JPH0656660B2 - Drive voltage generation circuit - Google Patents

Description

The present invention relates to a drive voltage generation circuit used for supplying a drive current to a tracking coil, a focus coil, a spindle motor or the like in a disc player or the like.

(B) Conventional Technology For example, an actuator of a CD player is composed of a focus coil of a pickup, a tracking coil, a feed motor for moving the pickup itself, and a spindle motor. Then, as described in, for example, Japanese Patent Laid-Open No. 63-204516, the tracking coil detects the irradiation deviation of the light beam on the track by a photodetector to generate a tracking error signal. It is applied to the tracking coil to track the light beam. When tracking cannot be performed only by applying the tracking error signal to the tracking coil, a signal is supplied to the feed motor of the pickup to move the entire pickup to perform tracking.

Further, as described in Japanese Patent Laid-Open No. 63-193332, a deviation of the spot of the light beam on the disk surface is detected by a photodetector using a half mirror or the like to generate a focus error signal, A focus error signal is applied to the focus coil and the objective lens is moved in the direction perpendicular to the disk surface so that the light beam is always focused on the disk surface.

Further, in a CD player, a servo signal is obtained by using a synchronizing signal or the like extracted from an information signal recorded on the disc, and the servo signal is supplied to a spindle motor so that the disc is always rotated at a constant linear velocity. I have to.

As described above, the control signal is supplied to the actuator such as the tracking coil or the focus coil in the CD player so that the actuator can be operated properly.

A power operational amplifier is used for each actuator as a control signal for each actuator, and a detection signal from a detection means is added to the power operational amplifier to control a voltage applied from a power source to each actuator. Consumes power and is unsuitable as a portable CD player.

Therefore, the detection current is detected according to the deviation of the focus or tracking, the drive voltage is obtained from a plurality of drive circuits according to the detected current, the maximum drive voltage is detected from the drive voltage, and the maximum drive voltage The power supply voltage supplied to each drive circuit is converted into a PWM voltage to reduce the operating voltage supplied to the drive circuit.

(C) Problems to be Solved by the Invention As described above, the operating voltage is reduced by performing PWM voltage conversion on the power supply voltage supplied to each drive circuit at the maximum drive voltage.

By the way, when there is a defect (scratch) on the disc in the CD player, a different defect signal is detected by the focus or tracking error detector. Therefore, when the defect signal is detected, the servo gain and f characteristic of tracking or focus are lowered during that time so that skipping of sound is prevented.

However, when the PWM voltage converted into the drive circuit is used as described above, an LC filter is required, which causes a delay with respect to a rapid change in the control voltage.

Therefore, the present invention eliminates such drawbacks by connecting the defect detection signal to a PWM conversion circuit so that the maximum PWM conversion voltage is generated when a defect occurs, and immediately after the defect passes, each tracking or focus servo is in a normal state. The present invention provides a drive voltage generating circuit that is operated in accordance with.

(D) Means for Solving the Problems The drive voltage generating circuit of the present invention includes a plurality of drive circuits for supplying a drive voltage to the drive means according to the detection current detected by the detection means, and the drive circuits A maximum voltage detection circuit for detecting the maximum output voltage, a PWM voltage conversion circuit for performing PWM voltage conversion of the power supply voltage supplied to all the drive circuits by a signal based on the detected maximum voltage, and the converted voltage. A filter for smoothing the PWM conversion voltage to obtain an operating voltage, a defect signal detector for generating a defect signal when the detection unit detects a defect, and a defect signal from the defect signal detection circuit for turning on the maximum signal. It is composed of a transistor that generates a larger control voltage detected by the voltage detection circuit and supplies it to the PWM voltage conversion circuit.

(E) Operation The drive voltage generation circuit of the present invention has the above-mentioned configuration,
When a defect is detected by the defect signal detector circuit, the maximum operating voltage is supplied to the drive circuit, and even if the servo gain is reduced when the defect is detected, the servo is quickly Return the gain to normal gain.

(F) Embodiment An embodiment of the drive voltage generation circuit of the present invention will be described with reference to the drawings.

In the figure, (1a) to (1d) are drive circuits that supply a drive current to a focus coil, a tracking coil, a pickup feed motor, and a spindle motor.
(1a) to (1d) have exactly the same circuit configuration, for example, a drive circuit
(1a) is an input terminal (2) to which a reference voltage (Vref) is applied, an input terminal (3) to which a focus shift signal (V _C1 ) according to the focus shift is added, and the reference voltage and the focus shift signal. An absolute value amplifier (4) that amplifies the absolute value of the difference and extracts the focus control signal (V _M1 ), a comparator (5) that compares the reference voltage and the magnitude of the focus deviation signal and generates an operation direction instruction signal, A logic circuit (6) for processing the focus control signal (V _M1 ) and the movement direction finger signal, the logic circuit (6)
Operational amplifiers (7) and (8) for amplifying the focus control signal (V _M1 ) by operating one of the shifts with the signal from
(7) (8) and transistors (9) to (12) selectively turned on by signals from the logic circuit (6), and the objective lens connected to the connection point of each of the transistors (9) to (12) A focus coil (13) for moving (not shown) in the direction perpendicular to the disk surface is provided. (15) is each of the drive circuits (1a) ~ (1d)
The maximum control signal generation circuit for detecting the maximum control signal among the control signals obtained from the output terminals (14a) to (14d) of the control circuit (1a) to (1d) at the input terminals (16a) to (16d). ) Output terminal
A differential amplifier (1a to which the control signals from (14a) to (14d) are added.
7) to (20), diodes (21) to (24) connected to the output terminals of these differential amplifiers (17) to (20), and these diodes (2)
It consists of a time constant circuit (25) connected to the outputs of 1) to (24). (26) is a PWM (Pulse Width Modulation) voltage conversion circuit, a transistor whose emitter and collector are connected to the power supply (27).
(28), a smoothing diode (29) connected to the collector of the transistor (28), a coil (30) and a capacitor (31),
A comparator (32) for comparing the maximum control signal from the maximum control signal detection circuit (15) with the operating voltage (V _PWM ) obtained by switching the power supply voltage from the power supply (27) with the transistor (28). And a PWM voltage generator (33) for comparing the voltage from the comparator (32) with the sawtooth wave signal from the sawtooth wave generator (34) to obtain a PWM voltage. The PWM voltage from the PWM voltage generator (33) is applied to the base of the transistor (28), and the operating voltage (V _PWM ) applied to the comparator (32) is the transistor.
The loss voltage (V _LOSS ) of (9) to (12) is increased. (35) is C
D A defect signal detector that detects a defect signal different from the normal focus error signal or tracking error signal that occurs in the photodetector when there is a scratch on the disc surface. The detected defect signal is supplied to the power source via a resistor. (27) and one end of the comparator (32) is added to the base of a transistor (36) connected to the comparator (32) of the maximum control signal detection circuit (15) differential amplifier (17) ~ Apply a control signal that is greater than that available at the output terminal of (20).

Next, the operation of the drive voltage generating circuit of the present invention will be described by taking a CD player as an example.

When the focus of the light beam from the optical pickup is deviated due to bending or the like during the performance of the CD disc, the deviation appears as a change in the light amount of the light beam applied to each photodetector through the half mirror. The focus shift signal corresponding to the focus shift is detected by taking the difference between the signals generated from the respective photodetectors. The detected defocus signal (V _C1 ) is applied to the input terminal (3),
The reference voltage (Vref) supplied to (2) is applied to the absolute value amplifier (4), and the reference voltage (Vref) and the focus shift signal (V
_C1 ) is taken and the absolute value of the difference is amplified to generate the focus control signal (V _M1 ). On the other hand, the comparator (5) compares the magnitude of the focus shift signal (V _C1 ) with the reference voltage (V ref) to generate a positive or negative operation direction indicating signal, which is supplied to the logic circuit (6). When the operation direction indicating signal applied to the logic circuit (6) is positive, a signal is applied from the logic circuit (6) to the operational amplifier (7) and the transistor (12) to turn on the transistor (12). On the other hand, the operational amplifier (7) is added with the focus control signal (V _M1 ) and the operation direction instruction signal in a superimposed manner, and the amplified signal is applied to the transistor (9).
In addition, since it turns on according to the magnitude of the voltage applied to the transistor (9), the operating voltage (V _PWM ) flows through the transistor (9), the focus coil (13) and the transistor (12), The objective lens is moved away from the CD disk surface according to the magnitude of the focus control signal (V _M1 ).

On the contrary, when the operation direction indicating signal generated from the comparator (5) is negative, signals are added from the logic circuit (6) to the transistor (10) and the operational amplifier (8), and the tracking (11)
Since (10) is turned on, the operating voltage (V _PWM ) is
It flows through 1) to the focus coil (13) in the opposite direction to the above. Therefore, the objective lens is moved toward the CD disk surface.

Although the focus servo has been described above, the tracking servo is almost the same, and the deviation of the light beam from the track on the CD disk surface is detected by a photodetector and applied to the input terminal of the drive circuit (1b) to obtain a reference voltage. A tracking control signal (V _M2 ) is obtained by taking the difference as an absolute value, and the tracking control signal is added to the tracking coil wound around the lens frame of the objective lens together with the focus coil, and the objective lens is placed on the CD disk surface. On the other hand, it is moved horizontally to perform tracking.

When tracking control cannot be performed only by moving the objective lens, this is detected, an input signal is added to the drive circuit (1c), a control signal (V _M3 ) is taken out, and the control signal (V _M3 )
Is added to a pickup feeding motor, and the motor is rotated to move the entire pickup in the tracking direction to perform tracking.

Further, in order to always rotate the CD disc at a constant linear velocity, a synchronizing signal or the like extracted from the information signal is added to the drive circuit (1d) to obtain a control signal (V _M4 ) and the control signal (V _M4 )
_The spindle motor is controlled by _M4 ) so that the CD disk can be rotated at a constant linear velocity.

Since the control voltage to each actuator of the CD player such as the focus coil is sufficiently small compared with the power supply voltage from the power supply (27), the power supply voltage is directly used for each drive circuit.
When added to (1a) to (1d), it becomes a loss and power consumption becomes large.
Therefore, the maximum control signal among the control signals is detected, and the voltage obtained by comparing with the operating voltage (V _PWM ) applied to each of the drive circuits (1a) to (1d) is compared with the sawtooth wave signal and PWM A voltage is generated, and the power supply voltage is switched by the detected PWM voltage so that the operating voltage (V _PWM ) becomes the voltage of the maximum control signal.

That said control signal (V _M1) ~ from the driving circuit (1a) ~ (1d)
(V _M4 ) is each differential amplifier (17) of the maximum control signal detection circuit (15)
After being added to the input terminals (16a) to (16d) of-(20) and amplified, they are added to the time constant circuit (25) through the diodes (21) to (24). The control signals from the drive circuits (1a) to (1d) change from 0.6V to 1.2V depending on the control state of the actuator.
For example, when the objective lens is largely displaced from the disk surface from the drive circuit (1a), a large focus control signal is generated to return the objective lens to the original position. In this way, the control signals (V _M1 ) to (V _M4 ) generated by the drive circuits (1a) to (1d) are changing every moment. The control signals (V _M1 ) to (V _M4 ) are amplified, and the diodes (21) to which the cathodes are commonly connected are
Since it is applied to the time constant circuit (25) via (24), only the maximum control signal of the control signals is added to the time constant circuit (25) and smoothed. The smoothed signal and operating voltage (V
_PWM ) is compared with the comparator (32), and the PWM voltage generator (33)
In, PWM conversion is performed by the sawtooth wave oscillation signal from the sawtooth wave oscillator (34) to obtain PWM. The obtained PWM voltage is applied to the base of the transistor (28),
Since (28) is turned on and off intermittently, the power supply voltage from the power supply (27) flows intermittently. The intermittent power supply voltage is smoothed by the diode (29), the coil (30), and the capacitor (31), and applied as an operating voltage (V _PWM ) to the drive circuits (1a) to (1d).

By the way, when there is a defect on the CD disc surface,
Unlike the usual focus error signal or tracking error signal, a large tracking control signal or the like is generated in the photodetector, and a so-called sound skip that causes several tracks to jump is generated. Therefore, during this period, the tracking and focus servo gains are forcibly reduced. However, it is necessary to restore the functions of the focus servo and the tracking servo immediately after passing through the defect portion of the CD disk surface. However, in order to obtain the operating voltage, an LC filter including coils (30) and (31) is used. In addition, since the servo gain is lowered and the maximum output voltage generated by the drive circuit is small, there is a delay with respect to an abrupt change in the control voltage. Therefore, in the present invention, when the defect signal is detected by the defect signal detector (35), the transistor (36) is turned on to generate a control signal larger than the maximum control signal obtained from the maximum control signal detection circuit (15), It is applied to the time constant circuit (25). The control signal supplied to the time constant circuit (25) is a comparator.
It is added to (32) and compared with the operating voltage (V _PWM5 ), and PWM conversion is performed by the sawtooth wave signal from the sawtooth wave oscillator (34) in the PWM voltage generator (33) to obtain PWM. The obtained PW
The M voltage is applied to the base of the transistor (28) to intermittently turn on / off the transistor (28).
Since the maximum control signal is supplied to (32), the PWM voltage is also large, the ON time of the transistor (28) is long, and the operating voltage passing through the transistor (28) is maximum. Therefore, the operating voltage (V _PWM ) that is smoothed by the coil (30) and the capacitor (31) and applied to each drive circuit (1a) to (1d) becomes the maximum, so immediately after the lapse of the defect, the tracking servo or the The focus servo etc. can be returned to the normal servo state and operated.

(G) Effect of the Invention As described above, the drive voltage generation circuit of the present invention detects the maximum output voltage among the output voltages generated from each drive circuit, and compares the maximum output voltage with the operating voltage to obtain the voltage. PWM
The power consumption is reduced by converting the voltage, interrupting the power supply voltage with the PWM conversion voltage, and supplying an operating voltage of a required magnitude to each of the drive circuits. In order to obtain a smoothed operating voltage from the intermittent power source voltage, a smoothing L
Although a C filter is used, if the servo gain is reduced to prevent skipping when a defect is detected, the output voltage generated from the drive circuit after passing the defect is reduced, and the normal servo state is restored. However, since the operating voltage is maximized when a defect is detected in the present invention, the servo time delay can be prevented.

[Brief description of drawings]

The figure shows a drive voltage generating circuit of the present invention. (1a) ~ (1d) ... drive circuit, (15) ... maximum control signal detection circuit, (26) ... PWM voltage conversion circuit, (35) ... defect signal detection circuit.

Claims (1)

[Claims] 1. A plurality of drive circuits for supplying a drive voltage to a drive means according to a detection current detected by the detection means,
A maximum drive voltage detection circuit that detects a maximum output voltage generated by the drive circuit, and a power supply voltage that is supplied to each drive circuit by a signal based on the detected maximum output voltage is PW.
A PWM voltage conversion circuit for performing M voltage conversion, a filter for smoothing the converted PWM conversion voltage to obtain an operating voltage, and a defect signal detector for generating a defect signal when a defect is detected by the detection means,
A drive voltage generation circuit comprising a transistor which is turned on by a defect signal from the defect signal detector and generates a larger control voltage detected by the maximum voltage detection circuit and supplies the control voltage to the PWM voltage conversion circuit.