JP2000244313A - Pll circuit for optical disk reproducing device and method for continuously increasing its open loop gain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PLL circuit for an optical disk reproducing device that utilizes a continuous increase in level at an output terminal of a charge pump circuit in a CAV reproduction circuit so as to continuously increase the band of an open loop gain. SOLUTION: Receiving data from an optical disk and an internal clock from a frequency divider 17, a phase comparator 10 outputs its phase difference information as an UP signal and a DOWN signal. A charge pump circuit 11 outputs/draws a current Ic to/from a terminal 31. Similarly a charge pump circuit 12 outputs/draws the current Ic to/from a terminal 32. A voltage current converter 13 converts a voltage at the terminal 31 into a current and supplies it to the charge pump circuit 11. Similarly a voltage/current converter 14 converts a voltage at the terminal 31 into a current and supplies it to the charge pump circuit 12. An oscillated frequency of a voltage controlled oscillator 16 is changed by the voltage at the terminal 32 and the oscillated frequency output thereof is frequency-divided by a frequency divider 17 and its output is given to the phase comparator 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus for reproducing an optical disk at a high speed, and more particularly, to an optical disk reproducing apparatus in which when an input reproduction data rate continuously increases, an open loop gain band also continuously increases. PLL for equipment
The present invention relates to a circuit and a method for continuously increasing its open loop gain.

[0002]

2. Description of the Related Art For an optical disk reproducing apparatus having a PLL circuit, an optical disk apparatus capable of reading a large amount of data in a short time by increasing the speed of a CPU or the like is required. In particular, the reading speed of a CD-ROM drive mounted on a personal computer or the like has been rapidly increased to double speed, quadruple speed, and octuple speed. At this stage, the data is generally read by the CLV playback method. However, as the speed increases, the speed difference between the inner circumference and the outer circumference of the optical disk increases, and the load on the motor that controls the rotation of the optical disk increases. Was. Also,
In the CLV reproduction method, the rotation speed of the motor for rotating the optical disk is maintained at a constant linear speed, so that the innermost circumference of the optical disk rotates at the maximum speed when reading. Therefore, the speed of the rotating motor must be adjusted each time the CD-ROM is played back and taken in, in which the rotation speed becomes slower toward the outer periphery and random access frequently occurs. Therefore, by adopting a CAV reproducing method with a constant angular velocity that does not require control of a motor, data can be read while maintaining the rotation of the optical disk at a constant speed.

In such a CAV reproduction method, when the transfer rate of input data increases, an internal clock corresponding to the rate must be generated. On the other hand, conventionally, it has been responded by switching the open loop gain of the PLL stepwise. For example, JP-A-10-23
In No. 3682, when the input data rate increases, the current in the charge pump circuit is controlled by a switch to switch the open loop gain. FIG. 6 shows the circuit configuration. FIG. 7 shows the charge pump circuit 2
0, and the current Ic is detected by the switches 80 and 81.
Can be changed in size. Similarly, the charge pump circuit 21 can change the magnitude of the current Ir by the switch. This controls the open loop gain.

[0004]

In the PLL circuit for an optical disk reproducing device having such a configuration, since the open loop gain is switched discontinuously, it takes time until the phase synchronization is stabilized again. Data transfer will be stopped. Further, when the input data rate fluctuates in the vicinity where the switching of the open loop gain is required, the stop state frequently occurs, and the data transfer capability is reduced.

In view of the above problems, the present invention is directed to an optical disk reproducing apparatus for continuously increasing the open loop gain band by utilizing the fact that the potential of the output terminal of a charge pump circuit continuously rises in CAV reproduction. An object of the present invention is to provide a PLL circuit and a method for continuously increasing the open loop gain thereof.

[0006]

According to a first aspect of the present invention, there is provided a PLL circuit for an optical disk reproducing apparatus for reproducing an optical disk at a high speed, wherein data read from the optical disk and input data are stored in the PLL circuit. And a phase comparator to which a synchronized internal clock is input, a charge pump circuit that outputs a current proportional to the phase difference information output from the phase comparator, a voltage-current converter that converts a voltage to a current, and a voltage It is characterized by comprising a voltage-controlled oscillator that synchronizes an oscillation frequency with input data by a voltage generated by a current converter, a charge pump circuit, and a capacitor. According to the PLL circuit for an optical disk reproducing device of the first invention of the present application having the above configuration,
An internal clock synchronized with the read data of the optical disk output from the phase comparator can be continuously generated. A circuit composed of a charge pump circuit and a voltage-current converter can control a signal based on the phase difference by controlling the current in proportion to the input data rate. Therefore, the bandwidth of the open loop gain accompanying the increase of the input data is continuously increased. be able to.
In addition, since the operation can be performed continuously, it is not necessary to switch the band during the CAV reproduction operation of the optical disc, and the data transfer is not stopped at the time of the band change, thereby increasing the data transfer rate.

Further, a PLL circuit for an optical disk reproducing apparatus according to the second invention of the present application is a PLL circuit for an optical disk reproducing apparatus according to the first invention of the present application, wherein the charge pump circuit includes a signal output from a phase comparator. Is a current proportional to the signal width. According to the PLL circuit for an optical disc reproducing apparatus of the second invention of the present application having the above configuration, a pulse signal indicating a phase frequency difference is sent from the phase comparator to the charge pump circuit. Since this signal outputs a continuous change in potential in the form of a pulse, the charge pump circuit can output a current proportional to the pulse width when the input data transfer rises, and when it falls The charge pump circuit can draw a current proportional to the pulse width. In this manner, the current corresponding to each signal width can be continuously varied, so that the band of the open loop gain can be continuously increased.

Further, a PLL circuit for an optical disk reproducing device according to a third invention of the present application is a PLL circuit for an optical disk reproducing device according to the first invention of the present application and the second invention of the present application, wherein the voltage-current converter comprises: It is a conductance and is characterized by converting a voltage into a current. The third application of the present application having the above configuration
According to the PLL circuit for an optical disk reproducing apparatus of the invention, the potential is continuously increased and decreased by the continuously changing current output from the charge pump circuit. Such a potential is converted into a current by a voltage-current converter (conductance) and fed back to the charge pump circuit, whereby a continuously variable gain characteristic can be secured. Also,
Since the band of the continuous open loop gain can be changed, time loss in switching control of the open loop gain can be prevented, and high-speed CAV reproduction can be performed.

Further, the PLL circuit for an optical disk reproducing apparatus according to the fourth invention of the present application is a PLL circuit for an optical disk reproducing apparatus according to the first invention of the present application, the second invention of the present application, or the third invention of the present application.
An L circuit, wherein the voltage-controlled oscillator changes an oscillation frequency according to an input voltage.
According to the PLL circuit for an optical disk reproducing device of the fourth invention of the present application having the above-described configuration, a filter circuit is provided at a stage preceding the voltage-controlled oscillator, and filters a current generated by the charge pump circuit. After being generated as a control voltage, it is sent to a voltage-controlled oscillator. Since this control voltage outputs a continuous change in potential,
An oscillation frequency corresponding to the input data rate can be generated by the voltage-controlled oscillator. The generated pulse signal is frequency-divided in the next stage and output to the phase comparator as a clock synchronized with the input data. Therefore, even if the data rate of the optical disk continuously read reaches the high-speed area, an internal clock synchronized with the data rate can be continuously generated.

A fifth aspect of the present invention provides a PLL circuit for an optical disc reproducing apparatus according to the first or second aspect of the present invention, wherein the charge pump circuit comprises: It is characterized by being constituted by a plurality of current mirror circuits. According to the PLL circuit for an optical disk reproducing device of the fifth invention of the present application having the above configuration, the charge pump circuit generates the sum of the current output from the voltage-current converter and the constant current transmitted by the current mirror circuit. Is done. The generated current is a current proportional to the current value output by the voltage-current converter, is transmitted by the next current mirror circuit, and is controlled by a signal based on phase difference information output from the phase comparison circuit. Can be done. According to this current control, when a continuously increasing current is input, a current proportional to the current can be continuously increased, and accordingly, the band of the open loop gain according to the transfer data rate can be increased. Further, by turning off the output current from the voltage-current converter, only the constant current is provided, so that it is possible to cope with CLV reproduction.

[0011] In a sixth aspect of the present invention, in the method for continuously increasing the open-loop gain for high-speed CAV reproduction of an optical disk, the gain characteristic is continuously changed in accordance with an increase in the transfer rate of input data. Features. The method for continuously increasing the open loop gain according to the sixth invention of the present application is characterized in that, when the transfer rate of input data is continuously increased from the CAV reproduction of the optical disk, signal information is sent from the phase comparator to the charge pump circuit. Is done. The charge pump circuit generates a potential from signal information, and the potential is continuously fed back to the charge pump circuit by a voltage-current converter as a current proportional to the rise of the voltage, whereby the gain characteristic can be continuously changed. it can. This allows
High speed CAV (Constant Angular Velocit)
(y: constant angular velocity) In reproduction, even if the input data rate changes to a high-speed region, continuous reproduction can be performed without switching gain characteristics, and high-speed and continuous data reading can be performed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a PLL circuit for an optical disk reproducing apparatus according to an embodiment of the present invention. In the PLL circuit for an optical disk reproducing device according to one embodiment of the present invention, input data read from the optical disk reproducing device is input from a terminal 30 of the phase comparator 10.
The phase comparator 10 supplies an UP signal and a DOWN signal according to the phase difference between the external input data and the internal clock to the charge pump circuits 11 and 12, respectively. The charge pump circuit 11 outputs a current Ic proportional to the UP signal width to a terminal 31, and outputs a current Ic proportional to the DOWN signal width to a terminal 3.
Pull in from 1. The charge pump circuit 12 similarly outputs and draws the current Ir to the terminal 32. The voltage-current converter 13 converts the voltage at the terminal 31 into a current Ic_val and applies the current Ic_val to the charge pump circuit 11. Similarly, the voltage-current converter 14 converts the voltage at the terminal 31 into a current Ir_val and applies the current Ir_val to the charge pump circuit 12. Capacitors C0 and C1,
The resistor R0 and the voltage-to-current converter 15 are a secondary filter, and generate a control voltage for the voltage-controlled oscillator 16. The oscillation frequency of the voltage controlled oscillator 16 changes according to the voltage of the terminal 32. The frequency divider 17 divides the output frequency of the voltage controlled oscillator 16 and uses it as an internal clock.
Output to It is constituted by the above.

The operation of the above-configured PLL circuit for an optical disk reproducing apparatus will be described in detail. When the data read from the optical disk and the internal clock synchronized with the read transfer data rate are input to the phase comparator 10, the phase difference information is output as an UP signal and a DOWN signal.
The charge pump circuit 11 has a current Ic proportional to the UP signal width.
Is output to the terminal 31, and a current Ic proportional to the DOWN signal width is drawn from the terminal 31. Charge pump circuit 12
Similarly, a current Ic proportional to the UP signal width is applied to the terminal 32.
Is output to the terminal 31 and the current Ic proportional to the DOWN signal width is output.
From the terminal 32. The voltage-current converter 13 has a conductance gm1, converts the voltage at the terminal 31 into a current Ic_val, and applies the current Ic_val to the charge pump circuit 11. Similarly, the voltage-current converter 14 has the conductance gm2 and the terminal 31
Is converted into a current Ir_val and applied to the charge pump circuit 12. gm1 and gm2 satisfy the relationship of Expression 1.

(Equation 1)

The capacitors C0 and C1, the resistor R0, and the voltage-to-current converter 15 are a secondary filter.
The charge of 0 increases or decreases, and the increase or decrease of the charge also increases or decreases the potential of the terminal 31. The potential of the terminal 32 is determined by the sum Ir of the current from the voltage-to-current converter 14 and the current from the charge pump circuit 12, and the capacitor C1. The oscillation frequency of the voltage-controlled oscillator 16 is determined by the voltage of the terminal 32. The output frequency of the voltage-controlled oscillator 16 is divided by the frequency divider 17 and input to the phase comparator 10.

The above circuit operation is performed by the loop of the PLL circuit of the present invention, whereby an internal clock synchronized with the input data can be obtained. Further, as the input data rate of CAV reproduction in this circuit operation continuously increases, the UP signal is continuously sent to the charge pump circuit 11, and the potential of the terminal 31 continuously increases.
The output current Ic_val of the voltage-current converter 13 increases in proportion to the voltage of the terminal 31. Similarly, the output current Ir_val of the voltage-current converter 14 also increases in proportion to the voltage of the terminal 31.
When the currents Ic and Ir continuously increase, PLL
The open loop gain band of the entire circuit increases as shown by the dotted line in FIG. The above operation will be described using the Laplace variable s.
(S) is represented by Equation 2, and FIG. 2 illustrates this. FIG. 4 shows that the unity gain (when the gain is 0) fu increases to fu ′ from Equations 3, 4 and 5, the corner frequencies f1 and f2 are constant, and the band of the open loop gain is continuously increased. It shows that it increases.

(Equation 2)

(Equation 3)

(Equation 4)

(Equation 5)

FIG. 4 shows an example of an internal circuit of the charge pump circuit 11. A constant current I1 flows through the resistor R1 from the reference voltage 71. The MOSFETs 50 and 51 constitute a current mirror circuit, and the MOSFET 51 has a constant current I
2 flows. The current Ic_val output from the voltage-current converter 13 in FIG. 1 is input to the terminal 73 in FIG.
The current I3 flowing through T52 is the sum of I2 and Ic_val.
The MOSFETs 52 and 53 constitute a current mirror circuit, and a current I4 flows through the MOSFETs 53 and 54.
The MOSFETs 52 and 58 are also current mirror circuits, and the current Ic flows. The MOSFETs 54 and 55 are current mirror circuits, and a current Ic flows through the MOSFET 55. MOSFET 56 is turned on and off by UP signal.
F is switched to output the current Ic to the terminal 76 in the ON state. The MOSFET 57 is switched between ON and OFF by the DOWN signal, and draws the current Ic from the terminal 76 in the ON state. The charge pump circuit is configured as described above.

The operation of the charge pump circuit having such a configuration will be described. Inside the charge pump circuit 11, a current I3 which is the sum of Ic_val input from the terminal 73 and the constant current I2 is generated. Ic output to terminal 76 is
It is proportional to the current I3 obtained by the current mirror circuit composed of the SFETs 52 and 53. Therefore, the current Ic is proportional to the current Ic_val. The charge pump circuit 12 has a similar circuit configuration, and generates a current Ir proportional to the current Ir_val. By continuously increasing the currents Ic and Ir, the bandwidth of the open loop gain of the entire PLL circuit can be increased as shown by the dotted line in FIG.

Next, a PL for an optical disk reproducing apparatus according to the present invention will be described.
Description will be given with reference to another embodiment of the charge pump circuit in the L circuit. FIG. 5 shows another embodiment of the charge pump circuit 11. MOSFET 59 is MOSFET5
0 and a current mirror circuit configuration. The switch 80 is connected to a current I2 flowing through the MOSFET 59.
a is turned ON / OFF. Similarly, the switch 81 is a MOSF
The current I2b flowing to the ET 51 is turned on / off. The switch 82 turns the current Ic_val input from the terminal 73 ON /
Turn off. The operation of the charge pump circuit having such a configuration will be described.

In CLV (Constant Liner Velocity) playback, the input data rate becomes constant, so that the open loop gain must also be constant. Therefore, by turning off the current Ic_val by the switch 82, the current I3 can be made constant. Further CLV
In order to cope with a change in the control speed of the reproduction speed, the magnitude of the current I3 can be selected from three of I2a, I2b, and I2a + I2b. From this, the current Ic is CL
A constant current suitable for V regeneration can be generated. Similarly, if the charge pump circuit 12 has the same circuit configuration, the current Ir can be a constant current. With such a configuration of the charge pump circuit, it is possible to cope with CLV reproduction, so that both the CLV reproduction and the CAV reproduction can be adopted by one PLL circuit. In this way, an efficient method can be selected, and the present invention can be used in an optical disc reproducing apparatus that combines CAV reproduction that is good at random access and CLV reproduction that can increase the transfer speed of continuous data.

[0020]

As described above, the PLL circuit for an optical disc reproducing apparatus according to the present invention can continuously increase the band of the open loop gain in accordance with an increase in the input data rate. This eliminates the band switching operation during the CAV reproducing operation of the optical disk, and makes it unnecessary to stop data transfer at the time of band switching.
In order to continuously increase the open loop gain of the above effect, the gain characteristic can be continuously changed by feeding back the conductance (change ratio of voltage to current) to the charge pump circuit as a feedback current. Also, by turning off the feedback current of the charge pump circuit, it is possible to cope with CLV reproduction. Therefore, CAV reproduction and CLV reproduction can be selectively used by one PLL circuit, and a reproduction method optimal for various formats of an optical disk is used. High-speed playback can be performed.

[Brief description of the drawings]

FIG. 1 shows a configuration of a PLL circuit for an optical disk reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a graph of Expression 1 according to an embodiment of the present invention.

FIG. 3 is a graph in which the increase in the open loop gain according to the embodiment of the present invention corresponds to the graph of Expression 1.

FIG. 4 is a circuit example of a charge pump circuit according to an embodiment of the present invention.

FIG. 5 is a circuit example of a charge pump circuit according to another embodiment of the present invention.

FIG. 6 shows a configuration of a conventional PLL circuit for an optical disk reproducing device.

FIG. 7 is a circuit example of a conventional charge pump circuit.

[Explanation of symbols]

 10 phase comparator 11, 12 charge pump circuit 13, 14 voltage-current converter (for gm) 15 voltage-current converter (filter) 16)------------------------------------------------------------------------------------------------------------

Claims (6)

[Claims] 1. A PLL circuit for an optical disk reproducing apparatus for reproducing an optical disk at a high speed, comprising: a phase comparator to which data read from the optical disk and an internal clock synchronized with input data in the PLL circuit are input; Oscillates with a voltage generated by a charge pump circuit that outputs a current proportional to the phase difference information output from the phase comparator, a voltage-current converter that converts a voltage to a current, a voltage-current converter, a charge pump circuit, and a capacitor A PLL circuit for an optical disk reproducing apparatus, comprising: a voltage-controlled oscillator that synchronizes a frequency with input data. 2. A PLL circuit for an optical disk reproducing apparatus, wherein said charge pump circuit converts a signal output from a phase comparator into a current proportional to a signal width. 3. The PLL circuit for an optical disk reproducing device, wherein the voltage-current converter is a conductance and converts a voltage into a current. 4. A PLL circuit for an optical disk reproducing device, wherein said voltage controlled oscillator changes an oscillation frequency according to an input voltage. 5. A PLL circuit for an optical disk reproducing apparatus, wherein said charge pump circuit is constituted by a plurality of current mirror circuits. 6. A method for continuously increasing an open loop gain for CAV reproduction of an optical disk at a high speed, wherein a signal corresponding to a phase difference is output from a phase comparator of a PLL circuit to a charge pump circuit, and the signal width of the signal is adjusted. A method of continuously increasing an open loop gain, comprising a procedure in which a proportional current is output from a charge pump circuit and fed back as a current from the voltage-current converter to the charge pump circuit.