JP2000082255A - Voltage control oscillation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage control oscillation circuit capable of setting an oscillating range according to each of the double-speed reproducing of plural kinds in an optical disk player. SOLUTION: This voltage control oscillation circuit is composed of a current source 7, a differential amplifier circuit 8 for controlling an output current based on a control voltage and an oscillation clock generating circuit 9 for generating the clock of an oscillation frequency according to the output current of the differential amplifier circuit 8, and the power source 7 is constituted of an N channel transistor 51 for supplying a drain current to the differential amplifier circuit 8, N channel transistors 1, 21,..., N1 connected in parallel between a reference current line 10 and a ground and switches 12, 22,..., N2. The reference current line 10 is connected to the gates of the respective transistors 11, 21,..., N1 by the switches 12, 22,...,N2. By controlling the turning ON/OFF of the switches 12 to N2, a current supplied from the current source 7 to the differential amplifier circuit 8 is changed, and the oscillating range of the oscillation output of the oscillation clock generating circuit 9 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CD player, C
D-ROM drive, DVD player, DVD-ROM
In an optical disc reproducing device such as a drive, a constant angular velocity (Constant Angular Velocity)
(hereinafter, referred to as “CAV method”).

[0002]

2. Description of the Related Art FIG. 6 shows a configuration diagram of a reproduction signal processing section of an optical disk including a conventional voltage controlled oscillation circuit. In FIG. 6, 1 is an optical disk such as a CD or CD-ROM, 2 is a pickup, 3 is a head amplifier, 4 is a data slice circuit, 5 is a PLL circuit, and 6 is a voltage controlled oscillation circuit.

Digital information is recorded on the reproduction surface of the optical disk 1, and is rotated at a predetermined rotation speed during reproduction. Then, the information recorded on the optical disc 1 is read by the pickup 2 as a difference in reflectance, and the value is converted into a voltage value and output. Next, the head amplifier 3 amplifies and equalizes the output from the pickup 2 and outputs it as an RF signal. In the case of the CAV optical disk reproducing apparatus, the RF signal is output at a frequency proportional to the linear velocity of the optical disk 1. Since this RF signal is an analog signal, it is converted into an H (high) or L (low) digital signal (binary signal) by the data slice circuit 4. This binarized signal is sent to the PLL circuit 5. PLL
The circuit 5 restores digital information recorded on the optical disc 1 from the binarized signal using an extraction clock synchronized with the binarized signal generated by the voltage controlled oscillation circuit 6.

FIG. 7 shows a conventional configuration of the voltage controlled oscillation circuit 6. As shown in FIG. The conventional voltage controlled oscillation circuit shown in FIG. 7 includes a current source 7 composed of a current mirror circuit composed of an N-channel transistor 50 and an N-channel transistor 51.
And a differential amplifier circuit 8 for controlling the amount of current by voltage control
And an oscillation clock generation circuit 9 for current control. Reference current line 10 to which a reference current is externally input
Are connected to the gate and drain of the transistor 50 and the gate of the transistor 51.

A current source 7 outputs a reference current supplied from the outside to a differential amplifier circuit 8 through a current mirror circuit used as a constant current source. The differential amplifier circuit 8 amplifies the current supplied from the current source 7 in accordance with the control voltage to generate an output current. The oscillation clock generation circuit 9 receives the output current of the differential amplifier circuit 8 and generates a clock having an oscillation frequency according to the output current. When the output current of the differential amplifier circuit 8 increases, the oscillation clock generation circuit 9 increases the switching speed of the transistor provided therein and increases the oscillation frequency. The output current of the differential amplifier circuit 8 increases as the current from the current source 7 increases and the control voltage increases. Therefore, the current source 7
2 and the control voltage of the differential amplifier circuit 8, the output current of the differential amplifier circuit 8 increases, and the oscillation frequency of the oscillation clock generation circuit 9 increases (however, FIG. , There is a saturation region as shown in FIG. 3).

In the case of a CAV type optical disk reproducing apparatus,
Since the angular velocity is constant, the linear velocity of the optical disc 1 is different by about 2.5 times between the outer circumference and the inner circumference. Therefore, as shown in FIG. 2, for example, as shown in FIG. Requires a 56 MHz synchronous clock. FIG. 2 is a diagram showing the relationship between the control voltage and the oscillation frequency in the case of the outermost circumference 32 × speed reproduction in the CAV method, and FIG. 3 is the control voltage and the oscillation frequency in the case of the outermost circumference 20 × speed reproduction in the CAV method. FIG.

[0007]

In the configuration of the above-mentioned conventional voltage controlled oscillation circuit, for example, CAV of 32x speed reproduction at the outermost circumference is used.
When the oscillator is designed to oscillate in the synchronous clock range of about 140 MHz to 56 MHz corresponding to the optical disk reproducing apparatus of the system, for example, the oscillation range of the synchronous clock required even if it is applied to the CAV optical disk reproducing apparatus of the outermost circumference 20 times speed reproduction As shown in FIG. 3, since the frequency is from 90 MHz to 35 MHz, a synchronous clock at or near the lower limit cannot be obtained, and the current source 7 or the differential amplifier circuit 8 for adjusting the current amount is newly designed. Needed.

An object of the present invention is to provide a voltage controlled oscillation circuit capable of setting an oscillation range according to a plurality of types of double speed reproduction in an optical disc reproducing apparatus.

[0009]

According to a first aspect of the present invention, there is provided a voltage controlled oscillation circuit comprising: a current source; a differential amplifier circuit for amplifying and outputting a current supplied from the current source according to a control voltage;
An oscillation clock generation circuit that generates a clock having an oscillation frequency according to the output current of the differential amplifier circuit. The current source has a gate connected to a reference current line to which a reference current is input. A first transistor connected to supply a drain current to the differential amplifier circuit, a plurality of second transistors each connected in parallel between the reference current line and the ground, and a plurality of second transistors each connected to the reference current line and the plurality of second transistors. And a plurality of switches connected between the respective gates of the transistors.

According to this configuration, the on / off of the plurality of second transistors provided in the current source is controlled by the respective switches, thereby controlling the current supplied from the current source, and controlling the oscillation clock generation circuit. The output oscillation range can be changed. A voltage controlled oscillation circuit according to a second aspect of the present invention is the voltage controlled oscillation circuit according to the first aspect, wherein one of the plurality of switches is replaced with a gate of a second transistor corresponding to the one switch. The reference current line is directly connected.

As described above, for example, the number of switches can be reduced by eliminating one switch of the second transistor to be normally turned on and directly connecting the reference current line to the gate.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a voltage controlled oscillator circuit according to a first embodiment of the present invention. In FIG. 1, reference numeral 7 denotes a current source, 8 denotes a differential amplifier circuit that controls a current amount by voltage control, and 9 denotes a current amplifier. The control oscillation clock generation circuit 10 is a reference current line.

The configuration of the reproduction signal processing section of the optical disk including the voltage controlled oscillation circuit of the present embodiment is the same as that of the conventional example shown in FIG. 6, and is shown in FIG. 1 as the voltage controlled oscillation circuit 6 of FIG. A voltage controlled oscillator circuit is used. The voltage controlled oscillation circuit according to the present embodiment includes a current source 7, a differential amplifier circuit 8,
The differential amplifier 8 and the oscillation clock generator 9 are the same as those in the conventional example shown in FIG. 7, and thus the detailed description thereof is omitted.

The current source 7 in the present embodiment has a gate connected to the reference current line 10, a source connected to the ground, a drain connected to the differential amplifier circuit 8, and supplies a drain current to the differential amplifier circuit 8. N-channel transistor 5
1 (first transistor), two N-channel transistors 11 and 21 (second transistor), and two switches 12 and 22. Transistor 11,
Reference numeral 21 indicates that each drain is connected to the reference current line 10 and the source is connected to the ground, so that the reference current line 10 and the ground are connected in parallel. Line 10
Is connected.

The operation of the thus-configured voltage controlled oscillation circuit of this embodiment will be described. First, when the switch 12 is turned on to turn on the transistor 11, and the switch 22 is turned off to turn off the transistor 21, the configuration is the same as that of the conventional example shown in FIG. Therefore, when designed for 32 × speed reproduction, the oscillation output of the oscillation clock generation circuit 9 can be adjusted to about 140 M by adjusting the control voltage of the differential amplifier circuit 8 as shown in FIG.
An oscillation range from Hz to 56 MHz is obtained.

Next, when the switch 12 is turned on to turn on the transistor 11 and the switch 22 is turned on to turn on the transistor 21, the drain current flowing through the transistor 11 is set to I ₁₁ and the transistor 21 is turned on. Assuming that the flowing drain current is I ₂₁ , the drain current flowing through the transistor 51, that is, the current supplied by the current source 7 is (I ₁₁ × I ₂₁ ) / (I ₁₁ + I ₂₁ ). If the transistor 11 and the transistor 21 are the same (same dimension) transistor, the current supplied from the current source 7 is の of the current flowing through one transistor 11 (or 21). In this case, as a result of the circuit simulation, the oscillation output of the oscillation clock generation circuit 9 can obtain an oscillation range of about 90 MHz to 35 MHz by adjusting the control voltage of the differential amplifier circuit 8 as shown in FIG. .

Therefore, according to the present embodiment, FIG.
As shown in (1), an oscillation range corresponding to 32 × speed reproduction and 20 × speed reproduction can be obtained with a single voltage controlled oscillation circuit. Next, a second embodiment of the present invention will be described. FIG. 5 is a configuration diagram of a voltage controlled oscillation circuit according to a second embodiment of the present invention, and the current source 7 is different from FIG. The differential amplifying circuit 8 and the oscillation clock generating circuit 9 are the same as those shown in FIG. 1 and the conventional example shown in FIG.

The second embodiment is basically similar to the first embodiment.
This is the same idea as the embodiment. As the current source 7,
In the first embodiment, in addition to the transistor 51 that supplies a current to the differential amplifier circuit 8, two transistors 11,
21 and switches 12 and 22,
In the second embodiment, three or more transistors 11,
... N1 and switches 12, 22,.
2 is used.

The operation of the thus-configured voltage controlled oscillation circuit according to the present embodiment will be described. First, when the switch 12 is turned on to turn on the transistor 11, and the switch 22 is turned off to turn off the transistor 21, the configuration is the same as that of the conventional example shown in FIG. Therefore, when designed for 32 × speed reproduction, the oscillation output of the oscillation clock generation circuit 9 can be adjusted to about 140 M by adjusting the control voltage of the differential amplifier circuit 8 as shown in FIG.
An oscillation range from Hz to 56 MHz is obtained.

Next, when the transistors 11 to N1 are turned on or off by the switches 12 to N2, respectively, the current supplied from the current source 7 to the differential amplifier circuit 8 can be changed by the combination thereof, and The oscillation range of the oscillation output of the clock generation circuit 9 can be changed. Therefore, a single voltage-controlled oscillation circuit can provide oscillation ranges corresponding to various double-speed reproductions of 32 times or less.

As described above, the voltage-controlled oscillation circuit according to the present embodiment can cope with the oscillation range of the CAV type optical disc reproducing apparatus having various reproducing speeds. In addition,
In the embodiment shown in FIGS. 1 and 5, for example, if the transistor 11 is always used in an on state, the switch 12 is eliminated and the reference current line 10 is directly connected to the gate of the transistor 11 so that one The number of switches 12 can be reduced.

Although the optical disk 1 of the optical disk reproducing apparatus using the voltage controlled oscillation circuits of the first and second embodiments is a CD, a CD-ROM or the like, if the optical disk reproducing apparatus of the CAV system is a CD-ROM. Other CD media such as R and CD-RW, or DVD, DVD-ROM,
DVD media such as DVD-RAM, MO and PD may be used.

[0023]

As described above, according to the present invention, a first transistor having a gate connected to a reference current line and supplying a drain current to a differential amplifier circuit as a current source, and a current source between the reference current line and ground are provided. A plurality of second transistors each connected in parallel, and a plurality of switches each connected between the reference current line and the gate of each of the plurality of second transistors. By controlling on / off of the transistors by respective switches, the current supplied from the current source can be controlled and the oscillation range of the output of the oscillation clock generation circuit can be changed. It is possible to cope with the oscillation range of the optical disc reproducing apparatus of the system.

In addition, the number of switches can be reduced by connecting a reference current line directly to the gate of the second transistor corresponding to the one switch instead of one of the plurality of switches. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a voltage controlled oscillation circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a control voltage and an oscillation frequency in the case of 32 × speed reproduction at the outermost circumference in the CAV method.

FIG. 3 is a diagram showing a relationship between a control voltage and an oscillation frequency in the case of 20 × speed reproduction at the outermost circumference in the CAV method.

FIG. 4 is a diagram showing a relationship between a control voltage and an oscillation frequency of the voltage controlled oscillation circuit according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram of a voltage controlled oscillation circuit according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a reproduction signal processing unit of an optical disk including a voltage controlled oscillation circuit.

FIG. 7 is a configuration diagram of a conventional voltage controlled oscillation circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Pickup 3 Head amplifier 4 Data slice circuit 5 PLL circuit 6 Voltage control oscillation circuit 7 Current source 8 Differential amplification circuit 9 Oscillation clock generation circuit 10 Reference current line 11, 21, N1 N channel transistor (2nd transistor) 12, 22, N2 switch 51 N-channel transistor (first transistor)

Claims (2)

[Claims] 1. A current source, a differential amplifier circuit for amplifying and outputting a current supplied from the current source according to a control voltage, and a clock having an oscillation frequency corresponding to an output current of the differential amplifier circuit A voltage-controlled oscillation circuit comprising: an oscillation clock generation circuit that generates a first current; and a first current source having a gate connected to a reference current line to which a reference current is input and supplying a drain current to the differential amplifier circuit. A plurality of second transistors, each of which is connected in parallel between the reference current line and the ground,
A voltage controlled oscillation circuit, comprising: a plurality of switches each connected between the reference current line and a gate of each of the plurality of second transistors. 2. The voltage controlled oscillation circuit according to claim 1, wherein a reference current line is directly connected to a gate of a second transistor corresponding to the one switch, instead of one of the plurality of switches.