CN1295685C - The control circuit of the automatic gain control device of the optical disc player - Google Patents

Abstract

A control circuit of automatic gain control device of optical disk drive is prepared as using a variable gain module and a feedback circuit to feedback control gain value of said variable gain module. The control circuit includes a fixed gain setting device for providing a fixed gain and a switch module, which can synchronously control the fixed gain setting device and the variable gain module, and whether the variable gain module is connected with the feedback circuit, when the CD-ROM drive reads the blank area of the CD or generates track jump action, the fixed gain setting device is connected with the variable gain module, and the feedback circuit is not connected with the variable gain module, otherwise, the fixed gain setting device is not connected with the variable gain module, and the feedback circuit is connected with the variable gain module, thereby achieving the purpose of preventing the variable gain module from generating false operation.

Description

The control circuit of the automatic gain control device of the optical disc player

technical field

The invention relates to a control circuit of an automatic gain control device of a CD player, in particular to a control circuit of the automatic gain control device of a CD player which can prevent the automatic gain control device from malfunctioning.

technical background

As shown in Figure 1, the radio frequency signal generated by the optical disc drive or optical reading device by reading the information on the disc through the optical pick-up head (Pick-upHead) 1 is usually sent to a radio frequency amplifier 2 for proper amplification and output , to provide a back-end Data Phase-Locked Loop (DataPLL: Data Phase-Locked Loop) 3 for information timing capture. The RF amplifier 2 mainly includes an automatic gain control device 21 and an equalizer 22 . The automatic gain control device 21 mainly prevents the amplitude of the output signal from changing abnormally due to the amplitude change of the input signal, that is, keeps the amplitude of the output signal constant, and then provides it to the equalizer 22 for amplitude and phase equalization processing.

As shown in FIG. 2 , the automatic gain control device 21 includes a variable gain module 23 and a feedback circuit 24 . After the radio frequency signal sent by the optical pickup 1 is amplified by the variable gain module 23, the amplitude of the output signal generated is measured by the feedback circuit 24, and compared with a reference amplitude (not shown), a control signal is output Instruct the variable gain module 23 to adjust the gain appropriately so that the amplitude of the output signal remains constant.

However, when the optical pick-up head 1 reads on a recordable disc with a blank area (Blank Area) and a data area (DataArea) at the same time, the blank area will not be read by the optical pick-up head 1. Generate any radio frequency signal, so that the variable gain module 23 produces a very large gain value for signal amplification, so that when the optical pickup 1 enters the data area from the blank area, the radio frequency will be activated when the feedback circuit 23 has no time to respond. The signal is over-amplified by the variable gain module 23 or even reaches a saturated state, and the amplitude of the output signal of the variable gain module 23 can be restored to the set value only after a period of transient response of the variable gain module 23 .

In addition, when the optical pick-up head 1 of the optical disc drive needs to perform a jump action due to tracking or other factors, the optical pick-up head 1 cannot sense the radio frequency signal on the disc during the track jump process. The variable gain module 23 is caused to have the same situation as above.

For this reason, U.S. Patent No. 5,128,911 discloses an optical disk drive, which uses an envelope detector (envelope detector) to detect the output signal of the automatic gain control circuit (AGC), and outputs the signal and a reference level through a After the comparator is compared, a gate signal (gate signal) is generated to indicate whether the optical pick-up head is located in the blank area of the disc, and the gate signal and a jump signal (jump signal) are used to control an OR gate, Make a timely output of a gain hold signal (gain hold signal) to control the automatic gain control circuit (hereinafter referred to as AGC) to generate a fixed gain. Alternatively, a switch circuit is controlled by a track jump signal, and the switch circuit can be set between the optical pickup head and the current/voltage converter, between the current/voltage converter and the amplifier, between the AGC and the input signal detection circuit, or between the wave between the seal detector and the comparator, so that when the optical pickup head trips, the gate signal is output to a high level and the AGC is controlled at a fixed gain.

Although the above-mentioned prior art properly controls the output gain of the AGC according to the track jump signal and the gate signal, it needs to use an additional input signal detection circuit to generate the gate signal, and additionally match the OR (OR) gate, or additionally use a jumper The rail signal controls the switch circuit to indirectly control the gate signal to control the output gain of the AGC, which not only increases the manufacturing cost but also occupies the circuit layout area.

Contents of the invention

The main purpose of the present invention is to provide a control circuit of an automatic gain control device of an optical disc player which can prevent the automatic gain control device from malfunctioning.

Another object of the present invention is to provide a control circuit for an automatic gain control device of an optical disc player that can reduce costs and save circuit layout area.

A control circuit for an automatic gain control device of an optical disc drive, the optical disc drive includes a detection unit for detecting a blank area of an optical disc machine or performing a track jump operation; the automatic gain control device includes a variable gain module and a A feedback circuit, which feeds back and controls the gain value of the variable gain module according to the output signal of the variable gain module; wherein:

The control circuit includes:

a fixed gain setter for providing a fixed gain; and

A switch module, used to synchronously control the fixed gain setter and the variable gain module, and whether the variable gain module is connected to the feedback circuit, when the optical disc drive reads a blank area of the disc or generates a track jump When in action, the switch module will connect the fixed gain setter to the variable gain module, and simultaneously disconnect the feedback circuit from the variable gain module, so that the variable gain module outputs a fixed gain value; otherwise, the The switch module means that the fixed gain setter is not connected to the variable gain module, and at the same time, the feedback circuit is connected to the variable gain module, so that the feedback controls the variable gain module.

The switch module includes a first switch, a second switch and a driving circuit for synchronously driving the first switch and the second switch, the first switch is arranged between the fixed gain setter and the variable gain module During the interval, the second switch is set between the variable gain module and the feedback circuit. When the optical disc player reads a blank area of the disc or generates a track jump action, the drive circuit will close the first switch and make the The second switch is turned on, otherwise, the first switch is turned on, and the second switch is turned off.

From the above, the control circuit of the automatic gain control device of the optical disc player of the present invention can prevent the automatic gain control device of the optical disc player from malfunctioning, and the present invention can reduce the cost and save the circuit layout area.

Description of drawings

FIG. 1 is a block diagram of the main circuit of an optical disc drive.

FIG. 2 is a circuit block diagram of a conventional automatic gain control device.

FIG. 3 is a circuit block diagram of an embodiment of the control circuit of the automatic gain control device of the optical disc player of the present invention.

FIG. 4 is a schematic diagram of the driving circuit in the embodiment of FIG. 3 .

Detailed ways

The control circuit of the automatic gain control device of the optical disc player of the present invention, the automatic gain control device includes a variable gain module and a feedback circuit, and the feedback circuit controls the gain of the variable gain module according to the output signal of the variable gain module value. The control circuit includes a fixed gain setter and a switch module. The fixed gain setter is used for providing a fixed gain. The switch module is used to synchronously control whether the fixed gain setter and the variable gain module are connected or not, and whether the variable gain module is connected to the feedback circuit. When in action, the switch module will connect the fixed gain setter to the variable gain module, and simultaneously disconnect the feedback circuit from the variable gain module, so that the variable gain module outputs a fixed gain value; otherwise, the The switch module means that the fixed gain setter is not connected to the variable gain module, and at the same time, the feedback circuit is connected to the variable gain module, so that the feedback controls the variable gain module. In this way, the effect of preventing the automatic gain control device from malfunctioning is achieved.

The foregoing and other technical contents, features and effects of the present invention will be clearly understood in the following detailed description of an embodiment with accompanying drawings.

Referring to Fig. 3, it is an embodiment of the control circuit of the automatic gain control device of the optical disc player of the present invention, wherein the input end of the automatic gain control device 4 of the optical disc player 1 is connected to the optical pick-up head 10, and the output end is connected to the equalizer 3 . And the automatic gain control device 4 includes a variable gain module 41 and a feedback circuit 42 for feedback controlling the gain value of the variable gain module according to the output signal of the variable gain module 41 .

The feedback circuit 42 includes a peak/valley detector 43 , a reference amplitude setter 44 and a comparator 45 . The two input ends of the comparator 45 are respectively connected to the peak/valley detector 43 and the reference amplitude setter 44 , and the output end 451 of the comparator 45 is connected to the variable gain module 41 .

In addition, in the optical disc drive 1, when the data format on the disc read by the optical head 10 belongs to a part of the data area and a part of the blank area (such as the data format of the CDR/CDRW packet writing method (Packet writing)) , a preset circuit in the optical disc drive 1 - a blank area detection module (not shown) will detect the blank area and generate a discrimination signal RECD1 to indicate that the optical pickup head 10 is located in the data area of the disc or blank space. In addition, when the optical pick-up head 10 is performing a track jump (Jump/Seek) action, a track-lock detection device (not shown) in the optical disc drive will perform track-lock detection and output a detection signal TRON, and When the detection signal TRON="L", it means that the optical pickup 10 is in an off-track state, and at this time the optical pickup 10 cannot sense the radio frequency signal on the disc, and there is no radio frequency signal output.

Therefore, the control circuit 5 of this embodiment includes a fixed gain setter 51 and a switch module 52 . The fixed gain setter 51 is used for providing a fixed gain. The switch module 52 includes a first switch 53 , a second switch 54 and a driving circuit 55 for synchronously driving the first switch 53 and the second switch 54 .

The first switch 53 is arranged between the fixed gain setter 51 and the variable gain module 41 , and the second switch 54 is arranged between the variable gain module 41 and the output terminal 451 of the comparator 45 . And the driving circuit 55 is controlled by the discrimination signal RECD1 and the detection signal TRON.

When the optical pickup head 10 reads data normally (that is, when the optical pickup head 10 is located in the data area of the disc), the first switch 53 is in the open (OFF) state, and the second switch 54 is in the closed (ON) state After the radio frequency signal generated by the optical pickup 10 reading the disc is amplified by the variable gain module 41, it is sent to the peak/valley detector 42 to measure the amplitude, and then sent to the comparator 45 to be compared with the reference amplitude setting Compared with a reference value generated by the stabilizer 44, a control signal is output to adjust the gain value of the variable gain module 41 in time to keep the amplitude of the output signal consistent.

However, when the blank area detection module of the optical disc player 1 detects that the optical pick-up head 10 enters the blank area from the data area of the disc, in order to prevent the variable gain module 41 from generating excessive noise due to the absence of radio frequency signals in the blank area The gain value is used for signal amplification, and the discrimination signal RECD1 will control the driving circuit 55 to close (ON) the first switch 53, and at the same time open (OFF) the second switch 54, so that the variable gain module 41 provides The fixed gain is used for signal amplification (that is, the variable gain module 41 is set to a fixed gain output), so that once the optical pick-up head 10 enters the data area from the blank area, the variable gain module 41 will not generate the data area of the disc. The radio frequency signal is over-amplified, and since the optical pickup 10 is already in the data area of the disc, the discrimination signal RECD1 will make the driving circuit 55 open (OFF) the first switch 53 and close the second switch 54 ( ON), so that the output gain of the variable gain module 41 continues to accept the feedback control of the feedback circuit 42 . In this way, it is possible to prevent the variable gain module 41 from producing abnormal output signals or abnormal amplitude changes when the optical pickup head 10 enters the blank area from the data area, or enters the data area from the blank area, thereby improving the quality of the radio frequency signal and read performance of the CD-ROM.

Wherein, the driving circuit 55 can be a flip-flop, such as a D-type flip-flop, as shown in FIG. The input terminal D is connected, and its output terminals Q and Q' will output two anti-phase signals, which can be used to control the first switch and the second switch respectively, so that when the first switch is closed (ON), the second switch is opened (OFF ); when the second switch is turned on (OFF), the first switch is turned off (ON).

Similarly, when the optical pick-up head 10 changes from the track-locking action to the track-jumping action, the track-locking detection device will make the detection signal TRON="L" (low level), and control the driving circuit 55 to turn the first switch 53 is closed (ON), and the second switch 54 is opened (OFF), so that the variable gain module 41 outputs a fixed gain until the optical pick-up head 10 returns to the locked track state by the track jumping action, and the detection signal TRON="H" ( high level), the drive circuit 55 is controlled to turn on (OFF) the first switch 53 and turn off (ON) the second switch 54, so that the variable gain module 41 accepts the feedback control of the feedback circuit 42.

As can be seen from the above description, since the blank area detection module of the optical disc drive 1 will generate the discrimination signal RECD1 indicating that the optical pick-up head 10 is located in the blank area or the data area of the disc, and the track detection device of the optical disc drive 1 is also detecting The detection signal TRON will be generated when the optical pickup 10 is in the track-locked state. Accordingly, the present invention uses the discrimination signal RECD1 and the detection signal TRON to control the switch module 52, so that when the optical pickup 10 is located in the blank area of the disc, , or when the optical pickup head 10 performs a track jumping action, the feedback control loop of the variable gain module 41 is interrupted, and a fixed gain is additionally provided to the variable gain module 41, thereby preventing the variable gain module 41 from outputting an excessively amplified signal Or abnormal amplitude changes, thereby improving the quality of the radio frequency signal and the read performance of the optical disc drive. In addition, compared with the above-mentioned conventional technology, the present invention can also effectively reduce the manufacturing cost and circuit layout space.

Claims (2)

1. The control circuit of the automatic gain control device of a kind of optical disc drive, described optical disc drive comprises a detection unit, is used for detecting the blank area of optical disc machine read or carry out track skip operation; Described automatic gain control device comprises a variable gain module And a feedback circuit, the feedback circuit controls the gain value of the variable gain module according to the output signal feedback of the variable gain module; it is characterized in that: The control circuit includes: a fixed gain setter for providing a fixed gain; and A switch module, used to synchronously control the fixed gain setter and the variable gain module, and whether the variable gain module is connected to the feedback circuit, when the optical disc drive reads a blank area of the disc or generates a track jump When in action, the switch module will connect the fixed gain setter to the variable gain module, and simultaneously disconnect the feedback circuit from the variable gain module, so that the variable gain module outputs a fixed gain value; otherwise, the The switch module means that the fixed gain setter is not connected to the variable gain module, and at the same time, the feedback circuit is connected to the variable gain module, so that the feedback controls the variable gain module. 2. The control circuit of the automatic gain control device of the optical disc player according to claim 1, wherein the switch module includes a first switch, a second switch, and a driver for synchronously driving the first switch and the second switch Circuit, the first switch is set between the fixed gain setter and the variable gain module, the second switch is set between the variable gain module and the feedback circuit, when the optical disc drive reads the When a blank area or a track jump action occurs, the driving circuit will turn off the first switch and turn on the second switch; otherwise, turn on the first switch and turn off the second switch.

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