JP2015198549A - Inverter driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a decrease in the operating voltage of an upper-arm-side driving circuit.SOLUTION: Upper-arm-side driving circuits (71, 72, 73) drive upper-arm-side switching elements (Q51a, Q52a, Q53a) composed of current-driving type semiconductor elements. Booster circuits (77, 78, 79) boost a DC voltage (Vdc2) according to a state of a motor (15). When the booster circuits (77, 78, 79) perform a boosting operation, bootstrap circuits (80, 81, 82) charge/discharge a voltage after boosting by the boosting circuits (77, 78, 79), thereby supplying the upper-arm-side driving circuits (71, 72, 73) with a voltage after boosting.

Description

  The present invention relates to a measure for preventing a decrease in operating voltage of an upper arm side drive circuit in an inverter drive device of an inverter circuit including an upper arm side switching element and a lower arm side switching element connected in series with each other.

  Some motors, which are driving sources for compressors and fans of an air conditioner, are driven by an inverter circuit as shown in Patent Document 1.

  The inverter circuit of Patent Document 1 is composed of an upper arm side switching element and a lower arm side switching element connected in series with each other, and an output of a drive circuit is connected to a control terminal of each switching element. In the upper arm side drive circuit of the upper arm side switching element, a boot capacitor for supplying an operating voltage to the circuit is connected in parallel to the circuit.

JP 2013-115954 A

  In recent years, instead of voltage-driven semiconductor elements such as insulated gate bipolar transistors, current-driven semiconductors such as high electron mobility transistors (HEMT) using GaN or heterojunction field effect transistors (HFETs) Attempts have been made to employ elements as switching elements.

  When a current-driven semiconductor element is employed as the upper arm side switching element, the current continues to flow from the output of the upper arm side driving circuit to the upper arm side switching element, so that the switching element is turned on. During this time, the boot capacitor continues to discharge the charged voltage to the upper arm side drive circuit using the charged voltage as the operating voltage, so that the operating voltage gradually decreases. The decrease in the operating voltage may make the operation of the upper arm side driving circuit unstable.

  Further, when the operating voltage decreases, the amount of current flowing to the control terminal of the upper arm side switching element also decreases. Then, the on-resistance increases, and the power loss of the switching element increases.

  The present invention has been made in view of such a point, and an object thereof is to prevent a decrease in operating voltage of the upper arm side drive circuit.

  The first invention drives an inverter circuit (50) including an upper arm side switching element (Q51a, Q52a, Q53a) and a lower arm side switching element (Q51b, Q52b, Q53b) connected in series to each other. Inverter drive is the target. The inverter drive device is connected to the control terminal of the upper arm side switching element (Q51a, Q52a, Q53a) composed of a current driven semiconductor element, and drives the upper arm side switching element (Q51a, Q52a, Q53a) The booster circuit (77,78) that can boost the predetermined voltage (Vdc2) according to the state of the upper arm side drive circuit (71,72,73) and the motor (15) connected to the inverter circuit (50) 79) and the booster circuit (77,78,79) perform the boost operation of the predetermined voltage (Vdc2), the boosted voltage that is boosted by the booster circuit (77,78,79) And a power storage circuit (80, 81, 82) for supplying the boosted voltage to the upper arm side drive circuit (71, 72, 73) by charging and discharging.

  Here, when required according to the state of the motor (15), the booster circuit (77, 78, 79) performs a boost operation, and the storage circuit (80, 81, 82) charges and discharges the boosted voltage. As a result, the boosted voltage that is higher than the predetermined voltage (Vdc2) is supplied as the operating voltage of the upper arm side drive circuit (71, 72, 73), so that the operating voltage is prevented from being lowered. Therefore, the upper arm side drive circuit (71, 72, 73) can operate stably.

  According to a second aspect of the present invention, in the first aspect, when the state of the motor (15) is when the motor (15) is started, the booster circuit (77, 78, 79) has the predetermined voltage (Vdc2) Is boosted.

  Here, when the motor (15) is started, a boosting operation is performed by the booster circuit (77, 78, 79), and the boosted voltage is supplied to the upper arm drive circuit (71, 72, 73). Therefore, when the motor (15) is started, even if the amount of current flowing from the upper arm side drive circuit (71, 72, 73) to the control terminal of the upper arm side switching element (Q51a, Q52a, Q53a) is relatively large, Lowering of the operating voltage of the upper arm side switching element (Q51a, Q52a, Q53a) is prevented.

  According to a third invention, in the first or second invention, when the state of the motor (15) is a state where the rotational speed of the motor (15) is lower than a predetermined rotational speed, the booster circuit (77, 78, 79) is characterized by boosting the predetermined voltage (Vdc2).

  Here, when the rotational speed of the motor (15) is lower than the predetermined rotational speed, the boosting operation by the booster circuit (77, 78, 79) is performed, and the boosted voltage is changed to the upper arm side drive circuit (71, 72, 73 ). Therefore, even when the amount of current flowing from the upper arm side drive circuit (71, 72, 73) to the control terminal of the upper arm side switching element (Q51a, Q52a, Q53a) is relatively large when the motor (15) rotates at a low speed. Thus, the operating voltage of the upper arm side switching elements (Q51a, Q52a, Q53a) is prevented from being lowered.

  In a fourth aspect based on the third aspect, the booster circuit (77, 78, 79) includes a coil (L77) and a switch (S77) connected in parallel to the coil (L77). It is. The step-up circuit (77, 78, 79) adjusts the amount of step-up of the predetermined voltage (Vdc2) by varying the duty ratio of the switch (S77) according to the number of rotations of the motor (15). And

  As described above, the booster circuit (77, 78, 79) can vary the boost amount according to the rotational speed of the motor (15) at that time with a simple configuration.

  According to a fifth invention, in the first or second invention, when the state of the motor (15) is a state in which the value of the current flowing through the motor (15) is higher than a predetermined value, The circuit (77, 78, 79) is characterized by boosting the predetermined voltage (Vdc2).

  Here, when the value of the current (Im) flowing through the motor (15) is higher than a predetermined value, the boosting operation by the booster circuit (77, 78, 79) is performed, and the boosted voltage is changed to the upper arm side drive circuit (71 72, 73). Therefore, when the value of the current (Im) flowing through the motor (15) is higher than the predetermined value, the upper arm side drive circuit (71, 72, 73) to the control terminal of the upper arm side switching element (Q51a, Q52a, Q53a) Even if the amount of current flowing to the side is relatively large, the operating voltage of the upper arm side switching elements (Q51a, Q52a, Q53a) can be prevented from decreasing.

  In a sixth aspect based on the fifth aspect, the booster circuit (77, 78, 79) includes a coil (L77) and a switch (S77) connected in parallel to the coil (L77). It is. The booster circuit (77, 78, 79) adjusts the boost amount of the predetermined voltage (Vdc2) by varying the duty ratio of the switch (S77) according to the value of the current flowing through the motor (15). Features.

  As described above, the booster circuit (77, 78, 79) can vary the boost amount according to the value of the current (Im) flowing through the motor (15) with a simple configuration.

  According to a seventh invention, in any one of the first to third inventions and the fifth invention, the booster circuit (77, 78, 79) is a charge pump circuit.

  In an eighth aspect based on any one of the first aspect to the seventh aspect, the booster circuit (77, 78, 79) has an output voltage of the power storage circuit (80, 81, 82) within a predetermined range. The boosting amount of the predetermined voltage (Vdc2) is adjusted so as to maintain the inside.

  Thereby, the value of the output voltage (Vb) of the power storage circuit (80, 81, 82), that is, the fluctuation of the operating voltage of the upper arm side drive circuit (71, 72, 73) is suppressed within a predetermined range. Therefore, the upper arm side drive circuit (71, 72, 73) can operate more stably.

  According to a ninth aspect of the present invention, in any one of the first to eighth aspects, when the booster circuit (77, 78, 79) does not perform the boost operation of the predetermined voltage (Vdc2), the power storage circuit (80, 81, 82) is characterized by charging and discharging the predetermined voltage (Vdc2).

  Thereby, the life of the power storage circuit (80, 81, 82) can be kept long, and the power loss due to the booster circuit (77, 78, 79) can be suppressed.

  According to the present invention and the seventh invention, since the operating voltage is prevented from being lowered, the upper arm drive circuit (71, 72, 73) can operate stably.

  According to the second invention, the third invention, and the fifth invention, the upper arm side drive circuit (71, 72, 73) controls the upper arm side switching element (Q51a, Q52a, Q53a). Even if the amount of current flowing to the terminals is relatively large, the operating voltage of the upper arm side switching elements (Q51a, Q52a, Q53a) can be prevented from decreasing.

  According to the fourth aspect of the present invention, the booster circuit (77, 78, 79) can vary the boost amount according to the rotational speed of the motor (15) at that time with a simple configuration.

  According to the sixth aspect of the invention, the booster circuit (77, 78, 79) has a simple configuration and the boost amount can be varied according to the value of the current (Im) flowing through the motor (15) at that time. Can be made.

  Further, according to the eighth aspect, the upper arm side drive circuit (71, 72, 73) can operate more stably.

  According to the ninth aspect of the invention, the life of the power storage circuit (80, 81, 82) can be kept long, and power loss due to the booster circuit (77, 78, 79) can be suppressed.

FIG. 1 is a schematic configuration diagram of a motor drive system including an inverter drive device. FIG. 2 is a diagram illustrating IV characteristics of a voltage-driven semiconductor element and a current-driven semiconductor element. FIG. 3 shows the switching element pair for one phase of the inverter circuit and the inverter driving device corresponding to this from FIG. 1, and specifically shows the configuration of the booster circuit. FIG. 4 shows a current path in the booster circuit when the switch is turned on. FIG. 5 shows a current path in the booster circuit when the switch is turned off. FIG. 6 is a flowchart showing the overall operation of the inverter driving apparatus according to the first embodiment. FIG. 7 is a timing chart showing a change with time in boot voltage and switch operation in the case of pattern 2 and pattern 3. FIG. 8 is a flowchart showing an operation performed by the inverter drive device so that the boot voltage is within a predetermined range. FIG. 9 illustrates a circuit configuration of a part of the inverter driving device according to the second modification of the first embodiment. FIG. 10 illustrates a configuration of a switching element pair for one phase of the inverter circuit according to the second embodiment and an inverter driving device connected thereto. FIG. 11 shows a current path in the booster circuit when the booster circuit is turned off. FIG. 12 shows a current path in the booster circuit during the first charging operation. FIG. 13 shows a current path in the booster circuit during the second charging operation. FIG. 14 is a flowchart showing the overall operation of the inverter driving apparatus according to the second embodiment. FIG. 15 is a timing chart showing changes over time in boot voltage and switch operation in the case of pattern 2 and pattern 3 in the second embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.
Embodiment 1
FIG. 1 is a schematic configuration diagram of a motor drive system (10) including an inverter drive device (70). As shown in FIG. 1, the motor drive system (10) includes a motor (15) and a power converter (20). The motor (15) is a drive source of a compressor included in the air conditioner. Therefore, the motor drive system (10) is mounted in the air conditioner.

  The motor (15) is, for example, a synchronous three-phase motor, and includes a stator, a rotor, a hall element, and the like.

<Configuration of power converter>
The power conversion device (20) converts input AC from the commercial power supply (90) into output AC. As shown in FIG. 1, the power conversion device (20) includes a rectifier circuit (30), a smoothing capacitor (C40), an inverter circuit (50), a current detection circuit (60), and an inverter drive device (70).

-Rectifier circuit-
The rectifier circuit (30) performs full-wave rectification on the AC voltage (Vac) from the commercial power supply (90). The rectifier circuit (30) is configured by connecting a plurality of (four in this embodiment) diodes (D31a, D31b, D32a, D32b) in a bridge shape.

-Smoothing capacitor-
One end of the smoothing capacitor (C40) is connected to the output side of the rectifier circuit (30), and the other end is connected to the GND wiring (L2). The smoothing capacitor (C40) is composed of, for example, an electrolytic capacitor, and smoothes the output voltage of the rectifier circuit (30).

-Inverter circuit-
The inverter circuit (50) is connected to both ends of the capacitor (C40) in the subsequent stage of the smoothing capacitor (C40). The inverter circuit (50) switches the voltage (Vdc1) across the smoothing capacitor (C40) to generate an AC drive voltage (SU, SV, SW) and outputs it to the motor (15). The inverter circuit (50) is configured by connecting a plurality (six in this embodiment) of switching elements (Q51a, Q52a, Q53a, Q51b, Q52b, Q53b) in a bridge shape.

  Specifically, two switching elements (Q51a, Q52a, Q53a, Q51b, Q52b, Q53b) are connected in series to form three switching element pairs (51, 52, 53). Each switching element pair (51, 52, 53) includes an upper arm side switching element (Q51a, Q52a, Q53a) and a lower arm side switching element (Q51b, Q52b, Q53b). In particular, switching elements (Q51a, Q52a, Q53a, Q51b, Q52b, Q53b) are voltage-driven types such as insulated gate bipolar transistors (IGBTs) and MOS-FETs (Metal Oxide Semiconductor Field Effect Transistors). The semiconductor device is not a semiconductor device but a current-driven semiconductor device such as a GaN-FET.

FIG. 2 shows the IV characteristics of the voltage-driven semiconductor element and the current-driven semiconductor element side by side. According to FIG. 2, in the voltage-driven semiconductor element, the collector-emitter voltage (V _CE ) changes from 1 V to 2 V when the gate voltage (V _GE ) is 20 V and when it is 15 V. The amount of increase in the collector current (Ic) at that time (that is, the slope of the graph when V _CE changes from 1 V to 2 V) is substantially the same. That is, even if the gate voltage (V _GE ) decreases from 20V to 15V, there is no significant change in the IV characteristics. On the other hand, in the current-driven semiconductor device, the drain current (I _DS ) that is not saturated even when the gate voltage (V _GS ) is decreased by 1.5 V from, for example, 2.5 V to 1.0 V is 20 A or more is 2 A. It changes to the characteristic which saturates below. Then, as the gate voltage (V _GS ) decreases, the on-resistance increases and the power loss also increases. Therefore, it can be said that in the current-driven semiconductor element, the change in the IV characteristic due to the fluctuation of the gate voltage (V _GS ) tends to be remarkable as compared with the voltage-driven semiconductor element.

  In the inverter circuit (50) of the present embodiment, as shown in FIG. 1, no reflux diode is provided. As shown in FIG. 2, unlike the IGBT, the current-driven semiconductor element has a property of allowing a current to flow while ensuring a withstand voltage in both directions.

-Current detection circuit-
The current detection circuit (60) detects a motor current (Im) that is a current that flows through the motor (15) that is being driven. The current detection circuit (60) includes a shunt resistor (R61) and the like. The shunt resistor (R61) is connected in series on the GND wiring (L2), which is the current path for the motor current (Im), and the motor current (Im) is detected based on the voltage across the shunt resistor (R61). The

-Inverter drive device-
The inverter drive device (70) is connected to the inverter circuit (50) and drives the inverter circuit (50). As shown in FIGS. 1 and 3 to 5, the inverter drive device (70) includes an upper arm side drive circuit (71, 72, 73), a lower arm side drive circuit (74, 75, 76), and a booster circuit (77). 78, 79), a bootstrap circuit (80, 81, 82) which is a power storage circuit, and a controller (86).

  3 partially extracts the switching element pair (51) for one phase of the inverter circuit (50) and the corresponding inverter driving device (70) from FIG. The configuration is specifically shown. 4 shows a current path in the booster circuit (77) when the switch (S77) is turned on, and FIG. 5 shows a current path in the booster circuit (77) when the switch (S77) is turned off. Yes. 4 and 5, the switch (S77) is simplified.

-Upper arm drive circuit-
Upper arm side drive circuit (71, 72, 73) is provided corresponding to each upper arm side switching element (Q51a, Q52a, Q53a), and drives the corresponding upper arm side switching element (Q51a, Q52a, Q53a) To do.

  The upper arm side drive circuit (71) is configured by connecting an upper Pch transistor (71a) and a lower Nch transistor (71b) in series with each other (71a, 71b). The base terminal is connected to the controller (86). The transistors (71a, 71b) connected in series with each other are connected to both ends of the boot capacitor (C80) of the bootstrap circuit (80), and a boot voltage (Vb) that is a voltage across the capacitor (C80) is applied. The

  A connection point between the Pch transistor (71a) and the Nch transistor (71b) is connected to a gate terminal which is a control terminal of the corresponding upper arm side switching element (Q51a). As described above, since the upper arm side switching element (Q51a) is composed of a current driven semiconductor element, when the upper arm side switching element (Q51a) is turned on, the upper arm side driving circuit (71) Current continues to flow to the gate terminal of the upper arm switching element (Q51a).

  The other upper arm side drive terminals (72, 73) have the same configuration as the upper arm side drive circuit (71).

-Lower arm drive circuit-
The lower arm side drive circuit (74, 75, 76) is provided corresponding to each lower arm side switching element (Q51b, Q52b, Q53b) and drives the corresponding lower arm side switching element (Q51b, Q52b, Q53b) To do.

  The lower arm side drive circuit (74) is configured by connecting an upper Pch transistor (74a) and a lower Nch transistor (74b) in series with each other (74a, 74b). The base terminal is connected to the controller (86). The transistors (74a, 74b) connected in series with each other are connected to both ends of the capacitor (C83), and the emitter terminal of the Pch transistor (74a) is connected to the booster circuit (77) via the resistor (R83) and the diode (D83). ) Is connected to the positive terminal of the DC power supply (Reg77). A connection point between the Pch transistor (74a) and the Nch transistor (74b) is connected to a gate terminal which is a control terminal of the corresponding lower arm side switching element (Q51b).

  The other lower arm side drive terminals (75, 76) have the same configuration as the lower arm side drive circuit (74).

-Booster circuit-
As shown in FIG. 1, the booster circuit (77, 78, 79) is provided corresponding to each upper arm side drive circuit (71, 72, 73), and has a predetermined voltage as shown in FIGS. Boost the DC voltage (Vdc2) of the corresponding DC power supply (Reg77).

  The booster circuit (77) is composed of a boost chopper circuit having a DC power supply (Reg77), a coil (L77), a switch (S77), a diode (D77), and a capacitor (C77). One end of the coil (L77) and the anode terminal of the diode (D77) are connected, and the other end of the coil (L77) is connected to the positive terminal of the DC power supply (Reg77). The capacitor (C77) is connected between the cathode terminal of the diode (D77) and the negative terminal of the DC power supply (Reg77). The switch (S77) is formed of a transistor, and is connected in parallel to the coil (L77), that is, to both ends of the capacitor (C77) between the coil (L77) and the diode (D77). The control terminal of the switch (S77) is connected to the controller (86).

  As shown in FIG. 4, when the switch (S77) is turned on, a current path is formed from the positive terminal of the DC power supply (Reg77) to the coil (L77), the switch (S77), and the negative terminal of the DC power supply (Reg77). As a result, energy is stored in the coil (L77).

  As shown in FIG. 5, when the switch (S77) is turned off, the current path of FIG. 4 is cut off. In this case, current flows from the DC power source (Reg77) to the coil (L77), the diode (D77), and the capacitor (C77), and the energy in the coil (L77) is stored in the capacitor (C77).

  4 and 5 is repeated, the voltage across the capacitor (C77) becomes higher than the DC voltage (Vdc), and the voltage across the capacitor is output as a boosted voltage. Further, since the amount of energy stored in the coil (L77) increases as the ON time of the switch (S77) increases, the booster circuit (77) adjusts the booster amount by changing the duty ratio of the switch (S77). be able to.

  When the booster circuit (77) does not perform the boosting operation, the switch (S77) continues to take the OFF state shown in FIG. In this case, the booster circuit (77) outputs a DC voltage (Vdc2).

  The other booster circuits (78, 79) have the same configuration as the booster circuit (77).

-Bootstrap circuit-
As shown in FIG. 1, the bootstrap circuit (80, 81, 82) is connected between each booster circuit (77, 78, 79) and each upper arm side drive circuit (71, 72, 73). It is provided corresponding to the arm side drive circuit (71, 72, 73). The bootstrap circuit (80, 81, 82) charges or discharges the DC voltage (Vdc2) or boosted voltage output from the booster circuit (77, 78, 79), thereby boosting the DC voltage (Vdc2) or boosted voltage. The voltage is supplied to the upper arm side drive circuit (71, 72, 73) as the operating voltage of the upper arm side drive circuit (71, 72, 73). Specifically, the bootstrap circuit (80, 81, 82) charges and discharges the post-boosting voltage during the boosting operation and the DC voltage (Vdc2) when the boosting operation is stopped.

  As shown in FIGS. 3 to 5, the bootstrap circuit (80) includes a diode (D80), a resistor (R80), and a boot capacitor (C80). The cathode terminal of the diode (D80) and one end of the resistor (R80) are connected, and the anode terminal of the diode (D80) is connected to the output of the booster circuit (77). A boot capacitor (C80) and an upper arm drive circuit (71) are connected in parallel to the other end of the resistor (R80).

  When the upper arm side switching element (Q51a) is off and the lower arm side switching element (Q51b) is on, a current path is formed from the boot capacitor (C80) to the lower arm side switching element (Q51b). (C80) charges the voltage output from the booster circuit (77). Next, when the upper arm side switching element (Q51a) is on and the lower arm side switching element (Q51b) is off, a current path is formed from the boot capacitor (C80) to the upper arm side drive circuit (71). The boot capacitor (C80) is discharged.

  Other bootstrap circuits (81, 82) have the same configuration as the bootstrap circuit (80).

-Controller-
The controller (86) is composed of a CPU and a memory, and includes a control terminal of the switch (S77) in each drive circuit (71, 72, 73, 74, 75, 76) and each booster circuit (77, 78, 79), current It is connected to the Hall element of the detection circuit (60) and motor (15). The controller (86) controls the drive of each drive circuit (71, 72, 73, 74, 75, 76) based on the operation command regarding the motor (15) from the overall control unit (not shown) of the air conditioner. I do. The controller (86) controls the boosting operation of each booster circuit (77, 78, 79) according to the detection result of the Hall element, the motor current (Im) as the detection result of the current detection circuit (60), and the like. I do.

<Operation of inverter drive device>
As described above, since the lower arm side switching elements (Q51b, Q52b, Q53b) are on during the charging operation of each bootstrap circuit (80, 81, 82), the lower arm side switching elements (Q51b, Q52b, An on-voltage due to on-resistance is generated in Q53b). The on-resistance increases as the temperature rises due to the motor current (Im) to the lower arm switching elements (Q51b, Q52b, Q53b) when the motor (15) rotates. If the step-up operation is not performed when the lower arm switching element (Q51b, Q52b, Q53b) is turned on, the difference between the DC voltage (Vdc2) and the on-voltage is booted due to the circuit configuration of FIGS. This is the voltage across the capacitor (C80), that is, the boot voltage (Vb). Therefore, the boot voltage (Vb) decreases as the ON voltage increases.

  In addition, each bootstrap circuit (80, 81, Q53a, Q52a, Q53a) is supplied to each of the bootstrap circuits (80, 81, If the charge amount of 82) is not sufficient, the boot voltage (Vb) is significantly reduced when the upper arm side switching elements (Q51a, Q52a, Q53a) are turned on.

The decrease in the boot voltage (Vb) may prevent the upper arm side switching elements (Q51a, Q52a, Q53a) from being driven in some cases. As shown in FIG. 2, the upper arm side switching elements (Q51a, Q52a, Q53a) composed of current-driven semiconductor elements are at least as the upper arm side switching elements (Q51a, Q52a, Q53a) are turned on. The threshold value of the control voltage to the required control terminal (V _{GS in} FIG. 2) is smaller than that of the voltage drive type. Therefore, when the boot voltage (Vb) decreases, the output voltage of the upper arm side drive circuit (71, 72, 73) using the boot voltage (Vb) as the operating voltage becomes lower than the threshold value, and the upper arm side switching element (Q51a, Q52a, Q53a) may not be driven.

Therefore, the inverter drive device (70) according to the first embodiment operates the booster circuit (77, 78, 79) in accordance with the state of the motor (15) where the boot voltage (Vb) may decrease. Prevent boot voltage (Vb) from dropping. Examples of the state of the motor (15) include the following patterns 1 to 3.
Pattern 1: When the motor (15) is in the activated state Pattern 2: When the rotational speed of the motor (15) is lower than the predetermined rotational speed Pattern 3: The value of the motor current (Im) is lower than the predetermined value When the state is high The patterns 1 to 3 can be said to be a state in which the load of the inverter circuit (50) is relatively high. In particular, in patterns 1 and 2, since the rotational speed of the motor (15) is increased, the time during which the upper arm side switching elements (Q51a, Q52a, Q53a) are turned on also increases. Then, the integrated amount of current from the upper arm side drive circuit (71, 72, 73) to the upper arm side switching elements (Q51a, Q52a, Q53a) and the motor current (Im) also increase. Pattern 3 includes an overcurrent state.

  Next, operation | movement of an inverter drive device (70) is demonstrated using FIG.6 and FIG.7. FIG. 6 is a flowchart showing the overall operation of the inverter drive device (70) according to the first embodiment. FIG. 7 is a timing chart showing temporal changes in the operation of the boot voltage (Vb) and the switch (S77) in the case of the pattern 2 and the pattern 3 described above.

  As shown in FIG. 6, when the controller (86) receives the operation command for starting the motor (15) (step S1), the controller (86) drives the inverter circuit (50) to start the motor (15). Each booster circuit (77, 78, 79) is turned on. Accordingly, the switch (S77) is repeatedly turned on and off at the first predetermined duty ratio, whereby each booster circuit (77, 78, 79) starts the boosting operation of the DC voltage (Vdc2) (step S2).

  Next, the controller (86) obtains the current rotational speed of the motor (15) from the detection result of the Hall element, and obtains the current motor current (Im) from the detection result of the current detection circuit (60). When the rotational speed of the motor (15) is lower than the predetermined rotational speed (Yes in step S3), or when the value of the motor current (Im) is higher than the predetermined value (Yes in step S4), the booster circuit (77, 78, 79) increase the duty ratio of the switch (S77) from the first predetermined duty ratio to a second predetermined duty ratio larger than this (step S5). As a result, the boost amount increases, so that the boot voltage (Vb) becomes higher than in the case of the first predetermined duty ratio.

  When the rotational speed of the motor (15) is higher than the predetermined rotational speed (No in step S3) and the value of the motor current (Im) is lower than the predetermined value (No in step S4), the duty of the switch (S77) The ratio is maintained at the first predetermined duty ratio.

  The operations in steps S3 to S5 are repeated until the synchronous operation (so-called normal operation) is started (No in step S6). After the synchronous operation is started (Yes in step S6), the booster circuit (77, 78, 79) is turned off, and the boosting operation is temporarily ended (step S7).

  Even after step S7, the controller (86) obtains the rotational speed and motor current (Im) of the motor (15) at that time from the latest detection result of the Hall element and the detection result of the current detection circuit (60). When the rotational speed of the motor (15) is lower than the predetermined rotational speed (Yes in step S8), or when the value of the motor current (Im) is higher than the predetermined value (Yes in step S11), the booster circuit (77, 78, 79) starts the boosting operation again (steps S9, S12), and varies the duty ratio of the switch (S77) according to the rotation speed of the motor (15) or the value of the motor current (Im) (step S10). , S13). As a result, the boost amount is adjusted so as to increase according to the rotation speed of the motor (15) or the value of the motor current (Im), and the boot voltage (Vb) becomes higher than in the case of the first predetermined duty ratio. .

  When the rotational speed of the motor (15) is higher than the predetermined rotational speed (No in Step S8) and the value of the motor current (Im) is lower than the predetermined value (No in Step S11), the booster circuit (77, 78 , 79) is turned off if the step-up operation is still in progress, and the step-up operation is stopped (step S14).

  The operations from step S8 to step S14 are repeated until the controller (86) receives an operation command to stop driving the motor (15) (No in step S15). When the controller (86) receives an operation command to stop driving the motor (15) (Yes in step S15), the inverter drive device (70) ends a series of operations.

  FIG. 7A shows an example of steps S8 to S10 and S14. In this figure, the step-up operation is performed while the rotational speed of the motor (15) falls below a predetermined rotational speed. In particular, the greater the difference between the rotational speed of the motor (15) and the predetermined rotational speed, the greater the duty ratio of the switch (S77). Conversely, the smaller the difference between the rotational speed of the motor (15) and the predetermined rotational speed, The duty ratio of the switch (S77) is decreasing.

  FIG. 7B shows an example of steps S11 to S14. In this figure, the boosting operation is performed while the peak value of the periodically flowing motor current (Im) exceeds a predetermined value. In particular, the greater the difference between the peak value of the motor current (Im) and the predetermined value, the greater the duty ratio of the switch (S77). Conversely, the smaller the difference between the motor current (Im) value and the predetermined value, the more the switch The duty ratio of (S77) is decreasing.

  7A and 7B, the boot voltage (Vb) is equal to or higher than the reference value.

  The reference value is determined, for example, as the value of the operating voltage of the upper arm side drive circuit (71, 72, 73) that is at least necessary to turn on the upper arm side switching element (Q51a, Q52a, Q53a). be able to. The predetermined rotation speed and the predetermined value can be determined, for example, as the rotation speed and motor current (Im) of the motor (15) when the boot voltage (Vb) is reduced to the reference value.

<Effect of Embodiment 1>
According to the inverter drive device (70) according to the first embodiment, when necessary according to the state of the motor (15), the booster circuit (77, 78, 79) performs a boost operation, and the boot capacitor (C80). Charges and discharges the voltage after boosting. This prevents a decrease in the boot voltage (Vb) that is the operating voltage of the upper arm side drive circuit (71, 72, 73). Therefore, the upper arm side drive circuit (71, 72, 73) can operate stably.

  In addition, when the motor (15) is started (pattern 1), when the rotation speed of the motor (15) is less than or equal to the predetermined rotation speed (pattern 2), and the value of the current (Im) flowing through the motor (15) If any one of the above cases (pattern 3) is established, the boost operation by the boost circuit (77, 78, 79) is performed, and the boosted voltage is applied to the upper arm side drive circuit (71, 72, 73). Supplied. Therefore, any one of the above patterns 1 to 3 is established, and even if the current flows from the upper arm side drive circuit (71, 72, 73) to the control terminal of the upper arm side switching element (Q51a, Q52a, Q53a). Even if the amount is relatively large, the boot voltage (Vb), which is the operating voltage of the upper arm side switching elements (Q51a, Q52a, Q53a), can be prevented from decreasing.

  The booster circuit (77, 78, 79) is composed of a boost chopper circuit. Since the booster circuit (77, 78, 79) has such a simple configuration, the duty of the switch (S77) included in the booster chopper circuit according to the rotation speed of the motor (15) or the value of the motor current (Im) By adjusting the ratio, the amount of boosting can be easily adjusted.

  Further, when the state of the motor (15) does not require the boosting operation, the boosting operation is not performed. In this case, since the bootstrap circuit (80, 81, 82) charges and discharges the DC voltage (Vdc2), the upper arm side drive circuit (71, 72, 73) has the DC voltage (Vdc2) as the operating voltage. Supplied. Therefore, the life of the bootstrap circuit (80, 81, 82) can be kept long and power loss in the booster circuit (77, 78, 79) can be suppressed.

<Modification 1 of Embodiment 1>
The inverter drive device (70) may further perform the operation of FIG. 8 after steps S10 and S13 of FIG. FIG. 8 is a flowchart showing the operation when the boost amount is adjusted so that the boot voltage (Vb) is within a predetermined range.

  When the operations in steps S10 and S13 in FIG. 6 are performed, the boot voltage (Vb) is detected in the inverter drive device (70) (step S21). When the boot voltage (Vb) is within the predetermined range, but the voltage difference between the boot voltage (Vb) and the upper limit voltage value within the predetermined range is smaller than the first voltage difference (Yes in step S22), the booster circuit (77, 78 , 79) adjusts the boost amount to decrease by reducing the duty ratio of the switch (S77) from the immediately preceding duty ratio (step S23). When the boot voltage (Vb) is within the predetermined range, but the voltage difference between the boot voltage (Vb) and the lower limit voltage value of the predetermined range is smaller than the second voltage difference (Yes in step S24), the booster circuit (77, 78 , 79) performs adjustment to increase the boosting amount by increasing the duty ratio of the switch (S77) from the immediately preceding duty ratio (step S25). The boot voltage (Vb) is within a predetermined range, the voltage difference between the boot voltage (Vb) and the upper limit voltage value is larger than the first voltage difference, and the voltage difference between the boot voltage (Vb) and the lower limit voltage value is When it is larger than the second voltage difference, the states of steps S10 and S13 are maintained.

  By this operation, the variation of the boot voltage (Vb), that is, the operating voltage of the upper arm side drive circuit (71, 72, 73) is suppressed within a predetermined range. Therefore, the upper arm side drive circuit (71, 72, 73) can operate more stably.

  The predetermined range can be determined, for example, as an operating voltage range in which the upper arm drive circuit (71, 72, 73) can operate without any problem. The first voltage difference and the second voltage difference are appropriately determined in consideration of the capacity of the boot capacitor (C80) and the like, and the increase amount and the decrease amount of the boost amount are appropriate so that the boot voltage (Vb) does not fall outside the predetermined range. Can be determined.

<Modification 2 of Embodiment 1>
As shown in FIG. 9, an upper arm side power supply circuit (87) may be further provided between the bootstrap circuit (80) and the upper arm side drive circuit (71). The input terminal and output terminal of the upper arm side power circuit (87) are connected to both ends of the boot capacitor (C80), and the output terminal is connected to the emitter terminal of the Pch transistor (71a) of the upper arm side drive circuit (71) Has been. The upper arm side power supply circuit (87) is, for example, a switching power supply, and converts the boot voltage (Vb) into a stable voltage and supplies it to the upper arm side drive circuit (71).

  On the lower arm side, a lower arm side power circuit (89) may be provided in the same manner as the upper arm side power circuit (87).

  Various power supply circuits (87, 89) may also be provided in the other phase of the inverter circuit (50).

<Modification 3 of Embodiment 1>
As shown in FIG. 1, the number of booster circuits provided in the inverter drive device (70) is one instead of three corresponding to the upper arm side drive circuits (71, 72, 73) for three phases. There may be. Since each bootstrap circuit (80, 81, 82) corresponding to each phase has a diode, one booster circuit can supply a boosted voltage to each power storage circuit (80, 81, 82). .
<< Embodiment 2 >>
In the second embodiment, the booster circuit (77, 78, 79) is constituted by a charge pump circuit.

  The first embodiment and the second embodiment are different in the configuration of the booster circuit (77, 78, 79), but the other configurations are the same as those in the first embodiment. Therefore, the configuration of the booster circuit (77, 78, 79), the boosting operation, and the operation of the inverter driving device (70) will be described below.

<Configuration of boosting circuit and boosting operation>
FIG. 10 is a diagram illustrating a configuration of a switching element pair (51) for one phase of the inverter circuit (50) according to the second embodiment and an inverter driving device (70) connected thereto. FIG. 11 shows a current path in the booster circuit (77) when the booster circuit (77) is turned off. 12 and 13 show current paths in the booster circuit (77) during the charging operation.

  As shown in FIGS. 10 to 13, the booster circuit (77) includes a DC power supply (Reg177), four switches (S177a, S177b, S177c, S177d), and two boost capacitors (C177a, C177b).

  Each of the four switches (S177a, S177b, S177c, S177d) is composed of a MOS-FET, and its control terminal is connected to the controller (86). Two switches (S177a, S177b) connected in series with each other and two switches (S177c, S177d) connected in series with each other are connected in parallel to the DC power supply (Reg177).

  Each terminal of the boost capacitor (C177a) (hereinafter referred to as a first boost capacitor) is connected to a connection point between the switches (S177a, S177b) and a connection point between the switches (S177c, S177d). Both ends of the boost capacitor (C177b) (hereinafter, second boost capacitor) are connected between the terminals of the switches (S177b, S177d) connected to the negative terminal of the DC power supply (Reg177).

  As shown in FIG. 11, when the booster circuit (77) is off, the switches (S177a, S177b) are turned on and the switches (S177c, S177d) are turned off. Then, a current path indicated by an arrow is formed, and the second boost capacitor (C177b) charges the DC voltage (Vdc2) of the DC power supply (Reg177). At this time, if the upper arm side switching element (Q51a) is turned off and the lower arm side switching element (Q51b) is turned on, the boot capacitor (C80) charges and discharges the DC voltage (Vdc2).

  When the booster circuit (77) is on, first, as shown in FIG. 12, the switches (S177a, S177d) are turned on and the switches (S177b, S177c) are turned off. Then, a current path indicated by an arrow in FIG. 12 is formed, and the first boost capacitor (C177a) charges the DC voltage (Vdc2) (first charging operation). Next, as shown in FIG. 13, the switches (S177a, S177d) are turned off and the switches (S177b, S177c) are turned on. Then, a current path indicated by an arrow in FIG. 13 is formed, and the second boost capacitor (C177b) has a DC voltage (Vdc2) of the DC power supply (Reg177) and a voltage across the first boost capacitor (C177a) (that is, DC voltage). Voltage (Vdc2)), that is, a voltage twice the DC voltage (Vdc2) is charged (second charging operation).

  As a result, the booster circuit (77) outputs a voltage that is twice the DC voltage (Vdc2) charged by the second boost capacitor (C177b) as the boosted voltage. At this time, if the upper arm side switching element (Q51a) is turned off and the lower arm side switching element (Q51b) is turned on, the boot capacitor (C80) charges and discharges the boosted voltage.

  The on / off cycle and duty ratio of each switch (S177a, S177b, S177c, S177d) may be constant, depending on the number of rotations of the motor (15) and the amount of motor current (Im). It may be variable. When at least one of the on and off cycles and the duty ratio is variable, the boost amount can be adjusted.

  The other booster circuits (78, 79) have the same configuration as the booster circuit (77).

<Operation of inverter drive device>
FIG. 14 is a flowchart showing the overall operation of the inverter drive device (70) according to the second embodiment. Here, in order to simplify the description, an example in which the ON / OFF cycle and the duty ratio of each switch (S177a, S177b, S177c, S177d) during the boosting operation are constant is taken.

  When the controller (86) receives the operation command for starting the motor (15) (step S41), the controller (86) drives the inverter circuit (50) to start the motor (15). The booster circuit (77, 78, 79) performs the boosting operation by repeatedly performing the first charging operation and the second charging operation until the synchronous operation (so-called normal operation) is started (No in step S43). (Step S42). During this time, the boot capacitor (C80) charges and discharges the boosted voltage, and the boosted voltage is supplied as the operating voltage to the upper arm side drive circuits (71, 72, 73).

  After the start of the synchronous operation (Yes in step S43), the booster circuit (77, 78, 79) is turned off and the boosting operation is temporarily ended (step S44). As a result, the DC voltage (Vdc2) is supplied as the operating voltage to the upper arm side drive circuits (71, 72, 73).

  After Step S44, when the rotational speed of the motor (15) is lower than the predetermined rotational speed (Yes in Step S45), or when the value of the motor current (Im) is higher than the predetermined value (Yes in Step S46), Each booster circuit (77, 78, 79) is turned on again to start a boost operation (step S47). As a result, the boosted voltage is again supplied to the upper arm side drive circuits (71, 72, 73).

  When the rotational speed of the motor (15) is higher than the predetermined rotational speed (No in Step S45) and the value of the motor current (Im) is lower than the predetermined value (No in Step S46), the booster circuit (77, 78 , 79) is turned off if the step-up operation is still in progress, and the step-up operation is stopped (step S48).

  The operations after step S45 are repeated until the controller (86) receives an operation command for stopping the driving of the motor (15) (No in step S49). When the controller (86) receives an operation command to stop driving the motor (15) (Yes in step S49), the inverter drive device (70) ends a series of operations.

  In FIG. 15, the change over time of the boot voltage (Vb) and the operation of each switch (S177a, S177b, S177c, S177d) is shown when the above steps S45 and S47 are performed (that is, in the case of pattern 2) and the above steps. The case where S46 and S47 are performed (that is, the case of pattern 3) is shown separately. In FIG. 15A, the boosting operation is performed while the rotational speed of the motor (15) is lower than the predetermined rotational speed. In FIG. 15B, the boosting operation is performed while the peak value of the periodically flowing motor current (Im) exceeds a predetermined value. 15A and 15B, the boot voltage (Vb) is equal to or higher than the reference value.

<Effect of Embodiment 2>
According to the inverter drive device (70) according to the second embodiment, even when the booster circuit (77, 78, 79) is configured by a charge pump circuit, when any one of the patterns 1 to 3 is established, The booster circuit (77, 78, 79) performs a boost operation, and the boot capacitor (C80) charges and discharges the boosted voltage. Therefore, as in the first embodiment, the boot voltage (Vb) is prevented from decreasing, and the upper arm side drive circuits (71, 72, 73) can operate stably.

  Further, when the step-up operation is not required as in the synchronous operation, the upper arm side drive circuit (71, 72, 73) is supplied with the DC voltage (Vdc2) as the operation voltage. Therefore, the life of the bootstrap circuit (80, 81, 82) can be kept long and power loss in the booster circuit (77, 78, 79) can be suppressed.

<Modification 1 of Embodiment 2>
As in FIG. 8, the on / off cycle and duty ratio of each switch (S177a, S177b, S177c, S177d) according to the value of the boot voltage (Vb) so that the boot voltage (Vb) remains within a predetermined range. At least one may be variable. As a result, the boost amount is adjusted, so that the upper arm side drive circuits (71, 72, 73) can operate more stably.

<Modification 2 of Embodiment 2>
Similarly to FIG. 9, an upper arm side power circuit (87) and a lower arm side power circuit (89) may be further provided.

<Modification 3 of Embodiment 2>
As in <Modification 3 of Embodiment 1>, the number of booster circuits provided in the inverter drive device (70) is three corresponding to the upper arm side drive circuits (71, 72, 73) for three phases. There may be only one.

  As described above, the present invention is useful for an inverter drive device of an inverter circuit including an upper arm side switching element and a lower arm side switching element.

15 Motor
50 Inverter circuit
Q51a, Q52a, Q53a Upper arm side switching element
Q51b, Q52b, Q53b Lower arm side switching element
71,72,73 Upper arm drive circuit
77,78,79 Booster circuit
L77 coil
S77 switch
80,81,82 Bootstrap circuit (storage circuit)
Vdc2 DC voltage (predetermined voltage)

Claims (9)

An inverter driving device for driving an inverter circuit (50) including an upper arm side switching element (Q51a, Q52a, Q53a) and a lower arm side switching element (Q51b, Q52b, Q53b) connected in series with each other. ,
Upper arm side drive that drives the upper arm side switching elements (Q51a, Q52a, Q53a) connected to the control terminal of the upper arm side switching elements (Q51a, Q52a, Q53a) composed of current driven semiconductor elements Circuit (71,72,73),
A booster circuit (77, 78, 79) capable of boosting a predetermined voltage (Vdc2) according to the state of the motor (15) connected to the inverter circuit (50);
When the booster circuit (77, 78, 79) performs the boost operation of the predetermined voltage (Vdc2), charge / discharge of the boosted voltage, which is the voltage boosted by the booster circuit (77, 78, 79), is performed. A storage circuit (80, 81, 82) for supplying the boosted voltage to the upper arm drive circuit (71, 72, 73),
An inverter drive device comprising: In claim 1,
An inverter driving device characterized in that the booster circuit (77, 78, 79) boosts the predetermined voltage (Vdc2) when the state of the motor (15) is when the motor (15) is activated. In claim 1 or claim 2,
When the motor (15) is in a state where the rotational speed of the motor (15) is lower than the predetermined rotational speed, the booster circuit (77, 78, 79) boosts the predetermined voltage (Vdc2). An inverter drive device characterized by that. In claim 3,
The booster circuit (77, 78, 79)
A step-up chopper circuit including a coil (L77) and a switch (S77) connected in parallel to the coil (L77),
Adjusting the boost amount of the predetermined voltage (Vdc2) by varying the duty ratio of the switch (S77) according to the rotation speed of the motor (15);
An inverter drive device characterized by that. In claim 1 or claim 2,
When the state of the motor (15) is such that the value of the current flowing through the motor (15) is higher than a predetermined value, the booster circuit (77, 78, 79) boosts the predetermined voltage (Vdc2). An inverter drive device characterized by that. In claim 5,
The booster circuit (77, 78, 79)
A step-up chopper circuit including a coil (L77) and a switch (S77) connected in parallel to the coil (L77),
According to the value of the current flowing through the motor (15), the duty ratio of the switch (S77) is varied to adjust the boost amount of the predetermined voltage (Vdc2).
An inverter drive device characterized by that. In any one of Claims 1-3 and Claim 5,
The booster circuit (77, 78, 79) is a charge pump circuit, and is an inverter drive device. In any one of Claims 1-7,
The booster circuit (77, 78, 79) adjusts the boost amount of the predetermined voltage (Vdc2) so that the output voltage of the power storage circuit (80, 81, 82) is kept within a predetermined range. To drive the inverter. In any one of Claims 1-8,
When the booster circuit (77, 78, 79) does not perform the boost operation of the predetermined voltage (Vdc2), the power storage circuit (80, 81, 82) charges and discharges the predetermined voltage (Vdc2). Inverter drive device.

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