JPH01264655A - Phase detecting circuit - Google Patents

Abstract

PURPOSE:To execute a phase detection with a high accuracy by weighting a signal level and amplifying the phase detecting signal or control reproducing signal of a drum motor by means of an inverse logarithmic amplifier. CONSTITUTION:By the rotation of a rotor 1, a phase detecting means 4 detects the magnetic flux change of a magnet 2, and a waveform to contain a ripple is inputted through an inverse amplifier 5 to the inverse logarithmic amplifier composed of a transistor 6, an arithmetic amplifier 8 and a resistance 9. The pulse peak value of a detected output waveform is smaller than the voltage of a reference power source 7 by the degree of a VBE. At such a time, an inverse logarithmic amplifier output is made into an exponential function, an output pulse, in which the peak A vicinity of an input signal is amplified, is obtained when the VBE is increased, a noise due to a leak magnetic flux from the driving magnet 2 is suppressed, and a phase signal is detected with a high S/N. The waveform in the peak vicinity of a phase signal A is a high gain and made into a pulse, and the phase detection is executed with a high accuracy. The inverse logarithmic amplifier output waveform is waveform-shaped by a comparator 10, and it is inputted to the phase control device of the drum motor.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording and reproducing device that records video signals and digital signals on a magnetic tape using a rotating head, and is particularly resistant to noise and has improved detection accuracy. Highly related to motor phase detection circuits.

[Conventional technology]

In consumer magnetic recording and reproducing devices (hereinafter referred to as VTR),
For rotation control of a drum motor equipped with a rotating head,
Speed control to keep the rotational speed constant and phase control to control the rotational phase of the drum motor by vertical synchronization of video signals are often used. Especially the phase.

For control, a magnet is attached to the rotor of the drum motor.

A detection means is placed on the stator to detect changes in magnetization due to rotation of the drum motor.

is described, for example, in JP-A-60-147956.

ing.

Hereinafter, the above conventional example will be briefly explained using FIGS. 7 and 8.

FIG. 7 is a configuration diagram of a phase detection circuit according to the prior art, in which reference numeral 101 indicates a rotor portion of a drum motor, reference numerals 102 and 105 indicate a pair of N and S poles attached to the rotor 101.

Pole magnet, 104 is magnet i'02, 10
means for detecting changes in magnetic flux of No. 5, 105-10B, I
N is a resistor, 109 is a differential amplifier, 110 is a capacitor,
112 is a phase control device for the drum motor.

FIG. 8 is a signal waveform diagram appearing at each part in FIG. 7,
(α) is the output waveform of the magnetic flux change detection means 104, (b)
is the output waveform of the differential amplifier 109, (Q) is the phase control device w
This is the input waveform at t112.

N-pole and S-pole magnets are attached to the rotor 101 of the drum motor, and the old rotor 1 is indicated by an arrow.

Rotate in the direction of. At this time, from the detection means 104.

The waveform shown in Fig. 8 (α) is obtained, and the resistance 105 to 108
, is input to a Schmitt circuit consisting of a differential amplifier 109. In this Schmitt circuit, the 8th
The pulse waveform shown in Figure (b) is output. This pulse waveform is further connected to a capacitor 110 and a resistor 111.

The differential waveform shown in FIG. 8(C) is extracted as an edge signal of the pulse waveform (b) and inputted to the phase control device 112, thereby controlling the phase of the drum motor.

Furthermore, in a VTR, a control signal (hereinafter referred to as a CTL signal) is recorded on the side edge of a magnetic tape, and is used as a reference signal for tracking servo during playback. for example,
The conventional CTL signal reproducing device described in Japanese Patent Application Laid-open No. 145559/1982 will be briefly described below with reference to FIGS. 9 and 10.

FIG. 9 shows another structure of the phase detection circuit according to the prior art, 1°・
6 causes, 150 is a CTL signal playback head, 151
．． .

157 is a capacitor, 152, 135, 136 are resistors, 1 flash is a reference voltage, 164 is an operational amplifier, 158,
159 is a switch that is switched by a binary control signal of 1H1gh level voltage Low level level voltage; 140 is an inverter;

141 is a timing control circuit for switching the switches 138 and 139, and 142 is a waveform shaper.

Figure 10 shows the magnetic pattern and reproduction waveform of the CTL signal recorded on the magnetic tape, and (α) is a diagram of the Deity 50
The magnetization pattern of the CTL signal recorded in % is 1. (b) is the CTL reproduction signal when the magnetization pattern of (α) is reproduced by the reproduction head 150, (0) is the CTL signal network aggregation signal recorded. (d) is the CTL signal when the magnetization pattern in (C) is reproduced.
1゜CTL signal playback head 150
Since this is a differential type head, the magnetization pattern shown in FIG. 10(α) is reproduced during normal reproduction, so that the reproduced signal shown in FIG. 10(b) is obtained from the CTL signal reproducing head 150. The reproduced signal (b) is sent to an operational amplifier 154°4' via a capacitor 161.

is input. During normal playback, switch 158 is open.

Yes, switch 139 is closed. As a result, the gain of the east operational amplifier 134 is determined by the ratio of the resistors 152 and 135, and the high frequency band is limited.

has been done. The output signal of the operational amplifier 154 is input to the waveform shaper 142, where it is compared with an internally set voltage threshold and converted into a CTL pulse.

Fast forward 97 When rewinding or fast forward playback/rewind playback, the running speed of the magnetic tape is fast.J, CTL playback signal (b)
The wave height value becomes even larger. Therefore, if the editing signal shown in FIG. 10 (0) is recorded on the side edge of the magnetic tape, a pseudo CTL signal E will be generated at the signal boundary, exceeding the voltage threshold of the waveform shaper 142. In some cases, erroneous detection of the CTL signal occurs.

For this reason, in the past, in order to prevent this false detection,
7 When rewinding or fast forwarding playback/rewinding playback, switch 1
By closing the switch 38 and opening the switch 139, the operational amplifier 134 is increased by the amount that the gain of the CTL signal is amplified during high-speed reproduction.
By lowering the gain and widening the band, pseudo-C during high-speed playback
T L (Prevents false detection of No. 8.

It had stopped.

[Problem to be solved by the invention]

In the above conventional technology, the jump waveform from the drive magnet shown in Fig. 8 (α) is removed by equipping the amplifier with hiszoline to prevent malfunction of phase detection, but it is installed on the rotor. Since the output amplitude of the detection means 10.1 changes depending on the magnetic flux strength of the magnet, there is a problem in that an error is mixed into the phase information. 1. .

In addition, when detecting a CTL signal during high-speed playback shown in Fig. 9, the gain and band of the amplifier can be changed to
Although this method prevents erroneous detection of signals, it requires a timing control circuit, a switch, etc. for switching, which increases the circuit scale and costs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly accurate phase detection circuit M that is resistant to noise and has a simple circuit configuration.

[Means to solve the problem]

The above objective is achieved by amplifying the drum motor's phase detection signal or control reproduction signal by weighting the signal level using an inverse logarithmic amplifier.

be done.

[Effect]

The inverse logarithmic amplifier has an exponential range depending on the input level of the signal.

Since it has a numerical gain, even if noise is superimposed on the base of the phase detection signal or control signal, the gain against the noise is relatively low compared to the signal.

Therefore, there will be no false positives. In addition, since it has a high gain near the peak of the signal, it is possible to detect the phase with high accuracy.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention, in which 1 is a rotor of a drum motor, 2 is a phase detection magnet, 4 is a means for detecting all changes in the magnetic flux of the magnet 2, and 5 is a circuit configuration diagram showing a first embodiment of the present invention. is an inverting amplifier, 6 is an N P N-type transistor,
7 and 11 are reference power supplies, 8 is a differential amplifier, 9 is a resistor, and 10
is a comparator, and 12 is a phase control device.

゛　7 FIG. 2 is a diagram for explaining the present invention in detail.

Ru.

5 is a diagram of signal waveforms appearing in the circuit of FIG. 1, where (α) is the output waveform of the phase signal detection means 4, (b) is the output waveform of the inverting amplifier 5, and (C) is the operational amplifier 8. (d) is the output waveform of the controller 10.

The operation of this embodiment will be explained below using FIGS. 1 to 5.

As the rotor 1 of the drum motor rotates in the direction of the arrow as shown in FIG. 1, the phase detection means 4 detects a change in the magnetic flux of the magnet 2 and outputs a signal waveform shown in FIG. 5 (α). Since leakage magnetic flux from the drive magnet enters the detection means 4, ripples as shown in (α) are superimposed on the signal waveform.

The signal waveform (α) is input to the inverting amplifier 5, and its output waveform (b) is applied to the emitter and ivy of the transistor B.

The peak value of the pulse of the output waveform (b) is the voltage v of the reference power supply 7
It is smaller than ref by the base-eminter voltage of the transistor. At this time, current 1. flowing through transistors 6 and 8. is the formula (1).

Ic=Isexp(Vnzq/kT)---(1).

Here, ■8 is the reverse saturation current between the base and emitter of the transistor 6, q is the amount of electron charge, k is Boltzmann's constant, and T is the absolute temperature. .

Therefore, the output voltage vO of the operational amplifier 8 is expressed by the formula (2) (%) where R is the resistance value of the resistor 9.

1. It consists of an operational amplifier 8, a transistor 6, and a resistor 9. .

As can be seen from equation (2), the inverse logarithmic amplifier has an exponential function, so as the base-emitter voltage VBE of the transistor increases, the gain becomes extremely high. For example, VBz = 0.6 V, VBE = o at room temperature
, sV, there is a gain difference of 3 saB. 1゜Therefore, Nocilus (5th
(b)) When the signal is input manually, the vicinity of the peak A of the input signal is amplified as shown in FIG. 2, and an output signal (FIG. 5(C)) is output from the operational amplifier 8.

For this reason, the noise caused by the leakage magnetic flux from the drive magneto seen in FIG. 5 (-) is suppressed, resulting in a high S/.

A phase signal is detected at N. Furthermore, the waveform near the peak of the phase signal (α) is pulsed with high gain, allowing highly accurate phase detection.

The signal waveform obtained from the antilogarithmic amplifier (FIG. 5(c)) is waveform-shaped by the comparator 10 as shown in FIG. 3(d), and then input to the drum motor phase control device.

As described above, according to this embodiment, high S/N and highly accurate phase detection can be performed.

Next, a second embodiment of the present invention will be described using FIG. 4.

FIG. 4 is a circuit configuration diagram showing a second embodiment of the present invention, in which the same symbols as in FIG. 1 have the same functions, 21, 22
, 25, 27, 28 are resistors, 24, 26 are PN
PW and NPN type transistors, and 25 is a capacitor.

In the same figure, as the rotor 1 of the drum motor rotates, the phase detection means 4 is detected as shown in FIG.
The Shinbune waveform shown in α) is generated. This signal waveform is amplified by the inverting amplifier 5 and becomes as shown in FIG. 3(b).

This output waveform is shown in Figure 1.

As in the embodiment, the voltage is applied to the emitter 7 of the transistor 6, and at the same time, it is divided by the resistors 21 and 24 and applied to the base of the transistor 2A. At this time, the tiger.

Since the transistor 24 operates in the active region, the collector current flows in accordance with the amplitude of the signal waveform applied to the base. That is, when the pulse amplitude in FIG. 5(b) is small, the collector current is small and the potential of the capacitor 25 is low; when it is large, the collector current is large and the potential of the capacitor 25 is high. The transistor 26 operates so that the resistance value between υ collector and emitter is made variable depending on the potential of the capacitor f25.

Therefore, when the amplitude of the signal obtained from the phase detection means 4 is small, the potential of the capacitor 25 becomes low as described above, so that the base current of the transistor 26 is small.
As a result, the collector-emitter resistance is large, and the signal waveform (a) is input to the inverting amplifier 5 as is. In addition, when the amplitude is large, the potential of the capacitor 25 becomes high, so the collector-emitter resistance of the transistor 26 becomes high (therefore, the collector-emitter resistance of the transistor 26 becomes small), and the signal waveform ( α) is attenuated and input to the inverting amplifier 5.

As a result, even if the signal amplitudes obtained from the phase detection means 4 are different from each other, the signal amplitude input to the inverting amplifier 5 is kept constant, so that the pulse signal output from the comparator 10 rises. The timing is constant.

As explained above, according to this embodiment, even when the signal amplitude obtained from the phase detection means differs from VTR to VTR, or when the signal amplitude changes due to temperature characteristics or aging, the inverse logarithmic amplifier can be used. Since the input signal amplitude can be kept constant, the motor phase detection accuracy can be kept high.

Next, a third embodiment of the present invention, which is different from the embodiments shown in FIGS. 1 and 4, will be described with reference to FIG. 5, in which a negative pulse is generated from the phase detection means 4.

FIG. 5 is a circuit configuration showing a fifth embodiment of the present invention. In this figure, the transistor 6 in FIG. 1 is PH2.

Replaced with transistor 1 and operational amplifier 8.

The input terminals of the comparator 10 are exchanged. .

In the figure, the phase detection means 4 detects a negative pulse.

occurs, so the inverting amplifier 5 outputs a positive pulse. At this time, this positive pulse is higher than the base-emitter voltage of the transistor 31° by VBK from the reference power source 7, contrary to the embodiment shown in FIG.

ing. This positive pulse is used by the transistor 31.

When input to the transmitter, the amplifier composed of the transistor 51, the operational amplifier 8, and the resistor 9 operates as an antilogarithmic amplifier with a polarity different from that shown in FIG. After waveform shaping,
input to the phase control device.

As explained above, according to this embodiment, the positive electrode It is effective not only for pulses but also for negative pulses.

Next, a fourth embodiment of the present invention in which an inverse logarithmic amplifier is used in a control signal reproducing circuit used for controlling the reproducing phase of a capstan of a VTR will be described with reference to FIGS. 6 and 10.
This will be explained using figures.

FIG. 6 shows a circuit #5 configuration that is a small version of the fourth embodiment of the present invention.

In the figure, 41 is a CTL signal reproducing head, 42 is an 8 magnetic tape, and other symbols have the same functions as in FIG.

In the figure, a CTL signal with a duty of 50% is placed at the 10th edge of the magnetic tape 42 as explained in the related art.
The magnetization pattern shown in the figure (σ) is recorded. An editing signal is recorded in this magnetization pattern as shown in FIG. 10(C),
The magnetic tape 42 runs at high speed in the direction of the arrow, and this ta
Figure 10 (d) when reproducing the separated mold using RAD 41
appears on the CTL playback head 41. At this time,
The reproduced waveform has noise E, which is lower in level than the CTL signal, superimposed on it, but as explained in Figure 1, by passing the reproduced signal through the inverse logarithmic amplifier, the noise E is suppressed.
Only the regular pulsed CTL signal is output, and the CTL pulse is input to the phase control device via the comparator 10. Therefore, malfunctions in phase detection due to noise E can be prevented.

As explained above, the present invention is also effective in a control signal reproducing circuit and is a simple circuit.

This can eliminate erroneous detection of the phase detection signal. .

〔Effect of the invention〕

As explained above, according to the present invention, the phase signal of the drum motor is amplified by the inverse logarithmic amplifier.

Therefore, unnecessary components such as ripple components due to leakage magnetic flux from the drive magnet can be removed. In addition, since the peak of the phase signal can be easily detected, highly accurate phase control can be performed.Excluding the drawbacks of the above-mentioned conventional technology, we have partnered with the phase detection circuit M, which has excellent functions.

can do.

[Brief Description of the Drawings] Fig. 1 is a circuit configuration diagram showing a first embodiment of the present invention, and Fig. 1 is a circuit diagram showing a first embodiment of the present invention.
5 is a diagram explaining the operation of the present invention, FIG. 5 is a signal/waveform diagram appearing in FIG. 1, FIG. 4 is a circuit configuration diagram showing the 21st embodiment of the present invention, and FIG. A circuit showing the sixth embodiment? #Configuration Diagram FIG. 6 is a circuit configuration diagram showing the fourth embodiment of the present invention, FIG. 7 is a circuit configuration diagram of the prior art, FIG. 8 is a signal waveform diagram appearing in FIG. 7, and FIG. 9 is a circuit diagram showing the fourth embodiment of the present invention. Another prior art circuit configuration diagram, FIG. 15, is an explanatory diagram of the operation of FIG. 9. DESCRIPTION OF SYMBOLS 1... Rotor of drum motor, 2... Phase detection magnet, 4... Detection means, 5... Preamplifier, 6
... Transistor, 8... Operational amplifier, 9... Resistor: 10... Comparator, 41... CT L signal reproducing head, 42... Magnetic tape. Representative Patent Attorney: Katsutoshi Ogawa, 16 years old
ゞ－゛N Mi scolding U

Claims (1)

[Scope of Claims] 1. A magnet provided at a predetermined position on the rotor of a rotating drum, a detection means that generates a detection signal when facing the magnet, and a detection signal obtained from the detection means to detect the rotation of the drum. A magnetic recording/reproducing device comprising: a rotational phase control means for controlling the rotational phase of the drum; an antilogarithmic amplifier for amplifying only the peak of the detection signal; A phase detection circuit characterized in that it is provided with a comparator that shapes the waveform of a square wave. 2. A preamplifier is provided between the detection means and the antilogarithmic amplifier, and means is provided for varying the input level of the preamplifier according to the amplitude level of the output signal of the preamplifier. The phase detection circuit according to claim 1. 3. A rotational phase control means for controlling the rotational phase of the capstan motor that drives the magnetic tape based on the reproduction control signal obtained by reproducing the control signal recorded on the side edge of the magnetic tape by the reproduction head. The magnetic recording and reproducing apparatus is characterized by being provided with an anti-logarithmic amplifier for amplifying only the peak of the reproduction control signal, and a comparator for shaping the pulse waveform output from the anti-logarithmic amplifier into a square wave. phase detection circuit.