JPS6040274B2 - phase difference detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase difference detector, and particularly to a phase difference detector for an electric motor.
The present invention relates to a phase difference detector used for locked loop (hereinafter referred to as PLL) control.

Motor speed control generally uses a method in which the rotational speed is detected as an electrical signal and this value is fed back. However, if more precise speed control is required, a method proportional to the set value of the rotational speed is used. A PLL control method is used in which a phase difference between a signal frequency and a signal frequency proportional to a detected value is determined and the phase difference is always set to a maximum of 4.

That is, in conventional motor phase difference detection methods, regardless of whether the method is analog or digital, the phase difference signal is averaged by an integrating circuit or a filter circuit, and once converted to direct current, which is input to a voltage controlled oscillator.

However, in the case of controlling a motor such as an induction motor, the response speed is slow because the frequency range is relatively low, which adversely affects control characteristics. Next, a block diagram of an example of a speed control system of a conventionally used PLL control type electric motor will be explained with reference to FIG.

That is, a signal from the frequency generating circuit 1 that commands the rotational speed and a sensor such as an encoder or position detector that generally uses an optical magnetic field or the like is coupled to the motor and generates a rectangular wave or sine wave output proportional to the rotational speed. The signal from 2 is converted into a DC signal through a phase comparator circuit 3 that outputs the phase difference between the output signals of the frequency generating circuit 1 and the sensor 2, and a low pass filter (LPF) 4 that averages the phase difference signal. This DC signal is converted into a required rectangular wave or sine wave signal via a voltage controlled oscillator 5, and this signal is used to drive a motor by a drive circuit 6 consisting of a logic circuit at the next stage, a gate amplifier, a thyristor inverter, etc. 7 will be driven.

As mentioned above, such a PLL control method has a negative effect on the performance characteristics of the control system because it is converted into a -degree DC signal through the phase comparator circuit 3 and the low-pass filter (LPF) 4, and the circuit is also complicated. It also had the disadvantage of slow response.

The present invention has been made in view of the various drawbacks of the conventional phase difference detector described above, and is capable of instantaneously and continuously processing the aforementioned phase difference detection signal by a combination of a multiplication function and multiphase of two or more phases. It is an object of the present invention to provide a phase difference detector which is capable of processing these functions directly within the detector without performing them using an external circuit.

Next, the principle of the phase difference detector of the present invention will be explained with reference to FIGS. 2 to 4.

First, FIGS. 2 and 3 show the structure of a phase difference detector.

That is, the rotor 11 having a permanent magnet or excitation winding structure is configured to rotate within the stator 12 at a rotational angular velocity i, and the rotor 111 of the stator 12 is located at a position opposite to the rotor 111. Magnetic effect elements (Hall elements) 13 and 14 made of GaAs or the like are attached at intervals, that is, in a two-phase arrangement. Next, the operating principle will be explained with reference to FIG. 4. The current terminals 15 and 16 of the magnetic effect elements 13 and 14
A predetermined current is passed through. Therefore, when the rotor 11 rotates at a rotational angular velocity of i (i is variable between 1 and n), the magnetic flux density B applied to the magnetic effect elements 13 and 14
, B2 are expressed by the following equation. B;Ac.

s(wit+gu)...(118=ASin
(wit+?) ... (2} However, A is a constant. In this case, if one magnetic effect element 13 and 14 each does not satisfy the equations {1} and '2), increase the number of elements, By combining these elements, it is easy to achieve equivalent sine conversion.

At this time, the currents flowing through the current terminals 15 and 16 are i,,j
2. It's il Ni CCOS
...[3} i2 CSin's IT
…,．． ．． {4, where C is a constant.

Then, since the magnetic effect elements 13 and 14 have a multiplication function, a voltage expressed by the following formula is generated at the respective output terminals 17 and 18.

v. =B.・i. =A.CCOS's itcOS(wit
10○) = 1'2A・C {COS (2 it + ○) 10C
OS○}. ...(5'v2=B2・i2!A・CSin
It・Sin (wit+○): 1′ secretion・C{cos?
-cos(2wit+gu)}. ...(6}This {5),
Equation (2) is established from the phase difference ◇ between the reference signal i,, j2 and the magnetic flux density B,, & by the rotor 1, and the vibration term of i in 2, but this {5}, ■Shiki no Kazurochi v;v,
If we take 10v2, V=V. 10V2=1'2A・CcOS◇
...{71, the vibration term disappears, and the cosine with a phase difference of 0 is obtained.

Furthermore, this v is a signal that has no time delay and is determined continuously.

Therefore, if this signal v is used for PLL control, it is no longer necessary to use an integrating circuit or a filter, and the drawbacks of the prior art can be eliminated. The value of v for this signal is curve 2 in Figure 5.
Phase beast like 1: 0 point and ground are constant, it is not a perfect linear signal, but it is a stable 0 as a signal for PLL control etc.
It only needs to be linear at a point, and if a particularly linear signal is desired, it can be solved by using a synchro-linear converter.

The above example is a two-phase case, but in the case of a three-phase or multi-phase configuration, for example, in the case of three-phase, three magnetic effect elements are arranged in a three-phase arrangement of every 1200 degrees or every 60 degrees, and each magnetic effect element It is sufficient to flow symmetrical three-phase current to the current supply terminal of
All three output signal voltages may be added.

The same applies to other polymorphisms as well. When multiphase is used, there is an advantage that variations in the characteristics of individual magnetic effect elements and variations in the precision of arrangement work are canceled to some extent, and detection accuracy is further improved. Next, a specific example using the phase table detector of the present invention will be explained with reference to FIG.

That is, when two signal currents from a frequency generation circuit (two-phase generation circuit) 31 that commands the rotational speed are input to a magnetic effect element (13, 14 in FIGS. 2 to 4) 32 as a sensor, this The output signals of the magnetic effect element 32 are '5}, [6
v, , v2 as shown in Equation 1, and this output signal is sent directly or by an adder circuit to the next stage logic circuit, The signal is guided to a drive circuit 36 composed of a gate amplifier, a thyristor inverter, etc., and a motor 37, which is a type of AC motor, is operated.

That is, in the case of this specific example, the conventional phase comparator circuit 3 and low-pass filter (LPF) 4 are not required at all, so the stability of the control system is not affected, and the components of the control system can be simplified. The response is extremely fast and can be done instantaneously and continuously.

Although this embodiment has been described for a two-phase case, it is almost the same in a three-phase or multi-phase configuration.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an example of a conventional phase difference detector, FIGS. 2 to 5 are diagrams explaining the principle of the phase difference detector of the present invention, and FIG. 3 is a cross-sectional view of FIG. 2 taken along the x-X line, and FIG. 4 is an explanation showing the arrangement of the magnetic effect element and its peripheral circuit. 5 is a curve diagram showing the relationship between phase difference and v, and FIG. 6 is a block circuit diagram of a specific example using the phase difference detector of the present invention. 1, 31... Frequency generation circuit, 2, 32...
...sensor, 3...phase comparison circuit, 4...low-pass filter, 5,35...voltage controlled oscillator, 6,36...drive circuit, 7,37...・・・・・・
Induction motor, 11... Rotor, 12...
・Stator, 13, 14... Magnetic effect element, 15
, 16... Current terminal, 17, 18...
voltage terminal. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. If a current corresponding to the rotational angular velocity of the rotor is applied to each of a plurality of magnetic effect elements fixed in a phase arrangement to a stator opposite to the rotor of the electric motor, the current generated by the rotation of the rotor is applied. A phase difference detector characterized in that it uses a voltage signal that is proportional to magnetic flux density and has only the cosine of a phase difference obtained by adding a plurality of output signal voltages generated in the plurality of magnetic effect elements.