KR19980045190A - Tracking error signal detection device with bad waveform detection - Google Patents

Abstract

A tracking error signal detection apparatus having a bad waveform detection function is disclosed. This tracking error signal detection which outputs a tracking error signal using the first and second signals transformed into square waves after dividing the beams received from the disc into a predetermined number and performing the current-voltage conversion and calculation processes. The apparatus inputs first and second signals to detect a phase, outputs a signal that detects a phase difference of the first signal based on the second signal as a first phase difference signal, and a second signal based on the first signal. Phase detection means for outputting a signal in which the phase difference of the signal is detected as a second phase difference signal; Bad waveform detection means for outputting a signal delayed by a predetermined pulse from the first or second phase difference signal as a switch control signal if one of the first and second signals is transformed into a bad waveform; Charging / discharging means for charging or discharging the first and second phase difference signals, respectively, according to the switch control signal; And a low pass filter for filtering the DC component of the signal from the charging / discharging means and outputting the filtered result as a tracking error signal, wherein when signals that should not have a phase difference are input, tracking corresponding to the phase difference is performed. Since no error signal is output, there is an effect that it does not affect other devices connected to the tracking error signal detection device.

Description

Tracking error signal detection device with bad waveform detection

The present invention relates to a digital versatile disk (DVD) 1-beam tracking error signal detection apparatus, and more particularly, to a tracking error signal detection apparatus having a bad waveform detection function.

Hereinafter, the configuration and operation of a conventional tracking error signal detection apparatus will be described with reference to the accompanying drawings.

1 is a schematic circuit diagram of a conventional tracking error signal detection apparatus, including a photodetector 10, first to fourth current-to-voltage converters (I / Vs) 22, 24, 26 and 28, and a first and It consists of second adders 32 and 34, first and second square wave generators 42 and 44, a phase detector 52 and a low pass filter 54.

The photodetector 10 shown in FIG. 1 consists of photodiodes and receives the beam reflected from the disk and divides it into four outputs A, B, C and D. The first to fourth current-voltage converters 22, 24, 26 and 28 convert the four divided output currents into corresponding voltages, respectively. The first adder 32 adds the voltages corresponding to A and C and the second adder 34 adds the voltages corresponding to B and D. The first and second square wave generators 42 and 44 convert the output signals from the first and second adders 32 and 34 into square wave signals, respectively. The phase detector 52 inputs a first signal and a second signal, which are square waves, compares the phase difference between the two signals, and outputs the compared result as the first phase difference signal and the second phase difference signal. Here, the first phase difference signal is a signal that detects the phase difference of the first signal based on the second signal, and the second phase difference signal is a signal that detects the phase difference of the second signal based on the first signal. The low pass filter 54 filters the DC component of the first phase difference signal or the second phase difference signal, and outputs the filtered result as the tracking error signal. Here, the tracking error signal is a voltage signal corresponding to the phase difference between the first signal and the second signal.

The conventional tracking error signal detection apparatus described above outputs a zero tracking error signal when the beam passes through the center of the pit of the disc track so that the first signal and the second signal do not have a phase difference. In addition, when the beam does not pass through the center of the pit of the disc track and the first signal and the second signal have a phase difference, a tracking error signal having a voltage value corresponding to the phase difference is output. The tracking error signal is then connected to the tracking servo IC to adjust the position of the pickup.

However, even if the beam normally passes through the center of the pit, one of the first and second signals may be transformed into a bad waveform.

Hereinafter, the operation of the conventional tracking error signal detecting apparatus when one of the first and second signals is transformed into a defective waveform will be described as follows with reference to the accompanying drawings.

2A to 2G are waveform diagrams of respective terminals of a conventional tracking error signal detection apparatus, and FIGS. 2A and 2B are diagrams illustrating the first and second adders 32 and 34. FIG. And (c) and (d) represent the first and second signals, respectively, which are signals from the first and second square wave generators 42 and 44, and (e) and (f) represent the phases, respectively. Represent each of the signals from the detector 52, and (g) represents the tracking error signal.

As shown in FIG. 2A, when the signal from the first adder 32 is deformed into a bad waveform, the first signal from the first square wave generator 42 also becomes a bad waveform as shown in (c). . Accordingly, a second phase difference signal such as (f) is generated from the phase detector 52 to generate a tracking error signal corresponding to the second phase difference signal. In FIG. 2G, the solid line indicates a tracking error signal that should be normally output when no bad waveform is generated, and the dotted line indicates a tracking error signal increased by a predetermined value due to the bad waveform.

Therefore, the conventional tracking error signal detecting apparatus has a problem of outputting a tracking error signal corresponding to a phase difference when the intermediate signal is deformed into a bad waveform during the tracking error signal detection process even though the beam normally passes through the center of the pit.

An object of the present invention is to provide a tracking error signal detection apparatus having a bad waveform detection function that does not output a tracking error signal even if a bad waveform occurs during the tracking error signal detection process when the beam normally passes through the center of the pit. To provide.

1 is a schematic circuit diagram of a conventional tracking error signal detection apparatus.

2A to 2G are waveform diagrams of respective terminals of a conventional tracking error signal detection apparatus.

3 is a circuit diagram of a tracking error signal detection apparatus of the present invention.

FIG. 4 is a detailed circuit diagram of a phase detector of the tracking error signal detector shown in FIG. 3.

FIG. 5 is a detailed circuit diagram of a bad waveform detection unit of the tracking error signal detection device shown in FIG. 3.

6A to 6H are waveform diagrams of respective terminals of the tracking error signal detecting apparatus of the present invention.

In order to achieve the above object, the tracking error signal is output using the first and second signals transformed into square waves after the beams received from the disk are divided into a predetermined number and the divided beams are subjected to current-voltage conversion and calculation processes. The tracking error signal detecting apparatus according to the present invention comprises detecting first and second signals by inputting the first and second signals, and outputting the detected signal of the phase difference of the first signal as a first phase difference signal based on the second signal, Phase detection means for outputting a signal in which the phase difference of the second signal is detected based on the first signal as a second phase difference signal; Bad waveform detection means for outputting a signal delayed by a predetermined pulse from the first or second phase difference signal as a switch control signal if one of the first and second signals is transformed into a bad waveform; Charging / discharging means for charging or discharging the first and second phase difference signals, respectively, according to the switch control signal; And a low pass filter for filtering the DC component of the signal from the charging / discharging means and outputting the filtered result as the tracking error signal.

Hereinafter, with reference to the accompanying drawings, the configuration and operation of the tracking error signal detection apparatus having a bad waveform detection function according to the present invention will be described.

3 is a circuit diagram of the tracking error signal detection apparatus of the present invention, which includes a photodetector 10, first to fourth current-voltage converters 22, 24, 26 and 28, and first and second adders 32. FIG. And 34), first and second square wave generators 42 and 44, a phase detector 62, a bad waveform detector 64, a charge / discharge unit 66 and a low pass filter 68.

Among the components of the tracking error signal detecting apparatus of the present invention shown in FIG. 3, the same parts as those of the conventional tracking error signal detecting apparatus shown in FIG. 1 are referred to the same reference numerals and description thereof will be omitted.

The phase detector 62 shown in FIG. 3 inputs the first signal and the second signal through the input terminals IN1 and IN2. Here, as described in the prior art, the first and second signals have no phase difference when the beam normally passes through the center of the pit, and has a phase difference when it does not pass normally. The present invention does not output a tracking error signal corresponding to the phase difference when one of the first and second signals is deformed into a bad waveform and has a phase difference even though the beam normally passes through the center of the pit.

The phase detector 62 inputs first and second signals to detect phases, and outputs the detected results as first and second phase difference signals. The first phase difference signal is a signal having a low level in a period where there is no phase difference between the two signals and having a level of the first signal in a phase where the phase of the first signal is different based on the second signal. The second phase difference signal is a signal having a low level in a period where there is no phase difference between the two signals and having a level of the second signal in a phase where the phase of the second signal is different based on the first signal. Accordingly, the first and second phase difference signals are inverted in phases in which the phases of the first and second signals are different from each other, and one of the first and second phase difference signals is a signal having only a low level.

FIG. 4 is a detailed circuit diagram of the phase detector 62 shown in FIG. 3 and includes inverters I1 to I4, inverse AND products NA1 to NA8, and a D flip-flop 602. The circuit shown in Fig. 4 is a general circuit for detecting phase as described above. The inverters I1 and I2 and the inverted ANDs NA1 to NA4 basically perform an inverted AND under the control of the D flip-flop 602, and the inverters I3 and I4 and the inverted ANDs NA5 to NA8) also performs an inverted OR basically under the control of the D flip-flop 602. However, as described above, the low and low levels are output in the same phase of the first and second signals input, and in the different phases. Print different levels.

Referring again to FIG. 3, the bad waveform detector 64 inputs the first and second signals simultaneously with the phase detector 62 and outputs a signal delayed by one pulse from the first or second phase difference signal as a switch control signal. do. The switch control signal from the bad waveform detection unit 64 is not generated if the first and second signals are normal signals, that is, signals having a constant phase difference or no phase difference.

FIG. 5 is a detailed circuit diagram of the bad waveform detection unit 64 shown in FIG. 3 and includes inversion AND products NA9 to NA16 and ORs OR1 to OR3. The circuit shown in FIG. 5 is a general circuit that does not generate an output signal when the first and second signals are normal signals, and generates an output signal when one of the first and second signals is transformed into a bad waveform.

Referring again to FIG. 3, the charge / discharge unit 66 is composed of first and second transistors M1 and M2 and first and second capacitors C1 and C2. The first transistor M1 has a gate connected to the switch control signal, a drain and a source connected between the first phase difference signal and the reference potential GND, respectively, and the second transistor M2 has a gate connected to the switch control signal; And a drain and a source connected between the second phase difference signal and the reference potential GND, respectively. The first and second capacitors C1 and C2 are connected between the first and second phase difference signals of the phase detector 62 and the reference potential GND, respectively.

The charge / discharge unit 66 charges or discharges the first and second phase difference signals, respectively, in response to the switch control signal. When the switch control signal is low level, the first and second transistors M1 and M2 are turned off and the first and second capacitors C1 and C2 charge the first and second phase difference signals, respectively. If the switch control signal is high level, that is, if there is a bad waveform, the first and second transistors M1 and M2 are turned on to bring the output from the phase detector 62 to zero, and the first and second capacitors Fields C1 and C2 discharge the charged signal.

The low pass filter 68 consists of an amplifier OP1, resistors R1, R2, R3 and R4 and capacitors C3 and C4. The negative input terminal of the amplifier OP1 is commonly connected to the first phase difference signal of the phase detector 62 and the first capacitor C1 through the resistor R1, and the positive input terminal is connected through the resistor R2. The second phase difference signal of the phase detector 62 and the second capacitor C2 are commonly connected. In addition, the resistor R3 and the capacitor C3 are connected in parallel between the resistor R1 and the output terminal of the amplifier OP1, and the resistor R4 and the capacitor C4 are connected to the resistor R2 and the reference potential GND. ) Are connected in parallel. The low pass filter 68 passes low frequency components of the signal discharged from the first and second capacitors C1 and C2.

6A to 6H are waveform diagrams showing waveforms of respective terminals of the tracking error signal detecting apparatus of the present invention, wherein (a) and (b) represent a first signal and a second signal, respectively, ( c) and (d) represent the first and second phase difference signals, respectively, (e) represent the switch control signal, and (f) and (g) represent the first and second capacitors C1 and C2 from the Signals are shown, and (h) indicates a tracking error signal.

As shown in FIG. 6A, when the first signal is deformed into a bad waveform, the phase detector 62 has a second phase difference having a pulse of a second signal having no bad waveform as shown in FIG. 6D. The bad waveform detection unit 64 outputs a signal delayed by one pulse from the second phase difference signal as a switch control signal as shown in FIG. In response to the switch control signal, the second capacitor C2 outputs a second phase difference signal, i.e., a signal such as (g) with respect to FIG. 6 (d), which is passed through a low pass filter 68. As shown in 6 (h), the signal is output as a tracking error signal which is almost zero.

As described above, the tracking error signal detection apparatus having a bad waveform detection function according to the present invention does not output a tracking error signal corresponding to the phase difference when signals that should not have a phase difference are input, and thus are connected to the tracking error signal detection device. It has the effect of not affecting other devices.

Claims (1)

A tracking error signal detection apparatus for dividing a beam received from a disc into a predetermined number and outputting a tracking error signal by using the first and second signals transformed into square waves after the divided beams are subjected to current-voltage conversion and calculation processes. To Detects a phase by inputting the first and second signals, outputs a signal from which a phase difference of the first signal is detected based on the second signal, as a first phase difference signal, and based on the first signal Phase detection means for outputting a signal that detects the phase difference of the second signal as a second phase difference signal; Bad waveform detection means for outputting a signal delayed by a predetermined pulse from the first or second phase difference signal as a switch control signal if one of the first and second signals is a signal transformed into a bad waveform; Charging / discharging means for charging or discharging the first and second phase difference signals, respectively, according to the switch control signal; And And a low pass filter for filtering the DC component of the signal from the charging / discharging means and outputting the filtered result as the tracking error signal.