JPH0510241Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a magnetic disk recording/reproducing device.

[Summary of the idea]

The present invention provides a magnetic disk recording/reproducing device in which a recording signal and a direct current are supplied to a recording amplifier circuit to which a magnetic head is connected, and an output signal current and an idling current are caused to flow through the recording amplifier circuit.
When switching between recording and playback modes, a correction current is generated to slow down the change in idling current.
By supplying it to the recording amplification circuit,
To prevent noise from being recorded in the magnetic head due to an instantaneous current flowing through the magnetic head due to a sudden change in the idling current when switching between recording and playback modes, thereby preventing damage to previously recorded signals. It has been made possible to do so.

[Conventional technology]

In conventional magnetic disk recording and reproducing devices, the voltage -
An information signal such as a video signal (still image signal) is supplied to a current conversion circuit, and the signal current and DC current obtained from this voltage-current conversion circuit are supplied to a recording amplifier circuit (current amplifier circuit) to perform this recording. Make the output signal current and idling current flow through the amplifier circuit,
Information signals were recorded on the magnetic disk by a magnetic head connected to this recording amplifier circuit.

[Problem that the invention attempts to solve]

By the way, in such a conventional magnetic disk recording/reproducing device, when switching from recording mode to reproduction mode or from reproduction mode to recording mode, the idling current flowing through the recording amplifier circuit changes from a certain value to 0 or from 0 to a certain value. changes rapidly.
Therefore, when switching between the recording and reproducing modes, a current momentarily flows through the magnetic head, and noise based on this is recorded on the magnetic disk, potentially damaging the information signals recorded thereon.

In view of this, the present invention has been proposed in which an instantaneous current flows through the magnetic head due to a sudden change in the idling current when switching between recording and reproducing modes, and based on this, noise is recorded in the magnetic head, and noise is recorded in the magnetic head. The present invention attempts to propose a magnetic disk recording and reproducing apparatus that can avoid damaging recorded signals.

[Problem that the invention attempts to solve]

The present invention provides a magnetic disk recording/reproducing apparatus in which a recording signal and a direct current are supplied to a recording amplifier circuit 5 to which a magnetic head 7 is connected, and an output signal current and an idling current are caused to flow through the recording amplifier circuit 5. The present invention is characterized in that a correction current generation circuit 8 is provided which generates a correction current that slows down the change in the idling current and supplies it to the recording amplifier circuit 5 when switching the reproduction mode.

[Effect]

According to the present invention, when switching between recording and reproduction modes, a correction current is supplied from the correction current generation circuit 8 to the recording amplifier circuit 5, and the change in the idling current at that time is corrected, and the current is instantaneously applied to the magnetic head. flow is avoided.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to FIG. 1 is a video signal (still image signal)
The information signal from this signal source is supplied to the voltage-current conversion circuit 2. This voltage-
The recording signal current is and the DC current _i0 from the current conversion circuit 2 are supplied to the recording amplifier circuit (current amplifier circuit) 5. This recording amplifier circuit 5 has an output signal current Is
and an idling current I ₀ is applied. A magnetic head 7 is connected to the recording amplifier circuit 5. The magnetic head 7 records information signals (still image signals) on a magnetic disk (not shown) so as to form concentric tracks, for example.

8 is a correction current generation circuit, which is the time constant circuit 3
and a current output circuit 4 to which the output of the time constant circuit 3 is supplied. This correction current generation circuit 8 generates a correction current when switching between recording and playback modes, supplies this correction current to the recording amplifier circuit 5, and supplies the DC current from the voltage-current conversion circuit 2 to the recording amplifier circuit 5. Correct so that the change in current i ₀ becomes slower.

Next, the specific configuration of each circuit will be explained. First, the voltage-current conversion circuit 2 will be explained. The emitters of the transistor 12 and the diode-connected transistor 13 constituting the current mirror circuit 11 are connected to the power supply through an on/off switch SW that is turned on during recording and turned off during playback.
Connected to B. A signal source 1 is connected between the emitter of the transistor 13 and ground. Collectors of transistors 12 and 13 constituting current mirror circuit 11 are respectively connected to emitters of diode-connected transistor 15 and transistor 16 constituting current mirror circuit 14. Transistor 1 constituting current mirror circuit 14
The collectors of transistors 5 and 16 are connected to the collectors of constant current transistors 17 and 18, respectively. A base bias voltage is applied to the bases of these transistors 17 and 18 by a bias power supply 19.

Next, the recording amplifier circuit 5 will be explained. The collector of transistor 37 is connected to power supply +B, and its emitter is grounded through resistor 38. The emitter of transistor 37 is connected to the base of transistor 39. The collector of the transistor 39 is connected to the power supply +B through the primary coil 6a of the transformer 6. A coil of the magnetic head 7 is connected to the secondary coil 6b of the transformer 6. The emitter of the transistor 39 is connected to the collector of a diode-connected transistor 35 forming the current mirror circuit 33. The emitters of the transistor 34 and the diode-connected transistor 35 constituting the current mirror circuit 33 are grounded. The base of the transistor 37 is
It is connected to the collector of the transistor 34 through a pair of diodes 36 connected in series. The transistor 16 of the voltage-current conversion circuit 2,
18 is connected to the base of the transistor 37 of the recording amplifier circuit 5.

Next, the correction current generation circuit 8 will be explained. This is composed of a time constant circuit 3 and a current output circuit 4 to which the output of the time constant circuit 3 is supplied. First, the time constant circuit 3 will be explained. An input terminal 23 to which a step signal generated before and after the switching of the recording and reproducing modes is connected to the transistor 22a of the differential amplifier 21 through an integrating circuit 24 consisting of resistors 25, 27 and a capacitor 26. connected to the base. That is, the input terminal 23 is connected to the transistor 2 through the resistor 25.
2a, and its base is grounded through a parallel circuit of a capacitor 26 and a resistor 27. The emitters of the transistors 22a and 22b constituting the differential amplifier 21 are grounded through the collector and emitter of the constant current transistor 20. A base bias voltage is applied to the base of the transistor 20 by the bias power supply 19 described above. The collector of transistor 22b is connected to power supply +B. A series circuit of resistors R ₁ and R ₂ is connected between the power supply +B and ground, and the reference voltage obtained at the midpoint of the connection is applied to the transistor 22.
applied to the base of b.

Next, the current output circuit 4 will be explained. The respective emitters of diode-connected transistor 29 and transistor 30 constituting current mirror circuit 28 are connected to power supply +B. transistor 2
The collector of transistor 22a is connected to the collector of transistor 22a. The collector of the transistor 30 is
It is connected to the collector of the diode-connected transistor 31 that constitutes the current mirror circuit 40 .
The collector of the transistor 32 constituting the current mirror circuit 40 is connected to the base of the transistor 37, and its emitter is grounded.

Next, the operation of this magnetic disk recording/reproducing apparatus will be explained. When switching from recording mode to playback mode, the switch SW that was on until now is turned off. Thus, from the voltage-current conversion circuit 2,
The direct current i ₀ supplied to the recording amplifier circuit 5 becomes zero immediately together with the recording signal current is. At this time, the input terminal 23 of the time constant circuit 3 is supplied with a step signal 23a that instantly reaches a positive predetermined level from 0. This step signal 23a is integrated by an integrating circuit 24, and the integrated voltage is supplied to the base of transistor 22a. As a result, the collector current of the transistor 29 of the current mirror circuit 28 changes, and this current change is transmitted to the current mirror circuit 40. Then, a current as shown in FIG. 2A is applied to the collector of the transistor 32.
id flows, and this current id flows out of the base of transistor 37. Therefore, the transistor 39
At the time of recording, the output signal current Is and the idling current _I0 were flowing through the collector of the A direct current flows that gradually decreases from I (equal to ₀ value).
Therefore, no instantaneous current flows through the magnetic head 7 when switching between the recording and reproducing modes, and there is no possibility that the recorded signals on the magnetic disk will be damaged.

Furthermore, when switching from the recording mode to the playback mode, the switch SW, which has been off until now, is turned on. In this way, the DC current i ₀ supplied from the voltage-current conversion circuit 2 to the recording amplifier circuit 5 immediately changes from 0 to a certain value. At this time, the input terminal 23 of the time constant circuit 3 is supplied with a step signal that is the opposite of the step signal 23a and instantly changes from a positive predetermined level to 0. This step signal is integrated by an integrating circuit 24, and the integrated voltage is supplied to the base of transistor 22a. As a result, the collector current of the transistor 29 of the current mirror circuit 28 changes, and this current change is transmitted to the current mirror circuit 40. A current having a characteristic opposite to that of the current id shown in FIG. 2A flows into the collector of the transistor 32, and this current flows into the base of the transistor 37. Therefore, although no current flows through the collector of the transistor 39 during playback, the output signal current Is and the idling current _I0 flow through it, and in addition to this, the current Id shown in FIG. 2B. A direct current with opposite characteristics flows. Therefore, no instantaneous current flows through the magnetic head 7 when switching between the reproduction and recording modes, and there is no possibility that the recorded signals on the magnetic disk will be damaged.

[Effect of idea]

According to the present invention described above, an instantaneous current flows through the magnetic head due to a sudden change in the idling current when switching between the recording and reproducing modes, and based on this, noise is recorded in the magnetic head, and noise is recorded in the magnetic head. It is possible to obtain a magnetic disk recording/reproducing device that can avoid damaging recorded signals.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
The figure is a characteristic curve diagram for explanation. 1 is a signal source, 2 is a voltage-current conversion circuit, 3 is a time constant circuit, 4 is a current output circuit, 5 is a recording amplifier circuit, 7 is a magnetic head, and 8 is a correction current generation circuit.

Claims (1)

[Claims for Utility Model Registration] In a magnetic disk recording/reproducing device which supplies a recording signal and a direct current to a recording amplifier circuit to which a magnetic head is connected, and causes an output signal current and an idling current to flow through the recording amplifier circuit, A magnetic disk recording/reproducing apparatus characterized in that a correction current generation circuit is provided which generates a correction current that slows down the change in the idling current when switching between recording and reproduction modes, and supplies the correction current to the recording amplifier circuit.