JPH05307705A - Magnetic head driving circuit - Google Patents

Abstract

PURPOSE:To constitute the magnetic head driving circuit having a short rise/fall time of an inversion magnetic field and also small power consumption in a small scale circuit. CONSTITUTION:A magnetic head 2 is composed of two recording coils L1 and L2 electrified with a current to be supplied in the reverse turning directions to each other from a DC power source circuit 1 via an auxiliary coil L0, and a modulation magnetic field is generated on the magnetic head 2 by alternately switching on/off switching elements Q1 and Q2 connected to the individual recording coils L1 and L2 in accordance with a recording signal. Then, transient distortion of a current waveform at the switching time for electrifying the recording coils L1 and L2 is prevented by constant voltage diodes D1 and D2 in parallel connection with the switching elements Q1 and Q2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head drive circuit, which is applied to a magnetic field modulation type magneto-optical recording device or the like, which drives the magnetic head with a simple structure to save power and outputs a modulation magnetic field to a recording signal. The present invention relates to a circuit corresponding to which it is possible to invert with a short response time.

[0002]

2. Description of the Related Art A magnetic field modulation type magneto-optical recording apparatus is used for recording on a rewritable compact disk or the like, and a perpendicularly magnetized film of the magneto-optical disk is irradiated with laser light of a constant intensity by an optical pickup. Information is recorded by applying a modulation magnetic field generated by a magnetic head to the irradiated portion while the temperature is raised above the Curie point and leaving a magnetic pattern corresponding to the change in the magnetic field. Here, the magnetic field is modulated by applying a current corresponding to the recording signal to the coil of the magnetic head, and it is of course ideal that the waveform of the applied current is exactly correlated with the waveform of the recording current. ..

By the way, in general, the magnetic head can be regarded as an LR series circuit having a resonance frequency smaller than the polarity reversal frequency of the energized current, and the current's initial response to the step signal E (V) is I = Io {1-exp ( -Rt / L)} (however, t; time, I
o = E / R), and the current rises with the L / R time constant. Therefore, in order to shorten the response time to the change of the recording signal, it is necessary to reduce the inductance of the coil of the magnetic head or increase the resistance value, which inevitably sets the driving power to a large value.

Conventionally, various proposals have been made as means for shortening the response time while driving a magnetic head with a small electric power, and FIG. 6 shows a typical magnetic head drive circuit. In the circuit of FIG. 6 (A), the auxiliary coil Lda and the switching element S11 are connected in series to one of the DC power supply circuits 11 and grounded, and the other DC power supply circuit 12 has an auxiliary coil.
Ldb and switching element S12 are connected in series and grounded, and auxiliary coil Lda in each series connection circuit,
It has a configuration in which the coil Lx of the magnetic head is connected to the connection circuit of Ldb and switching elements S11, S12, and by turning on / off the two switching elements S11, S12 alternately according to the recording signal, the coil Lx is connected. Currents of opposite polarities are alternately applied. In this circuit, the response time to the change of the recording signal is an extremely short time such as the switching time of the switching elements S11 and S12, and the coil Lda,
Since the inductance of Ldb is set to be sufficiently larger than the inductance of the coil Lx, the values of the alternating currents are almost the same. Furthermore, since the resistance element is only the resistance of each coil, low power consumption is sufficient.

On the other hand, the circuit of FIG. 6B is a DC power supply circuit 13
One auxiliary coil Ld is connected to, and a circuit in which two switching element series circuits (S21-S22), (S23-S24) are connected in parallel is connected to the auxiliary coil Ld and grounded. The pair of switching elements (S21 and S24) and (S22 and S23) are alternately turned on / off so that a current of opposite polarity is alternately applied to the coil Lx. This circuit also has a short response time to a change in the recording signal based on the same operation principle as that of the above-mentioned circuit, thus achieving power saving.

[0006]

By the way, the conventional magnetic head drive circuit realizes the reduction of the response time to the change of the recording signal and the power saving, but the circuit of FIG. Since the auxiliary coils Lda and Ldb are required, and the four switching elements S21, S22, S23, and S24 are required in the circuit of FIG. 6B, there is a problem in that the number of circuit elements increases. Since the magnetic head and its drive circuit applied to the magneto-optical recording device are moved along the surface of the magneto-optical disk together with the optical pickup while mounted on the slider,
It is necessary to reduce the mounting volume and the total weight, and the above problems affect the drivability of the slider and the optical pickup. Further, when the polarity of the current flowing through the coil Lx of the magnetic head changes, a counter electromotive voltage is generated in the coil Lx, and thus a large amount of power is consumed before the reversal.

Therefore, the present invention provides a magnetic head drive circuit capable of driving a magnetic head in a power-saving manner with a simple and small-scale circuit configuration and shortening the rise / fall time of a drive current with respect to a recording signal. It was created for that purpose.

[0008]

According to the present invention, in a magnetic head drive circuit for generating a modulation magnetic field corresponding to a recording signal, a direct current power source for supplying a current to a coil of the magnetic head,
It has an auxiliary coil connected to the DC power source and having a sufficiently larger inductance than the coil of the magnetic head, and two recording coils wound coaxially, and the current supplied from the auxiliary coil is used for each recording. A magnetic head that energizes the coil in the reverse direction and two switchings that are connected in series to each recording coil and that alternately turn on and off the energization state of each recording coil according to the recording signal. The present invention relates to a magnetic head drive circuit comprising an element and two constant voltage diodes connected in parallel to each of the switching elements.

[0009]

In the magnetic head of the present invention, the energy accumulated in the auxiliary coil is passed as a current in the reverse circulation direction.
Each recording coil is provided, and the polarity of the magnetic field is reversed by alternately turning ON / OFF the switching elements connected to each recording coil. Therefore, a recording current can be generated with one auxiliary coil and two switching elements, and there are two recording coils, but since they are wound coaxially, the mounting volume is one. Almost the same as the case of the coil. The ON / O of each switching element
At the start of energization of each recording coil by the FF operation, the voltage generated in one recording coil becomes the polarity of the energized voltage for the other recording coil, so the rise / fall time is further shortened and saved. Electrification is achieved.

By the way, when the switching element is turned on, a resonance circuit is formed by the series connection of the capacitance of the element and the coil, and the current waveform after rising / falling of the current passed through each recording coil is formed. Transient strain may occur. In the present invention, a constant voltage diode is connected in parallel to each of the switching elements to keep the connection circuit of the recording coil and the switching element at a constant voltage to remove the transient distortion.

[0011]

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 5. Fig. 1 shows an electric circuit diagram of the magnetic head drive circuit. 1 is a DC power supply circuit, L0 is an auxiliary coil, 2 is a magnetic head, Q1 and Q2 are P-channel FETs, D1 and D2 are constant voltage diodes (Zener diodes). ) And 3 are inverting circuits.
Here, the magnetic head 2 has two recording coils L1 and L2 wound around the core by the same number of turns in mutually reverse winding directions. The inductance of the auxiliary coil L0 is set sufficiently larger than the inductance of the recording coils L1 and L2.

Then, each recording coil L1 of the magnetic head 2 is
One terminal of L2 is connected to the auxiliary coil L0 connected to the DC power supply circuit 1, and the current from the auxiliary coil L0 flows in the reverse circulation direction. On the other hand, the other terminals of the recording coils L1 and L2 are connected to the drains of the FETs Q1 and Q2, respectively, the sources of the FETs Q1 and Q2 are grounded, and the gate of the FET Q1 is directly connected to the recording signal circuit. , The gate of the FET Q2 is connected to the recording signal circuit via the inverting circuit 3. In addition, the FETs Q1 and Q2 have constant voltage diodes D1 and D1 arranged in the forward direction from the source side to the drain side.
2 is connected.

From the recording signal circuit, the NZR (Non-Return
When a recording signal of the (0 to Zero) method is input, the FET Q1 is turned on by a "1" signal, and the FET Q1 to which a recording signal is input via the inverting circuit 3 is turned on by a "-1" signal, It turns on / off alternately in response to changes in the recording signal. Therefore, assuming that the recording signal is "1", FETQ1
Since the FET Q2 is turned off at N, the current I1 flows only from the auxiliary coil L0 to the recording coil L1 of the magnetic head 2, and the magnetic head 2 generates a magnetic field based on the energization of the recording coil L1. In this case, the auxiliary coil L0 and the recording coil L1
Energy of each 1/2 · L0 · I1 ² and 1/2 · L1 · I1 ² is accumulated in the.

Next, when the recording signal changes from "1" to "-1", the FET Q1 is turned off and the FET Q2 is turned on. Therefore, the current I2 from the auxiliary coil L0 to the recording coil L2 of the magnetic head 2 is changed.
Flow, the magnetic head 2 generates a magnetic field based on the energization of the recording coil L2. The magnetic field in this case has a polarity opposite to that in the case where the recording signal is "1" because the recording coils L1 and L2 are wound in reverse winding. Further, in this case, the energy 1/2, L1, I1 ² accumulated in the recording coil L1 when the recording signal is "1" is equal to the recording coil L2.
Since the current I2 is emitted so as to apply a voltage in the energizing direction, the rising of energization to the recording coil L2 is smoothed.
Speed up. From the point of view that the magnetic fields of opposite polarities are generated in the recording coils L1 and L2 corresponding to the state in which FETQ1 and FETQ2 are alternately turned ON / OFF, the windings of the recording coils L1 and L2 in the magnetic head 2 are not always required. It is not necessary to realize it by rotating direction, and as shown in FIG. 2, both recording coils L
The same function can be provided by winding 1 and L2 in the same direction and connecting the recording coil on one side to the auxiliary coil L0 and the FET on the other side in reverse.

In this way, an alternating magnetic field is generated in the magnetic head 2 in response to the change of "1" and "-1" of the input recording signal. At the time of switching, the recording coil is changed. A sudden current flows through L1 and FET Q1, or recording coil L2 and FET Q2, and the inductance of recording coils L1 and L2 and FTE
Rise / rise due to the series resonant circuit composed of the capacitances of Q1 and Q2.
Transient distortion occurs in the current waveform after falling. To solve this problem, in this embodiment, constant voltage diodes D1 and D2 are connected in parallel to each FTEQ1 and Q2, and the recording coils L1 and L2 are connected.
The occurrence of transient distortion is prevented by maintaining a constant voltage at the connection point between FTEQ1 and FTEQ1 and Q2.

Further, in order to analyze the function of each circuit element of the present embodiment, all circuits are removed when the auxiliary coil L0 is removed, the constant voltage diodes D1 and D2 are removed, and the circuit shown in FIG. Assuming that elements are provided, the magnetic field generated by the magnetic head 2 in each case is shown in FIGS.
And shown in FIG.

As is apparent from FIG. 3, except for the auxiliary coil L0, energy is not accumulated by energization, and the magnetic field generated by the magnetic head 2 becomes an integral waveform or a sawtooth waveform, so that normal recording cannot be expected at all. .. In FIG. 4, a rectangular wave-shaped generated magnetic field corresponding to the recording signal is obtained due to the presence of the auxiliary coil L0, but since the constant voltage diodes D1 and D2 are removed, transient distortion is generated at the time of rising / falling. This causes a recording error or the like. On the other hand, the waveform in FIG. 5 shows the auxiliary coil L0 and the constant voltage diode D.
Due to the existence of 1 and D2, a rectangular wave corresponding to the recording signal of the NZR system is formed, and the polarity of the generated magnetic field can be inverted exactly, and error-free recording is possible.

[0018]

The magnetic head drive circuit of the present invention has the following effects due to the above configuration. The magnetic head is configured by winding two recording coils that energize the current supplied from the auxiliary coil in the reverse winding direction, and each recording is performed with two switching elements that alternately turn on and off according to the recording signal. Since the coil for power supply is energized, it is possible to shorten the rise / fall time of the recording current with respect to the recording signal while driving the magnetic head in a small-scale circuit with low power consumption, thus ensuring accurate recording signals. To realize a magnetic head drive circuit free from recording errors by generating a magnetic field corresponding to. In addition, the voltage at the connection between each recording coil and switching element is held constant by a constant voltage diode connected in parallel to each switching element, and transient distortion that occurs when the recording current rises / falls To prevent. According to the magnetic head drive circuit of the present invention, the power consumption can be reduced by about 30% and the recording current jitter can be improved by about 10% as compared with the conventional circuit configuration.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a magnetic head drive circuit of the present invention.

FIG. 2 is an electric circuit diagram showing another embodiment of the magnetic head.

FIG. 3 is a graph showing a magnetic field generated when an auxiliary coil is removed.

FIG. 4 is a graph showing a magnetic field generated when a constant voltage diode is removed.

5 is a graph showing a magnetic field generated by the magnetic head drive circuit of FIG. 1. FIG.

FIG. 6 is an electric circuit diagram of a conventional magnetic head drive circuit.

[Explanation of symbols]

1 ... DC power supply circuit, 2 ... Magnetic head, 3 ... Inversion circuit, 4 ... Transient distortion, D1, D2 ... Constant voltage diode (Zener diode), L0 ... Auxiliary coil, L1, L2 ... Recording coil, Q1, Q2 ... F
ET.

Claims (1)

[Claims] 1. A magnetic head drive circuit for generating a modulation magnetic field corresponding to a recording signal, and a DC power supply for supplying a current to a coil of a magnetic head, and a DC power supply connected to the DC power supply.
An auxiliary coil having an inductance sufficiently larger than that of the coil of the magnetic head and two recording coils wound coaxially are provided, and a current supplied from the auxiliary coil is directed in a reverse winding direction with respect to each recording coil. , A magnetic head for energizing each of the recording coils, two switching elements connected in series to each of the recording coils, and alternately turning on / off the energization state of each recording coil in response to a recording signal, and each of the switching elements described above. A magnetic head drive circuit comprising: two constant voltage diodes connected in parallel to an element.