JPH0536614U - Focus drive circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] Control the abnormal current to the focus actuator by controlling the amplification of the drive circuit to be small against abnormal operation of the objective lens at power-on and power-off, and during disk playback. The objective lens and the disc are prevented from being damaged. [Structure] A series circuit of a first switch circuit and a first resistor connected in parallel to a feedback resistor of an inverting amplifier circuit of a focus actuator drive circuit, a second switch circuit and a second resistor. A first bias circuit that supplies a positive bias voltage to the first switch circuit, and a second bias circuit that supplies a negative bias voltage to the second switch circuit. It is configured to reduce the abnormal current flowing through the focus actuator.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a focus drive circuit of an optical disk player, and more particularly to a focus drive circuit suitable for reducing an abnormal current flowing to the focus actuator when power-on / power-off or reproduction of a dirty or damaged disk. ..

[0002]

[Prior art]

 Conventionally, many focus drive circuits having the circuit diagram shown in FIG. 3 have been provided. In the figure, reference numeral 1 denotes an input terminal of a focus drive circuit, to which a focus servo error signal received by a photo detector (not shown) of an optical disk player and converted into an electric signal is supplied.

Reference numeral 2 denotes an inverting amplifier circuit composed of an operational amplifier. The inverting amplifier circuit 2 amplifies the focus servo error signal supplied to the input terminal 1 and outputs a current proportional to the input signal voltage. Can be supplied to the focus actuator 3. The capacitors C1 and C2 of the inverting amplifier circuit 2 are capacitors for preventing oscillation and phase compensation.

As described above, the focus drive circuit can drive the focus actuator 3 to control the objective lens (not shown) in the vertical direction to focus on the disk and adjust the focus.

[0005]

[Problems to be solved by the device]

 However, in the conventional focus drive circuit described above, since the power supply voltage of the inverting amplifier circuit 2 is not stable when the optical disk player is powered on and off, an abnormal current flows through the focus actuator 3 and the objective lens moves abnormally in the vertical direction. In addition, there are drawbacks in that the focus adjustment operation causes abnormal noise, or the objective lens or the disk is damaged by coming into contact with the optical disk.

In addition, there is also a drawback that in the normal operation state of the optical disc player, by reproducing dirt or scratches on the disc, an abnormal current flows to the focus actuator 3 and the same problems as described above occur.

The present invention has been made in view of the above points, and an object thereof is to eliminate the drawbacks of the conventional example and to provide a drive circuit of a focus actuator with a series circuit of a switch circuit and a resistor, With respect to abnormal operation of the objective lens during disc playback, the amplification of the drive circuit is controlled to be small to reduce the abnormal current to the focus actuator and prevent damage to the objective lens and the disc. It is in the area of providing a focus drive circuit.

[0008]

[Means for Solving the Problems]

 The focus drive circuit of the present invention is a focus drive circuit using an inverting amplifier circuit as a focus actuator driving circuit of a pickup of an optical disk player, and a first switch circuit and a first switch circuit connected in parallel to a feedback resistor of the inverting amplifier circuit. A first bias circuit for supplying a positive bias voltage to the first switch circuit, wherein a series circuit with the first resistor circuit and a series circuit with the second switch circuit and the second resistor circuit are provided; And a second bias circuit for supplying a negative bias voltage to the second switch circuit to reduce an abnormal current flowing to the focus actuator during power-on / power-off of the optical disk player and during disk reproduction. It is composed.

Further, the first switch circuit and the second switch circuit may be composed of diode elements.

[0010]

[Action]

 According to this invention, an inverting amplifier circuit of an operational amplifier is used for a focus actuator drive circuit, a series circuit of a first switch circuit and a first resistor is provided in parallel with a feedback resistor of the inverting amplifier circuit, and The switch circuit and the series circuit of the second resistor are connected in parallel, and when the optical disc player is in the normal operation state, the first and second switch circuits are in the OFF state, and the inverting amplifier circuit is in the feedback resistor. It is possible to operate at the normal amplification degree of the instrument.

The OFF state of the first and second switch circuits is such that the first bias circuit that supplies a positive bias voltage to the first switch circuit and the negative bias voltage to the second switch circuit are negative bias voltage. Is biased by a second bias circuit that supplies

On the other hand, due to the fluctuation of the input signal voltage or the power supply voltage to the inverting amplifier circuit due to the inrush current of the power supply voltage when the optical disk player is powered on or off, the resistor connected in series to the focus actuator is An abnormal voltage is generated, and depending on the polarity of the generated abnormal voltage, the switch circuit of either the first or second switch circuit is turned ON via the first or second bias circuit, and the ON state is set. The resistor connected in series with the switch circuit serves as the feedback resistor of the inverting amplification circuit, and in parallel with the feedback resistor of the conventional inverting amplification circuit, the amplification degree of the inverting amplification circuit can be reduced.

That is, the abnormal current flowing into the focus actuator due to the turbulence of the focus servo system is controlled so that the drive current to the focus actuator is controlled to be small due to the reduction of the amplification degree of the inverting amplifier circuit. Abnormal vertical adjustment of the focus adjustment of the objective lens of the servo system can be suppressed to prevent generation of abnormal noise or damage to the disk.

Further, by configuring the first switch circuit and the second switch circuit with diode elements and supplying bias voltages to the diodes from positive and negative supply voltages, respectively, the same effect as described above can be obtained. Can be obtained.

[0015]

【Example】

 An embodiment of the focus drive circuit according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of an embodiment using a diode element. The same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, 4 is a first switch circuit connected in parallel to the feedback resistor R2 of the inverting amplifier circuit 2. This first switch circuit 4 and the first resistor R4 are series circuits. And 5 is a first bias circuit for biasing the first switch circuit 4, and the first bias circuit 5 is supplied with power from a positive supply voltage + V _B to form a bias circuit. is doing.

Reference numeral 6 is a second switch circuit connected in parallel to the feedback resistor R2 of the inverting amplifier circuit 2 like the first switch circuit 4, and the second switch circuit 6 is connected to the second resistor R5. And a bias voltage is supplied by a second bias circuit 7 that forms a series circuit with the bias voltage and is biased by the negative supply voltage -V _B.

In the focus drive circuit of the focus servo system of the optical disc player configured as described above, for example, as shown in the circuit diagram of FIG. 2, the first switch circuit 4 is formed by the first diode D1. 1 is connected to the positive supply voltage + V _B via the resistor R6 from the connection point A with the first resistor R4 connected in series with the diode D1 and is further grounded from the connection point A to the capacitor C3. , The second switch circuit 6 is formed by the second diode D2, and the connection point B with the second resistor R5 connected in series with the second diode D2 is a negative supply voltage via the resistor R7- It is configured to be connected to V _B and further grounded from the connection point B by a capacitor C4.

In the normal operation state of the optical disc player, the node of the first diode D1 is virtually grounded, and the cathode of the first diode D1 divides the positive supply voltage + V _B by the resistors R6, R4, R3. The first diode D1 is in the OFF state because it is biased by the positive voltage that is applied. On the other hand, the second diode D2 is connected in reverse polarity to the first diode D1, the cathode of the second diode D2 is virtually grounded, and the anode has a negative supply voltage -V _B to the resistors R7, R5, R6. It is divided by and is biased with a negative voltage and is in the OFF state.

That is, in the normal operation state, the inverting amplifier circuit 2 operates with the amplification degree by the feedback resistor R2, and supplies the drive current proportional to the input voltage to the focus actuator 3 by the same operation as the circuit of the conventional example. A focus servo system can be formed.

On the other hand, abnormal operation of the focus servo system caused by fluctuation of input signal voltage or power supply voltage to the inverting amplifier circuit due to inrush current of power supply voltage at power-on or power-off of optical disk player , And abnormal current flows to the focus actuator 3 due to abnormal operation of the focus servo system that occurs during reproduction such as dirt and scratches on the disc.

A voltage accompanying the abnormal current flowing into the focus actuator 3 is generated in the resistor R3, and the first or second diode D1, D2 is controlled to be ON by the polarity of the generated voltage. For example, if the abnormal current flowing through the focus actuator 3 is a positive current and this positive current increases, a positive voltage will be generated in the resistor R3, and the positive supply voltage + V _B The connection point A of the first diode D1 biased by the first bias circuit 5 composed of the resistors R6, R4 and R3, and the negative supply voltage -V _B and the resistors R7, R5 and R3. The bias voltage of the connection point B of the second diode D2 biased by the second bias circuit 7 rises and the first diode D1 maintains the OFF state, but the second diode D2 of the connection point B changes. It is turned on by the bias voltage raised to the positive voltage.

In this way, when the abnormal current of the focus actuator 3 is detected and the second diode D2 is turned on, the feedback resistor R2 of the inverting amplifier circuit 2 is connected in series with the second diode D2. The second resistor R5 is connected in parallel and operates so as to reduce the amplification degree of the inverting amplifier circuit 2. As a result, the drive current supplied to the focus actuator 3 is reduced, and The focus adjustment operation is limited, and it is possible to prevent problems caused by abnormal focus adjustment operations of the objective lens up and down.

On the contrary, when the abnormal current flowing through the focus actuator 3 is a large negative current, a negative voltage is generated in the resistor R3 contrary to the above, and the first and second bias circuits are generated. The bias voltage of the connection points A and B of 5,7 can be set in the negative voltage direction to turn on the first diode D1, and the second diode D2 is kept off.

That is, the feedback resistor R2 of the inverting amplifier circuit 2 is connected in parallel with the first resistor R4 that is connected in series with the first diode D1 to reduce the amplification degree of the inverting amplifier circuit 2 and The drive current supplied to the scrap actuator 3 can be reduced to limit the abnormal vertical focus adjustment operation of the objective lens.

Further, for the high frequency component of the abnormal current flowing through the focus actuator 3, the resistor R4 and the capacitor C3 of the first or second bias circuit 5 and 7, and the resistor R5 and the capacitor Since C4 and the low-pass filter circuit constitute the low-pass frequency component, the high-frequency component can be reduced, and the first or second diode D1, D2 of the switch circuit is turned on / off by this high-frequency component. It is possible to eliminate such problems.

In this way, it is possible to detect abnormal current flowing in the focus actuator 3 and control the amplification degree of the inverting amplification circuit 2 of the focus drive circuit to prevent problems such as abnormal noise due to the operation of the objective lens. it can.

[0028]

[Effect of the device]

 As described above, the focus drive circuit according to the present invention detects fluctuations in power supply voltage at power-on or power-off, and abnormal current flowing in the focus actuator by reproducing dirt and scratches on the disk, thereby performing focus drive. By controlling the amplification degree of the inverting amplifier circuit in the circuit and limiting the focus adjustment of the vertical movement of the objective lens, it is possible to prevent abnormal noise due to abnormal vertical movement and damage to the objective lens and the disk. There is an effect.

Further, since the dynamic range of the vertical movement of the focus adjustment of the objective lens is not affected by the surface wobbling at the time of reproducing the disc, the objective lens does not come into contact with the disc and the smooth focus adjustment operation is performed. It also has the effect of being able to follow the disc.

Further, the function of controlling the drive current of the focus actuator with a control signal such as a reset signal at the time of power-on, which has been conventionally used, controls the amplification degree of the focus drive circuit of the present invention to an abnormal current. There is also an effect that the control circuit for the above-mentioned control signals can be eliminated and the circuit configuration can be simplified because it is unnecessary just by controlling.

Moreover, it has excellent features such as a simple structure and easy implementation because it can be constructed at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a focus drive circuit according to the present invention.

FIG. 2 is a circuit diagram showing an example.

FIG. 3 is a block diagram showing a conventional example.

[Explanation of symbols]

 1 Input Terminal of Focus Drive Circuit 2 Inversion Amplifier Circuit 3 Focus Actuator 4 First Switch Circuit 5 First Bias Circuit 6 Second Switch Circuit 7 Second Bias Circuit A First Diode D1 and First Resistor Connection point with resistor R4 B Connection point between second diode D2 and second resistor R5

Claims (2)

[Scope of utility model registration request] 1. A focus drive circuit for an optical disc player, which uses an inverting amplifier circuit for a focus actuator driving circuit of a pickup, wherein a feedback switch of the inverting amplifier circuit comprises a first switch circuit and a first resistor in series. A circuit, a second switch circuit and a series circuit of a second resistor are connected in parallel, a first bias circuit for supplying a positive bias voltage to the first switch circuit, and the second switch A focus drive circuit, comprising: a second bias circuit that supplies a negative bias voltage to the circuit, thereby reducing an abnormal current flowing through the focus actuator. 2. The focus drive circuit according to claim 1, wherein the first switch circuit and the second switch circuit are diode elements.