JPH04313802A - Analog signal recorder - Google Patents

Abstract

PURPOSE:To control the envelop waveform of an oscillation output at the time of the rise and at the time of the fall of a bias oscillating circuit for recording and an oscillating circuit for erasing with simple constitution. CONSTITUTION:A first variable resistance circuit 22 is inserted into the power supplying path of a bias oscillating circuit 21 for recording. A second variable resistance circuit 32 is inserted into the power supplying path of an oscillating circuit 31 for erasing. From a micro computer 40, each pulse signal for controlling as oscillating circuir set in accordance with the envelope waveform at the time of the rise and at the time of the fall of the oscillation output of the bias oscillating circuit 21 for recording and the oscillating circuit 31 for erasing is outputted to first and second integrating circuits 23 and 33. In first and second voltage comparing circuits 24 and 34, the power voltage given to each oscillating circuit and the output of the first and second integrating circuits are respectively compared and by the comparing output, the resistance value of first and second variable resistance circuits 22 and 32 is controlled.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog signal recording apparatus suitable for use, for example, in bias recording an analog audio signal in the longitudinal direction of a tape.

0002

2. Description of the Related Art For example, in a VTR, an analog audio signal is recorded as a longitudinal track by a fixed head at the end of a tape in the width direction using an AC bias method. The analog audio signal of this longitudinal track is also used for so-called after-recording and audio editing recording.

By the way, in the AC bias recording method, if the recording bias oscillation circuit and the erasing oscillation circuit are abruptly raised or lowered at the start and end of recording, when the recorded signal is reproduced, the so-called Pop noise will occur.

Therefore, in order to prevent this pop noise from occurring, the recording bias oscillation circuit and the erasing oscillation circuit are
The oscillation output amplitude is controlled by gradually raising it at the start of recording and gradually lowering it at the end of recording. In particular, when considering editing and recording, the envelope waveform of the oscillation output waveform at the start-up and fall times should be controlled more precisely to make the joints of audio signals less noticeable. ing.

Conventionally, methods for controlling waveforms at the time of rising and falling of the oscillation output of the recording bias oscillation circuit and the erasing oscillation circuit include: 1. A time constant circuit is provided in the power supply circuit section of each oscillator circuit to moderate DC voltage changes.
Method of turning off directly by system control signal 2. In this method, power is supplied to each oscillation circuit, and the ground side of the oscillation circuit is controlled by a variable resistance circuit consisting of a transistor circuit. A method has been used in which the transistor circuit is controlled by the integrated output.

FIG. 7 shows an example of this type of conventional circuit.
is a recording bias oscillation circuit. In this oscillation circuit 10, a push-pull oscillation output from a bias oscillator 11 is supplied to the bases of drive push-pull transistors 12 and 13, and an oscillation output is obtained from a terminal 14. +Vcc is a power supply.

[0007] Then, from the system control signal, a signal DW that falls from a high level to a low level at the start of recording is formed, and a signal UP that rises from a low level to a high level at the end of recording is formed, and these signals UP and DW are formed. is supplied to input terminal 15. The signal UP or DW passed through the input terminal 15 is inverted by the transistor 16 in the input stage, and is supplied to the base of the control transistor 19 through integration circuits 17 and 18 consisting of a plurality of stages, for example, two stages of CR time constant circuits. Integrating circuit 17
, 18 are used in multiple stages of time constant circuits 17 and 18 in order to finely control the envelope waveform at the rise and fall of the oscillation output.

In the above configuration, the transistor 19
The base potential of the oscilloscope is gradually increased by the integrating circuits 17 and 18 at the start of recording, and therefore the oscillation output amplitude obtained at the output terminal 14 gradually increases. Further, at the end of recording, the base potential of the transistor 19 gradually decreases, and the oscillation output amplitude obtained at the output terminal 14 gradually decreases accordingly.

[0009]

[Problems to be Solved by the Invention] In the conventional circuit configuration described above, as shown in FIG. In order to perform precise control taking this into consideration, a multi-stage integration circuit is required, which has the disadvantage of complicating the configuration.

Furthermore, in the conventional circuit configuration, since the time constant of the multi-stage integrating circuit can generally be selected in only one way, it is not possible to control the envelope waveform in accordance with the transition from various different modes of the VTR.

An object of the present invention is to provide an analog signal recording device that solves the above-mentioned drawbacks.

0012

[Means for Solving the Problems] An analog signal recording device according to the present invention, referring to the reference numerals in the embodiments described later, includes a recording bias oscillation circuit that obtains an oscillation output with an amplitude corresponding to the magnitude of the supplied power supply voltage. 21 and erasing oscillation circuit 31
, a first variable resistance circuit 22 inserted into the power supply path of the recording bias oscillation circuit 21, and an erasing oscillation circuit 31.
The second variable resistance circuit 32 inserted into the power supply path of Alternatively, a microcomputer 40 that obtains a recording bias oscillation circuit control pulse output and an erasing oscillation circuit control pulse output whose pulse width changes according to the envelope waveform at the time of falling, and a recording bias output from the microcomputer 40. A first integrator circuit 23 that integrates the oscillation circuit control pulse output, a second integrator circuit 33 that integrates the erase oscillation circuit control pulse output from the microcomputer 40, and a recording bias oscillation circuit 21. The power supply voltage is compared with the output of the first integrating circuit 23, and the resistance value of the first variable resistance circuit 22 is controlled based on the comparison output, thereby controlling the power supply voltage applied to the recording bias oscillation circuit 21. The first voltage comparison circuit 24 compares the power supply voltage applied to the erasing oscillation circuit 31 with the output of the second integration circuit 33, and controls the resistance value of the second variable resistance circuit 32 based on the comparison output. The second voltage comparison circuit 34 controls the power supply voltage applied to the erasing oscillation circuit 31.

[0013]

[Operation] The microcomputer 40 has a first or second
A recording bias oscillation circuit control pulse signal and an erasing oscillation circuit control pulse signal whose pulse width, frequency, etc. change so that when integrated by the integrating circuit, the pulse width and frequency become the envelope waveform of the desired rising or falling oscillation output. Signal data is stored. Alternatively, the microcomputer 40 is provided with a program that executes an operation of creating the control pulse signal and outputting it from the port when it receives recording start and recording end information.

When the microcomputer 40 receives the recording start and recording end information, it outputs the control pulse signal from the port from the recording start or recording end point. This pulse signal output is transmitted to the first and second integrating circuits 2, respectively.
3 and 33, and the first and second voltage comparison circuits 2
4 and 34, the voltages are compared with the power supply voltages of the recording bias oscillation circuit 21 and the erasing oscillation circuit 31, respectively. Based on the comparison output, the resistance values of the first and second variable resistance circuits 22 and 32 are controlled so that each power supply voltage corresponds to the output of the integrating circuits 23 and 33.

The outputs of the first and second integrating circuits 23 and 33 are appropriately set as envelope waveforms at the rise or fall of the oscillation output of each oscillation circuit 21 and 31, so that each oscillation The envelope waveform at the rise or fall of the oscillation output of the circuit becomes the desired one.

[0016]

[Embodiment] The analog signal recording device according to the present invention is
An explanation will be given below, taking as an example a case in which the present invention is applied to a device that records audio signals as longitudinal tracks on a tape in TR.

In FIG. 1, 21 is a recording bias oscillation circuit, and 31 is an erasing oscillation circuit. These oscillation circuits 2
1 and 31 output an oscillation output with an amplitude corresponding to the magnitude of the supplied power supply voltage.

Variable resistance circuits 22 and 32 are inserted into the power supply paths to these oscillation circuits 21 and 31. In the example shown in the figure, the power supply terminal 20 from which a positive DC voltage +Vcc is obtained
Variable resistance circuits 22 and 32 are connected between the power supply line of each oscillation circuit 21 and 31, and the output voltage of the variable resistance circuit 22 and 32 is connected as a power supply voltage to each oscillation circuit 21 and 3.
1 is supplied. These variable resistance circuits 22 and 32
has a resistance value that changes depending on the control voltage supplied to its control terminal G, and can be constructed of, for example, an FET or a transistor.

Reference numeral 40 denotes a microcomputer which, for example, when a signal ST indicating the start and end of recording is supplied from the system control through a terminal 41, outputs a pulse signal P1 for controlling the oscillation output of the recording bias oscillation circuit 21 and an erase signal ST. Pulse signal P2 for controlling the oscillation output of the oscillation circuit 31
are output from each port. In this case, the output timing of the pulse signals P1 and P2 is determined by the erasing head and the output timing of the pulse signals P1 and P2.
The arrangement positional relationship with the audio recording head is taken into consideration, and the arrangement is made different as necessary.

Pulse signals P1 and P2 are created as follows. For example, the data buffer memory of the microcomputer 40 stores the pulse signals P1 and P1.
2 data is stored, and the microcomputer 4
0, when it is detected that the signal ST indicates the start of recording, pulses for controlling the rise of the oscillation output of each oscillation circuit 21 and 31 are read out from the memory as pulse signals P1 and P2, respectively. Output from the port. Further, when the microcomputer 40 detects that the signal ST indicates the end of recording, the microcomputer 40 sends falling control pulses of the oscillation outputs of the oscillation circuits 21 and 31 to the memory as pulse signals P1 and P2, respectively. and output from each port.

Alternatively, the data of the pulse signals P1 and P2 may be stored in the microcomputer 4 without being stored.
0, when it is detected that the signal ST indicates the start of recording, or when it is detected that the signal ST indicates the end of recording, a rising control pulse or a falling control pulse is created. Alternatively, a program may be executed to output the generated pulse signals P1 and P2 from the ports.

The control pulse signals P1 and P2 outputted from the microcomputer 40 are supplied to integration circuits 23 and 33, respectively, consisting of, for example, a resistor and a capacitor, and are integrated. The integrated outputs of the integrating circuits 23 and 33 are then supplied to voltage comparing circuits 24 and 34 as reference voltages for comparison. The voltage comparison circuits 24 and 34 are supplied with the output voltages of the variable resistance circuits 22 and 32, and
Compared to the integrated output voltage. The comparison output signals of the voltage comparison circuits 24 and 34 are supplied to the control terminals G of the variable resistance circuits 22 and 32, respectively.
The resistance values of the variable resistance circuits 22 and 32 are controlled so that the output voltages of the variable resistance circuits 2 and 32 correspond to the integrated output voltages of the integration circuits 23 and 33.

In this case, the integral output waveform of the pulse signals P1 and P2 output from the microcomputer 40 corresponds to the envelope of the power supply voltage at the rise or fall of the recording bias oscillation circuit 21 and the erasing oscillation circuit 31. The waveform is set to correspond to an appropriate waveform. That is, pulse signals P1 and P
The pulse width, frequency, duty, etc. of No. 2 can be changed according to the change in the envelope waveform.

For example, the microcomputer 40 is used to control the falling edge of the recording bias oscillation circuit 21.
From this, a pulse signal P1 as shown in FIG. 2A is obtained. This pulse signal P1 is integrated by the integrating circuit 23, and an integrated output as shown in FIG. 2B is obtained. Therefore, by controlling the resistance value of the variable resistance circuit 22 by the voltage comparator circuit 24, the output voltage of the variable resistance circuit 22, that is, the power supply voltage of the recording bias oscillation circuit 21, corresponds to the integral output, as shown in FIG. 2C. Become something. Therefore, the envelope waveform of the oscillation output from the recording bias oscillation circuit 21 becomes an appropriate falling waveform whose amplitude gradually decreases, as shown in FIG. 2D.

FIG. 3 shows a specific circuit example of the control circuit portion of the recording bias oscillation circuit 21. In this example, the recording bias oscillation circuit 21 is configured such that the push-pull oscillation output from the bias oscillator 210 is transmitted to the drive push-pull transistors 211 and 21, as in the conventional example shown in FIG.
2, and an oscillation output is obtained from a terminal 213.

The variable resistance circuit 22 also includes an FET 220
The drain and source of this FET 220 are connected between the power supply terminal 20 and the power supply line of the recording bias oscillation circuit 21. The comparison output of the voltage comparison circuit 24 is supplied to the gate of this FET.

The voltage comparison circuit 24 also includes the differential amplifier circuit 2.
40, the output voltage of the variable resistance circuit 22 is resistively divided and supplied to one input terminal of this differential amplifier circuit 240, and the integrated output of the integrating circuit 23 is supplied to the other input terminal. Ru.

The integrating circuit 23 includes resistors 231,
232 and a capacitor 233.

As described above, according to the present invention, fine waveform control can be performed using a microcomputer and a first-order integrating circuit, so the hardware configuration can be simplified and space can be saved.

Since a plurality of types of waveform control can be performed with the same configuration, optimum waveform control can be performed when the VTR shifts to various modes. Furthermore, waveform control can be changed simply by changing the microcomputer software (pulse signal generation program).

FIG. 4 shows another example of the present invention.
In the figure, only the control circuit portion for the recording bias oscillation circuit 21 is shown.

In this example, two pulse signals P11 and P12 are output from the port of the microcomputer 40 as control pulses for the recording bias oscillation circuit 21. Then, these two pulse signals P11 and P12
is supplied to the integrating circuit 23. This integrating circuit 23 is composed of resistors 234 and 235 and a capacitor 236, and outputs an integrated output obtained by combining pulse signals P11 and P12 to the voltage comparator circuit 24.

For example, taking the control at the time of falling of the recording bias oscillation circuit 21 as an example, the microcomputer 40 outputs a pulse signal P11 as shown in FIG. 5A,
The pulse signal P12 as shown in FIG. 5B is connected to the integrating circuit 23.
5C from this integrating circuit 23 and integrated.
An integral output is obtained which is a combination of the integral outputs of both pulses P11 and P12 as shown in FIG. Then, by controlling the resistance value of the variable resistance circuit 22 by the voltage comparison circuit 24, the power supply voltage of the recording bias oscillation circuit 21, which is the output voltage of the variable resistance circuit 22, becomes as shown in FIG. 5D. Therefore, the envelope waveform of the oscillation output from the recording bias oscillation circuit 21 becomes an appropriate falling waveform whose amplitude gradually decreases, as shown in FIG. 5E.

In this way, by outputting a plurality of types of pulse signals from the microcomputer 40 and composing them in the integrating circuit, compared to the integral output when one type of pulse signal is integrated, The integral output waveform can be controlled more precisely.

FIG. 4 shows still another example of the present invention, in which only the control circuit portion for the recording bias oscillation circuit 21 is shown.

In this example, the microcomputer 40 has a built-in D/A converter. Internal data buffers 401 and 402 store digital data of pulse signals P1 and P2, for example.
Equipped with When the signal ST input to the microcomputer 40 from the terminal 41 indicates the start or end of recording, the microcomputer 40 receives data from the internal data buffers 401 and 402 for rising control or falling control. Read pulse data and use built-in D/A converters 403 and 404, respectively.
Convert it to an analog waveform and output it. Then, an analog signal for controlling the recording bias oscillation circuit 21 from the built-in D/A converter 403 is supplied to the voltage comparison circuit 24 as a reference voltage.

In this example, an integrating circuit is not required, and the circuit configuration can be further simplified. Note that in this example as well, the pulses P1 and P2 are controlled by the program.
It is possible to form a configuration in which the signals are sequentially converted into analog signals by a built-in D/A converter and output.

In the circuit example shown in FIG. 3, the variable resistance circuit is constructed of FETs, but transistors may also be used. Further, the variable resistance circuit may be provided on the ground side of the oscillation circuit.

[0039]

Effects of the Invention As explained above, according to the present invention, detailed waveform control can be performed by using a microcomputer.
Since this can be done using the following integration circuit, the hardware configuration can be simplified and space can be saved.

Since a plurality of types of waveform control can be performed with the same configuration, optimum waveform control can be performed when the VTR shifts to various modes. Furthermore, waveform control can be changed simply by changing the microcomputer software.

Furthermore, when a microcomputer with a built-in D/A converter is used, an integrating circuit is not required, and the configuration can be further simplified.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an example of essential parts of the present invention.

FIG. 2 is a diagram showing output waveforms of each part in the example of FIG. 1;

FIG. 3 is a diagram showing a specific example of a part of the circuit shown in FIG. 1;

FIG. 4 is a block diagram of main parts of another example of the invention.

FIG. 5 is a diagram showing output waveforms of each part in the example of FIG. 4;

FIG. 6 is a block diagram of main parts of still another example of the present invention.

FIG. 7 is a block diagram of an example of a conventional device.

[Explanation of symbols]

20 Power terminal 21 Recording bias oscillation circuit 22 Variable resistance circuit 23 Integral circuit 24 Voltage comparison circuit 31 Erase oscillation circuit 32 Variable resistance circuit 33 Integral circuit 34 Voltage comparison circuit 40 Microcomputer

Claims (2)

[Claims] 1. A recording bias oscillation circuit and an erasing oscillation circuit that obtain an oscillation output with an amplitude corresponding to the magnitude of the supplied power supply voltage, and a recording bias oscillation circuit and an erasing oscillation circuit that are inserted into a power supply path of the recording bias oscillation circuit. a second variable resistance circuit inserted into the power supply path of the erasing oscillation circuit; A microcontroller that obtains a pulse output for controlling the recording bias oscillation circuit and a pulse output for controlling the erasing oscillation circuit, which are set in accordance with envelope waveforms at the rise or fall of the oscillation outputs of the oscillation circuit and the erasure oscillation circuit. a computer; a first integrating circuit that integrates the recording bias oscillation circuit control pulse output from the microcomputer; and a second integrating circuit that integrates the erasing oscillation circuit control pulse output from the microcomputer. The power supply voltage applied to the recording bias oscillation circuit is compared with the output of the first integrating circuit, and the resistance value of the first variable resistance circuit is controlled based on the comparison output, and the recording bias is A first voltage comparator circuit that controls the power supply voltage applied to the oscillation circuit compares the power supply voltage applied to the erasing oscillation circuit with the output of the second integration circuit, and uses the comparison output to An analog signal recording device comprising: a second voltage comparator circuit that controls a power supply voltage applied to the erasing oscillation circuit by controlling a resistance value of a variable resistance circuit. 2. A recording bias oscillation circuit and an erasing oscillation circuit that obtain an oscillation output with an amplitude corresponding to the magnitude of the supplied power supply voltage, and a recording bias oscillation circuit and an erasing oscillation circuit that are inserted into a power supply path of the recording bias oscillation circuit. a second variable resistance circuit inserted into the power supply path of the erasing oscillation circuit, and an envelope waveform at the rising or falling edge of the recording bias oscillation circuit and the erasing oscillation circuit; and a D/A converter for D/A converting the envelope waveform data from the storage section, the recording bias oscillation circuit receives recording start and recording end information, and operates the recording bias oscillation circuit from the recording start or recording end point. a microcomputer that outputs analog data of a control envelope waveform and an envelope waveform for controlling the erasing oscillation circuit; a power supply voltage applied to the recording bias oscillation circuit; and an envelope for controlling the recording bias oscillation circuit from the microcomputer. a first variable resistance circuit that controls a power supply voltage applied to the recording bias oscillation circuit by comparing the waveform with the first variable resistance circuit and controlling the resistance value of the first variable resistance circuit based on the comparison output;
The voltage comparison circuit compares the power supply voltage applied to the erasing oscillation circuit with the erasing oscillation circuit control envelope waveform from the microcomputer, and determines the resistance value of the second variable resistance circuit based on the comparison output. control the
and a second voltage comparison circuit that controls a power supply voltage applied to the erasing oscillation circuit.