JPH04105857U - CD player disk motor servo circuit - Google Patents

Abstract

(57) [Summary] [Objective] To provide a disk motor servo circuit for a CD player that switches servo gain depending on the size of the disk loaded in the CD player. [Structure] In a disc motor servo circuit of a CD player equipped with a selector switch ₁₄₁ for changing the gain of the servo circuit, a startup period length determination circuit 17 is provided to determine whether the startup period is longer than a predetermined period. A startup period length determination circuit 1 is provided.
The selector switch 14 ₁ is changed in accordance with the output of 7.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention relates to the disc motor servo circuit of a CD player, and more specifically to the disc motor servo circuit of a CD player. The present invention relates to a disk motor servo circuit that switches gain depending on disk size.

0002

[Conventional technology]

The conventional disc motor servo circuit of a CD player is as shown in Figure 3. The EMF signal detected from the disk 10 is supplied to the servo amplifier 1 and amplified, and the amplified output is is supplied to the gain switching circuit 2 to change the gain selected in the gain switching circuit 2. The signal is multiplied and supplied to the drive amplifier 3 for amplification to drive the disc motor 4. The in-switching circuit 2 is configured to select whether the disk is 8cm or 12cm. The output detected by the detection circuit 5 that optically detects the difference in size is supplied to the The gain of the disk motor servo circuit is changed by changing the gain according to the disk size. It was happening.

0003

[Problem that the idea aims to solve]

However, the detection circuit that optically detects the disc size is expensive; It cannot be applied to CD players, making it an optimal device for low-priced CD players. There was a problem in that it was not possible to operate the disk servo. This invention is ideal for disc motor servo circuits and is an inexpensive disc motor servo circuit. The purpose is to provide a bot circuit.

0004

[Means to solve the problem]

The disc motor servo circuit of the present invention has a gain switch that switches the gain of the servo circuit. In the disc motor servo circuit of a CD player equipped with a replacement circuit, the startup period is A startup period length determining means for determining whether the period is longer than a predetermined period is provided, and the startup period length determining means The gain switching circuit is characterized in that the gain switching circuit is switched in accordance with the output of.

[0005]

[Effect]

The disk motor servo circuit of the present invention configured as described above is When the diameter of the disk is large, the inertia is large and the start-up period is long and exceeds the specified period. When the diameter of the attached disk is small, the inertia is small and the startup period is short and the predetermined period is long. less than or equal to the length of the disk, and the size of the disk is substantially determined by the predetermined period length determining means. , the gain of the disk motor servo circuit is switched. It will be done.

[0006]

【Example】

The present invention will be explained below with reference to examples. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. The EMF signal detected from the disk 10 is supplied to the synchronization signal detection circuit 11, which detects the synchronization signal from the EFM signal, and compares the detected synchronization signal and the reference clock signal with the period of the detected synchronization signal and the period of the reference clock signal. The signal is supplied to a comparator 12 which compares the length of the period. This comparison output is supplied to a low-pass filter 13 for smoothing, and the output of the low-pass filter 13 is supplied to a servo amplifier 14 whose gain is switchable. The output of the servo amplifier 14 is supplied as an inverting input to the motor drive amplifier 15 to which a voltage 1/2 Vcc is applied as a non-inverting input and amplified, and the output of the motor drive amplifier 15 is applied to the disk drive motor. 16 to drive the disk drive motor 16. The output voltage of the motor drive amplifier 15 is also applied to a starting period length determining circuit 17, which determines whether or not the starting period is longer than a predetermined period based on the application period of the kick voltage applied to the motor driving amplifier 15. When the activation period is longer than a predetermined period, control is performed to increase the gain of the servo amplifier 15. Here, the switching of the gain of the servo amplifier 14 is controlled by a changeover switch 14 ₁ which switches the feedback resistance of the servo amplifier 14 using the output of the activation period length determination circuit 17 . Note that 18 is a reference clock signal oscillator.

For example, as shown in FIG. 2(b), the startup period length determination circuit 17 includes a resistor 17 ₁ connected to a power supply, a capacitor 17 2 connected in series to the resistor 17 ₁ , and a capacitor 17 ₂ connected to both ends of the capacitor 17 ₂ . The capacitor 172 is controlled by a voltage that reaches a power failure potential when the disk drive motor is started, so that the electric charge in the capacitor ₁₇₂ is discharged while the disk drive motor is stopped, and the capacitor ₁₇₂ can be charged while the disk drive motor is started and rotating. A transistor ₁₇₃ , a buffer amplifier ₁₇₄ which receives the voltage of the capacitor ₁₇₂ as an input, and a D flip-flop 175 which takes the kick voltage described later as a data input and the output of the buffer amplifier ₁₇₄ as _{a clock} input. It is configured such that the changeover switch 14 ₁ is driven by the Q output of the D flip-flop 17 ₅ .

[0008] In the disk motor servo circuit of this embodiment configured as described above, the disk The synchronization signal in the EMF signal detected from the synchronization signal detection circuit 11 , the period of the detected synchronization signal and the reference clock output from the reference clock signal oscillator 18. A comparator 12 compares the period of the clock signal with the period of the clock signal. This comparison determines the detected synchronization signal. When the period and the period of the reference clock signal match, the output terminal of the comparator 12 is It becomes high impedance. If the rotation speed of the disk drive motor 16 decreases, , the period of the detected synchronization signal becomes longer, the output of the comparator 12 becomes 〃L〉, and conversely, the rotation If the number is large, the output will be 〃H〃.

[0009] Therefore, when the disk drive motor 16 is started, the period of the detection synchronization signal is long. Therefore, the output of the comparator 12 becomes "L", and the output of the motor drive amplifier 15 becomes as shown in FIG. As shown in a), the kick voltage is output, and the disk drive motor 16 responds to the kick voltage. Therefore, when the disk drive motor 16 is started and the rotational speed of the disk drive motor 16 increases, a detection synchronization signal is generated. The period of the number becomes shorter, and when the disk drive motor 16 reaches a predetermined rotation speed, The output terminal of comparator 12 becomes high impedance and then overshoots. When the rotation speed of the disk drive motor 16 increases, the output of the phase comparator 12 becomes 〃H〃 As a result, the output of the motor drive amplifier 15 becomes negative polarity as shown in Fig. 2. The brake is applied to the disk drive motor 16, and the disk drive motor 16 rotates at a predetermined speed. It is controlled to be driven by.

0010 However, the output of the motor drive amplifier 16 is supplied to the starting period length determination circuit 17. It is determined whether the startup period is longer than a predetermined period or not based on the application period of the kick voltage. It is. That is, at the same time as the disk drive motor 16 is started, the transistor 17 ₃ is controlled to the off state, and the capacitor 17₂is resistance 17₁Figure 2 (c-1) through The battery is charged to the power supply voltage. capacitor 17₂A buffer that amplifies the voltage of Amplifier 17_FourAs shown in Figure 2 (c-2), the output of It becomes the rank. On the other hand, the kick voltage is as shown in Figure 2 (c-3), and the buffer amplification Vessel 17_FourThe output of is latched at the rising edge as shown in FIG. 2(c-4). Here, key The period during which the buffer amplifier 17 is applied is short;_FourThe output of rises When the voltage rises after the application of the kick voltage ends, the Q output is at a low potential, During the period when the kick voltage is applied, the buffer amplifier 17_FourThe output of In this case, the Q output becomes a high potential, and the start-up period length increases from the time of start-up to the buffer amplifier 17._Four Is the period during which the kick voltage is applied longer than the period until the output rises? , and is determined by how short it is.

However, if the disc installed in the CD player is a 12 cm disc, the period during which the kick voltage is applied is longer than in the case of an 8 cm disc due to its large inertia. The circuit 17 determines that the activation period is longer than a predetermined period, and the output of the activation period length determination circuit 17 causes the selector switch 14 ₁ to be switched to a position where the gain of the servo amplifier 14 is increased.

[0012] Furthermore, when the disc installed in the CD player is an 8 cm disc, the period during which the kick voltage is applied is shorter than when the disc is 12 cm because the inertia is small, and it is difficult to determine the startup period length. The circuit 17 determines that the activation period is less than a predetermined period, and the output of the activation period length determination circuit 17 causes the selector switch 14 ₁ to be switched to a position where the gain of the servo amplifier 14 is lowered. Therefore, the gain of the disk motor servo circuit is switched depending on the diameter of the mounted disk, and stable servo operation is performed.

[0013] In addition, in the above embodiment, the difference depends on the period during which the kick voltage is applied. In this example, the start-up period length is determined using the kick voltage application period. , a period during which the output of the comparator 12 is at "H" may be detected at startup. Also , exemplifies the case where the startup period length determination circuit 17 is configured with discrete components. However, the activation period length can also be determined by a microcomputer.

[0014]

[Effect of the idea]

As explained above, according to the present invention, it is determined whether the startup period is longer than a predetermined period or not. A start-up period length determining means is provided, and a gain switching circuit is activated according to the output of the start-up period length determining means. The inertia differs depending on the diameter of the installed disc. However, the size of the disk is essentially determined based on the length of the startup period, and the disk is installed. The gain of the disc motor servo circuit will be changed depending on the disc diameter. As a result, stable servo operation is performed. In addition, the activation period length determination means is not optical detection. It is also easy to configure and can be done at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2(a) is a waveform diagram showing the drive voltage of the disk drive motor at startup to explain the operation of an embodiment of the present invention. (b) is a block diagram showing the configuration of a startup time length determination circuit. (c-1) to (c-4) are waveform diagrams for explaining the operation of the activation time length determination circuit.

FIG. 3 is a block diagram showing the configuration of a conventional example.

[Explanation of symbols]

11 Synchronous signal detection circuit 12 Comparator 13 Low-pass filter 14 Servo amplifier 14 ₁ selector switch 15 Motor drive amplifier 16 Disk drive motor 17 Starting period length determination circuit 18 Reference clock signal oscillator

Claims (1)

[Scope of utility model registration request] Claim 1: A disc motor servo circuit for a CD player equipped with a gain switching circuit for switching the gain of the servo circuit, comprising a startup period length determining means for determining whether the startup period is longer than a predetermined period. 1. A disk motor servo circuit for a CD player, characterized in that a gain switching circuit is switched in accordance with the output of a starting period length determining means.