JP3276734B2 - Motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit capable of preventing output transistors connected to both ends of a coil from being short-circuited when the direction of current supply to the coil is switched.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional motor drive circuit. In FIG. 4, (1) is a Hall element (magnetoelectric conversion element), one power supply terminal is connected to a power supply Vcc via a resistor (2), and the other power supply terminal is grounded. It is fixed in position. When the rotor of the motor is rotating, the Hall element (1) performs a magnetoelectric conversion of a magnetic force change of a coil winding fixed at a predetermined position of the rotor, and generates a sine wave signal a of FIG. is there. Note that the frequency of the sine wave signal a generated from the Hall element (1) is proportional to the rotation speed of the motor.
(3) is an amplifier that amplifies the sine wave signal a and converts the sine wave signal a into a square wave signal b in FIG. 6 that changes to high and low levels at a zero cross point. (4) is a distributor for generating a square wave signal c of FIG. 6 obtained by inverting the square wave signal b (as it is) and a square wave signal d of FIG. 6 obtained by inverting the square wave signal b. is there. Reference numeral (5) denotes a drive circuit which switches the direction of energization of the coil (6) in accordance with two-phase square wave signals c and d generated from the distributor (4).

Hereinafter, a specific circuit of the driving circuit (5) will be described with reference to FIG. (7) is an NPN type transistor. A square wave signal c is applied to a base, and a collector is connected to a power supply Vcc via a resistor (8). The square wave signal c rises to a high level when a drive current is supplied from the A terminal to the B terminal of the coil (6), and falls to a low level when no drive current is supplied to the coil (6). Has become. (9) is a PNP transistor. The base is connected to the collector of the transistor (7), and the emitter is connected to the power supply Vcc. (10) is an NPN type source transistor, the base is connected to the collector of the transistor (9), and the collector is the power supply V.
cc, and the emitter is connected to the A terminal of the coil (6). (11) is an NPN transistor, and the base is a transistor (7) via a resistor (12).
And the collector is grounded via a resistor (13), the collector is connected to a power supply Vcc via a resistor (14), and the emitter is grounded via a resistor (15). (16) is an NPN type sink transistor,
The base is connected to the emitter of the transistor (11),
The collector is connected to the B terminal of the coil (6), and the emitter is grounded. (17) and (18) are regenerative diodes which form a loop for absorbing the back electromotive force of the coil (6) when the square wave signal c falls from the high level to the low level. The cathode of the regenerative diode (17) is connected to the power supply Vcc, and the anode is the B of the coil (6).
Connected to terminal. The cathode of the regenerative diode (18) is connected to the A terminal of the coil (6), and the anode is grounded.

Similarly, (19) is an NPN type transistor, a square wave signal d is applied to a base, and a collector is connected to a power supply Vcc via a resistor (20).
The square wave signal d rises to a high level when a drive current is supplied from the B terminal to the A terminal of the coil (6), and falls to a low level when no drive current is supplied to the coil (6). Has become. That is, when the motor is rotated, the square wave signals c and d alternately become high and low levels.
(21) is a PNP transistor, the base is connected to the collector of the transistor (19), and the emitter is connected to the power supply Vcc. (22) is an NPN type source transistor, and the base is a transistor (21).
, The collector is connected to the power supply Vcc, and the emitter is connected to the B terminal of the coil (6). (23) is an NPN transistor, whose base is connected to the emitter of the transistor (19) via a resistor (24) and grounded via a resistor (25);
The collector is connected to the power supply Vcc via the resistor (26),
The emitter is grounded via a resistor (27). (2
Reference numeral 8) denotes an NPN-type sink transistor, whose base is connected to the emitter of the transistor (23), whose collector is connected to the A terminal of the coil (6), and whose emitter is grounded. (29) and (30) are regenerative diodes,
This element forms a loop for absorbing the back electromotive force of the coil (6) when the square wave signal d falls from the high level to the low level. The cathode of the regenerative diode (29) is connected to the power supply Vcc, and the anode is connected to the A terminal of the coil (6). The cathode of the regenerative diode (30) is connected to the B terminal of the coil (6), and the anode is grounded.

First, when the square wave signal c is at a high level and the square wave signal d is at a low level, the source transistor (1
0) and the sink transistor (16) are turned on, and a drive current flows from the A terminal to the B terminal of the coil (6). From this state, the square wave signal c becomes low level and the square wave signal d
Changes to a high level, the source transistor (1
0) and the sink transistor (16) are turned off, but a back electromotive force is generated based on the characteristics of the coil, and the coil (6) is turned off.
, The drive current will continue to flow from the A terminal to the B terminal. This drive current is consumed by circulating through a loop consisting of the coil (6), the regenerative diode (17), the power supply Vcc, the ground, and the regenerative diode (18). That is,
The back electromotive force can be absorbed. At the same time, the source transistor (22) and the sink transistor (28) are turned on, and a drive current starts to flow from the terminal B to the terminal A of the coil (6). From this state, the square wave signal c becomes high level,
When the square wave signal d changes to the low level again, the source transistor (22) and the sink transistor (28) are turned off, but a back electromotive force is generated based on the characteristics of the coil, and A is output from the B terminal of the coil (6). The drive current continues to flow in the direction of the terminal. This drive current is consumed by circulating through a loop consisting of the coil (6), the regenerative diode (29), the power supply Vcc, the ground, and the regenerative diode (30). That is, the back electromotive force in the reverse direction can be absorbed. At the same time, the source transistor (10) and the sink transistor (16) are turned on, and a drive current starts flowing from the terminal A to the terminal B of the coil (6). By repeating the above operation, the motor can be normally rotated in a predetermined direction.

When FIG. 5 is formed by a discrete circuit, regenerative diodes (17) (18) (29) (30)
However, when FIG. 5 is formed by an integrated circuit, since the parasitic diodes of the transistors (16) and (28) perform the function of the regenerative diode, the regenerative diode (17) is used.
(29) becomes unnecessary.

[0007]

However, each time the direction of energization of the coil (6) is switched, the square wave signals c, d
Are instantaneously both at a high level. At this time, a relatively large current (see the power supply current e in FIG. 6) passes through the output paths of the source transistor (10) and the sink transistor (28) and the output paths of the source transistor (22) and the sink transistor (16). Therefore, there is a problem that these transistors are destroyed or the power supply Vcc is reduced.

Accordingly, an object of the present invention is to provide a motor drive circuit in which a source and a sink transistor are not short-circuited even when a current flowing direction of a coil (6) is switched.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is characterized by a sine wave generated from a magnetoelectric conversion element for detecting a rotation state of a motor. Amplifying means for shaping a signal into a square wave signal having hysteresis; distributing means for distributing a square wave signal generated from the amplifying means into two-phase square wave signals obtained by inverting and inverting; First delay means for detecting the rise or fall of one of the square wave signals, and delaying the fall or rise of the other square wave signal corresponding to the rise or fall of the one square wave signal by a predetermined time. Detecting the rise or fall of the other square wave signal generated from the distribution means, and delaying the fall or rise of one square wave signal corresponding to the rise or fall of the other square wave signal by a predetermined time. You A second delay means, a first source and a first sink transistor connected in series between the first and second power supplies via the coil, for flowing a drive current in one direction of the coil; In order to pass the drive current,
A second source and a second sink transistor connected in series between the first and second power supplies via the coil;
Driving means for switching the energizing direction of the coil in accordance with a square wave signal generated from the first and second delay means, wherein when the energizing direction of the coil is switched, the first source and the first sink transistor are switched. And that the second source and second sink transistors are turned off for a predetermined time to prevent a through current from flowing through the first source and second sink transistors and the second source and first sink transistors. It is.

[0010]

According to the present invention, the first source and the first sink transistor and the second source and the second sink transistor can be turned off for a predetermined time when the energizing direction of the coil is switched. It is possible to prevent a through current from flowing through the second sink transistor and the second source and the first sink transistor.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. In FIGS. 1 and 2 and FIGS. 4 and 5, the same elements are denoted by the same reference numerals. FIG. 1 is a diagram showing a motor drive circuit of the present invention. In FIG. 1, (31)
Is an amplifier having a hysteresis composed of a high threshold voltage V _THH and a low threshold voltage V _THL . Amplifier (3
1) amplifies the sine wave signal a of FIG. 3 generated from the Hall element (1) and converts it into a square wave signal b of FIG. 3 which changes to high and low levels at the threshold voltages V _THH and V _THL . Things. The amplifier (31) can absorb the noise with a hysteresis width even if the noise is superimposed on the sine wave signal a, and can prevent malfunction of the first and second delay circuits described later. (32) is a distributor, which generates a square wave signal c obtained by inverting the square wave signal b (as it is) and a square wave signal d obtained by inverting the square wave signal b. (3
3) a first delay circuit, which detects the falling edge of the square wave signal c and outputs a square wave signal d corresponding to the falling edge of the square wave signal c.
Is delayed by a predetermined time. (34)
Denotes a second delay circuit, which detects the fall of the square wave signal d and delays the rise of the square wave signal c corresponding to the fall of the square wave signal d by a predetermined time. That is, the first
The delay circuit (33) generates a square wave signal e that falls at the same time as the fall of the square wave signal c and rises with a predetermined delay from the fall of the square wave signal d. Also, the second delay circuit (34) falls simultaneously with the falling of the square wave signal d,
A square wave signal f that rises with a predetermined delay from the fall of the square wave signal c is generated. Then, the driving circuit (5)
The energizing direction of the coil (6) is switched according to the square wave signals e and f subjected to the delay processing, and the motor is rotated.

FIG. 2 shows a specific circuit of the drive circuit (5) and the first and second delay circuits (33) and (34). First
Inside the delay circuit (33), (35) is an NPN type transistor, a square wave signal c is applied to a base, a collector is connected to a power supply Vcc via a resistor (36), and an emitter is a transistor (7). ) Is connected to the emitter. (37) is a PNP transistor,
The base is connected to the collector of the transistor (35),
The emitter is connected to the power supply Vcc. (38) is NP
An N-type transistor, the base of which is a transistor (3
7) and grounded via a resistor (39), the collector is connected to the base of the transistor (19), and the emitter is grounded.

Similarly, inside the second delay circuit (34), (40) is an NPN transistor, a square wave signal d is applied to the base, and a resistor (41) is connected to the collector.
, And the emitter is connected to the emitter of the transistor (19). (42) is PN
It is a P-type transistor, and the base is a transistor (4
0), and the emitter is connected to the power supply Vcc. (43) is an NPN-type transistor, whose base is connected to the collector of the transistor (42) and grounded via a resistor (44), whose collector is connected to the base of the transistor (7) and whose emitter is grounded. ing.

The operation of FIG. 2 will be described below. First, when the square wave signal c is at a high level and the square wave signal d is at a low level, the source transistor (10) and the sink transistor (16) are turned on, and a driving current flows from the A terminal to the B terminal of the coil (6). Flowing. At this time, the transistor (3
Although 8) is on, the driving circuit (5) is not affected at all because the square wave signal d is originally at a low level.

From this state, when the square wave signal c falls and the square wave signal d rises, the source transistor (10) and the sink transistor (16) are turned off, but the back electromotive force is generated based on the characteristics of the coil. Then, the drive current tries to continue to flow from the A terminal to the B terminal of the coil (6). This drive current is consumed by circulating through a loop consisting of the regenerative diode (17), the power supply Vcc, the ground, and the regenerative diode (18). That is, the back electromotive force is absorbed. At this time, although the transistor (35) is turned off, the transistor (38) is continuously turned on until the transistor (37) is turned off because the transistor (37) is saturated. That is, a square wave signal f obtained by delaying the rise of the square wave signal d by the time required for turning off the transistor (37) is applied to the base of the transistor (19). afterwards,
When the transistor (37) turns off and the square wave signal f rises, the source transistor (22) and the sink transistor (28) turn on, and a drive current starts flowing from the terminal B to the terminal A of the coil (6). Therefore, the energizing direction of the coil (6) is determined by the threshold voltage V _{THH at} which the sine wave signal a intersects,
When switching from the direction from the terminal A to the terminal B to the direction from the terminal B to the terminal A, since the square wave signals e and f are both at a low level, a through current is generated in the source transistor (10) and the sink transistor (28). Output path, and the source transistor (22) and the sink transistor (16)
, So that these transistors can be protected and the power supply Vcc can be prevented from lowering.

In this state, when the square wave signal c rises and the square wave signal d falls, the source transistor (22) and the sink transistor (28) are turned off, but a back electromotive force is generated based on the characteristics of the coil. Then, the drive current tries to continue to flow from the terminal B to the terminal A of the coil (6). This drive current is consumed by circulating through a loop consisting of the regenerative diode (29), the power supply Vcc, the ground, and the regenerative diode (30). That is, the back electromotive force is absorbed. At this time, the transistor (40) is turned off, but the transistor (43) is saturated, so that the transistor (43) is continuously turned on until the transistor (42) is turned off. That is, a square wave signal e obtained by delaying the rise of the square wave signal c by the time required for turning off the transistor (42) is applied to the base of the transistor (7). Thereafter, when the transistor (42) turns off and the square wave signal e rises, the source transistor (10) and the sink transistor (16) turn on, and the drive current starts to flow from the A terminal to the B terminal of the coil (6). . Therefore, the energizing direction of the coil (6) is determined by the threshold voltage V _{THL at} which the sine wave signal a intersects,
When switching from the direction from the terminal B to the terminal A to the direction from the terminal A to the terminal B, the square wave signals e and f are both at a low level, so that a through current is generated in the source transistor (10) and the sink transistor (28). Output path, and the source transistor (22) and the sink transistor (16)
, So that these transistors can be protected and the power supply Vcc can be prevented from lowering.

By repeating the above operation, the motor can be rotated in a predetermined direction in a steady state.

[0018]

According to the present invention, when the energizing direction of the coil is switched, a through current flows to the output path of the first source transistor and the second sink transistor and the output path of the second source transistor and the first sink transistor. It is possible to prevent the transistor from flowing and to prevent the breakdown of these transistors and the reduction in the power supply voltage.

[Brief description of the drawings]

FIG. 1 is a diagram showing a motor drive circuit of the present invention.

FIG. 2 is a diagram illustrating a driving circuit and first and second delay circuits of FIG. 1;

FIG. 3 is a diagram showing main part waveforms of FIG. 1;

FIG. 4 is a diagram showing a conventional motor drive circuit.

FIG. 5 is a diagram illustrating a drive circuit of FIG. 4;

FIG. 6 is a diagram showing main part waveforms of FIG. 4;

[Description of Signs] (5) Drive circuit (31) Amplifier (32) Distributor (33) First delay circuit (34) Second delay circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 6/12

Claims (1)

(57) [Claims] Amplifying means for shaping a sine wave signal generated from a magnetoelectric conversion element for detecting a rotation state of a motor into a square wave signal having hysteresis; Distributing means for distributing the inverted two-phase square wave signal, detecting the rising or falling of one square wave signal generated from the distributing means, and the other corresponding to the rising or falling of the one square wave signal A first delay means for delaying the fall or rise of the square wave signal by a predetermined time, detecting the rise or fall of the other square wave signal generated from the distribution means, and detecting the rise or fall of the other square wave signal Second delay means for delaying the fall or rise of one of the square wave signals corresponding to the fall by a predetermined time; and, for flowing a drive current in one direction of the coil, the coil is placed between the first and second power supplies. Through A first source and a first sink transistor connected in series, and a second source and a second source connected in series via the coil between the first and second power supplies to allow a drive current to flow in the reverse direction of the coil. And a driving means including a sink transistor for switching an energizing direction of the coil in response to a square wave signal generated from the first and second delay means, wherein the first source is switched when the energizing direction of the coil is switched. And turning off the first sink transistor and the second source and second sink transistors for a predetermined time.
A motor drive circuit wherein a through current is prevented from flowing through a source and a second sink transistor and the second source and the first sink transistor.