JP3372729B2 - Recording device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording device,
In particular, it relates to control of a recording current when a digital signal is recorded on a magnetic recording medium by a magnetic head.

[0002]

2. Description of the Related Art As a device for recording a signal on a recording medium,
A digital VTR that records and reproduces a digital signal on and from a magnetic tape by a magnetic head is known.

In such a digital VTR, "DCC LSI / IC", N is used as an example of a magnetic head drive circuit for controlling a recording current flowing to the head.
national Technical Report
Vol. 39 No. 6, a schematic circuit block diagram described in Dec. 1993 is shown in FIG.

In parallel with the power supply 210 of the output voltage Vcc, a series circuit of a switch 212 controlled by the output of the inverting circuit 225 and a first current source 214 which can be turned on / off, and a switch controlled according to recording data. A node 220 connecting a series circuit of 216 and a second constant current source 218 capable of turning on / off, and connecting a switch 212 and a constant current source 214,
Node 222 where switch 216 and constant current source 218 connect
The magnetic head 224 is connected between and.

FIG. 7 shows the correspondence between the values of digital data to be recorded and the switches 212 and 216 and the constant current sources 214 and 218. That is, in the circuit shown in FIG. 6, when the value to be recorded is “1”, the switch 212 is turned on, the switch 216 is turned off, the constant current source 214 is turned off, the constant current source 218 is turned on, and the constant current source 218 is turned on. Constant current due to
c is the power supply 210, the switch 212, the magnetic head 22.
4 and the constant current source 218 to the power supply 210. Therefore, in the magnetic head 224, the nodes 220 to 22
A current Ic flows toward 2.

On the contrary, when the value of the data to be recorded is "0", the switch 212 is turned off, the switch 216 is turned on, the constant current source 214 is turned on and the constant current source 218 is turned off. A constant current Ic from the power source 210
Switch 216, magnetic head 224 and point current source 214
Through to the power supply 210. Therefore, the magnetic head 22
A current Ic flows from No. 222 to No. 220 in No. 4.

If the current flowing through the magnetic head 224 in the direction from the node 220 to the node 222 is positive, statically, the current Irec flowing through the magnetic head 224 is + Ic when the data to be recorded is "1", and the data should be recorded. When the data is "0", the recording current Irec flowing through the magnetic head 224 becomes -Ic.

When a constant current flows through an inductive load such as the magnetic head 224, the following voltage e is generated between the terminals of the load with respect to changes in the flowing current i, as is well known. That is, e = -L (di / dt) [v]. However, L is the inductance of the load.

In the circuit shown in FIG. 6, the switches 212, 2
Assuming that 16 is ideal and the on-resistance is zero, a negative transient pulse voltage appears at the nodes 220 and 222, as shown in FIGS. 8B and 8C. .

FIG. 8 is a diagram showing the waveform of the recording current flowing through the magnetic head 224. In order to obtain a pulse voltage according to the inductance L of the magnetic head 224, the transmission rate of digital data to be recorded, and the magnitude of the recording current,
The output voltage Vcc of the power supply 210 must be selected.

For example, if the output voltage Vcc of the power source 210 is too low, the pulse voltage at the nodes 220 and 222 is too low and the recording current rises and falls, as shown in FIG. With this, normal magnetic recording cannot be performed.

[0012]

In recent years, a camera-integrated VTR in which a VTR and a video camera are integrated has rapidly spread, and it has become a common practice to easily record outdoors using a battery as a power source. When converting the VTR unit into a digital circuit, it is strongly required to reduce power consumption.

However, the magnetic head drive circuit as described above has the following problems.

That is, the high voltage for obtaining the pulse voltage required at the nodes 220 and 222 is the constant current source 214.
And 218 are always applied, and the power consumption in the constant current sources 214 and 218 is large.
As a result, the time that can be recorded in the case of battery driving is shortened.

Further, when the magnetic head drive circuit is formed on an integrated circuit, the current value of the constant current source changes due to a change in resistance value due to manufacturing variations, a change in power supply voltage and temperature, etc. There is also a problem that the recording current cannot be passed or the recording current is too large and errors occur when the recorded tape is reproduced, and the reproduced image becomes unsightly.

An object of the present invention is to eliminate the above-mentioned problems.

Another object of the present invention is to provide an apparatus which has lower power consumption and a stable recording current.

[0018]

SUMMARY OF THE INVENTION In order to solve the problems conventionally held and to achieve the above object, the present invention provides a first voltage source and a second voltage source having an output voltage higher than that of the first voltage source. Voltage source, a first current source having one end connected to the first voltage source and the other end connected to one terminal of the magnetic head, one end connected to the first voltage source and the other end connected to the first voltage source. A second current source connected to the other terminal of the magnetic head, and a third current capable of on / off control, one end of which is connected to the second voltage source and the other end of which is connected to one terminal of the magnetic head. Connected to one terminal of the magnetic head, and a fourth current source whose one end is connected to the second voltage source and the other end is connected to the other terminal of the magnetic head and whose on / off control is possible. The first switch and the second switch connected to the other terminal of the magnetic head. Switch means for switching the direction of the current flowing through the magnetic head by controlling according to the value of the data, and a first for controlling ON / OFF of the third current source according to the voltage of one terminal of the magnetic head. And a second control means for controlling ON / OFF of the fourth current source according to the voltage of the other terminal of the magnetic head.
And a current source stabilizing means for controlling the first current source, the second current source, the third current source, and the fourth current source according to the value of the current flowing through the magnetic head. .

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

First, the operation of the digital VTR as an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, the video signal input from the terminal 1 is converted into a digital signal in the A / D converter 2 and output to the DCT circuit 3. The DCT circuit 3 makes a discrete cosine transform (Discrete Cosine Transform) in block units with 8 pixels × 8 lines of this digital signal as one block.
ormation (DCT) processing to convert the data in the spatial domain into the data in the frequency domain and output the data to the quantization circuit 4.

An image signal in which the quantization amount is quantized by a predetermined quantization coefficient by a quantization circuit 4, a variable length encoding process such as Huffman encoding is performed by a variable length encoding circuit 5, and the amount of information is compressed. Is output to the error correction coding circuit 6.

The error correction coding circuit 6 adds parity data to the recording signal, performs error correction coding, and outputs it to the digital modulation circuit 7. The digital modulation circuit 7 performs a digital modulation process on the recording signal to suppress the direct current component and multiplexes a pilot signal component for tracking control during reproduction.

The modulated recording signal is output to the head drive circuit 8. The head drive circuit 8 supplies a current to the heads 12a and 12b according to a recording signal through the switch 9 as described later, and records the signal on the magnetic tape 14.

The heads 12a and 12b are the rotary drum 13
The tape 14 is alternately placed on the tape 14 with a phase difference of 180 °. The switch 9 is switched by the head switching signal generated by the head switching circuit 15 using the signal PG indicating the rotation phase of the drum.

Further, 10 is a voltage source of voltage Vcc1,
In addition to the recording current, it also serves as a drive power source for each circuit of the device. Reference numeral 11 is a voltage source of voltage Vcc2, which is used for controlling the recording current as described later.

Next, the head drive circuit in FIG. 1 will be described.

FIG. 2 is a block diagram showing the configuration of the head drive circuit 8 in FIG. 1 as an embodiment of the present invention.

In FIG. 2, 10 and 11 are the power supplies for the output voltages Vcc1 and Vcc2 as described above, and Vcc2.
> Vcc1. A series circuit of a constant current source 103 capable of ON / OFF control and a switch 110, which outputs a constant current Ic, is connected in parallel to the power source 10, and a constant current source 104 capable of ON / OFF control, which outputs a constant current Ic. And switch 1
11 series circuits are connected.

These switches 110 and 111 are controlled as described later by the recording data supplied to the terminal 113 in FIG.

A magnetic head 12a or 12b is connected between a node (or terminal) 107 connecting the constant current source 103 and the switch 110 and a node (or terminal) 108 connecting the constant current source 104 and the switch 111. (Note that
In FIG. 2, the inductance 109 will be described. )

Here, the node 10 in the switch 110
7, the other end different from 7, and the node 10 in the switch 111.
The other end different from 8 is connected at a node 114, and this node 1
A resistor 116 for current detection is connected between 14 and the ground.

The output of the power source 11 is supplied to the node 10 via a constant current source 102 capable of on / off control which outputs a constant current Ic.
7, and also connected to the node 108 via a constant current source 105 capable of ON / OFF control, which outputs a constant current Ic. The constant current control circuits 101 and 106 are configured to supply the constant current sources 102 and 105, respectively, according to the potentials of the nodes 105 and 108.
Control on / off.

FIG. 3 shows the switches 110 and 111 for the value of digital data input from the terminal 113 in FIG.
FIG. 3 is a diagram showing a correspondence of operations of constant current sources 103 and 104.

That is, in this embodiment, when the value of the digital data to be recorded supplied from the terminal 113 is "1", this data is inverted by the inverter 112 and supplied to the switch 110, and the switch 110 is turned off. Also, it is supplied to the switch 111 as it is, and the switch 111 is turned on. Then, the constant current source 103 is turned on and 104 is turned off, and the constant current Ic from the constant current source 103 flows to the power source 10 through the node 107, the head 109, the node 108 and the switch 111.

On the contrary, when the value of the data to be recorded is "0", the switch 110 is turned on and the switch 111 is turned off. Then, the constant current source 103 is turned off and 104 is turned on, and the constant current Ic generated by the constant current source 104 is
8, magnetic head 109, node 107 and switch 110
Through to the power supply 10. Therefore, the magnetic head 109
A current Ic flows from node 108 to node 107.

The operation up to this point is similar to that of the circuit shown in FIG. 6, and assuming that the current flowing through the magnetic head 109 in the direction from the node 107 to the node 108 is positive, statically the data to be recorded is " When it is "1", the recording current Irec flowing through the magnetic head 109 is + Ic, and when the data to be recorded is "0", the recording current Irec flowing through the magnetic head 108 is -Ic.

Next, the operation when the digital data to be recorded is inverted and the polarity of the recording current changes will be described with reference to FIG.

FIG. 4 is a diagram showing signal waveforms of respective parts of the circuit when digital data to be recorded is alternately inverted to "1", "0", "1", "0". 4A shows the recording current Irec, FIG. 4B shows the voltage of the node 107, FIG. 4C shows the voltage of the node 108, and FIG. 4D shows the output current value of the power supply 11.
(E) shows the output current value of the power supply 10.

When the digital data to be recorded supplied from the terminal 113 is changed and the recording current is reversed, the node 1
The pulse voltages required for 07 and 108 are shown in FIG.
As shown in (c) and (d), the power source 1 is in the positive direction.
It becomes higher than the output voltage Vcc1 of 0. This is because the power supply 11 has a higher output voltage than the power supply 10 and the power supply 1 when the recording current changes.
A current supply circuit 10 for supplying a current amount which is insufficient with only 0
This is because 1, 102, 105, 106 are provided.

That is, the constant current source control circuit 101 monitors the potential of the node 107, and turns on the constant current source 102 when the potential of the node 107 approaches Vcc1. As a result, the potential of the node 107 becomes a voltage obtained by subtracting the voltage drop of the constant current source 102 from the output voltage Vcc2 of the power supply 11 regardless of the voltage drop or the induced voltage of the magnetic head 109. The constant current source control circuit 106 operates in the same manner, and the potential of the node 108 is V
When approaching cc1, the constant current source 105 is turned on and the node 108
Of the constant current source 105 from the output voltage Vcc2 of the power source 11
It controls to the value which reduced the voltage drop of.

As shown in FIG. 4D, the power source 11 is in a period in which the recording current changes, that is, the data is "1" →
The current is supplied during the period in which "0" or "0" is reversed to "1", and the power supply 10 supplies the current during the other period as shown in FIG.

Since the digital data as recording data in the digital VTR usually does not invert bit by bit and has a random period, the power supply 10 mainly supplies the current required for recording in this embodiment. It will be.
Further, in this embodiment, the potentials of the nodes 107 and 108 can be increased by the power supply 11, so that the output voltage Vcc1 of the power supply 10 can be lowered as compared with the circuit of FIG.

Therefore, the power consumption at the time of recording data can be greatly reduced.

Further, as shown in FIG. 1, V of this embodiment is
In TR, the voltage source used in the head drive circuit is used in the circuits of the respective parts of the apparatus, so that lowering the voltage of the power supply 10 leads to further reduction in power consumption.

Further, in the present embodiment, the current detection resistor 116 made of a metal film resistor of several ohms provided outside the integrated circuit is provided to detect the magnitude of the recording current. Then, after being filtered by the current stabilizing circuit 115, it is fed back to the constant current sources 102 to 105 to control the recording current. Therefore, the recording current can be always maintained at the reference value, and the extreme increase and decrease of the recording current can be prevented.

FIG. 4 (f) is a diagram showing the state of the recording current flowing through the resistor 116. Since the current flowing through the resistor 116 is a mixture of the current flowing through the switch 110 and the current flowing through the switch 11, it is constant. It becomes the current Ic.

In the above embodiment, the nodes 107 and 1
The magnetic head 109 is specially connected to the terminal 08, but in a VTR, a rotary transformer is generally inserted therebetween. Even in that case, the operation is similar to that of the above-described embodiment.

Further, in the above-mentioned embodiment, the switch 110 is connected between the node 107 and the ground and the switch 111 is connected between the node 108 and the ground. Current source 103,
A constant current source capable of on / off control and having a current supply capacity higher than that of 104 may be used. Even in that case, the operation is similar to that of the above-described embodiment.

In the above-described embodiment, the digital data is recorded by selectively using the power supplies 10 and 11 having different output voltages. However, the above (Vcc2-Vcc1) = Vcc
A power supply having an output voltage of 3 and a power supply having the output voltage of Vcc1 are provided, and Vcc1 is used in a transient state in which data changes from "0" → "1" or "1" → "0".
In addition to the above power supply, a power supply of Vcc3 may be connected in series to drive one constant current source.

In this case, the configuration is as shown in FIG.

In FIG. 5, the switch control circuit 117,
Reference numeral 118 is a circuit for detecting the potentials of the nodes 107 and 108 and controlling the switch 119 when the recording data is "0" and "1", respectively.

That is, in FIG. 5, when the recording data is "1" and in a steady state, the switch control circuit 118
Connects the switch 119 to the ground side and drives the current source 103 with the voltage Vcc1.

In the transitional state when the recording data is switched from "0" to "1", the switch control circuit 1
18 connects the switch 119 to the power supply 15 side, and Vcc1 +
The current source 103 is driven by the voltage of Vcc3 = Vcc2.

When the record data is "0" and "1" →
When it is switched to “0”, similar processing is performed under the control of the switch control circuit 117. The operation of the current stabilizing circuit 116 is similar to that of the above-described embodiment.

As described above, also in the circuit shown in FIG. 5, the power consumption during recording can be reduced as in the circuit shown in FIG.

In each of the above-mentioned embodiments, the two magnetic heads 12 are used.
Although the circuits shown in FIGS. 2 and 5 are provided for a and b, respectively, the number of parts and the cost can be reduced by sharing the current detecting resistor 115 and the current stabilizing circuit 116 by each head. .

[0058]

As apparent from the above description, according to the present invention, the input digital data is recorded by driving the current source by the plurality of voltage sources having the output voltages different from each other according to the state of the input digital data. Therefore, the current source can be driven with a high output voltage only when a high pulse voltage is required, and the current source can be driven with a low output voltage in other periods. Therefore, power consumption during recording can be reduced.

Further, since the current source is controlled according to the value of the current flowing through the recording means, the recording current value can always be kept stable.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a digital VTR as an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a head drive circuit in FIG.

FIG. 3 is a diagram for explaining the operation of the circuit of FIG.

FIG. 4 is a diagram showing the state of the recording current and the voltage across the head of FIG.

5 is a diagram showing another configuration of the head drive circuit of FIG.

FIG. 6 is a diagram showing a configuration of a conventional head drive circuit.

FIG. 7 is a diagram for explaining the operation of the circuit of FIG.

FIG. 8 is a diagram showing a state of a recording current and a voltage across the head.

FIG. 9 is a diagram showing a state of a recording current and a voltage across the head.

[Explanation of symbols]

9 Head drive circuit 10 voltage source 11 voltage source

Claims (4)

(57) [Claims] 1. A first voltage source, a second voltage source having an output voltage higher than that of the first voltage source, one end of which is connected to the first voltage source and the other end of which is one of a magnetic head. A first current source connected to the terminal; a second current source having one end connected to the first voltage source and the other end connected to the other terminal of the magnetic head; and one end connected to the second voltage source. An ON / OFF controllable third current source connected to the magnetic head and the other end connected to one terminal of the magnetic head, and one end connected to the second voltage source and the other end connected to the other terminal of the magnetic head. An on / off controllable fourth current source, a first switch connected to one terminal of the magnetic head, and a second switch connected to the other terminal of the magnetic head. By controlling according to the value of digital data, the direction of the current flowing through the magnetic head is switched. Switch means for switching, first control means for on / off controlling the third current source in accordance with the voltage of one terminal of the magnetic head, and the first control means for controlling the third current source in accordance with the voltage of the other terminal of the magnetic head. No. 4 current source for controlling ON / OFF, and the first current source, the second current source, the third current source, and the fourth current according to the value of the current flowing in the magnetic head. And a current source stabilizing means for controlling the source. 2. The current source stabilizing means has another end different from a connection end of the first switch connected to the magnetic head, and another end different from a connection end of the second switch connected to the magnetic head. 2. The recording apparatus according to claim 1, further comprising a resistance unit connected between a contact point connected to and the ground, and controlling the value of the current flowing through the magnetic head by using the resistance unit. 3. A first voltage source, a second voltage source connected in series to the first voltage source, a current source for supplying a current to the magnetic head, and a value depending on the value of input digital data. A switch for switching the direction of the current flowing to the magnetic head, and driving the current source only by the first voltage source in response to the input digital data being in a steady state at a low level or a high level, and The first voltage source and the second voltage source are connected in series in response to the transition state of input digital data from a high level to a low level or a transition from a low level to a high level, and the first voltage source and the second voltage source are connected in series. A control means for driving the current source by the first voltage source and the second voltage source; and a current stabilizing means for controlling the current source according to the current value flowing in the magnetic head. That the recording device. 4. A first voltage source, a second voltage source connected in series with the first voltage source via a connection switch, a current source for supplying a current to a magnetic head, and an input digital signal. A changeover switch for changing the direction of the current flowing through the magnetic head according to the value of the data, and a connection switch that detects the terminal potential of the magnetic head and controls the connection switch to drive the current source only by the first voltage source. Alternatively, the first voltage source and the second voltage source may be connected in series to connect the first voltage source and the second voltage source.
And a current stabilizing unit that controls the current source according to the value of the current flowing through the magnetic head.