JPH06169590A - Motor drive circuit - Google Patents

Abstract

PURPOSE:To prevent the saturation of an output transistor on control side without remarkably increasing the number of elements, which constitute a circuit, or setting the voltage for preventing the saturation, having a margin. CONSTITUTION:Transistors Q19, Q20, and Q21 are provided on the base side of output transistors Q1, Q3, and Q5 on saturation side. Saturation control voltage Valpha is applied through a diode Q22 to the bases of the transistors Q19, Q20, and Q21. The collectors of the transistors Q19, Q20, and Q20 are connected to the base of the transistor Q23. The transistor Q23 leads a current hfe times the current supplied to the base into the earth from the output of a current feedback amplifier 64. When the drive of the output transistors 1, Q3, and Q4 on control side increases and the output of the current feedback amplifier 64 increases accompanying it, the current being led in the earth by transistor Q23 increases, and the driving current being distributed to the output transistors Q1, Q3, and Q5 on control side from an above and below distributing circuit 60 decreases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit having a saturation prevention circuit.

[0002]

2. Description of the Related Art A spindle motor or the like of an optical disk system is required to have a low driving sound. In order to reduce the drive noise of the three-phase brushless motor, there are so-called 120 ° soft switching energization and 180 ° energization as a method of energizing the motor. Here, 120 ° means that the energization period in a half cycle is 120 ° in terms of electrical angle, and 180 ° means energization over the entire electrical angle of the motor.

FIG. 4 shows the configuration of a motor drive circuit according to a conventional example. The circuit shown in this figure is generally configured as an IC, and includes a position detection signal synthesizing unit 10, a voltage converting unit 12, three upper and lower differential distribution circuits 14, and an output circuit 16.

The position detection signal synthesizing section 10 receives a position detection signal from a sensor for detecting the rotational angle position of the motor,
These are combined and output to the voltage conversion unit 12. As the sensor for detecting the rotational angle position of the motor, a Hall element or the like arranged on the rotor at a predetermined angle can be used. The sensor including a Hall element or the like is connected to the input terminals IN1 to IN3 for each phase.

The position detection signal synthesizer 10 is composed of three differential circuits 18, 20 and 22. Differential circuit 1
8, 20, and 22 are input terminals IN1 to IN3, respectively.
It corresponds to. In addition, the position detection signal synthesizing unit 10 uses 3
The current mirror circuits 24, 26 and 28 are provided. One of the transistors forming the differential circuit 18 is an input side transistor of the current mirror circuit 24,
The other is connected to the input side transistor of the current mirror circuit 28, respectively. Similarly, one of the transistors forming the differential circuit 20 is connected to the input side transistor of the current mirror circuit 26, and the other is connected to the input side transistor of the current mirror circuit 24. Further, one of the transistors forming the differential circuit 22 is connected to the input side transistor of the current mirror circuit 28, and the other is connected to the input side transistor of the current mirror circuit 26. Current mirror circuit 2
Output currents to the voltage conversion unit 12 are taken out from the collectors of the output side transistors 4, 26 and 28. In the figure, 30, 32, 34, 36, 38 and 40 are
These are current sources for supplying a constant current to the output side transistors of the differential circuits 18, 20, 22 and the current mirror circuits 24, 26, 28, respectively, and their output currents are the same. VCC is a power supply terminal.

The voltage conversion unit 12 includes a position detection signal synthesis unit 1
0 output current is converted into voltage, and the upper and lower three differential distribution circuit 14
Supply to. The upper and lower three differential distribution circuit 14 includes the voltage conversion unit 1
The drive current is distributed to the output circuit 16 according to the output voltage of 2. The output circuit 16 includes output transistors Q1 to Q6 so as to correspond to the three output terminals OUT. Among these output transistors, the transistors Q1, Q3 and Q5 shown on the upper side in the figure are so-called source side output transistors, and Q2, Q4 and Q6 are sink side output transistors. Each output terminal OUT has an output transistor Q1 and Q2, and Q3 and Q, respectively.
4, a voltage is output from the connection point of Q5 and Q6. The output terminal OUT has coils 4 for each phase of the motor to be driven.
2, 44 and 46 are connected. Therefore, by appropriately controlling the supply of the drive current to the output transistors Q1 to Q6, it is possible to supply a desired current to the motor phase coils 42 to 46.

The upper and lower three differential distribution circuit 14 is a circuit for executing this drive power distribution. Upper and lower three differential distribution circuit 14
Are transistors Q7, Q9 and Q11 for distributing drive current to the source side output transistors Q1, Q3 and Q5.
In addition, the sink side output transistor Q2
Transistor Q for supplying drive current to Q4 and Q6
8, Q10 and Q12 are provided.

The collectors of the transistors Q7, Q9 and Q11 are transistors Q13, Q14 and Q1, respectively.
5 is connected to the base and collector. The transistors Q13, Q14 and Q15 are the input side transistors of the current mirror circuits 48, 50 and 52, and the output side transistors Q16, Q17 and Q18 of the current mirror circuits 48, 50 and 52 are the source side output transistors Q1 and Q3. And Q5 are inverted Darlington connection. Also, transistors Q8 and Q10
And the collectors of Q12 are current amplifiers 54, 56 and 5
Sink side output transistors Q2, Q4 and Q6 via
Connected to the base of. Therefore, the transistor Q
The drive currents of the source side output transistors Q1, Q3 and Q5 are determined by the output currents of Q7, Q9 and Q11, and the drive currents of the sink side output transistors Q2, Q4 and Q6 are determined by the output currents of transistors Q8, Q10 and Q12. It

The drive current is distributed to the output transistors Q1 to Q6 by the transistors Q7 to Q12 and the upper / lower distribution circuit 6.
Executed by 0. The upper / lower distribution circuit 60 supplies the output current of the built-in current source to the transistors Q7, Q9 and Q.
11 and on the other hand, to the transistors Q8, Q10 and Q12 via the current mirror circuit 62. When the voltage is supplied from the voltage conversion unit 12, the transistor Q
7, Q9 and Q11 distribute the current supplied from the current source of the upper / lower distribution circuit 60 to the output transistors Q1, Q3 and Q5 according to this voltage. Similarly, the transistors Q8, Q10, and Q12 supply the current supplied from the upper / lower distribution circuit 60 via the current mirror circuit 62 to the sink-side output transistors Q2, Q4, and Q6 according to the voltage supplied from the voltage conversion unit 12. Distribute as drive current.

The output current of the upper / lower distribution circuit 60 is feedback-controlled by the operating current of the motor. That is, the circuit of FIG. 4 includes the current feedback amplifier 64 that constitutes a current feedback loop. The current feedback amplifier 64 inputs the control input indicating the control target value of the operating current, inputs the voltage across the resistor Rf, and supplies the upper / lower distribution circuit 60 with a current corresponding to the difference. The resistor Rf is a sink side output transistor Q.
2, Q4 and Q6 are connected to the emitter side and convert the output currents of the output transistors Q1 to Q6 into voltage.
This output current represents the operating current of the motor. Therefore, one input of the current feedback amplifier 64 corresponds to the detected value of the operating current of the motor. Therefore, according to the output current of the current feedback amplifier, the upper / lower distribution circuit 60 causes the transistors Q7 ...
By supplying the current to Q12, the operating current of the motor by the output transistors Q1 to Q6 is controlled, and thus the driving force of the motor is controlled.

The circuit further includes a voltage feedback amplifier 66 to prevent saturation of the control side output transistor. In order to stabilize the output current from the output circuit 16 to the phase coils 42, 44 and 46 of the motor, for example, the method of feeding back the midpoint potential of the motor, the source side output transistors Q1, Q3 and Q5 and the sink side are used. There is a method of using any one of the output transistors Q2, Q4 and Q6 in a saturated state. Sink side output transistors Q2, Q4 and Q
6 is driven in the saturation state, and the source side output transistor Q
1, when Q3 and Q5 are used as the output transistors on the control side, the output circuit 16 causes the motor coil 42,
The maximum value of the output voltage to 44 and 46 is set to the diode group 68.
The voltage feedback amplifier 66 compares this with a reference voltage determined according to the motor drive power supply voltage. The output current of the voltage feedback amplifier 66 is supplied to the upper / lower distribution circuit 60, and the output current of the voltage feedback amplifier 66 is supplied from the upper / lower distribution circuit 60 to the transistor Q.
The output current to 7 to Q12 is changed. With such a circuit configuration, the control-side output transistor Q1,
It is possible to prevent saturation of Q3 and Q5.

For example, in the case of 120 ° soft switching energization shown in FIG. 5A, if the control input to the current feedback amplifier 64 is increased to increase the driving force of the motor,
The output current waveforms of the output transistors Q1 to Q6 change in the direction indicated by the arrow in the figure. In the circuit of FIG. 4, this change is detected by the voltage feedback amplifier 66, and the output current from the upper / lower distribution circuit 60 is suppressed. In this way, saturation of the control side output transistors Q1, Q3 and Q5 is prevented.

[0013]

However, in such a configuration, it is necessary to provide a single comparator (the voltage feedback amplifier 66 in the configuration of FIG. 4) to prevent saturation. This increases the number of elements that make up the circuit, which is an obstacle to cost reduction especially when the motor drive circuit is integrated into an IC.

Further, in such a configuration, it is necessary to set the saturation control voltage with a margin. The saturation control voltage is, for example, a reference voltage input to the voltage feedback amplifier 66 in the configuration of FIG. 4, and is normally set to a voltage slightly lower than the motor drive voltage (voltage applied to the terminal VM). Specifically, from the voltage applied to the terminal VM, the saturation voltage Vcesat of the transistors Q16, Q17 and Q18 is calculated.
And the base-emitter voltage threshold Vbe of the output transistors Q1, Q3 and Q5 on the control side are reduced, and further, the temperature change and variation of Vbe and the transistors Q16, Q17 and Q1.
Set in consideration of the margin of the saturation voltage Vcesat of 8. Since such setting has to be performed, in the past, there has been a problem in that heat generation increases due to a decrease in power utilization rate, resulting in a decrease in power efficiency and an increase in loss.

Further, in the case of 180 ° energization, as shown in FIG. 5B, the output current waveform changes in the direction of the arrow when the driving is strengthened. In the above-mentioned saturation prevention operation, the energization width to the motor is not controlled, and therefore, the saturation state is reached in the entire energization region, resulting in the output current waveform shown by the broken line in the figure. . This causes an increase in motor driving noise. In order to prevent this, it is necessary to provide two capacitors for rectifying and smoothing the upper side and the lower side of the output terminal voltage and feeding back the voltage of the capacitors as the saturation detection voltage. Since this capacitor has a large capacity, it is difficult to form it in an IC.

The present invention has been made to solve the above problems, and it is possible to prevent saturation of a control-side output transistor with a smaller number of circuit elements and to drive the control-side output transistor. It prevents fluctuation of the saturation voltage of the transistor that supplies the current, and
It is an object of the present invention to prevent the saturation of the control side output transistor without an external capacitor and to prevent the oversaturation of the saturation side output transistor even when energizing at 0 °.

[0017]

In order to achieve such an object, the present invention provides an NPN type source side output transistor having a collector connected to a power source side and driving a motor winding by an emitter, and a source side output transistor. A drive transistor that supplies current to the base of the transistor, a means for generating a negative reference voltage with the collector of the source-side output transistor as a reference, and this reference voltage is applied to the base and the emitter is connected to the base of the source-side output transistor. The saturation detection transistor, the means for detecting the operating current of the motor, the current feedback loop for comparing the detected operating current with the control input and controlling the current supplied to the drive transistor according to the comparison result, and the drive transistor Current feedback to reduce the supplied current according to the collector current of the saturation detection transistor Characterized in that it comprises a means for controlling the-loop.

Further, the present invention comprises an NPN type sink side output transistor whose collector is connected to the emitter of the source side output transistor and is driven in a saturated state, and the current feedback loop has a source side output transistor and a sink side output transistor. Means for detecting the minimum value of the connection point voltage of,
A means for comparing the detected minimum value with a saturation control voltage which is controlled slightly higher than the saturation voltage so as not to cause oversaturation of the sink side output transistor, and a current supplied to the drive transistor and a drive current of the sink side output transistor. And a means for distributing the output current of the current feedback loop according to the comparison result so that the ratio becomes sufficiently close to 1.

[0019]

In the present invention, the operating current of the motor is detected and the detected operating current is compared with the control input. The current feedback loop controls the current supplied to the drive transistor according to the comparison result. On the other hand, the base voltage of the NPN source side output transistor is compared with the reference voltage by the saturation detection transistor, and the current feedback loop is controlled according to the comparison result. That is, the current supplied to the NPN type source side output transistor decreases according to the collector current of the saturation detection transistor. This current reduction suppresses the increase in the base potential that accompanies the increase in the drive current of the source side output transistor. As a result, the saturation of the source-side output transistor is preferably prevented without significantly increasing the number of circuit elements or setting the voltage with a margin.

Further, in the present invention, current distribution to the output transistors on the source side and the sink side allows the use of an external capacitor or the like even in the case of 180 ° conduction having a driving force at all conduction electric angles. It is possible to suppress oversaturation of both the source side and sink side output transistors. First, when the source side output transistor approaches saturation and the base potential rises, the output current of the current feedback loop is reduced by the operation described above. The output current of the current feedback loop is distributed to the source side and the sink side by the distribution ratio that is determined so that the sink side does not oversaturate by comparing the minimum value of the connection point voltage between the source side output transistor and the sink side output transistor and the saturation control voltage. To be done. Therefore, oversaturation of both the source side output transistor and the sink side output transistor is less likely to occur. At that time, an external capacitor or the like for rectifying and smoothing the positive side and the negative side of the connection point voltage between the source side output transistor and the sink side output transistor is unnecessary.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. The same components as those in the conventional example shown in FIGS. 4 and 5 are designated by the same reference numerals, and the description thereof will be omitted.

First Embodiment FIG. 1 shows the configuration of the essential parts of a motor drive circuit according to the first embodiment of the present invention. In this embodiment, as the position detection signal synthesizing unit 10 and the voltage converting unit 12, the same configurations as those shown in FIG. 4 can be used. The configuration shown in this figure has three upper and lower differential distribution circuits 14 and an output circuit 16.
It is a peripheral structure.

This circuit has a source side output transistor Q.
1, Q3 and Q5 are control side output transistors, and sink side output transistors Q2, Q4 and Q6 are saturation side output transistors. Transistors Q16, Q17 and Q18 are respectively connected to the control side output transistors Q1, Q3 and Q5 by inverted Darlington connection, as in the configuration of FIG. In this embodiment, saturation detecting transistors Q19, Q20 and Q21 are provided on the base side of the control side output transistors Q1, Q3 and Q5. The saturation control voltage V is applied to the bases of the transistors Q19 to Q21 via the diode Q22.
α is applied as a reference voltage. A current source 70 supplies a current to the transistors Q19 to Q21.

Further, the collectors of the transistors Q19 to Q21 are connected to the base of the transistor Q23. The transistor Q23 is provided on the output side of the current feedback amplifier 64. The current feedback amplifier 64 is the amplifier 7
4 and the voltage across the resistor Rf are input, and a current corresponding to the difference is output. The amplifier 74 compares the control input indicating the control target value of the operating current with a predetermined voltage, and inputs the result to the current feedback amplifier 64. Current feedback amplifier 64
Output current of the current mirror circuit 78 is input to the current mirror circuit 78.
Is being supplied to. The upper / lower distribution circuit 60 distributes the current supplied from the current mirror circuit 78 to the source side and the sink side.

In this embodiment, when the control input increases and the output current of the current feedback amplifier 64 increases as a result, the value of the drive current distributed to the source side and the sink side by the upper / lower distribution circuit 60 increases. As a result of this increase, for example, the control-side output transistor approaches saturation and the transistor Q1
When the base potential of the transistor Q1 rises, a current flows through the transistor Q19 connected to the base of the transistor Q1.
This current is supplied to the base of the transistor Q23. Then, the transistor Q23 becomes the transistor Q19.
From the output of the current feedback amplifier 64 to ground. Therefore, the current feedback amplifier 64
The current value supplied to the upper / lower distribution circuit 60 via the current mirror circuit 68 is reduced. As a result, the increase in the drive current of the output side transistors Q1 to Q6 is suppressed. That is, the control side output transistors Q1 and Q3
And the rise of the base potential of Q5 will be limited,
Saturation of the control side output transistors Q1, Q3 and Q5 is prevented.

Further, control side output transistors Q1 and Q3
When the increase of the base potential of Q5 and Q5 is limited, the variation of Vbe of the transistors Q1, Q3 and Q5 does not contribute to the saturation prevention. Therefore, it is not necessary to set the control voltage Vα to a value that allows for the Vbe fluctuations of these transistors Q1, Q3, and Q5. As a result, the power utilization rate is improved and the drive efficiency of the motor is increased. Furthermore, loss is suppressed and heat generation is suppressed.

Furthermore, in this embodiment, only the capacitor C1 provided on the output side of the current mirror circuit 78 may be used as an element for preventing oscillation. That is, since the circuit of the present embodiment is configured to adjust the output current of the current feedback amplifier 64 that constitutes the current feedback loop,
The oscillation of the feedback loop composed of the transistors Q19 to Q23 is controlled by the current feedback loop oscillation prevention capacitor C1.
Can be realized only by.

Second Embodiment FIG. 2 shows the configuration of a motor drive circuit according to the second embodiment of the present invention. Similar to FIG. 1, this drawing shows the configuration around the upper and lower three differential distribution circuits 14 and the output circuit 16.

In this embodiment, the transistor Q19
A current mirror circuit 80 is provided on the collector side of Q21. The output currents of the transistors Q19 to Q21 are input to the current mirror circuit 80. The output of the current mirror circuit 80 is supplied to the transistor Q24. Transistor Q24 is biased by current source 82 and resistor R1 and has transistors Q19-Q21.
Is maintained at a constant voltage by the transistor Q24.
Therefore, in this embodiment, the transistors Q19-
Since Q21 and Q24 operate at substantially the same current density, the base potentials of the control side output transistors Q1, Q3 and Q5 do not depend on the gain of the amplifier 74 and the like.
The current source 83 is a starting circuit that supplies a minute current to the transistor Q25.

Third Embodiment FIG. 3 shows the configuration of the essential parts of a motor drive circuit according to a third embodiment of the present invention. The circuit shown in this figure is particularly the internal configuration of the upper / lower distribution circuit 60.

The upper / lower distribution circuit 60 has a differential circuit 84 having transistors Q26 and Q27 as input transistors. The base of the transistor Q26 is connected to the output terminal OUT via the diode group 86. The voltage applied from the diode group 86 to the base of the transistor Q26 has the lowest voltage value among the voltages appearing at the three output terminals OUT. A voltage that is variably controlled according to the voltage across the resistor Rf is applied to the base of the transistor Q27. That is, this differential circuit 8
Reference numeral 4 has a function of comparing the minimum value of the output voltage of the output circuit 16 with the output current of the output circuit 16.

Each input transistor Q26 of the differential circuit 84
Current mirror circuits 88 and 90 are provided on the collector side of Q27 and Q27, respectively. The current mirror circuits 88 and 90 are supplied with current from the transistors Q26 and Q27, respectively. Current mirror circuit 8
Reference numeral 8 denotes transistors Q7, Q9 and Q1 related to driving current distribution to the source side output transistors Q1, Q3 and Q5.
The current mirror circuit 90 supplies a current to the transistors Q8, Q10 and Q12 relating to the current distribution to the sink side output transistors Q2, Q4 and Q6 via the current mirror circuit 62. In the figure, 92
The circuit indicated by is a current mirror circuit that supplies a current to the differential circuit 84 and a bias current to the current mirror circuits 88 and 90. The input of this current mirror circuit 92 is the output current of the current mirror circuit 78.

With such a circuit configuration, it is possible to limit the ratio between the drive currents of the saturation side output transistors Q2, Q4 and Q6 and the drive currents of the control side output transistors Q1, Q3 and Q5. That is, the saturation side output transistors Q2, Q4 and Q6 and the control side output transistor Q
It is possible to distribute the drive currents to 1, Q3 and Q5 while preventing oversaturation so that the output currents of these output transistors Q1 to Q6 are not distorted. More specifically, as the base potentials of the control-side output transistors Q1, Q3, and Q5 rise, the current supplied to the upper / lower distribution circuit 60 is reduced, and the current is further controlled by the differential circuit 84 to the control side and the saturation side. Is over-saturated, the control side output transistors Q1, Q3 and Q5 and the saturation side output transistors Q2, Q4 and Q6 are prevented from being oversaturated. As a result,
There is no need to use external parts such as capacitors.

If the present invention is applied to the control circuit for the brushed motor, the output transistor can be driven without being saturated, and therefore the power consumption of the output transistor can be reduced.

[0035]

As described above, according to the present invention,
The saturation detection transistor compares the base voltage of the source side output transistor with the reference voltage, and the current supplied to the source side output transistor is reduced by the collector current of the saturation side detection transistor. Is limited, and its saturation can be preferably prevented. At that time, since it is not necessary to use a comparator or the like, an increase in the number of circuit elements can be prevented. Further, since it is not necessary to reflect the variation of Vbe of the driving transistor in the setting of the voltage used for preventing saturation, it is possible to improve the power supply utilization rate and suppress the loss.

Further, according to the present invention, the distribution ratio determined so that the sink side will not be oversaturated by comparing the minimum value of the connection point voltage of the source side output transistor and the sink side output transistor with the saturation control voltage causes the current feedback loop Since the output current is distributed to the source side and the sink side,
In the 120 ° / 180 ° dual conduction system, oversaturation of both the source side output transistor and the sink side output transistor can be suitably suppressed without an external capacitor.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main configuration of a motor drive circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a main configuration of a motor drive circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a main configuration of a motor drive circuit according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a motor drive circuit according to a conventional example.

FIG. 5 is a diagram showing a change in output current waveform when driving is strengthened, and FIG. 5 (a) shows the case of 120 ° energization.
(B) is a figure which respectively shows the case of 180 degree trapezoidal wave energization.

[Explanation of symbols]

10 position detection signal synthesis section 12 voltage conversion section 14 upper and lower three differential distribution circuit 16 output circuit 42, 44, 46 motor coil 64 current feedback amplifier 74 amplifier 80 current mirror circuit Q1, Q3, Q5 source side output transistor Q2, Q4 , Q6 Sink side output transistor Q7, Q9, Q11 Transistor for current drive current distribution to source side output transistor Q8, Q10, Q12 Transistor for current drive current distribution to sink side output transistor Q16, Q17, Q18 Control side output Transistors for supplying drive current to transistors Q19, Q20, Q21 Transistors for fixing the base potential of the control side output transistors Q23 Transistors for pulling in the output of the current feedback amplifier

Front page continuation (72) Inventor Yutaka Kamoki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. An NPN type source side output transistor whose collector is connected to a power source side to drive a motor winding by an emitter, a drive transistor which supplies current to the base of the source side output transistor, and a collector of the source side output transistor. Means for generating a negative reference voltage, a saturation detection transistor in which this reference voltage is applied to the base and the emitter is connected to the base of the source side output transistor, a means for detecting the motor operating current, and a detection The current feedback loop that controls the current supplied to the drive transistor by comparing the generated operating current with the control input according to the comparison result, and the current feedback that reduces the current supplied to the drive transistor according to the collector current of the saturation detection transistor. A motor drive circuit comprising means for controlling a loop. Road. 2. An NPN-type sink-side output transistor, whose collector is connected to the emitter of the source-side output transistor and is driven in a saturated state, wherein the current feedback loop has a connection point voltage between the source-side output transistor and the sink-side output transistor. Means for detecting the minimum value of, and a means for comparing the detected minimum value with a saturation control voltage which is controlled slightly higher than the saturation voltage so as not to cause oversaturation of the output transistor on the sink side, and a current supplied to the drive transistor. 3. The motor drive circuit according to claim 1, further comprising means for distributing the output current of the current feedback loop according to the comparison result so that the ratio of the drive current of the sink side output transistor is close to 1 sufficiently.