KR900007910Y1 - Head speed control circuit - Google Patents

Abstract

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Description

Drum speed control circuit during video search

1 is a conventional drum speed control circuit diagram.

Figure 2 is a detailed view showing an embodiment of the drum speed control circuit of the present invention.

* Explanation of symbols for main parts of the drawings

2: comparison unit 11: forward search control unit

12: reverse search control unit DAFC: drum automatic frequency control circuit

DAPC: Drum Auto Phase Control Signal RFF: Reel Fast Forward Signal

RREW: Reel Rewind Signal SEA: Search Control Signal

The present invention relates to a drum speed control circuit during image search for controlling the driving speed of the drum motor when searching for a playback image while driving a video tape at high speed such as forward search and reverse search.

In the conventional video tape recorder, the drum motor for rotating the drum is driven at a constant speed regardless of the operation mode.

That is, in the drum speed control circuit used in the conventional video tape recorder, as shown in FIG. 1, the microcomputer 1 pulse-width modulates the drum speed frequency signal which detects the drum rotation speed, and thereby the drum automatic frequency control signal. Outputs to the DAFC and outputs the drum driving reference signal as the drum automatic phase control signal DAPC, and the two control signals DAFC and DAPC outputted are the resistors R1 and R2 and the capacitor C1. ), And a filter composed of resistors R3 and R4 and capacitors C2 and C3, respectively, to the inverting input terminal (-) and the non-barrier force terminal (+) of the operational amplifier OP of the comparator 2, respectively. After input and speed comparison, it outputs the driving signal of the drum motor to drive the drum motor at a constant speed.

However, in the conventional drum speed control circuit as described above, the speed of the drum is controlled in the constant speed playback mode. In the video search mode, the color of the reproduced video signal is pushed at the lowest speed, so that the playback screen does not appear normally. In addition, when controlling the driving speed of the video tape by using a reel motor, there was a problem in that the phase control was not performed due to the characteristics of the reel motor, and the synchronization was broken at the beginning of the mode switching, and the playback screen did not appear.

The present invention devised a drum speed control circuit for controlling the rotational speed of the drum according to the image search mode of the forward search and the reverse search in order to solve the conventional problems as described above with reference to the accompanying drawings of FIG. When described in detail as follows.

2 is a detailed view showing an embodiment of the drum speed control circuit of the present invention, as shown therein, comparing the drum automatic frequency control signal (DAFC) and the drum automatic phase control signal (DAPC) output from the microcomputer (1) In the drum speed control circuit in which the section 2 compares and outputs the drive signal of the drum motor, the level of the drum automatic frequency control signal DAFC input to the comparing section 2 according to the reel fast-forward signal RFF. The drum search inputted to the comparator 2 according to the forward search control section 11 comprising resistors R11-R13 and transistors TR11 and a reel rewind signal RREW and search control signal SEA. The reverse search controller 12 includes resistors R14-R19, transistors TR12-TR14, an inverter IV, and a diode D for increasing the level of the frequency control signal DAFC.

The search control signal (SEA) is a video search mode, that is, a high potential is input during the forward search and the reverse search, the reel fast forward signal (RFF) and the reel rewind signal (RREW) is high during the forward search and reverse search, respectively The above is entered.

In the description of the drawings, reference numeral Vcc denotes a power supply terminal.

According to the present invention, the microcomputer 1 drives the drum automatic frequency control signal (DAFC) and the drum automatic phase control signal (DAPC) as in the case of driving the drum motor while the operating power is applied to the power terminal (Vcc). ), And the output control signals DAFC and DAPC are compared with each other through a filter consisting of resistors R1 and R2 and capacitor C1, resistors R3 and R4 and capacitors C2 and C3. It is inputted to (2) and compared, and outputs a drum motor drive signal to drive the drum motor.

In this state, when the high-speed reel fast-winding signal RFF is input by the forward search, the transistor TR11 of the forward search control unit 11 is turned on, so that the resistor R13 is equivalent through the transistor TR11. Grounded.

Accordingly, the level of the drum automatic frequency control signal DAFC connected to the inverting input terminal (-) of the operational amplifier OP by the resistor R13 is lowered, which causes the drum motor that the operational amplifier OP outputs. As the level of the driving signal increases, the driving speed of the drum motor is increased, and the drum rotates at a high speed.

At this time, the search control signal SEA is also supplied with a high potential, the transistor TR12 is turned on, the transistor TR13 is turned on, and the operating power supply of the power supply terminal Vcc passes through the resistor R18, and the transistor TR13 is turned on. Is applied to the emitter of the transistor TR14, but the reverse search signal RREW is input at a low potential, and the low potential is applied to the base of the transistor TR14 after being inverted to a high potential through the soft butter IV. Since it is off, the reverse search control unit 12 does not output any potential.

On the other hand, in the reverse search, the reverse search signal RREW is input at a high potential, and the input high potential is inverted to a low potential through the inverter IV and applied to the base of the transistor TR14, so that the transistor TR14 is turned on. do.

Since the search control signal SEA is also supplied with a high potential, the transistor TR12 is turned on and the transistor TR13 is turned on, so that the operating power of the power supply terminal Vcc is the resistors R18, TR13, and TR14. Drum automatic frequency control signal DAFC is applied to the connection point of the resistors R1 and R2 through the diode D and the resistor R19, and is therefore applied to the inverting input terminal (-) of the operational amplifier OP. The level of is increased.

Therefore, the level of the drum motor driving signal output from the operational amplifier OP is lowered, thereby lowering the rotational speed of the drum motor and rotating the drum at a slower speed.

As described in detail above, the present invention increases and decreases the speed of the drum by increasing or decreasing the level of the driving signal applied to the drum motor according to the forward search and the reverse search, so that the video head installed on the drum more accurately traces the video track on the video tape. This has the effect of making the search screen clean.

Claims (1)

In the drum speed control circuit in which the drum automatic frequency control signal (DAFC) and the drum automatic phase control signal (DAPC) are compared and outputs a drive signal of the drum motor, a forward search signal fast forward signal (RFF) The forward search control unit 11 for driving the drum motor at high speed by increasing the level of the drum automatic frequency control signal DAFC and the reel rewind signal RREW and the search control signal SEA And a reverse search controller (12) for slowing down the drum motor by reducing the level of the drum automatic frequency control signal (DAFC).