JPH04104691A - Signal processing circuit of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the power consumption in camera mode wherein the operation of a comb-shaped filter is not required by turning off power supply to the comb-shaped filter in the camera mode. CONSTITUTION:If a composition signal is inputted in recording mode, a power circuit 1 supplies electric power, so a delay line 2 and its peripheral circuits operate. In the camera input mode, the power circuit 1 which supplies the electric power to the delay line 2 and peripheral circuits stops supplying the electric power according to an input select signal. Consequently, the electric power consumed by the delay line 2 and its peripheral circuits is reducible and in the mode wherein the operation of the comb-shaped filter is not required, the power consumption of the comb-shaped filter part can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to recording of a comb filter, a dropout compensation circuit, and a feedback type line noise canceling circuit using a delay line (CCD) in a signal processing circuit of a magnetic recording/reproducing device. The present invention relates to a means for reducing power consumption at times.

[Conventional technology]

A conventional device, as described in Japanese Patent Application Laid-Open No. 63-308492, consists of a comb filter during recording, a dropout compensation circuit during playback, and a feedback line noise cancellation circuit in one delay line. Met. and,
In order to reduce power consumption, especially during recording and playback, the power supply to some of the comb filters is turned on.

It wasn't supposed to turn off.

[Problem to be solved by the invention]

The above-mentioned prior art does not take into consideration the power reduction of a portion of the comb filter in a mode in which the operation of a portion of the comb filter is not required.

An object of the present invention is to reduce the power consumption of a portion of the comb filter in a mode in which the operation of the portion of the comb filter is not required.

[Means to solve the problem]

In order to achieve the above object, a control switch is provided in a power supply circuit that supplies power to the delay line and peripheral circuits, so that power is not supplied when the delay line is not used.

[Effect]

During recording, when a composite signal is input, the power supply circuit supplies power, so the delay line and its peripheral circuits operate. Also, during camera input, the power supply circuit that supplies power to the delay line and peripheral circuits is in a mode that stops power supply based on the input selection signal, reducing the power consumed by the delay line and its peripheral circuits. can be reduced.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows a block diagram of a recording system in a signal processing circuit of a magnetic recording/reproducing apparatus according to the present invention. Second
The figure shows the internal circuit of the power supply circuit in FIG.

First, the operation will be explained using FIG. During recording, there are two modes: a mode in which the luminance signal and chrominance signal from the camera are input separately, and a composite video signal mode in which the luminance signal and chrominance signal are combined.

First, the separate input mode from the camera will be explained.

From the camera, a luminance signal is input from a luminance signal input terminal (16) and a color signal is input from a color signal input terminal (17). The brightness signal input from the brightness signal input terminal (16) is sent to the switch (
3) Enter. Switch (3) is the input selection signal input terminal (
18) is switched to select the (S) side based on the control signal input from step 18). Here, the control signal is set when the switch is turned on (
It becomes high level so that it connects to C) side. switch(
The luminance signal output from 3) enters the switch (4).

The switch (4) selects the (S) side by a control signal from an input selection signal input terminal (18). Switch (4)
The luminance signal from is sent to the next stage luminance signal recording processing circuit (19).
The signal is then subjected to emphasis processing, grip processing, and frequency modulation processing, and then enters the adder (13).

On the other hand, the color signal is input from the color signal input terminal (17) and input to the switch (5). The switch (5) is connected to the (S) side by a control signal from an input selection signal input terminal (18). The color signal output from the switch (5) enters the color signal recording processing circuit (20).

Here, the signal undergoes frequency conversion processing and enters the adder (13). The record luminance signal and record color signal are combined by an adder (13) and input to a record amplifier (21). Here, sufficient power is obtained to drive the magnetic head (22), and the magnetic head (22) is driven. The magnetic head (22) writes recording information onto the magnetic tape (23) to be recorded.

Next, a case where a composite video signal is input will be explained. In this case, input selection signal input terminal (18
), switch (3), switch (4)
and switch (5) are all connected to the (C) side. The composite video signal input from the composite video signal input terminal (15) enters the switch (3). The composite video signal output from switch (3) is sent to adder (11), subtracter (14) and delay line (2).
Enter. First, the video signal input to the delay line (2) is delayed by about one horizontal period by the delay line (2). The delayed video signal enters the LOF (6) where unnecessary signal components are removed. The video signal output from the LPF (6) enters an equalization circuit (EQ) (7).

The equalization circuit (8) here is a circuit that finely adjusts the adder (8) and subtracter (4) in the next stage to accurately delay one horizontal period. By adding and subtracting the video signal delayed by one horizontal period from the equalization circuit (7) and the video signal before being delayed, the video signal is separated into a luminance signal and a color signal. That is, the adder (11) outputs a luminance signal, and the subtracter (14) outputs a chrominance signal. The separated color signal from the subtractor (14) is B P F (10)
Unnecessary components are removed at , and the switch is turned on (5). The processing after the switch (5) is the same as in the separate input mode from the camera.The zero-order luminance signal from the adder (11) enters the equalization circuit (8). Also, a subtractor (14
) contains a low-frequency uncorrelated luminance signal in addition to the color signal, so the color signal component is removed by the trap circuit (9) in the next stage. The low-frequency uncorrelated luminance signal output from the trap circuit (9) is added to the luminance signal output from the equalization circuit (8) by an adder (12) to become a complete color signal and a separate luminance signal. and enter the next stage switch (4). The processing of the luminance signal output from the switch (4) is the same as in the separate input mode from the camera.The recording signal processing was explained by 0 or more.

Next, the operation of the power supply circuit (1) of the present invention will be explained. In Fig. 1, the input selection signal input terminal (18) has switch (3), switch (4), and switch (5) that can be switched between high level and low level in camera input mode and composite video signal input mode. ), but this control signal is set to low level only in recording mode and camera input mode.

This control signal is then input to the power supply circuit (1).

A power supply circuit (1) supplies power to a delay line (2) LPF (6) and an equalization circuit (7). and,
When the control signal from the input selection signal input terminal (18) becomes low level, that is, when the camera input mode is set, the power supply circuit turns off the power supply. This allows you to turn off the power supply to part of the comb filter in camera input mode that does not require the comb filter to operate.
F can do it.

Next, the operation of the power supply circuit (1) will be explained using FIG. 2. FIG. 2 shows the internal circuit of the power supply circuit (1). The power input terminal (25) is connected to the main power source of the magnetic recording/reproducing device. Here, when the control signal from the input selection signal input terminal (18) becomes high level, the transistor (27) is turned on, thereby
The base current of the transistor (26) flows, the transistor (26) is supplied with power from the ONL collector, the noise is removed by the coil (32) and the capacitor (33), and the above-mentioned comb shape is output from the power output terminal (24). Power is supplied to the filter circuit section. Also,
When the control signal from the input selection signal input terminal (18) becomes low level, the transistors (26) and (2
7) is turned off and power is not supplied. Here, resistance (28), resistance (29), resistance (30) and resistance (
31) is a voltage dividing resistor that determines the operating voltage of transistors (26) and (27).

According to this embodiment, since the power supply to the comb filter can be turned off in the camera input mode in which the comb filter does not require operation, there is an effect of reducing power consumption in the camera input mode.

Next, a second embodiment of the present invention will be described using FIGS. 3 and 4. FIG. 3 shows a block diagram of a second embodiment of the invention. FIG. 4 shows the internal circuit of the power supply circuit of the present invention. This embodiment differs from the first embodiment in that the delay line used in the comb filter circuit during recording is used as a color signal separation comb filter, dropout compensation circuit, and feedback line noise cancellation circuit during playback. It is. For this purpose, the power supply circuit (1
) is different in that a control signal from a preamplifier control terminal (55) is newly introduced.

Next, the operation will be explained using FIG. During recording, the operation is similar to that of the first embodiment except that the newly provided switch (34) is connected to the R side. During playback, magnetic tape (
The signal recorded on the magnetic head (23) is read out by a magnetic head (37) and amplified to a sufficient amplitude by a preamplifier (36). The video signal output from the preamplifier (36) is converted into a luminance signal component by the HPF (38).
The color signal component is extracted by F (39). HP
The luminance signal extracted by F (38) is FM demodulated and de-emphasized by a luminance signal reproduction processing circuit (40) and returned to a baseband luminance signal. The baseband luminance signal output from the luminance signal reproduction processing circuit (40) limits the noise in the color signal band by L P F (42), and then passes through an attenuator (52), an attenuator (54), and an adder (50). Enter. The adder (50) combines the color signal from the comb filter (45) and the LP F (42).
The luminance signals output from are added. The added signal is input to the switch (34), and since the switch (34) is connected to the P side, the input signal is output as is. The signal output from the switch (34) is sent to the delay line (2) L
P F (6) Almost 1 through equalizer (7)
After a horizontal period delay, switch (61), LP F (43
) and B P F (44).

First, the signal input to LPF (43) is
(43), the luminance signal is separated into (1) a luminance signal delayed by a horizontal period. The separated luminance signal is input to a subtracter (48). On the other hand, the undelayed luminance signal is level-adjusted by an attenuator (52) and enters a subtracter (48). Here, the signal output from the subtracter (48) is a signal without line correlation. This signal is input into a limiter (46), then an attenuator (53) to adjust the level, and an adder (49).
Enter. This activates the line noise cancellation circuit.

Next, the noise-free luminance signal outputted from the adder (49) is subjected to noise cancellation of small amplitude components in the horizontal direction by a noise cancellation circuit (47).

The luminance signal from which noise has been further removed is input to an adder (51). On the other hand, regarding the reproduced color signal, the reproduced signal output from the preamplifier (36) is L P
F (39), where the color signals are separated. LPF (
The reproduced color signal output from the color signal reproduction processing circuit (
41), and the frequency is converted by a comb filter (41).
5). The comb filter (45) is used to cancel signals from adjacent tracks picked up simultaneously during playback. In order to construct a comb filter, a signal delayed by a horizontal period is required, and in order to create the delayed signal, the color signal is input from the comb filter (45) to the adder (50). Adder (50)
At , the luminance signals are added and input to the switch (34). The operations of the next-stage delay line (2) LPF (6) and equalizer (7) are the same as those described for the luminance signal. The video signal delayed by one horizontal period from the equalizer (7) is input to the BPF (44), where color signal components are extracted. The color signal extracted by B P F (44) enters a comb filter (45) to constitute a comb filter circuit.

The color signal from which the crosstalk components of adjacent tracks have been removed is output from the comb filter (45) and sent to the adder (51).
)to go into. Here, the luminance signal and the color signal are added and output from the reproduced video signal output terminal (56).

Next, processing at the time of dropout will be explained. Dropouts are detected when the reproduced signal output from the preamplifier (36) enters a dropout detector (35). When a dropout is detected, a control signal is output from the dropout detector (36) and enters the switch (61). At the time of dropout, the switch (61) is connected to the Do side.

At this time, the IH-delayed signal is sent from the switch (61) to the P
F (42) and replace the line where dropout occurred with the line before IH. Here, the line noise canceling circuit does not operate because of line correlation.

Next, how the power supply circuit (1) works in this embodiment will be explained. The power supply circuit (1) is a circuit shown in FIG. The difference between the power supply circuit (1) and the power supply circuit of the first embodiment is that a transistor (59), a resistor (57), a resistor (58), and a diode (60) are newly added. The difference is that a preamplifier control terminal (55) is newly provided, and in addition to the operation of the first embodiment, when the preamplifier operates, the delay circuit operates.

According to this embodiment, in addition to the effects of the first embodiment, during reproduction, even when the delay line is used in the reproduction circuit as well as the recording circuit, the power supply to the delay line can be turned on as necessary.
It can be turned off and has the effect of saving power.

〔Effect of the invention〕

According to the present invention, in the signal processing circuit of a magnetic recording and reproducing device, power consumption can be reduced because the power supply to the delay line used in the comb filter circuit can be limited to only when necessary without significantly increasing the number of circuits. I can do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention, and FIG. 2 is a block diagram of a first embodiment of the present invention.
FIG. 3 is a block diagram showing a second embodiment of the present invention, and FIG. 4 is an internal circuit diagram of the power supply circuit in FIG. 2. 1... Power supply circuit 2... Delay line 3.4.5.
...Switch 6...LPF 7.8...Equalization circuit 15...Composite video signal input terminal 16...
- Luminance signal input terminal 17... Color signal input terminal 18... Input selection signal input terminal 55... Preamplifier control terminal 56... Playback video signal output terminal

Claims (1)

[Claims] 1. In a signal processing circuit of a magnetic recording and reproducing device having a recording and reproducing function and having an input terminal that handles a composite video signal during recording and a terminal that separately inputs a luminance signal and a color signal, When a power supply circuit is provided that can turn on and off the power supply to the comb filter circuit used to separate the video signal into a luminance signal and a chrominance signal, and the luminance signal and chrominance signal are separated and input based on the input selection signal. A signal processing circuit for a magnetic recording/reproducing device, characterized in that the power supply to the comb filter circuit is turned off at 2. In claim 1, the delay line used in the comb filter circuit constitutes a comb filter for separating luminance signals and chrominance signals during recording, and during reproduction, the luminance signal and the chrominance signal are superimposed and the delay line is When using this to configure a color signal separation comb filter, dropout compensation circuit, and feedback type line noise canceling circuit,
A signal processing circuit for a magnetic recording and reproducing device, which includes a power supply circuit that can turn on and off a power supply to the delay line, and turns off the power supply when a luminance signal and a color signal are input separately based on an input selection signal.