JPH0792895B2 - Recording / playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a recording / reproducing apparatus including a recording / reproducing head.

[Prior Art] FIG. 4 is a circuit diagram showing an example of a conventionally known recording / reproducing apparatus. In this figure, HD is a recording / playback head, A ₁ is a recording amplifier (hereinafter referred to as recording amplifier), and A _{2 is}
Is a regenerative amplifier (hereinafter referred to as regenerative amplifier), SW ₁ and S
W ₂ is a switch and C ₁ and C ₂ are coupling capacitors.

In the circuit shown in FIG. 4, the switch SW ₂ is closed (hereinafter referred to as ON) at the time of recording, and the switch SW ₂ is closed.
₁ is set to the open state (hereinafter referred to as OFF). During playback, switch SW ₁ is ON and switch S
W ₂ is set to OFF. Furthermore, recording amplifier A ₁ during playback
When is operating, noise is mixed in the reproduced signal and the S / N is deteriorated. Therefore, the recording amplifier A ₁ is turned off during reproduction.

Now, the operation when the circuit shown in FIG. 4 transits from the reproducing state to the recording state will be described.

During playback, power of recording amplifier A ₁ is OFF, switch SW ₁ is ON
Therefore, there is no potential difference between both terminals of the capacitor C ₁ . However, when the recording state is reached, the power of the recording amplifier A ₁ is turned on, the switch SW ₁ is turned off, and the switch SW ₂ is turned on, so that a potential difference is generated between both terminals of the capacitor C ₁ . As a result, the transient current accompanying the charging of the capacitor C ₁ flows through the head HD and the switch SW ₂ .

On the contrary, when the circuit shown in FIG. 4 changes from the recording state to the reproducing state, the transient current accompanying the discharge of the electric charge stored in the capacitor C ₁ flows into the head HD.

[Problems to be Solved by the Invention] As described above, in the conventional device having the recording / reproducing head, a transient current flows through the head when the recording / reproducing operation is switched. There were defects.
As a result, there arises a disadvantage that a signal already recorded on the recording medium is erased or noise is recorded in an unrecorded portion.

Therefore, in view of the above point, an object of the present invention is to provide a recording / reproducing apparatus configured so that a transient current does not flow in the recording / reproducing head even when the recording / reproducing operation is switched.

[Means for Solving Problems] In order to achieve such an object, a recording / reproducing apparatus of the present invention includes a recording / reproducing head, a recording amplifier for amplifying a recording signal supplied to the head, the head, and the head. A coupling capacitor for coupling with a recording amplifier, a first switch for grounding the terminal on the coupling capacitor side of the head during reproduction, and a second switch for grounding the other terminal of the head during recording.
A recording / reproducing apparatus including a switch, for closing the first switch at a first timing in response to a control signal for instructing switching of the operating state of the apparatus from a recording operation to a reproducing operation. A first switch control signal is generated, a second switch control signal for opening the second switch is generated at a second timing after the first timing, and the second switch control signal is generated after the second timing. And a timing control circuit for generating a recording amplifier operation control signal for stopping the operation of the recording amplifier at the third timing.

Further, the recording / reproducing apparatus of the present invention comprises a recording / reproducing head, a recording amplifier for amplifying a recording signal supplied to the head, a coupling capacitor for coupling the head and the recording amplifier, and the head of the head. In a recording / reproducing apparatus having a first switch for grounding a terminal on the coupling capacitor side during reproduction and a second switch for grounding the other terminal of the head during recording, the operating state of the apparatus is switched from a reproducing operation to a recording operation. Generating a recording amplifier operation control signal for starting the operation of the recording amplifier at a first timing in response to a control signal for instructing
A second switch control signal for closing the second switch is generated at a second timing after the first timing, and the first switch is generated at a third timing after the second timing. It comprises a timing control circuit for generating a first switch control signal for opening the switch.

[Operation] By configuring as described above, the transient current generated when the operation state of the device is switched from the recording operation to the reproducing operation or when the reproducing operation is switched from the recording operation to the Since the terminal on the coupling capacitor side for coupling the recording / reproducing head and the recording amplifier can be made to flow to the ground point via the first switch for grounding at the time of reproduction, recording or reproduction by an unnecessary transient current is performed. It is possible to prevent an adverse effect on the signal that is generated.

[Examples] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 is a block diagram showing an entire embodiment of the present invention. The switching timings of the switches SW ₁ and SW ₂ shown in this figure are as described with reference to FIG. That is,
During recording, the switch SW ₁ is turned off and the switch SW ₂ is turned on, so that the recording current flows from the recording amplifier A ₁ to the head HD. Further, during reproduction, the switch SW ₁ is turned on and the switch SW ₂ is turned off, and the reproduction signal obtained from the head HD is sent to the reproduction amplifier A ₂ .

FIG. 2 is a detailed configuration block diagram of the timing control circuit CNT shown in FIG. That is, this figure shows the switch
In addition to controlling ON / OFF of SW ₁ and SW ₂ , it is a circuit configuration for controlling ON / OFF of the power supply of the recording amplifier A ₁ . 3, 4, 5, 6, and 7 shown in the figure are inverters each composed of CMOS or the like.

FIG. 3 is a waveform diagram for explaining the circuit operation of FIG.
The waveforms (a) to (h) in FIG. 3 correspond to the signals (a) to (h) in FIG. 2, respectively.

Next, the operation of this embodiment will be described with reference to FIGS.

First, the operation when switching from the reproduction state to the recording state will be described.

A control signal a for switching between a recording state and a reproducing state is externally supplied to the inverter 3 shown in FIG. In the reproducing state, the control signal a supplied from the outside is at low level. At this time, the output signal b of the inverter 3 becomes high level, the input signal c of the inverter 4 becomes high level, and the output signal d of the inverter 4 becomes low level. The input signal e of the inverter 5 is high level, the output signal f of the inverter 5 is low level, the input signal g of the inverter 7 is low level, and the output signal h of the inverter 7 is high level.

Here, the power of the recording amplifier A ₁ is the signal d, and the switch SW ₁ is the signal d.
It is assumed that the h and the switch SW ₂ are ON / OFF controlled by the signal f (ON when these signals are high level, OFF when these signals are low level).

Next, when the external control signal a switches to the high level (that is, when the operation mode switches from the reproducing state to the recording state), the signals b and c immediately switch from the high level to the low level, and the signal d. Immediately changes from low level to high level. This is a diode D ₁
This is because the electric charge stored in the capacitor C ₃ is discharged via the. This timing is t ₁ (see FIG. 3).

Further, the input signal e of the inverter 5 tries to change from the high level to the low level, but it takes time to discharge the electric charge accumulated in the capacitor C ₄ through the resistor R ₂ , so that FIG. As shown in, there is a delay in the fall of the waveform. As a result, the output signal f of the inverter 5 is changed from the low level to the high level at a timing t ₂ delayed than t _1.

Next, the input signal g of the inverter 7 tries to change from the low level to the high level, but it takes time to charge the capacitor C ₅ via the resistor R _4, and therefore, as shown in FIG. There is a delay in rising. As a result, the output signal h of the inverter 7, a transition from the high level to the low level at a timing t ₃ when later than t _1. Where R ₂ ×
By setting C ₄ <R ₄ × C ₅ , the timing t ₃
It can be set after t ₂ .

As described above, when switching from the playback state to the recording state, the amplifier A ₁ recorded at the timing of t ₁ is turned ON, then
The switch SW ₂ turns on at the timing of t ₂ , and then the switch SW ₁ turns off at the timing of t ₃ . As a result, recording amplifier
The transient current generated by charging the capacitor C ₁ when A ₁ is turned on flows to the ground point through the switch SW _{1 and} does not flow to the head HD. Also, when the switch SW ₂ is turned on when the capacitor C ₁ is sufficiently charged and t ₂ and t ₃ are set so that the switch SW ₁ is turned off after that, the transient current due to the switching of these switches causes the head current. It never flows in HD.

Next, the operation when the recording / reproducing apparatus is switched from the recording state to the reproducing state will be described.

In the recording state, the control signal a is high level,
The signal b is low level, the signal c is low level, the signal d is high level, the signal e is low level, the signal f is high level,
The signal g is at high level and the signal h is at low level. In such a state, when the control signal a supplied from the outside changes from the high level to the low level at the timing of t ₄ , immediately the signal b becomes the high level and the signal g.
Changes to low level and the signal h changes to high level. This is because the electric charge stored in the capacitor C ₅ is discharged via the diode D ₃ .

However, the input signal c of the inverter 4 has a waveform as shown in FIG. 3 because it takes time to charge the capacitor C ₃ via the resistor R ₁ . Therefore, the output signal d of the inverter 4 returns from the high level to the low level at the timing of t ₆ .

The input signal e of the inverter 5 also has a waveform as shown in FIG. 3 because it takes time to charge the capacitor C ₄ through the resistors R ₂ and R ₃ . Therefore, the output signal f from the inverter 5 returns from high level to low level at the timing of t ₅ . Where R ₁ × C ₃ > (R ₂ + R ₃ ) × C ₄
It is possible to satisfy t ₄ <t ₅ <t ₆ by presetting such that

As described above, when switching from the recording state to the reproducing state, first, the switch SW ₁ is turned on at the timing of t ₄ , the switch SW ₂ is turned off at the timing of t ₅ , and the recording amplifier is further turned on at the timing of t _6. The power of A ₁ is turned off. as a result,
The transient current generated by the discharge of the capacitor C ₁ when the power of the recording amplifier A ₁ is turned off flows into the ground point via the switch SW _1, and therefore does not flow into the head HD. Also capacitors
The DC potential of the head side input terminal at C ₂ is
_Since switch SW ₂ turns off after ₁ turns on, it is always grounded. Thus, rather than that the charge stored in the capacitor C ₂ is discharged, the capacitor C ₂ to the head HD
No current flows due to the charging and discharging of.

[Effects of the Invention] As described above, according to the present invention, the transient current generated due to the switching between the recording operation and the reproducing operation is bypassed, and an extra noise current is not passed through the head. Thus, it is possible to obtain a recording / reproducing apparatus capable of appropriately switching the.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a detailed block diagram of the timing control circuit shown in FIG. 1, and FIG. 3 is an operation of FIG. FIG. 4 is a waveform diagram showing a conventional technique. A ₁ ...... Recording amplifier, A ₂ ...... Reproducing amplifier, HD ...... Recording and reproducing head, 3 to 7 ...... Inverter, SW ₁ , SW ₂ ...... Switch, CNT ...... Timing control circuit.

Claims (2)

[Claims] 1. A recording / reproducing head, a recording amplifier for amplifying a recording signal supplied to the head, a coupling capacitor for coupling the head and the recording amplifier, and a terminal on the coupling capacitor side of the head. In a recording / reproducing apparatus having a first switch grounded during reproduction and a second switch grounding the other terminal of the head during recording, an operation state of the apparatus is instructed to switch from a recording operation to a reproduction operation. In response to the control signal, a first switch control signal for closing the first switch is generated at a first timing, and the second switch is turned on at a second timing after the first timing. To generate a second switch control signal for opening and to stop the operation of the recording amplifier at a third timing after the second timing. Recording and reproducing apparatus, characterized in that it comprises a timing control circuit for generating a recording amplifier operation control signal. 2. A recording / reproducing head, a recording amplifier for amplifying a recording signal supplied to the head, a coupling capacitor for coupling the head and the recording amplifier, and a terminal on the coupling capacitor side of the head. A recording / reproducing apparatus comprising a first switch grounded at the time of reproduction and a second switch grounding the other terminal of the head at the time of recording, for instructing switching of the operation state of the apparatus from the reproduction operation to the recording operation. In response to the control signal, a recording amplifier operation control signal for starting the operation of the recording amplifier is generated at a first timing, and the second switch is turned on at a second timing after the first timing. A second switch control signal for closing is generated, and the first switch is opened at a third timing after the second timing. Recording reproducing apparatus according to claim first that comprises a timing control circuit for generating a switch control signal.