JP2002101687A - Pwm drive controller of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress distortion in drive current flowing to a drive coil and maintain noise, vibration and rotation irregularity small even when the level of a drive and control signal for varying forguce is large when a motor is driven and controlled in PWM. SOLUTION: A drive waveform generation circuit 1 generates a drive waveform signal based on the U-phase, V-phase and W-phase drive currents flowing to drive coils La-Lc, and variably outputs the waveform in response to a drive control signal level Vc. A PWM conversion circuit 3 converts into the PWM drive signal of pulse width in response to the drive waveform signal level. A drive circuit 5 switches and energizes a three-phase drive current based on the PWM drive signal to the drive coils La-Lc. A limiter circuit 9 fixes it to a limit level to be output to the drive waveform generation circuit 1 when the drive control signal level exceeds the limit level corresponding to the duty 100% of the PWM drive signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PWM drive control device for a motor, and more particularly, to a linear modulation PWM drive system.
The present invention relates to improvement of a WM drive control device.

[0002]

2. Description of the Related Art A motor mounted on a copying machine, a printer, or the like requires a large driving force, for example, a rotational torque, and thus requires a large driving power.

[0003] For this reason, a drive control device for a motor is generally provided with a PWM from the viewpoint of reducing the drive power loss and avoiding damage to a semiconductor switch element or the like which switches a drive current flowing through a drive coil of the motor and energizes the switch. A drive control method is adopted.

Conventionally, as a PWM drive control device of this type, as shown in FIG.
b, U-phase and V-phase which are the sources of the three-phase drive current waveforms flowing to Lc
The drive waveform generation circuit 1 generates the phase and W-phase drive waveform signals, and converts the drive waveform signals into a PWM drive signal having a duty ratio corresponding to the level in the PWM conversion circuit 3. Drive coil L connected in Y
A configuration was adopted in which a drive current was switched to a, Lb, and Lc in accordance with the duty ratio of the three-phase PWM drive signal, and the current was passed.

In such a PWM drive control device, FIG.
As shown in A to C, within a period of 240 electrical degrees, 60
Curve waveform with two maximum peak values shifted by 120 °
U-phase drive waveform signal repeated at intervals of
When the drive waveform generation circuit 1 generates and outputs the same V-phase and W-phase drive waveform signals shifted by 240 °, the drive coils La, Lb, and Lc connected in Y form, as shown in FIG. A drive current flows between the U-V phase, the V-W phase, and the W-U phase, and the rotor (not shown) rotates smoothly.

In addition, if the drive waveform generating circuit 1 is formed so as to generate a drive waveform signal whose peak value changes in accordance with the level of the drive control signal Vc added thereto, for example, the drive control signal Vc level becomes high. If it is smaller, as shown in FIG. 8A, a drive waveform signal having a lower peak value is output, and the PWM conversion circuit 3 outputs a PWM drive signal that is linearly PWM-modulated according to a change in the drive waveform signal level.

On the other hand, when the level of the drive control signal Vc is high, as shown in FIG. 8B, a drive waveform signal having a high peak value is output, and the duty is 10 at the maximum peak value.
A PWM drive signal close to 0% is output, and the drive control signal V
The number of rotations can be controlled by changing the level of c.

FIGS. 8A and 8B show U-phase drive waveform signals, but the same applies to V-phase and W-phase drive waveform signals.

For this reason, as shown in FIG. 6, for example, a detector 7 is arranged near the drive coils La, Lb, Lc to detect the rotational speed of the motor, so that the deviation from a predetermined reference rotational speed is reduced. If the drive control signal Vc is variably added to the drive waveform generation circuit 1, it is possible to keep the rotation speed of the motor constant.

[0010]

However, in the above-described motor PWM drive control device, the drive control signal Vc
A drive waveform signal having a peak value linearly corresponding to the level change is output from the drive waveform generation circuit 1. However, the level of the drive control signal Vc is too large due to restrictions on an actual semiconductor circuit, a power supply voltage to be applied, and the like. In this case, it is likely to be difficult to generate a drive waveform signal having a high peak value corresponding thereto.

That is, when a large drive control signal Vc is applied to the drive waveform generation circuit 1, as shown in FIG.
A drive waveform signal in which the maximum peak value is linearly cut only during the period exceeding the predetermined level is generated by the drive waveform generation circuit 1, and the PWM drive signal converted and output from the PWM conversion circuit 3 is also 100% only during that period. It is easy to output a signal that remains saturated and remains on.

Therefore, the driving circuit 5
a, the drive current flowing to Lb, Lc is easily distorted, and noise,
There is a problem that it is difficult to ensure smooth rotation drive due to occurrence of vibration and uneven rotation.

For example, in a copier, when starting or when a heavy load that saturates the PWM drive signal occurs, an excessive load is applied to the motor and a large level drive control signal V
c is easily added to the drive waveform generation circuit 1, and its improvement has been desired.

The present invention has been made to solve such a conventional drawback, and does not saturate a drive waveform signal or a PWM drive signal even when a large level of a drive control signal is applied, so that a drive coil It is an object of the present invention to provide a PWM drive control device that suppresses distortion of a drive current flowing to the drive device and is less likely to generate noise, vibration, and rotational unevenness.

[0015]

According to the present invention, there is provided a drive waveform for variably generating and outputting a drive waveform signal corresponding to a level change of a drive control signal for controlling a driving force of a motor. A generation circuit, a PWM conversion circuit that outputs a PWM drive signal having a pulse width corresponding to the drive waveform signal level, and a drive that switches and supplies a three-phase drive current to a drive coil of the motor based on the PWM drive signal to rotate the drive coil. And a limiter circuit for limiting the drive control signal level to a level corresponding to a duty of 100% and outputting the drive control signal level to a drive waveform generation circuit when the level of the drive control signal exceeds a level corresponding to a duty of 100% of the PWM drive signal. ing.

In the present invention, the limiter circuit may be formed so as to limit the drive control signal by a constant voltage diode.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Note that parts common to those of the conventional configuration are denoted by the same reference numerals.

FIG. 1 is a block diagram showing an embodiment of a motor PWM drive control device according to the present invention.

In FIG. 1, a driving waveform generating circuit 1 is a source of a three-phase driving current waveform to be supplied to driving coils La, Lb, and Lc, which will be described later.
It is a conventionally known one that generates V-phase and W-phase drive waveforms, and is connected to the PWM conversion circuit 3.

The driving waveform generating circuit 1 is provided with the above-mentioned FIGS.
As shown in FIG. C, the curve waveforms having two maximum peak values shifted by 60 ° within a continuous electrical angle of 240 ° are represented by 1
U-phase drive waveform signal repeated at 20 ° intervals,
A similar drive waveform signal of V phase and W phase shifted by 20 ° and 240 ° is generated, and a drive waveform signal whose peak value is changed according to the level of the input drive control signal Vc is output. Has become.

The PWM conversion circuit 3 is a known circuit that linearly converts the drive waveform signal into a PWM drive signal having a duty ratio according to the level (see FIG. 8), and is connected to the drive circuit 5.

That is, the PWM conversion circuit 3 has a function of linearly performing PWM modulation according to the level change of the drive waveform signal.

The drive circuit 5, for example, as shown in FIG.
For transistors Q1, Q3, and Q5 whose collectors are connected to the positive side of a power supply (not shown), their emitters are connected to the collectors of transistors Q2, Q4, and Q6, respectively, and the emitters of transistors Q2, Q4, and Q6 are connected to the power supply. , The connection point of the transistors Q1 and Q2 is set at the beginning of winding of the U-phase drive coil La, the connection point of the transistors Q3 and Q4 is set at the start of winding of the V-phase drive coil Lb, and the transistors Q5 and Q6 are connected. The connection point is connected to the beginning of winding of the W-phase drive coil Lc, and the transistors Q1 to Q6
Diodes D1, D2, D
3, D4, D5 and D6 are connected in parallel and in reverse from the emitter to the collector.

The drive circuit 5 receives the U signal from the PWM conversion circuit 3
The transistors Q1 to Q6 are selectively turned on / off by PWM driving signals (switching control signals) corresponding to the phases, the V phase and the W phase, and the drive current from the power supply is switched to the Y-connected drive coils La to Lc and energized. Has a function.

Returning to FIG. 1, the detector 7 is, for example, a sensor arranged near the driving coils La, Lb, Lc, detects the number of rotations or the rotation speed of the motor, and outputs an electric signal of a level corresponding to the rotation number or the rotation speed. And a limiter circuit for outputting a drive control signal Vc having a level such that a deviation between the detection signal level and a predetermined reference rotation speed (reference rotation speed) is reduced. 9 is connected.

The limiter circuit 9 limits the level of the drive control signal Vc input from the detector 7, and limits the voltage level corresponding to the duty ratio 100% of the PWM drive signal to be converted in the PWM conversion circuit 3. Level and is connected to the drive waveform generation circuit 1. FIG. 3 shows a variable characteristic of the drive control signal Vc output from the limiter circuit 9.

As shown in FIG. 4, for example, the limiter circuit 9 includes a resistor R inserted in series with an input line of a drive control signal Vc, and a parallel and reverse connection between an output terminal of the resistor R and a common line. And is connected to the drive waveform generation circuit 1.

The constant voltage diode d has a zener (breakdown) voltage of which the duty ratio of the PWM drive signal is 100.
The element corresponding to the% equivalent level, that is, the above-mentioned limit level is selected.

In such a PWM drive control device for a motor, when the drive waveform generation circuit 1 generates and outputs U-phase, V-phase and W-phase drive waveform signals which are each shifted by 120 °, the Y-connected motor Drive coils La, Lb, Lc
, Three-phase drive currents of the U-V phase, the V-W phase and the W-U phase flow, and a rotor (not shown) rotates.

At this time, a PWM drive signal having a variable duty ratio is output from the PWM conversion circuit 3 in accordance with the level of the drive control signal Vc input from the detector 7, and the duty ratio is changed by the drive circuit 5. The rotor is variably controlled by applying the corresponding drive current.

At this time, when the level of the drive control signal Vc exceeds the limit level and increases, the level is fixed to the limit level by the limiter circuit 9, and as shown in FIG. Is output from the drive waveform generation circuit 1, and a PWM drive signal that does not exceed the duty ratio of 100% is output from the PWM conversion circuit 3, whereby the rotation of the rotor is controlled.

FIG. 5 shows a U-phase drive waveform signal, but the same applies to V-phase and W-phase drive waveform signals, although not shown.

As described above, in the motor PWM drive control device according to the present invention, the motor drive coils La, Lb, Lc
A drive waveform signal which is a source of U-phase, V-phase and W-phase drive currents to be supplied to the drive waveform generator 1 is variably generated based on the drive control signal level, and the pulse width is changed according to each drive waveform signal level. The PWM drive signal is converted by the PWM conversion circuit 3, the drive circuit 5 switches the drive current to the drive coils La, Lb, and Lc based on the PWM drive signal and energizes the drive coil, and the drive control signal level is changed to the PWM drive signal. When the drive control signal level exceeds the limit level corresponding to the signal duty of 100%, the limit circuit 9 fixes the drive control signal level to the limit level and outputs the drive control signal level to the drive waveform generation circuit 1. Is added, the drive waveform signal generated by the drive waveform generation circuit 1 and the PWM drive signal converted by the PWM conversion circuit 3 It will not sum.

Therefore, even if the level of the drive control signal increases, the drive current flowing through the drive coils La, Lb, Lc is hardly distorted, and the noise, vibration, and uneven rotation of the motor can be suppressed.

Further, since a constant voltage diode d is used as the limiter circuit 9 and the drive control signal level is limited by the Zener voltage of the constant voltage diode d, if a diode d having appropriate characteristics is selected, a diode such as a diode can be used. The drive control signal level can be suppressed only by using extremely small and inexpensive electronic components, and the configuration is simple and inexpensive, and the assembly is easy.

In the above-described embodiment, the zener voltage of the constant voltage diode d is changed to the duty 1 of the PWM drive signal.
Although the level is selected to be equivalent to 00%, in the present invention, the PWM conversion circuit 3 may be formed so that the level corresponding to the zener voltage of the constant voltage diode d is converted to a PWM drive signal having a duty equivalent to 100%. It is possible.

Further, in the above-described configuration, the level of the drive control signal based on the detection signal from the detector 7 is limited by the limiter circuit 9, but the limiter circuit 9 limits the drive control signal input from the outside to drive the drive waveform. Generation circuit 1
It is also possible to output the data to

In the above-described PWM drive control device for the motor, the drive waveform generation circuit 1 generates and outputs three U-phase, V-phase and W-phase drive waveform signals which are shifted by 120 ° from each other. From the above, the configuration for converting to a three-phase PWM drive signal according to the description has been described.

However, in the present invention, a configuration is also possible in which the driving waveform generating circuit 1 outputs a single-phase driving waveform signal and converts it into a three-phase PWM driving signal or driving current in the PWM conversion circuit 3 or the driving circuit 5. It is.

[0040]

The PW according to the present invention as described above
An M drive control device, a drive waveform generating circuit that variably generates a drive waveform signal according to a level change of a drive control signal that controls the driving force of a motor, and converts the drive waveform signal level into a PWM drive signal corresponding to the drive waveform signal level A PWM conversion circuit, a drive circuit for switching and supplying a three-phase drive current to a drive coil of a motor based on the PWM drive signal, and a drive control signal when the drive control signal level exceeds a level corresponding to a duty of 100% of the PWM drive signal. Set signal level to Duty 1
And a limiter circuit for limiting the drive waveform signal to a level equivalent to 00% and outputting the drive waveform signal to the drive waveform generation circuit.
The M drive signal is no longer saturated, the distortion of the drive current flowing through the drive coil is suppressed, and noise, vibration, and uneven rotation are less likely to occur. In the configuration in which the limiter circuit is formed so that the drive control signal is limited by a constant voltage diode, if a diode having appropriate characteristics is selected, the drive control signal level can be reduced only by using extremely small and inexpensive electronic components such as a diode. Can be suppressed, the configuration is simple and inexpensive, and it is easy to assemble.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a motor PWM drive control device according to the present invention.

FIG. 2 is a circuit diagram illustrating an example of a drive circuit and a drive coil of FIG. 1;

FIG. 3 is a diagram illustrating characteristics of the limiter circuit of FIG. 1;

FIG. 4 is a circuit diagram showing an example according to the limiter circuit of FIG. 1;

FIG. 5 is a waveform diagram illustrating an operation of the PWM drive control device of FIG. 1;

FIG. 6 is a block diagram showing a conventional PWM drive control device for a motor.

FIG. 7 is a waveform chart for explaining the operation of the PWM drive control device of FIG. 6;

FIG. 8 is a waveform chart illustrating an operation of the PWM drive control device of FIG. 6;

FIG. 9 is a waveform diagram illustrating an operation of the PWM drive control device of FIG. 6;

[Explanation of symbols]

 Reference Signs List 1 drive waveform generation circuit 3 PWM conversion circuit 5 drive circuit 7 detector 9 limiter circuit D1, D2, D3, D4, D5, D6 diode d constant voltage diode La, Lb, Lc drive coil Q1, Q2, Q3, Q4, Q5 , Q6 transistor R resistance

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C480 CA49 EA09 EA28 5H560 AA10 BB04 BB07 DB00 EB01 EC01 RR01 SS01 TT20 UA02 XA04 XA10 XA12

Claims (2)

[Claims] 1. A drive waveform generating circuit for variably generating and outputting a drive waveform signal corresponding to a level change of a drive control signal for controlling a driving force of a motor, and a PWM converting the drive waveform signal level into a pulse width.
A PWM conversion circuit that outputs a drive signal; a drive circuit that switches and drives a three-phase drive current to a drive coil of the motor based on the PWM drive signal to rotate the drive coil; and that the drive control signal level is the duty of the PWM drive signal. And a limiter circuit for limiting the drive control signal level to a level equivalent to 100% duty and outputting the drive control signal level to the drive waveform generation circuit when the level exceeds the 100% equivalent level. 2. The PWM drive control device for a motor according to claim 1, wherein the limiter circuit is formed to limit the drive control signal by a constant voltage diode.