JPH0614790B2 - Motor drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit composed of a semiconductor integrated circuit such as a bipolar IC, and particularly to a reverse drive which occurs in a motor when rotation is stopped or rotation direction is switched. The present invention relates to suppression of a parasitic transistor effect generated at the time of an abnormality such as a potential of a conductive region where a driving transistor is formed by an electromotive force lower than that of a semiconductor substrate.

[Conventional technology]

FIG. 3 shows a conventional bridge type motor drive circuit. In this motor drive circuit, a pair of first transistors 4 and 6 are selectively turned on in accordance with the rotation direction and a drive current is supplied to the motor 2. And a pair of second transistors 8 and 10 for drawing the drive current from the motor 2 are installed. The driving power supply 14 is connected between the power supply terminal 12 and the ground point (GND), and V _CC is the voltage thereof.

A switching signal is applied from the drive control circuit 18 to the bases of the transistors 4, 6, 8 and 10 in response to the forward or reverse rotation command applied to the input terminals 16A and 16B.

For example, during normal rotation, the transistors 4 and 10 are conductive, and during reverse rotation, the transistors 6 and 8 are conductive, but when stopping the motor 2 during normal rotation, the transistor 4 is made non-conductive and the transistor 8 is made conductive. When the motor 2 is stopped during reverse rotation, the transistor 6 is made non-conductive and the transistor 10 is made conductive.

Then, due to the back electromotive force generated by stopping the motor 2 or switching the rotation direction, the transistor 8
Alternatively, diodes 20 and 22 are inserted between the collector and the reference potential point in order to prevent the motor-side terminal of the transistor 10, that is, the collector thereof from becoming abnormally low potential.

[Problems to be solved by the invention]

However, when such a motor drive circuit is formed of a bipolar semiconductor integrated circuit, the back electromotive force generated in the motor 2 causes the substrate-collector diode of the semiconductor integrated circuit to collect the collector of the transistor 8 or the transistor 10. At the same time as the potential is clamped, the parasitic transistor 24 operates.

For example, when the epitaxial layer (N layer) 26 formed on the semiconductor substrate has a lower potential than the semiconductor substrate (P layer), in this case, the NPN type parasitic transistor 24 is formed. That is, since the collector of the parasitic transistor 24 is composed of the epitaxial layer 26 of another adjacent integrated circuit element, the parasitic transistor 24
When it operates, it has a drawback that it affects other adjacent integrated circuit elements and causes malfunctions in those elements and circuits.

For example, the current amplification factor h _FE of the parasitic transistor 24 is
Although it is about 0.1 to 0.2, in the motor drive, the base current flowing into the parasitic transistor 24 due to the back electromotive force has a value of about 1 (A) instantaneously (100 msec), so that other The effect on elements and circuits is significant.

For this reason, when forming a transistor that drives an inductive load such as a motor or a capacitive load, it is necessary to pay attention to the layout to reduce the parasitic transistor effect, even if it cannot be eliminated. Layout design was very troublesome.

Therefore, the present invention is intended to prevent adverse effects on other elements such as a parasitic transistor generated by such an abnormal potential such as back electromotive force.

[Means for solving problems]

As illustrated in FIGS. 1 and 2, the motor drive circuit of the present invention includes a first transistor connected in series to the motor for supplying a drive current, and a first transistor connected in series to the motor for supplying the drive current. Second retracting via the motor
And a transistor for forming a transistor, the epitaxial layer formed on a semiconductor substrate is separated by a first isolation region to form a first epitaxial layer, and the first epitaxial layer is used as a collector. The first transistor is formed in the first epitaxial layer, and a second epitaxial layer partitioned by a second isolation region is formed inside the first epitaxial layer, and the second epitaxial layer is formed. Is formed in this second epitaxial layer.

[Work]

In the motor drive circuit shown in FIG. 1, for example, when the rotation of the motor 2 is stopped, a counter electromotive force is generated between its terminals, and the collector of the second transistor 10 (motor 2
If is reversed, the collector of transistor 8)
Shifts to a potential lower than that of the semiconductor substrate 30. At this time, the parasitic transistor 66 as shown in FIG. 2 is generated, but most of the base current and collector current of the parasitic transistor 66 form the power supply terminal 12 and the first transistor 6 connected to the power supply. Is rapidly supplied from the collector side (in the case of the transistor 8, the collector of the transistor 4), the influence of the parasitic transistor 66 on other adjacent elements and the control circuit is avoided.

〔Example〕

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

1 and 2 show an embodiment of the motor drive circuit of the present invention, and the same parts as those of the motor drive circuit shown in FIG. 3 are designated by the same reference numerals.

As shown in FIG. 1, for example, on a semiconductor substrate 30 of P-type conductivity type, transistors 4, 8 or transistors 6, 10 are formed adjacent to each other. As shown in FIG. After a buried layer 32 having a conductivity type opposite to that of the semiconductor substrate 30 is formed on the surface layer of the semiconductor substrate 30, the semiconductor substrate 3
A conductive region having a conductivity type opposite to 0, for example, an N type epitaxial layer 34 is formed. The epitaxial layer 34 has a conductivity type opposite to that of the epitaxial layer 34, for example, in order to electrically insulate and separate other semiconductor circuits such as a semiconductor device formed adjacently and a semiconductor element such as a transistor.
The P-type first isolation region 36 is formed, and the first epitaxial layer 3 serving as the collector region of the transistors 4 and 6 is formed.
4a is partitioned.

The transistors 4 and 6 are formed in the epitaxial layer 34a, and the second epitaxial layer 34b is formed by being partitioned by the second isolation region 38. That is, the epitaxial layer 34b is the transistor 8, 1
Since the collector region of 0 is formed, the transistors 8 and 1
0 is surrounded by the transistors 4, 6 via the isolation region 38.
Is surrounded by an epitaxial layer 34a serving as a collector region of.

The transistors 4 and 6 formed in the first epitaxial layer 34a are for extracting electrodes for the base region 40 having the opposite conductivity type to the epitaxial layer 34a, the emitter region 42 and the collector region having the same conductivity type as the epitaxial layer 34a. The transistors 8 and 10 formed in the second epitaxial layer 34b also include a conductive region 50 for drawing electrodes to the base region 46, the emitter region 48 and the collector region. ing.

An oxide film 52 is formed on the surface of the semiconductor integrated circuit thus formed, and each base region 40, 46, emitter region 42, 48 and conductive region 44 of each transistor 4, 8 or transistors 6, 10 is formed. , 50, base electrodes 54B, 56B, emitter electrodes 58E, 60E and collector electrodes 62C, respectively.
64C is formed.

The operation will be described based on the above configuration.

In the motor drive circuit shown in FIG. 3, when the rotation of the motor 2 is stopped, a counter electromotive force is generated between the terminals of the motor 2, so that the collectors of the transistors 8 and 10 are
The potential of the semiconductor substrate 30 shifts to a lower potential.

In this case, the epitaxial layer 34b which is the collector region of the transistors 8 and 10 is the emitter, the isolation region 38 is the base, and the epitaxial layer 34a which is the collector region of the transistors 4 and 6 is the first collector C ₁ and the isolation region 36.
A parasitic transistor 66 having the second collector C ₂ outside the epitaxial layer 34 is generated.

The base current of the parasitic transistor 66 is supplied from the power supply via the semiconductor substrate 30, and the first collector C
_The collector current flowing through ₁ is supplied from the power source connected to the collector side of the transistors 4 and 6, and the second collector C
_The collector current flowing in ₂ flows in from the epitaxial layer 34.

Therefore, in the motor drive circuit shown in FIG. 3, the current flowing in the first collector C ₁ of the parasitic transistor 66 is supplied from the positive side of the power source connected to the power source terminal 12 on the collector side of the transistors 4 and 6. .

Therefore, since the transistors 8 and 10 are surrounded by the collector regions of the transistors 4 and 6 connected to the positive side of the power supply, when the collector regions of the transistors 8 and 10 become lower than the potential of the semiconductor substrate 30. The compensation current is immediately supplied from the power source in accordance with the potential change in the collector regions of the transistors 8 and 10, and the influence on other adjacent elements and control circuits is effectively suppressed.

In particular, in the motor drive circuit, since the power supply of the drive control circuit 18 and the power supply of the drive elements such as the transistors 4, 6, 8, 10 are separated, there is no influence on the power supply of the drive control circuit 18, which is advantageous. is there.

Although the P-type semiconductor substrate is described as an example in the embodiment, the parasitic transistor is similarly formed in the case of the N-type semiconductor substrate by setting a conductive region having a conductivity type opposite to that of the above-described embodiment. It goes without saying that the effect can be suppressed.

〔The invention's effect〕

As described above, according to the present invention, the following effects can be obtained.

(a) Since the second transistor whose conductive region is lower than the potential of the semiconductor substrate due to the driving stop or reversal of the motor is surrounded by the conductive region forming a part of the first transistor, the parasitic transistor effect can be suppressed. The influence on adjacent semiconductor elements and semiconductor circuits can be reduced.

(b) The second region is formed in the conductive region forming a part of the first transistor.
It is unnecessary to pay attention to the layout position of the formation region of the second transistor because a part of the second transistor is formed, and the layout design can be facilitated and the semiconductor substrate can be downsized. .

(c) The conductive region surrounding the second transistor is formed of the collector region of the adjacent first transistor, and is formed simultaneously with the steps of the first and second transistors,
No special process is required.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a motor drive circuit of the present invention, FIG. 2 is a sectional view showing a main part taken along line II-II of FIG. 1, and FIG. 3 is a general motor drive circuit. 3 is a circuit diagram showing the configuration of FIG. 4, 6 ... First transistor, 8, 10 ... Second transistor, 34a, 34b ... Epitaxial layer as conductive region.

Claims (1)

[Claims] 1. A motor comprising: a first transistor connected in series to a motor for supplying a drive current; and a second transistor connected in series to the motor for drawing the drive current through the motor. A driving circuit, wherein an epitaxial layer formed on a semiconductor substrate is separated by a first isolation region to form a first epitaxial layer, and the first transistor having the first epitaxial layer as a collector is Forming a first epitaxial layer and forming a second epitaxial layer partitioned by a second isolation region inside the first epitaxial layer,
A motor drive circuit characterized in that a second transistor having the second epitaxial layer as a collector is formed on the second epitaxial layer.