JPH0629765Y2 - Coil damping circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for a coil drive device for magnetizing a magnetic recording medium such as a floppy disk (FD), a hard disk, and a magnetic tape for magnetically recording various data. The present invention relates to a coil damping circuit, and particularly to reduction of voltage loss by switching means of a damping resistor.

[Conventional technology]

Conventionally, in a recording drive device for a magnetic recording medium such as an FD,
A plurality of sets of magnetic heads for recording are installed close to each other such as corresponding to the recording surface of the FD. Then, a damping resistor is connected in parallel to each coil for driving the magnetic head according to the recording data in order to switch a driving current and generate a required magnetizing voltage.

By the way, when the coil of each magnetic head installed close to each other is closed loop by connecting the resistor, if the magnetic leakage from the magnetic head on the driving side acts on the magnetic head on the driving stop side, the coil on the magnetic head side Since an induced current is generated due to the leakage magnetism, the magnetic head on the drive stop side may generate magnetism due to the induced current even though the drive is stopped, and the magnetic recording medium may be magnetized unnecessarily.

Therefore, conventionally, the damping resistance for each coil is
For example, a switch is interposed between the coil and the coil, and by opening and closing the switch, only the coil on the drive side is closed loop to achieve the required operation, while the coil on the drive stop side disconnects the resistor. In order to prevent an induced current from flowing due to leakage magnetism from another magnetic head, a countermeasure is taken.

FIG. 4 shows a damping circuit in which a single damping resistor is selectively connected to two sets of coil driving devices depending on whether the coils are driven or stopped.

The two sets of coils L1 and L2 correspond to, for example, a magnetic head that magnetizes the recording surfaces set on the front and back surfaces of the FD, and each coil L1 and L2 is provided with an intermediate terminal by an intermediate tap or the like. The coil L1 has two coil pieces L1A, L1B, and a coil L2 sandwiching the intermediate terminal.
Is formed with two coil pieces L2C and L2D.

A drive voltage is applied to each intermediate terminal of each coil L1 and L2 via switches S1 and S2 for switching the coils L1 and L2 in accordance with the selection of the recording surface (size 0, 1) of the FD.
Vcc has been added. Switches S1 and S2 are coils L
1, L2 are selectively opened / closed, for example, when the switch S1 is closed, the coil L1 side is excited, the coil L2 side is not excited, and when the switch S2 is closed, the coil L1 is not excited. The L2 side is set to excitation and the coil L1 side is set to non-excitation.

Then, the terminals A and B of the coil L1 and the terminals C and D of the coil L2 are connected to diodes D11, D12, D21 and D22 for achieving insulation between the coils L1 and L2 from the resistor R for absorbing ringing. Together with the short circuit, the coil pieces L1A and L1 are common to the coils L1 and L2.
A switch S3 for switching the excitation of B, L2C and L2D,
S4 is installed. The switches S3 and S4 are alternately opened and closed by a steep driving pulse based on the recording data at the time of recording, and the opening / closing interval is controlled according to the data to be recorded. The current for driving each of the coils L1 and L2 is given by a constant current from the constant current source SC in order to stabilize the magnetization state and enhance the reliability of magnetic recording.

Therefore, when the switch S1 is closed and the coil L1 side is selected, the switch S3 is closed and the switch S4 is
When is opened, the diode D11 becomes conductive, and a drive current composed of a rectangular wave pulse flows on the coil piece L1A side according to the conduction of the switch S3. In that case, assuming that the switch S4 is in the closed state and the drive current is flowing to the coil piece L1B side immediately before the switch S3 is closed, when the switch S3 is turned on, the diode D12 is also turned on. The electric energy on the side passes through the diode D12, the resistor R and the switch S3, and the constant current source S
It is absorbed on the C side. As a result, the terminals A and B of the coil L1
A voltage due to a steep back electromotive force is generated between the switches S3 and S4, and the voltage causes magnetic recording of necessary data on a magnetic recording medium such as an FD.

Such an operation opens the switch S1 and opens the switch S2.
The same applies when the switches S3 and S4 are alternately opened and closed in the case where is closed.

[Problems to be solved by the invention]

By the way, a damping circuit installed in such a coil driving device includes a selection unit that switches a plurality of coils L1 and L2 to flow a drive current necessary for writing data, and a connection switching unit that connects a resistor R to the coils L1 and L2. And switches S1, S2, diodes D11, D12, D21, D22 and switch S3,
Equipped with S4.

In such a circuit, the internal resistance of the switches S1 and S2 has a finite value, and the diodes D11, D12 and D2 are
1. Due to the VI characteristics of D22 and D22, a voltage drop of about 1 V occurs. Even if such a voltage drop occurs, the drive voltage Vcc is 1
When the voltage is as high as 0 V, the coils L1 and L2
The generated voltage is large, so the ratio to the generated voltage is small, and no inconvenience will occur. However, when the drive voltage Vcc is set to about 5V by a battery or the like, the drive voltage Vcc is reduced to about 4V when the power is reduced. When the voltage drops, the voltage drop of 1V reaches 25% of the driving voltage Vcc, and the ratio is extremely large.

Since the voltage generated between the terminals A and B or between the terminals C and D of the coils L1 and L2 depends on the driving voltage Vcc, when the ratio of the voltage drop is large, the value of the generated voltage is reduced by the voltage drop. As a result, the required magnetization is impaired, and as a result, a reliable recording state may not be obtained.

Therefore, an object of the present invention is to provide a coil damping circuit that generates a necessary voltage even when the driving voltage is low.

[Means for solving problems]

The coil damping circuit of the present invention, as shown in FIG. 1, has coil pieces L1A, L1B, L2 with an intermediate terminal interposed therebetween.
A plurality of coils L1 and L2 having C and L2D are installed, and coil pieces L1A, L1B and L2C of the coils L1 and L2,
Selection means (switch S) for selectively supplying a drive current to L2D
11, S12, S21, S22), and a constant current source SC for supplying the drive current by a constant current, and when the specific coil pieces L1A, L1B, L2C, L2D are driven, the coils L1, L2 are driven. The short-circuits SL1 and SL2 for short-circuiting the terminals of the above through the resistors R1 and R2 are installed.

[Action]

In this damping circuit, the selection of the coils L1 and L2 is performed by selectively turning on the short-circuits SL1 and SL2 installed between the terminals of the coils L1 and L2 to be selected.

For example, as shown in FIG. 2A, when the coil L1 is selected, the switch S11 is closed and the switch S12 is
When the switch is opened, the drive current Id flows through the coil piece L1A, and the switch S11 side is electrically connected to the coil piece L1B.
The electric energy stored on the side is absorbed by the current Ir flowing because the switch S13 is conducting. As a result, a voltage is generated between the terminals A and B of the coil L1 with the driving voltage Vcc as an intermediate point and the side A being negative and the side B being positive.

Next, as shown in FIG. 2B, when the switch S12 is closed, the drive current Id flows through the coil piece L1B,
The electric energy accumulated on the coil piece L1A side is similarly absorbed by the current Ir flowing therethrough. In this case, the coil L
Between the terminals A and B of No. 1, the drive voltage Vcc is set as an intermediate point A
Voltage with positive side and negative side, that is, switch S1
A voltage in the opposite direction to that when 1 is closed is generated.

Such an operation is performed on the coil L2 side when the coil L2 is selected, and a voltage is generated between the terminals C and D of the coil L2.

Therefore, a damping operation similar to that of the circuit shown in FIG. 4 is obtained, and as is apparent from the comparison with the circuit shown in FIG. 4, the switches S1 and S2 and the diode D1 are provided.
Since there is no voltage drop due to 1, D12, D21, D22, even if the driving voltage Vcc is low, each coil L1, L2
A large voltage is generated between the terminals.

〔Example〕

FIG. 1 shows an embodiment of a coil damping circuit of the present invention.

Each of the coils L1 and L2 has an intermediate terminal at the center thereof and has coil pieces L1A, L1B, L2C and L2D, and each intermediate terminal is common without the switches S1 and S2 as shown in FIG. Drive and a driving power source such as a battery is connected. The terminals A, B, C and D of the coils L1 and L2 are
Switches S11 and S1 as selection means for selecting drive
2, a constant current source SC is installed via S21 and S22. The switches S11, S12, S21, S22 are
It is composed of a switching transistor and other switching elements which are opened and closed by a control signal from the driving means.

Then, between the terminals of the coils L1 and L2, resistors R1 and R2 for absorbing ringing and a switch S13 are individually provided.
Short circuits SL1 and SL2 configured by S23 are installed. Like the switches S11, S12, S21, and S22, each of the switches S13 and S23 is composed of a switching transistor that is opened / closed by a control signal from the driving unit, or another switching element.

According to this structure, when the coil L1 is selected, the switch S13 is closed and the switch S23 is opened, and when the coil L2 is selected, the switch S23 is closed and the switch S13 is opened.

When the coil L1 is selected, as shown in FIG. 2A, when the switch S11 is closed and the switch S12 is opened by the drive pulse, the constant current source SC is set on the coil piece L1A side. While the drive current Id due to the constant current flows, the electric energy accumulated on the coil piece L1B side flows to the constant current source SC side via the switch S13 and the resistor R1. As a result, terminal A has a voltage drop due to an increase in impedance at high frequencies, and terminal B has a voltage drop.
Since a counter electromotive force of the coil piece L1B is generated in the coil L1, a high voltage is generated between the terminals A and B of the coil L1, and the voltage can magnetize the magnetic recording medium.

Next, as shown in FIG. 2B, when the switch S11 is opened and the switch S12 is closed by the next drive pulse, the constant current set by the constant current source SC is applied to the coil piece L1B side. While the drive current Id flows, the electric energy accumulated on the coil piece L1A side is reduced by the resistance R1.
And flows to the constant current source SC side via the switch S13. As a result, the back electromotive force of the coil piece L1A is applied to the terminal A,
Since a voltage drop occurs at terminal B due to an increase in impedance at high frequencies, terminals A and B of coil L1
A high voltage is generated between them, and this voltage can magnetize the magnetic recording medium.

The magnetic recording medium is excited by such alternating voltages generated in opposite directions, and necessary magnetic recording is performed. In this case, as is clear from the comparison with FIG. 4, the switch S
1, S2 and diodes D11, D12, D21, D
Since there is no voltage drop due to 22, it is possible to generate a sufficient voltage even if the driving voltage Vcc is low, and it is particularly effective when the driving voltage Vcc due to battery driving is as low as about 5V.

The damping circuit of each coil L1 and L2 is, as shown in (A) of FIG. 3, a short circuit SL provided with a plurality of resistors Rx, Ry and a switch S, or (B) of FIG. As shown, a single resistor R and a short circuit SL provided with a plurality of switches Sx and Sy may be used.

Further, in the embodiment, the case of using the two coils L1 and L2 has been described, but the present invention can be applied to the case of installing a plurality of coils of three or more.

[Effect of device]

As described above, according to the present invention, the switch and the die auto are omitted to prevent the occurrence of the voltage drop, so that the voltage loss can be reduced and a large voltage can be generated between the coil terminals, and the battery can be driven. Even when the driving voltage is low, a voltage necessary for magnetically recording data on the magnetic recording medium can be generated, and stable and highly reliable magnetic recording can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a coil damping circuit of the present invention, FIG. 2 is a circuit diagram showing an operation of the coil damping circuit shown in FIG. 1, and FIG. 3 is a coil damping of the present invention. FIG. 4 is a circuit diagram showing a modified example of the circuit, and FIG. 4 is a circuit diagram showing a conventional coil damping circuit. L1, L2, ... Coil, L1A, L1B, L2C, L
2D ... coil piece, R1, R2 ... resistance, SL1, SL
2 ... Short circuit, S11, S12, S21, S22 ...
Switch, SC ... Constant current source.

Claims (1)

[Scope of utility model registration request] 1. A plurality of coils each having a coil piece sandwiching an intermediate terminal, a selection means for selectively supplying a drive current to the coil piece of each coil, and a constant current source for supplying the drive current by a constant current. And a short circuit that short-circuits the terminals of the coil via a resistor when the coil piece is driven.