JPH0580740B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a helical scan type magnetic recording/reproducing device, and in particular, to a method for fixing the position of noise appearing on a playback screen during a search playback (quick playback) mode. The present invention relates to a magnetic recording/reproducing device as described above.

[Background of the invention]

In a helical scan type magnetic recording and reproducing device, the rotating head must correctly scan the tracks on the magnetic tape during reproduction, and for this purpose, the capstan motor that drives the magnetic tape must be controlled by speed control. Phase control is performed. On the other hand, in such a magnetic recording/reproducing device, various playback operation modes such as standard playback, continuous playback, slow motion playback, and search playback can be set, and the rotational speed of the capstor motor can be changed for each playback operation mode. A predetermined magnetic tape running speed is set. In this case, during standard playback such as still playback and slow motion playback, and during playback operation mode where there is no significant difference in the running speed of the magnetic tape,
Tracking control can be performed so that the reproduction scanning locus of the rotary head substantially coincides with the trace on the magnetic tape, and by such tracking control it is possible to prevent noise from appearing on the reproduction screen.

However, in the case of search playback, the running speed of the magnetic tape is significantly different from that during standard playback, so it is very difficult to match the scanning locus of the rotary head with the track on the magnetic tape. For this reason, noise due to tracking deviation of the rotary head will appear on the playback screen, but in order to make this noise appear at a fixed position on the playback screen, the capstan motor is set at the above speed. control and phase control.

FIG. 1 is a block diagram showing one conventional example of such a magnetic recording and reproducing device, in which 1 is a drum motor, 2 is
is a magnetic tape, 3 is a rotating head, 4 is a capstan motor, 5 is a capstan, 6 is a frequency divider, 7 is a frequency-voltage converter, 8 is a control head,
9 is a frequency divider, 10 is a reference signal generator, 11 is a phase comparator, 12 is an adder, and 13 is a motor drive circuit.

In the figure, a magnetic tape 2 runs while being held between a capstan 5 which is rotationally driven by a capstan motor 4 and a pinch roller (not shown).
A rotary head 3 rotationally driven by a drum motor 1 reproduces and scans tracks on a magnetic tape 2.

The capstan motor 4 is provided with a frequency generator (not shown), and this frequency generator detects the rotational speed of the capstan motor 4 and generates a frequency signal CFG (Capstan motor) having a frequency corresponding to the rotational frequency.
Frequency Generator signal). This frequency signal CFG is supplied to a frequency-voltage converter 7 via a frequency divider 6, and a speed control voltage having a voltage value corresponding to the frequency of the output signal of this frequency divider 6 is obtained.

On the other hand, the control signal reproduced from the magnetic tape 2 by the control head 8 is supplied to a phase comparator 11 via a frequency divider 9, and is compared in phase with a reference signal SP from a reference signal generator 10.
The phase comparator 11 generates a phase control voltage whose voltage value corresponds to the phase difference between the output signal (ie, phase signal) PH of the frequency divider 9 and the reference signal SP.

The obtained speed control voltage and phase control voltage are added by an adder 12 and are negatively fed back to the motor drive circuit 13, and as a result, the capstan motor 4 is speed controlled so that a predetermined rotational speed is maintained. Further, the phase is controlled so that the phase difference between the phase signal PH and the reference signal SP is constant.

By the way, during standard reproduction, the frequency division ratios of the frequency dividers 6 and 9 are both 1, so the frequency signal CFG is directly transmitted to the frequency-voltage converter 7, and the control signal is directly transmitted as the phase signal PH. The signal is supplied to a phase comparator 11. At this time, the speed of the capstan motor 4 is controlled so that the running speed of the magnetic tape 2 is equal to that during recording.

On the other hand, at the time of search playback, assuming that the running speed of the magnetic tape 2 is N times that of recording (however, N is an integer of 2 or more), the frequency division ratio of the frequency dividers 6 and 9 is set to N. be done. Therefore, the frequency signal
CFG is frequency-divided by N in a frequency divider 6 and supplied to a frequency-voltage converter 7, and the control signal is also frequency-divided by N in a frequency divider 9 and supplied to a phase comparator 11. As a result, the capstan motor 4 is controlled so that the frequency of the output signal of the frequency divider 6 becomes equal to the frequency of the frequency signal CFG obtained at the running speed of the magnetic tape in standard playback, which is the same as that during recording.
The speed of the magnetic tape 2 is controlled, and the magnetic tape 2 runs at N times the recording speed. Due to this speed control, the phase signal PH has a frequency equal to that of the control signal obtained from the control head 8 at the running speed of the magnetic tape during standard playback, which is also the same as during recording, and this phase signal PH and the reference signal SP The phase of the capstan motor 4 is controlled so that the above phase relationship is maintained.

Through such speed control and phase control of the capstan motor 4, the relationship between the track on the magnetic tape 2 and the scanning locus of the rotary head 3 is maintained constant, and the playback screen changes due to the deviation between this scanning locus and the track. The noise above appears at a certain position.

By the way, in such a magnetic recording/reproducing device, when switching between search playback and standard playback, the capstan motor performs an undesirable transient operation, and the transition to a new playback operation mode is not performed smoothly.
Significant disturbances will occur in the reproduced image. This point will be explained below using the timing chart shown in FIG. In addition, in the same figure, the first
Signals corresponding to the figures are given the same symbols, and A represents the playback operation mode.
"L" represents standard playback mode, and "H" represents search playback mode.

Now, assuming that the magnetic recording and reproducing apparatus is in the standard reproduction mode, as explained earlier, the frequency signals of the output signal of the frequency divider 6 and the frequency of the phase signal PH are the same at the time of recording when the magnetic tape 2 is running at the same speed. The speed and phase of the capstan motor 4 are controlled so that the frequencies of the CFG and the control signal are equal. Here, if the frequency of the phase signal (ie, control signal) PH when the running speed of the magnetic tape 2 is equal to that during recording is _f0 , then the frequency of the reference signal SP is set to _f0 .

Next, when the standard playback mode is switched to the search playback mode at time t ₀ , the frequency division ratios of the frequency dividers 6 and 9 are switched from 1 to N at the same time. Therefore, the rotational speed of the capstan motor 4 attempts to increase N times by speed control, but due to the inertia of the capstan motor 4 and the like, the rotational speed does not suddenly become N times the rotational speed during recording. Therefore, the frequency of the phase signal PH from the frequency divider 9 becomes f ₀ /N, and approaches f ₀ as the capstan motor 4 accelerates.

On the other hand, the frequency of the reference signal SP is always f ₀ ,
In the transient state of the capstan motor 4, the frequencies of the phase signal PH and the reference signal SP are completely different from each other, so the output signal of the phase comparator 11 is generally not the correct phase control voltage. Therefore, since this output signal is supplied to the motor drive circuit 13 via the adder 12, the speed control operation that attempts to accelerate the capstan motor 4 all at once is prevented, and the standard reproduction The transition from mode to search playback mode is not performed smoothly.

When switching from the search playback mode to the standard playback mode (time t ₁ ), the frequency division ratio of the frequency divider 9 is switched from N to 1, so the frequency of the phase signal PH becomes Nf ₀ , and the capstan motor As the capstan motor 4 decelerates, the speed approaches f _0. Therefore, similarly to the above case, the speed control operation that attempts to decelerate the capstan motor 4 all at once is prevented.

In this way, in the conventional magnetic recording and reproducing apparatus described above, at the time of switching between the standard playback mode and the search playback mode, which require a rapid change in the running speed of the magnetic tape, the phase control system performs a rapid and rapid change in the playback operation mode. This had the drawback of interfering with a smooth transition.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
It is an object of the present invention to provide a magnetic recording and reproducing device that can quickly and smoothly shift between a standard reproduction mode and a search reproduction mode.

[Summary of the invention]

In order to achieve this object, the present invention stops phase control of the capstan motor at the same time as switching between standard playback mode and search playback mode, and monitors the running speed of the magnetic tape until the running speed reaches a predetermined level. The feature is that the phase control is restarted after confirming that the speed has been reached.

[Embodiments of the invention]

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

FIG. 3 is a block diagram showing an embodiment of the magnetic recording/reproducing apparatus according to the present invention, in which 14 is a counter control circuit, 15 is a clock pulse generator, 16 is a counter, 17 is a switching signal generator, and 18 is a changeover switch. , 19 is a constant voltage generator, and parts corresponding to those in FIG. 1 are given the same reference numerals, and some explanations will be omitted.

In FIG. 3, a changeover switch 18 and a constant voltage generator 19 are provided in the phase control system of the capstan motor 4, and when changing from standard playback mode to search playback mode and vice versa, , set the changeover switch 18 to the a side (that is, the constant voltage generator 1
9 side) to supply a constant voltage to the adder 12,
The phase control of the capstan motor 4 is cut off. The switching signal SW of the switching switch 18 is generated by the count control circuit 14, the clock pulse generator 15, the counter 16, and the switching signal generator 17, and is converted into an output signal of the frequency divider 6 (hereinafter referred to as rotation detection signal RD).
is formed based on the frequency of The configuration and operation other than the above points are similar to the prior art shown in FIG.

First, the operation of forming the switching signal SW in this embodiment will be explained with reference to FIG. In addition,
In the figure, signals corresponding to those in Figure 3 are given the same symbols, and NC is the count value of the counter 16, and the numerical value is plotted on the vertical axis, and in reality, this count value is expressed in stages. However, for simplicity, it is shown here as increasing linearly.

Now, the rotation detection signal RD obtained from frequency divider 6
is supplied to the counter control circuit 14 to form a count stop signal CS synchronized with the rising edge of the rotation detection signal RD, and a preset signal PR that is slightly delayed from this rising edge and within the pulse period of the count stop signal CS. do. The counter 16 is
The clock pulses from the clock pulse generator 15 are counted, and each time a count stop signal CS is supplied, the count is stopped and the current count value is held, and each time a preset signal PR is supplied, a predetermined value (eg , zero). NC in FIG. 4 shows changes in the count value of the counter 16.

Therefore, the count value when the counter 16 is stopped and held is the rotation detection signal RD.
The rotational speed of the capstan motor 4 can be determined from this count value.

Now, if the magnetic tape is at a normal speed (e.g.
During standard reproduction, the period of the rotation detection signal RD obtained when traveling at the same speed as during recording (hereinafter referred to as normal period) is T ₀ , the period of the clock pulse from the clock pulse generator 15 is T _cc ,
If the cycle of the count stop signal CS is _Ts , the count value _M0 of the counter 16 during one cycle of the rotation detection signal RD at this time is _M0 = _T0 - _Ts / _Tcc , which is different from this in reality. Obtained rotation detection signal RD
From the comparison with the count value M of the counter 16 during one cycle period, it can be determined whether the rotation of the capstan motor 4 is fast or slow. Furthermore, by calculating these count values M ₀ and M, the capstan motor 4
It is also possible to know the extent to which the actual rotational speed has been reduced.

Therefore, with respect to the above count value M ₀ (hereinafter referred to as reference count value), if the count value deviation corresponding to the pull-in range of phase control is △M, then M ₀ +△M≧M≧M ₀ −△M When (1), the speed of the capstan motor 4 is controlled within the pull-in range of phase control.

The switching signal generator 17 receives the counter M from the counter 16, determines whether the counter value M satisfies the above equation (1), and generates the switching signal SW. is the counter value M
When satisfies the above formula (1), the changeover switch 18
When the count value M does not satisfy the above condition (1), the changeover switch is closed to the a side.

Next, the operation of the phase control system of this embodiment using the switching signal SW will be explained using FIG. In this figure, A represents the same reproduction operation mode as in FIG. 2, and signals corresponding to those in FIG. 3 are given the same reference numerals.

Assuming that the magnetic recording and reproducing apparatus is now in the standard reproduction mode (A is "L"), the magnetic tape 2 runs at almost the same speed as during recording, and the frequency division ratio of the frequency divider 9 is 1.
Therefore, the phase signal PH is approximately equal to the frequency of the reference signal SP. Further, the count value M supplied from the counter 16 to the switching signal generator 17 is approximately equal to the reference count value M ₀ and satisfies the above equation (1). At this time, the switching signal SW output by the switching signal generator 17 is "H", the changeover switch 18 is closed to the b side, the phase control voltage from the phase comparator 11 is supplied to the adder 12, and the capstan motor 4
is phase controlled.

Next, when switching to the search playback mode at time t ₀ (A is "H"), the frequency division ratios of frequency dividers 6 and 9 change from 1 to N. As explained above, since the capstan motor 4 does not suddenly reach N times the rotation speed, the rotation detection signal RD
and the phase signal PH decreases in frequency. For this reason, the period of the rotation detection signal RD becomes longer, and the count value M of the counter 16 supplied to the switching signal generator 17 becomes larger, and the above equation (1) is no longer satisfied. Therefore, the switching signal SW becomes "L", the changeover switch 18 is switched to the a side, and the constant voltage generator 1
A constant voltage from 9 is supplied to adder 12 . For this reason, the capstan motor 4 is no longer subjected to phase control, and only speed control is performed to accelerate.
That is, the speed control of the capstan motor 4 is not disturbed by the undesired output voltage from the phase comparator 11, so that the capstan motor 4 is quickly and smoothly accelerated and searched. Approaching the rotational speed required for regeneration mode.

As the capstan motor 4 is accelerated, the period of the rotation detection signal RD becomes shorter, so the count value M supplied to the switching signal generator 17 also becomes smaller gradually. When this count value M finally satisfies the above equation (1), the switching signal SW becomes "H" and the changeover switch 18 is switched to the b side, and the output signal of the phase comparator 11 is transferred to the adder. 12. At this time, the frequency of the phase signal PH is almost equal to the frequency of the reference signal SP,
For this reason, the output signal of the phase comparator 11 can be used as a correct phase control voltage, and the capstan motor 4 is also subjected to phase control.

Next, when the search reproduction mode is switched to the standard reproduction mode at time _t1 , the frequencies of the rotation detection signal RD and the phase signal PH become higher, as explained in the prior art of FIG. For this purpose, the switching signal generator 1
The count value M supplied to 7 becomes smaller and becomes
Equation (1) is no longer satisfied. Therefore, the switching signal SW becomes "L" and the switching switch is switched to the a side.
A constant voltage from constant voltage generator 19 will be supplied to adder 12 . As a result, the phase control of the capstan motor 4 is cut off, and the capstan motor 4 is quickly and smoothly decelerated to approach the rotational speed required for the standard reproduction mode.

As the capstan motor 4 is decelerated, the count value M supplied to the switching signal generator 17 gradually increases until the count value M reaches the value shown in (1) above.
When the equation is satisfied, the switching signal SW becomes "H", the changeover switch 18 is switched to the b side, and the phase control voltage from the phase comparator 11 is supplied to the adder 12, and the capstan motor 4 phase control is resumed.

As described above, since the phase control of the capstan motor 4 is cut off when switching between the standard playback mode and the search playback mode, the rotational speed of the capstan motor 4 can be changed quickly and smoothly.

In the above embodiment, the count value M of the counter 16
The phase control of the capstan motor 4 is turned on or off depending on whether or not satisfies the above formula (1). However, as another embodiment of the present invention, the standard playback mode , after the frequency division ratios of the frequency dividers 6 and 9 change due to switching between search and playback modes, it is determined whether the count value M supplied to the switching signal generator 17 has reached the reference count value _M0 . It is possible to determine whether or not the capstan motor 4 has entered the phase control pull-in range. That is,
For example, when switching from standard playback mode to search playback mode, the count value M supplied to the switching signal generator 17 changes to the reference count value _M0 from the time the frequency division ratio of the frequency divider 6 changes from 1 to N. Until this point is reached, the selector switch 18 is closed to the a side to cut off the phase control of the capstan motor 4.

However, in this case, the center frequency of the speed control system
There are cases where f′ ₀ is deviated and the counter value M cannot be driven up to the reference count value M ₀ .

FIG. 6 is a block diagram showing another embodiment of the magnetic recording/reproducing apparatus according to the present invention which solves the above problem, in which 20 is a frequency-voltage converter control circuit (hereinafter simply referred to as a control circuit); Parts corresponding to those in FIG. 3 are given the same reference numerals.

In FIG. 6, the switching signal generator 17 operates during the period from when the frequency division ratios of the frequency dividers 6 and 9 are switched until the count value M from the counter 16 reaches the reference count value _M0 , as described above. is detected as a transition period, and during this transition period, a switching signal SW for switching the changeover switch 19 to the a side is generated. Further, a control circuit 20 is provided to control the DC operating point of the frequency-voltage converter 7 during the above-mentioned transient period. The configuration and operation other than these points are the same as the embodiment shown in FIG.

Next, the operation of the speed control system of this embodiment will be explained using FIG. 7. In this figure, signals corresponding to those in FIG. 6 are given the same reference numerals.

The frequency-voltage converter 7 is not explained in the embodiment shown in FIG. It consists of means for stopping the voltage increase for a period of time, and means for sampling and holding the voltage during the period when the voltage increase is stopped, and then returning it to the initial value. Of course, although these means have been described as analog circuits, they can also be implemented as digital circuits using counters, latch circuits, and digital-to-analog converters. That is, a count stop signal of a constant width is formed at the rising edge of the phase detection signal RD, a latch signal is formed with a slight delay from this rising edge, and a preset signal is formed with a slight delay from this. The counter counts desired clock pulses, and is stopped at each count stop signal to hold the current count value M'. This count value M' is transferred to a latch circuit as a latch signal and latched therein, and further supplied to a digital-to-analog converter and converted into an analog voltage. After the count value M' is latched, the counter is then preset to the initial value by a preset signal.

Therefore, the count value M' latched by the latch circuit is a value representing the period of the phase detection signal RD, and the analog voltage obtained from the digital-to-analog converter 7 is the speed control voltage VC.

Here, assuming that the frequency-voltage converter 7 has an analog circuit configuration, in FIG. 7, ST is a pulse with a constant width synchronized with the rising edge of the phase detection signal RD, and the frequency - This is a stop pulse that stops the voltage increase of the voltage generator 7. Also, SH is the sample and hold pulse of the voltage within the stop pulse ST period, and RS is the stop pulse
This reset pulse is slightly delayed from the sample and hold pulse SH within the ST period, and resets the voltage of the frequency-voltage converter 7 to its initial value. Furthermore, V is the voltage at the frequency-voltage converter 7 that increases with time.

Therefore, in the frequency-voltage converter 7, the voltage V stops increasing at every stop pulse ST and is held at the value at that time, and is sampled and held by the sample and hold pulse SH. Next, the voltage V returns to its initial value with the reset pulse RS, and when the stop pulse ST disappears, the voltage V begins to increase. The sampled and held voltage represents the period of the phase detection signal RD, and therefore this voltage is equal to the speed control voltage VC
It is.

The control circuit 20 controls the count value M of the counter 16.
The initial value of the frequency-voltage converter 7 is increased or decreased according to the voltage V.
is shifted upward from the solid line a as shown by the dotted line b, or shifted downward as shown by the dashed-dotted line c.

Now, if the count value M of the counter 16 is M≧M ₀ , the voltage V of the frequency-voltage converter 7 is shifted upward, and when M<M ₀ , it is shifted downward. do. Therefore,
When the rotational speed of the capstan motor 4 is lower than the normal speed, the period of the phase detection signal RD becomes longer and M> _M0 , so the voltage V of the frequency-voltage converter 7 is shifted upward, speed control voltage
VC increases from the solid line d to the dotted line e, and the capstan motor 4 is accelerated. Conversely, when the rotational speed of the capstan motor 4 is higher than the normal speed, the voltage V of the frequency-voltage converter 7 is shifted downward, and the speed control voltage VC decreases from the solid line d to the dashed-dotted line f. Capstan motor 4 is decelerated.

However, the rotational speed of the capstan motor 4 is driven until the period of the phase detection signal RD slightly fluctuates in the vicinity of the normal period _T0 , and this operation is affected by the amount of offset in the control system of the capstan motor 4. It will be done regardless. Therefore, as long as the speed control operation described above is performed, even if the rotational speed of the capstan motor 4 significantly deviates from the normal speed when switching between the search playback mode and the standard playback mode, the phase detection signal will always be output. The speed of the capstan motor 4 is increased until the period of RD slightly fluctuates from the normal period _T0 .

Next, the overall operation of this embodiment will be briefly explained.

When switching between the standard playback mode and the search playback mode, if the frequency division ratios of the frequency dividers 6 and 9 change, the capstan motor 4 does not respond immediately due to its own inertia. The rotational speed becomes significantly deviated from the normal rotational speed corresponding to the set reproduction operation mode. This state is detected by the counter 16, and the changeover switch 17 is operated to change the changeover switch 18 from the b side to the a side. Therefore, a constant voltage is supplied from the constant voltage generator 19 to the adder 12, and the phase control system is cut off.

Along with this, the control circuit 20 controls the counter 16
The initial value of the frequency-voltage converter 7 is added in accordance with the count value M of , the DC offset is canceled, and the voltage increase characteristic is shifted in the vertical direction. As a result, the capstan motor 4 receives the phase detection signal
The rotational speed is quickly and smoothly accelerated or decelerated until the period of RD slightly fluctuates around the normal period T ₀ to drive up the rotational speed.

Therefore, since the period of the phase detection signal RD always reaches the regular period _T0 , this is detected by the count 16 and the switching signal detector 17, and the changeover switch 18 is switched to the b side to start the phase control operation. At the same time, the voltage shift operation of the frequency-voltage converter 7 is stopped, and the speed control operation is performed at that operating point.

In this way, the switching between the standard playback mode and the search playback mode is performed quickly and smoothly, but in this embodiment, instead of detecting that the period of the phase detection signal RD has reached the regular period _T0 , , a counter counts the number of minute fluctuations around the regular period T ₀ , and when the count value reaches a predetermined number, the changeover switch 18 is changed from the a side to the b side.
A similar effect can be obtained by switching to the side.

The embodiments of the present invention have been described above, but it goes without saying that the present invention is applicable not only to switching between the standard playback mode and search playback mode, but also to switching between arbitrary playback operation modes. Further, in the above embodiment, the phase signal PH is formed from the control signal, but it is also possible to generate a pulse from the capstan motor 4 every rotation and form the phase signal PH from this pulse. good.

〔Effect of the invention〕

As explained above, according to the present invention, when switching the regeneration operation mode, it is possible to quickly and smoothly shift the rotation speed of the capstan motor to a rotation speed suitable for the newly set regeneration operation mode. , it is possible to significantly reduce disturbances in reproduced images, and it is possible to provide a magnetic recording and reproducing device with excellent functions, except for the drawbacks of the above-mentioned prior art.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional magnetic recording/reproducing device, FIG. 2 is a timing chart showing the operation of the phase control system shown in FIG. 1 when switching between standard playback mode and search playback mode, and FIG. A block diagram showing an embodiment of a magnetic recording and reproducing device according to the present invention,
FIG. 4 is a timing chart showing the switching signal generation operation in FIG. 3, FIG. 5 is a timing chart showing the operation of the phase control system in FIG. 3 when switching between standard playback mode and search playback mode, and FIG. 6 is a timing chart showing the operation of the phase control system in FIG. FIG. 7 is a block diagram showing another embodiment of the magnetic recording/reproducing apparatus according to the invention. FIG. 7 is a timing chart showing the operation of the speed control system shown in FIG. 2... Magnetic tape, 4... Capstan motor, 6... Frequency divider, 7... Frequency-voltage converter,
9... Frequency divider, 10... Reference signal generator, 11...
Phase comparator, 12... Adder, 13... Motor drive circuit, 14... Counter control circuit, 15... Clock pulse generator, 16... Counter, 17...
...Switching signal generator, 18...Switching switch, 19
... Constant voltage generator, 20 ... Frequency-voltage control circuit.

Claims (1)

[Claims] 1. The rotation of the capstan motor is controlled by supplying a frequency signal having a frequency corresponding to the rotation frequency of the capstan motor to a frequency-voltage converter via a first frequency divider. Generating a speed control voltage for controlling the speed, and supplying a signal obtained by frequency-dividing a phase signal representing the rotational phase of the capstan motor by a second frequency divider and a reference signal to a phase comparator. generates a phase control voltage that controls the rotational phase of the capstan motor, switches the frequency division ratios of the first and second frequency dividers for each of a plurality of regeneration operation modes, and controls the rotational phase of the capstan motor. A magnetic recording/reproducing device configured to control rotational speed and rotational phase, comprising: a counter that repeatedly counts a clock signal every cycle of an output signal of the first frequency divider; and an output of the frequency divider of the counter. A switching signal generator that generates a switching signal according to a count value of the period of the signal, and a switching switch that switches the phase control voltage to a predetermined voltage based on the switching signal, Frequency fluctuation periods of the frequency divider output signals of the first and second frequency dividers accompanying switching of the frequency division ratios of the first and second frequency dividers, and rotational phase control of the capstan motor. 1. A magnetic recording and reproducing device characterized in that it is configured to be able to cut off. 2. The switching signal generator causes the switching switch to switch to the predetermined range when the count value of the counter during the period of the frequency divider output signal of the first frequency divider is outside a preset range. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein a switching signal for switching to the voltage side is generated. 3. The switching signal generator is configured such that after switching the frequency division ratio of the first frequency divider, a count value of the counter during a cycle period of the frequency divider output signal of the first frequency divider is set in advance. 2. The magnetic recording/reproducing apparatus according to claim 1, wherein a switching signal is generated for switching the changeover switch to the predetermined voltage side during a transient period until the predetermined voltage level is reached.