JP2840784B2 - Drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used when an actuator is driven using discrete servo signals, such as a servo circuit of a sample servo type optical disk recording / reproducing apparatus. And a suitable drive circuit.

[Summary of the Invention]

The present invention forms a PWM signal having a pulse width corresponding to an input discrete servo signal in a drive circuit suitable for driving an actuator using the discrete servo signal. When the width is shorter than the sampling period divided by n, the PWM signal having the pulse width corresponding to the input discrete servo signal is output as it is, and when the pulse width of the PWM signal is longer than the sampling period divided by n, the signal is divided by n. Sampling period
A pulse having a pulse width multiplied by an integer up to a value that does not exceed the pulse width of the PWM signal is previously output, and a pulse having the remaining pulse width is output according to the input discrete servo signal. The delay of the drive system with respect to the servo signal due to the hold can be reduced.

[Conventional technology]

One of the optical disk servo systems is a sample servo system. In the sample servo method, servo control is performed using servo signals from servo areas arranged at predetermined intervals. Therefore, a continuous servo signal cannot be obtained, and the servo signal becomes discrete.

Conventionally, in the case of such a discrete servo signal, the previous servo data is held flat (zero-order hold),
The actuator is driven.

[Problems to be solved by the invention]

However, in the case of the zero-order hold, the drive system is delayed by (1/2) of the sampling period T _S with respect to the change of the servo signal. Therefore, there is a problem that the servo system is not stable.

That is, it is assumed that the servo signal is changing as shown by A1 in FIG. 9A. This servo signal is at time T ₅₁ ,
T _52, T _53, ... in the is sampled and held, the discrete servo signals _{D 51, D 52, D 53} , ... are obtained.

When these discrete servo signals D ₅₁ , D ₅₂ , D ₅₃ ,... Are held in the 0th order, a step-like waveform as shown by B1 in FIG. 9B is obtained. When the actuator is driven by the zero-order hold waveform B1, the actuator is driven at a timing corresponding to the center of the previous sample value up to the next sample point, so that the characteristic shown by the broken line C1 in FIG. 9B is obtained. Drives the actuator. Thus, the discrete surveillance signals D ₅₁ , D ₅₂ , D ₅₃ ,
.. Are driven in the 0th order and the actuator is driven with a delay of (（) of the sampling period T _S.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a drive circuit capable of reducing a delay caused when a waveform actuator in which a discrete servo signal is zero-order-held is driven and stabilizing a servo system.

[Means for solving the problem]

The present invention relates to a drive circuit for driving an actuator with a discrete servo signal, wherein a pulse width PW corresponding to the input discrete servo signal is used.
When the M signal is formed and the pulse width of the PWM signal is shorter than the sampling period divided by n, the PWM signal having the pulse width corresponding to the input discrete servo signal is output as it is, and the pulse width of the PWM signal is divided by n If the sampling period is longer than the sampling period, the sampling period divided into n
A pulse having a pulse width multiplied by an integer up to a value that does not exceed the pulse width of a signal is previously output, and pulses having the remaining pulse width are output according to the input discrete servo signal. It is a tribe circuit of a dynamic servo signal.

[Action]

If the pulse width of this discrete servo signal after PWM conversion is less than (1/2) of the sampling period, for example, the PWM of the pulse width corresponding to the input discrete servo signal
The signal is output as is, and this discrete servo signal is
The pulse width at the time of M conversion is, for example, (1
/ 2) when made above is, (1/2) · T pulse _S content of the pulse width is first-out before discrete servo signal current is input, discrete pulse of the remaining pulse width is inputted this time Is output in response to a dynamic servo signal. For this reason, the center of the drive pulse substantially coincides with the input timing of the discrete servo signal, and the delay of the drive system due to a change in the servo signal is improved.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

 First, the principle of an embodiment of the present invention will be described.

When driving an actuator with discrete servo signals,
When the discrete servo signal is converted to a PWM signal and the actuator is driven, when the input discrete servo signal is small and the pulse width of the converted PWM signal is short, the delay of the drive system due to the change in the servo signal is reduced. Can be improved.

That is, now, as shown in FIG. 2 A, at every sampling period T _s, the continuous servo signals _{D 1, D 2, D 3} , ... are obtained. When the values of the discrete servo signals D ₁ , D ₂ , D ₃ ,... Are converted into pulse widths to form PWM signals, the result is as shown in FIG. 2B. The pulse width p of the PWM signals P ₁ , P ₂ , P ₃ , ...
_k is the value of d _k of discrete servo signals D _k inputted, when the maximum value of the servo signal and d _max, since the maximum pulse width T _s at the maximum value d _max, p _k = T _s · (D _k / d _max ).

Thus, the discrete servo signals D ₁ , D ₂ , D ₃ ,.
When the actuators are driven by converting them into signals P ₁ , P ₂ , P ₃ ,..., Each servo signal drives the actuators at a timing substantially at the center of the pulse. Is τ _{1 in} FIG. When the input discrete servo signals D ₁ , D ₂ , D ₃ ,... Are small and the pulse width of the converted PWM signal is short, the delay τ ₁ becomes small as shown in FIG. It is possible to improve the delay of the driving system due to the change of the signal.

However, as shown in FIG. 3A, when the input discrete servo signals D ₁₁ , D ₁₂ , D ₁₃ ,.
As shown in FIG. B, the converted PWM signals P ₁₁ , P ₁₂ , P ₁₃ ,.
Becomes longer. In this case, the delay τ ₂ of the drive system with respect to the servo signal becomes large, and the delay of the drive system with respect to the change of the servo signal cannot be sufficiently improved.

Accordingly, in one embodiment of the invention, discrete servo signals D _k when PWM converts, when the pulse width p _k is equal to or less than (1/2) of the sampling period T _S the PWM signal input
As it is output P _k, that when the pulse width p _k becomes (1/2) or more of the sampling period T _S is, (1/2) · T _S content of discrete servo signals D pulses of this pulse width _k leave first-out before is input, the pulse p _k of the remaining pulse width - so that is output in response to (1/2) · T discrete servo _{signals S} a inputted this time.

Whether the pulse width p _k when the discrete servo signals D _k and PWM conversion time is (1/2) or more of the sampling period T _S, since the servo signal is correlated, the last discrete servo It can be detected from the pulse width _pk-1 when the signal _Dk-1 is subjected to PWM conversion.

Thus, when the pulse width p _k when the current discrete servo signals D _k to PWM conversion is (1/2) or more of the sampling period T _S is, (1/2) · T _S a pulse width corresponding Of the pulse before the current discrete servo signal _Dk is input, and output pulses of the remaining pulse width according to the discrete servo signal input this time, Even when the servo signal is large and the pulse width of the converted PWM signal is long, the delay of the drive system due to the change in the servo signal can be improved.

That is, as shown in FIG. 4A, it is assumed that discrete servo signals D ₂₁ , D ₂₂ , D ₂₃ ,... Having a large amplitude are input. The discrete servo signals _{D 21, D 22, D 23} , PWM signal P a ..., as shown in FIG. 4 _{B '21, P' 22,} P '23, when converted to ..., the pulse width p _21, p _22, p _23, ... is greater than (1/2) of sampling frequency T _s.

In this case, as shown in FIG. 4C, (1/2) · T _S
A pulse having a pulse width of 1 minute is output first, and as shown in FIG. 4D, after the current discrete servo signals D ₂₁ , D ₂₂ , D ₂₃ ,. You.
As a result, the PWM signals P ₂₁ , P ₂₂ , P as shown in FIG.
₂₃ , ... are formed. In this case, the delay of the drive signal with respect to the servo signal becomes τ ₃ , and the delay of the drive system with respect to the change of the servo signal can be improved.

FIG. 1 shows an embodiment of the present invention. In this embodiment, as described above, the pulse width when the discrete servo signal of this time is subjected to PWM conversion is set to the sampling period T _S (1
/ 2) When it becomes below, the PWM signal is output as it is,
If the pulse width of this discrete servo signal after PWM conversion is more than (1/2) of the sampling period, (1/2)
・ Pulse with a pulse width of T _S is advanced before the current discrete servo signal is input, and pulses with the remaining pulse width are output according to the discrete servo signal input this time. In this case, the delay of the drive signal with respect to the change of the servo signal is improved.

In FIG. 1, an input terminal 1 is supplied with a discrete servo signal held in the zero order. While this discrete servo signal is supplied to the non-inverting input terminal of the comparator 2A,
It is supplied to the non-inverting input terminal of the comparator 2B.

Triangular wave f ₁ synchronized with the sampling clock CK is supplied to an input terminal 3A. Triangular wave f ₁ from the input terminal 3A is supplied to the inverting input terminal of the comparator 2A. To an input terminal 3B, advanced triangular wave f ₁ from 180 degree phase from the input terminal 3A triangular wave f
₂ is supplied. Triangular wave f ₂ from the input terminal 3B is supplied to the inverting input terminal of the comparator 2B.

A sampling clock CK is supplied to the input terminal 4.
This sampling clock CK is supplied to D
It is supplied to the clock input terminal of the flip-flop 6.

The comparator 2A compares the level of the 0-order held discrete servo signal from the input terminal _{1 with} the level of the triangular wave f1 from the input terminal 3A. When the level of the discrete servo signal inputted is higher than the triangular wave f _1, the output of the comparator 2A goes high. When the level of the discrete servo signal level of the triangular wave f ₁ is input becomes higher,
The output of the comparator 2A becomes low level. From the output of the comparator 2A, a PWM signal corresponding to the zero-order held discrete servo signal from the input terminal 1 is obtained.

That is, as shown in FIG.
In CK time t ₃₁ to (FIG. 5 D) rises, as shown in FIG. 5 A, and the discrete servo signals D ₃₁ from the input terminal 1 is input. Level d ₃₁ of the discrete servo signals D ₃₁
Is the time point t ₃₂ at which the sampling clock CK rises next.
Until held. This and level d ₃₁ of discrete servo signals D ₃₁ and the signal level of the triangular wave f ₁ are compared by the comparator _2A.

As shown in FIG. 5 B, the signal level of the triangular wave f ₁ is the time
gradually rises from t _31. To time t _A1, since the level d ₃₁ of discrete servo signals D ₃₁ is greater than the signal level of the triangular wave f _1, as shown in FIG. 5 B, the output of the comparator 2A goes high. Triangular wave f ₁ is gradually increased, past the point t _A1, the signal level of the triangular wave f ₁ is greater than the level d ₃₁ of discrete servo signals D _31. Therefore, the output of the comparator 2A becomes low level. The output of the comparator 2A (Fig. 5 C), the PWM signal P ₃₁ corresponding to the discrete servo signals D ₃₁ inputted obtained.

In FIG. 1, the output of the comparator 2A is supplied to the a-side input terminal of the switch circuit 7 and to the data input terminal of the D flip-flop 6. The output of the comparator 2A is captured by the D flip-flop 6 at the falling edge of the sampling clock CK. The output of the D flip-flop 6, the last discrete servo signals D PWM signal corresponding to the _k-1 P _k-1 the pulse width p _k-1 is the sampling period T
_It is detected whether it is (1/2) or more of _s .

That is, in FIG. 5, the sampling clock CK
Assuming that the duty ratio of FIG. 5D is 50%, PW
If the pulse width of the M signal (Fig. 5 C) of the sampling period T _s (1/2) or more, even after the sampling clock CK falls time t _B, output from the comparator 2A
The PWM signal (FIG. 5C) is at a high level. If the pulse width of the PWM signal of the sampling clock T _s (1/2) or less,
Before past the falling time t _B of the sampling clock T _s, PWM signal output from the comparator 2A (Fig. 5 C) becomes a low level.

Therefore, if the output is low level of the D flip-flop 6, the pulse width p _k-1 of the PWM signal P _k-1 corresponding to the previous discrete servo signals D _k-1 is the sampling period T _s (1/2)
It can be determined that: If the output is high level of the D flip-flop 6, the last discrete servo signals D PWM signal corresponding to the _k-1 P _k-1 the pulse width p _k-1 is the sampling period T _s
It can be judged that it is (1/2) or more.

Comparator 2B, the level of the zero-order-held discrete servo signal from the input terminal 1, and the level of the triangular wave f ₂ from the input terminal 3B are compared. Triangular wave f _2, as described above, the triangular wave f ₁ from 180 degree phase from the input terminal 3A is progressing. When the level of the discrete servo signal inputted is higher than the triangular wave f _2, the output of the comparator 2B becomes high level. When the level of the triangular wave f ₂ is higher than the level of the discrete servo signals input, the output of the comparator 2B becomes low level. From the output of this comparator 2B,
(1/2) PWM signal first-out pulses only T _s can be obtained.

That is, as shown in FIG.
In CK (FIG. 6 D) time t ₄₁ which rises, as shown in FIG. 6 A, and the discrete servo signals D ₄₁ from the input terminal 1 is input. The signal level of the time point t ₄₁ (1/2) T _s by the triangular wave f ₂ in the previous time t ₄₀ is minimized, then gradually increases.

As shown in FIG. 6 A, from the time t ₄₁ to the sampling clock CK rises (1/2) in T _s just before the time point t _40,
Value d ₄₀ is provided which holds the previous discrete servo signals to the input terminal 1. Then, the signal level of the triangular wave f ₂ is minimum becomes at time t _40, gradually increases from this point t _40. Thus, between the time t ₄₀ the time t _41, as shown in FIG. 6 B, the signal level d ₄₀ from the input terminal 1
There greater than the signal level of the triangular wave f _2, as shown in FIG. 6 C, between the time t ₄₀ to time t _41, the comparator
2B output goes high. Thus, pulses of (1/2) T _s a pulse width corresponding to one of the PWM signal corresponding to the discrete servo signals D ₄₁ will be already outputted. However,
The pulse width of the current discrete servo signals and the PWM signal corresponding to the previous discrete servo signal is (1/2) shall become more T _s.

Once t _41, the current to the input terminal 1 discrete servo signals D ₄₁
The value d ₄₁ which holds the given. At this time, the triangular wave f ₂
Has risen to the level of (1/2) of the maximum value.

Once t _A2 the signal level of the triangular wave f ₂ is greater than the level d ₄₁ of discrete servo signals D _31, as shown in FIG. 6 C, the output of the comparator 2B becomes low level. From the output of this comparator 2B, the input discrete servo signal
Corresponding to D ₄₁ (1/2) T _s by the PWM signal P ₄₁ which the pulse was tipped is obtained.

In FIG. 1, the output of the comparator 2A is supplied to the a-side input terminal of the switch circuit 7, and the output of the comparator 2B is supplied to the b-side input terminal of the switch circuit 7. The output of the D flip-flop 6 is supplied to the switch circuit 7 as a switch control signal.

When the pulse width p _k-1 of the PWM signal corresponding to the previous discrete servo signals of the sampling period T _s below (1/2) is,
The output of the D flip-flop 6 goes low. When the output of the D flip-flop 6 is at the low level, the switch circuit 7 is switched to the side a, and the PWM signal corresponding to the input discrete servo signal is output from the switch circuit 7 as it is.

The pulse width p _k-1 of the PWM signal corresponding to the previous discrete servo signal is at the (1/2) or more of the sampling clock T _s is the output of the D flip-flop 6 becomes high level.
When the output of the D flip-flop 6 is high, the switch circuit 7 is switched to side b, (1/2) PWM signal first-out pulses only T _s is output from the switch circuit 7.

The PWM signal output from the switch circuit 7 is supplied to the PWM drive circuit 8. The output of the PWM drive circuit 8 is taken out from the output terminal 9. The output of the output terminal 9 is supplied to an actuator (not shown).

FIG. 7 shows the waveform of each part for the discrete input signal held in the zero order.

As shown in FIG. 7A, in synchronization with the sampling clock CK shown in FIG.
Supplied to

The input discrete servo signal (FIG. 7A) and the triangular wave f ₁ (FIG. 7B) are compared by the comparator 2A, and an output as shown in FIG. 7C is obtained from the comparator 2A. . From the output of the comparator 2A, a PWM signal corresponding to the discrete servo signal held in the 0th order is obtained.

The input discrete servo signal (FIG. 7A) is compared with the triangular wave f ₂ (FIG. 7D) by the comparator 2B, and an output as shown in FIG. 7E is obtained from the comparator 2B. From the output of this comparator 2B, the pulse width is (1 /
2) when equal to or greater than T _s is, PWM signal is obtained which is first-out pulse only (1/2) T _s.

FIG. 7G shows the output of the D flip-flop 6. The D flip-flop 6, whether the pulse width is (1/2) equal to or greater than T _s is detected. The switch circuit 7 is switched by the output of the D flip-flop 6. D
If the output of the flip-flop 6 is at a low level, the switch circuit 7 is switched to the side a, and the output of the comparator 2A (FIG. 7C) is output from the switch circuit 6. If the output of the D flip-flop 6 is at a high level, the switch circuit 7 is switched to the b side, and the output of the comparator 2B (FIG. 7E)
Are output from the switch circuit 6.

As a result, a PWM signal as shown in FIG.

As shown in FIG. 7 H, the PWM signal, when the pulse width is longer than (1/2) T _s, a pulse of (1/2) T _s before this discrete servo signals are input Since the pulse having the width is output first, the substantially center of the output pulse substantially coincides with the input timing of the discrete servo signal, and the drive system hardly delays due to the change in the servo signal.

In one embodiment described above, divided into two ways of the following or the pulse width of the current discrete servo signals (1/2) T _s or more,
If the pulse width is less than (1/2) T _s , the PWM remains unchanged
Outputs a signal, when the pulse width is more than (1/2) T _s is so that to first-out pulses of (1/2) T _s worth of pulse width, the present invention, the pulse width Divided into multiple ways,
In response to this, a plurality of advance pulse widths may be set.

For example, the pulse width p _k of discrete servo signals corresponds to which the length of the following four are not. This determination is made using the pulse width _pk-1 of the previous discrete servo signal.

_{p k <(1/4) T s} (1/4) T s ≦ p k <(1/2) T s (1/2) T s ≦ p k <(3/4) T s (3/4 ) T _s ≦ p _k Then, if the pulse width p _k is _{(p k <(1/4) T} s), as shown in FIG. 8 a, is outputted as the PWM signal.

If the pulse width _pk is (1/4) T _s ≤p _k <(1/2) T _s , a pulse having a pulse width of (1/4) T _s is advanced as shown in FIG. Pulses of the remaining pulse width are output after the current discrete servo signal is input.

If the pulse width p _k is _{(1/2) T s ≦ p k} <(3/4) T s, as shown in FIG. 8 C, and the pulse of the pulse width of (1/2) T _s first-out, the remaining Are output after the current discrete servo signal is input.

If the pulse width p _k is (3/4) T _s ≦ p _k, as shown in FIG. 8 D, (3/4) pulse having a pulse width of T _s is first-out, the pulse of the remaining pulse width time Are input and then output.

Generally, the algorithm is as follows. Or the pulse width p _k of discrete servo signal corresponds to any length of street below n is determined.

If the pulse width _pk is (0 ≦ _pk <(1 / n) T _s ), the PWM signal is output as it is.

The pulse width p _k, as described above, when the value of the discrete servo signal inputted to d _k, the maximum value d _max of the servo signal, and _{p k = T s · (d} k / d max) .

If the pulse width p _k is _{(1 / n) T s ≦} p k <(2 / n) T s, are first-out a pulse having a pulse width of _{(1 / n) · T s} . The remaining pulse width p _k − (1 / n) T _s = T _s · ((d _k / d _max ) − (1 / n)) is output after the current discrete servo signal is input. Is done.

If the pulse width p _k is _{(2 / n) T s ≦} p k <(3 / n) T s, (2 / n) of the pulse width of · T _s pulse is first-out. The remaining pulse width p _k − (2 / n) T _s = T _s · ((d _k / d _max ) − (2 / n)) is output after the current discrete servo signal is input. Is done.

(If _{N / n) T s, (} (N-1) pulse width p _k is (N-1) / n) T s ≦ p k </ n) of the pulse width of · T _s pulse is first-out. The remaining pulse width _{p k - ((N-1} ) / n) · T s = T s · ((d k / d max) - (N-1) / n)) is the current discrete servo signals Is input and then output.

〔The invention's effect〕

According to the present invention, the pulse width when the current discrete servo signal is subjected to PWM conversion is, for example, (1/1 /
2) When it becomes less than the above, the PWM signal of the pulse width corresponding to the input discrete servo signal is output as it is, and the pulse width when this discrete servo signal is subjected to PWM conversion is, for example, (1/2) of the sampling period. When it becomes more than (1/2)
A pulse having a pulse width of T _S is advanced before the current discrete servo signal is input, and a pulse having the remaining pulse width is output according to the discrete servo signal input this time.
For this reason, the center of the drive pulse substantially coincides with the input timing of the discrete servo signal, and the delay of the drive system due to a change in the servo signal is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIGS. 2 and 3 are timing diagrams used for explaining a PWM signal, FIG. 4 is a timing diagram used for explaining the principle of one embodiment of the present invention, and FIG. 5 and 6 are timing charts used for explaining one embodiment of the present invention, FIG. 7 is a waveform diagram of each part used for explaining one embodiment of the present invention, and FIG. 8 is a diagram showing another embodiment of the present invention. FIG. 9 is a timing chart used for explanation, and FIG. 9 is a waveform chart used for explaining a conventional drive circuit. Explanation of main symbols in the drawings 2A, 2B: Comparator, 6: D flip-flop, 7: switch circuit, 8: PWM drive circuit.

Claims (1)

(57) [Claims] In a drive circuit for driving an actuator by a discrete servo signal, a PWM having a pulse width corresponding to the input discrete servo signal is provided.
When the pulse width of the PWM signal is shorter than the sampling period divided by n, the PWM signal having the pulse width corresponding to the input discrete servo signal is output as it is, and the pulse width of the PWM signal is n. When the sampling period is longer than the divided sampling period, a pulse having a pulse width obtained by multiplying the sampling period obtained by dividing the n by an integer up to a value not exceeding the pulse width of the PWM signal is supplied in advance, and the pulses having the remaining pulse widths are input to the above. A drive circuit for outputting in response to a discrete servo signal.