JPH0762886B2 - Flying erase circuit of magnetic recording / reproducing apparatus - Google Patents

Description

The present invention relates to a flying erase circuit of a magnetic recording / reproducing apparatus (hereinafter referred to as VTR), and more specifically,
High-band mode camera-integrated VTR, stationary V
It is about TR.

[Conventional technology]

VTR compatible with high-band mode such as S-VHS (trademark) method
Records video signals in the frequency band of approximately 30 Hz to 10 MHz. At this time, the video signal is recorded separately as a luminance signal and a chroma signal (color signal).

By the way, in a standard mode such as the VHS (trademark) system, a luminance signal is converted into an FM signal having a carrier frequency of 3.4 MHz to 4.4 MHz and recorded. In the S-VHS (trademark) system, the luminance signal is converted into an FM signal having a carrier frequency of 5.4 MHz to 7.0 MHz and recorded. On the other hand, both the color signal, the VHS (trademark) system, and the S-VHS (trademark) system are low-frequency converted and recorded at a conversion frequency of 629 kHz.

In the VTR (first conventional technique) compatible with the S-VHS (trademark) system, when recording a recording signal, the flying erase circuit is driven prior to the recording. The oscillation frequency of the conventional flying erase circuit is set near 8 MHz, which is separated from the above FM signal (carrier frequency is 3.4 MHz to 4.4 MHz), and as shown in FIG. Care is taken not to generate chroma signals and beats.

Further, a magnetic recording device which records an FM modulated signal and is provided with an erasing head prior to the recording head is disclosed in, for example, Japanese Patent Laid-Open No. 1-312705.
Japanese Unexamined Patent Application Publication No. JP-A No. 2004-242242 (second prior art). According to this, the carrier frequency of the FM modulation signal can be switched, and
The frequency of the erasing signal supplied to the erasing head preceding the modulation signal recording head can be switched according to the carrier frequency. Therefore, the erase signal can be set to a signal in a band that is not used for FM demodulation regardless of the carrier frequency of the FM modulated signal, and adverse effects on the recording signal due to the erase signal can be avoided.

[Problems to be Solved by the Invention]

However, in the high-resolution VHS (trademark) system of the first prior art (hereinafter, simply referred to as S-VHS (trademark) system), the carrier frequency of the FM signal is set as high as 5.4 MHz to 7.0 MHz. At the oscillation frequency (about 8 MHz) of the conventional flying erase circuit described above, as shown in FIG. 4, the frequency is very close to the frequencies of the FM carrier and the chroma signal, so that beats may occur.

Further, at the oscillation frequency of the conventional flying erase circuit, there is a problem that the erase rate of the signal to be erased is low because the erase current is small at the time of erase in the S-VHS (trademark) mode.

On the other hand, in the configuration of the second conventional technique, only the frequency of the erase current is changed according to the carrier frequency, and neither the amplitude nor the frequency of the erase current is changed. In addition, since the frequency of the erasing current cannot be set near the resonance frequency, the amplitude of the erasing current cannot be largely changed, and thus the erasing rate of the magnetic signal to be erased cannot be significantly improved. ing.

[Means for Solving the Problems]

In order to solve the above problems, the flying erase circuit of the magnetic recording / reproducing apparatus according to the present invention takes the following means in the flying erase circuit of the magnetic recording / reproducing apparatus for erasing the recording signal on the magnetic recording medium.

That is, the above-mentioned flying erase circuit is for selecting a high band mode or a standard mode and generating an oscillation output signal having an oscillation frequency different for each selected mode. , An oscillating output signal generating means for generating an oscillating output signal having an oscillating frequency near the resonance frequency in the high band mode, and an erasing current generating for generating an erasing current whose frequency and amplitude both change according to the oscillating output signal. Means and magnetic erasing means for erasing the recording signal by recording a magnetic signal that changes according to the erasing current on a magnetic recording medium.

[Work]

According to the above configuration, when recording a recording signal on the magnetic recording medium, either one of the high band mode and the standard mode is selected via the mode selecting means prior to recording. When the mode is selected, the oscillation output signal having the oscillation frequency different for each mode is generated by the oscillation output signal generating means. The erasing current generating means generates an erasing current whose frequency and amplitude both change according to the oscillation output signal and sends it to the magnetic erasing means. At this time, in the high band mode, the oscillation frequency of the oscillation output signal is set near the resonance frequency, so that the amplitude of the erase current increases accordingly. A magnetic signal that changes according to the erasing current is recorded on the magnetic recording medium by the magnetic erasing means, and the previously recorded recording signal is erased.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

As shown in FIG. 1, a flying erase circuit of a magnetic recording / reproducing apparatus according to the present invention includes an oscillation circuit section 1 (oscillation output signal generating means), a driver circuit section 2 (erasing current generating means), and a rotary transformer 3 (erasing). The current generation means), the flying erase head 4 (magnetic erase means), and the high band mode determination switch 5 (mode selection means).

When recording the recording signal, the oscillation circuit unit 1 outputs an oscillation output signal having a different oscillation frequency to the driver circuit unit 2 described below for each selected mode. Oscillation circuit section 1
As shown in FIG. 1, is a transistor 6, resistors 13 to 16,
Coil 7 and capacitor 8 for determining the oscillation frequency
It consists of ~ 12.

Between the power supply voltage V _CC and the ground, a capacitor 9, a capacitor 8, a coil 7, and a capacitor 10 are connected in series from the power supply voltage V _CC side. One end of a capacitor 11 connected in parallel with the capacitor 10 is connected to a connection point B between the coil 7 and the capacitor 10 when a standard mode such as the VHS (trademark) method is selected. Capacitor 11
The other end of is connected to a common terminal of a high band mode discrimination switch 5 as a mode selecting means described later.
The contact 5a of the switch 5 is connected to the ground, and the contact 5b of the switch 5 is open without being connected to any of them.

When the high band mode such as the S-VHS (trademark) method is selected, the high band mode determination switch 5 is switched to the contact 5b. Then, the oscillation output signal which is the output of the oscillation circuit section 1 has an oscillation frequency determined by the following equations (1) to (3).

(Ω _S ) ² = (1 / L) × C _S … (1) C _S = [(1 / C ₈ ) + (1 / C ₉ ) + (1 / C ₁₀ )]… (2) ω _S = 2πf _S (3) where f _S represents the oscillation frequency of the oscillation output signal in the high band mode, and C _{8 to} C ₁₀ are the capacitors 8 respectively.
Represents a capacitance of ˜10 and L represents the inductance of the coil 7.

On the other hand, when the standard mode is selected, the high band mode determination switch 5 is switched to the contact 5a, and the oscillation output signal comes to have the oscillation frequency determined by the following equations (4) to (7).

ω ² = (1 / L) × C (4) C = [(1 / C ₈ ) + (1 / C ₉ ) + (1 / C _V )] (5) C _V = C ₁₀ + C ₁₁ … (6) ω = 2πf (7) However, f represents the oscillation frequency of the oscillation output signal in the standard mode, and C ₁₁ represents the capacitance of the capacitor 11.

As is clear from the above (1) to (7), the oscillation frequency f _S in the high band mode is higher than the oscillation frequency f in the standard mode because the capacitor 11 is not provided.

The connection point A between the coil 7 and the capacitor 8 is connected to the base of the transistor 6. The connection point A is connected to the power supply voltage V _CC via the resistor 14. Between the connection point A and the ground, a resistor 13 is provided in order from the connection point A side.
And the capacitor 12 are connected in series. The collector of the transistor 6 is connected to the ground, and the transistor 6
The emitter of is connected to the connection point between the capacitors 8 and 9. Further, a resistor is sequentially provided between the emitter of the transistor 6 and the power supply voltage V _CC from the power supply voltage V _CC side.
15 and the resistor 16 are connected in series.

The driver circuit unit 2 drives a rotary transformer 3 described later based on the oscillation output signal from the oscillation circuit unit 1,
It is provided on the secondary side to output an erase current having different frequency and amplitude. The circuit section 2 is composed of a transistor 17 and a resistor 18. Transistor
The base of 17 is connected to the connection point between the resistor 15 and the resistor 16 in the oscillation circuit unit 1. The emitter of transistor 17 is
It is connected to the power supply voltage V _CC through the resistor 18.

The collector of the transistor 17 is connected to the primary side of the rotary transformer 3 at one end, and the other end of the transformer 3 is connected to the ground. The rotary transformer 3 is provided for inducing an erasing current for erasing the magnetic signal on the recording medium on the secondary side of the transformer 3 in accordance with the output of the driver circuit unit 2. The erase current differs in frequency and amplitude for each mode, and is set to have a higher frequency and a larger amplitude in the high band mode.

The secondary side of the rotary transformer 3 is connected to both ends of the coil of the flying erase head 4 as a magnetic erasing means. The head 4 is a rotary transformer 3 2
A magnetic signal on the magnetic recording medium is erased prior to recording when the recording signal is recorded by the erase current induced on the next side.

According to the above configuration, when the high band mode or the standard mode is selected, (1) to
As shown in the equation (7), the oscillation output signal having the oscillation frequency different for each mode is output. In other words, the oscillation frequency f _S in the high band mode such as S-VHS (trademark) method is
It is set higher than the oscillation frequency f in the standard mode such as the VHS (trademark) method. Then, the driver circuit unit 2 is driven by the oscillation output signal for each mode. Depending on the output current of the driver circuit unit 2, the rotary transformer 1
The next side is excited. Along with this, an erase current is induced on the secondary side of the transformer 3. Erase current is high band mode (S-VHS (trademark) mode) as shown in FIG.
The time is larger than that in the standard mode (VHS (trademark) mode). This is because, as shown in FIG. 2, the oscillation frequency in the high band mode (S-VHS (trademark) mode) is higher than that in the standard mode (VHS (trademark) mode). This is because it is close to the resonance frequency.

Then, the erase current is output to the coil of the flying erase head 4 and electromagnetically converted by the head 4,
It is recorded on the recording medium. Along with this, the magnetic signal existing on the recording medium is erased by an erasing current whose frequency and amplitude are different for each selected mode, so that the recording area on the recording medium becomes a clean state, High-quality recording is possible.

〔The invention's effect〕

The flying erase circuit of the magnetic recording / reproducing apparatus according to the present invention has the mode selecting means for selecting one of the high band mode and the standard mode and the different oscillation frequency for each selected mode as follows. An oscillation output signal generating means for generating an oscillation output signal, the oscillation output signal generating means generating an oscillation output signal having an oscillation frequency near a resonance frequency in a high-band mode, and both the frequency and the amplitude according to the oscillation output signal. A structure comprising erase current generating means for generating a varying erase current and magnetic erase means for erasing the recording signal by recording a magnetic signal varying according to the erase current on a magnetic recording medium. Is.

Therefore, the oscillation frequency of the flying erase circuit can be set higher in the high band mode than in the standard mode. Therefore, in the high band mode, it is possible to avoid the occurrence of beats due to the close proximity of the carrier frequency of the FM signal and the oscillation frequency.

Further, in the high band mode, the oscillation frequency can be set near the resonance frequency, so that the amplitude of the erase current can be largely changed.

In addition, since both the frequency and the amplitude of the erasing current are changed, the erasing rate for erasing the magnetic signal on the recording medium is significantly improved.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a diagram showing a circuit configuration of a flying erase circuit of a magnetic recording / reproducing apparatus according to the present invention, and FIG. 2 is a flying erase. FIGS. 3 and 4 show a conventional example, FIG. 3 shows a frequency spectrum of a recording signal in a standard mode, and FIG. 4 shows a high band. It is a figure which shows the frequency spectrum of the recording signal in mode. 1 is an oscillation circuit section (oscillation output signal generation means), 2 is a driver circuit section (erase current generation means), 3 is a rotary transformer (erase current generation means), 4 is a flying erase head (magnetic erase means), and 5 is high. It is a band mode determination switch (mode selection means).

Claims (1)

[Claims] 1. A flying erase circuit of a magnetic recording / reproducing apparatus for erasing a recording signal on a magnetic recording medium, comprising mode selecting means for selecting one of a high band mode and a standard mode. An oscillation output signal generating means for generating an oscillation output signal having an oscillation frequency different for each mode, wherein the oscillation output signal generating means generates an oscillation output signal having an oscillation frequency near the resonance frequency in the high band mode; Erasing current generating means for generating an erasing current whose frequency and amplitude both change correspondingly, and a magnetic signal for erasing the above recording signal by recording a magnetic signal which changes according to the above erasing current on a magnetic recording medium. A flying erase circuit of a magnetic recording / reproducing apparatus, comprising: an erasing unit.