JP6012211B2 - Motor drive device and air conditioner equipped with the same - Google Patents

Description

  The present invention relates to a motor drive device that detects an overcurrent.

  The motor of the compressor is supplied with a current converted into an alternating current by a motor drive circuit. Here, when the switching element of the motor drive circuit is turned on at an unintended timing due to the influence of noise or the like, the positive side and the negative side of the DC power supply are connected with a very small resistance. In this case, a large current flows instantaneously and a normal switching element is destroyed.

  In Patent Document 1, the switching elements of the lower arm are sequentially turned on for a short time in the initial stage of output, and the short circuit is confirmed by the short circuit current protection circuit, and the normal switching element can be prevented from being destroyed by the short circuit current protection circuit.

Japanese Patent Laid-Open No. 10-257777

  In compressors for air conditioners, permanent magnets made of inexpensive iron oxide (hereinafter referred to as “ferrite magnets”) are beginning to be used as substitutes for rare earth magnets. However, the ferrite magnet has a characteristic that the demagnetization start current is low at a low temperature. There is a risk of demagnetization when a current higher than the demagnetization start current flows through the ferrite magnet in the initial stage of operation when the motor temperature is low.

  Here, when the switching element of the motor driving circuit is turned on due to the influence of noise or the like, there is a possibility that a current flowing through the motor may be generated in addition to the current flowing through the upper and lower switching elements.

  The short-circuit current protection circuit of Patent Document 1 can turn off a switching element instantaneously when a current exceeding a set element protection threshold flows. Therefore, the flow of current due to conduction of the upper and lower stage switching elements can be prevented.

  However, since the demagnetization start current of the ferrite magnet is lower than the element protection threshold, the short-circuit current protection circuit of Patent Document 1 cannot prevent the demagnetization of the ferrite magnet due to the current flowing through the motor.

  The objective of this invention is providing the motor drive device which prevents the demagnetization of the magnet for motors.

In order to solve the above-described problem, a motor driving device of the present invention includes an inverter in which an upper switching element and a lower switching element are connected in series in a forward direction and a connection point is an output terminal to the motor, and the upper switching element. A capacitor connected to an emitter; current detection means for detecting a current flowing through the inverter; a motor protection threshold value that is lower than a demagnetization start current of a permanent magnet of the motor; and the current during initial charging of the capacitor. Current limiting means for limiting the current flowing to the motor when the current detected by the detection means exceeds the motor protection threshold; an element protection threshold that is higher than the motor protection threshold; and initial charging of the capacitor a current limiting circuit during the current detected by the detection means current stops the motor if it exceeds the element protection threshold, Serial and a charge reduction threshold which is lower than the motor protection threshold, at least a portion of the current limiting means is constituted by a microcomputer, the current limiting circuit is configured by hardware, detected by the current detecting means When the current exceeds the charging deceleration threshold, the duty ratio is decreased .

  A motor driving device that prevents demagnetization of a motor magnet can be provided.

The permanent magnet motor drive device in the 1st Embodiment of this invention. The hardware constitutions of the air conditioner outdoor unit in the 1st Embodiment of this invention. The hardware configuration of the inverter circuit in the 1st Embodiment of this invention. The schematic diagram at the time of the upper-lower switching element conduction | electrical_connection accompanying the switching element abnormality in the 1st Embodiment of this invention. The charge current change which flows at the time of capacitor charge in the 1st embodiment of the present invention. The charge current change which flows at the time of capacitor charge at the time of chopping in the 1st embodiment of the present invention. The schematic diagram when an electric current flows through a motor winding at the time of the switching element abnormality in the 1st Embodiment of this invention. The abnormal current detection flowchart at the time of the capacitor initial charge of the 1st Embodiment of this invention. The switching element drive sequence of the 1st Embodiment of this invention. The abnormal current detection flowchart at the time of capacitor initial charge of the 2nd Embodiment of this invention. The electric current which flows into a motor winding at the time of the normal of the 2nd Embodiment of this invention. The electric current which flows into the motor winding at the time of the upper stage switching element abnormality of the 2nd Embodiment of this invention.

  Hereinafter, embodiments will be described with reference to the drawings.

Hereinafter, the motor drive apparatus of Example 1 is demonstrated.
In the first embodiment, a permanent magnet type synchronous motor (hereinafter referred to as “PM motor”) is described as a motor. However, the present invention is not limited to this, and other synchronous motors (for example, a wound type synchronous motor or a reluctance motor) are used. Is also applicable.

  In FIG. 1, a motor driving DC power source 1 is constituted by an AC power source, a rectifier circuit, a transformer and the like (not shown).

  The motor drive DC power supply 1 supplies a DC voltage to the inverter unit 15 configured by switching elements connected in series in the upper and lower stages for each input phase of the PM motor 8. In order to rotate the PM motor 8, an AC applied voltage to be applied to the PM motor 8 is calculated by the microcomputer 105, converted into a pulse width modulated wave signal (hereinafter referred to as “PWM signal”), and an upper drive IC signal line 13 and the lower drive IC signal line 14, and then transmitted to the upper drive IC 203 and the lower drive IC 204.

  The upper drive IC 203 and the lower drive IC 204 turn ON / OFF the upper switching element 201 and the lower switching element 202 of each phase in accordance with the PWM signal, and apply an AC applied voltage to the PM motor 8.

  When an AC applied voltage is applied to the PM motor 8, a DC current (not shown) flows from the motor drive DC power supply 1 to the inverter unit 15, and this DC current is detected as a voltage generated across the current detection resistor 208. The voltage generated at both ends of the current detection resistor 208 is amplified by the amplifier 3, digitally converted by the A / D converter 4, information is taken into the microcomputer 105, and the current flowing through the winding of the PM motor 8 is reproduced as current. Reproduced in Part 5. In the normal rotation operation of the PM motor 8, a PWM signal is generated by performing feedback control on the target PWM frequency, for example, based on the current value reproduced by the current reproducing unit 5.

  FIG. 2 shows the main hardware configuration of the outdoor unit of the air conditioner. The AC power supplied from the commercial power source 101 is converted into a DC power source by the rectifier circuit 103, and a power source adapted to the rated voltage of each of the various control circuits is made by the power source circuit 104 constituted by a transformer and a semiconductor IC.

  The DC output voltage converted by the rectifier circuit 103 is reconverted into an AC output voltage by the compressor inverter circuit 111a and the blower inverter circuit 111b, and is supplied to the compressor motor 110 and the blower motor 112.

  FIG. 3 shows an inverter circuit of a brushless DC motor (hereinafter referred to as “three-phase brushless motor”) from which a mechanical contact portion such as a brush is removed.

  The output line 10, the output line 11, and the output line 12 of the inverter circuit are respectively connected to the U phase, the V phase, and the W phase that are motor input phases. Two switching elements for each phase are bridge-connected to the output line 10, the output line 11, and the output line 12.

  The upper switching element 201 includes a U-phase upper switching element 201u, a V-phase upper switching element 201v, and a W-phase upper switching element 201w, and the lower switching element 202 includes a U-phase lower switching element 202u, a V-phase lower switching element 202v, and a W-phase. It is comprised from the lower stage switching element 202w.

  The bases of the upper switching element 201 and the lower switching element 202 are connected to the upper driving IC 203 and the lower driving IC 204, respectively. The voltage of the control terminal is controlled by the upper stage driving IC 203 and the lower stage driving IC 204, and the upper stage switching element 201 and the lower stage switching element 202 are turned ON / OFF. The upper drive IC 203 includes a U-phase upper drive IC 203u, a V-phase upper drive IC 203v, and a W-phase upper drive IC 203w, and the lower drive IC 204 includes a U-phase lower drive IC 204u, a V-phase lower drive IC 204v, and a W-phase lower drive IC 204w. . The operations of the upper drive IC 203 and the lower drive IC 204 are controlled based on signals from the microcomputer 105, respectively.

  In order to drive the driving IC, an IC driving power source is required. Furthermore, the negative side of the IC drive power source needs to be connected to the emitter of each switching element.

  Since the IC driving power supply of the driving IC of the lower switching element 202 has a common potential at the emitters of the lower switching elements 202, the U-phase lower driving IC 204u, the V-phase lower driving IC 204v, and the W-phase lower driving IC 204w are provided by one power source. Can be driven.

  On the other hand, the IC driving power source of the upper driving IC 203 of the upper switching element 201 has a different potential at the emitter of the upper switching element 201, and therefore the total for each of the U-phase upper driving IC 203 u, the V-phase upper driving IC 203 v and the W-phase upper driving IC 203 w. Three power supplies are required.

  In such a case, since the power supply required for each inverter circuit increases, the power supply circuit configuration becomes enormous, resulting in an increase in cost and a reduction in effective substrate space. As this solution, for example, a method using a circuit provided with a capacitor 207 is known.

  Charging of the capacitor 207 is performed by turning on the lower switching element 202. In the rotation operation, the lower switching element 202 of each phase is always turned on sequentially so that the charging voltage of the capacitor 207 can be stably maintained.

The capacitor 207 is connected between the charging power source _Vcc and the emitter of the upper switching element 201 via a resistor 205 corresponding to the U phase, V phase, and W phase, and is charged when the corresponding lower switching element 202 is turned on. Is done. For example, when the U-phase lower stage driving IC 204u is turned on, the U-phase capacitor 207u is charged.

  Further, a diode 206 is inserted between the resistor 205 and each capacitor 207 so that the capacitor 207 does not discharge even when the potential of the emitter of the upper switching element 201 is high. By using such a method, the power supply of the driving IC of the upper switching element 201 can be reduced from three to one, and furthermore, if the driving IC of the lower switching element 202 and the rated voltage are the same, All drive ICs can be driven by a minimum of one power source.

  Here, the capacitor 207 is sequentially charged in accordance with the ON timing of the lower switching element 202 during the rotating operation, but it is necessary to perform a charging sequence in the initial stage before the rotating operation. Therefore, the capacitor 207 is charged by turning on only the lower switching element 202 immediately before the rotation operation.

  In the overcurrent detection circuit 209, when a current exceeding the abnormality determination threshold value is detected even once, a signal informing the drive IC of an abnormality is immediately input, and the drive IC is forcibly driven regardless of the microcomputer signal. To stop. The operation of the switching element becomes abnormal due to the influence of noise or the like, and the current flow can be stopped before the current flowing through the switching element becomes excessive. This protects the switching element. Since the abnormality determination threshold is determined by the value of the comparator and the fixed resistance, the threshold cannot be changed according to the operation status of the motor drive device.

  It is assumed that any one or more of the upper switching elements 201 of the inverter circuit is always in an ON state regardless of a signal from the microcomputer due to some influence such as component deterioration or noise.

  When the capacitor 207 is initially charged in this state, an unintended large current flows on the microcomputer side as the lower switching element 202 is turned on. In some cases, this large current flows in the motor winding. FIG. 6 is a simulation of the current flowing through the windings of the motor. The U-phase upper switching element 201u is always in the ON state. When the W-phase lower switching element 202w is turned on, an unintended current is generated on the microcomputer side. It flows through the motor winding as shown by the broken line.

  Conventional motors used in air conditioner compressors are made of neodymium or the like, and the demagnetization start current value is higher than the abnormal threshold current of the overcurrent detection circuit. Therefore, even when an excessive current flows through the motor winding, the prior art can detect an abnormality at the initial stage before the rotating operation without demagnetizing.

  However, compressors for air conditioners are beginning to use permanent magnets (hereinafter referred to as “ferrite magnets”) made of inexpensive iron oxide as a substitute for rare earth magnets such as neodymium. Ferrite magnets have the property of low demagnetization starting current at low temperatures. There is a risk of demagnetization when a current higher than the demagnetization start current flows through the ferrite magnet in the initial stage of operation when the motor temperature is low.

  Since the demagnetization start current of the ferrite magnet is lower than the element protection threshold, demagnetization of the ferrite magnet due to the current flowing through the motor cannot be prevented.

  Also, when protecting a motor with a low demagnetization start current, the abnormal threshold current of the overcurrent detection circuit can be set lower than the demagnetization start current to cope with demagnetization. However, it must be below the abnormal threshold current, and operation with a large motor output cannot be performed.

  In the first embodiment, the components are protected by two methods when the capacitor 207 is charged immediately before the rotation operation.

  The first is hardware protection composed of the current detection resistor 208 and the overcurrent detection circuit 209. This protection is mainly used to protect the switching element. For example, when the switching element is turned on at an unintended timing due to the influence of noise or the like, the positive side and the negative side of the motor driving DC power supply 1 are connected with an extremely small resistance in some cases. In this case, a large current flows instantaneously and a normal switching element is destroyed. To prevent this, hardware protection is performed.

  A switching element has an withstand capacity that defines the time until breakdown when a large current flows and an element absolute rated current value that defines a maximum allowable current. In other words, in order to prevent the switching element from being destroyed, an instantaneous current rise is quickly captured, and the switching element is turned off by applying a voltage to the switching element from the upper stage driving IC 203 and the lower stage driving IC 204 before the tolerance. The maximum value of the flowing current must be smaller than the element absolute rated current. Since the protection by the current detection resistor 208 and the overcurrent detection circuit 209 is entirely configured by hardware, the detection to the stop is performed in several microseconds, and a stop earlier than the withstand capability is possible. Moreover, it is possible to prevent element destruction by providing an element protection threshold smaller than the element absolute rated current value.

  The second is protection by software that has undergone processing in the microcomputer 105. This protection is mainly used to protect the motor. The abnormal current determination unit 6 in FIG. 1 compares the current reproduced by the current reproduction unit 5 with an overcurrent threshold in the microcomputer 105 (hereinafter referred to as “motor protection threshold”), and the reproduced current sets the motor protection threshold. When it exceeds, the bootstrap charging signal generator 7 is instructed to stop the signal. The bootstrap charging signal generator 7 instructed to stop the charging signal stops transmission of the charging signal to the upper driver IC 203 and the lower driver IC 204, and the initial charging process is processed in the form of an abnormal stop.

  The time from the detection of the current flowing through the inverter unit 15 by the current detection resistor 208 to the abnormal stop of the initial charging process through the process in the microcomputer 105 as described above is governed by the process in the microcomputer 105. It is about 10 to several hundred microseconds.

  Not only when charging the capacitor 207 immediately before the rotation operation, the PWM signal stop processing after the processing in the microcomputer 105 is limited to the one that does not affect even if it takes 10 to several hundred microseconds, Parts malfunction due to electrical time constant or heat capacity such as motor step-out protection, motor winding temperature protection, motor demagnetization protection, element temperature rise protection, compressor overtemperature protection, compressor pressure protection, etc. It takes a few milliseconds or more to reach such an influential region.

  Further, the PWM signal stop processing after the processing in the microcomputer 105 can freely handle the information in the microcomputer 105, so that the motor control information and various sensor information are used, or a complicated calculation formula is used for high accuracy. Overcurrent can be determined.

  Incidentally, the processing from the current detection resistor 208 to the amplifier 3, the amplifier 3 to the A / D converter 4, the A / D converter 4 to the current reproduction unit 5, and the bootstrap charging signal generation unit 7 to the upper stage driving IC 203 in FIG. 1. Since the processing up to the lower stage driving IC 204 has a hardware configuration, signal transmission is possible in a total of several microseconds.

  In the first embodiment, the protection by the above two methods is provided, and the element protection threshold is set to be higher than the motor protection threshold.

  As shown in FIG. 4, when the operation of the W-phase upper switching element 201w is not normal due to the influence of noise or the like and is always ON, the W-phase lower switching element 202w is turned on to charge the W-phase capacitor 207w. Then, a large current instantaneously flows through the W-phase upper switching element 201w and the W-phase lower switching element 202w. However, the protection by hardware can stop the drive signal and stop the flow of current before the W-phase upper switching element 201w and the W-phase lower switching element 202w are destroyed.

  As shown in FIG. 6, when the operation of the U-phase upper switching element 201u is not normal due to the influence of noise or the like and is always ON, the signal 16 transmitted from the microcomputer to the lower driver IC when the U-phase capacitor 207u is charged. Assuming that the W-phase lower switching element 202w is first turned ON by the energization method shown in FIGS. 5A and 5B. Then, the current through the motor winding flows according to the time constant of the motor winding, but the drive signal is stopped before the motor is demagnetized by the protection by software, and the current flow can be stopped.

  In a general motor drive device, only protection by hardware is used as a protection mechanism, so the element protection threshold is set to both the demagnetization start current value of the motor and the absolute rated current value of the switching element for cases where these large currents flow. It was necessary to set it lower.

  When a PM motor having a low motor demagnetization starting current is used, the element protection threshold value is also lowered, so that high-power operation of the motor becomes impossible.

  On the other hand, in the motor drive device of the first embodiment, it is not necessary to match the element protection threshold with the motor demagnetization start current. FIG. 7 is a flowchart up to the protection operation when the initial charging process of the capacitor is performed when the upper switching element 201 is always in the ON state due to the influence of noise or the like in the motor drive device of the first embodiment. . In the first embodiment, when the upper switching element 201 that is energized due to an abnormality and the lower switching element 202 that is energized are in the same phase, protection by hardware is performed without processing by the microcomputer 105. On the other hand, when the upper switching element 201 that is energized due to an abnormality and the lower switching element 202 that is energized are in different phases, protection by software by the microcomputer 105 is performed. As a result, the current level for protecting the switching element can be made equal to the conventional level, and the demagnetization of the motor can be prevented.

  Next, an example of a motor drive device capable of detecting and stopping an abnormality during charging processing of the capacitor 207 immediately before the rotation operation will be described not only when the upper switching element 201 is abnormal but also when the lower switching element 202 is abnormal.

FIG. 8 is an example of a time chart of a bootstrap charging signal transmitted from the microcomputer 105 when the capacitor 207 is charged immediately before the rotation operation of the motor driving device according to the first embodiment. For example, when the charging process for the capacitor 207 is completed at time t ₄ , even if one of the lower switching elements 202 in FIG. Since it is not turned ON, a large current does not flow during the charging process for the capacitor 207 immediately before the rotating operation.

  However, in the subsequent positioning sequence, a control signal is sent from the microcomputer 105 to flow a current that gives a rotating magnetic field to the PM motor 8. Therefore, while the lower switching element 202 is abnormal, an unintended current flows through the motor winding when the upper switching element 201 is turned on, and an unintended rotation (reverse rotation or the like) magnetic field may be generated.

Therefore, in the first embodiment once charging the capacitor 207 at time t ₁ ~t _4, simultaneously causing ON only all the upper stage switching element 201 between times t ₄ ~t _5. At this time, if any one of the lower switching elements 202 is in an ON state due to an abnormality, a large current flows instantaneously without passing through the motor winding, so that the overcurrent detection circuit 209 performs processing without the microcomputer 105. The protection operation can be reached.

When the lower stage switching element 202 is normal, since the capacitor 207 by the ON of the upper stage switching element 201 between time t ₄ ~t ₅ is discharged, the time t _5, time t _6, time t ₁ at time t _7, the time Processing similar to that at time t ₂ and time t ₃ is performed to charge the capacitor 207.

  In charging the capacitor 207, the lower switching elements 202 of the respective phases are turned on at different timings. However, the present invention is not limited to this, and the present invention can be implemented even when the lower switching elements 202 of the respective phases are simultaneously turned on.

  As described above, it is possible to determine abnormality of all the switching elements before entering the sequence in which the PM motor 8 rotates, and charging of the capacitor 207 can be properly performed in the normal state.

  In the case of motors using ferrite magnets, the demagnetization start current at low temperatures is low, so a warm-up operation is performed at a low output for a certain period of time until the motor warms up, and then the motor protection threshold is raised after warming up. May be.

  Alternatively, the motor temperature may be measured, and the motor protection threshold may be varied according to the motor temperature. Since the demagnetization start current changes according to the motor temperature, it is possible to obtain a wide motor output by changing the motor protection threshold in accordance with the demagnetization start current. These motor protection thresholds are possible because they are software protected.

  As an application example of the motor drive device, a drive device for a compressor motor can be cited. By providing an element protection threshold and a motor protection threshold during charging of the capacitor 207 immediately before the compressor rotation operation, if a current larger than the motor protection threshold and smaller than the element protection threshold is detected, an overcurrent detection configured by hardware Protection operation in the circuit does not occur, it is determined that the demagnetization overcurrent is detected by the abnormal current determination unit for demagnetization protection, a stop signal is sent from the bootstrap charge signal generation unit to the drive IC, and the operation of the inverter unit stops To do.

  In this case, a current exceeding the motor protection threshold flows through the current detection resistor 208 due to the reaction speed of the microcomputer 105. However, since the motor current changes slowly according to the time constant, the motor has a demagnetizing current or more. Current can be prevented from flowing.

  As described above, according to the present invention, it is possible to appropriately protect the element and protect the motor from demagnetization regardless of the magnitude of the demagnetizing current and the element absolute rating. In addition, since the demagnetization current of the motor varies depending on the material, by determining the motor protection threshold value for each motor, the element protection and motor reduction can be properly performed when charging the capacitor 207 immediately before the rotation operation for all motors. Magnetic protection can be performed.

  Although the motor drive device is different for each compressor and blower, charging to the capacitor 207 immediately before the rotating operation can be performed with the same power source if the power supply rated voltage of the drive IC in each drive device is the same. Therefore, it is possible to operate the drive IC normally while suppressing the volume of the power source. Also. For the charging process and protection operation, if the PWM frequency, chopping duty ratio, single charging time, motor protection threshold, charging deceleration threshold, etc. are stored in the external storage medium as parameters of each system, the operation of the corresponding system In this case, by calling parameters using the same microcomputer and the same routine program, it is possible to control the capacitor charging before the rotation operation and the protection operation of any motor drive device.

  In order to stably supply the AC applied voltage to the PM motor 8, it is necessary to stably supply power to the upper drive IC 203 and the lower drive IC 204 that apply the ON / OFF voltage to the switching element of the inverter unit 15. .

  In addition to the stable supply of the AC applied voltage to the PM motor 8, the first embodiment adopts a method of connecting the bootstrap charging circuit 2 to the power supply unit of the upper drive IC 203 in order to realize a low cost and a small board area. doing.

Further, the charging power source V _CC can be made common if the rated voltages of the upper stage driving IC and the lower stage driving IC are equal, and the upper stage driving IC 203 can be operated by the charging voltage of the capacitor 207.

  In addition, because the influence of disturbance such as gusts is large on the blower motor, the induced voltage generated in the motor due to the disturbance is detected by the rotor position detector 113, and control is performed in consideration of the disturbance situation. You can also.

Moreover, IGBT with a protection diode is used for a switching element, for example.
In some cases, the output voltage of the power supply circuit 104 is a positive motor drive DC power supply _VDD, and the output voltage of the power supply circuit 104 is a DC voltage made by a smoothing circuit.

  In addition, not only immediately before the rotation operation of the motor drive device, but also when the thermo-off or abnormally stops, the short-circuit check operation that turns the switching element on for a short time is performed, and the hardware and software of the present invention during the short-circuit check operation Protection may be provided.

  In the second embodiment, when the upper switching element 201 is in an ON state due to some abnormality such as deterioration and a large current flows through the PM motor 8, a motor drive capable of performing a motor protection operation with a more time constant. An example of the apparatus will be described.

  FIG. 9 is a flowchart until the switching element according to the second embodiment is in an ON state due to some abnormality such as deterioration and is stopped due to a protection operation.

  In the second embodiment, a charging deceleration threshold value lower than the motor protection threshold value is provided when the protection operation is performed via the processing in the microcomputer 105, and charging is performed when the current flowing through the current detection resistor 208 is taken into the microcomputer 105. When the deceleration threshold is exceeded, a chopping rate (hereinafter referred to as “duty ratio”) of the PWM signal chopped for each PWM cycle is lowered to take measures to suppress the rise of the current flowing through the motor.

  FIG. 10 shows the bootstrap charging signal and the current Id flowing through the current detection resistor when the capacitor 207 is normally charged without any abnormality of the switching element in the second embodiment. FIG. 11 shows the bootstrap charging signal and the current Id flowing through the current detection resistor when a current having a time constant passing through the motor winding flows when the upper switching element 201 is abnormal.

In the second embodiment, as shown in FIG. 11, when the current Id reaches the charge deceleration threshold value, the duty ratio of the PWM signal is reduced to suppress the rising slope of the current. Furthermore, the time period during which only the W phase is charged is from time t ₁ to time t ₂ is designated as time t ₁ to time t ₂ ′. Thereby, the rise of the current flowing through the motor can be suppressed.

  In the second embodiment, by reducing the duty ratio of the PWM signal and reducing the pulse width, the reaction time from detection to stop is shortened, and the motor protection threshold is set to a high value with a low possibility of erroneous detection in order to suppress the rise of current. Can be set.

  Furthermore, it is desirable to set the duty ratio of the PWM signal after detecting the charge deceleration threshold in the second embodiment according to the minimum pulse width that can be detected by the overcurrent detection circuit. It is desirable that the time until the drive IC is turned on is increased in accordance with the decrease rate of the duty ratio, assuming that the charge deceleration threshold value is erroneously detected due to noise or the like.

  FIG. 9 is a flowchart based on the motor drive device of the second embodiment, but it can also be applied to a capacitor charge signal that does not particularly detect the abnormality of the lower switching element as shown in FIG. 5A. On the other hand, as shown in FIG. 5B, a PWM signal chopped every PWM period is used.

  Further, in the protection operation via the processing in the microcomputer 105, the operation timing is often combined with the ON timing of the PWM signal given from the microcomputer 105 to the drive IC. For example, it is detected at the middle position of the ON signal pulse. If the motor protection threshold is exceeded, processing is performed such that the next and subsequent pulses are not output. That is, even if a current exceeding the motor protection threshold is detected, the current continues to flow for a time that is ½ of the pulse width. Therefore, the margin between the motor protection threshold and the motor demagnetization start current must be set to be equal to or more than the current that flows during a time half the pulse width.

  As described above, the motor driving device of the present invention is connected to the inverter in which the upper switching element and the lower switching element are connected in series in the forward direction and the connection point is the output terminal to the motor, and the emitter of the upper switching element. Capacitor, current detection means for detecting the current flowing through the inverter, motor protection threshold lower than the demagnetization start current of the permanent magnet of the motor, and the current calculated by the current calculation means during initial charging of the capacitor is the motor protection threshold. Current limiting means for limiting the current flowing to the motor when the current exceeds the limit.

  Furthermore, the motor driving device of the present invention includes a current limiting circuit that stops the motor when the current detected by the current detecting means during the initial charging of the capacitor exceeds the element protection threshold, and the element protection threshold is the motor protection threshold. Higher than.

  Furthermore, in the motor drive device of the present invention, the element protection threshold is higher than the demagnetization start current of the permanent magnet of the motor.

  Furthermore, in the motor drive device of the present invention, the motor protection threshold changes according to the temperature of the motor.

  Furthermore, the motor drive device of the present invention includes a microcomputer having current calculation means.

  Furthermore, the motor drive device of the present invention has a charging deceleration threshold value lower than the motor protection threshold value, and reduces the duty ratio of the inverter when the current calculated by the current calculation means exceeds the charging deceleration threshold value.

  Furthermore, the motor drive device of the present invention lengthens the initial charging time for the capacitor according to the decreasing rate of the duty ratio.

  Furthermore, the motor driving device of the present invention performs the initial charging to the capacitor by turning on the lower switching element, and turns off all the lower switching elements after the initial charging to the capacitor and before driving the motor. And all the upper switching elements are turned ON.

  Furthermore, the air conditioner of this invention drives a compressor with a motor drive device.

DESCRIPTION OF SYMBOLS 1 DC power supply for motor drive 2 Bootstrap charge circuit 3 Amplifier 4 A / D converter 5 Current reproduction part 6 Abnormal current determination part 7 Bootstrap charge signal generation part 8 PM motor 13 Upper stage drive IC signal line 13u U phase upper stage drive IC Signal line 13v V phase upper stage drive IC signal line 13w W phase upper stage drive IC signal line 14 Lower stage drive IC signal line 14u U phase lower stage drive IC signal line 14v V phase lower stage drive IC signal line 14w W phase lower stage drive IC signal line 15 Inverter Unit 16 Signal 100 transmitted from microcomputer to lower drive IC Power module 101 Commercial power supply 102 Reactor 103 Rectifier circuit 104 Power supply circuit 105 Microcomputer 106 Outdoor communication circuit 107 Temperature sensor 108 Expansion valve unit 109 Expansion valve drive circuit 110 Motor for compressor 111 Inverter circuit 11 a Compressor inverter circuit 111b Blower inverter circuit 112 Blower motor 113 Rotor position detector 201 Upper switching element 201u U phase upper switching element 201v V phase upper switching element 201w W phase upper switching element 202 Lower switching element 202u U phase lower switching Element 202v V-phase lower switching element 202w W-phase lower switching element 203 Upper stage driving IC
203u U-phase upper stage drive IC
203v V-phase upper stage drive IC
203w W-phase upper stage drive IC
204 Lower stage drive IC
204u U phase lower stage drive IC
204v V-phase lower stage drive IC
204w W phase lower stage drive IC
205 Resistor 206 Diode 207 Capacitor 207u U-phase capacitor 207v V-phase capacitor 207w W-phase capacitor 208 Current detection resistor 209 Overcurrent detection circuit

Claims (8)

An inverter in which the upper switching element and the lower switching element are connected in series in the forward direction, and the connection point is an output terminal to the motor;
A capacitor connected to the emitter of the upper switching element;
Current detecting means for detecting a current flowing through the inverter;
A motor protection threshold value that is lower than the demagnetization start current of the permanent magnet of the motor;
Current limiting means for limiting the current flowing to the motor when the current detected by the current detection means during initial charging of the capacitor exceeds a motor protection threshold;
An element protection threshold that is higher than the motor protection threshold;
A current limiting circuit for stopping the motor when the current detected by the current detecting means during initial charging of the capacitor exceeds the element protection threshold;
A charge deceleration threshold that is lower than the motor protection threshold,
At least a part of the current limiting means is constituted by a microcomputer,
The current limiting circuit is configured by hardware,
A motor drive device characterized by lowering a duty ratio when the current detected by the current detection means exceeds the charge deceleration threshold. An inverter in which the upper switching element and the lower switching element are connected in series in the forward direction, and the connection point is an output terminal to the motor;
A capacitor connected to the emitter of the upper switching element;
Current detecting means for detecting a current flowing through the inverter;
A motor protection threshold value that is lower than the demagnetization start current of the permanent magnet of the motor;
Current limiting means for limiting the current flowing to the motor when the current detected by the current detection means during initial charging of the capacitor exceeds a motor protection threshold;
A motor driving apparatus characterized in that an initial charging time for the capacitor is lengthened in accordance with a decreasing rate of the duty ratio. The lower stage switching element is turned on to perform initial charging to the capacitor,
3. The motor according to claim 2, wherein all of the lower switching elements are turned off and all of the upper switching elements are turned on after the initial charging of the capacitor and before driving of the motor. Drive device. The motor driving apparatus according to claim 2, wherein the motor protection threshold changes according to a temperature of the motor. A charge deceleration threshold value that is lower than the motor protection threshold value,
5. The motor drive device according to claim 4, wherein the duty ratio is lowered when the current detected by the current detection means exceeds the charge deceleration threshold value. An inverter in which the upper switching element and the lower switching element are connected in series in the forward direction, and the connection point is an output terminal to the motor;
A capacitor connected to the emitter of the upper switching element;
Current detecting means for detecting a current flowing through the inverter;
A motor protection threshold value that is lower than the demagnetization start current of the permanent magnet of the motor;
Current limiting means for limiting the current flowing to the motor when the current detected by the current detection means during initial charging of the capacitor exceeds a motor protection threshold;
A charge deceleration threshold that is lower than the motor protection threshold,
The lower stage switching element is turned on to perform initial charging to the capacitor,
After the initial charge to the capacitor and before driving the motor, turn off all the lower switching elements, and turn on all the upper switching elements,
A motor drive device that reduces the duty ratio when the current detected by the current detection means exceeds the charge deceleration threshold.   The air conditioner according to any one of claims 1 to 6, further comprising a compressor driven by the motor driving device, a condenser, an expansion device, and an evaporator. The current limiting means limits the current flowing to the motor when the current detected by the current detection means during initial charging of the capacitor exceeds a motor protection threshold;
8. The air conditioner according to claim 7, wherein the current limiting circuit stops the motor when a current detected by the current detection unit exceeds an element protection threshold during initial charging of the capacitor.