RF, SSP and DSP processing circuits
The composition of the servo circuit: it is composed of RF amplification, servo processing KB9223 (SU3), DSP processing KS9284 (SU2), focusing, tracking, spindle, feed, and motor drive KA9259 (SU4).
For the block diagram of the whole machine, please refer to the drawing on page 85.
1. RF digital signal processing The laser signal reflected from the optical disc is converted into electrical signals PD1, PD2 by the photosensitive device, input to the RF amplifier KB9223 Pin65, Pin66; converted into a voltage signal by the internal current-voltage (IV) amplifier, and sent to RF Adding amplifier addition, EFM demodulation circuit, the demodulated EFM signal is output from Pin33 to DSP processing KS9284 Pin66, after internal error correction and DSP processing, CD-LRCK, CD-DATA is output from Pin11, Pin12, Pin14, CD-BCK signal.
2. Servo processing â‘ Focus servo: As the disc rotates, it is often accompanied by a small range of up and down vibration. In order to track the vibration of the disc, the disc drive is equipped with a focus servo. The laser electrical signals PD1 and PD2 picked up from the laser head are subjected to servo processing KB9223 internal focus error amplifier subtraction, phase compensation and PWM modulation, and then output the focus servo signal FCSO from Pin48 to the servo drive chip KA9259 Pin3, through its internal drive circuit power After magnification, Pin1 and Pin2 output focus servo voltage signals F- and F + to drive the focus coil up and down to move the objective lens up and down to correct the laser focus to accurately fall on the disc information layer.
â‘¡ Tracking servo: Due to the limitation of the manufacturing process level, the center of rotation of the disc and the center of the circular track are shifted. If the disc rotation accuracy is added, the reading of the signal will be seriously affected. In order to control this offset at Within a certain range, the video disc drive is equipped with a tracking servo to correct tracking errors. When the light beam deviates from the trajectory, the photodiode detects the error signals E and F and outputs them to the servo processing KB9223 Pin67 and Pin68, which are converted into voltage signals by the current-voltage (IV) amplifier, tracking error amplifier subtraction, phase compensation and PWM After modulation, the tracking servo signal TKEO is output from Pin50 to KA9259 Pin25, after its internal drive circuit power is amplified, the tracking servo voltage signals T + and T- are output by Pin26 and Pin27, and the tracking coil is driven to move left and right slightly to promote The objective lens is moved slightly from side to side, thereby correcting the laser beam to accurately track the center of the disc information track.
â‘¢ Feed servo: Because the tracking servo has a small adjustment range for the automatic tracking of the disc track, it can only make precise adjustments to the laser head, and cannot make large-scale radial adjustments. Continuous and rapid radial tracking is performed continuously throughout the signal recording range. In fact, the laser player's functions such as jumping, fast forwarding, and fast rewinding require the cooperation of the feed servo mechanism. The feed servo mechanism quickly moves the laser head to the corresponding track, and then uses the tracking servo The mechanism accurately captures the center of the track. Servo processing KB9223 internal feed servo circuit extracts the feed error signal from the tracking signal. After processing, the feed servo signal SLED is output from Pin43 to KA9259 Pin19. After its internal drive circuit power is amplified, it is fed by Pin17 and Pin18. The servo voltage signals SL-, SL + drive the feed motor to complete various feed servos.
â‘£ Spindle servo: The recording density of about 600 signal tracks per 1mm width of the disc, the laser head moves along the track at a constant linear velocity (CLV), and gradually moves from the inner ring to the outer ring, so that the angular velocity changes, and the disc rotates The speed is getting slower and slower, from 500 rpm in the inner ring to 200 rpm in the outer ring. This constant linear velocity rotation method can make the signal recording density of the inner and outer circles of the laser disc be the same, greatly improving the recording density of the optical disc. The purpose of setting the spindle servo system is to control the disc to rotate at a constant linear speed to ensure the correct reading of the signal. The RF signal is obtained by the RF processing circuit KB9223, processed into an EFM signal by internal circuits and peripheral capacitors SC10, SC11, resistors SR15, SR16, and sent from Pin33 to DSP for processing KS9284 Pin66. The EFM signal is sent to the DSP circuit for error correction and data processing all the way inside the DSP processing chip, and is converted into a CD signal and output to the decoding circuit. The other way is to take out the frame synchronization signal and compare it with the internal reference clock to calculate and form the spindle error signal. After PWM modulation, the spindle motor rotation / stop control SMON and spindle motor drive signal SMDP are output from Pin73 and Pin75, and the servo processing KS9223 Pin24, Pin23 is sent After low-pass filtering, the spindle servo signal SPO is output from Pin46 to KA9259 Pin10, and after its internal drive circuit power is amplified, the spindle servo control voltage signals SP + and SP- are output by Pin11 and Pin12 to drive the spindle motor for normal playback at a constant linear speed .
⑤ In and out warehouse control: After receiving the in and out warehouse control signals, the internal microprocessor of ES3207 outputs the out warehouse signal OPEN and the in warehouse warehouse signal CLOSE from Pin18 and Pin20, and drives KA9259 Pin9 and Pin14 to the servo drive through resistors SR8 and SR35. After the power of the driving circuit is amplified, Pin15 and Pin16 output the drive signals MCL and MOP for entering and exiting the warehouse, and driving the motors for entering and exiting the warehouse to control the entry and exit. The CLSW and OPSW signals for entering and exiting the warehouse are input to ES3207 by Pin14 and Pin11 respectively. When the warehouse is in place, the internal micro-processing controls the motor to stop.
â‘¥ Laser power control: It consists of laser diode LD, laser power detection diode PD, transistor SQ1 and KB9223 internal APC (automatic power control) circuit. The laser power detection diode detects the laser intensity signal PD and inputs it to the internal APC circuit of KB9223. When the luminous intensity of the laser diode LD decreases, the APC circuit will increase the LD luminous intensity by controlling the output voltage of Pin70. On the contrary, the LD emission intensity is reduced.
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