JP3686992B2 - PWM motor drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a PWM motor driving apparatus that drives a brushless DC motor such as a VTR capstan motor while controlling the number of rotations by a PWM method.
[0002]
[Prior art]
A configuration example of the output stage of the motor driving device is shown in FIG. In the figure, T _UU , T _VU , T _WU , T _UL , T _VL , and T _WL are NPN type power transistors. L _U , L _V , and L _W are U-phase, V-phase, and W-phase coils of the motor, respectively, and are Y-connected. Transistor T _UU, T _VU, the collector of T _WU are applied drive voltage V _M of the motor is, the emitter of the transistor T _UL, T _VL, T _WL is connected to the ground. The coil L _U collector and the motor of the U-phase of the emitter and the transistor T _UL transistor T _UU, and the collector of the emitter and the transistor T _VL of the transistor T _VU is the coil L _V of the V-phase of the motor, the transistor T _WU The emitter and the collector of the transistor T _WL are connected to the W phase coil L _W of the motor, respectively.
[0003]
For example, as indicated by an arrow Y ₁ in FIG. 7, when the current flows from the coil L _U of the motor of the U-phase to the coil L _V of the V-phase, makes ON the upper output transistor T _UU and lower output transistor T _VL However, in the PWM drive system, one or both of these transistors are switched ON / OFF. The amount of electric power supplied to the motor, that is, the rotational speed of the motor is controlled by the ON / OFF duty ratio.
[0004]
[Problems to be solved by the invention]
Here, in the PWM drive method, since each coil of the motor is driven with pulses as described above, the rotation efficiency of the motor is good, but on the other hand, a sine wave can be obtained as the waveform of the current flowing through each coil of the motor. The motor could not be rotated smoothly.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a PWM motor driving apparatus that further reduces the rotational ripple of a motor.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, in a PWM motor driving apparatus that drives each phase of a motor with a pulse and controls the amount of power supplied to the motor by the duty ratio of this pulse, a signal indicating the rotational position of the motor Is provided with a signal generating means for generating a ripple cancel signal that is a triangular wave signal that is maximized at a timing when the torque is minimized, and a signal corresponding to an error between the actual rotational speed of the motor and the set rotational speed, and The duty ratio of the pulse is controlled by a signal obtained by adding the ripple cancel signal.
[0007]
With this configuration, since the duty ratio of the PWM signal is controlled in accordance with the triangular wave signal that is maximized at the timing when the torque is minimized, it is possible to flow more current at a timing when the torque is weak.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a PWM motor driving apparatus according to an embodiment of the present invention. Hall signals H1, H2, and H3 respectively output from Hall elements HU, HV, and HW attached to the periphery of the rotor, which is a rotating portion of the motor, are amplified by the Hall amplifier 1 to become signals A1, A2, and A3. Thereafter, it is input to the three-phase synthesis circuit 2. The three hall signals H1, H2, and H3 indicate the rotational position of the motor.
[0009]
The output amplifier 3 includes NPN-type power transistors T _UU , T _VU , T _WU , T _UL , T _VL , and T _WL . The upper output transistor T _UU, T _VU, and the collector of T _WU and driving voltage V _M of the motor is applied, the lower the output transistor T _UL, T _VL, the emitter of T _WL is via a common resistor R Connected to ground. The emitter of the upper output transistor _{TUU and} the collector of the lower output transistor _TUL are the U phase coil L _U of the motor, and the emitter of the upper output transistor T _{VU and} the collector of the lower output transistor T _VL are the V phase of the motor. the coil L _V of the coil L _W of the collector of the upper output transistor T _WU of the emitter and the lower output transistor T _WL is W-phase are connected. Currents UU, VU, WU, UL, VL, WL output from the three-phase synthesis circuit 2 are supplied to the bases of the output transistors T _UU , T _VU , T _WU , T _UL , T _VL , T _WL , respectively.
[0010]
The reference voltage V _REF is input to the inverting input terminal (−) of the control amplifier 4, while the torque control signal T _CTL that is a voltage signal is input to the non-inverting input terminal (+). The control amplifier 4 outputs a current I _CTL corresponding to the voltage difference between the voltage input to the inverting input terminal (−) and the voltage input to the non-inverting input terminal (+). Specifically, the current I _CTL output from the control amplifier 4 increases as the voltage of the torque control signal T _CTL becomes higher than the reference voltage V _REF . The current supply circuit 11 supplies the current I _CTL output from the control amplifier 4 to the resistor 5 and the ripple cancel circuit 13.
[0011]
The torque control signal T _CTL is a signal output from a circuit (not shown) that detects the number of rotations of the motor and compares the detected number of rotations with the set number of rotations. The lower the rotation speed is, the higher the rotation speed is. The higher the rotation speed is, the lower the rotation speed. Therefore, the current I _CTL output from the control amplifier 4 is a signal corresponding to an error between the actual rotational speed of the motor and the set rotational speed.
[0012]
At the non-inverting input terminal (+) of the current feedback amplifier 6, a current obtained by adding a current I _CTL output from the control amplifier 4 and a current I _CAN output from a ripple cancel circuit 13 described later is converted to a voltage by the resistor 5. On the other hand, the voltage at both ends of the resistor R, that is, the voltage corresponding to the drive current of the motor is input to the inverting input terminal (−).
[0013]
The current feedback amplifier 6 outputs a current I _FS corresponding to the voltage difference between the voltage input to the non-inverting input terminal (+) and the voltage input to the inverting input terminal (−). Specifically, the larger the current obtained by adding the current I _CAN output from the current I _CTL and ripple cancellation circuit 13 which is output from the control amplifier 4, also, as the driving current of the motor is reduced, current feedback amplifier 6 The current I _FS output from is increased.
[0014]
The current I _FS output from the current feedback amplifier 6 is converted into a voltage by the resistor 8 and input to the non-inverting input terminal (+) of the PWM comparator 9, while the triangular wave is generated at the inverting input terminal (−). A high-frequency triangular wave output from the circuit 10 is input.
[0015]
From the above, the PWM comparator 7 outputs a high-frequency binary signal (hereinafter referred to as “PWM signal”) S _PWM . The high-level duty ratio for one cycle of the PWM signal S _PWM is the torque control signal. In addition to the T _CTL and the motor drive current, control is performed according to the current I _CAN output from the ripple cancel circuit 13. Specifically, the PWM signal S _CTL increases as the voltage value of the torque control signal T _CTL increases, the current value of the current I _CAN output from the ripple cancel circuit 13 increases, and the motor drive current decreases. _The high level duty ratio for one _PWM period is increased.
[0016]
As shown in FIG. 3, sinusoidal Hall signals H1, H2, and H3, which are output from the Hall elements HU, HV, and HW and are shifted in phase by 120 ° from each other, have phases of 30 by the Hall amplifier 1, respectively. After being advanced, it is amplified to become signals A1, A2, and A3.
[0017]
The internal configuration of the three-phase synthesis circuit 2 is shown in FIG. As shown in FIG. 3, the logarithmic conversion circuit 21 extracts the positive portions of the signals A1, A2, and A3, and obtains the switching signals B1, B2, and B3, and the negative values of the signals A1, A2, and A3, respectively. Switching signals B4, B5, and B6 obtained by extracting the portions are generated.
[0018]
Further, as shown in FIG. 3, the logarithmic conversion circuit 21 generates absolute value signals Z1, Z2, and Z3 obtained by taking the absolute values of the signals A1, A2, and A3. These absolute value signals Z1, Z2, and Z3 are input to the ripple cancel circuit 13.
[0019]
The configuration of the three differential circuit 22 is shown in FIG. PNP transistors 2201 and 2202 constitute a current mirror circuit. A constant current flowing into the constant current circuit 2215 having one end connected to the ground flows through the collector of the transistor 2201 on the input side. On the other hand, the collector of the NPN transistor 2203 is connected to the collector of the transistor 2202 on the output side.
[0020]
NPN transistors 2203 and 2204 constitute a current mirror circuit. As described above, the collector of the transistor 2202 is connected to the collector of the transistor 2203. The collector of the transistor 2204 is connected to the emitters of NPN transistors 2205, 2206, and 2207.
[0021]
NPN transistors 2208 and 2209 constitute a current mirror circuit. A constant current flowing out from a constant current circuit 2216 having one end connected to the power supply flows through the collector of the transistor 2208 on the input side. On the other hand, the collector of the output side transistor 2209 is connected to the collector of a PNP transistor 2210.
[0022]
PNP transistors 2210 and 2211 form a current mirror circuit. As described above, the collector of the transistor 2209 is connected to the collector of the transistor 2210 on the input side. The emitters of the PNP transistors 2212, 2213, and 2214 are connected to the collector of the output-side transistor 2211.
[0023]
The base of the transistor 2205 has a switching signal B1, the base of the transistor 2206 has a switching signal B2, the base of the transistor 2207 has a switching signal B3, the base of the transistor 2212 has a switching signal B4, and the base of the transistor 2213 has The switching signal B5 is input to the base of the transistor 2214, and the switching signal B6 is input thereto.
[0024]
Then, currents I 1, I 2, I 3, I 4, I 5, and I 6 flowing through the collectors of the transistors 2205, 2212, 2206, 2213, 2207, and 2214 are output from the three differential circuit 22. The currents I1, I2, I3, I4, I5, and I6 output from the three differential circuit 22 are amplified by the preamplifier 23 to become currents UU, UL, VU, VL, WU, and WL, and then output amplifiers to be described later Three output transistors T _UU , T _UL , T _VU , T _VL , T _WU , T _WL are input to the bases.
[0025]
Of the current output from the three differential circuit 22, currents I1, I3, and I5 related to the current input to the base of the upper output transistor are input to the preamplifier 23 via the switches 24, 25, and 26, respectively. . Each switch 24, 25 and 26 is adapted to OFF when ON, a low level when the PWM signal S _PWM is high. Therefore, ON / OFF of the upper output transistor of the output amplifier 3 is switched at the same frequency and the same duty ratio as the PWM signal S _PWM .
[0026]
With the above configuration, the driven coil is switched at an appropriate timing according to the rotational position of the motor, and the motor rotates. As the duty ratio of the high level with respect to the low level of the PWM signal S _PWM increases, the time during which the upper output transistor of the output amplifier 3 is turned on becomes longer, so that the amount of power supplied to the coil (in other words, the coil drive current) ) Increases and the motor load is constant, the motor speed increases.
[0027]
The internal configuration of the torque ripple cancel circuit 13 is shown in FIG. NPN transistors 1301 and 1302 form a current mirror circuit. The emitters of the transistors 1301 and 1302 are grounded through resistors 1303 and 1304, respectively. The output current I _CTL of the control amplifier 4 is input to the collector of the transistor 1301 on the input side. The collector of the PNP transistor 1305 is connected to the collector of the transistor 1302 on the output side. Note that a terminal is provided at a connection point between the emitter of the transistor 1302 and the resistor 1304 so that the resistor can be connected to adjust the ripple cancellation rate.
[0028]
The PNP type transistors 1305 and 1306 constitute a current mirror circuit. The emitters of the transistors 1305 and 1306 are connected to the power supply voltage V _CC via resistors 1307 and 1308, respectively. The collector of the transistor 1305 on the input side is connected to the collector of the transistor 1302 as described above. The emitters of the PNP transistors 1307, 1308, 1309, and 1310 are commonly connected to the collector of the output-side transistor 1306.
[0029]
Absolute value signals Z1, Z2, and Z3 generated by the three-phase synthesis circuit 2 are input to the bases of the transistors 1308, 1309, and 1310, respectively. One ends of resistors 1312, 1313, and 1314 are connected to the bases of the transistors 1308, 1309, and 1310, respectively, and the other ends of these resistors 1312, 1313, and 1314 are connected in common. The base of the transistor 1307 is connected to a common connection point of the resistors 1312, 1313, and 1314 through the resistor 1311. The common connection point of the resistors 1311, 1312, 1313, and 1314 is biased.
[0030]
NPN transistors 1315 and 1316 constitute a current mirror circuit. The emitters of the transistors 1315 and 1316 are grounded through resistors 1317 and 1318, respectively. The collectors of the transistors 1308, 1309, and 1310 are commonly connected to the collector of the transistor 1315 on the input side. The collector of the transistor 1317 is connected to the collector of the transistor 1316 on the output side. Then, a difference current I _CAN between the collector current of the transistor 1307 and the collector current of the transistor 1316 is output from the ripple cancel circuit 13 and supplied to the resistor 5.
[0031]
Due to the configuration of the ripple cancel circuit 13, the current I _CAN output from the ripple cancel circuit 13 has absolute value signals Z1 and Z2 generated by the three-phase synthesis circuit 2 as shown in the timing chart of FIG. , The waveform is similar to the waveform taken by the minimum value of Z3. As a result, the current I _CAN output from the ripple cancel circuit 13 becomes a triangular wave signal that becomes maximum at the timing when the amplitude of each Hall signal H1, H2, and H3 becomes 0, that is, when the torque becomes minimum. .
[0032]
Therefore, when the current I _CAN output from the ripple cancel circuit 13 increases, the high level duty ratio for one cycle of the PWM signal S _PWM increases. become longer. As a result, the weak torque portion can be canceled, and the motor can be rotated more smoothly.
[0033]
When switching ON / OFF of the upper output transistor, it is desirable that the resistor R for detecting the drive current of the motor is connected to the ground GND side as in the above embodiment. Because, as shown in FIG. 7, for example, in case of switching the ON / OFF of the upper output transistor T _UU, even after the upper output transistor T _UU is switched to OFF from ON, the counter electromotive voltage of the coil L _U as shown by the arrow Y _2, the current flows through the diode D parasitic to the lower output transistor T _UL, when connecting the resistor R to the driving voltage V _M side of the motor, detecting the current Because you can't.
[0034]
For the same reason, when switching the ON / OFF of the lower output transistor, it is better to connect a resistor for detecting the motor drive current to the motor drive voltage side. Since it can detect more correctly, controllability improves.
[0035]
Moreover, in the said embodiment, although the drive current of a motor is fed back, this does not need to be performed. When feedback of the motor drive current is not performed, a current obtained by adding the output current I _CTL of the control amplifier 4 and the output current I _CAN of the ripple cancel circuit 13 is converted into a voltage by the resistor 5 and the PWM comparator 9 is turned off. What is necessary is just to make it input into an inverting input terminal (+). However, controllability is improved by feeding back the motor drive current.
[0036]
【The invention's effect】
As described above, according to the PWM motor drive device of the present invention, the duty ratio of the PWM signal is controlled according to the triangular wave signal that is maximized at the timing at which the torque is minimized. More current can be passed. Thereby, a motor can be rotated more smoothly.
[Brief description of the drawings]
FIG. 1 is a block diagram of a PWM motor driving apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing an internal configuration of a three-phase synthesis circuit.
FIG. 3 is a timing chart of each signal.
FIG. 4 is a circuit diagram of a three-differential circuit.
FIG. 5 is a circuit diagram of a ripple cancel circuit.
FIG. 6 is a timing chart of each signal.
FIG. 7 is a circuit diagram of an output stage of the motor driving device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hall amplifier 2 Three-phase synthetic circuit 3 Output amplifier 4 Control amplifier 5 Resistance 6 Current feedback amplifier 8 Resistance 9 PWM comparator 10 Triangular wave generation circuit 11 Current supply circuit 13 Ripple cancellation circuit

Claims (3)

In the PWM motor drive device that drives each phase of the motor with a pulse and controls the amount of power supplied to each phase of the motor by the duty ratio of this pulse,
It is generated based on a signal indicating the position of each phase when the motor rotates, and a ripple cancellation signal having a triangular waveform having a maximum value at the timing when the torque of each phase is minimum, and the actual motor A PWM characterized in that an input signal obtained by adding a torque control signal corresponding to an error between the rotational speed and a set rotational speed is input to a PWM comparator, and the duty ratio is controlled by the output of the PWM comparator. Motor drive device. In the PWM motor drive device that drives each phase of the motor with a pulse and controls the amount of power supplied to each phase of the motor by the duty ratio of this pulse,
Based on a signal indicating the rotational position of each phase of the motor, means for generating a triangular wave ripple cancel signal having a maximum value at a timing at which the torque of each phase is minimum,
A signal obtained by adding a torque control signal corresponding to an error between the actual rotational speed of the motor and the set rotational speed and the ripple cancellation signal is input as an input signal, and PWM having a duty ratio based on the level of the input signal A PWM comparator that outputs a signal;
An upper output transistor connected between the high voltage side of the power supply and the motor;
A lower output transistor connected between the low voltage side of the power supply and the motor;
Switching means for switching ON / OFF of the upper output transistor and the side output transistor according to a signal indicating a rotational position of each phase of the motor;
A PWM motor driving apparatus that controls the amount of electric power by controlling the duty ratio of ON / OFF of one or both of the upper output transistor and the lower output transistor with the PWM signal. 3. The PWM motor driving apparatus according to claim 1, wherein a level of the ripple cancel signal changes according to a level of the torque control signal. 4.

Images