JPH0527351B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is applicable to tape recorders, record players,
This invention relates to a brushless motor that can be used in video tape recorders and the like.

Conventional configuration and its problems Brushless motors, in which armature current is switched by transistors and generated torque is controlled by command input, are widely used in the above-mentioned industrial fields. A conventional example of a typical configuration using a three-phase armature winding is shown in FIG. In FIG. 1, the rotational positions of the multi-pole magnetized permanent magnet rotor 1 and the respective windings L ₁ to _{L 3} of the armature winding 3 are detected by the position detector 2, and the position signal switching circuit 5, 7. The position signal switching circuits 5 and 7 each have a three-differential configuration, and their collectors are connected to the bases of the transistors Q ₁ to Q ₃ and Q ₄ to Q ₆ of the corresponding output transistor groups 6 and 8, respectively. The emitters of the output transistor groups 6 and 8 are connected in common, and the collectors are connected to one end of the corresponding phase of the armature winding 3 in a push-pull configuration. The common emitters of the output transistor group 6 are connected to a power source 16, and the common emitters of the output transistor group 8 are grounded via a resistor 13. Ungrounded terminal 1 of resistor 13
4 is applied to one input of the current output type differential amplifier circuit 4, and the torque command voltage 15 is applied to the other input of the differential amplifier circuit 4.
The output is applied to the position signal switching circuit 7 in a current mirror format. The other ends of the armature windings 3 are commonly connected and connected to one input 12 of the differential amplifier circuit 9, and the other input 11 of the differential amplifier circuit 9 is connected to the voltage divider 1.
0, 1/2 of the voltage of the power supply 16 is applied. The output of the differential amplifier circuit 9 is applied to the position signal switching circuit 5 in a current mirror format.

The operation of FIG. 1 will now be explained assuming that transistors Q ₃ and Q ₄ are in a conductive state. The armature current flows through the path of transistor Q ₃ → winding L ₁ → winding L ₃ → transistor Q ₄ → resistor 13, the voltage at terminal 14 and torque command input voltage 15 are compared, and the negative feedback circuit The difference is controlled to be zero.
As a result, the armature current is controlled by the torque command voltage 15, and therefore the torque generated by the motor is controlled by the torque command voltage 15. On the other hand, the windings L ₁ , L ₂ ,
The common connection point of _L3 is maintained at 1/2 of the power supply voltage by the negative feedback circuit formed by the differential amplifier circuit 9. Therefore, the potential of the armature winding 3 changes around 1/2 of the power supply voltage, and since transistors Q ₅ and Q ₄ operate with approximately the same collector-emitter voltage, the torque command voltage or When the voltage across the windings L ₁ and L ₃ increases due to an increase in the motor rotation speed, the transistors Q ₃ and Q ₄ reach saturation to approximately the same extent, improving the utilization rate of the power supply voltage.

However, in order to maintain the potential of the common connection point of the armature winding 3, the common connection point must be connected to the input 12 of the differential amplifier 9, which requires wiring. As tape recorders, record players, video tape recorders, etc. are becoming smaller and lighter, this has resulted in a disadvantage that the number of lines is large, especially when the drive circuit is integrated, leading to an increase in costs. Furthermore, if the output voltage of the voltage divider 10 deviates from 1/2 of the power supply voltage, as the armature current increases, only one of the output transistor groups 6 or 8 will be saturated first, so that However, it also has the disadvantage that the current does not increase and the utilization rate of the power supply voltage deteriorates.

Purpose of the Invention The present invention eliminates the drawbacks of the above-mentioned conventional example, reduces the number of wires, is resistant to element variations,
The present invention provides a brushless motor suitable for integrating a drive circuit.

Structure of the Invention In order to achieve the above object, the present invention includes a multi-pole magnetized permanent magnet rotor, a multi-phase armature winding whose one end is commonly connected, and the rotor and the armature winding. a position detector for detecting the rotational position with respect to the armature winding; a first pair of push-pull output transistors connected to each phase of the armature winding and having a number equal to the number of phases; and a first position detector for detecting the current of the armature winding. a current detection means, a first amplifier for amplifying the difference between the output signal of the first current detection means and a motor torque command input signal, and an output of the first amplifier according to an output of the position detector. a first position signal switching means for switching between the output transistors and determining the energization phase of the armature winding by one transistor of the output transistor pair; and a second position signal switching means for outputting a signal corresponding to the base current of the one transistor. a detection means, a second amplifier for amplifying the difference between the respective output signals of the first and second current detection means, an output of the second amplifier being switched in accordance with an output of the position detector; and second position signal switching means for determining the energization phase of the armature winding by the other transistor of the output transistor pair, the base current of the one transistor and the current flowing through the first current detection means. The conduction state of the other transistor is controlled by the second amplifier so as to keep the ratio constant, and the torque is generated according to the torque command input. In addition to controlling the torque by comparing it with the command input, it also detects the current corresponding to the base current of the output transistor, compares it with the armature current, and controls the push-pull operation so that the ratio is constant. This eliminates the need for wiring between the common connection point of the armature windings and the drive circuit, and the power supply voltage of the output stage can be used effectively regardless of element variations.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the drawings. FIG. 2 is a diagram showing its configuration. The permanent magnet rotor 1 is magnetized to have eight poles, and the three-phase electronic winding 3 is composed of windings L ₁ , L ₂ , and L ₃ that are commonly connected at one end.
The rotational positions of the rotor 1 and the armature winding 3 are detected by a position detector 2 and applied as three-phase signals to position signal switching circuits 5 and 7. The position signal switching circuit 5
The output transistor group 6 is driven by a three-differential configuration using NPN transistors. Position signal switching circuit 7
has a three-differential configuration using PNP transistors and drives the output transistor group 8. The emitters of the output transistor group 6 were commonly connected to the power supply 16.
Output transistor group 8 consists of PNP transistors Q ₁ , Q ₂ , Q ₃ , and NPN transistors Q ₄ , Q ₅ , Q ₆ whose emitters are commonly connected to current detection resistor 13 .
Consists of. Transistors Q ₁ and Q ₄ , Q ₂ and Q ₅ , Q ₃ and
Q ₆ has a push-pull configuration, and its collectors are commonly connected to windings L ₃ , L ₂ , and L ₁ . Two current output terminals 18, 1 by current mirror
The non-inverting side input (+) of the differential amplifier circuit 4 having 9
A torque command voltage 15 is applied to the inverting side input (-), and a voltage at a terminal 14 of a resistor 13 is applied to the inverting side input (-). The output terminal 19 is connected to the common emitter of the position signal switching circuit 7, and the output terminal 18 is connected to the non-inverting input of the differential amplifier 20 together with the resistor 17 connected to one end. The inverting input of the differential amplifier 20 is connected to the ungrounded side of the resistor 13, and the output is connected to the low-pass filter 21.
It is connected to the emitter of the position signal switching circuit 5 via.

Next, the circuit operation will be explained. The armature current flows through the path of output transistor group 6 → winding 3 → output transistor group 8 → resistor 13, and negative feedback is formed by differential amplifier circuit 4, position signal switching circuit 7, output transistor group 8, and resistor 13. Control is performed by the loop so that the torque command voltage and the voltage across the resistor 13 are equal. Therefore, the magnitude of the armature current is determined by (torque command voltage/resistance value of resistor 13). Now, depending on the positional relationship between the rotor 1 and the armature winding 3, among the output transistors _Q1 to _Q6 ,
Suppose that only transistors Q ₃ and Q ₄ are conducting. Only the emitter current of transistor Q ₄ flows through resistor 13 . The base current of the transistor Q ₄ is supplied from the current output terminal 19 of the differential amplifier circuit 4, and a current of the same magnitude is supplied from the current output terminal 18 to the resistor 17. Resistor 13 and Resistor 17
and the flowing current value are R ₁₃ and R ₁₇ respectively.
and I ₁₃ and I ₁₇ , the input voltage V ₂₀ of the differential amplifier 20 is V ₂₀ =R ₁₇ ·I ₁₇ −R ₁₃ ·I ₁₃ (1). On the other hand, the current amplification factor of transistor _Q4 is h _FE
Then, it can be written as I ₁₃ = (1+h _FE )・I ₁₇ ……(2), so equation (1) becomes V ₂₀ = (R ₁₇ /1+h _FE −R ₁₃ )・I ₁₃ ……(3) . Since the h _FE of the transistor Q ₄ changes with the collector-emitter voltage V _CE as shown in FIG. 3, the differential amplifier 20, the low-pass filter 21,
When the loop gain of the negative feedback loop composed of the position signal switching circuit 5, the output transistor Q ₃ , the windings L ₁ and L ₃ , the output transistor Q ₄ and the resistor 13 is sufficiently high, the input voltage V ₂₀ becomes zero. The collector-emitter operating voltage of transistor _Q4 is automatically determined. Therefore, from equation (3), h _FE = R ₁₇ /R ₁₃ −1 (4). Since the right side of equation (4) is constant, h _FE of transistor Q ₄ is constant. If the torque command voltage changes, the emitter current of transistor _Q4 will also change,
From Figure 3, the collector-emitter voltage of transistor _Q4 also changes automatically. In other words, since the collector-emitter voltage of transistor Q ₄ is automatically controlled according to the emitter current so that the current amplification factor is kept constant, the potential across the windings L ₁ and L ₃ also changes depending on the armature current. It is determined accordingly and operates stably.

As the motor rotates, the rotor 1 and armature winding 3
Even if the rotational position of Q 1 to Q 6 changes and which one of the transistors Q ₁ to _{Q 6} becomes conductive changes, the operating potential of the windings L ₁ , L ₂ , and L ₃ will correspond to the winding current in the same manner as described above. It changes stably.

FIG. 4 shows another embodiment of the invention. The emitters of transistors Q ₇ , Q ₈ , and Q ₉ are Q ₄ , Q ₅ , and
It is connected to the base of Q ₆ , and the collectors are connected in common to the collector of transistor Q ₁₀ . Transistor _Q10 is diode-connected and forms a current mirror together with transistor _Q11 . The collector of the transistor Q ₁₁ is connected to a resistor 17 and a differential amplifier 2 as a current mirror output 22.
0 non-inverting side input. The bases of transistors Q ₇ to _{Q 9} are connected to corresponding phases of position signal switching circuit 7. The configuration of FIG. 4 other than the above is the same as that of FIG. 2, so a description thereof will be omitted.

The base currents of transistors Q ₄ to _{Q 6} are the emitter currents of transistors Q ₇ to _{Q 9} , respectively.
Since the transistors Q ₇ to _{Q 9} are emitter followers, their current amplification factors are sufficiently large and can be regarded as collector currents. These collector currents are integrated and applied to the resistor 17 with the current direction reversed by a current mirror of transistors Q ₁₀ and Q ₁₁ . As a result,
A voltage corresponding to the base current of the transistors Q ₄ to _{Q 6} is generated across the resistor 17, and the collector operating voltage of the transistors Q ₄ to _{Q 6} is increased by a negative feedback loop similar to that in the first embodiment. It is decided.

As is clear from the above explanation, if the brushless motor is configured as in this embodiment, the emitter current of the output transistor group 8 is controlled by the torque command input voltage 15, so that the collector current is controlled and the difference The collector-emitter voltage of the output transistor group 8 is automatically controlled by a negative feedback loop including a dynamic amplifier. That is, the current of the output transistor group 6 is controlled so that h _FE of the output transistor group 8 is a constant value determined by the values of the resistors 13 and 17, and the emitter current is controlled so as to follow the characteristics shown in FIG. The collector-emitter voltage according to I ₁₃ is maintained. This shows that within the range of effective power supply voltage, both output transistor groups 6 and 8 operate without saturation. Therefore, in the configuration of this example, the common winding There is no need to wire to a differential amplifier to fix the connection point to a constant voltage.

Therefore, the current amplification factor of the lower arm transistor is
By keeping h _FE constant, the utilization rate of the power supply voltage can be improved.

Effects of the Invention As explained above, the brushless motor of the present invention automatically controls the collector-emitter voltage by operating the output transistor so that the current amplification factor is always constant, which can be determined by the resistance ratio. Since the operating potential of the wire can be maintained stably according to the current, there is no need for wiring between the common connection point of the armature winding and the drive circuit, and the power supply voltage of the output stage can be used effectively regardless of element variations. This is extremely effective when integrating drive circuits and reducing the size and weight of brushless motor application equipment.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional brushless motor.
Fig. 2 is a block diagram of one embodiment of the present invention, Fig. 3 is a graph showing the relationship between collector-emitter voltage of a transistor and current amplification factor, and Fig. 4 is a block diagram of a second embodiment of the present invention. be. 1... Permanent magnet rotor, 2... Position detector, 3
... Armature winding, 4 ... Differential amplifier circuit, 5, 7 ...
... Position signal switching circuit, 6, 8 ... Output transistor group, 13, 17 ... Resistor, 15 ... Torque command input voltage, 16 ... Power supply, 20 ... Differential amplifier,
21...Filter.

Claims (1)

[Claims] 1. Detecting a multi-pole magnetized permanent magnet rotor, a multi-phase armature winding whose one end is commonly connected, and the rotational position of the rotor and the armature winding. a position detector; a number of push-pull output transistor pairs equal to the number of phases connected to each phase of the armature winding; a first current detection means for detecting a current in the armature winding; a first amplifier that amplifies the difference between the output signal of the first current detection means and the motor torque command input signal; and a first amplifier that switches the output of the first amplifier in accordance with the output of the position detector; a first position signal switching means for determining the energization phase of the armature winding by one of the transistors; a second current detection means for outputting a signal according to a base current of the one transistor; and a second amplifier for amplifying the difference between the respective output signals of the second current detection means, and the other transistor of the output transistor pair, the output of the second amplifier being switched in accordance with the output of the position detector. a second position signal switching means for determining the energized phase of the armature winding according to The brushless motor is configured to control the conduction state of the other transistor by the second amplifier to generate torque according to the torque command input. 2. A current mirror and a resistor are used as the second current detection means, a current output type differential amplifier is used as the first amplifier, and the current output of the differential amplifier is transferred to the current mirror and the first position signal switching means. 2. The brushless motor according to claim 1, wherein the current is distributed between the resistor and the voltage across the resistor as the output of the second current detecting means. 3 The first position signal switching means is a current output type,
An emitter follower transistor is inserted between the first position signal switching means and the base of the output transistor, a resistor is inserted as a second current detection means into the collector circuit of the emitter follower transistor, and both ends of the resistor are inserted. 2. The brushless motor according to claim 1, wherein the voltage is the output of said second current detection means.