JPH0528519A - Protective circuit for actuator - Google Patents

Abstract

PURPOSE:To provide a protective circuit for an actuator capable of eliminating the deviation of a focusing point with respect to a transitional disturbance while protecting the actuator. CONSTITUTION:This device is provided with a monitoring means 16 detecting the driving signal of the actuator 10, an integration circuit 18 inputting the detective signal of the monitoring means and integrating it by a prescribed time constant and a comparator 20 comparing the integration output of the integration circuit and a prescribed constant K and interrupting the supply of the driving signal of the actuator when the integration output is larger. Since the device is constituted so that the supply of the driving signal is interrupted only when the driving signal of the actuator exceeds the prescribed constant K and flows continuously, the large driving current to suppress the disturbance is supplied when the transitional disturbance is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit for an actuator of a drive device such as an optical disk or a magneto-optical disk (hereinafter referred to as optical disk).

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
The protection of the focus actuator of the optical disk drive has been performed by, for example, limiting the drive current supplied to the focus actuator by the maximum rated direct current. However, for example, in a state where autofocus is applied to a grooved disk, crosstalk may occur due to the groove unevenness. If a large transient disturbance that exceeds the dynamic range of focus control such as the effect of this crosstalk occurs, the drive current will be limited by the driver, and the actuator must be adjusted to suppress the transient disturbance. Although more current was required to drive, there was not enough current to suppress the disturbance, which resulted in servo displacement. Therefore, there is a problem that the responsiveness to the transient disturbance is not good and the focus point is displaced.

The present invention has been made in order to solve such a problem, and protects the actuator, and at the same time protects the actuator, which makes it possible to eliminate the shift of the focus point against a transient disturbance. The purpose is to provide a circuit.

[0004]

An actuator protection circuit of the present invention comprises a monitor means for detecting a drive signal of the actuator, an integrating circuit for receiving the detection signal of the monitor means, and integrating it with a predetermined time constant. And a comparator that compares the integrated output of the integrating circuit with a predetermined constant and stops the supply of the drive signal of the actuator when the integrated output is large.

[0005]

In the present invention, even if the value indicated by the drive signal of the actuator instantaneously becomes larger than a predetermined constant (hereinafter referred to as constant K), the detection signal of the drive signal is integrated by the integrating circuit. , The integral output of the integrator circuit is a constant K
The actuator drive signal is smaller and continues to be supplied. Therefore, when a transient disturbance occurs, a drive signal corresponding to a large value for suppressing the disturbance is supplied, and the response to the transient disturbance is improved. However, when the value indicated by the drive signal of the actuator exceeds the constant K and is continuously supplied in steps, the integrated output becomes larger than the constant K, and the comparator stops the supply of the drive signal of the actuator. In this way, the actuator is protected by stopping the supply of the drive signal to the actuator.

[0006]

1 is a block diagram of an actuator protection circuit according to an embodiment of the present invention. In the figure, a disk 4 is mounted on a spindle 2, and the disk 4 is rotated by driving the spindle 2. A carriage 6 is arranged close to the disk 4, and the carriage 6 moves in the diameter direction of the disk 4. An optical pickup 8 incorporating a laser light emitting element, a light receiving element and the like is mounted on the carriage 6. The optical pickup 8 is also equipped with an autofocus actuator (referred to as an AF actuator) 10 that adjusts the focus of the laser. Optical pickup 8
The variation signal from the autofocus control circuit (hereinafter AF
Control circuit) 12, and the control signal obtained by the AF control circuit 12 is input to the driver 14. The driver 14 supplies a drive current based on the control signal to the AF actuator 10 to drive the AF actuator 10 to drive the laser. Adjust the focus.

At this time, the current monitor 16 detects the drive current, converts it into a voltage, and outputs it to the integrating circuit 18. The integrating circuit 18 integrates the detection signal corresponding to the drive current with a predetermined time constant as described later. The comparator 20 is an integrating circuit 1
8 is compared with the output K of the maximum value setting circuit 22. For example, when the output of the integrating circuit 18 is high, the power supply circuit 2
Switch 2 provided between the driver 4 and the driver 10
6 is opened to cut off the power supply to the driver 14 and stop the supply of the drive current.

Next, the time constant T of the integrating circuit 18 will be described. A time constant T is set in the integrating circuit 18,
A drive current detection signal from the current monitor 16 is input, and charging / discharging is performed with a time constant T.

FIG. 2 is a characteristic diagram of the integrating circuit 18. In the figure, K is the output of the maximum value setting circuit 22 (hereinafter, simply referred to as a constant), and is set to a signal level corresponding to the drive current that can be constantly supplied. Here, the relationship between the time constant T and the constant K is as follows. (1) The maximum DC rated current of the AF actuator is a (A) and b (sec). (Protection conditions) (2) The actual use conditions of the AF actuator are (when seeking, immediately after the end of seek → until tracking) a1 (A) and b1 (sec). However, the relationship between a1 and a and b1 and b is as follows.

[0010]

[Equation 1] Therefore, the setting condition of the constant K is as follows from the above equation.

[0011]

[Equation 2]

In normal operation, the current supplied to the AF actuator 10 swings positively and negatively around "0", and the integral output of the integrator circuit 18 repeats charging and discharging by itself. It is almost “0”. Then, even if a transiently large current flows, if the excessive current does not flow before the time set by the time constant T, the integrated output drops before reaching the constant K, so the integrated output The state of the constant K continues, and the drive current is not cut off.

FIG. 3 is a timing chart showing the state at this time. As shown in this figure, when the drive current of the AF actuator 10 rises in a pulse shape as shown in the figure, it is detected by the current monitor 16 and the output of the integrating circuit 18 is time constant T as shown by the broken line. When the drive current falls, it is discharged at the time constant T and falls. Therefore, the integration circuit 18
The integrated output of the power supply drops before reaching the constant K, and the integrated output is smaller than the constant K. Even if the drive current instantaneously becomes larger than the constant K, the comparator 20 does not open the switch 26. Keeps flowing. The drive current at this time exceeds the constant K, but the time is short, so there is no risk of damaging the actuator. In this way, the drive current can be supplied to an instantaneous disturbance without limiting it, so if a transient disturbance occurs, a large drive current for suppressing the disturbance can be obtained, Good response to general disturbances.

However, when the drive current of the actuator rises stepwise and exceeds the constant K and its amplitude value continues, the integrated output of the integrating circuit 18 is the time constant T.
May exceed the value of the rising constant K. At this time, the comparator 20 opens the switch 26 to cut off the driving power source of the driver 14, the driver 14 stops its driving, and the supply of the driving current is stopped. By stopping the supply of the drive current in this manner, the AF actuator 1
0 is protected. In addition, the cutoff of the drive current is not limited to the cutoff of the drive power source for the driver 14 as described above, and for example, a switch may be provided in the path through which the drive current flows to open and close the switch.

[0015]

As described above, according to the present invention, the supply of the drive signal is stopped only when the value indicated by the drive signal of the actuator exceeds the value corresponding to the predetermined constant K and is continuously supplied. As a result, the actuator is properly protected, and when a transient disturbance occurs, it is possible to supply a drive signal corresponding to a large value to suppress the disturbance, and Responsiveness to various disturbances has improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a protection circuit for an actuator according to an embodiment of the present invention.

FIG. 2 is an operation waveform diagram of an integrating circuit.

FIG. 3 is a waveform diagram illustrating the operation of the embodiment of FIG.

[Explanation of symbols]

 8 Optical Pickup 10 AF Actuator 12 AF Control Circuit 14 Driver 16 Current Monitor 18 Integrator Circuit 20 Comparator 26 Switch

Claims (1)

Claim: What is claimed is: 1. Monitor means for detecting a drive signal of an actuator, an integration circuit for receiving a detection signal of the monitor means and integrating the detection signal with a predetermined time constant, and an integration output of the integration circuit. A protection circuit for an actuator, comprising: a comparator that compares a predetermined constant and stops the supply of a drive signal for the actuator when the integrated output is large.