JP3397984B2 - Rotation state detection circuit of brushless motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor rotation state detection circuit suitable for use in a DC fan motor or the like.

[0002]

2. Description of the Related Art Generally, a large-scale OA device or the like is provided with a fan motor for cooling the internal temperature of the device. This fan motor can prevent the OA equipment from being destroyed due to the rise of the internal temperature of the OA equipment due to the heat generated by the elements inside the OA equipment, and thus the internal temperature of the OA equipment can be sufficiently cooled. OA set to the number of revolutions
It is designed to rotate when the device is used. However, the structure of the fan motor has deteriorated over time,
In some cases, the preset rotation speed cannot be maintained, and the rotation speed may be lower than this rotation speed. In this case, there is a high possibility that the OA equipment is destroyed by the internal heat. However, in the case of the OA equipment operated by the operator, the operator notices an abnormality of the fan motor (for example, motor noise, temperature of the OA equipment, etc.), Countermeasures (fan motor replacement) by early detection are also possible. However, in the case of an unattended server device installed in a relay station on the Internet used for communication of a personal computer, if an abnormality occurs in the fan motor inside the server device and the number of rotations drops, etc. It is necessary to inform the operator of the place that centrally manages Otherwise, the server equipment will be thermally destroyed. Therefore, conventionally, by monitoring the FG pulse generated in response to the rotation speed of the fan motor, a decrease in the rotation speed of the fan motor is detected, and the detected output is notified to a remote operator, so that the fan motor has a lifespan. Etc. gave instructions such as when it is time to replace. This detection function is called a life sensor function.

The above-mentioned method for monitoring the FG pulse of the fan motor is to detect that the frequency of the FG pulse has become lower than a preset frequency and rotate the fan motor only at a rotational speed lower than the preset rotational speed. It is decided that it cannot be done. However, in this method, since the fan motor gradually increases its rotation speed during the period from when the fan motor is started to when it reaches the normal rotation speed, the rotation speed is lower than the set rotation speed of the fan motor described above. However, there is a problem that the fan motor is in an abnormal state even though the fan motor is normal.

Therefore, as a means for preventing erroneous detection at the time of starting the fan motor, a delay circuit including a capacitor is provided, and the FG pulse monitoring function works for a certain period of time from the start of the fan motor to the steady rotation speed. However, the FG pulse is monitored after a certain period of time to detect the fan motor abnormality.

[0005]

However, in order to realize the function of driving the fan motor and the life sensor function except when starting, it is necessary to combine the fan motor driving IC and the delay-dedicated IC to which a capacitor is externally attached. There is.
A constant current flows from the delay IC to the external capacitor, and depending on the terminal voltage of the external capacitor when the external capacitor is charged for the time from the start of the fan motor to the steady rotation state, The operation and stop of the life sensor function were controlled.

Therefore, since the life sensor function is controlled by the time factor of delay, a relatively large-capacity capacitor must be externally attached, and the board area is reduced together with the driving IC and the delay-dedicated IC. There was a problem that the cost increased as the size increased. Further, it is impossible to set a reliable delay time due to variations in the capacitance of the capacitor, variations in the delay time based on temperature characteristics, etc., and it operates when the life sensor function does not have to operate,
On the contrary, there is a problem that it does not work when it needs to work. Furthermore, the capacity of the capacitor must be selected each time according to the type of fan motor, which causes a problem of complicated operation.

Therefore, an object of the present invention is to provide a rotation state detection circuit for a brushless motor, which system can be simplified and can be applied to a wide range of fan motors.

[0008]

The present invention has been made to solve the above problems, and is characterized in that a pulse whose frequency changes in response to the rotation speed of a brushless motor is used. A discharge circuit that discharges the charging voltage of a charging circuit that is applied with a power supply voltage and charges the power supply voltage with a specific time constant; and a comparison circuit that compares the charging voltage of the charging circuit with a reference voltage. , A latch circuit that latches the comparison output of the comparison circuit in synchronization with the pulse, and a specific number of the pulses that should be generated in a normal state between the start of the brushless motor and the steady rotation speed. While counting and counting a specific number of the pulses, a counter that generates an inhibition signal for inhibiting the output of the latch circuit from changing according to the output of the comparison circuit and setting a fixed value. When the charging voltage of the charging circuit exceeds the reference voltage after the counter has counted the specific number of pulses, one of the logic values latched by the latch circuit causes the brushless motor to This is to inform that the rotation speed is lower than the steady rotation speed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be specifically described with reference to the drawings. FIG. 1 is a circuit diagram showing a rotation state detection circuit of a brushless motor according to the present invention. As an example, a case where the brushless motor is applied to a two-phase unipolar DC fan motor is described.

In FIG. 1, (1) is an IC for driving a fan motor, a power supply terminal (2) to which a power supply voltage VCC is applied, and a hall element (3) fixed to a stator (not shown) of the fan motor. ) Which is an output of the FG pulse is applied to the Hall input terminals H + and H-, and the output terminals O to which one ends of the two-phase coils (4) and (5) of the fan motor are connected
It has UT1 and OUT2, a charging voltage input terminal CR to which a charging voltage is applied, an alarm terminal LS for notifying an abnormal rotation state of the fan motor, and a ground terminal GND.

Outside the driving IC (1), the Hall element (3) has one power supply input connected to the power supply voltage VCC through the resistor (6) and the other power supply input grounded. The Hall element (3) output FG pulses applied to the Hall input terminals H + and H- are antiphase waveforms having a phase difference of 180 degrees. A resistor (7) and a capacitor (8) forming a charging circuit are connected in series between the power supply voltage VCC and the ground, and a time constant determined by the resistance value of the resistor (7) and the capacitance of the capacitor (8). Charging is performed in accordance with the charging voltage, and the charging voltage appearing across the capacitor (8) at this time is applied to the charging voltage input terminal CR. Further, the alarm terminal LS is connected to the power supply voltage VCC via the pull-up resistor (9).

Next, the drive system of the fan motor in the drive IC (1) will be described. (10) is a Hall amplifier, the input waveform of the Hall input terminal H + is applied to one input, and the Hall input terminal H is applied to the other input.
A negative input waveform is applied. That is, hall amplifier (1
From 0), a rectangular wave HA with a duty of 50%, which repeats high level and low level for every 180 electrical degrees, is output. The Hall amplifier (10) has a hysteresis structure to prevent the influence of external noise. Reference numeral (11) is a control block, the input of which is connected to the output of the Hall amplifier (10). Further, the two outputs of the control block (11) are connected to the NPN type output transistors (12) and (13). Specifically, the base of the output transistor (12) is connected to one output of the control block (11), the collector is connected to the output terminal OUT1, and the emitter is grounded. Similarly, the base of the output transistor (13) is connected to the other output of the control block (11), the collector is connected to the output terminal OUT2, and the emitter is grounded. The above is the drive system of the fan motor. When a high level output is applied from the Hall amplifier (10), the control block (11) outputs a high level from one output (at this time, the other output is a low level) and turns on the output transistor (12). A drive current is caused to flow through one coil (4). Further, when the low level output is applied from the Hall amplifier (10), the control block (11) outputs a high level from the other output (at this time, one output is a low level), and the output transistor (13) is turned on. The other coil (5) is turned on and a drive current is caused to flow. That is, in the two-phase coils (4) and (5),
In each case, a drive current flows alternately every 180 electrical degrees, and the fan motor rotates.

Next, the control system of the fan motor inside the driving IC (1) will be described. (14) is a buffer, to which the output of the Hall amplifier (10) is applied,
Waveform (pulse) in phase with the output of the Hall amplifier (10)
Is output. (15) is a PNP type transistor, (1
6) is an NPN type transistor which constitutes a discharge circuit. That is, the base of the transistor (15) is connected to the output of the buffer (14), the emitter is connected to the charging voltage input terminal CR, and the collector is connected to the base of the transistor (16). And a transistor (16)
Is connected to the charging voltage input terminal CR, and the emitter is grounded. Therefore, the charging voltage, which is the terminal voltage of the capacitor (8) applied to the charging voltage input terminal CR, turns on the transistor (15) when the output of the buffer (14) falls to a low level and turns on the transistor (16). ) Is discharged through the collector-emitter path. However, even if the charging voltage is completely discharged, the voltage at the charging voltage input terminal CR will not drop below the base-emitter voltage of the transistor (16), 0.7 volt. That is, the minimum voltage of the charging voltage input terminal CR is clipped to 0.7 volt.

Between the power supply voltage VCC and ground, a resistor (1
7) (18) and the diode (19) are connected in series. Reference numeral (20) is a comparator, one input of which is + terminal connected to the charging voltage input terminal CR, and the other input of which is − terminal is connected to a connection point of the resistors (17) and (18). The reference voltage VREF1 appearing at the connection point of the resistors (17) and (18) will now be described. When the fan motor is rotating at a constant speed in a normal state, the charging voltage is a buffer that responds to the rotation speed of the fan motor. Since it is discharged at the trailing edge of the output of (14), it cannot rise to a specific voltage. That is, when an abnormality occurs in the fan motor and the rotation speed falls below a predetermined rotation speed, the output frequency of the buffer (14) may decrease and the charging voltage may rise to the specific voltage.
Therefore, as a reference for detecting the abnormality of the fan motor, the specific voltage is set to VREF1 and the-
Applied to the terminal. The diode (19) is used to generate the reference voltage VREF1. First, considering that the minimum voltage applied to the + terminal of the comparator (20) is 0.7 volt, This is for compensating the reference voltage VREF1 of 0.7 volt or more, and secondly, for preventing the set rotational speed of the fan motor that should bring the alarm terminal LS to the low level when the power supply voltage VCC fluctuates. Thirdly, it is for canceling the voltage change due to the temperature characteristic of the base-emitter voltage of the transistor (16) of 0.7 volt. Further, when the output of the comparator (20) switches to a high level or a low level, chattering due to uneven rotation of the fan motor is prevented from occurring, so that the comparator (20) has a hysteresis. Reference numeral (21) is a latch circuit for latching the output of the comparator (20) in synchronization with the fall of the output of the buffer (14).

(22) is a counter, which is a buffer (1
4) Counting the falling edge of the output. here,
When the fan motor functions normally, the number of FG pulses generated from startup to reaching the steady rotation speed is uniquely determined. Therefore, the counter (22) is allowed to count a number equal to or more than the FG pulse number. For example, assuming that the number of FG pulses from the start of the fan motor to the steady rotation speed is 100, the counter (22) is composed of 7 bits and 1
Design it so that it can count 28 (= 2 to the 7th power).
The counter (22) generates a low level overflow signal CTR after counting 128.

Reference numeral (23) is an NPN type transistor whose base is connected to the output of the counter (22), whose collector is connected to the output of the latch circuit (21) and whose emitter is grounded. That is, while the counter (22) is counting 128, it is the process from the start of the fan motor to the steady rotation speed, and the output CTR of the counter (22)
Is high level, the transistor (23) is turned on,
The output of the latch circuit (21) is fixed to the low level regardless of the output of the comparator (20). As a result, the output of the latch circuit (21) is fixed at the low level even if the output of the comparator (20) becomes high level before the rotational speed of the fan motor reaches the steady rotational speed. A false alarm does not occur from the alarm terminal LS. After the counter (22) has counted 128, it is assumed that the fan motor is rotating at a constant rotation speed,
Since the low level overflow signal CTR is generated,
The transistor (23) is turned off, and the output of the latch circuit (21) changes depending on the output of the comparator (20). Reference numeral (24) is an NPN type transistor whose base is connected to the output of the latch circuit (21), whose collector is connected to the alarm terminal LS, and whose emitter is grounded. The alarm terminal LS is normally a latch circuit (21).
Latches a low level (logical value "0"), the transistor (24) is turned off, and the pull-up resistor (9) outputs a high level pulled up to the power supply voltage VCC. This high level output is a signal indicating that the fan motor is normally rotating normally.

(25) is a comparator for driving I
This is for viewing the state of the charging voltage input terminal CR when the power supply voltage VCC is applied to C (1). The + terminal which is one input of the comparator (25) is connected to the charging voltage input terminal CR, and the reference voltage VREF2 (<VREF1) is applied to the − terminal which is the other input. Power supply voltage V
Resistors (26) and (27) are connected in series between CC and the ground, and the connection point voltage is applied as the reference voltage VREF2 to the negative terminal of the comparator (25). Reference voltage VR
The EF1 is a voltage higher than 0.7 volt as described above, while the reference voltage VREF2 is a voltage lower than 0.7 volt. Reference numeral (28) is a reset circuit, which is a latch circuit (21) and a counter (22) when the charging voltage, which is the terminal voltage of the capacitor (8), exceeds the reference voltage VREF2 at the initial stage of turning on the power supply voltage VCC. Is to be initialized. As a result, the latch circuit (21)
Latches the logical value "0", and each bit of the counter (22) becomes "0".

Here, the minimum level of the charging voltage appearing at the charging voltage input terminal CR is set to 0.7 V because the result of accidentally discharging the voltage at the charging voltage input terminal CR falls below the reference voltage VREF2. If this happens, the latch circuit (2
This is to prevent 1) and the counter (22) from being initialized and the correct alarm terminal LS output not being obtained. Further, the charging of the capacitor (8) is always started from the same voltage, so that the relationship between the charging time corresponding to the frequency of the FG pulse and the charging voltage is unique.

The operation of FIG. 1 will be described below with reference to the waveform chart of FIG. First, when the power supply voltage VCC is turned on, time t
At 0, the latch circuit (21) and the counter (22) are initialized, the drive system of the drive IC (1) described above operates, and the fan motor starts to rotate. In the period from the start of the fan motor to the steady rotation speed, the output frequency of the hall amplifier (10) gradually increases, but the rotation speed becomes slower than the steady value due to the life of the fan motor. The same situation occurs as. It is obviously a malfunction to set the alarm terminal LS to the low level during this period, although the fan motor is normal. In order to prevent this, the counter (22) counts the fall of the output of the buffer (14) in phase with the output of the Hall amplifier (10) 128 times. In the embodiment of the present invention, the FG that occurs from the start of the fan motor to the steady rotation speed.
The number of pulses is 100. While the counter (22) is counting the output of the buffer (14) 128 times, the output of the counter (22) is at the high level.
The output of 1) is fixed to low level. Therefore, at times t1, t2, and t3, the charging voltage is the reference voltage VR.
Even if EF1 is exceeded, the transistor (24) is turned off in response to the low level output of the latch circuit (21) and the alarm terminal L
S continues to output a high level indicating a normal state.

Thereafter, at time t4, the counter (2
2) finishes counting 128 times and outputs the low level overflow signal CTR, the transistor (23)
Is turned off, and the content of the latch circuit (21) depends on the output of the comparator (20). If something goes wrong from the state where the fan motor is rotating normally, and the rotation speed decreases, and that state continues,
For example, when the charge voltage exceeds the reference voltage VREF1 and the output of the buffer (14) falls at time t5 immediately thereafter, a high level (logical value “1”) is latched in the latch circuit (21), and the transistor (24) ) Turns on, and the alarm terminal LS becomes low level. This low level is transmitted to an external computer or the like, and the operator can be notified that the fan motor built in the OA device or the like is due to failure, deterioration, or the like, and it is time to replace it.

As described above, it is possible to reliably prevent the malfunction of the life sensor function from the start of the fan motor to the steady rotation.

[0022]

According to the present invention, from the start of the brushless motor to the steady rotation speed, the pulse whose frequency changes in response to the rotation of the brushless motor is determined in advance instead of the conventional factor of time. The determination is made by counting the specified number with a counter. Therefore, a large-capacity capacitor is not needed, the substrate area can be reduced, and the cost can be reduced. Further, since the conventional delay-dedicated IC is not necessary, the system configuration can be simplified. Furthermore, even if the type of motor changes, the number of pulses required from startup to steady rotation speed is constant, so
The advantage of being able to provide a versatile circuit is obtained.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a rotation state detection circuit of a brushless motor of the present invention.

FIG. 2 is a waveform diagram showing the operation of FIG.

[Explanation of symbols]

(1) Driving IC (7) Resistance (8) Capacitor (14) Buffer (15) (16) (23) (24) Transistor (20) Comparator (21) Latch circuit (22) Counter

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 6/12 G01H 17/00

Claims (5)

(57) [Claims] 1. A power supply voltage is applied by applying a pulse whose frequency changes in response to the rotation speed of a brushless motor, and the charge voltage of a charging circuit that charges the power supply voltage with a specific time constant is discharged. A discharge circuit, a first comparison circuit that compares the charging voltage of the charging circuit with a first reference voltage, a latch circuit that latches the comparison output of the first comparison circuit in synchronization with the pulse, and the brushless motor During the period from the start to the steady rotation speed, the specific number of the pulses to be generated in the normal state is counted, and while the specific number of the pulses is counted, the output of the latch circuit is A counter that generates a prohibition signal for prohibiting a change in accordance with the output of the comparator circuit 1 to set a fixed value, and after the counter counts a specific number of the pulses, When the electric voltage exceeds the reference voltage, the one logical value latched by the latch circuit informs that the rotation speed of the brushless motor is lower than the steady rotation speed. Rotation state detection circuit. 2. A transistor that is switched according to an output of the latch circuit is provided, and the transistor is provided when the charging voltage of the charging circuit exceeds the reference voltage after the counter has counted a specific value of the pulse. By turning on the transistor by the latch output of the latch circuit and inverting the value that is pulled up or pulled down,
2. It is informed that the rotation speed of the brushless motor is lower than the steady rotation speed.
A rotation state detection circuit for the brushless motor described. 3. The rotation state detection circuit of the brushless motor according to claim 1, wherein the first comparison circuit has a hysteresis. 4. A second comparison circuit for comparing the output of the charging circuit with a second reference voltage lower than the first reference voltage, and the output of the charging circuit becomes the second reference voltage after the power supply voltage is turned on. And a reset circuit for initializing the latch circuit and the counter when the output of the second comparison circuit changes, and the charging circuit is shared by the first and second comparison circuits. Item 1. A rotation state detection circuit for a brushless motor according to item 1. 5. The discharging circuit is configured such that a minimum voltage level when the charging voltage of the charging circuit is discharged is between the first and second reference voltages. 4. A rotation state detection circuit for the brushless motor according to 4.