JPS6180412A - Automatic phase controller - Google Patents

Abstract

PURPOSE:To improve the starting characteristics of a motor, etc. by keeping a break mode of an APC loop until an AFC reaches its linear control range and then applying an APC output at a time point when the APC output is delivered in the same direction as the AFC control direction and in said linear control range. CONSTITUTION:When the revolving speed of a motor is accelerated and the outputs of control range detecting circuits 31 and 32 are set at 1, an FF circuit 36 is reset with a switch SW2 turned at the side of a terminal (b). Then the output of the switch SW2 shoes an ordinary AFC (automatic frequency control) linear control range. The output of a switch SW3 can conduct when the output of the SW2 is set at 1. At the same time, the output of an AND circuit 33 is also set at 1. Then the SW3 is turned at the side of a terminal (a). A coincidence circuit 39 compares the signals of both comparators 24 and 30 with each other and delivers 1 when the coincidence is obtained. In other words, 1 is delivered when the outputs of both the AFC and APC (automatic phase control) are decelerated or accelerated. Thus an APC loop is added to a control loop.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an automatic phase control device used, for example, in a video tape recorder (VTR), and more particularly to an automatic phase control device including a frequency control loop.

[Technical background of the invention]

Generally, in VTRs, automatic frequency control loops (AFO loops) and automatic phase control loops (APO loops) are provided to control the rotary head disk motor and capstan motor, respectively, to ensure stable recording and playback operations. ing. For example, AFO%AP of a disk motor
An example of the O servo circuit is shown in the block diagram of FIG. To explain the operation of this circuit, during recording, a vertical synchronizing signal (Vs) separated from the recording video signal is inputted through the terminal (1) and inputted into the terminal b frequency dividing circuit (3). Here, the i-divided signal is input to one input terminal of the phase comparator (4).

On the other hand, the rotational phase of the disc motor (5) is
The PG head (6) generates pulses synchronized with the rotation of the
), and this pulse is input as a feedback signal to the other input terminal of the phase comparator (4) via the waveform shaping circuit (force). The phase difference with the PG pulse, which is the feedback signal from the disk motor (5), is detected by the phase comparator (4).In addition, during playback, the switch SW is switched to the terminal a side, so that the vertical The output of the voltage controlled oscillator (2) that generates a signal with a frequency that matches the synchronization signal frequency is A
It is used as a reference signal for PO system servo. Furthermore, the rotation speed of the disk motor (5) is determined by the FG (frequency generator) head (
8), and this output is input to the frequency discriminator Ql via the waveform shaping circuit (9). Then, the rotation frequency is detected here. The outputs of the phase comparator (4) and the frequency discriminator 0C are added by the adder αυ, and the disc motor (5) is driven via the motor drive amplifier (lz). With this configuration, the disc motor (5) Rotates in synchronization with the reference signal.

By the way, in the servo circuit configured as described above,
The detection characteristics of the phase comparator (4) and the frequency discriminator αl generally have saturation characteristics or nonlinear characteristics. In other words, linear control is applied only near the stable point, and saturation characteristics etc. are provided when the stable point is significantly deviated from the stable point. Figure 5 shows the detection characteristics of AFO and APO. Here, (8) in the figure shows the relationship between the AFO detection voltage and the frequency, and (B) in the same figure shows the relationship between the APO detection voltage and the time difference (phase difference).

Note that fo is the target frequency of control, and To is the target time difference. In FIG. 5, the AFC detection characteristic outputs a low voltage as the frequency increases to decelerate the motor (5). Further, it is configured to output a linear control output in a frequency range from fl to fl including the target frequency fO, and to have the median value of the control output at fo. Similarly, APO
As for the detection characteristics, when the phase difference (time difference) becomes large, a high voltage is outputted and the motor (5) is accelerated. Also, the target time difference T
A linear control output is output in the time difference range from Tl to Tl including O, and the median value of the control voltage is set at To. Furthermore, when the AFO detection voltage is outside the linear control range, the APC output voltage is forced to the median value (=i
By fixing the voltage to iVl), a capacitor of a lag filter with a large time constant, which is normally inserted in the APC loose circuit, is charged with the voltage value of iVl, thereby improving the transient characteristics.

Next, the servo operation of the servo circuit having the detection characteristics shown in FIG. 5 will be described in further detail using FIG. 6. For example, if a disturbance such as a load change is applied to the motor at time t and the motor rotation speed increases, the effect of the FG multiplication signal will appear as shown in Figure 6), and the AFO output will decelerate the motor. In addition, as the rotational speed of the motor increases, the phase difference between the reference signal and the feedback signal decreases, so the APC output also decreases to decelerate the motor. In this way, both the AFO and A20 outputs are controlled in the direction of decelerating the motor, and the motor rotational speed and rotational phase are quickly returned to the synchronized state.

[Problems with background technology]

- By the way, when a motor is started, it generally has characteristics different from the transient characteristics in the steady state. In other words, when starting the motor, AFO brings the motor rotation speed to around the target value (at this time, AFO
The detection output of PO is fixed at 100v1 as described above). When the AFO enters the linear control range, the AP
O starts working. At this point, for example, if the APO output is in the motor deceleration direction outside the linear control range (the initial phase of the feedback signal is arbitrary, and this naturally occurs), the motor rotation speed will be lower than the target value. Although it is still small, the APC output acts in the direction of decelerating the motor and slows down the transient response. This phenomenon becomes stronger as the linear control range of the AFC becomes larger (that is, as the initial rotational speed of the motor becomes smaller), resulting in a large delay. That is, there has been a conventional problem in terms of the starting characteristics of the motor.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide an automatic phase control device with excellent starting characteristics.

[Summary of the invention]

The present invention interrupts the APO loop until the AFC reaches its linear control range when starting a motor, etc., and when the range is reached, the APO loop is stopped at a point where the APO output is output in the same direction as the AP'O control direction. The output is applied to the AFO output. That is, by selecting the point in time at which such a phase feedback signal is generated and applying the APO loop, it is possible to improve, for example, the starting characteristics of a motor.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 3.

FIG. 1 is a block diagram showing an embodiment of an automatic phase control device according to the present invention. First, its configuration will be explained. Qυ
is a phase reference signal input terminal, and ■ is a phase feedback signal input terminal. A phase comparator is connected to these input terminals Qυ and @, and its output terminal is connected to the terminal a side of the switch SWI and to the + side input terminal of the comparator 1241. An input terminal (c) to which a voltage of 1v2 is applied is connected to the terminal side of the switch SW1.
The movable terminal of I is connected to the APC output terminal +261. Punishment is the input terminal where the frequency feedback signal is input,
A frequency discriminator (to) is connected to this, and its output terminal is connected to the AFO output terminal and the + side input terminal of a comparator (to). The output of the frequency discriminator (c) is also connected to the control range detection circuit C31) and the control range detection circuit 03, and these output terminals are connected to the terminal a side of the switch 8W2,
They are respectively connected to the b side. And switch SW
The two common terminals are connected to one input terminal of the AND circuits (To) and (B). (g) is the motor start signal input terminal, which is connected to the R, -8 flip-flop circuit (to)
, C3η.几-87
The output terminal Q of the 1J tube flop circuit (to) is switch 8
The reset terminal R of the R-8 flip-flop circuit is connected to the output terminal of the switch SW2. The reset terminal R of the R-87 lip-flop circuit (37) is connected to the output terminal of the AND circuit, and the output terminal Q is connected to the other input terminal of the AND circuit. The comparator C4, (to) -
The input terminal (to) to which a voltage of 1v2 is applied is connected to the side terminal, and the output terminals of the comparator (24) and (to) are connected to the two input terminals of the matching circuit (EX-N08 circuit) CHI, respectively. ing. The output terminal of the BX-NOR circuit 1.31 is connected to the terminal a side of the switch SW3, and the input terminal (40) to which the input "1" is applied is connected to the terminal a side of the switch SW3. Common terminal is ANDNO
circuit 1 is connected to the other input terminal, and this ANL) circuit p
The output of t+ is used for switching the switch SW1.

Further, the output of the AND circuit example is used for switching the switch 8W3.

Next, the operation of this embodiment will be described. First, the operation of each circuit will be briefly described, and then, based on the time chart of FIG. 3, the operation of the process from motor startup to phase locking will be explained.

The phase comparator has a reference signal input from the terminal (2υ (for example, in a VTR, as mentioned above, the vertical synchronization signal during recording, and a signal whose frequency matches the vertical synchronization signal frequency during playback) and the terminal. The phase difference with the phase feedback signal (output of the PG head provided on the motor) is detected, and a control voltage according to the detection characteristics as shown in FIG. 5(B) is output.

The frequency discriminator (c) detects the frequency of the frequency feedback signal (output of the FG head installed in the motor) input from the terminal and outputs a control voltage according to the detection characteristics as shown in Figure 5 to the AFO output terminal. Output to (to).

As will be described later, the control range detection circuit C31) and the detection circuit G3 are unique to this embodiment, and are provided to improve the characteristics when starting the motor. The detection circuit Gυ detects a narrow linear control range for APO loop switching during startup,
The detection circuit C33 detects the normal linear control range. This detection output will be explained with reference to FIG. 2 shows the output (AFO control voltage) of the frequency discriminator (to) shown in FIG. That is, the detection circuit Gυ outputs "1" (high level signal) when the frequency detected by the frequency discriminator (to) is between f3 and f4, and outputs "0" (low level signal) in other ranges. Output. Similarly, the detection circuit O3 outputs "1" when the detected frequency is between f1 and f2 (within the normal linear control range), and outputs "0" when it is in other ranges. In addition, the output of the frequency discriminator (to) is the middle value (2v2) of the maximum control voltage value at the center of the linear control range (frequency fo).
is set to be.

Next, the operating process from motor starting to phase locking will be explained based on the time chart of FIG. 3.

In this figure, ~(J)m indicates the output of each point A-J in FIG. First, when starting the motor, a starting signal (see the fifth position) is input to the input terminal (c). As a result, the R-8 flip-flop circuit (301C37) is set (fifth
Figure (B), (see C1). Therefore, the switch SW2 is switched to the terminal a side. At this time, the frequency discriminator (c)
The output (AFO output) is naturally outside the linear control range,
The output of the control range detection circuit C31+ is "0" (fifth
(see figure). Therefore, this output is input to the AND circuit □□□ via the switch SW2, and the output of this circuit (G) becomes rOJ. Here, the output of switch 8W2 is changed to the fifth
In the figure, the output of the AND circuit (c) is shown in figure 0. Therefore, the switch SW3 is turned to the terminal side. Similarly, the output of the AND circuit (B) also becomes "0" (see Figure 5 (J)), the switch SW1 is turned to the terminal side, and the terminal (to) receives the voltage of IV2 input to the terminal. The voltage value is obtained as the APO output which becomes the target value.

The rotation of the motor is accelerated, and at time t1 the frequency discriminator (
When the output of (c) reaches a value corresponding to the normal linear control range, the output of the linear control range detection circuit G2 (see FIG. 5 (8) becomes "1". However, the switch S
Since W2 remains on the terminal a side, the switch SW is still
The output of 2 is ti of "0".

When the motor is further accelerated, the output of the detection circuit Gυ becomes "1" (time tz), and the output of the 7-lip-flop circuit (
) will be reset. As a result, the switch 8W2 is pushed to the terminal side, and from now on, unless the upper start signal is input to the terminal (to), the output of the switch SW2 will be the normal AFO output.
This indicates the linear control range. And switch SW
Since the output of 2 becomes "1", the AND circuit (b)
The output of the switch 8W3 (see FIG. 5(I)), which had been gated by this, becomes conductive. Also, AND circuit (to)
The output of is also "1", and the switch SW3 is turned to the terminal a side. Therefore, the output of the EX-NOR circuit 131 (see FIG. 3 (q)) is input to the AND circuit (2). In other words, the output of the EX-NOR circuit ■ is used as it is as the APC output selection control signal of the switch SW2. It will be done.

Next, the operation of the EX-NOR circuit will be described. Terminal (
The voltage value 10η applied to the comparator (24), (to)
is supplied to the negative terminal of comparator C! When (a) and (7) are smaller than APO1Al2, the motor is decelerated, and when it is larger than APO1Al2, the motor is accelerated. Then, the output of the comparator (24, (to)) is compared in the EX-NOR circuit G3, and when both signals match, "1" is output from this circuit c3. That is, both APO and AFO outputs are Outputs "l" when in deceleration mode (output of both comparators Q4 and BIN is "0") or acceleration mode (output of both comparators (24) and Glossy is "1"). To explain with Figure 3, 1
At the 2nd point in time, AFC, APOOlflmo)” was opposed (E
(See (I) in the same figure showing the output of the X-NOR circuit C3'll), and the modes match for the first time at time t3. In other words, even though the AFO output shows a linear control range from time point 12 to time point 13, since the output modes of APO and AFO do not match, '-v2 is output as the APO output. That will happen. and,
When the modes match at time t3, A
The output of the ND circuit (b) becomes "1" and the switch SW1 is switched to the terminal a side. Therefore, the phase comparator (c)
The output of is directly outputted to the terminal (A) via the switch SW1, and the APO loop is added to the control loop. Furthermore, as the output of the AND circuit (b) becomes "1", the R-8 flip-flop circuit r37) is reset, and the output of the AND circuit (to) becomes "0", causing the switch 8W3 to move to the terminal side. Can be switched. Therefore,
terminal (output “1” applied with 41K is AND circuit C34
), henceforth, the switch 8W1 will be controlled by the output of the control range detection circuit G2. The switch SW3 remains switched to the terminal side unless a motor start signal is input to the terminal.

Through the process described above, the AFO and APO loops return to normal mode.

As described above, according to this embodiment, the conventional problem of deterioration of transient characteristics due to the arbitrariness of the initial phase of the phase transition signal at the time of startup is improved. That is, AFO output and AP
Since the APO loop is not applied to the AFO loop only when the control directions of both O outputs match, a very smooth pull-in characteristic can be obtained.In addition, in this embodiment, two AFO linear control range detection circuits are provided. However, this is due to the following reasons. In other words, when the setting of the addition ratio between AFO output and APC output is selected so that APO has a strong effect on AFO, if the range in which APC is effective is set to the normal wide linear control range, the effect of APC looseness will be reduced. This is to prevent deterioration of the transient response due to AFO loose drag. Therefore, depending on the addition ratio of the AFC output and the APO output, one of the detection circuits (detection circuit C31, switch SW2, R-S flip circuit lower 1 circuit) may be omitted.

Further, in this embodiment, the operation at the time of starting the motor has been described, but it is also applicable to the case where the rotation speed changes from one rotation speed to another.

Further, although the present embodiment has been described with an analog servo system in mind, the present invention can also be applied to a digital servo system, and in this case, the device can be configured more simply.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to shorten the transient state from the servo disconnection state to the return to the normal servo loop, and for example, it is possible to obtain excellent starting characteristics when starting the motor. .

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the automatic phase control device according to the present invention, Fig. 2 is a diagram showing the characteristics of the device shown in Fig. 1, and Fig. 3 is a timing chart of the device shown in Fig. 1. , FIG. 4 shows the conventional automatic phase control 23... Phase comparator, 24. 30... Comparator, 28... Frequency discriminator, 3L32... Control range detection circuit, 33 .34
・・・・・・AND circuit, 36.37 ・・・・・・
R-8 flip-flop circuit, 39...E
X-NOR circuit, SWI, SW2, SW3 River... Switch. Agent: Patent Attorney Noriyuki Chika (Figure 1, Figure 2, Figure 3, U)

Claims (1)

[Claims] In an automatic phase control device having a frequency control loop and a phase control loop, the target value of the phase control loop is fixed when the frequency control is outside the linear control range, and the frequency control is outside the linear control range. a detection means for comparing the frequency control output and the phase control output and detecting that both output control outputs in the same direction; In a transient state where the transition is from outside the range to within the range, after the output of the discrimination means changes from an output indicating outside the linear control range to an output indicating within the range, the frequency is determined at the time when the detection output of the detection means is obtained. An automatic phase control device comprising means for applying a phase control loop to a control loop.