JP2556143B2 - Integrated circuit device for driving a motor - Google Patents

Description

The present invention relates to an integrated circuit device used in a drive circuit that controls the speed of a motor.

[Prior Art] Conventionally, there is a motor drive circuit having a configuration shown in FIG. 3 as a motor drive circuit that performs feedback control even when the load of the motor fluctuates so that the rotation speed of the motor becomes constant. In the figure, M is a three-phase brushless motor, Q1 to Q6 are six power transistors for driving the brushless motor M, IN1 is a power supply terminal for supplying DC power to a drive circuit including the power transistors Q1 to Q6, and IN2. Is a reference signal terminal for applying a predetermined reference voltage Vref, and IN3 is a control signal terminal for inputting a speed control signal Vctl (servo signal) according to the rotation speed of the brushless motor M which changes with load variation. A1 is a first for outputting a base current control signal of the power transistors Q1 to Q6 according to a signal deviation ΔV between the reference voltage Vref and the speed control signal Vctl (that is, ΔV = Vctl−Vref).
, A2 is a second differential amplifier connected to the reference signal terminal IN2, and A3 is a third differential amplifier connected to the control signal terminal IN3. Q9 and Q10 are both transistors whose bases are connected to the third differential amplifier A3, R1 and R2 are voltage dividing resistors, and Rs is a sensing resistor.

In such a configuration, the rotation control signal applied to the third differential amplifier A3 according to the rotation speed of the brushless motor M.
The magnitude of Vctl is the reference voltage applied to the second differential amplifier A2.
When Vref is exceeded, the reference voltage Vref and speed control signal
A signal deviation ΔV of Vctl is generated across the resistor R2,
At the same time, the signal deviation ΔV is shifted across the resistor R1. The first differential amplifier A1 outputs the base current control signals of the power transistors Q1 to Q6 so that a voltage drop of the same magnitude as the signal deviation ΔV occurs across the sensing resistor Rs. With this configuration, even if the load of the brushless motor M changes, the base current Ictl of each of the power transistors Q1 to Q6 is controlled so that its rotation speed becomes constant.

As is well known, each arm connected to the coil drive terminals U, V, W of this three-phase brushless motor is shown in FIG. 5 by a position signal from a position detection element such as a photo interrupter (not shown). As shown in the drawing, the brushless motor M is switched and driven at every 120 °.

[Problems to be Solved by the Invention] By the way, in the motor drive circuit having such a configuration, according to the signal deviation ΔV between the reference voltage Vref and the speed control signal Vctl input to the reference signal terminal IN2 and the control signal terminal IN3, respectively. The second and third differential amplifiers A2 and A3 and the transistors Q9 and Q10 are provided in order to apply the signal to the first differential amplifier A1. Therefore, the motor drive circuit is composed of many elements, and there are various difficulties in realizing the motor drive circuit as an integrated circuit device.

Conventionally, when this motor drive circuit is realized as an integrated circuit device, the power transistors Q1 to Q6 and the second and third differential amplifiers A2 and A3 have a pattern layout configuration as shown in FIG. It was In this case, paying attention to the range of 0 ° to 120 ° in the rotation angle of the motor, Q2 is continuously conducting in the entire range, but in the range of 0 ° to 60 °, Q3 is 60 ° to 120 °.
In the range of °, Q5 is conducting, and the power transistor conducting in the middle switches from Q5 to Q3. Here, as viewed from the third differential amplifier A3, the distances of Q5 and Q3 from the power transistors are different from each other, so that the interval of 0 ° to 60 ° in which Q5 is conductive and the interval of 60 ° in which Q3 is conductive. ~
The thermal influence on the third differential amplifier A3 is different in the section of 120 °. Due to the fluctuation of the thermal effect, the output of the third differential amplifier A3 also changes, and similarly, the output of the first differential amplifier A1 also has the thermal effect, so that a ripple component appears in the output and the power is increased. Transistor Q1 to Q6 base current Ic
tl fluctuates, causing problems such as deterioration of motor control characteristics. This phenomenon is caused by the second and third differential amplifier A3
Besides, the same occurs for the transistors Q9 and Q10.

In order to avoid such a change in thermal influence, the second and third differential amplifiers A2 and A3 and the transistors Q9 and Q10 that form the servo control system should be arranged as far as possible from the power transistors Q1 to Q6. You can, but as mentioned above,
This conventional drive circuit has a large number of elements,
If the layout configuration is such that the distance between the respective elements is secured, the chip area becomes large and it becomes more difficult to realize it as an integrated circuit.

[Means for Solving the Problems] The present invention has been made in view of the above circumstances, and reduces the number of elements in the circuit configuration as compared with the related art without impairing the required characteristics. , It is intended to minimize fluctuations in heat effect.

Therefore, in the present invention, between the power supply terminal and the negative-phase terminal of the differential amplifier via the first transistor and the resistor,
The power supply terminal and the positive-phase terminal of the differential amplifier are connected to the second transistor via a resistor, respectively, and the negative-phase terminal of the differential amplifier is connected to the sensing resistor via the resistance, , And a control signal terminal was connected to the base of the second transistor, and six power transistors, a differential amplifier, a first transistor and a second transistor were formed on one chip.

[Operation] In the drive circuit having this configuration, since the current control system is configured by the two transistors and the one differential amplifier, the number of circuit elements is smaller than in the conventional case. In addition, since the margin on the chip area increases as the number of circuit elements decreases, it becomes possible to arrange each circuit element forming the servo control system away from each power transistor. It is possible to minimize fluctuations in heat effect.

[Embodiment] FIG. 1 is a circuit configuration diagram of a motor drive circuit according to the present invention, and portions corresponding to the conventional example shown in FIG. 3 are denoted by the same reference numerals.

In FIG. 1, M is a three-phase brushless motor, Q1 to
Q6 is six power transistors for driving the brushless motor M, IN1 is a power supply terminal for supplying DC power to the drive circuit including the power transistors Q1 to Q6, IN2 is a reference signal terminal for applying a predetermined reference voltage Vref, and IN3 is It is a control signal terminal for inputting a speed control signal Vctl (servo signal) according to the rotation speed of the brushless motor M which changes with load variation. A1 is a differential amplifier that outputs the base current control signal of the power transistors Q1 to Q6 according to the signal deviation ΔV between the reference voltage Vref and the speed control signal Vctl, and Rs is a sensing resistor. These configurations are shown in FIG. It is similar to the conventional motor drive circuit.

Further, in the motor drive circuit according to the present invention, the power supply input terminal IN1 and the negative phase input terminal (-) of the differential amplifier A1 are connected via the first transistor Q7 and the voltage dividing resistor R3, and the power supply terminal. Positive phase input terminal (+) of IN1 and differential amplifier A1
Is connected via a second transistor Q8 and a voltage dividing resistor R5, and the connection point a between the resistor R3 and the negative phase input terminal (−) of the differential amplifier A1 is a voltage dividing resistor R4. Is connected to the sensing resistor Rs via the voltage dividing resistor R5, and the connection point b between the voltage dividing resistor R5 and the positive phase input terminal (+) of the differential amplifier is a voltage dividing resistor R6.
Grounded through. On the other hand, the first transistor Q7
The reference signal terminal IN2 is connected to the base of the second transistor Q8
The control signal terminals IN3 are respectively connected to the bases of.

In such a configuration, when the torque command value to the brushless motor M decreases and the control signal Vctl becomes smaller than the reference signal Vref (Vctl ≦ Vref), the potential at the connection point a of the voltage dividing resistors R3 and R4 changes. It becomes higher than the potential of the connection point b of R5 and R6, and the output of the differential amplifier A1 causes the power transistor
The base current of Q1 to Q6 decreases, and the output current of each power transistor Q1 to Q6 and the brushless motor M
Drive torque decreases, and the rotation speed of the brushless motor M also decreases. The resistance values of the voltage dividing resistors R3 and R4 are sufficiently larger than the resistance value of the sensing resistor Rs.
3. The voltage flowing across the sensing resistor Rs is not affected by the current flowing through R4.

On the other hand, the torque command value to the brushless motor M increases and the control signal Vctl becomes larger than the reference signal Vref (Vctl> Vre
f), the potential at the connection point a of the voltage dividing resistors R3 and R4 becomes lower than the potential at the connection point b of the voltage dividing resistors R5 and R6, and the output of the differential amplifier A1 causes the base currents of the power transistors Q1 to Q6. Has increased, and along with that, each power transistor Q1
The output current of Q6 and the drive torque of the brushless motor M increase, and the rotation speed of the brushless motor M also increases.

The voltage across the sensing resistor Rs is the signal deviation ΔV
Changes by the amount equivalent to.

Even if the first and second transistors Q7 and Q8 are affected by the fluctuation of the heat distribution due to the conduction / interruption of the power transistors Q1 to Q6, this fluctuation is attenuated by the voltage dividing resistors R3 to R6 and is Be transmitted to. Regarding the influence of the variation of the heat distribution on the differential amplifier A1 itself, since the circuit of the present invention has a small number of elements as a whole and there is a margin in the chip area, as shown in FIG. The position can be sufficiently separated from each of the power transistors Q1 to Q6 so that the arrangement is less likely to be affected by the fluctuation of the heat distribution. Further, if the differential amplifier A1 is composed of four transistors, and each transistor is arranged in a "T" shape, the diagonal transistors form a pair. It is preferable because it is more unlikely to be affected by changes in heat distribution.

Although the resistor Rs is provided on the ground side in the above embodiment, the resistor Rs may be connected to the Vcc side by making the first and second transistors Q7 and Q8 PNP type. it can. Further, it goes without saying that the present invention can be applied to a drive circuit using a two-phase brushless motor.

[Effects of the Invention] According to the present invention, the number of elements in the circuit configuration can be reduced as compared with the prior art without impairing the required characteristics when driving a motor, and thus the chip area can be reduced, and therefore the integrated circuit device Can be easily realized. Moreover, an excellent effect is exhibited in that the influence of the fluctuation of the heat distribution can be reduced as much as possible.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a circuit configuration diagram of a motor drive circuit, and FIG. 2 is a pattern layout diagram of each element when the circuit is used as an integrated circuit device. . 3 and 4 show a conventional example, FIG. 3 is a circuit configuration diagram of a motor drive circuit, and FIG. 4 is a pattern layout diagram of each element when the circuit is used as an integrated circuit device. FIG. 5 is a timing chart of a three-phase brushless motor. Q1 to Q6 power transistors, IN1 …… power supply terminal, IN2 ……
Reference signal terminal, IN3 ... control signal terminal, A1 ... differential amplifier, Rs ... sensing resistance, Q7 ... first transistor, Q8 ... second transistor, R3 to R6 ... voltage dividing resistance.

Claims (1)

(57) [Claims] 1. A plurality of power transistors for driving a motor, a power supply terminal for supplying DC power to the plurality of power transistors, a reference signal terminal for inputting a predetermined reference signal, and a speed control signal for the motor. A differential amplifier that outputs a current control signal of the power transistor according to a difference between the reference signal and the speed control signal, and a sensing resistor that detects a motor current flowing through the plurality of power transistors. In a motor drive integrated circuit device for use in a motor drive circuit including: a first power supply terminal and a negative phase terminal of the differential amplifier;
Of the differential amplifier and the power supply terminal and the positive-phase terminal of the differential amplifier are connected via a resistor and the negative-phase terminal of the differential amplifier, respectively. To the sensing resistor, the reference signal terminal is connected to the base of the first transistor, and the control signal terminal is connected to the base of the second transistor. An integrated circuit device for driving a motor, wherein an amplifier, the first transistor and the second transistor are formed on one chip.