JPH01320607A - Constant current pulse generator for writing head - Google Patents

Abstract

PURPOSE:To impress a constant current in accordance with the change of a head resistance value by calculating a voltage value which becomes the refer ence of a constant voltage at the time of an initial action, storing it once and outputting the voltage value at the time of the ordinary action. CONSTITUTION:At the time of an initial action, a constant voltage circuit 2 sends the constant voltage current of a prescribed level Vc based on a reference voltage value Vc. Then, a measuring circuit 4 measures a voltage value Vh impressed to a writing head 1 and sends it to a calculating means 5. The calcu lating means 5 calculates reference voltage value data based on a value R of the full resistance such as an element held by the measuring circuit 4 and a writing head driving circuit 3, a measured voltage value Vh and a constant current level Vc and are stored by a storing part 6. At the time of the ordinary action, the refence data are read, converted by a converting circuit 7, sent to the constant voltage circuit 2 as the reference current, and therefore, the device can correspond to the dispersion of the head resistance value.

Description

[Detailed Description of the Invention] (Summary) A write head that digitally writes data on a record carrier, and a write head drive circuit that drives the write head based on a predetermined constant current and a write pulse signal. Regarding the constant current pulse generator for a write head that has a constant voltage pulse generator, the input criteria are for the purpose of providing a constant voltage pulse generator for a write head that can be driven at a constant voltage, reduce heat generation and power consumption, and downsize the device. a constant voltage circuit that generates a constant voltage current of a predetermined level based on the current level; a voltage value measurement circuit that measures a voltage value applied to the write head; and a voltage value measurement circuit that measures at least a reference voltage value data based on the voltage value. The present invention is configured to include a calculation means for calculating, a storage unit that stores at least the reference voltage value data, and a current conversion circuit that converts the reference voltage value data into a reference current of a corresponding level and sends it to the voltage circuit. .

[Industrial application field]

The present invention relates to a constant current pulse generator for a write head that generates a constant current to be applied to a magnetic head used for magnetic tape, etc., and particularly for a write head that digitally writes data on a record carrier such as a magnetic tape. The present invention relates to a write head constant current generator having a predetermined constant current and a head driving circuit that drives the write head based on pulses of write data.

In recent years, magnetic tape devices have been required to increase the data transfer speed by increasing the number of tracks and performing high-speed writing. For this reason, inductive light thin film magnetic heads are used, but it is necessary to make the write current constant from the viewpoint of guaranteeing the quality of writing and protecting the thin film pattern.

[Conventional technology]

Conventionally, as shown in FIG. 5, a constant voltage circuit 52 that generates a constant voltage current at a predetermined level and a magnetic write head 51 as a write head have a large resistance value (approximately 4Ω) compared to the resistance value (approximately 4Ω). There was a write head current pulse generator having a resistor 54 with a resistance of 37.5Ω) and a magnetic write head 51 as the write head.

Here, the reason why the resistor 54 having a resistance value larger than that of the magnetic write head 51 is provided is that the magnetic write head 51 generally has a variation in resistance value as a product (approximately 4
This is to reduce the variation in the current value applied to the magnetic write head 51 by using the resistor 54 having a resistance value larger than the resistance value of the magnetic write head 51.

[Problem to be solved by the invention]

By the way, in the conventional constant current pulse generator for a write head, as explained above, the value of the pulse current applied to the magnetic write head 51 at high speed is measured, and a peak pulse is generated to apply a pulse current with a constant current value. Since it is difficult to realize the circuit, a resistor 54 having a large resistance value compared to the resistance value of the magnetic write head is used in the magnetic write head 5.
1 in series so that variations in the resistance value of the magnetic write head 51 can be ignored.

Therefore, since the resistance value of the resistor 54 connected in series to the magnetic write head 51 is large, the voltage of the constant voltage circuit 52 becomes high, which not only requires a high voltage transistor and therefore a heat dissipation fin, but also requires the constant current pulse generator. The problem is that it cannot be made smaller.

Therefore, the technical object of the present invention is to solve the above-mentioned problems.The present invention aims to generate constant current pulses for a write head that can be driven with a constant voltage to suppress heat generation and power consumption, thereby reducing the size of the device. This was done for the purpose of providing equipment.

[Means to solve the problem]

The present invention has been made to solve the above-mentioned technical problems, and as shown in FIG. A constant current pulse generator for writing includes a write head drive circuit 3 that drives the write head 1 based on a pulse signal of a constant voltage that generates a constant voltage current of a predetermined level based on the level of an input reference current. a circuit 2, a voltage value measurement circuit 4 that measures a voltage value applied to the write head 1, a calculation means 5 that calculates at least reference voltage value data based on the voltage value, and at least the reference voltage value data. , and a current conversion circuit 7 that converts the reference voltage value data into a corresponding reference current and sends it to the voltage circuit 2.

[Effect]

When using the present invention, as shown in FIG. 1, the constant voltage circuit 2 is set at a predetermined level (similarly, vc) based on a reference voltage value (for example, V) corresponding to the level of the reference current. It sends out a constant voltage current of.

Then, the voltage value measurement circuit 4 measures the voltage value (for example, vH) applied to the write head 1, and generates a signal (for example, 1
is a coefficient for converting an analog value into data) to the calculation means 5.

The calculation means 5 calculates the total resistance value (for example, Rs.
At least the constant voltage circuit 2 calculates reference voltage value data to be used as a reference based on the measured voltage value VH and the level vc of the constant voltage flow. The reference voltage value data is temporarily stored in the storage section 6.

Here, the reference voltage value data is calculated as follows, for example.

That is, the resistance (Rs) and the resistance (
r, ) are connected in series, the current iH applied to the write head 1 is equal to each other, so 1M"VC/ (R8+ rH) -VH/rtt
sea (2), and the resistance value of the write head 1 is determined as rH-Rs/(Vc/VH-1), - (2).

Therefore, when the desired current of the write head 1 is iHc, the reference voltage value data N2C=Vc/2(K
, are coefficients used when the current conversion circuit 7 converts reference voltage value data into a corresponding current) can be obtained by the following equation.

N2cm (fH(HXrH” R5) /2
``• Therefore, according to the present invention, it is possible to apply a constant current to the rad 1 for writing.

Note that this work is performed at a different time from the normal write operation, for example, during the initial operation, and when performing the normal write operation, the write head 1 is operated based on the pulse current of the write data input to the write head drive circuit 3. will be driven to perform writing.

The reason why at least the reference voltage value data is stored in the storage section 6 is that when writing at high speed, the reference voltage value data is calculated in real time and immediately fed back to the constant voltage circuit 2 for use. This is because it is not possible.

- The reference voltage value data once stored in the storage section 6 is read out during normal writing, converted by the current conversion port 7, and sent to the constant voltage circuit 2 as a reference current, and the above procedure is performed. It will be repeated.

〔Example〕

Next, examples of the present invention will be described.

This embodiment relates to a constant current pulse generator for a write head for a thin film magnetic write head (hereinafter referred to as "magnetic write head") as a write head that records on a magnetic tape as a record carrier.

As shown in FIG. 2, this embodiment includes a constant voltage circuit 12 that generates a constant voltage current of a predetermined level based on the level of an input reference current, a voltage value measuring circuit 14, TSTI, TS
T2. A magnetic write head drive circuit 13 that drives the magnetic write head 11 based on the signals applied to the IH and *IH terminals and the constant voltage current output by the constant voltage circuit 2; and a magnetic write head drive circuit 13 that drives the magnetic write head 11; head 11
and a microprocessor device 15 having TSTI and TST2 terminals and serving as calculation means 5 for calculating reference voltage value data and resistance value data of the magnetic write head 11, and storing the reference voltage value data and resistance value data. It is possible to write and read data as a storage unit 6 and is non-volatile (memory contents are not erased even if the power is turned off).
EE-ROM (ElectricErasab
16, and a D/A converter 17 as a current conversion circuit 7 that converts the reference voltage value data into a reference current of a corresponding level. As shown in FIG. 2, the constant voltage circuit 12 includes an operational amplifier 12a that amplifies the difference between the reference voltage value and the voltage value of the collector current, a PNPW transistor 12b that operates in a non-saturation region, and a magnetic write circuit. Degauss of Rad 11 (
The capacitor 12c provides a voltage value for demagnetization.

The voltage value measuring circuit 14 includes resistors 14b and 14c, and a comparator 14a used to convert the magnetic write head terminal voltage into a digital value.

Furthermore, the magnetic write head drive circuit 13 outputs a drive signal according to test conditions at the time of initialization by turning on the power, etc.
It has R elements 13a and 13c, and magnetic write head drive transistors 13d and 13b that perform a switching operation based on the drive signal.

Although only one magnetic write head 11 has been described above to simplify the explanation, the number of magnetic write heads 11 is generally not limited to one, but a plurality (n).

Next, the operation of this embodiment will be explained.

During normal write operation, the D/A converter 17
A reference current of a constant reference voltage is sent to the constant voltage circuit 12 from the AC2 terminal. Then, it is input to the negative terminal of the operational amplifier 12a of the constant voltage circuit 12. The operational amplifier 12a outputs a current with an output voltage proportional to the voltage difference between the positive terminal and the negative terminal.
A constant voltage current is input to the base of the NP-type transistor 12b, and is output from the collector side of the transistor 12b, which operates in a non-saturation region.

Further, the TSTI and T of the microprocessor device 15 are
When the signal output from the ST2 terminal is in the “LO” state,
IH or *IH of the magnetic write head drive circuit 13
By applying a pulse signal to one of the terminals alternately, pulse currents in both positive and negative directions are caused to flow through the magnetic write rad 11 to perform a write operation and simultaneously demagnetize the magnetic write rad 11.

On the other hand, during initialization when the power is turned on, etc., the operation is as follows.

As shown in FIG. 3, after the level of the current inputted from the D/A converter 17 to the DAC2 terminal of the constant voltage circuit 12 is set to a constant state (2), the current is inputted to the TSTI terminal of the magnetic write head drive circuit 13. The constant current 1. from the constant voltage circuit 12 is applied to the magnetic write rad 11 when the signal is in the ggH1l state (2). flows, and a voltage vH is generated in the head 11.

The microprocessor device 15 is the DA of the D/A converter 17.
When the level of the output signal from the CI terminal is gradually increased as shown in FIG. 3, the measurement signal at the output terminal LVLI of the comparator 14a of the voltage value measurement circuit 14 changes from the on state to the off state (■, ■). Based on the measurement signal input from the measurement circuit 14 at the time of the change, the microprocessor device 15 as the calculation means 5 determines that the digital value N1 of DA (:1) is the A/D converted value of the magnetic write head terminal voltage vH. recognized as

In addition, the microprocessor device 15 substitutes the measured voltage value N1 into the above-mentioned equation 0 and applies the rad 1 to the magnetic write.
After finding the resistance value data r of 1, calculate N2C corresponding to the desired current to be applied to the magnetic write rad 11 as the digital value of the reference voltage DAC2 of the constant voltage source from equation 0, and calculate the above D/ The A converter 17 converts it into a reference current of a corresponding level and updates the reference voltage applied to the constant voltage circuit 12 (■).

If a constant voltage current of a level determined by the reference voltage updated in the same manner is generated from the constant voltage circuit 12, the same operations (■, ■, ■) are repeated for DACI and LVLI as in the case described above. The measurement circuit 14
Then, when the correctness of the resistance value data rH determined in ■■ is confirmed by the calculation means 15, the resistance value data r
H and reference voltage value data N2C are stored in the EE-ROM 16 and used as the reference voltage value of the constant voltage source during normal write operation.

After calculating r and N2C, turn off DAC2 ([
]) TSTl, using the charging of the rear capacitor 12c.
By alternately applying pulse signals (@, @) and discharging (■) to TST2, the magnetic write head 11 is demagnetized (degaussed), and the calculation work of rHI N2C is completed.

Management of the D/A conversion circuit 17, test condition signal TST
I, generation of TST2, output terminal L of comparator 14a
The monitoring of the signal from VL1, the storage and reference of the reference voltage value vc and the resistance value r of the magnetic write head 11 in the EE-ROM 16 are controlled by the microprocessor device 15.

Next, other embodiments will be described.

In the embodiment described above, the EE-RO is used for storing the calculation results.
I used M17, but R with battery backup
It is also possible to use AM.

Furthermore, if it is always possible to keep the magnetic medium sufficiently away from the magnetic writer rad 11 by mechanical means, a RAM may be used.

Further, the OR circuits 13a and 13c can also be realized by software.

Note that the demagnetizing operation by the capacitor 12c may be realized by successively reducing the output terminal DAC2 of the D/A converter 17.

(Effects of the Invention) As explained above, in the present invention, in order to avoid fluctuations in the current applied to the write head caused by product variations such as the resistance value of the write head, the reference voltage of the constant voltage circuit is The value is calculated and stored in the storage section, and during normal operation, the value is sent to the constant voltage circuit so that the circuit outputs a voltage value based on the value.

Therefore, it is possible to apply an optimum constant current to the write head in accordance with variations in the resistance value of the write head due to variations in each product or changes in temperature.

Further, heat generation can be prevented and the device can be downsized without the need to use a resistor with a high resistance value and a high voltage power source as in the conventional case.

[Brief explanation of the drawing]

FIG. 1 is a principle block diagram of the present invention, FIG. 2 is a circuit diagram according to an embodiment, FIG. 3 is a timing chart according to an embodiment,
FIG. 4 is a flowchart according to a conventional example. 1 (11)...Writing head (magnetic write head) 2 (12)...Constant voltage circuit 3 (13)...Writing head drive circuit (magnetic write head drive circuit) 4 (14)...Voltage Value measurement circuit 5 (15)...Calculation means (microprocessor device) 6 (16)...Storage unit (EE-ROM) 7 (17)
...Current conversion circuit (D/A converter) sales port I; related shield, S-Supervisor Pro, Figure 7, Figure 11! l Takashi Isho 11 Nii Itoru Timing Night No. 31! l 4th question

Claims (1)

[Scope of Claims] A write head (1) having a predetermined resistance value for digitally writing data on a record carrier;
); and a constant voltage circuit (2) that generates a constant voltage current at a predetermined level based on the level of an input reference current. a voltage value measuring circuit (4) that measures a voltage value applied to the write head (1); a calculation means (5) that calculates at least reference voltage value data based on the voltage value; and at least the reference voltage. Storage section (6) that stores value data
), and a current conversion circuit (7) that converts the reference voltage value data into the reference current of a corresponding level and sends it to the voltage circuit (2). Device.