JPS6385911A - Servo circuit - Google Patents

Abstract

PURPOSE:To simplify circuit constitution, by constituting a character compensation circuit to an adder circuit with a digital circuit, and providing a PWM (pulse width modulation) circuit at the rear stage of the adder circuit. CONSTITUTION:An analog AFC (automatic frequency control) signal, after being digital-signalized at an amplifying and waveform arranging circuit 31, is inputted to a speed discrimination circuit 32, and is used for the discrimination of the rotation speed of a motor. The output is inputted to the characteristic compensation circuit 33, and is processed so as to obtain a required control characteristic. An APC signal is also digital-signalized at an amplifying and waveform arranging circuit 34, and is inputted to a phase discrimination circuit 35, and is used for the discrimination of the rotation phase of the motor. The output is processed so as to obtain the required control characteristic at a characteristic compensation circuit 36. The outputs of both characteristic compensation circuits 33 and 36, after being added at the adder circuit 37 constituted as the digital circuit, are PWMed at the PWM circuit 38. The output of the PWM, after being rectified at a rectifier circuit 39, is sent to the motor 40, and controls the rotation of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a servo circuit that controls the rotational speed and rotational phase of a rotating body such as a motor.

(Prior art) As a servo circuit that controls the rotational speed and rotational phase of a motor, etc., there is a digital servo circuit in which a speed comparison circuit and a phase comparison circuit are digital circuits (Reference ■VTR servo using a digital control method, Katayama, NHK Giken, monthly report October 1971, ■Digital Signal Pr
ocessing LSI for Hol1e VC
R3ervo ct-rcutt, stamp material IEEE T
rans, CE-25, August 41979).

As an output interface for supplying the speed comparison output and phase comparison output (both binary data) to the motor in this digital servo circuit, the binary data is digitally pulse width modulated (hereinafter referred to as PWM). An output method is used. Further, as a low power consumption drive method for motors and the like, a switching regulator type drive method is known.

FIG. 4 is a block diagram showing the configuration of a servo circuit having the above-mentioned output interface method and drive method, respectively.

In FIG. 4, an automatic frequency control (hereinafter referred to as AFC) signal indicating the rotational speed of the motor, which is fed back from the motor, is transmitted to the amplification/waveform shaping circuit 1.degree. speed discrimination circuit 12. P
WM circuit 13. Ripple filter 14. Characteristic compensation circuit 1
5 to the adder/amplifier circuit 16. On the other hand, an automatic phase control (hereinafter referred to as APC) signal indicating the rotational phase of the motor, which is fed back from the motor, is also transmitted to the amplification/waveform shaping circuit 172, the phase comparison circuit 18. PWM circuit 19° ripple filter 20. It is applied to the addition/amplification circuit 16 via the characteristic compensation circuit 21. The output of this addition/amplification circuit 16 is the PWM circuit 22. The signal is applied to the motor 24 via the rectifier circuit 23 to control the rotational speed and rotational phase of the motor 24.

The speed discrimination circuit 12 and the phase discrimination circuit 18 are digital circuits as described above. Since the characteristic compensation circuit 15.21 and the addition/amplification circuit 16 are analog circuits, the ripple filter 14.20 converts the output of the PWM circuit 13.19 into DC.

Furthermore, since the addition/amplification circuit 16 and the like are analog circuits, a PWM circuit 22 is provided at the subsequent stage to convert the signal converted into an analog signal by the filter 14.20 back into a digital signal. .

FIG. 5 shows a part of the specific circuit shown in FIG. 4. FIG. 5 shows a sawtooth wave as a reference signal for comparison in the PWM circuit 22. In FIG.

However, in the above configuration, there is a problem in that the circuit configuration becomes complicated because it is necessary to perform PWM twice.

(Problems to be Solved by the Invention) As described above, in a servo circuit that employs a PWM method as a control signal supply method to a motor and a switching regulator method as a motor drive method, PWM overlap has conventionally been used. Therefore, there was a problem that the circuit configuration became complicated.

Therefore, an object of the present invention is to eliminate duplication of PWM and provide a servo circuit with a simple circuit configuration.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention uses a characteristic compensation circuit and an addition circuit as digital circuits, and a P in the latter stage of the addition circuit.
A WM circuit is provided.

(Function) According to the above configuration, since PWM only needs to be performed once, the circuit configuration can be simplified.

(Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In FIG. 1, an analog AFC signal is converted into a digital signal by an amplification/waveform shaping circuit 31, and then inputted to a speed discrimination circuit 32, which is a digital circuit, and is used to discriminate the rotational speed of the motor. This discrimination output is input to a characteristic compensation circuit 33 configured as a digital circuit, and processed so as to obtain a desired control characteristic.

The APC signal is also converted into a digital signal by the amplification/waveform shaping circuit 34, and then input to the phase discrimination circuit 35, where it is used to discriminate the rotational phase of the motor. This discrimination output is processed by the characteristic compensation circuit 36 so as to obtain the required gAvf control property. In this case as well, the phase discrimination circuit 35. Characteristic compensation circuit 36
is configured as a digital circuit.

The outputs of both characteristic compensation ports 133 and 36 are added by an adder circuit 37 configured as a digital circuit, and then PWMed by a PWM circuit 38. This PWM output is the rectifier circuit 3
After being commutated at 9, it is applied to a motor 40 to control its rotation.

FIG. 2 shows an adder circuit 33 configured as a digital circuit.
FIG. 36 shows an example of the circuit configuration of a conventional analog adder circuit. FIG.

In this case, the respective benefits (9Ga, Gb) are as follows.

FIG. 3(a) shows an example of the circuit configuration of the characteristic compensation circuit 36 provided as a digital circuit, and FIG.
) shows the configuration of a conventionally used analog characteristic compensation circuit.

In this case, the respective profits IWGa and Gb are expressed as follows.

1-FZ-' (3) As detailed above, according to this embodiment, the characteristic compensation circuits 33, 36 and the adder circuit 37 are converted into digital circuits.
There is no need to convert the outputs of the speed discrimination circuit 32 and the phase discrimination circuit 33 into direct current. Therefore, in this embodiment, PWM only needs to be performed once, and the circuit configuration can be simplified.

Further, in this embodiment, the PWM circuit 38 is replaced by the adder circuit 37.
Since it is provided at the subsequent stage, only one PWM circuit is required, and the circuit configuration becomes even simpler.

Furthermore, according to this embodiment, it is possible to fix the reference oscillation signal frequency in the switching regulator system, and by incorporating the digital filter and amplifier into the integrated circuit, it is possible to reduce the number of external components in the circuit. It has the advantage of being possible.

[Advantageous Effects of the Invention 1] As described above, according to the present invention, a servo circuit with a simple circuit configuration can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
Fig. 2 is a circuit diagram showing a specific example of an adder circuit, Fig. 3 is a circuit diagram showing a specific example of a characteristic compensation circuit, Fig. 4 is a block diagram showing the configuration of a conventional servo circuit, and Fig. 5 is a circuit diagram showing a specific example of a characteristic compensation circuit. FIG. 3 is a circuit diagram showing a specific example of a part of the diagram. 31.34... Amplification/waveform shaping circuit, 32... Speed discrimination circuit, 35... Phase comparison circuit, 33.36...
Characteristic compensation circuit, 37... Addition circuit, 38... PWM
Circuit, 39... Rectifier circuit, 40... Motor. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 3

Claims (1)

[Scope of Claims] Rotation speed discrimination means constituted by a digital circuit and for discriminating the rotation speed of the rotary body from a signal indicating the rotation speed of the rotary body fed back from the rotary body; a first characteristic compensating means for correcting the discrimination output of the means to have a desired characteristic; and a digital circuit, the rotation of which is determined from a signal indicating the rotational phase of the rotating body fed back from the rotating body; A rotational phase discrimination means for discriminating the phase, and a second characteristic compensation means for correcting the discrimination output of the rotational speed discrimination means, which is constituted by a digital circuit and has a desired characteristic, and a digital circuit. , comprising an addition means for adding the compensation outputs of the first and second characteristic compensation means, and a pulse width modulation means for pulse width modulating the addition output of the addition means to obtain a rotation control signal for the rotating body. A servo circuit characterized by: