JPH04197096A - Controller for brushless motor - Google Patents

Abstract

PURPOSE:To protect a switching transistor against burning due to chopping operation of a constant current chopper circuit by lagging the rising of a chopper signal thereby ensuring a long OFF interval of the switching transistor after chopping operation. CONSTITUTION:After chopping operation, a comparator 11 outputs a voltage determined in accordance with the voltage division ratio of resistors 12, 13 and a high level chopper signal is fed through a time constant circuit to the plus input terminal of a comparator 16. At that time, time to be elapsed before the potential of the chopper signal reaches a reference voltage Vs is extended through charge storing function of the capacitor 15 in the time constant circuit. According to the constitution, current is blocked perfectly from flowing into driving coils 2a-2c after turn OFF of switching transistors 4a-4c.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-speed, high-input brushless motor used, for example, in a blower, and particularly to a control device thereof.

[Prior art] At a high speed of 20,000 rpm or more and an input of 2
Commutator motors and induction motors are common as motors of 00W or higher. However, attempts have been made to replace these motors with brushless motors that have a high-speed, high-input configuration, and for this purpose, the resistance of the drive coil of the brushless motor is reduced, and a large current flows through the drive coil during startup. It is known that it is best to avoid this. .

As a conventional technique, a constant current chopper circuit is used to convert and detect the current flowing through a switching transistor connected in series with the drive coil into a voltage, and when the voltage value exceeds a reference value, the transistor is turned off. Techniques for keeping the current flowing through the drive coil constant are known.

[Problems to be Solved by the Invention] However, since the comparator of the constant current chopper circuit has good frequency characteristics, the switching speed of the switching transistor by this circuit is fast, and in practice, control approaching constant current control is performed.

Therefore, even though the switching transistor is turned off, the current flowing through the drive coil does not become completely zero from the time the switching transistor is turned off until it is next turned on. In addition,
FIG. 7 shows the chopper signal output by the constant current chopper circuit and the change in the current of the drive coil controlled by the chopper signal, and the current value A in the figure flows into the drive coil after the transistor is turned off. Shows the current value.

Further, B in FIG. 7 indicates the value of the chopper current C at which the chopping operation is performed.

Therefore, a loss occurs in the switching transistor due to the current flowing every time the constant current chopper circuit performs a chopping operation.

Here, if the resistance of the drive coil is R1, the power supply voltage is V, and the current is I, then immediately after the switching transistor is turned off, the voltage between the base and emitter of this transistor is (V-I R), so the current It is the value multiplied by I or the loss P of the switching transistor. That is, the loss P is given by the formula P-(V-IR)X'I.

From the above equation, this loss increases as the input power of the motor increases. Therefore, in a conventional configuration using a constant current chopper circuit in order to obtain a high-speed, high-input brushless motor, there is a high risk that the switching transistors will burn out due to the heat generated by the above-mentioned losses.

SUMMARY OF THE INVENTION An object of the present invention is to provide a brushless motor control device that can prevent switching transistors from burning out due to the chopping operation of a constant current chopper circuit.

[Means for Solving the Problems] In order to achieve the above object, a brushless motor control device according to the present invention includes switching transistors each connected in series with a drive coil, and a switching transistor that is rotated by excitation of the drive coil. a position detection means for detecting the rotational position of the rotor, and a position detection means connected downstream of the switching transistor, and outputs a low-level chopper signal that turns off the transistor when the detected voltage on the downstream side exceeds a reference voltage. At the same time, there is a constant current chopper circuit that outputs a high-level chopper signal that turns on the transistor when the detected voltage does not exceed the reference voltage, and a constant current chopper circuit that is connected to the output terminal of this chopper circuit to detect the rise of the high-level chopper signal. a delay means for delaying for a certain period of time, an output end connected to the base of the switching transistor, and an input end connected to an output end of the delay means and an output end of the position detection means, respectively; The device is equipped with an AND gate that turns on and off the switching transistor.

Furthermore, in order to achieve the same purpose, the present invention includes:
switching transistors each connected in series to the drive coil; a position detection means for detecting the rotational position of the rotor rotated by the excitation of the drive coil; and a position detection means connected downstream of the switching transistor to be detected on the downstream side. outputs a low-level chopper signal that turns off the transistor when the detected voltage exceeds a reference voltage, and outputs a low-level chopper signal that turns on the transistor when the detected voltage does not exceed the reference voltage; , a constant current chopper circuit having a reference voltage variable means for gradually increasing the reference voltage to a set value over time when the motor is started; and an output end connected to the base of the switching transistor, respectively, and an input end connected to the constant current chopper circuit. The output terminal of the constant current chopper circuit and the output terminal of the position detecting means are connected to each other, and an AND gate is provided to turn on/off the switching transistor.

Furthermore, in order to achieve the same purpose, the present invention includes:
switching transistors each connected in series to the drive coil; a position detection means for detecting the rotational position of the rotor rotated by the excitation of the drive coil; and a position detection means connected downstream of the switching transistor to be detected on the downstream side. outputs a low-level chopper signal that turns off the transistor when the voltage exceeds a reference voltage, and outputs a high-level chopper signal that turns on the transistor when the detected voltage does not exceed the reference voltage; a constant current chopper circuit having a reference voltage variable means for gradually increasing the reference voltage to a set value as the rotational speed of the rotor increases; The output terminal of the constant current chopper circuit and the output terminal of the position detecting means are connected to each other, and an AND gate is provided to turn on/off the switching transistor.

[Operations] In the invention of claim 1, when the switching transistor is turned on, current flows through the drive coil and the rotor is rotated. The position detection means detects the rotational position of the rotor and inputs the detection signal to the AND gate. The constant current chopper circuit converts and detects the current flowing through the switching transistor into a voltage, and outputs a low-level chopper signal that turns off the transistor when the voltage value exceeds a reference value, and also outputs a low-level chopper signal that turns off the transistor. If the reference voltage is not exceeded, a high-level chopper signal that turns on the transistor is output. The delay means delays the rise of the chopper signal for a certain period of time and inputs the delayed signal to the AND gate.

Therefore, every time a chopping operation is performed by the constant current chopper circuit and the switching transistor is turned off, the rise of the high-level chopper signal output from the constant current chopper circuit is delayed for a certain period of time by the delay means. This signal turns on the transistor.

Therefore, it is possible to ensure a long period of time when the switching transistor is completely turned off, and it is possible to prevent current from flowing through the switching transistor.

According to the second aspect of the invention, the reference voltage variable means included in the constant current chopper circuit gradually increases the reference voltage to a set value over time when the motor is started.

Therefore, even though current flows through the switching transistor each time the constant current switching circuit performs a chopping operation, the power supply voltage and current applied at that time can be reduced.

According to the invention of claim 3, the reference voltage variable means provided with the constant current circuit gradually increases the reference voltage to the set value by increasing the rotational speed of the rotor when starting the motor, etc. Therefore, even though current flows through the switching transistor every time the constant current chopper circuit performs a chopping operation, the power supply voltage and current applied at that time can be reduced.

[Example] Hereinafter, a first example of the present invention will be described with reference to FIGS. 1 and 2.

Reference numeral 1 in FIG. 1 denotes a constant voltage power supply circuit, which includes, for example, three drive coils 2a, 2b, 2c provided in a branless motor.
are connected to each other. These drive coils 2a to 2C attract the rotor magnet of the rotor 3 provided in the motor by their excitation, and rotate this rotor 3. Each of the drive coils 2a to 2C has a rotational speed of 2000 Orp.
In order to create a high-speed, high-input type branless motor with a power output of 200 W or more and an input of 200 W or more, it is made of a material with a small resistance value. The collectors of switching transistors 4a, 4b, and 4c are connected to each of the drive coils 2a to 2C separately.

In FIG. 1, 5a, 5b, and 5c are position detection means for detecting the rotational position of the rotor 3, respectively. These means 5a to 5C
is formed of a Hall element that detects the polarity of the rotor magnet, an operational amplifier that amplifies the output voltage of this element, and a waveform shaping circuit that waveforms the output of this amplifier to obtain a drive signal.

The output terminals of each of the detection means 58 to 5C are AND gates 6a and 6b provided correspondingly thereto.

6c. These gates 6
The output terminals of a to 6C are separately connected to the bases of the switching transistors 4a to 4c via resistors 7a to 7C, respectively. The output terminals of a constant current chopper circuit 8 are connected to the other input terminals of the AND gates 6a to 6C via delay means 9, respectively.

The constant current chopper circuit 8 includes the switching transistor 4
The detected voltage V is on the downstream side (that is, the emitter side) of a to 4C.
a current detection resistor 10 that generates the voltage a, an open collector comparator 11 that compares the detected voltage Va and the reference voltage vb, and a resistor 1 that generates the reference voltage vb.
2 and a variable resistor 13.

One end of the current detection resistor 10 is grounded, and the other end is connected to the emitters of the switching transistors 4a to 4c, respectively. The connection point between these emitters and the current detection resistor 10 is connected to the negative input terminal of the comparator 11. The resistor 12 and variable resistor 13 are
A series circuit is formed between the resistors 12 and 13, and the resistors 12 and 13 are connected to the positive input terminal of the comparator 11.

The delay means 9 includes a time constant circuit consisting of a resistor 14 and a capacitor 15, and an open collector type comparator 1 that compares the output of the comparator 11 that has passed through this circuit, that is, the Chotsuno Kuichi signal Vf, with a reference voltage Vs.
6, a resistor 17 and a variable resistor 18 for generating the reference voltage Vs, and a resistor 19 for outputting a chopper signal from the comparator 16.

An interconnection point between the resistor 14 and the capacitor 15 forming the time constant circuit is connected to the output terminal of the comparator 11 of the constant current circuit 8 and also to the positive input terminal of the comparator 16. The resistor 17 and the variable resistor 18 form a series circuit and are provided between plus Vcc and ground, and both resistors 17 and 18
The interconnection point of is connected to the negative input terminal of the comparator 16. The output terminal of the comparator 16 is connected to the other input terminals of the AND gates 6a to 6C, respectively. Furthermore, plus VCC is also connected via a resistor 19 to the other input terminals of the AND gates 6a to 6C.

When the power is turned on and the motor is started in the above configuration, at that point both comparators 11 and 16 are in a high level state, and AND gates 6a to 6C
are supplied with a voltage of plus Vcc through the resistor 19, respectively, so the AND gate to which the drive signal based on the detection of any one of the position detection means 58 to 5c is input opens, and the switching transistor connected to it is turned on. be done.

Therefore, the drive filter connected in series with this transistor is energized, and the rotor 3 starts rotating. below,
Based on the position detection of the rotor 3 by the position detection means 5a to 5c, the drive coils 2a to 2c are excited one after another.

In this drive, when the value of the current flowing through the drive coils 2a to 2c exceeds a predetermined value, the detected voltage Va obtained by converting the current into a voltage by the current detection resistor 10 becomes lower than the reference voltage Vb. Since it becomes large, the convergence signal 11 becomes low. Then capacitor 1
5 is discharged to the comparator 11, and the potential at the plus input terminal of the comparator 16 falls below the reference voltage Vs, so the comparator 16 also becomes a low state. Therefore, since AND gates 6a to 6C are all closed, each switching transistor 48 to 4C is turned off, and the magnitude of the current applied to drive coils 2a to 2c can be limited so as not to exceed a predetermined value. . FIG. 2 shows changes in the waveforms of the currents flowing through the drive coils 2a to 2C due to the above chopping operation.

After this chopping operation, the resistance 12.13
A voltage determined according to the voltage division ratio is output from the comparator 11, and this high-level chopper signal is input to the plus input terminal of the comparator 16 through a time constant circuit. At this time, due to the charge accumulation effect of the capacitor 13 of the time constant circuit, the time until the potential of the chopper signal reaches the reference voltage VS is delayed. That is, the rise of the chopper signal is delayed. Note that the comparator 16
The relationship between the high-level input chopper signal Vf input to the comparator 16 and the high-level output chopper signal Vout output from the comparator 16 is shown in FIG.

Therefore, due to the above-described delay, it is possible to secure a long time T from when the switching transistors 4a to 4c are turned off until they are turned on again. This delay time T is about 1 millisecond, and the rest time of the switching transistors 4a to 4c can be extended by about 1000 degrees compared to the conventional case where such a delay is not used. The influence of variations in each circuit component can also be completely eliminated.

Therefore, each transistor 48 to 4c can be sufficiently rested, and the switching transistor 4a
It is possible to completely prevent current from flowing through the drive coils 2a to 2c after the coils 2a to 4c are turned off. Note that the delay operation described above is performed not only when the motor is started, but also when the chopping operation is performed during steady operation of the motor.

In this way, regardless of the chopping operation of the constant current chopper circuit 8, the rise of the high-level chopper signal is delayed to prevent current from flowing through the drive coils 28 to 2c, so that the switching transistors 4a to 4C are turned off. It is possible to eliminate losses in these transistors 48 to 4C immediately after the operation. Therefore, in order to create a high-speed, high-input brushless motor, although a constant current chopper circuit is used, switching transistors 48 to 4C
There is no risk of burning out due to the heat generated.

3 and 4 show a second embodiment of the invention. In this embodiment, the constant current chopper circuit 8 is formed with a reference voltage variable means 21, the delay means of the above embodiment is omitted, and the output terminal of the comparator 11 is connected to the AND gates 6a to 6c. Connected directly to each input terminal. The configuration other than these points is the same as the first embodiment.

The reference voltage variable means 21 gradually increases the reference voltage vb to a set value over time when the motor is started, and as shown in FIG. Become. The interconnection point of resistors 12 and 13 that generate a constant voltage is connected to the end of the resistor 22 opposite to the interconnection point with the capacitor 23, and the interconnection point between the resistor 22 and the capacitor 23 is connected to a comparator. It is connected to the positive input terminal of 11.

According to this second embodiment, when the motor is started, the resistor 12.
A voltage determined according to the voltage division ratio of 13 is set to the positive input terminal of the comparator 11 via the reference voltage variable means 21. Therefore, due to the charge storage effect of the capacitor 23, the time required for the potential at the positive input terminal to reach the reference voltage vb is delayed, so the chopper current gradually increases from zero as time passes, as shown in FIG. It will eventually become the set value.

Since the chopper current is varied over time, each time the constant current chopper circuit 8 performs a chopping operation, even though current flows through the switching transistors 4a to 4C, the power supply voltage and current at the time of starting the motor are changed. Can be kept small. Therefore, the above formula P-(V-
It is clear from IR)×1 that the values of
By reducing the loss of ~4C, the motor can be started while preventing these burnouts.

In addition, in this second embodiment, since the starting of the motor is controlled by controlling the current rather than the power supply voltage as described above, only the processing of the signal system is required, and the reference voltage variable means 21 has a time constant. It can be easily realized by adopting a simple circuit such as a circuit.

However, when controlling with the power supply voltage like a soft start circuit, in addition to the power components such as the power supply and thyrisk, additional components are required to control them, making the structure complicated. Such problems can be avoided in this embodiment.

FIG. 5 shows a third embodiment of the invention. In this example,
The constant current chopper circuit 8 is formed by providing a reference voltage variable means 31 instead of the constant voltage generating circuit, and the delay means of the above embodiment is omitted, and the output terminal of the comparator 11 is connected to the AND gates 6a to 6C. are connected to the respective input terminals of the These unintended configurations are the same as in the first embodiment.

The reference voltage variable means 31 gradually increases the reference voltage vb to a set value as the rotation speed of the rotor 3 increases when the motor is started, and is formed of a rotation speed-voltage converter. The input end of this variable means 31 is connected to any input line of the drive signal to the AND gates 6a to 6C, and the output end is connected to the comparator 1.
It is connected to the positive input terminal of 1. Since the drive signal is generated by the position detecting means 5a to 5C as the rotor 3 rotates, a change in the period of the drive signal can be regarded as the number of rotations of the rotor 3. The rotation speed/voltage converter converts the rotation speed into a voltage corresponding to the rotation speed, and generates a small voltage when the rotation speed is low, and conversely generates a large voltage when the rotation speed is high.

Therefore, in this third embodiment, when the rotational speed of the rotor 3 is slow, a small voltage is set at the plus input terminal of the comparator 11 as the reference voltage vb, and as the rotational speed increases thereafter, the plus input terminal of the comparator 11 is set to a small voltage. , a gradually larger voltage is set as the reference voltage vb. Due to such an increase in the rotational speed, the Choppalumi flow also gradually increases from zero and eventually reaches the set value.

Since the chopper current is varied according to the rotational speed in this way, even though current flows through the switching transistors 4a to 4C each time the constant current chopper circuit 8 performs a chopping operation, the power supply voltage at the time of starting the motor is suppressed to a small value. can. Therefore, switching transistor 4
The above formula P-(V-IR)xI to find the loss P of a~4C
As is clear from the above, since the values of V and l are each small, the loss of the switching transistors 4a to 4c is naturally reduced, and the motor can be started while preventing the risk of burning out these transistors.

FIG. 6 shows a fourth embodiment of the invention. In this example,
The input end of the reference voltage variable means 31 consisting of the rotation speed/voltage converter in the configuration of the third embodiment is connected to a speed detection circuit 32 for detecting the rotation speed of the rotor 3. This unexpected configuration is the same as the third embodiment.

Therefore, even in the configuration of the second fourth embodiment, the third embodiment
For the same reason as in the embodiment, the loss of the switching transistors 4a to 4C is reduced, and the motor can be started while preventing the risk of burning out these transistors.

[Effects of the Invention Since the present invention is constructed as described above, it has the following effects.

In the control device for a brushless motor according to claim 1, the off time of the switching transistor after the chopping operation is ensured by the delay in the rise of the chopper signal, so that the loss of the switching transistor is eliminated and the chopping of the constant current chopper circuit is improved. Burnout of the switching transistor due to operation can be prevented.

In the control device for a brushless motor according to claim 2, since the chopper current is gradually increased over time when the motor is started, the loss of the switching transistor is reduced, and the loss of the switching transistor based on the chopping operation of the constant current chopper circuit is reduced. Can prevent burnout.

In the brushless motor control device according to claim 3, since the chopper current is gradually increased by increasing the rotational speed of the rotor when starting the motor, the loss of the switching transistor is reduced, and the switching based on the chopping operation of the constant current chopper circuit is reduced. Can prevent transistor burnout.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and FIG. 2 is a waveform diagram explaining the first embodiment. FIG. 3 is a circuit diagram showing a second embodiment of the present invention, and FIG. 4 is a waveform diagram explaining the second embodiment. FIG. 5 is a circuit diagram showing a third embodiment of the present invention. FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention. FIG. 7 is an explanatory waveform diagram showing a conventional example. 2a-2c... Drive coil, 3... Rotor, 4a-
4c...Switching transistor, 5a-5c...
・Position detection means, 6a to 6c...and gate, 8・
...constant current chopper circuit, 9...delay means, 21.3
1-...Reference voltage variable means. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (3)

[Claims] 1. switching transistors each connected in series to the drive coil; a position detection means for detecting the rotational position of the rotor rotated by the excitation of the drive coil; and a position detecting means connected downstream of the switching transistor to be detected on the downstream side. a constant current chopper that outputs a low-level chopper signal that turns off the transistor when the voltage exceeds a reference voltage, and outputs a high-level chopper signal that turns on the transistor when the detected voltage does not exceed the reference voltage; a circuit, a delay means connected to the output end of the chopper circuit to delay the rise of the high-level chopper signal for a certain period of time, and the output end connected to the base of the switching transistor, and the delay means connected to the input end. A control device for a brushless motor, comprising an AND gate connected to an output end of the position detecting means and an output end of the position detecting means, respectively, for turning on and off the switching transistor. 2. switching transistors each connected in series to the drive coil; a position detection means for detecting the rotational position of the rotor rotated by the excitation of the drive coil; and a position detecting means connected downstream of the switching transistor to be detected on the downstream side. outputs a low-level chopper signal that turns off the transistor when the voltage exceeds a reference voltage, and outputs a high-level chopper signal that turns on the transistor when the detected voltage does not exceed the reference voltage; a constant current chopper circuit having a reference voltage variable means for gradually increasing the reference voltage to a set value over time when the motor is started; and an output terminal connected to the base of the switching transistor, respectively;
A control device for a brushless motor, further comprising an AND gate connected to an input terminal of the output terminal of the constant current chopper circuit and the output terminal of the position detecting means, respectively, for turning on and off the switching transistor. 3. switching transistors each connected in series to the drive coil; a position detection means for detecting the rotational position of the rotor rotated by the excitation of the drive coil; and a position detecting means connected downstream of the switching transistor to be detected on the downstream side. outputting a low-level chopper signal that turns off the transistor when the voltage exceeds a reference voltage, and outputting a high-level chopper signal that turns on the transistor when the detected voltage does not exceed the reference voltage; a constant current chopper circuit having a reference voltage variable means for gradually increasing the reference voltage to a set value as the rotational speed of the rotor increases; A control device for a brushless motor, comprising an AND gate connected to an output end of a constant current chopper circuit and an output end of the position detecting means, respectively, for turning on and off the switching transistor.