JPH0775044B2 - Damping circuit when writing to magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a magnetic head write damping circuit applied to a magnetic head circuit of an FDD (floppy disk drive) or the like.

(B) Conventional Technology When writing and reading with one magnetic head, it is necessary to make the damping characteristics different from each other. In general, it is necessary to increase the magnetic energy in writing in order to improve the magnetization reversal of the magnetic medium as compared with in reading, and therefore the damping ability to absorb the energy stored in the coil must also be increased. In the past, resistors were used to perform this writing damping and reading damping.

FIG. 4 shows a conventional magnetic head circuit used in a magnetic recording medium having a magnetic recording surface on the front and back sides.

The magnetic head is composed of a coil in which a power source is connected to the center tap and a damping resistor is connected between both terminals. A indicates the front side (SIDE0) magnetic head and B indicates the back side (SIDE0)
IDE1) magnetic head is shown. The SIDE0 power supply circuit 1 and the SIDE1 power supply circuit 2 are connected to the center taps of the magnetic heads A and B, respectively, and the power supply voltage V1 is supplied to the magnetic head of SIDE0 or SIDE1 by selectively driving this circuit. Is supplied. Transistors Q1 and Q2 forming a head selection switch element are connected to both terminals of the magnetic heads A and B (both terminals of the coil) via diodes D1 to D4.
Further, a constant current source I _w is connected. Outputs from both terminals of the magnetic heads A and B are further input to amplifiers 3 and 4, where they are amplified and output to an external circuit. The transistors Q1 and Q2 are on / off controlled by a head selection signal φ, which is a write control signal, and the write coil L00 of the magnetic head A,
Either L01 or one of the write coils L10 and L11 of the magnetic head B is driven. The magnetization direction of coils L01 and L11 is 1 with respect to the magnetization direction of coils L00 and L10.
The direction is reversed by 80 degrees.

A resistor is used for the damping circuit when writing or reading.
R1 to R3 are used. The resistors R2 and R3 form a damping resistor during reading, and the resistor R1 forms a damping resistor during writing. Damping resistor for reading
R2 and R3 are directly connected to both terminals of the magnetic heads A and B respectively, and the damping resistor R1 during writing is the diode D1 and D
2 and the above resistors R2 and R3 in parallel via diodes D3 and D4.
It is connected to the. The diodes D1 to D4 are
It serves to determine which side of resistor R1 or resistor R2 is connected in parallel. SID when writing SIDE0 side
Since E0 power supply circuit 1 is turned on, diodes D1 and D2
Turns on and the resistor R1 enters the SIDE0 side. That is, resistance R
1 and resistor R2 are connected in parallel. Similarly, when the SIDE1 power supply circuit 2 is turned on, the resistor R1 is connected in parallel with the resistor R3.

The damping resistance R1 at the time of writing is set to have a considerably smaller resistance value than the damping resistance R2 at the time of reading. The reason for this is that, at the time of writing, it is necessary to increase the write current in order to improve the magnetization reversal of the medium, but since the stored energy of the magnetic head increases correspondingly, it is necessary to enhance the ability of the damping circuit to consume that energy. Because there is. Normally, the ratio of the resistance values of the resistors R1 and R2 is set to 1:10 or more.

With the above configuration, at the time of writing, the SIDE0 power supply circuit 1 or the SIDE1 power supply circuit 2 is turned on, and writing is performed with the resistor R1 connected in parallel to either the resistor R2 or the resistor R3. In this case, when the head selection signal φ is "H", the coil L00 or L10 serves as the selection side coil and data is written by these coils.
In case of, L01 or L11 becomes the selection side coil and data is written by these coils.

(C) Problems to be Solved by the Invention However, in the above conventional circuit, the write current is not selected because the impedance of the coil becomes high when the head selection switch element is switched, that is, when φ is switched. There is a drawback that the set write current does not flow to the selection side coil and the rising of the current flowing to the selection side coil is delayed because the set write current does not flow to the selection side coil. FIG. 5 shows this state. The figure shows the waveform of the main part on the SIDE0 side. In the figure, d1 to d3 represent the switching timings of φ and φ. In d1 and d3, L00 is the selection side coil and L01 is the non-selection side coil. At the time of switching between d1 and d3, the voltage waveform at the point a sharply falls as shown in the figure, and the voltage waveform at the point b, on the contrary, sharply rises. However, at the time of this switching, the current flowing into the coil has a large high-frequency component, so the coil L00 on the selection side has a high impedance (of course, the coil L01 on the non-selection side is also in a high impedance state), and during writing Since the damping resistance of is a parallel combination of the low resistance R1 and the high resistance R2, the current i ₃ flowing from the SIDE0 power supply circuit 1 into the coil is i _{2 in} FIG.
As shown by, it also flows into the non-selected side coil L01.
Therefore, the waveform of the current i ₁ flowing at the point a is q in the figure.
As shown in, the rise will be slow.

As described above, in the conventional circuit, the rising of the waveform of the current flowing through the coil on the selection side is delayed when writing the data, which deteriorates the magnetization reversal characteristic on the magnetic medium. However, there is a drawback in that the magnetic storage device cannot be increased in capacity and the increase in capacity of the entire magnetic storage device is hindered.

An object of the present invention is to solve the above-mentioned drawbacks and to increase the capacity of a magnetic storage device by configuring a damping circuit at the time of writing by a current drawing means capable of selectively operating.

(D) Means for Solving the Problems The present invention relates to a magnetic head including a coil whose power source is connected to a midpoint tap, and a write control signal connected between each of both terminals of the coil and a write current control circuit. In a magnetic head circuit including a head selection switch element that is on / off controlled based on the above, write current drawing means for drawing a part of the write current from the coil is provided in parallel with the write current control circuit at both terminals of the coil. And a timer circuit for directly outputting the damping effective signal for operating the write current drawing means from the time when a certain time t1 has passed after the on / off switching of the head selection switch element until a certain time t2 has passed. It is characterized by having.

FIG. 1 is a block diagram of a magnetic head circuit using a damping circuit according to the present invention. This circuit shows only the SIDE0 side circuit.

The magnetic head circuit shown in FIG. 1 includes a head selection switch element 10, a head selection signal forming circuit 11, and a delay circuit 12.
And a timer circuit 13, a write current drawing circuit 14, and a constant current source of I _w which is a write current control means.

The head selection element 10 is a transistor Q1, Q shown in FIG.
It is composed of switching elements such as 2. The head selection signal forming circuit 11 uses write data ▲ ▼ supplied from an external device.
To form a head selection signal φ, which is a write control signal. The delay circuit 12 forms a timing signal delayed by a predetermined time t1 from the rising timing of the head selection signal φ. The timer circuit 13 generates a damping effective signal for a fixed time t2 from the generation timing of the delay signal and outputs it to the write current drawing circuit 14. The write current drawing circuit 14 draws a part of the write current flowing through the coil of the magnetic head as the constant current I _D while the damping effective signal is generated.

(E) Action In the above magnetic head circuit, since neither the head selection signal φ, is output during reading, the high resistance R2 acts as a damping resistor during reading, and the signal read by the coil is read. It is output as data ▲ ▼. On the other hand, when writing, write data ▲ ▼
Is output to the head selection signal forming circuit 11 to form a head selection signal φ, which is output to the head selection switch element 10. Further, a delay signal delayed by a fixed time t1 from the rising timing of the head selection signal φ is output to the tire 13, and the timer 13 outputs a fixed time t2 from the delayed timing.
Only the damping effective signal is written and the current drawing circuit 14
Output to. Therefore, the write current drawing circuit 14 does not operate in the time t1 from the moment when φ, rises, and the damping resistor R2 at the time of reading is also high resistance, so that the current supplied from the power source is almost constant even if the coil impedance is high. Flows into the coil on the selection side. For example, if the head selection signal φ rises, most of the current flows into L00 at the time t1 from the rising timing, and no current flows in the circuit of L01 and the resistor R2. That is, in the figure, current i ₁ ≈ current i ₃ . Also, at time t2 when the damping effective signal is output after the time t1 has elapsed,
Since the write current drawing circuit 14 operates, consumption of energy stored in the coil during this time, that is, a damping action is performed.

In the above-described operation, when the head selection signal φ is switched, the current can be supplied to almost only the selected coil, so that the rising characteristic of the write current flowing in the selected coil can be improved. Further, since the current is drawn by the write current drawing circuit 14 after the lapse of time t1, it is possible to reliably perform the damping action for absorbing the energy stored in the coil. Furthermore, when the magnetic head circuit is provided on both the SIDE0 side and the SIDE1 side, the diodes D1 to D4 that switch the high resistance for damping at the time of writing as in the conventional circuit are unnecessary,
The power supply voltage can be lowered by the amount of voltage drop due to the diode, and the power supply voltage can be lowered.

(F) Effects of the Invention As described above, according to the present invention, the head selection signal φ,
For prohibiting the operation of the write current drawing means that performs a damping action at the time of switching, and operating the write current drawing means at a constant time t2 after the time t1 has elapsed Since the low resistance is not used, almost all the current supplied from the power source can flow into the coil on the selection side at time t1, and the damping action can be surely performed. Therefore, the rising characteristics of the write current can be improved, and the write frequency can be increased, so that there is an advantage that the storage density is increased and the capacity of the magnetic storage device can be increased.

(G) Embodiment FIG. 2 shows a circuit diagram of a magnetic head circuit according to an embodiment of the present invention.

In this embodiment, the head selection switch element shown in FIG.
10 is composed of transistors Q1 and Q2. The head selection signal forming circuit 11 is composed of an inverter INV and a flip-flop FF, the delay circuit 12 is composed of a mono-multi MM1, and the timer circuit 13 is composed of a mono-multi MM2. Further, the write current drawing circuit 14 is composed of a current mirror circuit CM.

The flip-flop FF outputs an inverted signal of the write data WD.
Divide the frequency by 1/2 and output as head select signal φ. This φ is output to the bases of the transistors Q1 and Q2 to control ON / OFF of each transistor. The output of the flip-flop FF is led to the clock terminal of the monomulti MM1 and forms a pulse of time t1 from the rising timing of the Q output. The mono-multi MM2 outputs a pulse having a width of a constant time t2 from the rise of the output pulse of the mono-multi MM1 as a damping effective signal and supplies it to the current mirror circuit CM after the time t1 has passed. The current mirror circuit CM draws a part of the current flowing through the coil of the magnetic head as I _d when the damping effective signal is “H”. The write current is damped by the pull-in current of the current I _d .

FIG. 3 shows a timing chart at the time of writing in the magnetic head circuit.

As shown in the figure, it can be seen that at time t1, the rising characteristics of the current flowing through the selection side coil are extremely good, and at time t2, damping is effectively performed.

In this embodiment, the delay circuit 12 shown in FIG.
Although MM1 is used, other delay elements can be used.

[Brief description of drawings]

FIG. 1 is a block diagram of a magnetic head circuit using a damping circuit at the time of writing according to the present invention. FIG. 2 shows a circuit diagram of an embodiment of the present invention, and FIG. 3 shows a timing chart of the same embodiment. Further, FIGS. 4 and 5 show a circuit diagram of a conventional circuit and a waveform diagram of a main part. L00, L01 …… A coil that constitutes the magnetic head, R2 …… A resistor for damping during reading.

Claims (1)

[Claims] 1. A magnetic head comprising a coil whose power source is connected to an intermediate tap, and head selection which is connected between each of both terminals of the coil and a write current control circuit and is on / off controlled based on a write control signal. In a magnetic head circuit including a switch element, a write current drawing means for drawing a part of a write current from the coil is directly connected to both terminals of the coil in parallel with the write current control circuit, and the head selection switch element is also provided. For a certain period of time after switching on / off
A magnetic head write-time damping circuit comprising a timer circuit for outputting a damping effective signal for operating the write current drawing means from the time when t1 has passed until a certain time t2 has passed.