JPH04252404A - Recording current control device - Google Patents

Abstract

PURPOSE:To suppress a recording data fluctuation, which is caused by the variation of head impedance of DAT, etc., by controlling the gain of recording current. CONSTITUTION:The voltage at both ends of the head 3 is detected by a voltage detector 11, and only the component of the prescribed frequency of this signal is detected for its peak by a peak detector 13. The voltage whose peak is detected by the peak detector 13 is supplied to a sample-and-hold circuit 14. The voltage of a section which corresponds to a prescribed period in DAT format is sampling and holding by the sample-and-hold circuit, and by a voltage gain controller amplifier in which such voltage is set as the control voltage, the gain of the recording current is controlled.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording current control device suitable for use in a recording device such as a digital audio tape recorder (DAT) that records information on a magnetic tape using a rotary head.

0002

2. Description of the Related Art In a magnetic recording apparatus using a conventional head, variations in the impedance characteristics of the recording head are unavoidable, so even if the output current of the recording amplifier is constant, the voltage generated in the head varies. As a result, the recording level recorded on the magnetic tape changes, so it is necessary to adjust the recording current level for each device.

FIG. 6 shows an example of a conventional recording current adjustment circuit, in which the recording current is controlled by a voltage gain control amplifier (VC
A) 1, and is amplified by a recording amplifier 2 and supplied to a rotary recording head 3. The amplification gain of the VCA 1 is controlled by a control voltage set for each device by an adjustment voltage generator 4, and the level of the recording current is adjusted.

0004

[Problems to be Solved by the Invention] In the conventional recording current control device as described above, it is necessary to adjust the adjustment voltage generator 4 for each device to set the control voltage of the VCA 1 and adjust the recording current level. This increases the number of work steps and increases the cost of the product.

[0005] The present invention has been made in view of this situation, and it is an object of the present invention to provide a device that does not require adjustment work.

[0006]

[Means for Solving the Problems] A recording current control device according to claim 1 is a recording current control device for a recording device that records information on a magnetic tape using a head, and the recording current control device is a recording current control device for a recording device that uses a head to record information on a magnetic tape. filter means for extracting only a predetermined frequency band of the output of the detection means; generation means for generating a control voltage according to the level of the output of the filter means; The present invention is characterized by comprising a sample hold means for holding a sample, and a level control means for controlling the level of a recording signal according to the output of the sample hold means.

A recording current control device according to a second aspect of the present invention is a recording current control device for a recording device that uses a head to record information on a magnetic tape, and the recording current control device includes a detection means for detecting a voltage generated at both ends of the head. , a filter means for extracting only a predetermined frequency band of the output of the detection means, a generation means for generating a control voltage according to the level of the output of the filter means, and a sample hold means for sampling and holding the control voltage in a predetermined section of the recording signal. The apparatus is characterized by comprising: level control means for controlling the level of the recording signal according to the output of the sample hold means; and storage means for storing the output of the sample hold means.

A recording current control device according to a third aspect of the present invention is a recording current control device for a recording device that records information on a magnetic tape using a head, and includes a reference recording signal generating means for generating a reference recording signal; A detection means for detecting the voltage generated across the head, a rectification means for rectifying the voltage detected by the detection means, an A/D conversion means for digitizing the output of the rectification means, and a digitized signal and a reference. The present invention includes a comparison means for generating error data by comparing with the data, a storage means for storing the error data, and a level control means for controlling the level of the recording signal according to the error data stored in the storage means. Features.

[0009]

In the recording current control device according to the first aspect of the present invention, the detection means detects the voltage generated across the head. Of the output of the detection means, only components in a predetermined frequency band are extracted by the filter means. A control voltage corresponding to the amplitude of the signal extracted by the filter means is generated by the generation means, and a control voltage in a predetermined section in the recording signal is sampled and held by the sample hold means. The level control means is controlled by the sampled and held control voltage, and the level of the recording signal is adjusted. Therefore, there is no need to adjust the recording current.

In the recording current control device according to the second aspect of the present invention, the detection means detects the voltage generated across the head. Of the output of the detection means, only components in a predetermined frequency band are extracted by the filter means. A control voltage corresponding to the amplitude of the signal extracted by the filter means is generated by the generation means, and a control voltage in a predetermined section in the recording signal is sampled and held by the sample hold means. The sampled and held control voltage is stored in the storage means and is also supplied to the level control means to control the level of the recording signal. Therefore, the process for adjusting the recording current only needs to be performed once.

In the recording current control device having the third aspect of the present invention, a reference recording signal is supplied to the head. The voltage generated across the head is detected by the detection means, and the detected voltage is rectified by the rectification means. The rectified voltage is digitized by the A/D conversion means, the digitized signal is compared with reference data by the comparison means, and the comparison result is supplied to the storage means as error data. The level control means controls the level of the recording signal according to the error data stored in the storage means. Therefore, the adjustment operation can be completed quickly when the power is turned on.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention. Note that the same reference numerals are given to the parts corresponding to those in the conventional case, and the explanation thereof will be omitted as appropriate.

In the figure, the recording current during recording is VCA1
, are supplied to the head 3 via the recording amplifier 2. A voltage detector 11 detects the voltage appearing across the head 3. Here, if the input impedance of the voltage detector 11 is small, the current flowing to the head 3 will be affected by the voltage detector 11. Therefore, the input impedance of the voltage detector 11 will be limited to the entire recording band of the recording current (in the case of DAT, from 130 kHz to 4 kHz). .7
MHz).

FIG. 2 shows part of the DAT data format. In the DAT data format,
A single frequency of 4.7 MHz is recorded over 11 blocks (one block is 288 bits) in the marginal area (MARGIN). Following this, in order to record time, address, etc., a preamble (PLL), sub data area (SUB CODE), and postamble (P
OST AMBLE) is formed. Furthermore, an automatic track finding (ATF) for tracking control is formed between interblock gaps (IBG) to provide sufficient switching time between recording and playback, and a preamble (PLL)
) is followed by a data area (PCM).

That is, the 4.7 MHz single frequency signal recorded in the marginal area exists regardless of the presence or absence of PCM data. The filter 12 extracts only this single frequency component and uses the peak detector 13 as a generating means.
supply to. The attenuation characteristic of this filter 12 is shown in FIG. The peak detector 13 detects the peak value of the detected voltage, that is, the level of the single frequency signal extracted by the filter 12, for use in adjusting the control voltage.

The peak level voltage detected by the peak detector 13 is supplied to a sample and hold circuit 14. The sample-and-hold circuit 14 samples and holds the peak level voltage during the aforementioned marginal area period using a sample-and-hold pulse synchronized with the marginal area generated from a controller (not shown), and sends the sample-and-held voltage value to the control voltage generation circuit 15. Output. The control voltage generation circuit 15 has an internal reference voltage source, and uses the error voltage from the input voltage value as the control voltage to output the VCA.
Supply to 1. And VCA1 is control voltage generation circuit 1
The gain of the recording current is controlled in accordance with the control voltage outputted from 5.

With the above configuration, when the impedance of the head 3 differs from device to device, the voltage appearing across the head 3 changes, and the control voltage generation circuit 15 generates a control voltage corresponding to the amount of change. Therefore, the VCA1 controls the gain of the recording current so that the peak level voltage approaches the reference voltage. Therefore, if the reference voltage value is set to an optimal value at the design stage, the recording level recorded by the head 3 will always be constant regardless of individual differences between the heads 3.

In DAT, the frequency characteristics of the magnetic recording and reproducing level peak at 1 MHz to 2 MHz and worsen as the frequency increases, and the higher the frequency, the greater the variation depending on the head. Therefore, in the present invention, the level of the recording current is controlled according to the predetermined frequency band recorded in the marginal area existing in the recording signal, that is, the highest frequency component among the detected voltages of the voltage detector 11. Highly accurate recording current control becomes possible.

FIG. 4 is a block diagram showing the configuration of a second embodiment of the present invention.

In FIG. 4, in addition to the configuration of the first embodiment shown in FIG.
, a memory circuit 22 that holds and stores the analog voltage value that is the output of the sample and hold circuit 14, and a control voltage generator 15.
and a controller 2 that controls the operation of the memory circuit 22
3 is provided.

First, when the power is turned on, the recorded data is stored in VCA1.
given to. In the case of a 90 degree wrap DAT, the timing of this recording data is set to a period in which the head 3 is not in contact with the tape, and therefore this recording signal is not recorded on the tape. Then, the peak value of the voltage across the head 3 is sent to the sample and hold circuit 14 as in the first embodiment.
Sample and hold is performed at the timing of the marginal area.

On the other hand, at the initial stage when the power is turned on, the control voltage generator 15 inputs the output of the sample and hold circuit 14 under the control of the controller 23, and outputs the error voltage from the internal reference voltage to the VCA 1 as a control voltage. supplying. When the system is stabilized by this feedback loop, the recording current level is set to the optimum value. When a preset time (time until the feedback loop becomes sufficiently stable) has elapsed, the controller 23
The memory 22 is brought into a writing state, and the input of the control voltage generator 15 is switched to the memory 22 side. From now on, the control voltage generator 15 will output the error voltage between the output of the memory 22 and the internal reference voltage to the VCA 1. At the same time, the output of recording data for setting to the VCA 1 is stopped, and from this point on, recording operations corresponding to normal recording operations are performed.

By providing the memory 22 in this manner, the peak level voltage at the time when the feedback loop system reaches a stable state is stored in the memory 22, and during actual recording, the recording current is determined by the voltage value stored in the memory 22. level is controlled. That is, it is possible to disable the control voltage detection operation during recording, and unnecessary power consumption can be prevented.

FIG. 5 is a block diagram showing the configuration of a third embodiment of the present invention.

In the figure, either the actual recording current input from the terminal 33 or the reference recording signal supplied from the recording reference signal generation circuit 31 is selected by the switch 32 and supplied to the VCA 1. There is. For example, a 4.7 MHz continuous wave is used as the reference recording signal.

The voltage across the head 3 detected by the voltage detector 11 is rectified by a rectifier circuit 34 as a rectifier to become a DC voltage. This DC voltage is digitized by the A/D converter 35 and becomes one input of the digital subtracter 36. Reference data from a reference data generation circuit 37 is supplied to other inputs of the digital subtracter 36 .

The digital subtracter 36 functions as a comparison means for comparing the DC voltage obtained by rectifying the voltage across the head 3 with the reference data from the reference data generation circuit 37, and supplies the difference between the two as error data to the memory 38. do. memory 3
Writing and reading of error data to and from 8 is controlled by a controller 39. The error data written as necessary is constantly read out from the memory 38 and supplied to the PWM modulator 18 which controls the duty of the output signal according to this error data. That is, since the DC component of the output of the PWM modulator 18 changes according to the error data, this DC component is extracted by the low-pass filter (LPF) 41, and the VCA 1 is controlled according to the output of the LPF 41.

The operation of the recording current control device having the above configuration will be explained.

First, the controller 39 receives the 4.7M signal from the recording reference signal generation circuit 31 when the power of the apparatus is turned on.
The switch 32 is changed so that the recording reference signal, which is a continuous wave of Hz, is supplied to the VCA1. Further, the controller 39 puts the memory 38 in write mode and writes the error data obtained during this period into the memory 38.

That is, the voltage across the head 3 is rectified and A/
If the D-converted head voltage data is larger than the reference data, the error data is written into the memory 38 as a positive value. The PWM modulator 18 acts to reduce the duty of the output signal based on this error data. This reduces the level of the DC component extracted by the LPF 41. As a result, the gain of the recording current by VCA1 decreases. Further, when the head voltage data is smaller than the reference data, the error data becomes negative, and the PWM modulator 40
The output duty of is large. As a result, LPF4
The output level of 1 is increased, and the gain of the recording current is increased. In this way, the servo is applied so that the head voltage data and the reference data are finally approximately equal.

After a period of time until the value of the error data becomes sufficiently small, the controller 39 adjusts the normal recording current to VC.
The switch 32 is switched so that the signal is supplied to A1, and writing of new data to the memory 38 is prohibited.

By performing level adjustment using the recording reference signal, which is a continuous wave of 4.7 MHz, as described above,
During the recording operation of PCM data, the recording current level is adjusted according to the output of the PWM modulator 18, which is adjusted during the level adjustment period immediately after the power is turned on.

Although each of the above-mentioned embodiments has been explained using a DAT, the present invention is not limited to this and can also be used in a video tape recorder or the like.

[0035]

As described above, according to the recording current control device according to claim 1, the detection means detects the voltage generated across the head to which the recording current is supplied, and the recording current is controlled in accordance with the detected voltage. Since the current level is controlled, even if there are variations in head impedance, the recording current level can be automatically controlled, making it possible to keep the recording level recorded on the tape almost constant. .

Further, according to the recording current control device according to the second aspect, since the detected voltages at both ends of the head are stored, the detected voltages detected prior to the original data recording operation are stored. Therefore, unnecessary power consumption can be prevented by disabling the detection voltage detection operation during the original data recording operation.

Furthermore, according to the recording current control device according to the third aspect, since the level of the recording current is controlled using the reference recording signal generated by the reference recording signal generating means, the level of the recording current is controlled when the power is turned on. etc., adjustment operations can be performed quickly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a first embodiment of a recording current control device of the present invention.

FIG. 2 is a diagram showing part of a DAT data format.

FIG. 3 is a graph showing the attenuation characteristics of the filter in FIG. 1;

FIG. 4 is a block diagram showing the configuration of a second embodiment of the recording current control device of the present invention.

FIG. 5 is a block diagram showing the configuration of a third embodiment of the recording current control device of the present invention.

FIG. 6 is a block diagram showing the configuration of an example of a conventional recording current control device.

[Explanation of symbols]

1 Voltage gain control amplifier (voltage control means) 2 Recording amplifier 3 Head 4 Adjustment voltage generator 11 Voltage detector (detection means) 12 Filter 13 Peak detector (generation means) 14 Sample and hold circuit 22 Memory (storage means) 31 Standard Recording signal generation circuit 34 Rectifier circuit (rectifier means) 35 A/D converter 36 Digital subtracter (comparison means) 38 Memory 39 Controller

Claims (3)

[Claims] 1. A recording current control device for a recording device that records information on a magnetic tape using a head, comprising: a detection means for detecting a voltage generated across the head;
filter means for extracting only a predetermined frequency band of the output of the detection means; generation means for generating a control voltage according to the level of the output of the filter means; and a sample for sampling and holding the control voltage in a predetermined section of the recording signal. A recording current control device comprising: a hold means; and a level control means for controlling the level of the recording signal according to the output of the sample hold means. 2. A recording current control device for a recording device that records information on a magnetic tape using a head, comprising: a detection means for detecting a voltage generated across the head;
filter means for extracting only a predetermined frequency band of the output of the detection means; generation means for generating a control voltage according to the level of the output of the filter means; and a sample for sampling and holding the control voltage in a predetermined section of the recording signal. A recording current control device comprising a hold means, a level control means for controlling the level of the recording signal according to the output of the sample hold means, and a storage means for storing the output of the sample hold means. . 3. A recording current control device for a recording device that records information on a magnetic tape using a head, the recording current control device comprising: a reference recording signal generating means for generating a reference recording signal; and detecting a voltage generated across the head. a rectifying means for rectifying the voltage detected by the detecting means;
A/D conversion means for digitizing the output of the rectifying means; comparison means for generating error data by comparing the digitized signal with reference data; storage means for storing the error data; 1. A recording current control device comprising: level control means for controlling the level of a recording signal according to error data stored in a storage means.