JP4788603B2 - Inverter device - Google Patents

Description

  The present invention relates to a phase current detection method for an inverter device that performs PWM modulation.

  Conventionally, as this type of phase current detection method, a method of detecting from a current of a DC power supply line is known (see, for example, Patent Document 1). This is only one current sensor, which is effective for circuit simplification and component saving.

  This circuit will be described below. FIG. 39 shows an electric circuit diagram. The control circuit 12 of the inverter device 23 controls the switching element 2 via the connection line 18 based on a rotation speed command signal (not shown) and the like, and converts the electric power of the battery 1 into direct current alternating current. Thereby, an alternating current is supplied to the stator winding 4 of the motor 11 and the magnet rotor 5 is driven. The diode 3 serves as a circulation route for the current flowing through the stator winding 4. For the switching element 2, the upper arm switching element is defined as U, V, W, and the lower arm switching element is defined as X, Y, Z. The value detected by the current sensor 6 is sent to the control circuit 12 and used for detecting the position of the magnet rotor 5. Furthermore, it is used for power consumption calculation, switching element 2 protection, and the like.

  FIG. 40 shows sinusoidal three-phase modulation waveforms with a maximum modulation of 50% for U phase terminal voltage 41, V phase terminal voltage 42, W phase terminal voltage 43, and neutral point voltage 29.

  FIG. 41 is an example of energization of the upper arm switching elements U, V, W and the lower arm switching elements X, Y, Z within one carrier (carrier cycle), and each switching element 2 is controlled from the control circuit 12. Indicates an ONOFF signal. In this case, energization is performed before and after the phase indicated by α in FIG. The phase with the maximum ON time of the upper arm switching element is the maximum energized phase (U phase in this case), the intermediate phase is the intermediate energized phase (in this case V phase), and the minimum phase is the minimum energized phase (in this case W phase) Define. The intermediate energized phase is also the second phase when the upper arm switching element is on.

  There are four types of energization periods: (a), (b), (c), and (d). Although details are omitted, the phase current that can be detected by the current sensor 6 in the ON and OFF states of the upper arm switching elements U, V, and W is specified. That is, when only one phase is ON, the current of the phase flows, and when the two phases are ON, the current of the remaining phase flows through the DC power supply line and can be detected by the current sensor 6. On the other hand, when all three phases are ON and when all three phases are OFF, current does not flow to the DC power supply line, and detection is impossible. Therefore, the detectable phase current can be known by confirming that the upper arm switching elements U, V, and W are ON. If phase currents for two phases are detected, the phase currents of the remaining phases can be calculated from the two current values by applying Kirchoff's current law at the neutral point of the stator winding 4.

  FIG. 42 shows changes in the current flowing through the DC power supply line in FIG. In the energization period (b), since only the upper arm switching element U is ON, the U-phase current iU becomes a direct current and can be detected by the current sensor 6. In the energization period (c), since the upper arm switching elements U and V are ON, the W-phase current iW becomes a direct current and can be detected by the current sensor 6.

The timing at which the current is detected by the current sensor 6 is detected when the current changes. That is, as shown in FIG. 43, the U-phase current iU is detected at a timing indicated by a white triangle, and the W-phase current iW is detected at a timing indicated by a black triangle. 43 shows the current in the first half of the carrier cycle in FIG. 42, and the lower side in FIG. 43 shows the current in the second half of the carrier cycle in FIG.
Japanese Patent Laid-Open No. 2003-189670 (page 14, FIG. 1)

  As described above, in the phase current detection method with only one current sensor, the phase currents for two phases are detected at different timings, and the phase currents of the remaining phases can be calculated from the two current values. it can.

  However, since the current changes within the carrier period even though it is small (in the drawing, it is shown for the sake of convenience), if phase currents for two phases are detected at different timings, Kirchoff's current law is It cannot be applied accurately, and the calculation for obtaining the phase current of the remaining phases becomes inaccurate. Also, when used for detecting the position of the magnet rotor 5, the arithmetic expression cannot be applied accurately, and the position detection error increases. The greater the modulation, the wider between the different detection timings. On the other hand, if the detection timings for detecting the phase currents for two phases are too close, the phase currents cannot be detected accurately.

  The present invention solves such a conventional problem, and in an inverter device that detects a phase current by a current sensor of a DC power supply line, a minimum necessary interval between different detection timings for detecting a phase current for two phases is required. The purpose is to provide an inverter device that can be limited.

  In order to solve the above problems, an inverter device according to the present invention includes an inverter circuit including an upper arm switching element connected to the plus side of a DC power source and a lower arm switching element connected to the minus side, a DC power source and an inverter. The control circuit includes a current sensor that detects a current between the circuits, and a control circuit that outputs an alternating current to the motor by applying PWM modulation to the inverter circuit and detects a phase current using the current sensor. On the basis of the ON signal or OFF signal to the upper arm switching element as the reference, the phase current for two phases is detected by the current sensor at the timing before and after the reference.

  With the above configuration, it is possible to minimize the interval between different detection timings for detecting phase currents for two phases. Therefore, the phase current and the position of the magnet rotor can be accurately detected.

  In the inverter device of the present invention, in the phase current detection by the current sensor of the DC power supply line, the interval between the different detection timings for detecting the phase current for two phases is minimized, and the phase current and the position of the magnet rotor are accurately determined. Can be detected.

  According to a first aspect of the present invention, there is provided an inverter circuit having an upper arm switching element connected to the plus side of a DC power source and a lower arm switching element connected to the minus side, and a current sensor for detecting a current between the DC power source and the inverter circuit And a control circuit that outputs an alternating current to the motor by applying PWM modulation to the inverter circuit and detects a phase current by a current sensor, the control circuit has an upper arm whose ON time is second. With reference to the ON signal or OFF signal to the switching element, the phase current for two phases is detected by the current sensor at the timing before and after the reference. With the above configuration, it is possible to minimize the interval between different detection timings for detecting phase currents for two phases. Therefore, the phase current and the position of the magnet rotor can be accurately detected.

  According to a second aspect, in the inverter device according to the first aspect, the timing before and after the reference differs depending on the direction of the current between the inverter circuit and the motor. That is, different timings are adopted depending on whether the current between the inverter circuit and the motor is positive or negative. This further minimizes the interval between different detection timings for detecting phase currents for two phases.

  According to a third aspect, in the inverter device according to the second aspect, the direction of the current is determined by the phase of the current to the motor. The control circuit can grasp the phase of the current by calculation. Thereby, the direction of the current can be easily determined without providing a special detector or the like.

  According to a fourth invention, in the inverter device of the second invention, the direction of the current is determined by the phase of the voltage applied to the motor. There is a correlation between the phase of the current and the phase of the applied voltage, and the control circuit can grasp it by calculation. Further, even if it is simply assumed that the phases of both are equal, there is no significant difference. Thereby, the direction of the current can be easily determined.

  According to a fifth invention, in the inverter devices of the first to fourth inventions, the timing before and after the reference is different between when the ON signal is used as a reference and when the OFF signal is used as a reference. That is, different timings are adopted for the first half and the second half in the carrier cycle. This further minimizes the interval between different detection timings for detecting phase currents for two phases.

  According to a sixth aspect of the present invention, in the inverter device according to the first to fifth aspects of the present invention, when the rotational speed of the motor is high, the phase current is detected by the current sensor. When the rotation speed of the motor is high, the rotation cycle is shortened. For this reason, the carrier period within one rotation period decreases, and the interval between different detection timings in phase current detection for two phases becomes relatively large with respect to one rotation period. That is, the influence of the interval between detection timings on the position detection is increased. Therefore, the effect of the present invention is great.

  According to a seventh invention, in the inverter device of the first to sixth inventions, when the PWM modulation is high, the phase current is detected by the current sensor. The higher the modulation, the wider the interval between different detection timings in phase current detection for two phases. That is, the influence of the interval between detection timings on the position detection and current detection increases. Therefore, the effect of the present invention is great.

  According to an eighth invention, in the inverter devices of the first to seventh inventions, the phase current detection by the current sensor is performed in the first half and the second half of the carrier cycle, and the average is calculated. The timing of current detection within the carrier period varies depending on the phase. At this time, the first half and the second half of the carrier cycle change in opposite directions. Therefore, the phase current detection is performed in the first half and the second half of the carrier cycle, and the average of these is calculated to obtain a value corresponding to the phase current detection at the center of the carrier cycle. That is, the phase current value is always detected (corresponding) at the center of the carrier period, and the accuracy of position detection and current detection can be improved.

  A ninth invention drives the motor of the electric compressor in the inverter device of the first to eighth inventions. As a result, even when the pressure difference between the refrigerant discharge side and the suction side is large, the position of the magnet rotor can be accurately detected, so that stable startup can be achieved.

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

(Embodiment 1)
FIG. 1 shows an inverter device 20 according to Embodiment 1 of the present invention and an electric circuit around it. The control circuit 7 of the inverter device 20 detects the phase current based on the voltage from the current sensor 6 provided on the power supply line. If phase currents for two phases are detected, the phase currents for the remaining phases can be calculated from the two current values (Kirchhoff's current law is applied at the neutral point of the stator winding 4).

  Based on these three-phase current values, the control circuit 7 calculates the induced voltage of the stator winding 4 by the magnet rotor 5 constituting the sensorless DC brushless motor 11 (hereinafter referred to as the motor 11), and the magnet rotor. 5 position detection is performed. Then, based on this position detection, rotation speed command signal (not shown), etc., the switching element 2 constituting the inverter circuit 10 is controlled, and the DC voltage from the battery 1 is switched by PWM modulation. An alternating current is output to the stator winding 4 constituting the motor 11. The diode 3 constituting the inverter circuit 10 serves as a circulation route for the current flowing through the stator winding 4. For the switching element 2, upper arm switching elements are defined as U, V, W, and lower arm switching elements are defined as X, Y, Z, and diodes corresponding to the switching elements U, V, W, X, Y, Z Is defined as 3U, 3V, 3W, 3X, 3Y, 3Z.

  The current sensor 6 may be any sensor that can detect an instantaneous peak current, such as a current sensor using a Hall element or a shunt resistor. Further, it may be provided on the positive side of the power supply line. If it is a shunt resistor, it is easy to realize miniaturization and improvement of vibration resistance.

  The control circuit 7 is connected to the upper arm switching elements U, V, W and the lower arm switching elements X, Y, Z by a connection line 18 via a drive circuit or the like, and controls each switching element. When the switching element 2 is an IGBT or a power MOSFET, the gate voltage is controlled. When the switching element 2 is a power transistor, the base current is controlled. Next, a method for detecting the phase current with the current sensor 6 will be described.

  FIG. 2 shows three-phase modulation waveforms with a maximum modulation of 50% with respect to the U-phase terminal voltage 41, the V-phase terminal voltage 42, the W-phase terminal voltage 43, and the neutral point voltage 29. This motor terminal voltage is equal to the voltage applied to the motor. In the three-phase modulation, as the degree of modulation increases, it extends in both directions of 0% and 100% centering on Duty 50%. These terminal voltages are realized by duty (%) indicated on the vertical axis by PWM modulation. The neutral point voltage 29 is a value obtained by calculating the sum of the terminal voltages of each phase and dividing by 3. The phase voltage is a value obtained by subtracting the neutral point voltage from the terminal voltage, and is a sine wave.

  On the other hand, assuming that the phase of the phase current is substantially equal to the phase of the terminal voltage, the current of the intermediate energized phase V flows out of the motor 11 in the phase indicated by-in FIG. The direction of the current flowing out of the motor 11 is defined as a negative direction. In the phase indicated by +, the current of the intermediate energized phase V phase flows into the motor 11. The direction of the current flowing into the motor 11 is defined as the + direction. In both the indicated phase and the indicated phase, the U phase that is the maximum energized phase is + current, and the W phase that is the minimum energized phase is -current.

  FIG. 3 shows an example of energization of the upper arm switching elements U, V, W and the lower arm switching elements X, Y, Z within one carrier (carrier cycle). ON / OFF for controlling each switching element from the control circuit 7 Signals are shown. In this case, the energization is performed at the phase indicated by − and the phase indicated by +, which is around 120 degrees in FIG. 2. There are four types of energization periods: (a), (b), (c), and (d). However, the dead time period is omitted to prevent a short circuit between the upper arm switching element and the lower arm switching element.

  First, consider the phase indicated in FIG. The intermediate energized phase V phase current is in the negative direction. The U-phase current iU becomes the maximum current. In the energization period (a), the upper arm switching elements U, V, W are all OFF, and the lower arm switching elements X, Y, Z are all ON. FIG. 4 shows the current flow at this time. U-phase current iU flows from a diode in parallel with lower arm switching element X to stator winding 4, and V-phase current iV and W-phase current iW respectively from stator winding 4 to lower arm switching elements Y and Z. It is flowing out. Therefore, no current flows through the current sensor 6.

  In the energization period (b), the upper arm switching element U is ON and the lower arm switching elements Y and Z are ON. FIG. 5 shows the current flow at this time. U-phase current iU flows from upper arm switching element U to stator winding 4, and V-phase current iV and W-phase current iW flow from stator winding 4 to lower arm switching elements Y and Z, respectively. Therefore, a U-phase current iU flows through the current sensor 6 and can be detected.

  In the energization period (c), the upper arm switching elements U and V are ON, and the lower arm switching element Z is ON. FIG. 6 shows the current flow at this time. U-phase current iU flows from upper arm switching element U to stator winding 4, and V-phase current iV flows from stator winding 4 to a diode in parallel with upper arm switching element V. The W-phase current iW flows from the stator winding 4 to the lower arm switching element Z. Therefore, a W-phase current iW flows through the current sensor 6 and can be detected.

  In the energization period (d), all the upper arm switching elements U, V, W are ON, and all the lower arm switching elements X, Y, Z are OFF. FIG. 7 shows the current flow at this time. U-phase current iU flows from upper arm switching element U to stator winding 4, and V-phase current iV and W-phase current iW flow from stator winding 4 to diodes in parallel with upper arm switching elements V and W, respectively. ing. Therefore, no current flows through the current sensor 6.

  FIG. 8 shows a change in the direct current in the phase indicated in FIG. 2 based on FIGS. The current sensor 6 can detect the U-phase current iU that is the maximum current during the energization period (b) and the W-phase current iW during the energization period (c).

  Next, the phase indicated by + in FIG. The intermediate energized phase V phase current is in the + direction. The W-phase current iW becomes the maximum current. In the energization period (a), the upper arm switching elements U, V, W are all OFF, and the lower arm switching elements X, Y, Z are all ON. FIG. 9 shows the current flow at this time. U-phase current iU and V-phase current iV flow from the diodes in parallel with lower arm switching elements X and Y to stator winding 4, respectively, and W-phase current iW flows from stator winding 4 to lower arm switching element Z. ing. Therefore, no current flows through the current sensor 6.

  In the energization period (b), the upper arm switching element U is ON and the lower arm switching elements Y and Z are ON. FIG. 10 shows the current flow at this time. U-phase current iU flows from upper arm switching element U to stator winding 4, V-phase current iV flows from a diode in parallel with lower arm switching element Y to stator winding 4, and W-phase current iW is stator. It flows from the winding 4 to the lower arm switching element Z. Therefore, a U-phase current iU flows through the current sensor 6 and can be detected.

  In the energization period (c), the upper arm switching elements U and V are ON, and the lower arm switching element Z is ON. FIG. 11 shows the current flow at this time. U-phase current iU and V-phase current iV flow from upper arm switching elements U and V to stator winding 4, respectively, and W-phase current iW flows from stator winding 4 to lower arm switching element Z. Therefore, a W-phase current iW flows through the current sensor 6 and can be detected.

  In the energization period (d), all the upper arm switching elements U, V, W are ON, and all the lower arm switching elements X, Y, Z are OFF. FIG. 12 shows the current flow at this time. U-phase current iU and V-phase current iV flow from upper arm switching elements U and V to stator winding 4, respectively, and W-phase current iW passes from stator winding 4 to a diode in parallel with upper arm switching element W. It is flowing out. Therefore, no current flows through the current sensor 6.

  FIG. 13 shows changes in DC current at the phase indicated by + in FIG. 2 based on FIG. 9 to FIG. The current sensor 6 can detect the U-phase current iU during the energization period (b), and the W-phase current iW that is the maximum current during the energization period (c). The U-phase current iU is detected during the energization period (b) and the W-phase current iW is detected during the energization period (c), as in FIG.

  4 to 13, the phase current that can be detected by the current sensor 6 when the upper arm switching elements U, V, and W are turned on and off is identified. That is, when only one phase is ON, the current of that phase can be detected, and when the two phases are ON, the current of the remaining phases can be detected, and when the three phases are ON and when the three phases are OFF, they cannot be detected. Therefore, when the ONOFF signal for controlling each switching element from the control circuit 7 and the ONOFF of each switching element coincide with each other without advance and delay, the control circuit 7 determines the current sensor based on the ONOFF signal for controlling each switching element. It is possible to identify and detect which phase current the current signal from 6 has.

  However, actually, the ONOFF signal for controlling each switching element from the control circuit 7 does not match the ONOFF of each switching element due to circuit characteristics or the like. Further, there are rise and fall characteristics of the element, dead time between the upper arm switching element and the lower arm switching element, and the like. For this reason, the control circuit 7 needs to consider these when setting the current detection timing and determining which phase current based on the ON / OFF signal for controlling each switching element.

  Hereinafter, these will be described. FIG. 14 shows a dead time incorporated in the energization timing chart of FIG. Considering the ON time tn and OFF time tf of the switching element in this timing chart, the change of the direct current shown in FIGS. 8 and 13 will be considered in detail.

  First, consider the direct current shown in FIG. The current iV of the intermediate energized phase V phase is in the negative direction. FIG. 15 shows the transition from the lower arm to the upper arm of U-phase current iU. The time relationship of switching is shown on the upper side, and the current flowing through the circuit elements in the time relationship is shown on the lower side. Before the OFF signal to the lower arm switching element X, it is in the state of FIG. When an OFF signal is output to the lower arm switching element X, the U-phase current iU flows from the diode 3X in parallel with the lower arm switching element X to the stator winding 4. In the circuit diagram, the upper arm side does not function and is omitted. Even after the OFF time tf of the lower arm switching element X, the U arm current iU flows from the diode 3X to the stator winding 4 because the upper arm switching element U is OFF. At this point, the lower arm switching element X does not function and is omitted from the circuit diagram.

  An ON signal is output from the OFF signal to the lower arm switching element X to the upper arm switching element U after the dead time td. The U-phase current iU flowing through the diode 3X starts to shift to the upper arm switching element U, and the transition is completed after the ON time tn of the upper arm switching element U. At this point, the state shown in FIG. 5 is obtained. Therefore, the U-phase current iU must be detected after tn from the ON signal to the upper arm switching element U.

  FIG. 16 shows the transition from the lower arm to the upper arm of the V-phase current iV. When an OFF signal is output to the lower arm switching element Y, the V-phase current iV flows from the stator winding 4 to the lower arm switching element Y. The V-phase current iV starts to shift to the diode 3V in parallel with the upper arm switching element V, and the transition is completed after the OFF time tf of the lower arm switching element Y. At this point, the state shown in FIG. Therefore, it is possible to detect the W-phase current iW before td-tf from the time when the ON signal is supplied to the upper arm switching element V (after the dead time td from the OFF signal to the lower arm switching element Y).

  FIG. 17 shows the transition from the lower arm to the upper arm of W-phase current iW. As in the case of the V-phase current iV in FIG. 16, the transition is completed td-tf before the ON signal time to the upper arm switching element W (after the dead time td from the OFF signal to the lower arm switching element Z). ing. At this point, the state shown in FIG.

  FIG. 18 shows the transition from the upper arm to the lower arm of W-phase current iW. Before the OFF signal to the upper arm switching element W, it is in the state of FIG. When the OFF signal is output to the upper arm switching element W, the W-phase current iW flows from the stator winding 4 to the diode 3W in parallel with the upper arm switching element W. In the circuit diagram, the lower arm side is not functioning and is omitted. Even after the OFF time tf of the upper arm switching element W, since the lower arm switching element Z is OFF, the W-phase current iW flows out from the stator winding 4 to the diode 3W. At this point, the upper arm switching element W is not functioning, and is therefore omitted from the circuit diagram.

  An ON signal is output to the lower arm switching element Z after the dead time td from the OFF signal to the upper arm switching element W. The W-phase current iW flowing through the diode 3W starts to shift to the lower arm switching element Z, and the transition is completed after the ON time tn of the lower arm switching element Z. At this point, the state shown in FIG. Therefore, it is necessary to detect the W-phase current iW after td + tn from the OFF signal to the upper arm switching element W.

  FIG. 19 shows the transition from the upper arm to the lower arm of V-phase current iV. As in the case of the W-phase current iW in FIG. 18, the transition is completed after the ON time tn of the lower arm switching element Y. At this point, the state shown in FIG. 5 is obtained. Therefore, the U-phase current iU needs to be detected after td + tn from the OFF signal to the upper arm switching element V.

  FIG. 20 shows the transition from the upper arm to the lower arm of U-phase current iU. When the OFF signal is output to the upper arm switching element U, the U-phase current iU flows from the upper arm switching element U to the stator winding 4. The U-phase current iU starts to shift to the diode 3X in parallel with the lower arm switching element X, and the transition is completed after the OFF time tf from the OFF signal to the upper arm switching element U. At this point, the state shown in FIG.

  Next, the direct current shown in FIG. 13 at the phase indicated by + in FIG. The current iV of the intermediate energized phase V phase is in the + direction. FIG. 21 shows the transition from the lower arm to the upper arm of U-phase current iU. Compared to FIG. 15, the magnitude of the current of the U-phase current iU is different, but the current direction is the same, so the timing relationship is the same as FIG. Before the OFF signal to the lower arm switching element X, it is in the state of FIG. Further, the transition is completed after the ON time tn of the upper arm switching element U. At this point, the state shown in FIG. 10 is obtained. Therefore, the U-phase current iU must be detected after tn from the ON signal to the upper arm switching element U.

  FIG. 22 shows the transition from the lower arm to the upper arm of V-phase current iV. In this case, since the direction of the V-phase current iV is reversed compared to FIG. 16, the timing relationship is different from FIG. The timing relationship is the same as FIG. 21 and FIG. 15 because the current direction is the same although the phase and current magnitude are different. The transition is completed after the ON time tn of the upper arm switching element V. At this point, the state shown in FIG. 11 is obtained. Therefore, detection of the W-phase current iW must be performed after tn from the ON signal to the upper arm switching element V.

  FIG. 23 shows the transition from the lower arm to the upper arm of W-phase current iW. Although the magnitude of the current is different, the current relationship is the same as in FIG. 17 because the current direction is the same. Therefore, the transition is completed before td-tf from the time of the ON signal to the upper arm switching element W (after the dead time td from the OFF signal to the lower arm switching element Z). At this point, the state shown in FIG.

  FIG. 24 shows the transition from the upper arm to the lower arm of the W-phase current iW. Although the magnitude of the current is different, the current relationship is the same as in FIG. 18 because the current direction is the same. The transition is completed after the ON time tn of the lower arm switching element Z. At this point, the state shown in FIG. 11 is obtained. Therefore, it is necessary to detect the W-phase current iW after td + tn from the OFF signal to the upper arm switching element W.

  FIG. 25 shows the transition from the upper arm to the lower arm of V-phase current iV. Since the direction of the V-phase current iV is reversed, the timing relationship is different from that in FIG. The timing relationship is the same as in FIG. 20 because the phase and current magnitude are different, but the current direction is the same. The transition is completed after the OFF time tf of the upper arm switching element V. At this point, the state shown in FIG. 10 is obtained. Therefore, it is possible to detect the U-phase current iU at an OFF time tf from the OFF signal to the upper arm switching element V.

  FIG. 26 shows the transition from the upper arm to the lower arm of U-phase current iU. Although the current magnitude is different, the current relationship is the same as in FIG. 20 because the current direction is the same. The transition is completed after the OFF time tf from the OFF signal to the upper arm switching element U. At this time, the state shown in FIG. 9 is obtained.

  FIG. 27 shows the details of the first half of the DC current change in the carrier period in FIG. 8 according to FIGS. 15, 16, and 17. This is a relationship between an ONOFF signal for controlling each switching element of the control circuit 7 and a direct current. There is no change in the direct current (U-phase current iU) for a while after the ON signal to the upper arm switching element U, but this is due to the delay by the filter circuit, drive circuit, etc. from the control circuit 7 to the switching element U. Yes. It is the same that there is no change in the direct current for a while from the OFF signal to the lower arm switching elements Y and Z. The rise time and fall time including this delay time are the ON time tn and OFF time tf of the switching element.

  As shown in FIG. 27, with reference to the ON signal to the V phase, which is the intermediate energized phase (the upper arm switching element has an intermediate ON time, that is, the ON time is the second phase), the current flows at the timing before and after the reference. The sensor 6 can detect phase currents for two phases. Here, the conditions under which the difference between different detection timings for detecting the phase currents for two phases is the minimum necessary will be examined. The time required for the current to be detected by the current sensor 6 and taken into the control circuit 7 is defined as tk.

  From FIG. 15, it is necessary to detect the U-phase current iU after tn from the ON signal to the upper arm switching element U. In order to reduce the interval from the detection timing of the W-phase current iW, it is necessary to set the detection timing of the U-phase current iU in the right direction while securing the time tk. Therefore, the detection timing of the U-phase current iU is a point indicated by a white triangle. Specifically, although it can be set in the right direction by the delay time from the OFF signal to the lower arm switching element Y, it is omitted because it is small. From FIG. 16, it is possible to detect the W-phase current iW before td-tf from the time of the ON signal to the upper arm switching element V. Therefore, the detection timing of the W-phase current iW is a point indicated by a black triangle. Accordingly, if the white triangle time with reference to the ON signal to the upper arm switching element V is tNU, tNU = −td−tk. If the time of the black triangle is tNW, tNW = −td + tf.

  FIG. 28 shows details of the latter half of the DC current change in the carrier period in FIG. 8 according to FIG. 18, FIG. 19, and FIG. Similarly, the conditions under which the difference between the different detection timings for detecting the phase current for two phases is the minimum necessary will be examined. From FIG. 18, it is necessary to detect the W-phase current iW after td + tn from the OFF signal to the upper arm switching element W. In order to reduce the interval between the detection timing of the U-phase current iU, it is necessary to set the detection timing of the W-phase current iW in the right direction while securing the time tk. Therefore, the detection timing of the W-phase current iW is a point indicated by a black triangle. Specifically, although it can be set in the right direction by the delay time from the ON signal to the lower arm switching element Y, it is omitted because it is small.

  From FIG. 19, it is necessary to detect the U-phase current iU after td + tn from the OFF signal to the upper arm switching element V. Therefore, the detection timing of the U-phase current iU is a point indicated by a white triangle. Therefore, if the time of the white triangle based on the OFF signal to the upper arm switching element V is tFU, tFU = td + tn. If the time of the black triangle is tFW, tFW = td−tk.

  Next, FIG. 29 shows details of the first half of the DC current change within the carrier period in FIG. 13 according to FIG. 21, FIG. 22, and FIG. Similarly, the conditions under which the difference between the different detection timings for detecting the phase current for two phases is the minimum necessary will be examined. From FIG. 21, it is necessary to detect the U-phase current iU after tn from the ON signal to the upper arm switching element U. In order to reduce the interval from the detection timing of the W-phase current iW, it is necessary to set the detection timing of the U-phase current iU in the right direction while securing the time tk. Therefore, the detection timing of the U-phase current iU is a point indicated by a white triangle. Specifically, although it can be set to the right by the delay time from the ON signal to the upper arm switching element V, it is omitted because it is small.

  From FIG. 22, it is necessary to detect the W-phase current iW after tn from the ON signal to the upper arm switching element V. Therefore, the detection timing of the W-phase current iW is a point indicated by a black triangle. Therefore, if the white triangle time with reference to the ON signal to the upper arm switching element V is tNU, tNU = −tk. If the black triangle time is tNW, tNW = tn.

  FIG. 30 shows details of the latter half of the DC current change within the carrier period in FIG. 13 with reference to FIGS. 24, 25, and 26. FIG. Similarly, the conditions under which the difference between the different detection timings for detecting the phase current for two phases is the minimum necessary will be examined. From FIG. 24, it is necessary to detect the W-phase current iW after td + tn from the OFF signal to the upper arm switching element W. In order to reduce the interval between the detection timing of the U-phase current iU, it is necessary to set the detection timing of the W-phase current iW in the right direction while securing the time tk. Therefore, the detection timing of the W-phase current iW is a point indicated by a black triangle. Specifically, although it can be set to the right by the delay time from the OFF signal to the upper arm switching element V, it is omitted because it is small.

  From FIG. 25, it is possible to detect the U-phase current iU at an OFF time tf from the OFF signal to the upper arm switching element V. Therefore, the detection timing of the U-phase current iU is a point indicated by a white triangle. Therefore, if the time of the white triangle with reference to the OFF signal to the upper arm switching element V is tFU, tFU = tf. If the black triangle time is tFW, then tFW = −tk.

  As described above, the interval between different detection timings (in this case, indicated by white triangles and black triangles) for detecting phase currents for two phases (in this case, U-phase current iU and W-phase current iW) is minimized. 27 and 30, tf + tk, and in FIGS. 28 and 29, tn + tk. These are constant without being affected even if the modulation changes by 10%, 50%, 100%, etc., or the carrier period is changed. Therefore, it becomes easy to set the current detection timing in the software program of the control circuit 7. Moreover, it becomes easy to arrange time allocation of various operations in the software program. In the above description, the intermediate energized phase (the phase in which the upper arm switching element is ON in the middle, that is, the second phase in which the ON time is ON) for reference when ON or OFF is the V phase.

  In the above embodiment, it is assumed that the phase of the phase current is substantially equal to the phase of the terminal voltage. However, when the phase current is not equal, the flow time of the U-phase current iU and the W-phase current iW in FIGS. The current detection timing determined by the direction of the motor current and whether it is the ON reference or the OFF reference does not change.

(Embodiment 2)
FIG. 31 shows a current detection timing selection flowchart in the first half of the carrier cycle based on the consideration in FIG. 27 and FIG. The detection timing based on the ON signal to the upper arm switching element V is selected according to the direction of the V-phase current that is the intermediate energized phase. In step 10, it is determined whether the intermediate energized phase is -current, that is, whether the current direction is a current flowing out of the motor. If it is current (Y), tNU and tNW in FIG. If not current (N), tNU and tNW in FIG. 29 are selected in step 12.

  Whether the intermediate energized phase is -current, that is, whether the direction of the current flows out of the motor, is determined by the phase of the phase current. As an example, when the phase current waveform of FIG. 2 is used, the V-phase current is a negative current at a phase of 0 ° to 120 ° and 300 ° to 360 °, and a positive current at a phase of 120 ° to 300 °. The control circuit 7 calculates this according to the rotation speed, applied voltage, load, and the like. Assuming that the phase of the terminal voltage, that is, the applied voltage and the phase of the phase current in FIG. 2 are substantially equal, the phase of the applied voltage may be used. It can also be determined by whether a current is flowing through the switching element or a parallel diode.

(Embodiment 3)
Similarly to FIG. 31, FIG. 32 shows a current detection timing selection flowchart in the latter half of the carrier period based on the consideration in FIGS. The detection timing based on the OFF signal to the upper arm switching element V is selected according to the direction of the V-phase current that is the intermediate energized phase. In step 20, it is determined whether the intermediate energized phase is -current, that is, whether the current direction is current flowing out of the motor. -If current (Y), in step 21, tFU and tFW in FIG. 28 are selected. If not current (N), tFU and tFW in FIG. 30 are selected in step 22.

  In the first half of the carrier cycle, the upper arm switching element is turned on, so the ON signal to the upper arm switching element is a reference, and in the second half of the carrier cycle, the upper arm switching element is turned off, so the upper arm switching element. The OFF signal to is the reference.

(Embodiment 4)
FIG. 33 shows the selection of whether the ON signal is used as a reference or the OFF signal as a reference in the flowcharts 31 and 32 described above.

  In step 30, it is determined whether the intermediate energized phase is -current, that is, whether the current direction is current flowing out of the motor. If it is current (Y), in step 31, it is selected whether or not the ON signal to the upper arm switching element is a reference. If it is ON standard (Y), tNU and tNW in FIG. If it is not the ON standard (N), tFU and tFW in FIG. If it is not -current (N) at step 30, whether or not the ON signal to the upper arm switching element is a reference is selected at step 34. If it is ON reference (Y), tNU and tNW in FIG. 29 are selected in step 35. If it is not the ON reference (N), tFU and tFW in FIG.

(Embodiment 5)
In this embodiment, the phase current is detected by the current sensor 6 when the rotational speed of the motor is high in each of the above embodiments. When the rotation speed of the motor is high, the rotation cycle becomes short. For this reason, the carrier period within one rotation period decreases, and the interval between different detection timings in phase current detection for two phases becomes relatively large with respect to one rotation period. That is, the influence of the interval between detection timings on the position detection is increased.

  As an example, it is assumed that the carrier period is 0.1 mS (10 kHz) and a two-pole motor. When the rotation speed is low and the rotation cycle is 100 mS (10 Hz), the carrier cycle within one rotation cycle is 1000. One carrier cycle corresponds to a rotation angle of about 0.36 degrees. On the other hand, when the rotation speed is high and the rotation period is 6.7 mS (150 Hz), the carrier period within one rotation period is 67. One carrier period corresponds to a rotation angle of about 5.4 degrees.

  That is, when the rotation period is 6.7 mS (150 Hz), the rotation angle corresponding to one carrier period is 15 times as compared with the case where the rotation period is 100 mS (10 Hz). For this reason, the influence between the different detection timings in the phase current detection for two phases within one carrier cycle also has a 15-fold effect on the position detection. Therefore, the present invention that can reduce the interval between the different detection timings in the phase current detection is particularly effective when the rotational speed of the motor is high.

(Embodiment 6)
In FIG. 34, the ON periods (Duty) of the upper arm switching elements U, V, and W within one carrier period in the phase of 30 to 90 degrees indicated by the broken line in FIG. 2 are displayed symmetrically from the center. The ON period of the U-phase upper arm switching element U is represented by a thin solid line, the ON period of the V-phase upper arm switching element V is represented by a solid solid line, and the ON period of the W-phase upper arm switching element W is represented by a thick solid line. ing. This is generally realized by the timer function of the microcomputer. A period in which current detection by the current sensor 6 can be performed is set as a detection period, and is indicated by a solid line arrow, and indicates a phase of the current detected in the vicinity of the solid line arrow. In this case, the detection period of the U-phase current is indicated as U, and the detection period of the V-phase current is indicated as V. Similarly, FIG. 35 shows a case where the maximum modulation is 100%.

  At the phase of 60 degrees, the conventional timing of U-phase phase current detection is indicated by a vertical white arrow, and the conventional timing of V-phase phase current detection is indicated by a vertical horizontal arrow. In this case, the conventional timing is an example of phase current detection at the left end of the detection period. Comparing FIG. 34 and FIG. 35, in the case of the maximum modulation of 100% in FIG. 35, the interval between the different detection timings (vertical white arrow and vertical horizontal line) in the case of the maximum modulation of 50% in FIG. The distance between the arrows is large. Therefore, the present invention that can reduce the interval between different detection timings in phase current detection is particularly effective when the modulation is high. In this case, the W phase is an intermediate energized phase.

  FIG. 36 shows two-phase modulation waveforms with a maximum modulation of 50% with respect to the U-phase terminal voltage 41, the V-phase terminal voltage 42, the W-phase terminal voltage 43, and the neutral point voltage 29. This motor terminal voltage is equal to the voltage applied to the motor. In the two-phase modulation, it increases in the direction of 100% as the modulation degree increases. In FIG. 37, the ON periods (Duty) of the upper arm switching elements U, V, and W within one carrier period in the phase of 90 to 150 degrees indicated by the broken line in FIG. 36 are displayed symmetrically from the center. The notation items are the same as those in FIGS. FIG. 38 shows a case where the maximum modulation is 100%.

  At the phase of 120 degrees, the conventional timing for detecting the U-phase current is indicated by a vertical white arrow, and the conventional timing for detecting the W-phase current is indicated by a vertical black arrow. In the case of the maximum modulation of 100% in FIG. 38, the interval between the different detection timings in the phase current detection (the interval between the vertical white arrow and the vertical black arrow) is larger than in the case of the maximum modulation of 50% in FIG. Therefore, the present invention that can reduce the interval between different detection timings in phase current detection is particularly effective when the modulation is high. This is the same as in the case of the three-phase modulation. In the two-phase modulation, the W phase (stationary phase) of 0% is the minimum energized phase, and the V phase is the intermediate energized phase.

(Embodiment 7)
In this embodiment, the phase current detection by the current sensor 6 is performed in the first half and the second half of the carrier cycle in each of the above embodiments, and the average is calculated. The current detection timing within the carrier period varies depending on the phase. At this time, the first half and the second half of the carrier cycle change in opposite directions. 34, 35, 37, and 38, the current detection timing in the first half of the carrier cycle is indicated by a white rhombus, and the current detection timing in the second half is indicated by a black rhombus. It can be seen that the current detection timing changes as described above.

  For this reason, the timing of current detection in the carrier cycle differs depending on the phase, and the accuracy of position detection and current detection is reduced. The phase, detection position, and detection current value do not match exactly. In response to this, phase current detection is performed in the first half (white rhombus) and the second half (black rhombus) of the carrier period, and the average is calculated. As a result, a value corresponding to the phase current detection at the center of the carrier period can be obtained. That is, the phase current value (corresponding) at the center of the carrier period can always be obtained, and the accuracy of position detection and current detection can be improved.

  In each of the above embodiments, the DC power source is a battery. However, the present invention is not limited to this, and a DC power source rectified from a commercial AC power source may be used. Although the motor 11 is a sensorless DC brushless motor, it can also be applied to a reluctance motor, an induction motor, or the like. It can be applied to other than sine wave drive. Also, the two-phase modulation can be applied when the stationary phase is the minimum energized phase and the current in the first half and the second half in the carrier cycle are continuous as described above. Further, a 100% stationary phase may be the maximum energized phase.

  As described above, the inverter device according to the present invention can minimize the interval between different detection timings for detecting phase currents for two phases, and can accurately detect the phase current and the position of the magnet rotor. Therefore, it can be applied to various consumer products and various industrial equipment. The load can be applied to AC devices other than motors.

The inverter apparatus which concerns on Embodiment 1 of this invention, and its surrounding electric circuit diagram Waveform diagram showing modulation of each phase at maximum modulation 50% of three-phase modulation Energization timing chart in carrier cycle Electrical circuit diagram showing current path of energization period (a) when intermediate energization phase is -current Electric circuit diagram showing current path in same energization period (b) Electric circuit diagram showing current path in same energization period (c) Electric circuit diagram showing current path in same energization period (d) DC current waveform diagram flowing in the DC power line within the same carrier cycle Electrical circuit diagram showing current path in energization period (a) when intermediate energization phase is + current Electric circuit diagram showing current path in same energization period (b) Electric circuit diagram showing current path in same energization period (c) Electric circuit diagram showing current path in same energization period (d) DC current waveform diagram flowing in the DC power line within the same carrier cycle Energization timing chart including dead time Transition diagram of the U-phase current from the lower arm to the upper arm when the intermediate energized phase is -current Transition diagram of the V-phase current from the lower arm to the upper arm Transition state diagram from lower arm to upper arm of W phase current Transition state diagram from upper arm to lower arm of W phase current Transition state diagram of the V-phase current from the upper arm to the lower arm Transition diagram of the U-phase current from the upper arm to the lower arm Transition diagram of the U-phase current from the lower arm to the upper arm when the intermediate energized phase is + current Transition diagram of the V-phase current from the lower arm to the upper arm Transition state diagram from lower arm to upper arm of W phase current Transition state diagram from upper arm to lower arm of W phase current Transition state diagram of the V-phase current from the upper arm to the lower arm Transition diagram of the U-phase current from the upper arm to the lower arm DC current detection timing explanatory diagram in the first half of the carrier cycle when the intermediate energized phase is -current DC current detection timing explanatory diagram in the latter half of the same carrier cycle DC current detection timing explanatory diagram in the first half of the carrier cycle when the intermediate energized phase is + current DC current detection timing explanatory diagram in the latter half of the same carrier cycle The flowchart which selects the direct current detection timing based on the direction of the electric current of an intermediate energization phase based on Embodiment 2 of this invention. The flowchart which selects the direct current detection timing based on the direction of the electric current of an intermediate energization phase based on Embodiment 3 of this invention. The flowchart which selects the direct current detection timing based on the direction of the electric current of an intermediate | middle energized phase, and a reference | standard is ON or OFF based on Embodiment 4 of this invention Explanatory drawing in the maximum modulation 50% three-phase modulation according to Embodiments 6 to 7 of the present invention Explanatory drawing in the maximum modulation 100% three-phase modulation according to Embodiments 6 to 7 of the present invention Waveform diagram showing modulation of each phase at maximum modulation 50% of two-phase modulation Explanatory drawing in the maximum modulation 50% two-phase modulation according to Embodiments 6 to 7 of the present invention Explanatory drawing in the maximum modulation 100% two-phase modulation according to Embodiments 6 to 7 of the present invention Inverter device that detects phase current with current sensor of power line and electrical circuit diagram around it Waveform diagram showing modulation of each phase at maximum modulation 50% of three-phase modulation Energization timing chart in carrier cycle DC current waveform diagram flowing in the DC power supply line within the carrier cycle Explanatory drawing of timing to detect phase current for two phases

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 2 Switching element 3 Diode 4 Stator winding 5 Magnet rotor 6 Current sensor 7 Control circuit 10 Inverter circuit 11 Sensorless DC brushless motor 20 Inverter device

Claims (7)

An inverter circuit comprising an upper arm switching element connected to the positive side of a DC power source and a lower arm switching element connected to the negative side; a current sensor for detecting a current between the DC power source and the inverter circuit; and the inverter The circuit includes a control circuit that outputs an alternating current to the motor by energizing PWM modulation, and the control circuit is based on the ON signal or OFF signal to the upper arm switching element whose ON time is second, before and after the reference In the inverter device that detects the phase currents for two phases by the current sensor at the timing of, when the current direction between the inverter circuit and the motor flows out from the motor, the timing before and after the reference flows into the motor Compared to
An inverter device characterized in that the timing before and after the reference is advanced when an ON signal is used as a reference, and is delayed when an OFF signal is used as a reference . The inverter device according to claim 1 , wherein the direction of the current is determined by a phase of a current to the motor. The inverter device according to claim 1 , wherein the direction of the current is determined by a phase of a voltage applied to the motor. The said control circuit is an inverter apparatus as described in any one of Claims 1-3 which performs a phase current detection by the said current sensor, when the rotation speed of a motor is high. The inverter device according to any one of claims 1 to 3 , wherein the control circuit performs phase current detection by the current sensor when PWM modulation is high. 6. The inverter device according to claim 1 , wherein the control circuit performs phase current detection by the current sensor in a first half and a second half of a carrier cycle and calculates an average thereof. The inverter apparatus as described in any one of Claims 1-6 which drives the motor of an electric compressor.

Images