JP2006271108A - Semiconductor device for inverter control, and inverter controller for motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter controller for motor drive which is capable of high quality drive from a low-speed range to a high-speed range by accurately detecting a phase current, in inexpensive constitution. <P>SOLUTION: This inverter controller can materialize high quality motor drive by accurately detecting the current of each phase of a motor, without incurring the increase, etc. of a magnetic sound, with a semiconductor device for inverter control which is equipped with a PWM signal generator having a plurality of counters (23u-23w) for PWM signal generation and registers 27u for duty setting being provided for each of the above plurality of counters (23u-23w) and converts an inputted analog signal into a digital signal in case that the count values of the above plurality of counters (23u-23w) are the same as predetermined set values. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inverter control semiconductor device equipped with an AD converter.

  Conventionally, an inverter control microcomputer is provided with an AD converter, a PWM signal generation unit, and the like. The PWM signal generation unit 9 generally generates six PWM (Pulse Width Modulation) signals. These signals are composed of three PWM signals of U phase, V phase, and W phase having different duties, and three signals of X phase, Y phase, and Z phase that are inverted signals thereof.

  Although various types of PWM signal generation units are known, they are generally composed of a counter and a comparator (comparator). An example of this is shown in FIG. In the example of the figure, a counter 23, a carrier setting register 24 for storing the maximum count value (carrier set value) of the counter 23, and a comparator 25 for comparing the current count value of the counter 23 with the carrier set value are provided. When the current count value of the counter 23 matches the carrier set value or the zero value, the comparator 25 inverts the counter 23 from the up count to the down count or vice versa.

  Furthermore, the PWM signal generation unit 9 of FIG. 10 includes phase circuits 26u, 26v, and 26w. In the case of the U phase, the duty setting register 27u that stores the duty setting value and the count value of the counter 23 are stored therein. A comparator 28u that compares the duty setting value of the duty setting register 27u and a flip-flop that receives a signal from the comparator 28u and inverts the U-phase and X-phase PWM signals when the count value of the counter 23 matches the duty setting value. Circuit 29u.

  The inverter control microcomputer 1 provided with such a PWM signal generation unit 9 is used for controlling an inverter device for driving an AC motor, as shown in FIG. 11, for example. A motor drive inverter control apparatus that performs variable speed drive of an AC motor will be described with reference to FIG.

  FIG. 11 shows an inverter control device for driving a motor using a conventional pulse width modulation method. The inverter 2 generates and outputs a drive voltage to be supplied to the DC power source 1 and the brushless motor 3, and the control unit 6 that controls the inverter 2 is provided. Have.

  The DC current detector 11 detects a DC current flowing through the inverter bus, and the phase current conversion unit 7 flows to the motor 3 from the detected DC current and each phase duty of the PWM signal output from the PWM signal generation unit 9. U-phase motor current Iu, V-phase motor current Iv, and W-phase motor current Iw are detected. Based on the detected motor currents Iu, Iv, and Iw and a speed command ω * given from the outside, a signal for controlling the inverter 2 is created by the PWM signal generation unit 9.

  FIG. 12 shows the PWM signal (only for the upper arm of the inverter 2) output from the PWM signal generator 9, the motor applied voltage generated thereby, and the current of each phase flowing through the motor.

FIG. 13 shows details of the period T in FIG. Upper arm U phase switching element control signal, upper arm V phase switching element control signal, upper arm W phase switching element control signal, lower arm U phase switching element control signal, lower arm V phase switching element control signal, lower arm W The phase switching element control signal and the direct current flowing through the inverter bus. Two phase phases of the motor appear in the direct current, and the phase current conversion unit 7 converts the motor currents Iu, Iv, and Iw using the duty information of the PWM signal output from the PWM signal generation unit 9.

A method for converting the inverter bus current into motor currents Iu, Iv, and Iw is described in detail in Patent Document 1 below.
Japanese Patent No. 2712470

  However, when the motor applied voltage of each phase is equal or very close, the duty of the PWM signal output from the PWM signal generator 9 is almost equal, and only the motor phase current for one phase appears in the inverter bus current. Become. FIG. 13 shows an ideal waveform, so that the inverter bus current rises instantaneously, but actually there is a rise delay time of the current, and in some cases an overshoot occurs in the inverter bus current. There is. For this reason, when the duty difference of the PWM signal output from the PWM signal generation unit 9 is small, it is difficult to sample an accurate motor phase current.

  Also, when switching the upper and lower arm switching of each phase on / off, a dead time is provided to prevent short circuit of the inverter upper and lower arms due to the delay in operation of the switching element. During this period, the current flowing through the inverter bus becomes indefinite and the phase current The conversion of the motor phase current in the conversion unit 7 becomes impossible.

  As described above, when the current sampling period becomes short due to the actual current rise delay time, inverter bus current overshoot, dead time period, and the like, current sampling becomes difficult.

  For this reason, in order to ensure a sufficient sampling period, it is necessary to lower the carrier frequency. However, if the carrier frequency is lowered, there is a problem that magnetic sounds from the motor and the load increase.

  The present invention solves such a conventional problem, and provides an inverter control device for driving a motor capable of accurately detecting the current of each phase of the motor without causing an increase in magnetic sound, etc., and capable of high-quality driving. The purpose is to provide.

  In order to solve the above problems, the present invention includes a PWM signal generation unit having a plurality of counters for generating a PWM signal and a duty setting register provided in each of the plurality of counters, and the count values of the plurality of counters Is the same as the preset value, the inverter control semiconductor device is configured to convert the input analog signal into a digital signal, and it detects the current of each phase of the motor without increasing the magnetic noise. Can be performed accurately and high-quality motor drive can be realized.

  According to the present invention, it is possible to provide an inverter control device for driving a motor capable of accurately detecting the current of each phase of the motor without causing an increase in magnetic sound, etc., and capable of high-quality driving.

  A first invention includes a PWM signal generation unit having a plurality of counters for generating a PWM signal and a duty setting register provided in each of the plurality of counters, and the count values of the plurality of counters are respectively set in advance. In the case where the set value is the same, the inverter control semiconductor device configured to convert the input analog signal into a digital signal can detect the phase current of the motor with high accuracy.

  In the second invention, particularly in the inverter control semiconductor device according to the first invention, when the set values set in the respective registers are substantially the same, the counter maintains a predetermined time interval and starts counting. It is a feature, and it is possible to eliminate a period in which the phase current of the motor cannot be detected.

  The third invention is an inverter control device for driving a motor that uses the semiconductor device for inverter control of the first or second invention, and has high control stability by executing a motor drive algorithm at a constant cycle. A control device can be realized.

  According to a fourth aspect of the invention, in particular, in the motor drive inverter control apparatus of the third aspect of the invention, based on a direct current detector that detects a direct current flowing through the inverter circuit, and a direct current detection value of the direct current detector, It is provided with a phase current calculation means that reproduces the current of each phase of the motor, and it is possible to realize a motor drive inverter control device having high control stability while being small and low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of an inverter control apparatus for driving a motor according to the present invention. The motor drive inverter control device includes a DC power source 1, an inverter 2 that generates and outputs a drive voltage to be supplied to the brushless motor 3, and a control unit 6 that controls the inverter 2.

  The brushless motor 3 includes a stator 4 to which three-phase windings 4u, 4v, 4w Y-connected around a neutral point are attached, and a rotor 5 to which a magnet is attached. The U-phase terminal 8u is connected to the non-connected end of the U-phase winding 4u, the V-phase terminal 8v is connected to the non-connected end of the V-phase winding 4v, and the W-phase terminal 8w is connected to the non-connected end of the W-phase winding 4w. Yes.

  The inverter 2 has a half-bridge circuit composed of a pair of switching elements for three phases for U phase, V phase, and W phase. The pair of switching elements of the half-bridge circuit are connected in series between the high-voltage side end and the low-voltage side end of the DC power supply 1, and a DC voltage output from the DC power supply 1 is applied to the half-bridge circuit. The U-phase half-bridge circuit includes a switching element 12u on the high voltage side (upper arm) and a switching element 12x on the low voltage side (lower arm). The V-phase half-bridge circuit includes a high-voltage side switching element 12v and a low-voltage side switching element 12y. The W-phase half-bridge circuit includes a high-voltage side switching element 12w and a low-voltage side switching element 12z. In addition, free wheel diodes 14u, 14v, 14w, 14x, 14y, and 14z are connected in parallel with the switching elements.

  The terminals 8u, 8v, and 8w of the brushless motor 3 are connected to the interconnection point between the switching element 12u and the switching element 12x in the inverter 2, the interconnection point between the switching element 12v and the switching element 12y, and the interconnection point between the switching element 12w and the switching element 12z. Each is connected.

The DC voltage applied to the inverter 2 is converted into a three-phase AC voltage by the switching operation of the switching element in the inverter 2 described above, whereby the brushless motor 3 is driven. A DC current detector 11 is arranged on the bus of the inverter 2. The control unit 6 includes a PWM signal generation unit 9, a base driver 10, a phase current conversion unit 7, a phase estimation unit 17, and a rotor speed detection unit 18.

  The PWM signal generator 9 outputs the output voltage obtained by calculation from the error between the current speed and the target speed in order to realize the target speed given from the outside, so that each switching element 12u, 12v, PWM signals for driving are generated. The generated PWM signal is converted by the base driver 10 into a drive signal for electrically driving the switching element. Each switching element 12u, 12v, 12w, 12x, 12y, 12z operates according to the drive signal.

  The control unit 6 is realized by an inverter control semiconductor device (microcomputer), and the PWM signal generation unit 9 includes a counter, a comparator (comparator), and the like. The phase current converter 7 observes a current (hereinafter referred to as “inverter bus current”) flowing through the DC current detector 11 and converts the inverter bus current into a phase current of the brushless motor 3. The phase current converter 7 actually detects the current only for a predetermined period from when the inverter bus current changes.

  The phase estimation unit 17 outputs the phase current of the brushless motor 3 converted by the phase current conversion unit 7, the output voltage calculated by the PWM signal generation unit 9, and the inverter 2 detected by the inverter input voltage detection unit 16. The phase of the brushless motor 3 is estimated based on the information on the applied voltage. Further, the rotor speed estimation unit 18 estimates the speed of the brushless motor 3 from the estimated phase. Based on the information on the estimated rotor magnetic pole position, the PWM signal generator 9 generates a PWM signal for driving the brushless motor 3. At that time, the PWM signal generation unit 9 controls the PWM signal so that the rotor speed becomes the target speed based on the deviation information between the estimated speed of the rotor 5 and the target speed given from the outside.

  In order to realize the target speed ω *, the PWM signal generation unit 9 calculates a voltage V * to be output based on a difference Δω between the target speed ω * and the estimated speed ωm using a PI calculation or the like. A voltage V * s (s: phase u / v / w) to be output to each phase is obtained from the voltage value V *.

  Furthermore, the PWM signals of the switching elements 12u, 12v, 12w, 12x, 12y, and 12z for outputting the obtained voltage V * s (s: phase u / v / w) are output to the base driver 10. Each of the switching elements 12u, 12v, 12w, 12x, 12y, and 12z is driven in accordance with the PWM signal, and generates a sine wave AC.

  Thus, in the present embodiment, the sine wave drive of the brushless motor 3 is realized by flowing a sine wave phase current.

  Here, how the phase current of the brushless motor 3 appears in the current flowing through the inverter bus will be described with reference to FIGS.

FIG. 2 is a diagram showing the state of the phase current flowing in each phase winding of the brushless motor 3 and the direction of the current flowing in each phase winding in each section of the electrical angle every 60 °. Referring to FIG. 2, in the section where the electrical angle is 0 to 60 °, the U-phase winding 4u and the W-phase winding 4w are neutral from the unconnected end to the neutral point, and the V-phase winding 4v is neutral. Current flows from the point toward the non-connected end (see FIG. 2B). Further, in the section of electrical angle of 60 to 120 °, the U-phase winding 4u is directed from the non-connection end toward the neutral point, and the V-phase winding 4v and the W-phase winding 4w are not connected from the neutral point. A current flows toward the end (see FIG. 2C). 2 (d) to 2 (g) show how the state of the phase current flowing through the windings of each phase changes every electrical angle of 60 °.

  For example, consider a case in which the PWM signal corresponding to the half carrier period generated by the PWM signal generation unit 9 changes as shown in FIG. 3 when the electrical angle is 30 ° in FIG. In FIG. 3, the signal “U” indicates the upper arm switching element 12u, the signal “V” indicates the upper arm switching element 12v, the signal “W” indicates the upper arm switching element 12w, and the signal “X” indicates the lower arm. The switching element 12x, the signal “Y” indicates the lower arm switching element 12y, and the signal “Z” indicates the signal for operating the lower arm switching element 12z. These signals operate active high. In this case, the current does not appear on the inverter bus at timing 1 as shown in FIG. 4A, and at timing 2 the current flowing in the W-phase winding 4w as shown in FIG. 4B (W-phase current). ) Appears, and at timing 3, a current (V-phase current) flowing through the V-phase winding 4v appears as shown in FIG. 4C.

  As another example, let us consider a case where the PWM signal having a half carrier period generated by the PWM signal generation unit 9 when the electrical angle is 30 ° in FIG. 2 changes as shown in FIG. In this case, as shown in FIG. 6 (a), no current appears on the inverter bus at timing 1, and as shown in FIG. 6 (b), current flowing in the U-phase winding 4u (U-phase current) at timing 2. As shown in FIG. 6C, a current flowing in the V-phase winding 4v appears at timing 3.

  As described above, it can be seen that the phase current of the brushless motor 3 corresponding to the state of the switching elements 12u, 12v, 12w, 12x, 12y, and 12z of the inverter 2 appears on the inverter bus. If the current for two phases can be determined at close timing within one carrier period as described above, it is clear that the currents iu, iv, and iw for the three phases can be obtained from the relationship of the following equations.

  That is, the case where any one of the upper arm switching elements is turned on as in timing 2 and the case where any two of the upper arm switching elements are turned on as in timing 3 are within one carrier cycle. If present, the motor phase current can be detected for each carrier cycle from the current flowing in the inverter bus, and fine motor drive control can be used for generating a PWM signal in the next carrier cycle.

  FIG. 7 shows a PWM signal (only for the upper arm of the inverter 2) output from the PWM signal generator 9, the motor applied voltage generated thereby, and the current of each phase flowing through the motor. Here, considering the period T in FIG. 7, the U-phase and W-phase motor applied voltages are very close during this period, and the U-phase duty of the PWM signal output by the PWM signal generation unit 9 The W-phase duty is also very close.

  Conventionally, in the period T in FIG. 7, there is no timing 2 in which any one of the upper arm switching elements is turned on, or it exists only in a very short time. From the current flowing through the inverter bus The motor phase current cannot be detected every carrier cycle, and fine motor drive control is impossible.

However, in the present invention, the PWM signal generator 9 is provided with three counters, counter U, counter V, and counter W, and the count start timing of the counter W is shifted by Td from the count start timing of other counters. .

  As shown in FIG. 8, the U-phase duty decision value and the W-phase duty decision value are the same by shifting the count start timing of the counter W by Td from the count start timing of other counters by the PWM signal generation unit 9. Even when the value is reached, only the U-phase upper arm switching element is turned on, or the period of timing 2 in which only the W-phase upper arm switching element is turned on can exist for Td. By securing the time required to detect the current flowing through the bus (specifically, the AD conversion time for a microcomputer or the like), the motor phase current can be detected for each carrier cycle from the current flowing through the inverter bus. Can be used for PWM signal generation in the next carrier cycle, and achieves fine motor drive control It was.

  As shown in FIG. 9, the microcomputer 1 for inverter control provided with the PWM signal generation unit 9 for realizing the operation shown in FIG. 8 includes three counters 23u, 23v, 23w, and the maximum count value ( Carrier setting register 24 for storing the carrier setting value) and a comparator 25 for comparing the current count value of the counter with the carrier setting value, and as shown in FIG. 8, the current values of the counters 23u, 23v, 23w When the count value coincides with the carrier set value or zero value, the comparator 25 inverts each counter 23u, 23v, 23w from up-count to down-count or vice versa.

  Furthermore, the PWM signal generation unit 9 of FIG. 9 is provided with phase circuits 26u, 26v, and 26w, and in the case of the U phase, the duty setting register 27u that stores the duty setting value and the count value of the counter 23u are stored therein. A comparator 28u that compares the duty setting value of the duty setting register 27u, and a flip-flop that receives a signal from the comparator 28u and inverts the U-phase and X-phase PWM signals when the count value of the counter 23u matches the duty setting value. Circuit 29u.

  According to the present embodiment, when it is necessary to detect the phase current flowing in the winding of each phase of the brushless motor 3 in order to establish the control loop in the control unit 6, it is impossible to detect the phase current. The sine wave drive can be realized with high accuracy by an inexpensive system configuration in which it is not necessary to provide two or more current detection means between the lines between the inverter and the motor. In addition, since phase current can be detected without lowering the carrier frequency, there is an effect that magnetic noise from the motor and load is not increased.

  The present invention described in the first embodiment can be applied to a motor drive inverter control device that drives a motor using an inverter circuit. For example, an air conditioner equipped with an inverter circuit, a refrigerator, an electric washing machine, an electric dryer, an electric vacuum cleaner, a blower, a heat pump water heater and the like. For any product, by reducing the size and weight of the motor drive inverter device, the degree of freedom in product design is improved, and an inexpensive product can be provided.

As described above, the inverter control device for motor driving according to the present invention includes a plurality of counters for generating a PWM signal, a PWM signal generating unit having a duty setting register for each counter, and a counter count value of a predetermined value. And an AD converter that converts an input analog signal into a digital signal, and particularly when there is no predetermined difference between the values set in the registers, the counter controls the inverter to start counting at an arbitrary time. Since the current of each phase of the motor can be reproduced regardless of what PWM signal is output and the reliability of the system can be improved, the compressor drive motor in the air conditioner etc. As in the case where a speed sensor such as a pulse generator cannot be used, Also the present invention in the case, which may comprise a speed sensor, such as can be applied.

The system block diagram of the inverter control apparatus for motor drive which shows the 1st Embodiment of this invention (A)-(f) The figure showing the example of the time change of the phase current state of the motor, and the state of the electric current in each phase winding of the motor in each section of an electrical angle The figure showing an example of the PWM signal in the same carrier cycle (A)-(c) The figure showing the electric current state which flows into a motor and an inverter at the time of the drive by the PWM signal in FIG. The figure showing the other example of the PWM signal in the same carrier cycle (A)-(c) The figure showing the electric current state which flows into a motor and an inverter at the time of the drive by the PWM signal in FIG. Waveform diagram showing the operation of the motor drive inverter controller The figure showing operation of the PWM signal generation part The figure which shows an example of the PWM signal generation part The figure which shows an example of the conventional PWM signal generation part Block diagram showing the configuration of the motor drive inverter control device Waveform diagram showing the operation of the motor drive inverter controller Operation waveform diagram of T section in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter 3 Brushless motor 7 Phase current conversion part 9 PWM signal generation part 11 DC current detector 16 Inverter input voltage detection part 17 Phase estimation part 18 Rotor speed estimation part 23u-23w Counter 24 Carrier setting register 25 Comparator 26u to 26w phase circuit 27u duty setting register 28u comparator 29u flip-flop circuit

Claims (4)

A plurality of counters for generating a PWM signal, and a PWM signal generating unit having a duty setting register provided in each of the plurality of counters, wherein the count values of the plurality of counters are the same as the preset set values, respectively. In this case, the inverter control semiconductor device is configured to convert an input analog signal into a digital signal. 2. The inverter control semiconductor device according to claim 1, wherein when the set values set in the respective registers are substantially the same, the counter maintains a predetermined time interval and starts counting. A motor drive inverter control device using the inverter control semiconductor device according to claim 1. 4. A DC current detector for detecting a DC current flowing in the inverter circuit, and phase current calculation means for reproducing the current of each phase of the motor based on a DC current detection value of the DC current detector. Motor drive inverter control device.

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