JPH1042586A - Motor drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive circuit which can stop a motor in case of failure, without generating erroneous stoppings, and is capable of surely preventing the motor and the driving part from being damaged by burning. SOLUTION: In this motor drive circuit, a burning preventive means which stops a motor, based on the magnitude of current flowing through a driving part 4 for applying current into the motor is constituted of first and second over-current detecting circuit 6, 7 for detecting that it has reached first and second over-current determination values, first and second over-current generating time determining circuit 8, 9 for determining that the period of an over- current generating condition detected by the first and the second over-current detecting circuits has reached first and second determination times, and a latch circuit 11 for inputting first and second motor stopping signals which are outputted by the first and the second over-current generating time determining circuits through an OR circuit 10. The first over-current determination value is set to be smaller than the second over-current determination value, and the first determining time is set to be longer than the second determining time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a brushless motor, and more particularly to a motor drive circuit capable of accurately detecting an abnormality in a motor and a driver and preventing burnout of the motor and its peripheral circuits.

[0002]

2. Description of the Related Art Conventionally, in a motor drive circuit, a technique for detecting an abnormality and stopping the motor is disclosed in Japanese Unexamined Patent Publication No.
There is one disclosed in Japanese Patent No. 276787. Next, a conventional technique disclosed in the publication will be described with reference to FIG. This conventional example shows a drive circuit for a brushless motor, and this drive circuit comprises a Hall element 101 (Ha, H
b, Hc), a Hall amplifier 102 that amplifies the signal of the Hall element, and a control unit 103 that receives the output of the Hall amplifier 102 and controls the exciting current supplied to the coils U, V, and W of the motor. The control unit 103 is connected to a driver unit 104 for supplying an exciting current to the coils U, V, W. An exciting current (hereinafter referred to as motor current) supplied to the motor by the driver 104 flows to the ground via the resistor 105, and a voltage V generated at one end of the resistor 105.
mi is compared with a reference voltage Vd generated by a resistor 106 and a diode 107 in a comparator 108. The comparator 108 outputs a motor stop command signal when Vmi> Vd, and supplies this to the control unit 103 to stop the motor.

[0003] Next, the operation of the motor drive circuit thus configured will be described in more detail with reference to FIG.
Assuming that the current flowing through the motor is Im and the resistance value of the resistor 105 is Rmi, the voltage Vmi generated at one end of the resistor 105 is expressed by the following equation (1). Vmi = Im × Rmi (1) When the motor is rotating in a steady state, the value of Rmi is set so that Vmi <Vd as shown in FIG. deep. When an abnormality such as an excessive load is applied to the motor, the motor current increases, and Vmi increases as shown in FIG. When Vmi reaches the reference voltage Vd, a motor stop command signal is output from the comparator 108, and the motor is immediately stopped to prevent the motor from burning.

[0004]

In the conventional brushless motor drive circuit shown in FIG. 7, it is important to set the resistance Rmi of the resistor 105. If the value of Rmi is too large, the motor will stop erroneously, and if the value of Rmi is too small, the motor stop function at the time of abnormality will not operate. This will be described in more detail with reference to FIG. When Rmi is large, the motor reacts sensitively to the abnormality of the motor and can stop the motor. On the other hand, as shown in FIG. 9, the motor also reacts at the start when the motor current increases and the motor may stop erroneously. . Furthermore, not only when starting the motor, but also when switching the rotation direction of the motor where the current increases, there is a possibility that the motor will stop erroneously. Conversely, when Rmi is small, normal startup is performed without erroneous stop. However, a motor stop signal may not be output in response to a motor abnormality, and the motor or the like may be burned.

[0005] The present invention has been made to solve the above-mentioned problems in the conventional motor drive circuit.
SUMMARY OF THE INVENTION The object of the present invention is to provide a motor drive circuit capable of reliably stopping a motor when an abnormality occurs without erroneous stop and reliably preventing burnout of the motor and its driver circuit. . In addition, the invention of claim 2 includes, among the objects of the invention of claim 1,
It is an object of the present invention to provide a motor drive circuit capable of setting a stop condition of a motor with high accuracy.
It is an object of the present invention to provide a motor drive circuit capable of easily changing a motor stop condition.

[0006]

According to a first aspect of the present invention, there is provided a control unit for controlling a current supplied to a motor based on information on a rotational position of the motor. In a motor drive circuit having a driver unit that receives an output signal and supplies a current to the motor, and a burnout prevention unit that stops the motor according to the magnitude of the current flowing through the driver unit, the burnout prevention unit includes a first overcurrent. A first overcurrent detection circuit for detecting that the determination value has been reached, and a first overcurrent detection circuit for determining that a period of the overcurrent occurrence state detected by the first overcurrent detection circuit has reached a first determination time. The overcurrent occurrence time determination circuit, the second overcurrent detection circuit for detecting that the second overcurrent determination value has been reached, and the period of the overcurrent occurrence state detected by the second overcurrent detection circuit. Second
A second overcurrent occurrence time determination circuit for determining that the determination time has been reached, a first motor stop signal output from the first overcurrent occurrence time determination circuit, and a second overcurrent occurrence time determination circuit An OR circuit for performing an OR operation on a second motor stop signal output from the OR circuit, and a latch circuit for holding an output signal of the OR circuit, wherein the first overcurrent determination value is the second overcurrent The first determination time is set to be longer than the second determination time and is smaller than the determination value to configure the motor drive circuit.

As described above, the first and second overcurrent detection circuits and the first and second overcurrent occurrence time determination circuits are provided, and the first overcurrent determination value is set to be larger than the second overcurrent determination value. By setting the first determination time to be shorter than the second determination time, erroneous stop can be prevented for short-time overcurrent such as when starting the motor or switching the rotation direction. Motor can be reliably stopped against overloading of the motor, and furthermore, when an excessive current such as a through current in the driver section occurs, the driver section can be turned off in a short time to prevent burnout. .

According to a second aspect of the present invention, in the motor drive circuit according to the first aspect, the first and second overcurrent occurrence time determination circuits are respectively provided by the first and second overcurrent detection circuits. Counting is started based on the clock signal from the timing at which the overcurrent is detected, reset when the overcurrent is no longer detected, and when the count advances to the first determination time and the second determination time, the respective It is characterized by comprising a first and a second timer in which the state of the output signal changes. With this configuration, the motor stop timing can be managed based on the clock, so that the motor stop condition can be set with little variation and with high accuracy.

According to a third aspect of the present invention, in the motor drive circuit according to the first aspect, the first and second overcurrent occurrence time determination circuits are respectively provided by the first and second overcurrent detection circuits. First and second integration circuits that start integration from a timing at which an overcurrent is detected, a first comparator that compares an output signal of the first integration circuit with a predetermined voltage value, and a second integration circuit And a second comparator for comparing the output signal of the circuit with a predetermined voltage value. In the first and second overcurrent occurrence time determination circuits configured as described above, the stop condition of the motor can be easily changed by changing the constants and the like of the elements constituting the integration circuit.

[0010]

Next, an embodiment will be described. First, a basic embodiment will be described with reference to FIG. In FIG. 1, a Hall element 1 (Ha, Hb, H
c) is an element for detecting the rotational position of the motor,
The output of the Hall element 1 is amplified by the Hall amplifier 2. The output of the hall amplifier 2 is given to the control unit 3, which generates a current supply timing signal for driving the motor. The timing signal output from the control unit 3 is applied to a driver unit 4 including transistors Q1 to Q6 that supply current to coils U, V, and W in the motor, and drives the motor. The motor current flowing through the coils U, V, W passes through the resistor 5 and goes to the ground. Assuming that the motor current flowing through the coils U, V and W is Im and the resistance value of the resistor 5 is Rmi, the voltage Vmi generated at one end of the resistor 5
Is Vmi = Im × Rmi.

The signal of the voltage Vmi generated at one end of the resistor 5 is input to a first overcurrent detection circuit 6 and a second overcurrent detection circuit 7. The first overcurrent detection circuit 6 and the second overcurrent detecting circuit 7, independent determination voltage value V ₁ and V ₂ are set. The first overcurrent detection circuit 6 compares the determined voltage value V ₁ and the input voltage Vmi. In other words,
It is determined whether or not the motor current Im exceeds a predetermined current value I ₁ = V ₁ / Rmi, and if it exceeds I ₁ , it is output as a first overcurrent detection signal. Similarly, the second overcurrent detection circuit 7 determines that the motor current Im has a predetermined current value I ₂ = V ₂ / Rmi
Determines whether or not beyond, if exceeding the I _2, second
Output as overcurrent detection signal.

The result of determination by the first overcurrent detection circuit 6 is input to a first overcurrent occurrence time determination circuit 8. First overcurrent time decision circuit 8, when continuously input without first overcurrent detection signal during a predetermined determination time T _1, changes,
A first motor stop signal is output. Similarly, the determination result of the second overcurrent detection circuit 7 is input to the second overcurrent occurrence time determination circuit 9. Second overcurrent time decision circuit 9, when continuously input without second overcurrent detection signal during a predetermined determination time T _2, changes, and outputs a second motor stop signal. The first motor stop signal and the second motor stop signal are OR-processed by an OR circuit 10, and the output signal is input to a latch circuit 11. That is, when at least one of the first motor stop signal and the second motor stop signal is output, the information is held in the latch circuit 11.
The information held here is input to the control unit 3 as a motor stop command signal. The control unit 3 receives the stop command signal, turns off the transistor in the driver unit 4, and stops driving the motor.

In the motor drive circuit having the above-described configuration, the determination voltage values V ₁ and V ₂ and the determination times T ₁ and T 2
₂ is set to an appropriate value while maintaining the relationship of V ₁ <V ₂ , T ₁ > T ₂ , thereby preventing erroneous stop when starting the motor or switching the rotation direction, and furthermore, when the motor is abnormal. Motor can be reliably stopped when the error occurs. Further, even when a through current is generated inside the driver unit 4 due to an abnormality in the control unit 3 or the driver unit 4, the driver unit 4 can be turned off by detecting the through current and the burnout of the driver unit 4 can be prevented.

Next, a specific first embodiment will be described with reference to FIG. 2, the same or corresponding components as those in the basic embodiment shown in FIG. 1 are denoted by the same reference numerals. In FIG. 2, the output of the Hall element 1 is amplified by the Hall amplifier 2 and
Is output to the control unit 3, and the control unit 3 generates a current supply timing signal for driving the motor, and the timing signal output from the control unit 3 supplies currents to the coils U, V, W in the motor. Is supplied to the driver unit 4 that supplies the motor and drives the motor. Then, the motor current flowing through the coils U, V, W passes through the resistor 5 to the ground, and if the motor current flowing through the coils U, V, W is Im, and the resistance value of the resistor 5 is Rmi, one end of the resistor 5 Generated voltage Vmi
Is the same as the basic embodiment shown in FIG. 1 in that Vmi = Im × Rmi.

The signal of the voltage Vmi generated at one end of the resistor 5 is input to one input terminal of a first comparator 23 whose other input is connected to a power supply 21 having a voltage value V ₁ , and further the other input is provided. Is connected to a power supply 22 having a voltage value V _2.
Is input to one of the input terminals. Then, a first overcurrent detection signal and a second overcurrent detection signal are output from the first and second comparators 23 and 24, and the first and second overcurrent detection signals are output by the first and second timers. Input to 25 and 26 respectively. Further, a first motor stop signal and a second motor stop signal are output from the first and second timers 25 and 26,
These first and second motor stop signals are input to the OR circuit 10.

Next, the operation of the first and second comparators 23 and 24 and the first and second timers 25 and 26 will be described with reference to the timing chart of FIG. FIG. 3 (A), (B), the motor current such that Vmi> V ₁ is generated, from the first comparator 23 high level is outputted as a first overcurrent detection signal. The first overcurrent detection signal is inputted to the first timer 25, the first timer 25, upon receiving the first overcurrent detection signal, that is, from when the state of Vmi> V _1, the clock signal (CLK ) starts counting the time base, the first overcurrent detection signal when the state had a Vmi <V ₁ becomes L level, the first timer
25 is reset. The first timer 25, at the time of the count until the determination time T ₁ which is set in advance, the output becomes high level. The output of the first timer 25 is used as a first motor stop signal. That is, during the T ₁ preset time, when the state continues of Vmi> V _1, a first motor stop signal is output. Conversely, Vmi> V
Even State ₁ has occurred, the period is shorter than T _1, the first motor stop signal is not output.

On the other hand, the signal of the voltage Vmi generated at one end of the resistor 5 is also input to one input terminal of a second comparator 24 whose other input is connected to a power supply 22 having a voltage value V ₂ . Second
The output signal of the comparator 24 is similarly supplied to a second timer 26, and is output from the second timer 26 as a second motor stop signal. However, the time determination previously set in the second timer 26 is set to T _2.

The first motor stop signal and the second motor stop signal, which are the outputs of the first timer 25 and the second timer 26, are input to the OR circuit 10, and the output is input to the latch circuit 11 which holds the state. Is done. That is, when at least one of the first motor stop signal and the second motor stop signal is output, the latch circuit 11 holds this information. Further, the information held here is given to the control unit 3 as a motor stop command signal.

Next, the overall operation in the present embodiment will be described with reference to FIG. The respective determination voltages V ₁ and V ₂ applied to the first comparator 23 and the second comparator 24 are defined as V ₂ > V ₁
And Further, the determination times T ₁ and T ₂ set for the first timer 25 and the second timer 26 respectively are set as T ₁ > T ₂ . When starting from a state where the motor is stopped,
An excessive current flows through the motor as an inrush current at the time of starting. When the motor starts and the rotation is in a steady state, the current of the motor decreases. When an excessive load is applied to the motor while the motor is rotating, an overcurrent is generated in the motor. When the control unit 3 and the driver unit 4 are operating normally, FIG.
Q1 and Q2, Q3 and Q4 in the driver section 4
The transistors are not turned on at the same time by the combination of Q5 and Q6, but the operation of the control unit 3 is abnormal for some reason or one of the transistors of the driver unit 4 is always on. An extremely large through current limited only by the ON resistance and the resistance 5 of the PNP transistor and the NPN transistor of the driver unit 4 flows.

When the motor is in a steady state, Vmi <V
_{1. When} an overcurrent occurs due to an increase in motor load, Vmi>
And Vmi <V _2, further, when generation of a through current due to abnormality in the control unit 3 or the driver unit 4, Vmi> in V ₁ V
V ₁ and V ₂ are set so as to be ₂ . The determination time T ₁ to be set in the first timer 25, the motor startup starting current is greater than the period occurring. on the other hand,
Determination time T ₂ to set the second timer 26 is set smaller than the period of generation of a through current.

As shown in FIG. 4, when applying a start from a state where the motor is stopped, the motor excessive current flows as inrush current during startup, Vmi> period of V _1, the first comparator 23 the output of the high level, and therefore the period is shorter than the determination time T ₁ to be set in the first timer 25, from the first timer 25, no first motor stop signal is generated. Therefore, normal startup is performed without erroneous stop. At the time of occurrence of an overcurrent by the motor load increases, at the time this occurrence period exceeds the determination time T ₁ set in the first timer 25, the first motor stop signal is generated from the first timer 25, OR circuit 10 And a latch circuit 11 to the controller 3 as a motor stop command signal. The control unit 3 receives the stop command signal and stops driving the motor. When the motor is stopped, Vmi <V _1, and the first timer 25 would be reset, since the latch circuit 11 holds the stop instruction signal of the motor, restart unless it is reset the latch circuit 11 is It does not take.

The abnormal by the through current of the control unit 3 or the driver unit 4 occurs and a Vmi> V _2, at the time this occurrence period exceeds the determination time T ₂ set in the second timer 26, the second timer A second motor stop signal is generated from 26 and is supplied to the control unit 3 as a motor stop command signal via the OR circuit 10 and the latch circuit 11. The control unit 3 receives this command signal and stops driving the motor. When the motor is stopped, Vmi <V _2, and the second timer 26 would be reset, since the latch circuit 11 holds the stop instruction signal of the motor, restart unless it is reset the latch circuit 11 is It does not take.

As described above, according to the present embodiment, erroneous stop at start-up is prevented, and when the load on the motor increases and an excessive current flows through the motor, the motor is surely stopped. Burnout of the motor and its peripheral components can be prevented. Also, when a through current occurs due to an abnormality in the motor drive circuit, the motor is reliably stopped,
Burnout of the motor and its peripheral components can be prevented. Furthermore, since the timing at which the motor stop command is issued is managed based on the clock, it is possible to set a highly accurate motor stop condition with little variation.

Next, a second specific embodiment will be described with reference to FIG. 5, the same components as those of the first embodiment shown in FIG. 2 are denoted by the same reference numerals. In this embodiment, the functions of the first timer and the second timer in the first embodiment are configured to be realized in an analog manner. Coil U, V, W
Current flowing through the resistor 5 to the ground via the resistor 5, and assuming that the resistance value is Rmi, the voltage Vmi generated at one end of the resistor 5 is Vmi = Im × Rmi. Is the same as Voltage Vmi generated at one end of resistor 5
Is input to one input terminal of an open collector output first comparator 31 connected to a power supply 21 having the other input having a voltage value V ₁ . The output of the first comparator 31 controls the integration start and reset of the integration circuit including the current source 33 and the capacitor 34. Vmi <period V ₁ was output becomes the low level of the first comparator 31, integrating circuit is in the reset state. vice versa,
When the vmi> V _1, the output of the first comparator 31 starts becomes integral to the high impedance. This integration signal is input to one input terminal of a third comparator 38, the other of which is connected to the power supply 37. The function of the first timer in the first embodiment is realized by the integration circuit including the current source 33 and the capacitor 34 and the third comparator 38.

Similarly, the voltage Vmi generated at one end of the resistor 5
Is input to one input terminal of an open collector output second comparator 32 whose other input is connected to the power supply 22 having the voltage value V _{2, and the} output of the second comparator 32 is It controls the integration start and reset of the integration circuit composed of the capacitor 36. A fourth circuit in which an integration circuit including the current source 35 and the capacitor 36 is inputted, and a power source 37 is connected to one end of the integration circuit.
The function of the second timer in the first embodiment is realized by the comparator 39.

Next, referring to FIG. 6, it will be described that the integrating circuit including the current source 33 and the capacitor 34 and the circuit including the third comparator 38 perform the same function as the first timer in the first embodiment. explain. Vmi <period V ₁ was output becomes the low level of the first comparator 31, integrating circuit is in the reset state.
Conversely, when the Vmi> V _1, the output of the first comparator 31 starts becomes integral to the high impedance. Assuming that the time from the start of integration is t, the current value of the current source 33 is I ₁ , and the capacitance value of the capacitor 34 is C ₁ , the integrated value Vi at time t is Vi = I ₁
× t / C ₁ . Therefore, this integral value is equal to the voltage value V _{3 of the} power supply 37 connected to the other terminal of the third comparator 38.
Is exceeded, the output of the third comparator 38 is inverted, and a first motor stop signal is output. The third comparator 38 after starting the integration
The time T ₁ until the output is inverted is T ₁ = C ₁ × V ₃
/ A I _1. Before the integral value Vi exceeds the voltage value V _3, <If you return to the state of V _1, the integral is reset, again, Vmi> Vmi integration starts from the time that the state of V _1.

The first motor stop signal obtained by the above operation is the same as that obtained by the first timer in the first embodiment. Here, an example in which the integrating circuit is configured by a current source and a capacitor has been described, but an integrating circuit configured by a resistor and a capacitor also performs a similar function. OR circuit 10 to which the first motor stop signal is input, and OR circuit 10
The function of the latch circuit 11 for holding the output signal is the same as that in the first embodiment, and the description is omitted. In addition, the overall operation of the configuration of the present embodiment is the same as that of the first embodiment, and the description is omitted.

In the present embodiment, similarly to the first embodiment, erroneous stop at start-up is prevented, and when the load on the motor increases and an excessive current flows through the motor, the motor is surely stopped. Can be stopped to prevent burnout of the motor and its peripheral parts. Further, even when a through current is generated due to an abnormality in the motor drive circuit, the motor can be reliably stopped, and burnout of the motor and its peripheral components can be prevented. Further, by changing the capacitance value for integration and the like, the stop condition of the motor can be easily changed, and the stop condition in the system can be optimized.

[0029]

According to the first aspect of the present invention, the motor is reliably stopped in the event of an abnormality without erroneous stop, and burnout of the motor and its driver is prevented. It is possible to realize a motor drive circuit that can surely prevent such a problem. According to the second aspect of the present invention, it is possible to provide a motor drive circuit capable of setting a motor stop condition with high accuracy, and further according to the third aspect of the present invention, particularly to stop the motor. A motor drive circuit whose conditions can be easily changed can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic embodiment of a motor drive circuit according to the present invention.

FIG. 2 is a circuit configuration diagram showing a specific first embodiment of the present invention.

FIG. 3 is a timing chart for explaining operations of a first comparator and a first timer according to the first embodiment shown in FIG. 2;

FIG. 4 is a timing chart for explaining the overall operation of the first embodiment shown in FIG. 2;

FIG. 5 is a circuit configuration diagram showing a specific second embodiment of the present invention.

FIG. 6 is a timing chart for explaining the operation of the second embodiment shown in FIG. 5;

FIG. 7 is a circuit configuration diagram showing a configuration example of a conventional motor drive circuit.

8 is a timing chart for explaining the operation of the conventional example shown in FIG.

FIG. 9 is an explanatory diagram for explaining a problem of the conventional example shown in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hall element 2 Hall amplifier 3 Control part 4 Driver part 5 Resistance 6 1st overcurrent detection circuit 7 2nd overcurrent detection circuit 8 1st overcurrent generation time judgment circuit 9 2nd overcurrent generation time judgment circuit 10 OR circuit 11 Latch circuits 21, 22 Power supply 23 First comparator 24 Second comparator 25 First timer 26 Second timer 31 First comparator 32 Second comparator 33, 35 Current source 34, 36 Capacity 37 Power supply 38 Third comparator 39 4th comparator

Claims (3)

[Claims] 1. A control unit for controlling a current supplied to a motor based on information on a rotational position of the motor, a driver unit receiving an output signal of the control unit and supplying a current to the motor, and a current flowing through the driver unit A motor drive circuit having burnout prevention means for stopping the motor depending on the size of the motor, wherein the burnout prevention means detects that the first overcurrent determination value has been reached; The period of the overcurrent occurrence state detected by the overcurrent detection circuit of FIG.
A first overcurrent occurrence time determination circuit for determining that the determination time has been reached, a second overcurrent detection circuit for detecting that a second overcurrent determination value has been reached, and a second overcurrent detection A second overcurrent occurrence time determination circuit for determining that a period of the overcurrent occurrence state detected by the circuit has reached a second determination time, and a first overcurrent occurrence time determination circuit output from the first overcurrent occurrence time determination circuit
ORing the motor stop signal of the second motor stop signal and the second motor stop signal output from the second overcurrent occurrence time determination circuit.
A latch circuit that holds an output signal of the OR circuit, wherein the first overcurrent determination value is smaller than the second overcurrent determination value, and the first determination time is equal to or less than the second overcurrent determination value. 2
A motor drive circuit set to be longer than the determination time. 2. The first and second overcurrent occurrence time determination circuits start counting based on a clock signal from a timing at which an overcurrent is detected by the first and second overcurrent detection circuits, respectively. It is reset when the overcurrent is no longer detected, and comprises a first and a second timer in which the state of each output signal changes when the count advances to the first determination time and the second determination time. The motor drive circuit according to claim 1, wherein: 3. The first and second overcurrent occurrence time determination circuits, wherein the first and second overcurrent occurrence time determination circuits start integration from a timing at which an overcurrent is detected by the first and second overcurrent detection circuits, respectively. , A first comparator that compares an output signal of the first integration circuit with a predetermined voltage value, and a second comparison that compares an output signal of the second integration circuit with a predetermined voltage value 2. The motor drive circuit according to claim 1, wherein the motor drive circuit comprises a motor.