has returned to the normal state.

Returning to FIG. The selector 50 receives the rotation speed signals FG _{1 to} FG ₃ and the lock alarm signal AL, selects one corresponding to the selection signals SEL 1 and SEL 2, and outputs the selected signal from the FG / AL terminal to the outside of the driving device 100.

  According to the rotation speed signal generation circuit 20a, it is possible to generate an appropriate rotation speed signal FG for each motor having various pole numbers and output it to the outside, thereby improving the versatility of the driving apparatus 100. be able to. Depending on the application, a lock alarm signal AL indicating an abnormal state of the motor may be required instead of the rotation speed signal FG. In this case, since the rotation speed signal FG and the lock alarm signal AL can be switched by the selector 50, various applications can be handled.

  In the embodiment, the case where the cooling device 4 is mounted on an electronic device and the CPU is cooled has been described. However, the application of the present invention is not limited to this and can be used for various applications for cooling a heating element. . Furthermore, the use of the driving apparatus 100 according to the present embodiment is not limited to driving a fan motor, and can be used to drive other various motors.

  Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate the principles and applications of the present invention, and the embodiments are defined in the claims. Many variations and modifications of the arrangement are permitted without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Drive device, 1 ... Electronic device, 2 ... CPU, 4 ... Cooling device, 6 ... Fan motor, 10 ... BEMF detection circuit, 12 ... External PWM input circuit, 14 ... Drive signal synthesis circuit, 16 ... Drive circuit, 20 DESCRIPTION OF SYMBOLS ... Revolution signal generation circuit, 22 ... First counter, 24 ... Comparison unit, 26 ... Register, 28 ... Comparator, 30 ... Second counter, 32 ... Synthesis unit, 34 ... Counter, 40 ... Rotation signal generation circuit, 42 ... 1st rotation speed signal generation circuit, 44 ... 2nd rotation speed signal generation circuit, 46 ... 3rd rotation speed signal generation circuit, 48 ... Lock alarm signal generation circuit, 50 ... Selector, FG ... Rotation speed signal, S1 ... Input Signal, S2 ... Control signal, S3 ... Rotation detection signal, S11 ... First signal, S12 ... Second signal, AL ... Lock alarm signal.

Claims (11)

A driving device for a three-phase six-pole motor,
The counter electromotive force generated at one end of each of the U, V, and W phase coils connected to the star of the motor is compared with the midpoint voltage generated at the common connection node of the three coils, and is asserted every 60 degrees of electrical angle. A counter electromotive force detection circuit for generating a rotation detection signal;
A first counter that is reset each time the rotation detection signal is asserted and measures a period of the rotation detection signal;
A comparator that generates a first signal that is asserted each time the count value of the first counter matches a value that represents a half of the period measured before;
A second counter that generates a rotation number signal that is asserted each time a predetermined number of the rotation detection signal and the first signal are counted;
A motor drive device comprising: The comparison unit includes:
A register for holding the latest period measured by the first counter;
A comparator that compares a value indicating a half of the period stored in the register with a count value of the first counter;
The motor drive device according to claim 1, comprising: The second counter is
A synthesis unit that receives the rotation detection signal and the first signal, and generates a second signal that is asserted when at least one is asserted;
A counter for counting the second signal;
The motor drive device according to claim 1, wherein the motor drive device includes: A motor driving device for driving any one of three-phase four-pole, three-phase six-pole, and three-phase eight-pole motors,
The counter electromotive force generated at one end of each of the U, V, and W phase coils connected to the star of the motor is compared with the midpoint voltage generated at the common connection node of the three coils, and is asserted every 60 degrees of electrical angle. A counter electromotive force detection circuit for generating a rotation detection signal;
When the motor has four poles, a first rotation number signal generation unit that generates a first rotation number signal that is asserted every time the rotation detection signal is counted a predetermined number;
When the motor has 6 poles, a second rotational speed signal generating unit that generates a second rotational speed signal;
When the motor has eight poles, a third rotation number signal generation unit that generates a third rotation number signal that is asserted every time the rotation detection signal is counted a predetermined number;
A selector that selects and outputs one of the first to third rotational speed signals according to the number of poles of the motor to be driven;
With
The second rotation speed signal generating unit is
A first counter that measures a period at which the rotation detection signal is asserted;
A comparator that generates a first signal that is asserted each time the count value of the first counter matches a value that represents a half of the period measured before;
A second counter that asserts the second rotation number signal each time a predetermined number of the rotation detection signal and the first signal are counted;
A motor drive device comprising: A lock alarm signal generation circuit that monitors the rotation detection signal and generates a lock alarm signal that is asserted when a period in which the rotation detection signal continues at a certain level exceeds a predetermined time;
5. The motor drive device according to claim 4, wherein the selector selects and outputs one of the first to third rotation speed signals and the lock alarm signal. 6. The comparison unit includes:
A register for holding the latest period measured by the first counter;
A comparator that compares the count value of the first counter with a value indicating a half of the period stored in the register;
The motor drive device according to claim 5, comprising: The second counter is
A synthesis unit that receives the rotation detection signal and the first signal, and generates a second signal that is asserted when at least one is asserted;
A counter for counting the second signal;
The motor drive device according to claim 4, comprising: A fan motor,
The motor drive device according to any one of claims 1 to 7, which drives the fan motor;
A cooling device comprising: A method of generating a rotation speed signal when driving a three-phase six-pole motor,
The counter electromotive force generated at one end of each of the U, V, and W phase coils connected to the star of the motor is compared with the midpoint voltage generated at the common connection node of the three coils, and is asserted every 60 degrees of electrical angle. Generating a rotation detection signal;
Measuring a period at which the rotation detection signal is asserted using a first counter;
Generating a first signal that is asserted each time a count value of the first counter matches a value indicating half of the period;
Generating a rotation speed signal that is asserted each time a predetermined number of the rotation detection signal and the first signal are counted using a second counter;
A method comprising the steps of:   The method according to claim 9, wherein the value to be compared with the count value of the first counter is updated every time the first counter is reset. Generating a second signal that is asserted when at least one of the rotation detection signal and the first signal is asserted;
The method according to claim 9 or 10, wherein the second counter counts the second signal.

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