JPS5836188A - Brushless motor drive circuit - Google Patents

Abstract

PURPOSE:To form a drive circuit a brushless motor drive circuit which can suppress the offset voltage to small value capable of being ignored by providing a low pass filter in a feedback circuit of a DC amplifier system for amplifying the output of a rotor rotating position detecting magnetoelectric transducer. CONSTITUTION:A rotating position detection signal of a rotor from a Hall element 1 is amplified through an operational amplifier 3 and a single-ended push- pull power amplifier 5, and is applied to an exciting coil 7 of a brushless motor. A low pass filter 12 is provided in the feedback circuit of a DC amplifier system 10 which has the amplifiers 3, 5, and the relation of R2+R3=R5 is set to suppress the offset current of the amplifier 3 to low value. Since the feedback amount is reduced as the rotating speed of the rotor is increased due to the provision of the low pass filter 12, the gain of the system 10 increases proportionally to the rotating speed, and the offset voltage can be suppressed by the automatic removing function of the circuit itself by selecting the value of R5/R1 to small value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a brushless motor in which the output of a magnetoelectric transducer that detects the rotational position of a rotor is amplified by a DC amplification system equipped with an operational amplification device and applied to an excitation coil. This invention relates to a motor drive circuit.

The field magnet on the rotor side is magnetized in a sine wave, and two-phase excitation coils are arranged on the stator at intervals of odd multiples of 90 degrees in electrical angle.
2) A two-phase sinusoidal wave-driven brushless motor is known in which a drive current of the same phase as 0) is applied and a constant rotational torque is maintained by using the relationship am''#-)2θ=1.

Diagram 1 shows the drive circuit of this type of conventional two-phase sine wave drive brushless motor, which includes two Hall elements (1
1+21 is used as a rotor rotational position detection element. Although not shown, the Hall element (11(2)
O is placed in the same phase as each excitation coil or at a position that is an integral multiple of 180° in electrical angle. The output voltage is (31 (the output of 41 is the complementary connected transistor Trt%Tr
It is applied to the human-phase and B-phase excitation coils +71 and +81 through the single-end bush-pull (8EPP) power amplifiers (51+61), which consist of y and Tr, respectively. coil +71
+81 is directly connected to the DC amplification system number because the Hall cumulative Tf (11 (21
Amplify the direct i output of tIt% directly to the coil +71181
This is because the flow needs to flow. In addition, power amplifier f51
(The resistor R, which is connected between the output terminal of 61 and the inverting terminal of the operational amplifier t31+41, is a feedback resistor that determines the gain of this DC amplification system. (The output from 2+ is applied to the operational amplifier (31+41) and the power amplifier (51 (61) and is amplified by the human phase and B phase excitation coils +71 +8), respectively.

In addition, in such a motor drive circuit, as is well known, a Hall element (II(2+) and an operational amplifier f31 +41
There is an offset voltage (unbalanced voltage) for each. In principle, a two-phase sine wave driven brushless motor rotates smoothly without uneven rotation (torque ripple), but if there is even a slight DC component on the coil drive power supply side due to the offset voltage mentioned above, uneven rotation may occur. This causes noise and vibration of the motor shaft.

Furthermore, when the motor stops rotating, a wasteful current (offset amount) flows through the excitation coil, resulting in a problem of increased power loss. Therefore, in general, this type of motor drive circuit is provided with an offset compensation means. Means are provided. That is, the volume vR1,V
By adjusting B1, the operational amplifier +31+41
A predetermined DC voltage is applied to the non-inverting input terminal of the DC amplifier to cancel the offset voltage of the DC amplification system consisting of the Hall element (11 (2+), the operational amplifier 131 (41), and the power amplifier f51 +61. .

To compensate for the offset voltage, the excitation coil (7118
) Adjust the volumes VRI and VB2 so that the offset voltage becomes zero when the applied voltage Eo is a constant voltage (for example, before the rated rotation).

This cancels the offset voltage of the entire DC amplification system including the offset voltages of the Hall element (II(2+) and the operational amplifiers (3) and (4).

However, such conventional methods have the following drawbacks.

(11. Since the main cause of offset voltage is semiconductor elements such as transistors, the offset voltage fluctuates depending on the temperature. Therefore, the volume VR+, VB
Even if the offset voltage is adjusted to zero under the temperature conditions resulting from the adjustment of 2, the offset voltage will continue to occur as the temperature changes.

When offset voltage β occurs, exciting coils (7) (8
) changes from the adjusted state shown by the solid line in Fig. 2 to asymmetrical (α + μ α - β) as shown by the dotted line in Fig. 2, which becomes a major cause of rotational unevenness and noise. Wah and black are noticeable in devices.

(21. Due to aging, the adjustment points of the volumes VR, VB2 change, and this causes an offset voltage, which is a problem in the configuration.Also, as mentioned above, the so-called volume (variable resistance) - adjustment method Now, unless the volumes V1 and V2 are adjusted accurately, an offset voltage will inevitably occur.

(3), Hall element (IH21 and operational amplifier 13+
+41 offset gains are different, so when changing the voltage applied to the excitation coils (7) and (8) (for example, when changing the rotational speed of the motor shaft), an offset voltage will occur, and the Hall This causes problems such as the operating current of the element (11(2+) changing or the gain (or feedback amount) of the operational amplifier !31(41) changing.

(4) Hall element (lH2) to stop the motor
When the + operating current (or +Vcc) is reduced to zero, the offset of the Hall element (IH2+) disappears and the operational amplifier 13
The offset of 1 +41 is directly applied to the I coil 171 +
Added to 81. For this reason, the motor does not stop smoothly, but instead decelerates and stops in a so-called cogging state. Even under the stopped state, a DC current corresponding to the offset is flowing through the coil 17118), so there is power loss.

The present invention was invented in order to solve the various IS problems mentioned above, and it is possible to ignore the offset voltage (residual trade direct decrement) without being affected by temperature changes or secular changes. The present invention provides a brushless motor drive circuit configured to be small.

Hereinafter, examples of the present invention will be described with reference to Figures 1pJ3 to WI7. In addition, in Figures 3 to 7, Building 1
Parts common to those in the figures are given the same reference numerals. Although only the human phase (coil (7)) drive circuit is shown in these figures, the B phase (coil (8)) is also driven by a similar drive circuit.

FIG. 3 shows a first embodiment of the present invention. 6th
As shown in the figure, a DC amplification system G (l
A negative feedback circuit consisting of a resistor and a series resistor is provided between the output terminal 1 of the amplifier (3) and the inverting input terminal of the operational amplifier (3), and a low-pass filter 0 is provided in this negative feedback circuit. There is. That is, the connection point C between the feedback resistor island and the resistor is grounded via the resistor and capacitor 0. Therefore, the feedback resistor is 4, the resistor is 0, and the capacitor is 0. The low-pass filter 2 is llll1i. Further, the resistor bird is a dividing resistor for dividing the input signal supplied to the non-inverting input terminal of the operational amplifier 1 by the resistor Rt&.

In this embodiment, in order to suppress the offset of the operational amplifier (31) to a small value, R
i, the collector of Tr2 has a bidirectional electric current, that is, +Vcc.
.

-Vc and c are respectively supplied.

In the motor drive circuit configured in this way, when the input voltage e1 is supplied from the Hall element (11 to the operational amplifier (3)), the output terminal A of the DC amplification system 0 (1) has the following equation: An output voltage e.

However, Ei is the offset voltage included in the input signal number, ■
lo is the offset voltage of the operational amplifier (3), ■! o is the offset l-%1m of the apex amplifier (3).

Since the offset voltage fiIto is a very small value compared to the offset 'storm pressure Ei and VIO, the value of (■) above can be kept small, and as a result, the offset included in the output voltage eo can be ignored. It can be reduced.

In addition, as mentioned above, by providing the DC amplification system OI feedback circuit 1 and low-pass filter α2, the DC amplification system OI responds to changes in the rotational speed of the rotor (and in turn, the frequency of the output signal of the Hall element/element (1)). The gain of the widening system 00 changes. That is, as the rotational speed of the rotor increases Q) gain increases. Figure 4 shows the frequency f of the output signal of the Hall element (11) and the DC amplification system αO.
(1) As the frequency &if increases, the degree of increase increases exponentially.

The frequency f at startup is: Also, the frequency f when the motor reaches its rated rotation state.

teeth, , and the degree of increase A in that case is It is.

Note that normally, the normal operating frequency f of the motor is set higher than the frequency f.

According to the motor drive circuit configured as described above, instead of canceling the offset voltage by setting the volumes VILI and Vft2 to IIIi as in the conventional case, by reducing the value of b, the circuit itself automatically cancels the offset voltage.
) and the offset voltage of the motor drive circuit can be kept to a small level with the wealth cancel (automatic removal) function. Therefore, the occurrence of offset voltage (temperature drift) due to temperature changes, aging, etc. can be suppressed to a minimum. In this case, as described above, as the rotational speed of the rotor increases due to the provision of the low-pass filter az, the DC amplification system ae
Even if the degree of amplification is made small to reduce the offset voltage, sufficient output voltage can be supplied to the coil (31(4)) at the rated rotation.Also, compared to the conventional case, the offset voltage Since there is no need to perform any adjustment operation for the removal of the offset voltage, offset voltages are not likely to occur due to adjustment inaccuracies.

In addition, since the width increase I is configured to increase in accordance with the rotational speed l of the rotor, when an external force (load) is applied to the rotor and the rotation of the rotor decreases (or stops), the DC width increase system 001 The gain of will decrease. Therefore, since the current flowing through the coil t17+ (21) decreases, the power consumption at this time is reduced, and the coil 1.7+
Heat generation of 1 tl can be effectively suppressed.

In the past, even when the rotational speed of the rotor was reduced (or stopped) by an external force, the 11 current at the rated rotation was flowing through the coil, which caused the motor to generate heat. In some cases, there was a risk that the motor would be covered with burnt sand.

Figure tlc5 shows a second embodiment of the present invention.

As shown in FIG. 5, a single power supply of +Vcc is supplied to the collector of the transistor Tr1 of the power amplifier (5).
The collector of the other transistor Tr2 is grounded. In this embodiment, an operational amplifier (inverting amplifier) Q41, a pair of transistors 'r, 5. 'rr
A DC amplification system block consisting of a single-end bush-pull power amplification device (151) with complementary connection of 6 and 151 and having an intensification degree of -1 is provided.

Note that the collector of the above-mentioned transistor Tr5 is connected to the single voltage source Vcc, and the collector of the other transistor 'I'r6 is grounded. And DC widening thread (5) Q6
A coil (7) is connected between output terminals a and d of 1,
BTL (Ba,
J ancedTransforrrerless)
The circuit is configured.

A pair of resistors is connected in series between the output terminals 3 and d, and a resistor R7 is connected to the connection point g of the pair of resistors R6 to the inverting input terminal of the operational amplifier (14+).
The potential at the connection point between , and Ra is determined by the Zener die 4 and the ode D. A resistor R1 is connected between the connecting point C and the non-inverting input terminal of the operational amplifier (31), and the above-mentioned resistor and capacitor R1 are connected between the connecting points C and h. A series circuit 6 consisting of the following is connected.

In this example, R, -+4. =R,, ↑R6
=R8.

Describing the operation of the motor drive circuit configured, when the positive half wave of the sinusoidal rotor position detection signal is output from the operational term rD unit (3), the transistors Tr1 and Tr6 Each works as a sine V-shaped positive half-drive! 111'wL current flows to the coil (7) 〇Also, the negative half wave of the rotor position ti11 detector is connected to the operational amplifier (
3), the transistors Tr2 and T
, 5 are operated so that a negative half-wave drive current flows through the coil (7).

Also in this case, the feedback circuit of the DC amplification system Ql has a resistor R.
Since a low-pass filter a2 consisting of V, Rm, R4 and capacitor C1 is provided, as the rotational speed of the motor increases, the feedback current from output terminal a passes through resistor island A2, capacitor C1, and Zener diode D1, respectively. Passed through. Therefore, the relationship between one frequency & (corresponding to the rotational speed of the rotor) and the degree of amplification has a characteristic as shown in FIG. 6, just as in the case of the first embodiment described above.

In this case, the output voltage elo generated between output terminals a and d is expressed by the following equation.

-2Vx0t+2FL@I summer o+ +Re■xo2 -
・−・−・−−−−<g, where the base is the offset voltage included in the input signal, VI (IN is the operational amplifier (3)
, VIO2 is the offset voltage of the operational amplifier α4, ll0I is the offset current of the operational amplifier +31, and IIQ2 is the off-state of the operational amplifier 0.11.It can be kept small and the output amplitude can be kept large. be able to.

Therefore, in the case of this embodiment, it is possible to drive the iron circuit with only a single power supply of 1 Vcc, and it is also possible to obtain the same effects as in the case of the first embodiment described above.

FIG. 6 shows a third embodiment of the present invention. In this embodiment, switch low S1 and resistance R9 is provided. First mentioned above
As described in the second embodiment, since the offset voltage is increased during evening startup in order to keep the offset voltage low, it may not be possible to obtain sufficient starting torque.

Therefore, in this embodiment, as shown in FIG. 6, in the motor drive circuit of FIG. 5, a switch circuit S1 and a resistor R? (R9>R- is connected in series.

Therefore, when the motor is started, the switch circuit S is set to a predetermined F by a switching means (not shown) consisting of a control circuit, etc.
It is switched on only during I#, thereby reducing the feedback to the inverting input terminal of the operational amplifier (31).As a result, the gain of the DC amplifier system 0α becomes Since a relatively large current is passed through the coil (7), sufficient rotational torque necessary for starting can be obtained.If a relatively small starting torque is sufficient, the above-mentioned switch circuit S1 and It is not necessary to omit the resistor R9.

Figure 1g7 shows a fourth embodiment of the present invention,
In this embodiment, a switch circuit 8 is added to the motor drive circuit shown in FIG.
．． and resistance islands are added.

That is, as shown in FIG. 7, a switch circuit S and a resistor island are connected in series between the connection point C and the ground terminal. Even in the breast cage constructed in this manner, sufficient starting torque can be obtained by turning on the eight switch circuits λ only when starting the motor.

Although the water supply invention has been described with reference to examples, the present invention is not limited to these examples. Thus, the present invention provides a low-pass filter in the gynecological circuit of the straight ri and widening thread that amplifies the output of the magnetoelectric transducer (for example, λ, Hall transducer mf21).Therefore, the brushless motor of the present invention According to the drive circuit, the cane of the current widening thread is increased in proportion to the rotational speed of the rotor of the brushless motor (the frequency of the output signal of the magnetoelectric conversion element), and the current flowing through the excitation coil is increased accordingly. It will be increased. Therefore, when an external force is applied to the rotor and its rotational speed is reduced (or stopped), the gain of the downstream width-enhancing yarn decreases a little.
Since a large current does not flow through the excitation coil, the consumption per current is reduced, and the heat generation of the excitation coil can be effectively suppressed.

However, by using the above-mentioned configuration and selecting appropriate circuit constants, sufficient power can be obtained at the motor's rated rotation.
In addition to being able to obtain rotational torque, it is possible to suppress the occurrence of offset voltage due to temperature changes (temperature drift) and aging, etc., to a small level without making adjustments.In other words, it is possible to automatically cancel offset voltage in the motor drive circuit itself. (
automatic removal) function.

[Brief explanation of the drawing]

Fig. 1 is a drive circuit diagram of a conventionally known two-phase sine wave sliding brush motor, Fig. 2 is a waveform diagram showing whether the voltage applied to the coil has an offset or not, and Fig. 7 are for explaining the present invention in detail, FIG. 3 is a circuit diagram of a brushless motor drive circuit showing the first embodiment of the present invention, and FIG. 4 is a circuit diagram of a brushless motor drive circuit showing a first embodiment of the present invention. 5 to 7 are circuit diagrams of brushless motor drive circuits showing second to fourth embodiments of the present invention, respectively. In the codes used for (IK2+...
......Hall element L31 (4+...
−・・Operation amplifier (IO)・・・・・・・・・・・・・・・
・・DC amplification system U ・・・・・・・・・・・・・・・Low bass fill “2+About a+B%, R9・・・Resistance C1・・・・・・・・・・・・・・・...Capacitor S ・
・・・・・・・・・・・・It is a switch circuit. Agent Saturn Masaru Matsuzai Figure 1 Figure 2

Claims (1)

[Claims] In a brushless motor drive circuit in which the output of a magneto-electric transducer that detects a rotational position of 0-1 is amplified by a DC amplification thread having an operational amplification device and applied to an excitation coil, the DC amplification line is applied to an excitation coil. A brushless motor drive circuit characterized by providing a low-pass filter in the feedback circuit of the system.