JPH0739309Y2 - Motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a motor drive circuit, and more particularly to a motor drive circuit suitable for a spindle motor drive circuit of an LD player or a CD player.

[Conventional technology]

For example, a spindle motor drive circuit that drives a spindle motor of an LD player uses the F / R signal (front / rear switching signal) and ACCEL signal (accelerator signal) input from an external spindle controller (see Fig. 1) to drive the motor. Switching drive.

For example, if the F side is at "H" level and the R side is at "L" level, the F / R signal is at "H" level during the start-up of the spindle motor and during normal rotation to drive in the forward rotation direction. Is stopped, it is driven in the deceleration direction and is set to the “L” level.

On the other hand, for the ACCEL signal, for example, the on side (rotation side) is "L".
If the level and the off side (stop side) are set to “H” level, the spindle motor is set to “L” level when starting and stopping.

During steady rotation, according to the error signal obtained by comparing the frequency phase of the H sync in the playback video signal with the reference oscillation signal, ACCEL
The signal alternates between "H" and "L" levels.

A concrete circuit diagram of a conventional spindle motor drive circuit is shown in FIG.

The transistors Tr1 to Tr5 are power transistors having a large current capacity, and the transistors Tr6 to Tr11 are switching control transistors.

The transistor Tr12 is connected to the transistor Tr5 in Darlington.

Transistors Tr8 and Tr9 when F / R signal is at "H" level
Is turned on, the transistor Tr7 is turned off in response to this, and the transistor Tr10 is turned off.

Also, the transistor Tr6 is turned on.

Transistor Tr11 while ACCEL signal is "L"
Turns on, and in response to this, the transistors Tr12 and Tr5 also turn on.

Therefore, transistors Tr1 and Tr4 are turned off,
Since Tr2 and Tr3 are turned on, a drive current in the forward rotation direction flows through the spindle motor 10 and the spindle motor 10 is accelerated in the forward rotation direction.

Transistor Tr11 while ACCEL signal is "H"
Turns off, and in response to this, the transistors Tr12 and Tr5 also turn off.

For this reason, all of the transistors Tr1 to Tr4 are turned off, almost no drive current flows through the spindle motor 10, and braking is applied to decelerate.

During steady rotation, the ACCEL signal is repeatedly turned on and off periodically, and the spindle motor 10 rotates at a speed according to the duty ratio of the ACCEL signal.

The choke coil L and the capacitor C1 form an integrating circuit, and prevent the drive current flowing through the spindle motor 10 from abruptly changing and vibrating due to the on / off state of the transistor Tr5.

The diode D1 is for absorbing the counter electromotive force of the choke coil L when the transistor Tr5 changes from on to off.

The capacitors C2 and C3 are for speeding up, and improve the response of the on / off change of the transistors Tr11, Tr12, Tr5 to the high speed change of the ACCEL signal, and ensure the control response of the spindle motor 10. .

The resistor R is a small resistor for detecting the drive current, and the resistor R
After the detection voltage across both ends of the is amplified by the first operational amplifier 60, the second operational amplifier 62 outputs the reference voltage E _ref (+ V _{cc divided} by resistors R20 and 21 corresponding to the reference drive current I ₀ ).
Compared to.

In the second operational amplifier 62, the drive current I flowing through the spindle motor 10 (actually the current flowing through the resistor R) is smaller than I ₀ , and the detection voltage output from the first operational amplifier 60 falls below the reference voltage E _ref. If it is, “L” level (≒
-V _-) and outputs a reverse drive current I exceeds the I _0, the detection voltage exceeds the reference voltage E _ref "H" level (≒ + V _-) and outputs an overcurrent detection signal.

The resistor R, the first operational amplifier 60, the second operational amplifier 62, the resistors 20, 21 and the like constitute the overcurrent detecting means 70.

When the overcurrent detection signal is "L", the transistor Tr11
Turns on and off according to the ACCEL signal.

Conversely, when the overcurrent detection signal becomes "H", the transistor
The base voltage of Tr11 is clamped to about + _Vcc by the diode D2 and turned off, the transistors Tr12 and Tr5 are also turned off, and the drive current hardly flows to the spindle motor 10.

As a result, the ACCEL
It is possible to suppress a large starting current generated when the signal is continuously set to the “L” level for a certain period of time.

[Problems to be solved by the device]

However, in such a conventional technique, a response in which the transistor Tr11 is turned on / off in response to a fast change of the ACCEL signal is caused by the capacitance component of the clamping diode D2 provided between the base of the transistor Tr11 and + _Vcc. However, there is a problem that the reliability is deteriorated and it becomes difficult to perform reliable switching control for the spindle motor 10.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a motor drive circuit capable of improving switching responsiveness to a rapid change in an accelerator signal.

[Means for Solving the Problems]

A motor drive circuit of the present invention includes a control transistor for switching a power transistor in accordance with an accelerator signal input from the outside, and an overcurrent detection means for outputting an overcurrent detection signal when the drive current becomes an overcurrent. The circuit is characterized in that a transistor that is turned on / off according to an overcurrent detection signal is connected in series between the control transistor and the power supply, and a clamping diode is interposed between the base of the transistor and the power supply.

〔Example〕

Next, one embodiment of this invention will be described with reference to FIG.

FIG. 1 is a circuit diagram of a spindle motor system of an LD player according to the present invention.

The spindle motor drive circuit 20 is an F / R input from a spindle controller 30 including a microcomputer.
Switching drive of spindle motor 10 (DC brushless motor) is performed according to the signal and ACCEL signal.

The spindle motor drive circuit 20 has an F / R terminal for inputting an F / R signal, an ACCEL terminal for inputting an ACCEL signal, and + V ₊
+ Power supply terminal E ₊ connected to the power supply, and −V ₋ connected to −V −
It has a power supply terminal E _- and a + power supply terminal V ₊ connected to + _Vcc .

After the PNP transistor Tr1 and NPN transistor Tr2 connected in series and the PNP transistor Tr3 and NPN transistor Tr4 connected in series are connected in parallel, one end side is +
It is connected to the power supply terminal E ₊ , and the other end is connected through the resistor R for current detection, the choke coil L, and the transistor Tr5 of NPN.
Power terminal E _- to be connected.

The connection point P1 between the transistors Tr1 and Tr2 and the transistor
The spindle motor 10 is connected between the connection point P2 between Tr3 and Tr4.

The transistors Tr1 to Tr5 are power transistors.

A transistor Tr12 is Darlington-connected to the transistor Tr5.

The base of the transistor Tr2 is connected to the collector of the transistor Tr6 of the PNP via the resistor R1, and the emitter of this transistor Tr6 is connected to the + power supply terminal E ₊ .

The base of the transistor Tr1 is connected to the collector of the transistor Tr7 of the NPN via the resistor R2, and the emitter of this transistor Tr7 is connected to the ground.

The base of the transistor Tr7 is connected to the collector of the transistor Tr8 of the NPN via the resistor R3, and the emitter of this transistor Tr8 is connected to the ground.

The collector of the transistor Tr8 is + via the resistor R4.
It is connected to the power supply terminal E ₊ , and the base is connected via the resistor R5.
It is connected to the F / R terminal.

The base of the transistor Tr3 is connected to the collector of the transistor Tr9 of the NPN via the resistor R6, and the emitter of this transistor Tr9 is connected to the ground.

The base of the transistor Tr9 is connected to the F / R terminal via the resistor R7, and the collector is connected to the base of the transistor Tr6 via the resistor R10.

The base of the transistor Tr4 is connected to the collector of the transistor Tr10 of the PNP via the resistor R8, and the emitter of this transistor Tr10 is connected to the + power supply terminal E ₊ .

The base of the transistor Tr10 is connected to the collector of the transistor Tr7 via the resistor R9.

Emitter side of transistor Tr2 of resistance R and + power supply terminal ₊
A capacitor C1 is connected between the two.

A diode D1 is connected between the collector side of the transistor Tr5 of the choke coil L and the + power supply terminal E ₊ .

The choke coil L and the capacitor C1 form an integrating circuit,
The step-like change in the applied voltage of the spindle motor 10 accompanying the on / off of the transistor Tr5 is suppressed to a smooth change.

The diode D1 is for absorbing the counter electromotive force generated in the choke coil L when the transistor Tr5 changes from on to off.

The base of the transistor Tr12 is connected to the collector of the transistor Tr11 of the PNP via the resistor R11, and the collector of the transistor Tr11 is also connected to the −power supply terminal E ₋ via the resistor R12.

The transistor Tr11 is a control transistor for switching-controlling the transistors Tr12 and Tr5 according to the ACCEL signal.

The emitter of the transistor Tr11 is connected to the ground via the resistor R13, and is also connected to the collector of the transistor Tr13 of the PNP, and the emitter of this transistor Tr13 is connected to the + power supply terminal V ₊ .

The base of transistor Tr11 is ACCEL via resistors R14 and R15.
It is connected to the terminal.

Resistors R15 and R11 are connected in parallel with speed-up capacitors C2 and C3, respectively, so that the transistors Tr11, Tr12, and Tr15 can be turned on and off with good response to rapid changes in the ACCEL signal. It has become.

On the other hand, both ends of the resistor R are connected to the + side input terminal and the − side input terminal of the first operational amplifier 60 via the resistors R16 and R17, respectively.

There is a resistor between the + side input terminal of the first operational amplifier 60 and ground.
R18 is connected, and a resistor R19 is connected between the output side of the first operational amplifier 60 and the-side input terminal.

The first operational amplifier 60 configured as described above amplifies the detection voltage generated across the resistor R.

The output side of the first operational amplifier 60 is connected to the + side input terminal of the second operational amplifier 62.

Also, resistors R20 and 21 are connected in series between the + power supply terminal V ₊ and ground, and the reference voltage E _ref obtained by dividing + V _cc with the resistors R20 and R21 is the − side input of the second operational amplifier 62. It is input to the terminal.

This reference voltage E _ref corresponds to the reference drive current I ₀ .

With the second operational amplifier 62 configured in this way, the first operational amplifier 62
The output voltage of the operational amplifier 60 and the reference voltage E _ref are compared, and when the output of the first operational amplifier 60 is lower than the reference voltage E _ref , the “L” level (≈−V ₋ ) is output, When the output of the operational amplifier 60 exceeds the reference voltage E _ref , an “H” level (≈ + V ₊ ) overcurrent detection signal is output.

The resistor R, the first operational amplifier 60, the second operational amplifier 62, and the resistors R16 to R21 form an overcurrent detecting means 70.

In addition, the first operational amplifier 60 and the second operational amplifier 62 are +
V ₊ and −V ₋ are supplied as operating power.

The output side of the overcurrent detecting means 70 is connected to the base of the transistor Tr13 via the resistor R22.

Further, a clamp diode D2 is connected between the base of the transistor Tr13 and the + power supply terminal V ₊ .

When the output of the overcurrent detection means 70 is "L", the transistor
The base voltage of Tr13 is almost -V _- Since the fall near the transistor Tr13 is turned on, the transistor Tr11 can be turned on and off in accordance with ACCEL signal.

On the contrary, when the output of the overcurrent detection means 70 is "H", the base voltage of the transistor Tr13 is almost + V due to the diode D2.
Since it is clamped to _cc , transistor Tr13 turns off,
The transistor Tr11 is also turned off.

Therefore, the transistors Tr12 and Tr5 are also turned off to prevent the drive current from flowing through the spindle motor 10.

The spindle motor drive circuit 20, the + V ₊ is formed by a DC power supply circuit (not shown), -V _{-, +} + V _cc of the DC power supply voltage + power terminal E, - power supply terminal E _-, + supply terminal V _-
Is supplied to.

Then, + V _cc is also supplied to the spindle controller 30.

In the case of this embodiment, as an example, + _Vcc = + 5V, | + V ₊
| = | -V _- | a> + V _cc.

Next, the operation of this embodiment will be described with reference to the time chart of FIG.

The current flowing through the resistor R is referred to as the drive current I.

In addition, the ACCEL signal output of the spindle controller 30 is set to the “H” level in advance, the transistor Tr11 is turned off, the transistors Tr12 and Tr5 are also turned off accordingly, and no current flows in the spindle motor 10. It is assumed to be in a stopped state.

At this time, the detection voltage across the resistor R is zero, and the output of the overcurrent detection means 70 is at the “L” level (see FIG. 2 (4)).

In this state, when the spindle motor 10 is activated by the user's PLAY start operation, the spindle controller 30 sets the F / R signal to the “H” level and sets the ACCEL signal to “H” for a certain time. L "level (Fig. 2 (1),
(See (2)).

When the output of the overcurrent detection means 70 is "L", the transistor
Tr13 is on (see Fig. 2 (5)).

Here, when the "L" level is applied to the base of the transistor Tr11, the transistor Tr11 is turned on.

Then, the transistors Tr12 and Tr5 are also turned on (see FIG. 2 (6)).

On the other hand, since the F / R signal is at "H" level, transistors Tr8 and Tr9 turn on, transistors Tr7 and Tr10 turn off, transistor Tr6 turns on, and transistor Tr1 turns on.
Tr4 turns off and transistors Tr2 and Tr3 turn on.

Therefore, the drive current I flows through the path of + V ₊ , + power supply terminal E ₊ , transistor Tr3, spindle motor 10, transistor Tr2, resistor R, choke coil L, transistor Tr5, −power supply terminal E ₋ , −V ₋ , The spindle motor 10 is driven in the forward direction.

When the spindle motor 10 starts up, the drive current I
Rapidly increases from zero and becomes a large starting current.

The magnitude of this starting current is detected by the resistor R and a detection voltage is output.

The detection voltage detected by the resistor R is amplified by the first operational amplifier 60 and then amplified by the second operational amplifier 62 at the reference voltage E.
compared with _ref .

When the spindle motor 10 starts up,
When the magnitude of the drive current I is lower than the predetermined reference drive current I _{0 and} the output of the first operational amplifier 60 does not exceed the reference voltage E _ref , the output of the second operational amplifier 62 maintains the “L” level. , The transistor Tr13 continues to be in the ON state (see broken lines A to D on the left side of FIGS. 2 (3) to (6)).

Therefore, the drive current I continuously flows through the spindle motor 10 and is accelerated.

On the contrary, when the magnitude of the drive current I exceeds the predetermined reference level I ₀ and the output voltage of the first operational amplifier 60 exceeds the reference voltage E _ref during the rising of the spindle motor 10, the second operational amplifier 62 is released. Outputs an "H" level overcurrent detection signal (see solid lines in FIGS. 2 (3) and (4)).

Then, the base voltage of the transistor Tr13 changes to the diode D2.
Is almost + _Vcc due to the clamping action of the transistor T
r13 turns off (see the solid line in Fig. 2 (5)).

With the turning off of this transistor Tr13, the transistor
Tr11 turns off, and transistors Tr12 and Tr5 also turn off (second
(See the solid line in Fig. 6).

As a result, the drive current I flowing through the spindle motor 10 drops to near zero, and the spindle motor 10
The damage of the transistors Tr1 to Tr5 is prevented.

When the drive current I drops to near zero, the detection voltage of the resistor R also drops to near zero, and the output of the first operational amplifier 60 becomes the reference voltage.
Since it becomes lower than E _ref , the output of the second operational amplifier 62 returns to the “L” level (see FIG. 2 (4)).

Therefore, the transistor Tr13 is turned on again and the transistor Tr11 is also turned on, so that the transistors Tr12 and Tr5 are also turned on and the drive current I flows again to the spindle motor 10,
Acceleration is restarted (see (5) and (6) in FIG. 2).

Then, when the drive current I exceeds the predetermined reference level I ₀ again, the drive current I temporarily drops to near zero in the same manner as described above.

After that, when the rotation speed reaches a certain level due to the rise of the spindle motor 10, the spindle controller 30
Turns on the spindle servo and returns an error signal that compares the frequency sync of the H sync in the playback video signal with the reference oscillation signal.
Output as ACCEL signal.

At this time, the ACCEL signal periodically changes between the “L” level and the “H” level (see FIG. 2 (2)).

While the ACCEL signal is at the "L" level, the drive current I flows through the spindle motor 10 to accelerate in the positive direction as described above, and while the ACCEL signal is at the "H" level, the transistor Tr11 is turned on.
Is turned off, and the transistors Tr12 and Tr5 are turned off accordingly. Therefore, the drive current I hardly flows to the spindle motor 10, and braking is applied to decelerate.

Therefore, the spindle motor 10 is driven at a speed according to the duty ratio of the ACCEL signal.

At this time, the rotation of the spindle motor 10 is smoothed by the integrating circuit including the choke coil L and the capacitor C1.

Also, with the speed-up capacitors C2 and C3, the transistor Tr11 and
Since the transistors Tr12 and Tr5 are turned on / off with good responsiveness, the control response of the spindle motor 10 becomes good.

Here, the diode D2 for clamping is the transistor Tr
Separated from the base circuit of 11, so the diode
The capacitive component of D2 does not deteriorate the on / off response of the transistor Tr11 to the ACCEL signal.

After that, when the disk is stopped according to the STOP operation of the user, the spindle controller 30 sets the F / R signal and the ACCEL signal to the “L” level for a certain time (FIG. 2, (1),
(See (2)).

When the F / R signal goes to "L" level, transistors Tr8 and Tr
9 turns off, transistors Tr7 and Tr10 turn on, transistor Tr6 turns off, transistors Tr1 and Tr4 turn on, and transistors Tr2 and Tr3 turn off.

Therefore, the drive current I flows in the route of + V ₊ , + power supply terminal E ₊ , transistor Tr1, spindle motor 10, transistor Tr4, resistor R, choke coil L, transistor Tr5, −power supply terminal E ₋ , −V ₋ , The spindle motor 10 is driven in the reverse direction.

As a result, the spindle motor 10 is rapidly decelerated.

Then, when the rotation speed of the spindle motor 10 approaches zero, the spindle controller 30 sets the ACCEL signal to the "H" level (see (2) in FIG. 2).

When the ACCEL signal goes to "H" level, the transistor Tr11 is turned off, the transistors Tr12 and Tr5 are turned off accordingly, and the spindle motor 10 is stopped (Fig. 2 (6)).
reference).

If the drive current I exceeds a predetermined reference level I ₀ during the rapid deceleration of the spindle motor 10, the detection voltage of the resistor R increases as described above, and the first operational amplifier 60
Output of the second operational amplifier exceeds the reference voltage E _ref.
62 outputs an "H" level overcurrent detection signal (see (a) and (b) in FIGS. 2 (3) and (4)).

Therefore, the transistor Tr13 turns off and the transistor Tr11
Is also turned off, the transistors Tr12 and Tr5 are turned off, the drive current I becomes close to zero, and the spindle motor 10 and
An excessive current is prevented from flowing through the transistors Tr1, Tr4, Tr5 (see (c) and (d) in FIGS. 2 (5) and (6)).

When the drive current I becomes close to zero, the detection voltage of the resistor R becomes close to zero, and the output of the first operational amplifier 60 becomes the reference voltage E.
Since it falls below _ref , the output of the second operational amplifier 62 becomes "L" again, and the transistor Tr13 is turned on (see (3), (4), and (5) in FIG. 2).

Therefore, the transistor Tr11 is turned on in accordance with the ACCEL signal to turn on the transistors Tr12 and Tr5, and the drive current I in the reverse direction is again supplied to the spindle motor 10 to restart the rapid deceleration operation (Fig. 2 (6)). reference).

Hereinafter, the same operation is performed until the spindle motor 10 stops.

According to this embodiment, the spindle motor drive circuit 20
Input the ACCEL signal to turn on transistor Tr5.
A transistor Tr13 is connected in series between the transistor Tr11 that performs the off control and the + power supply terminal V ₊ to provide an overcurrent detection means.
Since the overcurrent detection signal output by 70 is applied to the base of the transistor Tr13, and the clamping diode D2 is interposed between the base of the transistor Tr13 and the + power supply terminal V ₊ , the overcurrent detection means 70 becomes "H". When a level-overcurrent detection signal is output, the transistor Tr11 can be turned off in accordance with the turning off of the transistor Tr13 to prevent an excessive drive current I from flowing, while the base circuit of the transistor Tr11 causes the diode D2 to flow. By disconnecting, the ON / OFF responsiveness of the transistor Tr11 to the ACCEL signal that changes at high speed can be prevented from being deteriorated.

In the above-mentioned embodiment, the spindle motor system of the LD player is taken as an example, but the invention is not limited to this, and is applied to a spindle motor system of a CD player or other disc players, It may be applied to a motor drive circuit other than the disc player.

[Effect of device]

In the motor drive circuit of the present invention, a control transistor that switches a power transistor according to an accelerator signal input from the outside and a transistor that is turned on / off according to an overcurrent detection signal are connected in series between a power supply and the base of this transistor. Since the diode for clamping is interposed between the power supply and the power supply, the diode for clamping is disconnected from the control transistor, and the on / off response of the control transistor to the accelerator signal becomes good.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a spindle motor system of an LD player according to one embodiment of the present invention, FIG. 2 is a time chart showing the operation of FIG. 1, and FIG. 3 is a spindle motor drive of a conventional LD player. It is a circuit diagram of a circuit. Explanation of main symbols 10: Spindle motor, 20: Spindle motor drive circuit, 30: Spindle controller, 70: Overcurrent detection means,
Tr5, Tr11, Tr12, Tr13: Transistor, D2: Diode.

Claims (1)

[Scope of utility model registration request] 1. A motor drive circuit comprising: a control transistor for switching a power transistor in accordance with an accelerator signal input from the outside; and an overcurrent detection means for outputting an overcurrent detection signal when the drive current becomes an overcurrent. A motor drive circuit characterized in that a transistor for turning on / off according to an overcurrent detection signal is connected in series between a control transistor and a power supply, and a clamp diode is interposed between the base of this transistor and the power supply.