JPH0738351A - Constant-current driving circuit - Google Patents

Abstract

PURPOSE:To enhance the degree of freedom of a design of the constant-current driving circuit of a BTL system by a master amplifier and a slave amplifier, especially, the degree of freedom of a gain design of the master amplifier by allowing a inversion input of the master amplifier in which a generated voltage of a current detecting resistance is fed back to be subjected to virtual short circuit to the reference potential by a negative feedback operation of its master amplifier. CONSTITUTION:By an output Vo1 of a master amplifier 1 and an output Vo2 of a slave amplifier 2, a load ZL is subjected to two-phase driving by a BTL system. An energizing current Io of a load ZL driven by two amplifiers 1, 2 is detected by a current detecting resistance Rs, and subjected to negative feedback to an inversion input (-) side of the master amplifier 1 through a resistance R2. As a result, the energizing current Io to the load ZL is controlled in accordance with an input signal Vin. In this case, in the master amplifier 1, a negative feedback operation is executed so that the potential by its inversion input (-) follows the potential by a non-inversion input (+). In such a way, the input potential comes to be held in a roughly constant potential.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant current driving circuit, and more particularly to a technique effective when applied to a BTL type constant current driving circuit which performs two-phase driving by a master amplifier and a slave amplifier. The present invention relates to a technique effectively used for a head actuator of a disk storage device.

[0002]

2. Description of the Related Art In a hard disk storage device, an optical disk storage device, and the like, a voice coil motor is used in the drive portion of its head actuator. To drive the voice coil motor, for example, as shown in FIG. Constant current drive circuit is used.

FIG. 3 shows a constant current drive circuit studied by the present inventors. First, a master amplifier 1 which is negatively feedback operated as an inverting amplifier circuit by resistors R1 and R2.
And a slave amplifier 2 which is negatively feedback operated as a mirror inversion circuit by the resistors R3 and R5.
in is amplified by the master amplifier 1 by inversion, and one terminal of the load (voice coil) ZL is energized and driven by the inverted amplification output Vo1, and the output Vo1 of the master amplifier 1 is mirror-inverted by the slave amplifier 2; This mirror inverted output Vo2 (Vo2 = -Vo1)
Thus, the other terminal of the load ZL is energized and driven. As a result, the two-phase drive of the load ZL by the master amplifier 1 and the slave amplifier 2 is called BTL.
Drive is performed.

At the same time, a current detection resistor Rs is interposed in series between the output of the master amplifier 1 and the load ZL, and the voltage Vo3 appearing at the end of the current detection resistor Rs on the load ZL side is not applied to the master amplifier 1. It feeds back to the inverting input (+) side.

Then, a negative feedback operation is performed in which the potential at the inverting input (-) of the master amplifier 1 follows the potential at the non-inverting input (+).
The energizing current Io to L is controlled according to the input signal Vin.

As a reference for the constant current drive circuit described above, for example, "IC databook for Hitachi OA equipment" HA13490 series "'90 .3"
387-390 pages.

[0007]

However, the present inventors have clarified that the above-mentioned technique has the following problems.

That is, the maximum input voltage range of the inverting input (-) and the non-inverting input (-) of the master amplifier 1, that is, the so-called common-mode input voltage range is finite, and normal operation is performed with an input voltage exceeding that range. Not done.

On the other hand, in the constant current drive circuit shown in FIG.
The negative feedback operation in which the potential at the inverting input (-) of the master amplifier 1 follows the potential at the non-inverting input (+) controls the energizing current Io to the load ZL. The potential at () varies depending on the voltage Vo3 fed back from the current detection resistor Rs.

Therefore, when the gain setting of the master amplifier 1 is small (R1 >> R2), if the voltage Vo3 fed back from the current detection resistor Rs to the non-inverting input (+) largely fluctuates, the input voltage of the master amplifier 1 becomes the above. The common-mode input voltage range may be exceeded, and latch-up may occur in some cases.

Therefore, in the constant current drive circuit described above,
There is a problem that the degree of freedom in the design is low, and in particular, the gain in the master amplifier 1 cannot be freely designed.

An object of the present invention is to provide a technique for increasing the degree of freedom in designing a BTL type constant current drive circuit using a master amplifier and a slave amplifier.

The above and other objects and features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[0014]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

That is, one terminal of a load is energized and driven by a master amplifier that inverts and amplifies an input signal, and the other terminal of the load is energized and driven by a slave amplifier that mirror-inverts the output of this master amplifier. The generated voltage of the current detection resistor interposed in series is fed back to the inverting input side of the master amplifier to control the current flowing to the load according to the input signal.

[0016]

According to the above-mentioned means, the inverting input of the master amplifier to which the generated voltage of the current detection resistor is fed back is virtually short-circuited to the reference potential by the negative feedback operation of the master amplifier, so that it is maintained at a substantially constant potential. You will be drunk.

Thus, the input voltage of the master amplifier does not exceed the in-phase input voltage range, and the purpose of increasing the design flexibility of the BTL type constant current drive circuit by the master amplifier and the slave amplifier is achieved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

In the figures, the same reference numerals indicate the same or corresponding parts.

FIG. 1 shows an embodiment of a constant current drive circuit to which the technique of the present invention is applied.
1, a master amplifier which is negatively feedback operated as an inverting amplifier circuit by R2, 2 is a slave amplifier which is negatively feedback operated as a mirror inverting circuit by a resistor R3, and ZL is BTL by an output Vo1 of the master amplifier 1 and an output Vo2 of the slave amplifier 2. A load (voice coil motor) to be driven, Rs is a current detection resistor for detecting the energization current Io of the load ZL.

Here, each of the master amplifier 1 and the slave amplifier 2 is constructed by using a differential type operational amplifier having an inverting input (-) and a non-inverting input (+).
A negative feedback operation can be performed as an inverting amplifier circuit. Negative feedback is applied to the inverting inputs (-) of the amplifiers 1 and 2 by the resistors R2 and R3, respectively, but the resistors R4 and R5 are respectively provided on the non-inverting input (-) side.
Is connected to the reference potential Vref via. A fixed potential such as a ground potential is used as the reference potential Vref.

The master amplifier 1 inverts and amplifies the input signal Vin applied to the inverted input (-) to which the negative feedback is applied, and energizes and drives one terminal of the load ZL by this amplified output Vo1. The slave amplifier 2 mirror-inverts (phase-inverts) the output Vo1 of the master amplifier 1 with respect to the reference potential Vref, and outputs the mirror-inverted output Vo2 (Vo
2 = −Vo1), the other terminal of the load ZL is energized and driven.

The current detection resistor Rs is interposed in series between the other terminal of the load ZL and the output Vo2 of the slave amplifier 2 and detects the energizing current Io to the load ZL. The voltage Vo3 appearing at the connection point between the current detection resistor Rs and the load ZL is negatively fed back to the inverting input (−) side of the master amplifier 1 via the resistor R3.

Next, the operation will be described.

In the constant current drive circuit shown in FIG. 1, the output Vo1 of the master amplifier 1 and the output Vo of the slave amplifier 2 are shown.
The load ZL is two-phase driven by the BTL method by the method 2. Two
The conduction current Io of the load ZL driven by the two amplifiers 1 and 2 is detected by the current detection resistor Rs and
Negative feedback is provided via 2 to the inverting input (−) side of the master amplifier 1. As a result, the current Io applied to the load ZL
Are controlled according to the input signal Vin.

At this time, the master amplifier 1 performs a negative feedback operation such that the potential at its inverting input (-) follows the potential at its non-inverting input (+). That is, the inverting input (-) of the master amplifier 1 to which the generated voltage Vo3 of the current detection resistor Rs is fed back is virtually short-circuited to the reference potential Vref by the negative feedback operation of the master amplifier 1, and the input potential becomes almost constant. Will be kept.

As a result, the input voltage of the master amplifier 1 does not exceed the in-phase input voltage range, and the design of the BTL type constant current drive circuit by the master amplifier 1 and the slave amplifier 2, especially the gain design of the master amplifier 1, is free. You will be able to do it.

In the circuit shown in FIG. 1, the relationship between the input signal Vin and the conduction current (output current) Io is calculated as follows.

Io = −Vin × (R2 / R1) × (1 / Rs) FIG. 2 shows another embodiment of the present invention, in which the current source Iin is used as the input signal source of the master amplifier 1. Has been done. Thus, the current source Iin is used as the input signal source.
In the case of using, the current source Iin is considered to operate in the same manner as in the embodiment shown in FIG. 1 by considering an equivalent output resistance corresponding to the input resistance R1.

The invention made by the present inventor has been specifically described above based on the embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the master amplifier 1 and the slave amplifier 2 can also be constructed by using an inverting amplifier with one input terminal.

In the above description, the case where the invention made by the present inventor is mainly applied to drive a head actuator of a disk storage device, which is a field of application which is the background of the invention, has been described, but the present invention is not limited thereto. It can also be applied to drive a constant torque generating motor or an acoustic speaker, for example.

[0033]

The effects of the typical ones of the inventions disclosed in this application will be briefly described as follows.

That is, there is an effect that the degree of freedom in designing a BTL type constant current drive circuit using a master amplifier and a slave amplifier can be increased.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a constant current drive circuit to which the technique of the present invention is applied.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration example of a constant current drive circuit before the present invention.

[Explanation of symbols]

 1 Master amplifier 2 Slave amplifier ZL Load (Voice coil) Rs Current detection resistor-Inverted input + Non-inverted input

Claims (2)

[Claims] 1. A master amplifier for inverting and amplifying an input signal applied to an inverting input under negative feedback, and energizing and driving one terminal of a load by this amplified output, and the output of this master amplifier is mirror-inverted. It has a slave amplifier that energizes and drives the other terminal of the load by an inverting output, and feeds back the generated voltage of a current detection resistor that is interposed in series to the load to the inverting input side of the master amplifier. A constant current drive circuit, characterized in that the energization current is controlled according to the input signal. 2. A master amplifier for inverting and amplifying an input signal applied to an inverting input under negative feedback, and energizing and driving one terminal of a load by this inverting and amplified output, and a mirror inverting of the output of this master amplifier. A slave amplifier that energizes and drives the other terminal of the load by mirror inversion output, a current detection resistor that is interposed in series between the output of the slave amplifier and the other terminal of the load, and the current detection resistor and the load. The constant current drive circuit is characterized in that the current flowing to the load is controlled according to the input signal by feeding back the voltage appearing at the connection point with the other terminal of the above to the inverting input side of the master amplifier.