JP2009022086A - Inverter apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and reliable inverter device which computes the average of a DC current with high accuracy without providing an integrating circuit and an A/D port for average current input. <P>SOLUTION: The inverter apparatus equipped with an inverter circuit with upper arm switching elements and lower arm switching elements, a current detector between a DC power source and an inverter circuit, and a control circuit which controls the switching element and outputs a AC current to a motor, and a control circuit which detects a current by a current sensor. The control circuit computes the average of a DC current which flows between it and the DC power source, based on the product of the time of outputting an ON signal to only one of the upper arm switching elements and the current value detected by a current detector at that time and the product of the time of outputting an ON signal to only two of the upper arm switching elements and the current value detected by the current detector at that time, by reducing the time for outputting the ON signal as compared with the actual output time by a predetermined value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inverter device for calculating an average value and an effective value of a direct current from a direct current power source.

  Conventionally, as a method for calculating the average value of DC current from a DC power supply, a method is known in which a current sensor is provided in a power supply line from the DC power supply to the inverter device, and this DC current is detected and integrated by a resistor and a capacitor. (For example, refer to Patent Document 1).

  FIG. 33 shows an inverter device and its surrounding electric circuit. The control circuit 14 of the inverter device 22 controls the switching element 2 constituting the inverter circuit 10 based on a rotation speed command signal (not shown) and the like, and switches the DC voltage from the battery 1 by PWM modulation. An alternating current is output to the stator winding 4 constituting the motor 11. 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. As the switching element 2, a transistor, an IGBT, or the like is used. The diode 3 constituting the inverter circuit 10 serves as a return route for the current flowing through the stator winding 4.

  The direct current value detected by the current sensor 6 is converted to an average value by the operational amplifier 15, the resistor 12 and the capacitor 13, and transmitted to the control circuit 14. And it is used for calculation of the power consumption of the inverter apparatus 22 from the product with the voltage of the battery 1. The calculation of power consumption is indispensable for monitoring the power consumption of the load of the battery 1, which is a DC power source, that is, the power consumption of the inverter device 22, and for limiting the power consumption.

Further, the peak value of the direct current detected by the current sensor 6 is transmitted to the control circuit 14 via the operational amplifier 15. And it is used for judgment etc. for protecting switching element 2 grade.
Japanese Patent Laid-Open No. 7-67248 (5th page, FIGS. 1 and 2)

  In the method for calculating the average value of the direct current from the direct current power source, in addition to the current sensor and the operational amplifier, an integration circuit using a resistor and a capacitor and an A / D port for inputting an average current of the microcomputer in the control circuit are required. It becomes the subject of improvement and reliability improvement. In addition, the resistance value of the resistor, the variation of the capacitance value of the capacitor, and the temperature change are affected. Furthermore, it is necessary to obtain the correlation between the integrated value of the resistor and the capacitor and the actual average current, which is a problem of improving accuracy. The effective value cannot be detected.

  In an inverter device provided with a current sensor for detecting a load current (motor phase current) between the inverter circuit and a load (motor), a DC current from a DC power source cannot be measured. Therefore, the average current cannot be obtained, and the power consumption of the DC power source cannot be calculated. Although AC power from the phase current to the motor can be calculated, it is necessary to calculate the phase difference between the current and voltage, the PWM voltage, etc., and the calculation load of the microcomputer constituting the control circuit becomes excessive. Further, when AC power is calculated and used as a substitute for DC power, the power consumption of the inverter device is not included and becomes inaccurate.

  In an inverter device having a shunt resistor for detecting a phase current between a lower arm switching element and a DC power source (battery), the DC current from the DC power source cannot be measured. Therefore, the same problem as described above occurs.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a highly reliable and compact inverter device capable of calculating an average value and an effective value of a direct current with high accuracy.

  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 supply and a lower arm switching element connected to the minus side, a DC power supply, A current detector between the inverter circuits and a control circuit for controlling the switching element to output an alternating current to the motor and detecting the current by a current sensor, and the control circuit is provided for only one of the upper arm switching elements. The product of the time during which the ON signal is output and the current value detected by the current detector at that time, and the time during which the ON signal is output to only two of the upper arm switching elements and the current at that time Based on the product of the current value detected by the detector and the average value and effective value of the direct current flowing between the direct current power supply and the ON signal, Time that the force are those calculated by a predetermined value smaller than the time that is actually output.

  With the above configuration, it is not necessary to provide an integrating circuit using resistors and capacitors and an A / D port for inputting average current of the microcomputer in the control circuit, and it is possible to calculate an average value of DC current and further an effective value. Therefore, a highly reliable and small inverter device that can calculate the average value and effective value of the direct current with high accuracy can be realized.

  The inverter device of the present invention is small and highly reliable, and can calculate an average value and an effective value of DC current with high accuracy.

  According to a first aspect of the present invention, there is provided an inverter circuit including an upper arm switching element connected to a positive side of a DC power source and a lower arm switching element connected to a negative side, a current detector between the DC power source and the inverter circuit, A control circuit that controls the switching element to output an alternating current to the motor and detects the current by a current sensor, and the control circuit outputs an ON signal to only one of the upper arm switching elements; The product of the current value detected by the current detector at the time, the time when the ON signal is output to only two of the upper arm switching elements, and the current value detected by the current detector at the time When calculating the average value of DC current flowing between the DC power supply based on the product of the And calculates and value smaller.

  With the above configuration, it is possible to calculate the average value of the direct current without the need to provide an integrating circuit with resistors and capacitors and an A / D port for inputting average current of the microcomputer in the control circuit. Therefore, a highly reliable and small inverter device that can detect the average value of the direct current with high accuracy can be realized.

  According to a second invention, in the inverter device of the first invention, the predetermined value is a delay time from when the control circuit outputs an ON signal to the switching element until the ON of the switching element is completed. Thereby, the average current can be calculated in accordance with the actual current behavior.

  According to a third aspect of the present invention, in the inverter device of the second aspect, when the direction of the current in the intermediate energized phase is the direction of flowing out from the motor, the time for outputting the ON signal to only one upper arm switching element is the delay time. When the current direction of the intermediate energized phase is the direction of flowing into the motor, the time during which the ON signal is output to only the two upper arm switching elements is calculated by reducing the delay time. As a result, the average current can be calculated more accurately in accordance with the actual current behavior.

  According to a fourth aspect of the present invention, in the inverter device of the first to third aspects of the invention, the time during which only one of the upper arm switching elements is ON is the time during which only two of the lower arm switching elements are ON. The time when only two of the upper arm switching elements are ON is replaced with the time when only one of the lower arm switching elements is ON, respectively. This makes it possible to select a time that can be easily referred to as appropriate, so that the average value of the direct current can be easily calculated.

  According to a fifth invention, in the inverter device of the first to fourth inventions, a current detector is provided in series with the lower arm switching element instead of the current detector between the DC power source and the inverter circuit. Thereby, the average value calculation of direct current is applicable also to the inverter apparatus from which a current detection system differs.

  According to a sixth invention, in the inverter device of the first to fourth inventions, a current detector is provided between the inverter circuit and the motor in place of the current detector between the DC power source and the inverter circuit. Thereby, the average value calculation of direct current is applicable also to the inverter apparatus from which a current detection system differs.

  According to a seventh aspect, in the inverter devices of the first to sixth aspects, an effective value is calculated instead of the average value of the direct current. Thereby, it is possible to calculate the internal resistance of the DC power supply, the power consumption by the elements of the DC power supply line, heat generation, and the like.

  An eighth invention drives the motor of the electric compressor in the inverter device of the first to seventh inventions. Since the power consumption from the DC power supply can be accurately calculated, it can contribute to the energy saving operation of the air conditioning.

  According to a ninth invention, in the inverter device of the eighth invention, the inverter device is mounted on an electric compressor. The inverter device mounted on the electric compressor has a limited installation space and needs to be miniaturized, and needs vibration resistance against vibration from the motor. Therefore, a resistor, a capacitor, an A / D port of a microcomputer, and the like are unnecessary, and the present inverter device that can contribute to an improvement in reliability of downsizing and weight reduction is useful.

  A tenth aspect of the invention is the inverter device according to the first to ninth aspects of the invention mounted on a vehicle. For vehicles, the mounting space is limited, miniaturization is required, and vibration resistance against running vibration is also required. Therefore, a resistor, a capacitor, an A / D port of a microcomputer, and the like are unnecessary, and the present inverter device that can contribute to an improvement in reliability of downsizing and weight reduction is useful.

  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 current based on the voltage from the current sensor 6 provided on the power supply line. The phase current value is obtained from this current value. And the induced voltage of the stator winding | coil 4 by the magnet rotor 5 which comprises the sensorless DC brushless motor 11 (henceforth the motor 11) is calculated, and the position detection of the magnet rotor 5 is performed. 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, so that a sinusoidal AC current is obtained. 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.

  Hereinafter, the relationship between the current flowing through the current sensor 6 and the ON / OFF timing of the switching element will be examined, and the calculation of the average value of the current will be considered. 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. It is assumed that the terminal voltage, that is, the phase of the applied voltage and the phase of the phase current are substantially equal. In the phase indicated by-in FIG. 2, the V-phase current flows out of the motor 11. The direction of the current flowing out of the motor 11 is defined as a negative direction. In the phase indicated by +, the V-phase current 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 is + current and the W 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. This is generally realized by the timer function of the microcomputer. In this case, energization is performed around 120 degrees in the vicinity of the phase indicated by − (minus) in FIG. Within the carrier cycle, the phase with the maximum energization period is the maximum energization phase (U phase in FIG. 3), the intermediate phase is the intermediate energization phase (V phase in FIG. 3), and the minimum phase is the minimum energization phase (FIG. 3). In the case of W phase). There are four types of energization periods: (a), (b), (c), and (d).

  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 is 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 is 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 U-phase current iU, which is the maximum current, flows in the current sensor 6 during the energization period (b), and the W-phase current iW flows in the current sensor 6 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.

  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.

  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 U-phase current iU flows through the current sensor 6 during the energization period (b), and the W-phase current iW that is the maximum current flows through the current sensor 6 during the energization period (c). The U-phase current iU flows in the energization period (b) and the W-phase current iW flows in the energization period (c), as in FIG.

  4 to 13, it can be seen that the phase current flowing in the current sensor 6 is specified when the upper arm switching elements U, V, W are turned on and off. 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. It does not flow when 3 phase is ON and 3 phase is OFF.

  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 signal from the current sensor 6 and each switching element. It can be seen that the average value of the current can be calculated from the current flowing time based on the ON / OFF signal to be controlled.

  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. In addition, 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. Therefore, it is necessary to consider these.

  These will be discussed in detail below. 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, changes in the direct current shown in FIGS. 8 and 13 are shown below.

  First, the direct current shown in FIG. 8 in the phase indicated by − (minus) in FIG. 2 will be considered. 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, the current is in the state shown in 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. In the circuit diagram, the lower arm switching element X does not function and is omitted.

  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 current is in the state shown in FIG.

  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 current is in the state shown in FIG. The dead time td is set longer than the OFF time tf in order to prevent a short circuit. Therefore, the transition is completed 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 W-phase current iW starts to shift to the diode 3W in parallel with the upper arm switching element W, and the transition is completed after the OFF time tf of the lower arm switching element Z. At this point, the current is in the state shown in FIG.

  FIG. 18 shows the transition from the upper arm to the lower arm of W-phase current iW. Prior to the OFF signal to the upper arm switching element W, the current is in the state shown in 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. In the circuit diagram, the upper arm switching element W is omitted because it does not function.

  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 current is in the state shown in FIG.

  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 current is in the state shown in FIG.

  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 of the upper arm switching element U. At this point, the current is in 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, the current is in the state shown in FIG. Further, the transition is completed after the ON time tn of the upper arm switching element U. At this point, the current is in the state shown in FIG.

  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 that in FIGS. 15 and 21 because the current direction is the same although the phase and current magnitude are different. When the OFF signal is output to the lower arm switching element Y, the V-phase current iV flows from the diode 3Y in parallel with the lower arm switching element Y 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 Y, since the upper arm switching element V is OFF, the V-phase current iV flows from the diode 3Y to the stator winding 4. In the circuit diagram, the lower arm switching element Y is omitted because it does not function.

  An ON signal is output from the OFF signal to the lower arm switching element Y to the upper arm switching element V after the dead time td. The V-phase current iV flowing in the diode 3Y starts to shift to the upper arm switching element V, and the transition is completed after the ON time tn of the upper arm switching element V. At this point, the current is in the state shown in FIG.

  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. The W-phase current iW starts to shift to the diode 3W in parallel with the upper arm switching element W, and the transition is completed after the OFF time tf of the lower arm switching element Z. At this point, the current is in 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.

  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. When an OFF signal is output to the upper arm switching element V, the V-phase current iV flows from the upper arm switching element V to the stator winding 4. The V-phase current iV starts to shift to the diode 3Y in parallel with the lower arm switching element Y, and the transition is completed after the OFF time tf of the upper arm switching element V. At this point, the current is in the state shown in FIG. The dead time td is set longer than the OFF time tf in order to prevent a short circuit. Therefore, the transition is completed after the dead time td 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 of the upper arm switching element U. At this point, the current is in the state shown in FIG.

  FIG. 27 shows the details of the left side (first half) of the DC current change in the carrier period in FIG. 8 (the current iV of the intermediate energization phase V phase is in the negative direction) by FIG. 15, FIG. 16, and FIG. 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 a delay by the filter circuit, drive circuit, etc. from the control circuit 7 to the switching element U. ing. 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 delay time includes the rise time of the switching element and is the ON time tn of the switching element. The same applies to the aforementioned OFF time tf.

  FIG. 28 shows details of the right side (second half) of the DC current change in the carrier period in FIG. 8 according to FIG. 18, FIG. 19, and FIG. FIG. 29 shows details of the left side of the DC current change in the carrier period in FIG. 13 (the current iV of the intermediate energized phase V phase is in the + direction) with reference to FIGS. 21, 22, and 23. FIG. 30 shows details of the right side of the DC current change in the carrier period in FIG. 13 with reference to FIGS. 24, 25, and 26. FIG.

  As shown in FIGS. 27 to 30, the control circuit 7 outputs the product of the time for outputting the ON signal to only one upper arm switching element U and the U-phase current iU, and only the two upper arm switching elements U and V. An average value can be calculated by dividing the sum of the product of the ON signal output time and the W-phase current iW by a predetermined time (such as half the carrier period).

  However, the total time of the time for the control circuit 7 to output the ON signal to only one upper arm switching element U and the time to output the ON signal to only two upper arm switching elements U and V is the flow of the U-phase current iU. It is longer than the total time of the time and the time during which the W-phase current iW flows. This is due to the ON time tn and the OFF time tf. The current value must be detected after the ON time tn and the OFF time tf have elapsed and the current value has stabilized.

  Therefore, in calculating the average value, the control circuit 7 calculates the total time of the time for outputting the ON signal to only one upper arm switching element U and the time for outputting the ON signal to only two upper arm switching elements U and V. It is necessary to reduce the predetermined value. Thereby, accuracy can be improved.

(Embodiment 2)
As the predetermined value, an ON time tn (OFF time tf) is appropriate in FIGS. 27 and 29, both ends are rising and falling with reference to ON of the upper arm switching element, and when ½ of the ON time tn (OFF time tf) is reduced at the left end and right end respectively, It becomes appropriate as the current flow time. In FIGS. 28 and 30, when the lower arm switching element is turned on instead of the upper arm switching element being turned off, both ends are rising and falling, and the left end and the right end are respectively turned on time tn (OFF time tf). ) Is reduced as a current flowing time. The upper arm switching element OFF and the lower arm switching element ON are only shifted by the dead time td.

(Embodiment 3)
In FIG. 27 and FIG. 28 in which the current direction of the intermediate energized phase V phase is in the negative direction, as can be seen from FIG. If the time for outputting the ON signal to only one upper arm switching element U is reduced by the ON time tn (OFF time tf), it becomes appropriate as the current flowing time. On the other hand, in FIGS. 29 and 30 where the direction of the current of the intermediate energized phase V phase is in the negative direction, as can be seen from FIG. If the time for outputting the ON signal to only the upper arm switching elements U and V2 is reduced by the ON time tn (OFF time tf), the current flows appropriately.

  The determination of whether the intermediate energized phase is + current can be estimated from the current of the intermediate energized phase in the previous carrier cycle. Further, since the control circuit 7 detects the phase current in units of carrier cycles, the phase can be grasped by calculation. Therefore, it can be estimated whether the current of the intermediate energized phase in the carrier cycle in which the phase current is to be detected is a positive current. Instead of the phase of the current, a substitution can be made as it can be approximated by the phase of the applied voltage. For example, in FIG. 2, + current and −current are reversed at a phase of 120 degrees. It can also be determined by whether the current is flowing through the switching element or the parallel diode.

(Embodiment 4)
In FIGS. 27 to 30, the time during which only one upper arm switching element U is ON is equal to the time during which only two lower arm switching elements Y and Z are ON. The time during which only the upper arm switching elements U and V2 are ON is equal to the time during which only one lower arm switching element Z1 is ON. Therefore, each can be replaced.

(Embodiment 5)
FIG. 31 shows an inverter device and its peripheral circuits in the present embodiment. A shunt resistor 25 is provided between the U-phase lower arm switching element X and the ground, a shunt resistor 26 is provided between the V-phase lower arm switching element Y and the ground, and a shunt resistor 27 is provided between the W-phase lower arm switching element Z and the ground. . The control circuit 24 of the inverter device 21 detects the phase current of each phase based on the voltage from each shunt resistor.

  In calculating the average value of the current of the DC power supply line, the current values in FIGS. 27 to 30 are detected by the respective shunt resistors. The U-phase phase current iU is detected by the shunt resistor 25, and the W-phase phase current iW is detected by the shunt resistor 27. When the U-phase phase current iU cannot be detected by the shunt resistor 25, for example, in the case of FIG. 5, it is obtained by the sum of the V-phase phase current iV (shunt resistor 26) and the W-phase phase current iW (shunt resistor 27). .

(Embodiment 6)
The case where two current sensors (not shown) are provided between the inverter circuit 10 and the motor 11 is the same as in the fifth embodiment. For example, when provided in the U phase and the V phase, the current values in FIGS. 27 to 30 are detected by the current sensor as the U phase current iU. The W-phase phase current iW is obtained from the sum of the U-phase phase current iU and the V-phase phase current iV (detected by the current sensor).

(Embodiment 7)
The effective value can be calculated in the same manner as the average value, although the current value is squared. In the examples of FIGS. 27 to 30, the product of the time for outputting the ON signal to only one upper arm switching element U and the square of the U-phase current iU, and the ON signal to only two upper arm switching elements U and V are used. The effective value can be calculated by dividing the sum of the product of the output time and the square of the W-phase current iW by a predetermined time (such as half of the carrier period) and raising the sum to 1/2.

(Embodiment 8)
FIG. 32 shows a diagram in which the inverter device 20 is attached in close contact with the right side of the electric compressor 40. The compression mechanism 28, the motor 11, and the like are installed in the metal casing 32. The refrigerant is sucked from the suction port 33 and compressed by the compression mechanism 28 (scroll in this example) being driven by the motor 11. The compressed refrigerant cools the motor 11 when passing through the motor 11 and is discharged from the discharge port 34.

  The inverter device 20 uses a case 30 so as to be attached to the electric compressor 40. The inverter circuit unit 10 serving as a heat source is cooled by the low-pressure refrigerant through the low-pressure pipe 38. A terminal 39 connected to the winding of the motor 11 inside the electric compressor 40 is connected to the output unit of the inverter circuit unit 10. The connection line 36 fixed to the inverter device 23 by the holding unit 35 includes a power line to the battery 1 and a signal line to an air conditioner controller (not shown) that transmits a rotation speed signal.

  In such an inverter device integrated electric compressor, it is necessary that the inverter device 20 is small and highly reliable. Therefore, it is suitable as an embodiment of the present invention. Moreover, since the power consumption from a DC power supply can be accurately calculated, it is possible to contribute to energy saving operation of air conditioning.

  In each of the above embodiments, the case where the phase is around 120 degrees in FIG. 2 has been considered, but other cases can be considered in the same manner. The calculation period of the average value and the effective value is half of the carrier period, but it may be one period or the other. Although the DC power supply is a battery, the present invention is not limited to this, and a DC power supply obtained by rectifying a commercial AC power supply may be used. Although an example of a motor is shown as a load, it can also be applied to various devices using an AC power source, a transformer, and the like. 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. It can also be applied to two-phase modulation.

  As described above, the inverter device according to the present invention can calculate the average value of the direct current with high accuracy without providing an integrating circuit (resistor and capacitor) and an A / D port (for inputting the average current of the microcomputer in the control circuit). It can be calculated. Moreover, since it is small and highly reliable, it can be applied to various consumer products, various industrial devices, and various mobile devices. 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 detected 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 detected 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 Detailed waveform diagram of DC current on the left side in the carrier cycle when the intermediate energized phase is -current Detailed waveform diagram of DC current on the right in the same carrier cycle Detailed waveform diagram of DC current on the left side in the carrier cycle when the intermediate energized phase is + current Detailed waveform diagram of DC current on the right in the same carrier cycle Embodiment 5 of the present invention and its peripheral electrical circuit diagram Sectional drawing of the inverter apparatus integrated electric compressor which concerns on Embodiment 8 of this invention. Electric circuit diagram of an inverter device that detects the average value of conventional DC current

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 (inverter apparatus 20)
10 Inverter circuit 11 Sensorless DC brushless motor 20 Inverter device (current sensor on DC power line)
21 Inverter device (shunt resistor for current detection on the lower arm)
24 Control circuit (inverter device 21)
25 Lower arm shunt resistor for current detection (U phase)
26 Lower arm shunt resistor for current detection (phase V)
27 Lower arm shunt resistor for current detection (W phase)
40 Electric compressor

Claims (10)

An inverter circuit comprising an upper arm switching element connected to the positive side of the DC power source and a lower arm switching element connected to the negative side, a current detector between the DC power source and the inverter circuit, and the switching element In an inverter device including a control circuit that controls to output an alternating current to the motor and detects the current by the current sensor, the control circuit outputs an ON signal to only one of the upper arm switching elements. Product of the current time and the current value detected by the current detector at the time, and the time when the ON signal is output to only two of the upper arm switching elements and the current detector at the time When calculating the average value of the direct current flowing between the direct current power source based on the product of the current value and the ON signal, Force to which time inverter device calculated by a predetermined value smaller than the time that is actually output. 2. The inverter device according to claim 1, wherein the predetermined value is a delay time from when the control circuit outputs an ON signal to the switching element until the ON of the switching element is completed. When the current direction of the intermediate energized phase is the direction of flowing out of the motor, the time during which the ON signal is output to only one upper arm switching element is calculated by reducing the delay time, and the current direction of the intermediate energized phase is the motor The inverter device according to claim 2, wherein in the direction of flowing into the inverter, the time during which an ON signal is output to only two upper arm switching elements is calculated by reducing the delay time. When only one of the upper arm switching elements is ON, the time when only two of the upper arm switching elements are ON The inverter device according to any one of claims 1 to 3, wherein each of the arm switching elements is replaced at a time when only one of the arm switching elements is ON. The inverter device according to any one of claims 1 to 4, wherein a current detector is provided in series with a lower arm switching element instead of the current detector. The inverter device according to any one of claims 1 to 4, wherein a current detector is provided between the inverter circuit and the motor instead of the current detector. The inverter device according to claim 1, wherein an effective value is calculated instead of an average value of direct current. The inverter apparatus as described in any one of Claims 1-7 which drives the motor of an electric compressor. The inverter apparatus of Claim 8 mounted in the said electric compressor. The inverter apparatus as described in any one of Claims 1-9 mounted in a vehicle.

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