JP6711116B2 - Electric motor drive - Google Patents

Description

The present invention relates to a motor drive device, and more particularly to a motor drive device including a current detection circuit that detects a current from an inverter circuit.

BACKGROUND ART Conventionally, there is known an electric motor drive device including a current detection circuit that detects a current from an inverter circuit (see, for example, Patent Document 1).

The electric motor drive device described in Patent Document 1 includes an inverter circuit, and a current detection circuit (effective value calculation unit) that detects three-phase output current output from the inverter circuit to a load such as an electric motor. Further, the electric motor drive device described in Patent Document 1 monitors the fluctuation rate of the current value (effective value) of the three-phase output currents detected by the current detection circuit, so as to detect the fluctuation between the inverter circuit and the load. It is configured to detect (determine) the presence or absence of disconnection (phase loss).

JP-A-4-236123

Here, in the electric motor drive device described in Patent Document 1, the presence or absence of disconnection (open phase) is determined by monitoring the fluctuation rate of the current value (effective value) of the output currents of the three phases. There is a problem that it takes time from the occurrence to the detection of the disconnection.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electric motor drive device capable of promptly detecting a disconnection between an inverter circuit and a load. Is to provide.

An electric motor drive device according to one aspect of the present invention includes an inverter circuit that outputs an alternating current to a load, a pulse width modulator that controls the on/off time of a PWM signal for driving the inverter circuit, and an output from the inverter circuit to the load. A current detection circuit for detecting an alternating current of at least two phases out of three phases; a current command section for controlling the current value output from the inverter circuit to the load to a predetermined current value; and a current command section Of the PWM signal output from the pulse width modulation unit, which is output based on the signal from the current detection circuit and the detection signal of the current detection circuit, is equal to or longer than a predetermined threshold time , And a control unit for detecting a disconnection state between them.

In the motor drive device according to one aspect of the present invention, as described above, the control unit is configured to detect the disconnection state between the inverter circuit and the load based on the PWM signal from the pulse width modulation unit. Accordingly, the current value detected by the current detection circuit can be calculated, and the disconnection between the inverter circuit and the load can be detected without monitoring the fluctuation rate of the current value. Here, the PWM signal changes within a relatively short time after the disconnection occurs with respect to the time required to calculate the current value and monitor the variation rate of the current value. Therefore, by detecting the disconnection state based on the PWM signal, the disconnection between the inverter circuit and the load can be promptly detected.

Further , the disconnection can be detected only by comparing the ON time of the PWM signal with a predetermined threshold time. As a result, the disconnection can be detected more easily than in the case where the current value is calculated and the fluctuation rate of the current value is monitored.

In this case, preferably, the control unit outputs the detection signal of the current detection circuit that is smaller than the signal from the current command unit and is output, and the on-time of the PWM signal from the pulse width modulation unit. If the predetermined threshold time is exceeded, it is determined that there is a disconnection between the inverter circuit and the load. Here, when the disconnection occurs, the detection signal of the current detection circuit becomes smaller, so that the detection signal of the current detection circuit becomes smaller than the signal from the current command unit. Therefore, with the above configuration, when a disconnection occurs, the PWM signal from the pulse width modulation unit is turned on for a long time, so that the disconnection can be easily detected.

In the motor drive device that detects disconnection based on the ON time of the PWM signal, each of the inverter circuit and the current detection circuit is preferably configured to be supplied with power from a common power source. The disconnection between the load and the load reduces the supply power of the common power supply, and thus the detection signal of the current detection circuit is reduced. According to this structure, when the detection signal of the current detection circuit becomes small and the control is performed so as to increase the output current of the inverter circuit, the power supply of the common power supply that supplies power to the inverter circuit. Since the capacity is lowered, the output power of the inverter circuit does not increase. Therefore, the PWM signal which is a signal for controlling the output power of the inverter circuit to increase is turned on. Thereby, the disconnection between the inverter circuit and the load can be easily detected based on the length of the ON time of the PWM signal.

In this case, preferably, the inverter circuit includes a bootstrap circuit having a bootstrap capacitor that is a common power source for the inverter circuit and the current detection circuit, and a semiconductor that constitutes an upper arm whose on/off is controlled in synchronization with the PWM signal. The bootstrap circuit includes an element and a semiconductor element that forms a lower arm. The bootstrap circuit discharges the bootstrap capacitor when the PWM signal is on, and the bootstrap circuit when the PWM signal is off. The capacitor is configured to be charged, and the disconnection between the inverter circuit and the load reduces the charge of the bootstrap capacitor, so that the detection signal of the current detection circuit is reduced. It is configured. According to this structure, by using the bootstrap capacitor as the common power supply, the cost can be reduced as compared with the case of using the external power supply as the common power supply. Further, since the bootstrap capacitor discharges the charged electric charge more easily than an external power source or the like, it is possible to easily detect disconnection due to the length of the ON time of the PWM signal.

In the electric motor drive device according to the above aspect, preferably, the control unit is configured to notify the outside when the disconnection between the inverter circuit and the load is made. According to this structure, the user is notified of the disconnection. Therefore, when the disconnection occurs, the user can recognize the disconnection, and the user can promptly stop the circuit control.

According to the present invention, as described above, it is possible to provide the electric motor drive device capable of promptly detecting the disconnection between the inverter circuit and the load device.

It is a figure showing composition of an electric motor drive by one embodiment of the present invention. It is a figure for demonstrating the structure of the bootstrap circuit of the electric motor drive device by one Embodiment of this invention. FIG. 6 is a diagram for explaining control in a pulse width modulation unit of the motor drive device according to the embodiment of the present invention. FIG. 4 is a diagram showing a PWM signal from a pulse width modulation unit of the motor drive device according to the embodiment of the present invention. FIG. 6 is a diagram for explaining a control flow of wire breakage detection of the electric motor drive device according to the embodiment of the present invention.

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

[This embodiment]
First, the configuration of the electric motor drive device 100 according to the present embodiment will be described with reference to FIG.

(Circuit configuration of the motor drive device)
As shown in FIG. 1, the motor drive device 100 is configured to be supplied with an alternating current of three phases (U phase, V phase, W phase) from an AC power supply 1. Further, the electric motor drive device 100 includes a rectifying device 2 that rectifies the AC current from the AC power supply 1. Further, the motor drive device 100 is provided with a smoothing capacitor 3 that converts an alternating current into a direct current. Further, an inverter circuit 4 for converting a direct current into an alternating current is connected between both ends of the rectifying device 2.

Further, the inverter circuit 4 is configured so that each of the three-phase alternating currents is output to the load 101 such as an electric motor through separate wirings. Specifically, the U-phase current is output from the inverter circuit 4 to the load 101 via the U-phase wiring 4a. Further, the V-phase current is output from the inverter circuit 4 to the load 101 via the V-phase wiring 4b. In addition, the W-phase current is output from the inverter circuit 4 to the load 101 via the W-phase wiring 4c.

Further, the motor drive device 100 is provided with a current detection circuit 5 that detects the respective current values of the U-phase current and the W-phase current output from the inverter circuit 4. Further, the current detection circuit 5 is configured such that power is supplied from a bootstrap capacitor 42a described later. The bootstrap capacitor 42a also functions as a power supply that supplies power to the gate drive circuit of each switching element that forms the upper arm of the inverter circuit 4. Specifically, the current detection circuit 5 is supplied with power from the bootstrap capacitor 42a via the wiring 6. The bootstrap capacitor 42a is an example of the "common power supply" in the claims.

Further, the electric motor drive device 100 includes a current command unit 7, a current adjusting unit 8, and a PWM signal creating unit 9. Further, the motor drive device 100 is provided with an adder 102. The current adjusting unit 8 calculates a voltage command value such that the deviation between the current command value from the current command unit 7 obtained by the adder 102 and the current detection value from the current detection circuit 5 becomes zero. The PWM signal generation unit 9 generates the PWM signal 9a based on the comparison between the voltage command value (modulation signal) (see FIG. 3) from the current adjustment unit 8 and the carrier wave (for example, triangular wave) (see FIG. 3), This PWM signal 9a is output to the gate drive circuit of each switching element of the inverter circuit 4. The PWM signal creation unit 9 is an example of the “pulse width modulation unit” in the claims.

Further, in the PWM signal creation unit 9, when the magnitude of the modulation signal (see FIG. 3) is larger than the magnitude of the carrier wave (see FIG. 3), the PWM signal 9a (see FIG. 4) is turned on. When the magnitude of the modulation signal is equal to or smaller than the magnitude of the carrier wave, the PWM signal 9a is turned off.

Here, in the present embodiment, the control unit 10 that detects the disconnection state between the inverter circuit 4 and the load 101 based on the PWM signal 9a (see FIG. 4) from the PWM signal creation unit 9 is provided. .. Specifically, the control unit 10 is configured to detect the disconnection state based on the length of time that the PWM signal 9a is in the on state (hereinafter referred to as the on time). The length of the ON time of the PWM signal 9a is the length of time that the PWM signal 9a is maintained in the ON state.

Further, in the present embodiment, the control unit 10 controls the inverter circuit 4 and the load 101 when the ON time of the PWM signal 9a from the PWM signal generating unit 9 is equal to or longer than the predetermined threshold time Tmax (see FIG. 4). It is configured to determine that there is a disconnection between and.

Specifically, the control unit 10 outputs the PWM signal 9a from the PWM signal creation unit 9, which is output because the detection signal of the current detection circuit 5 becomes smaller than the signal from the current command unit 7. When the ON time (see FIG. 4) is equal to or longer than the predetermined threshold time Tmax (see FIG. 4), it is determined that the disconnection between the inverter circuit 4 and the load 101 is made. ..

Specifically, the predetermined threshold time Tmax (see FIG. 4) is a value calculated in advance by an experiment and stored in a memory or the like not shown. Then, the control unit 10 disconnects the inverter circuit 4 from the load 101 when the ON time of the PWM signal 9a (see FIG. 4) is longer than the predetermined threshold time Tmax read from the memory or the like. Is configured to determine that it is.

Further, in the present embodiment, the control unit 10 is configured to notify the outside when there is a disconnection between the inverter circuit 4 and the load 101. Specifically, the control unit 10 is configured to control to sound an alarm when the inverter circuit 4 and the load 101 are disconnected.

(Configuration of inverter circuit)
The inverter circuit 4 is provided with a semiconductor element circuit 40 forming an upper arm and a semiconductor element circuit 41 forming a lower arm. Further, each of the semiconductor element circuit 40 forming the upper arm and the semiconductor element circuit 41 forming the lower arm is configured to be turned on/off in synchronization with the PWM signal 9a. The semiconductor element circuit 40 forming the upper arm includes a U-phase semiconductor element forming the upper arm, a V-phase semiconductor element forming the upper arm, and a W-phase semiconductor element forming the upper arm, which are not shown. The semiconductor element circuit 41 forming the lower arm includes a U-phase semiconductor element forming the lower arm, a V-phase semiconductor element forming the lower arm, and a W-phase semiconductor element forming the lower arm, which are not shown. .. In FIG. 1, the wiring connecting the semiconductor element circuit 40 forming the upper arm and the semiconductor element circuit 41 forming the lower arm is omitted. It should be noted that the semiconductor element circuit 40 forming the upper arm and the semiconductor element circuit 41 forming the lower arm are the semiconductor element forming the upper arm and the semiconductor element forming the lower arm, respectively, in the claims. Is an example.

The inverter circuit 4 also includes a bootstrap circuit 42. The bootstrap circuit 42 also has a bootstrap capacitor 42a.

Further, the inverter circuit 4 (bootstrap circuit 42) is provided with an upper arm drive circuit 43 for controlling on/off of the semiconductor element circuit 40 forming the upper arm. Further, the inverter circuit 4 (bootstrap circuit 42) is provided with a lower arm drive circuit 44 for controlling on/off of the semiconductor element circuit 41 forming the lower arm.

(Configuration of bootstrap circuit)
As shown in FIG. 2, the bootstrap circuit 42 includes a bootstrap circuit power supply 42b and a bootstrap circuit diode 42c that rectifies the current from the bootstrap circuit power supply 42b.

The upper arm drive circuit 43, together with the PWM signal 9a from the PWM signal generating section 9 (see FIG. 4) if in the ON state, to turn on the switching elements of the semiconductor device circuit 40 constituting the upper arm, the PWM signal 9a Is off, each switching element of the semiconductor element circuit 40 forming the upper arm is controlled to be turned off . Further, the lower arm drive circuit 44 turns off each switching element of the semiconductor element circuit 41 forming the lower arm when the PWM signal 9a is in the ON state, and forms the lower arm when the PWM signal 9a is in the OFF state. Then, each switching element of the semiconductor element circuit 41 is controlled to be turned on . Although each of the semiconductor element circuit 40 forming the upper arm and the semiconductor element circuit 41 forming the lower arm has three switching elements, each of them is omitted in FIG. doing.

When the PWM signal 9a (see FIG. 4) is in the off state, the current from the bootstrap circuit power supply 42b causes the bootstrap circuit diode 42c, the bootstrap capacitor 42a, and the semiconductor element circuit 41 forming the lower arm. Through each of. As a result, the bootstrap capacitor 42a is charged. In addition, when the PWM signal 9a is in the ON state, the charged current from the bootstrap capacitor 42a flows to the upper arm drive circuit 43 to turn on each switching element of the semiconductor element circuit 40 forming the upper arm. At the same time, the bootstrap capacitor 42a is discharged.

In addition, in the present embodiment, the current detection circuit is caused by the disconnection between the inverter circuit 4 and the load 101 (see FIG. 1), which reduces the supply power of the bootstrap capacitor 42a as the common power supply. The detection signal 5 is small. Specifically, due to the disconnection between the inverter circuit 4 and the load 101, the charge (voltage) of the bootstrap capacitor 42a decreases, and the detection signal of the current detection circuit 5 decreases.

In particular, it decreases the charge of the bootstrap capacitor 42a, the electric power supplied to the current detection circuit 5 of the bootstrap capacitor 42a is reduced. Therefore, the detection signal of the current detection circuit 5 becomes smaller than the signal of the current command unit 7 (see FIG. 1).

Further, since the detection signal of the current detection circuit 5 becomes smaller than the signal of the current command unit 7 (see FIG. 1), the modulation signal (see FIG. 3) output from the current adjusting unit 8 (see FIG. 1) is changed. When the magnitude becomes larger than the magnitude of the carrier wave (see FIG. 3), the PWM signal 9a (see FIG. 4) is turned on. Therefore, the upper arm drive circuit 43 controls the bootstrap capacitor 42a to discharge. To be done. As described above, the disconnection between the inverter circuit 4 and the load 101 causes the charge of the bootstrap capacitor 42a to continue decreasing without being charged. As a result, when the inverter circuit 4 and the load 101 (see FIG. 1) are disconnected, the PWM signal 9a is kept in the ON state.

(Detection method of disconnection)
As shown in FIG. 3, the modulation signal in the case where there is a disconnection between the inverter circuit 4 (see FIG. 1) and the load 101 (see FIG. 1) hardly decreases even after increasing to the maximum, and remains unchanged. Maintained in a state. In this case, after the time t1 when the magnitude of the modulated signal becomes larger than the magnitude of the carrier wave, the magnitude of the modulated signal does not become smaller than the magnitude of the carrier wave. Further, the modulation signal when there is no disconnection between the inverter circuit 4 and the load 101 (normal time) has a normal sine wave shape as shown by the broken line in FIG. If no disconnection occurs, the magnitude of the modulation signal becomes larger than the magnitude of the carrier wave at time t2, and the magnitude of the modulation signal becomes less than or equal to the magnitude of the carrier wave at time t3.

That is, as shown in FIG. 4, when a disconnection occurs between the inverter circuit 4 (see FIG. 1) and the load 101 (see FIG. 1), the magnitude of the modulation signal (see FIG. 3) at time t1. Becomes larger than the size of the carrier wave (see FIG. 3), and the PWM signal 9a is turned on. In this case, after the PWM signal 9a is turned on, the PWM signal 9a is maintained in the on state. As a result, the ON time of the PWM signal 9a becomes longer than the predetermined threshold time Tmax.

Further, when the disconnection does not occur between the inverter circuit 4 (see FIG. 1) and the load 101 (see FIG. 1) (normal time), the modulation signal (see FIG. 3) is obtained between time t2 and time t3. Becomes larger than that of the carrier wave (see FIG. 3), and the PWM signal 9a is turned on. Here, the predetermined threshold time Tmax is, for example, a time corresponding to the half cycle T (see FIG. 3) of the modulation signal in the normal state, and therefore the PWM signal 9a is in the ON state in the normal state. The time (t3−t2) becomes smaller than the predetermined threshold time Tmax.

(Control flow for disconnection detection)
Next, a control flow for detecting disconnection by the control unit 10 (see FIG. 1) of the electric motor drive device 100 (see FIG. 1) of the present embodiment will be described with reference to FIG.

First, in step S1, the control unit 10 (see FIG. 1) determines whether the PWM signal 9a (see FIG. 4) is on. If the PWM signal 9a is in the on state, the process proceeds to step S2. If the PWM signal 9a is not on, the control of step S1 is repeated. Next, in step S2, the PWM signal 9a activates a timer for measuring the ON time. Next, in step S3, it is determined whether or not the ON time of the PWM signal 9a is longer than a predetermined threshold time Tmax. If the ON time of the PWM signal 9a is longer than the predetermined threshold time Tmax, the process proceeds to step S4. Next, in step S4, it is determined that a disconnection between the inverter circuit 4 (see FIG. 1) and the load 101 (see FIG. 1) has been detected. If the ON time of the PWM signal 9a is equal to or less than the predetermined threshold time Tmax in step S3, the process proceeds to step S5. In step S5, the timer is reset and the process returns to step S1. After the disconnection is detected in step S4, the outside is notified in step S6 that the disconnection has occurred.

(Effect of this embodiment)
In this embodiment, the following effects can be obtained.

In the present embodiment, as described above, the inverter circuit 4 that outputs an alternating current to the load 101, the PWM signal creation unit 9 that controls the on/off time of the PWM signal 9a for driving the inverter circuit 4, and the inverter circuit 4 A current detection circuit 5 for detecting an alternating current output from the load circuit 101 to the load 101; a current command section 7 for controlling the current value output from the inverter circuit 4 to the load 101 to a predetermined current value; The disconnection state between the inverter circuit 4 and the load 101 is detected based on the PWM signal 9a output from the PWM signal generation unit 9 that is output based on the signal from the unit 7 and the detection signal from the current detection circuit 5. The electric motor drive device 100 is configured to include the control unit 10. Accordingly, the control unit 10 is configured to detect the disconnection state between the inverter circuit 4 and the load 101 based on the PWM signal 9a from the PWM signal creation unit 9, and thus the current detection circuit 5 It is possible to detect the disconnection between the inverter circuit 4 and the load 101 without calculating the fluctuation rate of the current value while calculating the current value detected by. Here, the PWM signal 9a changes within a relatively short time after the disconnection occurs with respect to the time required to calculate the current value and monitor the rate of change of the current value. Therefore, by detecting the disconnection state based on the PWM signal 9a, the disconnection between the inverter circuit 4 and the load 101 can be promptly detected.

Further, in the present embodiment, as described above, the control unit 10 causes the inverter circuit 4 and the load 101 to operate when the ON time of the PWM signal 9a from the PWM signal generating unit 9 is equal to or longer than the predetermined threshold time Tmax. The electric motor drive device 100 is configured to determine that there is a disconnection between Thereby, the disconnection can be detected only by comparing the ON time of the PWM signal 9a and the predetermined threshold time Tmax. As a result, the disconnection can be detected more easily than in the case where the current value is calculated and the fluctuation rate of the current value is monitored.

Further, in the present embodiment, as described above, the control unit 10 outputs the PWM signal generated due to the detection signal of the current detection circuit 5 becoming smaller than the signal from the current command unit 7, and thus PWM signal generation. The motor drive device 100 is configured to determine that the disconnection between the inverter circuit 4 and the load 101 is made when the ON time of the PWM signal 9a from the unit 9 is equal to or longer than the predetermined threshold time Tmax. To do. Here, when the disconnection occurs, the detection signal of the current detection circuit 5 becomes smaller, so that the detection signal of the current detection circuit 5 becomes smaller than the signal from the current command unit 7. As a result, when a disconnection occurs, the ON time of the PWM signal 9a from the PWM signal creation unit 9 becomes long, so that the disconnection can be easily detected.

Further, in the present embodiment, as described above, each of the inverter circuit 4 and the current detection circuit 5 is configured such that power is supplied by the common power source, and the power is supplied between the inverter circuit 4 and the load 101. The motor drive device 100 is configured so that the detection signal of the current detection circuit 5 becomes small due to the decrease in the supply power of the common power source due to the disconnection of the. As a result, when the detection signal of the current detection circuit 5 becomes small and the control is performed so as to increase the output current of the inverter circuit 4, the power supply capability of the common power supply that supplies power to the inverter circuit 4 Has decreased, the output power of the inverter circuit 4 does not increase. Therefore, the PWM signal 9a, which is a signal for controlling the output power of the inverter circuit 4 to increase, is turned on. Thereby, the disconnection between the inverter circuit 4 and the load 101 can be easily detected based on the length of the ON time of the PWM signal 9a.

In addition, in the present embodiment, as described above, the inverter circuit 4 is synchronized with the bootstrap circuit 42 having the bootstrap capacitor 42a that is a common power source for the inverter circuit 4 and the current detection circuit 5, and the PWM signal 9a. The bootstrap circuit 42 includes a semiconductor element circuit 40 forming an upper arm and a semiconductor element circuit 41 forming a lower arm whose on/off is controlled. The bootstrap circuit 42 is a bootstrap capacitor when the PWM signal 9a is on. When the PWM signal 9a is off while the 42a is discharged, the bootstrap capacitor 42a is configured to be charged, and the disconnection between the inverter circuit 4 and the load 101 causes the bootstrap. The electric motor drive device 100 is configured such that the detection signal of the current detection circuit 5 becomes small due to the decrease in the charge of the capacitor 42a. As a result, by using the bootstrap capacitor 42a as the common power supply, the cost can be reduced as compared with the case where the external power supply or the like is used as the common power supply. Further, compared to an external power source or the like, the bootstrap capacitor 42a is more likely to discharge the charged electric charge, so that it is possible to easily detect the disconnection due to the length of the ON time of the PWM signal 9a.

Further, in the present embodiment, as described above, the control unit 10 configures the motor drive device 100 to notify the outside when the inverter circuit 4 and the load 101 are disconnected. As a result, the user is notified of the disconnection, so that when the disconnection occurs, the user can recognize the disconnection, and the user can immediately stop the circuit control.

[Modification]
It should be considered that the embodiments disclosed this time are exemplifications in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of the claims, and further includes meanings equivalent to the scope of the claims and all modifications (modifications) within the scope.

For example, in the above-described embodiment, an example has been shown in which the control unit 10 sounds an alarm when a disconnection is detected, but the present invention is not limited to this. For example, the control unit 10 may be configured to control the operation of the electric motor drive device 100 to be stopped when the disconnection is detected.

Further, in the above-described embodiment, the current detection circuit 5 has shown the example of the configuration for detecting the current value of the U-phase wiring 4a and the current value of the W-phase wiring 4c, but the present invention is not limited to this. Absent. For example, the current detection circuit 5 may be configured to detect the current value of the U-phase wiring 4a and the current value of each of the V-phase wiring 4b. Further, the current detection circuit 5 may be configured to detect each of the current value of the V-phase wiring 4b and the current value of the W-phase wiring 4c. Further, the current detection circuit 5 may be configured to detect each of the current value of the U-phase wiring 4a, the V-phase wiring 4b, and the W-phase wiring 4c.

Further, in the above embodiment, the example in which the predetermined threshold time Tmax is the time corresponding to the half cycle of the normal modulation signal when the disconnection does not occur has been described, but the present invention is not limited to this. .. For example, a time different from the half cycle of the modulation signal may be set as the predetermined threshold time Tmax.

Further, although the bootstrap capacitor 42a, the upper arm drive circuit 43, and the lower arm drive circuit 44 are provided one by one in the above embodiment, the present invention is not limited to this. I can't. For example, three bootstrap capacitors 42a, upper arm drive circuits 43, and lower arm drive circuits 44 may be provided so as to correspond to each phase.

Further, in the above embodiment, an example of the configuration in which the bootstrap capacitor 42a is provided as the common power source has been shown, but the present invention is not limited to this. For example, a power source other than the bootstrap capacitor 42a may be used as the common power source.

Further, in the above-described embodiment, the example of the configuration in which the PWM signal 9a is turned on when the magnitude of the modulation signal is larger than the magnitude of the carrier wave is shown, but the present invention is not limited to this. For example, the PWM signal 9a may be turned on when the magnitude of the modulation signal is larger than a predetermined ratio of the magnitude of the carrier wave.

Further, in the above-described embodiment, for convenience of description, the processing of the control unit 10 of the present invention has been described using a flow-driven flowchart that sequentially performs processing along the processing flow, but the present invention is not limited to this. .. In the present invention, the processing operation of the control unit 10 may be performed by an event driven type (event driven type) processing that executes processing for each event. In this case, the event driving may be performed completely, or the event driving and the flow driving may be combined.

4 Inverter circuit 5 Current detection circuit 7 Current command section 9 PWM signal creation section (pulse width modulation section)
9a PWM signal 10 Control unit 40 Semiconductor element circuit forming upper arm (semiconductor element forming upper arm)
41 Semiconductor element circuit forming the lower arm (semiconductor element forming the lower arm)
42 bootstrap circuit 42a bootstrap capacitor (common power supply)
100 electric motor drive device 101 load Tmax predetermined threshold time

Claims (5)

An inverter circuit that outputs an alternating current to the load,
A pulse width modulator that controls the on/off time of a PWM signal for driving the inverter circuit;
A current detection circuit for detecting an alternating current of at least two phases out of three phases output from the inverter circuit to the load;
A current command unit that controls the current value output from the inverter circuit to the load to be a predetermined current value;
Based on that the ON time of the PWM signal from the pulse width modulation unit, which is output based on the signal from the current command unit and the detection signal of the current detection circuit, is equal to or longer than a predetermined threshold time. And a control unit that detects a disconnection state between the inverter circuit and the load. The control unit outputs a detection signal of the current detection circuit that is smaller than a signal from the current command unit, the ON time of the PWM signal from the pulse width modulation unit, said predetermined when it is more than the threshold h, the between the inverter circuit and the load is configured to determine that the broken, the motor driving apparatus according to claim 1. Each of the inverter circuit and the current detection circuit is configured to be supplied with power by a common power source,
By between the load and the inverter circuit is disconnected, due to the supply power of the common power supply is decreased, the detection signal of the current detection circuit is configured to be smaller, claim 2 The electric motor drive device according to. The inverter circuit includes a bootstrap circuit having a bootstrap capacitor which is the common power source for the inverter circuit and the current detection circuit, and a semiconductor element forming an upper arm whose on/off is controlled in synchronization with the PWM signal. And a semiconductor element forming the lower arm,
The bootstrap circuit is configured such that the bootstrap capacitor is discharged when the PWM signal is on, and the bootstrap capacitor is charged when the PWM signal is off. And
Said by between the inverter circuit and the load is disconnected, due to the charge of the bootstrap capacitor drops, the detection signal of the current detection circuit is configured to be smaller, claim 3 The electric motor drive device according to. Wherein, when between the load and the inverter circuit is disconnected, and is configured to notify an external, motor driving device according to any one of claims 1-4.

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