JP2002043859A - Voltage-current converter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent fluctuation of a gain control current even when a gain control voltage fluctuates and to eliminate reproduction RF signal attenuation due to power supply voltage fluctuation without resetting the gain control voltage, thereby performing reproduction. Provided is a voltage-current conversion circuit that can reliably and accurately reproduce a recording signal on an optical disk even when the frequency of an RF signal increases. SOLUTION: An input voltage 10 and a power supply voltage 8 serving as a reference thereof are inputted, a fluctuation of the power supply voltage 8 is detected, and a current obtained by converting the input voltage 10 into a voltage-current conversion is detected using the detection result. By correcting an error caused by the fluctuation, a gain control current 17 having no error due to the fluctuation of the power supply voltage 8 is output as an output current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage / current conversion circuit for converting an input voltage as a gain control voltage into a gain control current as an output current when a focus error signal is generated in, for example, an optical disk reproducing apparatus. is there.

[0002]

2. Description of the Related Art Conventionally, for example, in a focus error signal generation circuit in an optical disk reproducing apparatus, a gain control circuit is used for focus balance control when generating a focus error signal. In an integrated circuit,
2. Description of the Related Art A voltage-current conversion circuit that converts an input voltage that is a gain control voltage of a gain control circuit into a gain control current that is an output current is widely used.

[0003] The above-described conventional voltage-current conversion circuit will be described below, taking as an example a circuit used in a focus error signal generation circuit in an optical disk reproducing apparatus.

FIG. 4 is a block diagram for explaining a focus error signal generating function in an optical disk reproducing apparatus using a conventional voltage-current conversion circuit. 4, reference numeral 1 denotes a photodetector for detecting a focus error, 2 denotes a focus error signal generation circuit, 3 denotes a focus balance control circuit, 4 and 5 denote gain control circuits used in the focus balance control circuit 3, and 6 denotes focus. A differential amplifier for generating an error signal, 7 is a voltage converter, 8 is a power supply voltage input to the voltage converter 7, 9 is a voltage conversion setting input input to the voltage converter 7, and 10 is a voltage converter 7 , The gain control voltage set by the voltage conversion setting input 9 with respect to the power supply voltage 8,
Is a voltage-to-current conversion circuit that converts the gain control voltage 10 as an input voltage into a current,
This is a gain control current, which is an output current output from No. 1.

[0005] The two signals of the photodetector 1 are input to a focus balance control circuit 3, and a gain control current 12 is current-converted by a voltage-current conversion circuit 11 based on a gain control voltage 10 by a voltage converter 7.
Gain control circuit 4 whose gain is controlled by
5 and is converted by a differential amplifier 6 into a focus error signal.

FIGS. 5A, 5B and 5C show changes in the gain control voltage 10 and the gain control current 12 with respect to changes in the voltage conversion setting input 9 in the conventional optical disk reproducing apparatus shown in FIG. FIG. FIG. 5A shows a temporal change of the voltage conversion setting input 9, FIG. 5B shows a temporal change of the gain control voltage 10,
FIG. 5C shows a temporal change of the gain control current 12.

The gain control voltage 10 is set by a voltage conversion setting input 9 based on the power supply voltage 8 input to the voltage converter 7. Gain control current 12
Converts the gain control voltage 10 input to the voltage-current converter 11 with a fixed conversion gain.

Therefore, as shown in FIG. 5A, when the voltage conversion setting input 9 is intentionally changed, the gain control voltage 10 changes and the gain control current 12 also changes. Thus, the function of gain control is realized. Here, the gain control voltage 10 is set so that the information surface of the optical disc and the focus of the light beam coincide when the focus error output from the differential amplifier 6 becomes zero.

FIGS. 6A, 6B and 6C show changes in the gain control voltage 10 and the gain control current 12 with respect to changes in the power supply voltage 8 in the conventional optical disk reproducing apparatus shown in FIG. It is a schematic diagram. FIG.
6A shows a temporal change of the power supply voltage 8, FIG. 6B shows a temporal change of the gain control voltage 10, and FIG. 6C shows a temporal change of the gain control current 12.

The gain control voltage 10 is set by a voltage conversion setting input 9 based on the power supply voltage 8 input to the voltage converter 7. Gain control current 1
2 converts the gain control voltage 10 input to the voltage / current conversion circuit 11 with a fixed conversion gain.

Therefore, as shown in FIG. 6A, even when the power supply voltage 8 changes unintentionally,
As shown in FIG. 6B, the gain control voltage 10 changes, and as shown in FIG. 6C, the gain control current 12 also changes.

As described above, when the preset gain control current 12 fluctuates, an error occurs in the focus error signal. In the optical disk reproducing device, the error of the focus error signal becomes a focus shift. Although the reproduction RF signal of the optical disk is slightly attenuated due to the focus shift, in the case of the reproduction speed in the CD reproduction, this amount of attenuation can be ignored and does not cause any problem.

FIG. 3 is a block diagram showing a configuration of a conventional voltage-current conversion circuit 11 provided in the focus error signal generation circuit 2 shown in FIG. 3, reference numeral 13 denotes a voltage-current converter, 14 denotes a voltage input terminal for inputting a gain control voltage 10 as an input voltage to the voltage-current converter 13, and 15 denotes a gain control which is an output current from the voltage-current converter 13. This is a current output terminal for outputting the current 12.

The operation of the conventional voltage / current conversion circuit 11 configured as described above will be described below. The input voltage 10 input from the voltage input terminal 14 to the voltage-current converter 13 is converted into a current by the voltage-current converter 13 according to a preset voltage-current conversion gain. Is output.

[0015]

However, in the conventional voltage-to-current conversion circuit as described above, the attenuation of the reproduced RF signal due to the focus shift becomes more susceptible to the higher frequency, and in the future, as represented by DVD, the reproduction of the optical disk will be more difficult. When the reproduction speed is increased and the frequency of the reproduction RF signal is increased, the attenuation of the reproduction RF signal due to the focus shift due to the power supply voltage fluctuation cannot be ignored, and the attenuation of the reproduction RF signal causes the reproduction of the recording signal on the optical disk. There was a problem that it became impossible.

On the other hand, the power supply voltage generally fluctuates, and it is easy to reset the gain control voltage each time so that the focus error becomes zero in accordance with such power supply fluctuation. There was also a problem that it could not be performed.

The present invention solves the above-mentioned conventional problems. Even if the gain control voltage fluctuates due to the fluctuation of the power supply voltage, the fluctuation of the gain control current can be prevented, and the gain control voltage can be prevented. In addition to eliminating the need for resetting, the attenuation of the reproduction RF signal due to the power supply voltage fluctuation is eliminated, and even if the frequency of the reproduction RF signal increases in response to the increase in the reproduction speed of the optical disk, the recording signal on the optical disk can be reduced. Provided is a voltage-current conversion circuit capable of reliably and accurately reproducing data.

[0018]

According to the present invention, there is provided a voltage-current conversion circuit for converting an input voltage to a current based on a predetermined arbitrary power supply voltage. Means for detecting a change in the power supply voltage, and an output current obtained by the voltage / current conversion,
The error caused by the fluctuation of the reference power supply voltage,
Means for canceling using the power supply voltage fluctuation information.

Thus, the input voltage and the reference power supply voltage are inputted, the fluctuation of the power supply voltage is detected, and the detection result is used to generate a current obtained by converting the input voltage into a current by the fluctuation of the power supply voltage. By correcting the error, the gain control current having no error due to the fluctuation of the power supply voltage can be output as the output current.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A voltage-current conversion circuit according to a first aspect of the present invention is a voltage-current conversion circuit for converting an input voltage into a voltage-current conversion with reference to a predetermined arbitrary power supply voltage. Means for detecting fluctuations, and means for canceling an error caused by fluctuations in the reference power supply voltage using the power supply voltage fluctuation information, for the output current obtained by the voltage-current conversion. Configuration.

A voltage-current conversion circuit according to a second aspect of the present invention is a voltage-current conversion circuit for converting an input voltage into a voltage-current conversion with reference to a predetermined arbitrary power supply voltage, wherein the first power-supply voltage is converted into a current. A voltage-current converter, a first variable amplifier that amplifies the converted current from the first voltage-current converter by variable gain, a reference current generating circuit that generates an arbitrary reference current, and the reference current generating circuit And a comparator that controls the gain of the first variable amplifier so that their current values become equal, and a comparator that converts the input voltage to a current. The second to convert
And a second variable amplifier that amplifies the converted current from the second voltage / current converter by changing the gain by the output of the comparator, and amplifying the converted current from the second voltage / current converter.
Is configured to control the gain of the variable amplifier to be equal to the gain of the first variable amplifier.

According to these configurations, an input voltage and a reference power supply voltage are input, and a change in the power supply voltage is detected.
By using the detection results to correct the error caused by the fluctuation of the power supply voltage for the current obtained by converting the input voltage to the voltage current, it is possible to output the gain control current without error due to the fluctuation of the power supply voltage as the output current. Make it possible.

Hereinafter, a voltage-current conversion circuit according to an embodiment of the present invention will be specifically described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of the voltage-current conversion circuit 16 according to the present embodiment. In FIG. 1, reference numeral 20 denotes a voltage / current converter (first voltage / current converter), reference numeral 21 denotes a power supply input terminal for inputting a power supply voltage 8 to the voltage / current converter 20, and reference numeral 22 denotes a current output of the voltage / current converter 20. , A reference current generating circuit, 23 compares a current generated by the reference current generating circuit 23 with a current amplified by the variable amplifier 22, and outputs A comparator for controlling the gain of the variable amplifier 22 to be equal; 30 a voltage-current converter (second voltage-current converter) having the same conversion gain as the voltage-current converter 20; 31
Is a voltage input terminal for inputting the input voltage 10 to the voltage / current converter 30, and 32 is a variable which is controlled by the comparator 24 with the current output of the voltage / current converter 30 as an input, and has the same gain as the gain of the variable amplifier 22. An amplifier (second variable amplifier) 33 is a current output terminal for outputting the output current 17 from the variable amplifier 32.

The operation of the voltage-to-current conversion circuit 16 of the present embodiment configured as described above will be described below. First, the power supply voltage 8 input from the power supply input terminal 21 to the voltage / current converter 20 is converted into a current by the variable amplifier 22.
Is input to The comparator 24 compares the reference current generated in advance by the reference current generating circuit 23 with the output current of the variable amplifier 22 and controls the variable amplifier 2 so that they become equal.
2 is controlled.

On the other hand, the input voltage 10 inputted from the voltage input terminal 31 to the voltage / current converter 30 is subjected to current conversion and inputted to the variable amplifier 32, and the gain control current 17 is outputted from the current output terminal 33 as an output current. . At this time, the gain of the variable amplifier 32 is controlled with the same gain as the variable amplifier 22 whose gain is controlled by the comparator 24. Therefore, the error of the gain control current 17 caused by the fluctuation of the power supply voltage 8 is canceled.

FIG. 2 is a block diagram showing a case where the above-described voltage / current conversion circuit 16 is used in a focus error signal generation circuit for generating a focus error signal in an optical disk reproducing apparatus.

FIGS. 7 (a), 7 (b) and 7 (c) show gains for a change in the voltage conversion setting input 9 in the optical disk reproducing apparatus using the voltage / current conversion circuit 16 of the present embodiment shown in FIG. FIG. 3 is a schematic diagram illustrating changes in a control voltage 10 and a gain control current 17. FIG.
FIG. 7A shows a temporal change of the voltage conversion setting input 9, FIG.
FIG. 7 shows a temporal change of the gain control voltage 10, FIG.
(C) is a temporal change of the gain control current 17.

The gain control voltage 10 is set by a voltage conversion setting input 9 based on the power supply voltage 8 input to the voltage converter 7. Gain control current 17
Converts current of the gain control voltage 10 input to the voltage-current conversion circuit 16 with a fixed conversion gain, and
This is a current in which an error due to the fluctuation of the power supply voltage 8 is canceled by the variable amplifier 22.

Therefore, when the voltage conversion setting input 9 is intentionally changed as shown in FIG.
As shown in FIG. 7B, the gain control voltage 10 changes, and as shown in FIG. 7C, the gain control current 17 also changes. Thus, the function of gain control is realized.

FIGS. 8 (a), 8 (b) and 8 (c) show gain control voltages corresponding to changes in the power supply voltage 8 in the optical disk reproducing apparatus using the voltage / current conversion circuit 16 of the present embodiment shown in FIG. FIG. 9 is a schematic diagram illustrating changes in 10 and gain control current 17. 8A shows a temporal change of the power supply voltage 8, FIG. 8B shows a temporal change of the gain control voltage 10, and FIG. 8C shows a temporal change of the gain control current 17.

The gain control voltage 10 is set by a voltage conversion setting input 9 based on the power supply voltage 8 input to the voltage converter 7. Gain control current 1
Reference numeral 7 denotes a current obtained by converting the gain control voltage 10 input to the voltage / current conversion circuit 16 into a current with a fixed conversion gain, and canceling an error due to a change in the power supply voltage 8 by the variable amplifier 22.

Therefore, as shown in FIG. 8A, when the power supply voltage 8 is unintentionally changed, as shown in FIG.
As shown in FIG. 8, the gain control voltage 10 changes, but as shown in FIG. 8C, the gain control current 17 does not change.

As described above, the input voltage 10 and the power supply voltage 8 as its reference are input, the fluctuation of the power supply voltage 8 is detected, and the detection result is used to calculate the current obtained by converting the input voltage 10 into a voltage-current. By correcting an error caused by a change in the power supply voltage 8, a gain control current 17 having no error due to a change in the power supply voltage 8 can be output as an output current.

As a result, even when the gain control voltage fluctuates due to the fluctuation of the power supply voltage, the fluctuation of the gain control current can be prevented, and the need to reset the gain control voltage is eliminated. Thus, even if the frequency of the reproduction RF signal is increased in response to the increase in the reproduction speed of the optical disk, the recording signal on the optical disk can be reproduced reliably and accurately.

[0035]

As described above, according to the present invention, the input voltage and the reference power supply voltage are input, the fluctuation of the power supply voltage is detected, and the input voltage is subjected to voltage-to-current conversion using the detection result. By correcting the error caused by the fluctuation of the power supply voltage, the gain control current without error due to the fluctuation of the power supply voltage can be output as the output current.

As described above, even when the gain control voltage fluctuates due to the fluctuation of the power supply voltage, the fluctuation of the gain control current can be prevented, and the need to reset the gain control voltage is eliminated. Thus, even if the frequency of the reproduction RF signal is increased in response to the increase in the reproduction speed of the optical disk, the recording signal on the optical disk can be reproduced reliably and accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a voltage-current conversion circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram for explaining a focus error signal generation function in the optical disc reproducing apparatus using the voltage-current conversion circuit of the embodiment;

FIG. 3 is a block diagram showing a configuration of a conventional voltage-current conversion circuit.

FIG. 4 is a block diagram for explaining a focus error signal generation function in an optical disk reproducing apparatus using the conventional voltage-current conversion circuit.

FIG. 5 is a schematic waveform diagram showing a state of each unit with respect to a change in a voltage conversion setting input in the conventional voltage-current conversion circuit.

FIG. 6 is a schematic waveform diagram showing the state of each unit with respect to a change in power supply voltage in the conventional voltage-current converter.

FIG. 7 is a schematic waveform diagram showing a state of each unit with respect to a change in a voltage conversion setting input in the voltage-current conversion circuit according to the embodiment of the present invention.

FIG. 8 is a schematic waveform diagram showing a state of each unit with respect to a change in a power supply voltage in the embodiment.

[Explanation of symbols]

 Reference Signs List 1 photodetector 2 focus error signal generation circuit 3 focus balance control circuit 4, 5 gain control circuit 6 differential amplifier 7 voltage converter 8 power supply voltage 9 voltage conversion setting input 10 gain control voltage (input voltage) 11 voltage current conversion circuit Reference Signs List 12 gain control current (output current) 13 voltage / current converter 14 voltage input terminal 15 current output terminal 16 voltage / current converter 17 gain control current (output current) 20 voltage / current converter 21 power supply input terminal 22 variable amplifier 23 reference current generation Circuit 24 Comparator 30 Voltage-current converter 31 Voltage input terminal 32 Variable amplifier 33 Current output terminal

Continued on the front page F term (reference) 5H410 BB02 BB05 CC02 DD02 FF03 FF16 FF18 GG01 JJ03 5J090 AA01 CA04 CA88 CN04 FA09 FN03 KA02 KA17 KA18 SA00 TA01 TA06 5J091 AA01 CA04 CA88 FA09 KA02 KA10 KA18 SA00 TA01 TA01

Claims (2)

[Claims] 1. A voltage / current conversion circuit for converting an input voltage into a voltage / current based on a predetermined arbitrary power supply voltage, comprising: means for detecting a change in the power supply voltage; and an output obtained by the voltage / current conversion. Means for canceling an error caused by the fluctuation of the reference power supply voltage using the fluctuation information of the power supply voltage. 2. A voltage / current conversion circuit for converting an input voltage into a voltage / current based on a predetermined arbitrary power supply voltage, wherein the first voltage / current converter converts the power supply voltage into a current.
A first variable amplifier that amplifies the converted current from the first voltage-current converter by varying the gain, a reference current generating circuit that generates an arbitrary reference current, a reference current from the reference current generating circuit, A comparator that compares the currents amplified by the first variable amplifier and controls the gain of the first variable amplifier so that their current values become equal; and a second voltage that converts the input voltage into a current. A current converter; and a second variable amplifier that amplifies the converted current from the second voltage-current converter by changing the gain according to the output of the comparator, wherein the comparator includes the second variable amplifier. A voltage-current conversion circuit configured to control the gain of the first variable amplifier to be equal to that of the first variable amplifier.