JP2004173466A - Motor protection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To protect a motor against burning when a rotor of the motor under driving is locked due to some cause by detecting the locking of the rotor surely by a simple and inexpensive arrangement while eliminating erroneous detection. <P>SOLUTION: The motor protection circuit comprises a means for detecting a counter-electromotive force induced in coils (windings 1u-1w) of a motor 1 by the switching of a field, and a means for outputting a stop signal S<SB>2</SB>of the motor 2 when the counter-electromotive force disappears by the locking of the rotor of the motor 2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor protection circuit when a rotor is restrained during energization driving.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a motor incorporated in various electronic devices, if the rotor is restrained (locked) during energization driving for some reason, a serious accident such as burnout of the motor is caused due to the continued restrained state.
[0003]
Therefore, for example, in a brushless DC motor used for a fan motor for cooling, a paper feed motor, or the like, a pulse output of a magnetic sensor such as a Hall element for detecting the rotation position is used, and a change in the frequency is used to determine the energizing drive. The motor is stopped by detecting the rotor constraint of the middle motor (see Patent Document 1).
[0004]
Also, in this type of brushless DC motor, a small resistor is inserted into the power line of the motor, and by detecting an abnormally large current from the voltage drop of the small resistor, the rotor constraint of the motor during energization driving is restricted. Stopping the motor upon detection is also performed.
[0005]
[Patent Document 1]
Japanese Patent Publication No. 7-99953 (page 2-3, FIGS. 1 and 6)
[0006]
[Problems to be solved by the invention]
In the case of detecting the rotor constraint from the frequency change of the pulse output of the magnetic sensor as in the conventional case, a complicated combination circuit for charging / discharging the time constant circuit by the pulse output, comparing the voltage of the converter, and switching the transistor is required. However, there is a problem that the number of parts increases and the cost becomes extremely high.
[0007]
The cycle (interval) of the pulse output is measured with a reference clock to detect a rotor constraint, or the frequency (F) / voltage (V) of the pulse output is converted into a voltage, and the voltage change is calculated from the voltage change. Although it is conceivable to detect a rotor constraint, these cases also require a reference frequency oscillator, an F / V converter, and the like, and the same problem occurs.
[0008]
Next, when detecting the rotor restraint from the voltage drop of the small resistance of the power supply line, when it takes a long time to start up the motor due to low-speed startup or so-called slow start, a large current flows during that time, There is a problem that erroneous detection is caused by the flow of the large current.
[0009]
A similar problem occurs not only in a brushless DC motor but also in a three-phase AC motor or the like.
[0010]
The present invention provides a simple and inexpensive configuration that reliably detects a rotor constraint and protects the motor from burnout when the rotor of the motor being driven is restrained for some reason. Make it an issue.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a motor protection circuit according to a first aspect of the present invention includes a means for detecting a back electromotive force generated in a coil of a motor by switching a magnetic field, and losing the back electromotive force by restricting a rotor of the motor. Means for outputting a motor stop signal when the motor is stopped.
[0012]
Therefore, if the rotor is restrained during the energization driving of the motor, the back electromotive force of the motor coil disappears, and a detection signal of the disappearance outputs a motor stop signal, which stops the motor. Motor burnout and the like are prevented.
[0013]
In this case, detection of the back electromotive force generated in the coil of the motor can be performed by simple and inexpensive voltage detection, and erroneous detection is performed even when a large current flows through the coil at low speed start or slow start. Without this, the constraint of the rotor is reliably detected, and the protection of the motor is surely realized.
[0014]
According to a second aspect of the present invention, the motor includes a brushless DC motor, and a coil is a winding of a stator of the brushless DC motor.
[0015]
Therefore, in the case of a brushless DC motor, the protection of the first aspect is performed by detecting the back electromotive force generated in the winding of the stator.
[0016]
Further, the motor protection circuit according to claim 3 is means for adding and synthesizing the back electromotive force generated in the winding of each phase of the stator of the brushless DC motor by switching the rotating field element, and performing smooth output.
Means for switching a semiconductor switch based on the disappearance of the smoothed output to output a detection signal of a rotor constraint of the motor;
A time constant circuit that is charged by a detection signal of a rotor constraint, and that outputs a motor stop signal when the detection signal continues for a predetermined time.
[0017]
Therefore, when the rotor is restrained during the energization driving of the brushless DC motor, back electromotive force is not generated in the windings of each phase of the stator, and the output obtained by adding and synthesizing these starting powers disappears. The semiconductor switch switches and outputs a detection signal of the rotor constraint.
[0018]
A motor stop signal is output only when the detection signal continues for a predetermined time and the rotor is securely restrained, and the motor is stopped by this signal, thereby providing the same protection as in claim 1. Can be performed.
[0019]
Therefore, a more specific protection circuit for the brushless DC motor can be provided.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a circuit configuration when applied to a brushless DC motor.
In the brushless DC motor 1, the three-phase windings (armature windings) 1u, 1v, and 1w of the stator, which are coils, are motor driver ICs (IC: integrated type) of model number LB1980JH (manufactured by Sanyo Electric Co., Ltd.). 2) are connected to output terminals u, v, w of each phase.
[0021]
Further, the Hall elements 3u, 3v, 3w of each phase of the Hall IC 3 which is a rotation position sensor (magnetic sensor) of the motor 1 are connected to a pair of detection terminals u (+), u (-), v (+), v (-), w (+), w (-).
[0022]
Then, when the motor 1 is started and its rotor rotates, the motor driver IC 2 outputs the signals from the output terminals u to w at the timing of the field switching based on the speed command and the like based on the detection outputs of the rotational positions of the Hall elements 3u to 3w. A current of each phase is supplied to each of the windings 1u to 1w, a rotating field is generated, the rotor continues to rotate, and the motor 1 enters an operation state at a commanded speed.
[0023]
At this time, back electromotive force is sequentially generated in the windings 1u to 1w due to a current change accompanying the field switching, and these back electromotive forces are paralleled by resistors Ru, Rv, Rw and backflow prevention diodes Du, Dv, Dw. Are added and synthesized.
[0024]
Further, the combined back electromotive force is smoothed by a smoothing circuit 4 including resistors R ₁ , R ₂ and a capacitor C ₁ , and the voltage of the smoothed output is passed through a resistor R ₃ to a transistor Q _{1 of} an NPNP as a semiconductor switch. Applied to the base.
[0025]
This application, while the rotor of the motor 1 is rotated, the transistor Q ₁ is turned on, its collector output is held at the low level (hereinafter referred to as L), the detection signals S ₁ of the rotor constraint of the motor 1 is not output .
[0026]
Then, the rotor of the motor 1 is restricted for some reason, the switching of the field is not performed, the electromotive force is not generated in the winding 1U～1w, and switched off the transistor Q ₁ is from on, the The collector output becomes high level (hereinafter referred to as H), and the detection signal S1 of the rotor constraint of the motor ₁ is output.
[0027]
In this case, the resistance R ₄ of the time constant circuit 5 the collector of the transistor Q ₁ is _connected to the connection point of the capacitor C _2, the detection signal S _1, by the connection point is changed to H from L, a capacitor C ₂ There is connected via a resistor R ₄ to the power supply terminal + B, it is charged with a voltage of eg 5V of the power supply terminal + B.
[0028]
Then, in order to prevent erroneous detection due to momentary fluctuations, when the restraint of the rotor motor 1 is a predetermined time (constraint protection circuit operation time) continues to charge voltage of the capacitor C ₂ reaches a certain voltage, the voltage thereof stop signal S ₂ of the motor 1 is output from the time constant circuit 5.
[0029]
In this case the stop signal _{S 2} output from the time constant circuit 5, FETs Q _2, it is inputted via a buffer transistor _{Q 3} to the stop command terminal (reset terminal) pc of the driver IC 2.
[0030]
Then, the input of the stop signal S _2, the driver IC2 stops the driving of the motor 1 to stop the current output from the output terminal U to W, the rotation of the motor 1 to prevent burnout and the like of the winding 1u~1w Protection against child restraint.
[0031]
When the power is turned off or the speed command becomes zero, an H reset signal is input to a reset signal terminal 6 from a reset signal generator (not shown). transistor Q ₄ is turned on by the on resistance R ₅ and capacitor C ₃ is discharged, which is connected to the power supply terminal + B through a transistor Q ₅ which has been turned on by the charging voltage of the capacitor C ₃ is turned off.
[0032]
Then, the capacitor by turning off the transistor Q _5, the capacitor C ₄ is charged by the + 5V power supply terminal + B via a resistor R _6, this charge, the transistor Q ₅ of the reset control of the final stage is turned on by the ON C ₂ is discharged.
The discharge stop signal S ₂ is turned off, the reset is performed.
[0033]
In the drawing, R ₇ and R ₈ are bias resistors of the Hall IC 3, and R ₉ and R ₁₀ are bias resistors of the transistors Q ₂ and Q ₃ .
[0034]
Cu, Cv, and Cw are capacitors between the windings 1u to 1w and the terminal RF of the driver IC 2, and a plurality of resistors Rx having the same or different resistance values are provided between the terminal RF and the ground. I have.
[0035]
Next, the resistors Ru to Rw, the diodes Du to Dw, and the smoothing circuit 4 form means for detecting the back electromotive force generated in the coil of the motor 1. The transistor Q ₁ and the time constant circuit 5 control the rotation of the motor 1. forming means for outputting a stop signal S ₂ motor 1 when the counter electromotive force is lost by the child restraint.
[0036]
And it is a very simple and inexpensive configuration that detects the rotor constraint of the motor 1 from the disappearance of the smoothed voltage of the back electromotive force of the motor 2.
[0037]
Further, at the time of starting or slow start at low speeds, the winding 1u, 1 v, even when a large current flows through the 1 w, without turning on the transistor Q ₁ is incorrectly Furthermore, rotating magnetic field is continuously unless certain time lost, since the stop signal S ₂ is not output, no false or erroneous operation of the rotor constraint does not occur, reliable.
[0038]
In the embodiment, the brushless DC motor 1 is applied. However, various motors such as a three-phase AC motor can be similarly applied as long as a counter electromotive force is generated during driving. .
[0039]
That is, in the case of a three-phase AC motor, the present invention can be applied to any motor as long as the two-phase winding is energized and the one-phase winding is de-energized.
[0040]
In addition, since there is no need to detect the rotational position using a Hall element or the like, the present invention has an advantage that it can be applied to a motor having no rotational position detecting function.
[0041]
【The invention's effect】
The present invention has the following effects.
First, in the case of claim 1, when the rotor of the motor (brushless DC motor 1) is restrained during energization driving, the back electromotive force of the coils (windings 1u to 1w) of the motor 1 disappears, and outputs a motor stop signal S ₂ by the detection of the loss, by stopping the motor by the signal S _2, it is possible to prevent the burnout of the motor.
[0042]
In this case, the back electromotive force generated in the coil of the motor can be eliminated by a simple and inexpensive voltage detection, and no erroneous detection occurs even at a low speed start or a slow start. Thus, the occurrence of rotor constraint can be reliably detected, and the protection of the motor can be reliably achieved.
[0043]
Next, in the case of claim 2, since the motor is composed of the brushless DC motor 1 and the coils are the windings 1u to 1w of the stator of the brushless DC motor 1, in the case of the brushless DC motor 1, the winding of the stator is By detecting the back electromotive force generated in the lines 1u to 1w, the same protection as in claim 1 can be performed.
[0044]
Next, in the case of claim 3, when the rotor is restrained in the brushless DC motor 1, the back electromotive force of the windings 1u to 1w of each phase of the stator is added and synthesized, and the smoothed output disappears. Due to this disappearance, the semiconductor switch (transistor Q ₁ ) can be switched to output the rotor restraint detection signal S ₁ .
[0045]
Then, the detection signal S ₁ is continued for a predetermined time, only when the restraint of the rotor occurs reliably, it outputs the stop signal S ₂ motor 1, the motor is stopped 1 This signal S ₂ Thus, the same protection as in claim 1 can be provided.
[0046]
Therefore, a more specific protection circuit for the brushless DC motor 1 can be provided.
[Brief description of the drawings]
FIG. 1 is a connection diagram of one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Brushless DC motor 1u, 1v, 1w Winding 4 Smoothing circuit 5 Time constant circuit Q ₁ Transistor S as a semiconductor switch ₁ Rotor restraint detection signal S ₂ Stop signal

Claims (3)

Means for detecting a back electromotive force generated in the coil of the motor by switching the field;
Means for outputting a motor stop signal when the back electromotive force has disappeared due to the rotor constraint of the motor. The motor protection circuit according to claim 1, wherein the motor is a brushless DC motor, and the coil is a winding of a stator of the brushless DC motor. Means for adding and synthesizing the back electromotive force generated in the windings of each phase of the stator of the brushless DC motor by switching the rotating field, and smoothing the output;
Means for switching a semiconductor switch by the disappearance of the smoothed output to output a detection signal of a rotor constraint of the motor;
A motor protection circuit comprising: a time constant circuit charged by the detection signal; and means for outputting a motor stop signal when the detection signal continues for a predetermined time.

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