JPH0799953B2 - Motor coil burnout prevention device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coil burnout prevention device used in a motor, for example, an automatic restoration type brushless motor.

[Prior Art] Japanese Patent Application Laid-Open No. 63-121491 discloses such a coil burnout prevention device for an automatic restoration type brushless motor. FIG. 6 shows the circuit shown in this publication, in which (201) is a first constant current source connected to a power supply terminal Vcc and flowing a constant current I ₁ , and (202) is grounded and a constant current I _{A second} constant current source for pulling in 2, (203) (204) are transistors constituting a differential amplifier, and the transistor (203) is between the first and second constant current sources (201) (202). And the transistor (204) is connected to the first constant current source (201). (205) is a capacitor connected between the collector of the transistor (203) and ground, (206) is a transistor connected in parallel with this capacitor, (207) is a resistor connected to the base of this transistor, (208) )
Is a resistor connected between this resistor and the power supply terminal Vcc, (2
09) is an AND circuit in which the output from the detection means for detecting the rotational position of the rotor of the brushless motor is input to one input terminal and the output is connected to the resistor (207), and (210) is the AND circuit. A capacitor connected between the other input terminal and ground, (211) is a resistor connected to the other input terminal of the AND circuit (209), and (212) is between this resistor and the output of the detection means. In the inverter connected to, the capacitor (210) and the resistor (211) constitute delay means for inverting and delaying the output of the detecting means. (twenty one
5) is a comparator whose inverting input terminal is connected to the capacitor (205) and whose non-inverting input is connected to the reference voltage via a resistor (213), and (214) is the non-inverting input terminal and output terminal of this comparator. The resistors (216) and (217) connected between the inverter and the inverter (21) are connected in series to the output terminal of the comparator (215).
The output terminal of 6) is connected to the transistor (20
The output terminal of the inverter (217) is connected to the base of the transistor (204) through the resistor (219) while being connected to the base of (3). (221) is a transistor connected between the circuit for driving the brushless motor and the ground, and its base is connected to the inverter (217) through the resistor (220).

Next, the operation of the brushless motor burnout prevention device configured as described above will be described. First, the case where the brushless motor is normally rotating will be described. When the brushless motor is normally rotating, the output (the signal having the H level and the L level) from the detecting means that detects the rotational position of the rotor of the brushless motor becomes a signal with a very short cycle. As a result, the output from the AND circuit (209) also becomes a signal with a short cycle, and the ON / OFF repetition cycle of the transistor (206) becomes extremely short.

On the other hand, transistors (203) (20
In 4), when one is in the ON state and the other is in the OFF state, and when the transistor (203) is in the ON state, the constant current I ₁ from the first constant current source (201) is the transistor (203). And is drawn into the second constant current source (202) by a constant current I ₂ . Then, when the transistor (206) is in the OFF state, the difference (I ₁ −I ₂ ) between the constant current I ₁ and the constant current I ₂ charges the capacitor (205). However, during normal operation of the brushless motor, the transistor (206) is repeatedly turned on and off in a very short cycle, so that the transistor (206) is charged before the charging potential of the capacitor (205) becomes the reference voltage. 206) is discharged through. As a result, the output of the comparator (215) is not inverted and continues to output the H-level potential. Therefore, the transistor (20
An L level potential is applied to the base of 3) to keep the ON state, and an L level is applied to the base of the transistor (204) to keep the OFF state.
21) keeps ON, the drive circuit keeps operating, and the brushless motor keeps operating normally.

Further, when the brushless motor is in normal operation and the motor is locked for some reason, the output from the detection means for detecting the rotational position of the rotor remains at the H or L level, so the AND circuit (209 ) Output remains L level, and the transistor (206) is in OFF state. Therefore, the electric charge charged in the capacitor (205) is not discharged through the transistor (206), and the charge potential rises. When this charging potential exceeds the reference voltage, the output from the comparator (215) is inverted to L level. As a result, the H level is applied to the base of the transistor (203) to turn it off, and the transistor (204)
The L level is applied to the base of the transistor to turn it on, and the transistor (221) is turned off to deactivate the drive circuit. At this time, the reference voltage applied to the non-inverting input terminal of the comparator (215) drops to a voltage determined by the resistors (213) (214). When the transistor (203) is turned off, the charging current does not flow in the capacitor (205), and the charging charge is discharged through the second constant current source (202). Then, when the charging potential of the capacitor (205) drops below the voltage determined by the resistors (213) (214), the output from the comparator (215) is inverted to the H level. As a result, the transistors (203) and (221) are turned on and the transistor (204) is turned off to activate the drive circuit and start charging the capacitor (205). When the rotor of the brushless motor is rotated by the operation of the drive circuit, the brushless motor operates in the same manner as in the normal rotation state described above.
When the rotor is in the locked state, the capacitor (205) continues to be charged, and operates in the same manner as above, rendering the drive circuit inoperative. The non-operating state and the operating state of the drive circuit are repeated while the rotor is in the locked state.

[Problems to be Solved by the Invention] However, in the burnout prevention device configured as described above, when the rotor is locked, the condenser (205)
The duty ratio between the charging time and the discharging time of is the constant current I ₁ of the _first constant current source (201) and the constant current of the second constant current source (202).
Since it is determined by I ₂ , there is a problem that the duty ratio cannot be reduced so much that it cannot be used for a motor that generates a large amount of heat.

The present invention has been made in view of the above points, and an object thereof is to obtain a coil burnout prevention device for a motor having a small duty ratio between a charging time and a discharging time, which can be used for a motor having a large amount of heat generation. is there.

[Means for Solving the Problem] A coil burnout prevention device for a motor according to the present invention receives a position detection signal indicating a magnetic pole position of a rotor of a motor, and in accordance with the position detection signal, an energized state of a coil of the motor. A drive circuit for controlling the capacitor, a capacitor, a discharge pulse generation circuit that receives the position detection signal and generates a pulse in synchronization with the position detection signal, and an output pulse of the discharge pulse generation circuit discharges the charge stored in the capacitor. When receiving the charging / discharging potential of the discharging transistor and the capacitor, when the charging / discharging potential becomes equal to or higher than the first potential, the drive circuit is deactivated and is equal to or lower than the second potential lower than the first potential. And a drive circuit control section that is in an operating state, and an output of this drive circuit control section, and when the output of the drive circuit control section becomes equal to or higher than the first potential, A timer circuit having a constant current circuit for discharging the charged electric charge with a constant current and charging the capacitor with a constant current according to the output when the voltage becomes equal to or lower than the second potential of the drive circuit control unit, and the drive circuit operates. In the state, a charging current is supplied to the capacitor of the timer circuit, and in a non-operating state, the supply of the charging current is stopped, and a charging time shortening circuit that shortens only the charging time to the capacitor is provided. .

[Operation] In the present invention, the charging time shortening circuit supplies the charging current to the capacitor of the timer circuit when the motor of the rotor is locked, and shortens only the charging time of the capacitor by driving the capacitor while driving the driving circuit. The duty ratio between the operating state time and the non-operating state time of the circuit is reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. 1. In the figure, (1) is a resistor connected between a power supply terminal Vcc and a node A, and (2) is the node described above. It is a constant voltage element composed of a Zener diode connected between A and ground, and keeps the node A at a constant voltage V1. (3) is a resistor connected to the node A, and (4) is position detecting means for outputting a position detection signal indicating the magnetic pole position of the rotor of the brushless motor. In this embodiment, it is connected to the resistor (3). , A Hall element disposed in proximity to the rotor composed of a permanent magnet is used. (5) is a stator coil (10) of the motor according to the position detection signal from the position detecting means.
A drive circuit for controlling the energization state of (11) receives an input amplifier (6) for amplifying the position detection signal and an amplified position detection signal of the input amplifier (6), and receives a first position in response to the amplified position detection signal. A pre-stage drive section (7) that outputs a selective output, that is, a complementary signal to the first and second output terminals, a first output terminal of the pre-stage drive section (7), and a first stator coil (1
0) and a first output amplifier (8) connected between the first output amplifier (8) and the second stator coil (11) between the second output terminal of the pre-stage drive section (7) and the second output terminal. 2 output amplifiers (9)
It consists of and. (12) is a diode connected between the power supply terminal Vcc and the first and second stator coils (10) and (11), and (14) is the position from the hall element which is the position detecting means (4). A discharge pulse generation circuit that receives a detection signal and generates a pulse every inversion of this position detection signal, (15)
Is a discharge transistor that receives the output of this discharge pulse generation circuit (14) at its base, (16) is a capacitor connected in parallel with this discharge transistor (15), and (17) is a constant current to this capacitor (16). The constant current circuit to supply the sixth
The circuit shown in the figure is composed of two constant current sources and a differential amplifier circuit. (18) is this capacitor (1
Upon receiving the charge / discharge potential of 6), the drive circuit (5) is brought into a non-operating state when the charge / discharge potential becomes equal to or higher than the first potential Vref1, and becomes lower than the second potential Vref2 lower than the first potential Vref1. Then, the drive circuit control section which is in the operating state also controls the constant current circuit (17), and is composed of the comparator and the two resistors of the circuit shown in FIG. 6, and the capacitor (16), The discharge pulse generating circuit (14), the discharging transistor (15) and the constant current circuit (17) form a timer circuit (19), and a power supply for driving is supplied from a node A. Reference numeral (20) is a charging time shortening circuit for shortening the charging time of the capacitor (16) by supplying the charging current to the capacitor (16) of the timer circuit (19) when the drive circuit (5) is in the operating state. , Diodes (21) and (22) respectively connected to the output terminals of the first and second output amplifiers (8) and (9), and connected in series between the common connection point of these diodes and the node A. Resistors (23) (24),
A transistor (25) whose base is connected to the connection point of these resistors (23) and (24) and whose emitter is connected to the node A, and a resistor connected between the collector of this transistor (25) and the node B. It is composed of (26).

Next, the operation of the brushless motor burnout prevention device configured as described above will be described. First, the case where the brushless motor is normally rotating will be described. When the brushless motor is normally rotating, the detection means for detecting the rotation position of the rotor of the brushless motor, that is, the output signal (from the H level and the L level) corresponding to the magnetic field of the rotor from the Hall element (4). Signal) is input to the input amplifier (6) as a signal having a very short period. The amplification detection signal amplified by this input amplifier (6) is the front-stage drive section (7).
Is input to the first and second output amplifiers (8) and (9) to selectively drive the first and second stator coils (10) and (11).
Is selectively energized to rotate the rotor in one direction.

On the other hand, the detection signal from the Hall element (4) is also input to the discharge pulse generating circuit (14), and the output from this discharge pulse generating circuit (14) also becomes a signal of a short cycle, which causes the discharge transistor (15) to discharge. The repetition cycle of ON and OFF is also very short. In the initial state, since the drive circuit control section (18) outputs the H level, the constant current circuit (17)
A constant current flows from here to the capacitor (16), and when the discharging transistor (15) is in the OFF state, this constant current charges the capacitor (16). However, when the brushless motor is operating normally, the discharge transistor (15) is repeatedly turned on and off in a very short cycle, so the charging potential of the capacitor (16) becomes the first reference voltage Vref1. Before, it is discharged through the discharging transistor (15).
As a result, the output of the comparator of the drive circuit control section (18) is not inverted and continues to output the H level potential.
Therefore, the pre-stage drive unit (7) maintains the operating state, and the stator coils (10) and (11) of the brushless motor are energized to continue normal operation.

In addition, if the brushless motor is operating normally and motor lock occurs for some reason, the Hall element (4)
The output from the discharge pulse generation circuit (14) remains at the L level and the discharge transistor (15) is in the OFF state. Therefore, the electric charge charged in the capacitor (16) is not discharged through the discharging transistor (15), and the charging potential rises. At this time, since the drive circuit (5) is still in the operating state, one output of the first and second output amplifiers (8) and (9) is at the L level, so that the charging time shortening circuit (2
The base potential of the transistor (25) of 0) is L level, the transistor (25) is turned on, and the charging current is supplied to the capacitor (16). And the capacitor (1
When the charging potential in 6) is shortened by the charging time shortening circuit (20) and exceeds the first reference voltage Vref1, the output from the comparator of the drive control circuit brushless motor (18) is inverted to L level. As a result, the pre-stage drive section (7) of the drive circuit (5) is made inoperative. At this time, the reference voltage applied to the input terminal of the comparator of the drive circuit control section (18) drops to the second potential Vref2. On the other hand, the constant current circuit (17) discharges the L level output of the drive circuit control section (18) with a constant current at the node B, while the first and second output amplifiers (8) and (9) are discharged. Since both outputs are at H level, the base potential of the transistor (25) of the charging time shortening circuit (20) is at H level, and no charging current flows from the charging time shortening circuit (20) to the capacitor (16). . Therefore, the charge of the capacitor (16) is discharged through the constant current circuit (17). When the charging potential of the capacitor (16) drops below the second reference potential Vref2, the output from the comparator of the drive control circuit section (18) is inverted to H level. As a result, the pre-stage drive unit (7) of the drive circuit (5) is in the operating state, and the constant current from the constant current circuit (17) and the charging current from the charging time shortening circuit (20) charge the capacitor (16). Begin to. Drive circuit (5)
The operation of the first and second stator coils (8)
In (9), when the brushless motor rotor is rotated by being alternately energized, it operates in the same manner as in the normal rotation state described above. If the rotor remains locked, the capacitor (16) will continue to be charged and operate in the same manner as above, rendering the drive circuit (5) inoperative. The non-operating state and the operating state of the drive circuit (5) are repeated while the rotor is in the locked state.

That is, as indicated by the solid line A in FIG. 2, the potential V2 of the node B repeats the charging / discharging potential below the second reference potential Vref2 during normal rotation of the brushless motor. It rises to the potential Vref1, then falls to the second reference potential Vref2, and the potential between the first and second reference potentials Vref1 and Vref2 is repeated during motor lock.
At this time, the charging time T1 (the potential of the node B is the second reference potential)
The time from Vref2 to the first reference potential Vref1, the period during which the drive circuit (5) is in the operating state) is the charging time T1 '(see FIG. 2) when the charging time shortening circuit (20) is not provided. It is shorter than the discharge time T2 (the time until the potential of the node B changes from the first reference potential Vref1 to Vref2, the period when the drive circuit (5) is in the non-operation state) while being shorter than the charging time. It is the same as the discharge time T2 when the shortening circuit (20) is not provided. Therefore, the duty ratio between the charging time and the discharging time becomes small, and it can be used for a brushless motor that generates a large amount of heat, and it is difficult to cause a burnout accident when the brushless motor is locked.

FIG. 3 is a partial circuit diagram showing a second embodiment of the present invention. Instead of connecting to the node A as the driving power source of the charging time shortening circuit (20) in comparison with the embodiment shown in FIG. The power supply terminal Vc to which the stator coil (10) (11) is connected to
It is connected to c.

With this configuration, if the potential of the power supply terminal Vcc fluctuates, the charging time reduction circuit (20)
The charging current from also fluctuates. That is, when the potential of the power supply terminal Vcc increases, the energizing current of the stator coils (10) and (11) increases, the starting torque increases, and it becomes easier to start, but the amount of heat generation increases. However, the charging current from the charging time shortening circuit (20) is also large, and the charging time can be further shortened to suppress the amount of heat generation. On the contrary, when the potential of the power supply terminal Vcc decreases, the amount of heat generated decreases but the starting torque also decreases. However, since the charging current from the charging time shortening circuit (20) is also small and the charging time is long, it is possible to compensate for the difficulty in starting.

FIG. 4 is a diagram showing a third embodiment of the present invention.
In contrast to the one shown in the figure, first and second output amplifiers (8) and (9) are connected to resistors (8a) and (9a) and transistors (8).
b) A diode (27) composed of (9b), in which the charging time reduction circuit (20) is connected to the output terminal of the pre-stage drive section (7).
(28) and a resistor (26) connected between the common connection point of these diodes (27) and (28) and the node B.

Even in the case of such a configuration, the same operation as that of the embodiment shown in FIG. 1 is obtained and the same effect is obtained, and the drive power supply of the charging time shortening circuit (20) is connected to the power supply terminal Vcc. Since the output of the front-stage driving section (7), which follows the electric potential and is approximately similar, is output, the power supply terminal Vcc is the same as in the second embodiment.
It also has an effect that the charging time can be changed in accordance with the change of.

FIG. 5 is a partial circuit diagram showing a fourth embodiment of the present invention. Compared to the third embodiment shown in FIG. 4, the charging time shortening circuit (20) is provided with two resistors (29) (30). ) And has the same effect as that of the third embodiment.

As described above, the present invention receives the position detection signal indicating the magnetic pole position of the rotor of the motor, and controls the energization state of the coil of the motor according to the position detection signal, A capacitor, a discharge pulse generation circuit that receives the position detection signal and generates a pulse in synchronization with the position detection signal, and a discharge transistor that discharges the charge stored in the capacitor by the output pulse of the discharge pulse generation circuit, Drive that receives the charge / discharge potential of the capacitor and renders the drive circuit inoperative when the charge / discharge potential becomes equal to or higher than the first potential, and activates the drive circuit when the charge / discharge potential is equal to or lower than the second potential lower than the first potential. The output of the circuit control unit and the drive circuit control unit is received, and the electric charge charged in the capacitor is discharged at a constant current in accordance with the output when the voltage becomes equal to or higher than the first potential. A timer circuit having a constant current circuit for charging the above capacitor with a constant current according to the output when the voltage falls below the second potential of the drive circuit control unit, and the capacitor of the timer circuit when the above drive circuit is in an operating state. Supply the charging current to
When the motor is locked, the drive circuit operates in the capacitor of the timer circuit when the motor is locked, because the charging time shortening circuit that stops the supply of this charging current in the non-operating state to shorten only the charging time to the capacitor is provided. The charging time can be shortened by supplying the charging current only when the driving circuit is in operation, the duty ratio between the operating state time and the non-operating state time of the drive circuit is reduced, and even the motor with large heat generation burns out. This has the effect of preventing

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing a change in potential V2 at a node B of FIG. 1, and FIG. 3 is a second embodiment of the present invention. 4 is a partial circuit diagram showing the third embodiment of the present invention, FIG. 5 is a partial circuit diagram showing the fourth embodiment of the present invention, and FIG.
FIG. 1 is a circuit diagram showing a conventional coil burnout prevention device for a motor. In the figure, (4) is position detecting means which is a Hall element,
(5) is a drive circuit, (10) and (11) are stator coils, and (1
4) is a discharge pulse generation circuit, (15) is a discharge transistor, (16) is a capacitor, (17) is a constant current circuit, (18)
Is a drive circuit controller, (19) is a timer circuit, and (20) is a charging time shortening circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A drive circuit for receiving a position detection signal indicating a magnetic pole position of a rotor of a motor, a capacitor for controlling an energization state of a coil of the motor according to the position detection signal, and a position detection signal, A discharge pulse generation circuit that generates a pulse in synchronization with this position detection signal, a discharge transistor that discharges the charge stored in the capacitor by the output pulse of the discharge pulse generation circuit, and a charge / discharge potential of the capacitor are received. A drive circuit control unit that puts the drive circuit into a non-operation state when the charge / discharge potential is equal to or higher than a first potential, and an operation state when the charge / discharge potential is equal to or lower than a second potential lower than the first potential, and the drive circuit control unit Of the output of the drive circuit control unit, and the charge of the capacitor is discharged with a constant current in accordance with the output when the output of the drive circuit is higher than the first potential. When the driving circuit is operating, the charging circuit supplies a charging current to the capacitor of the timer circuit when the driving circuit is operating, and when the driving circuit is not operating, A coil burnout prevention device for a motor, comprising a charging time shortening circuit for stopping the supply of the charging current and shortening only the charging time for the capacitor.