Noise reduction device, power conversion device, vehicle, and noise reduction method

Abstract

To provide a noise reducing device capable of suppressing defects caused by noise components occurring on a load, a power conversion device, a vehicle, and a noise reduction method.SOLUTION: A noise reduction device has a noise reduction circuit and a fault diagnosis circuit. The noise reduction circuit generates an offsetting signal. The offsetting signal is a signal of opposite polarity to a noise component occurring on a load. The fault diagnosis circuit detects the level of the offsetting signal. The fault diagnosis circuit determines whether the detected level is within an appropriate range. The fault diagnosis circuit diagnoses a fault of the noise reduction circuit in accordance with the determination results.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a noise reduction device, a power conversion device, a vehicle, and a noise reduction method. [Background technology]

[0002] Noise reduction devices may generate a cancellation signal of opposite polarity to a noise component occurring in a load of a predetermined circuit, and supply the cancellation signal to the predetermined circuit or load (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5621533 Summary of the Invention [Problem to be solved by the invention]

[0004] The noise reduction device may not operate properly. In this case, noise components generated in the load of a specific circuit may cause malfunctions. For example, if the noise components leak to other devices via the ground potential, the other devices may malfunction.

[0005] The present disclosure provides a noise reduction device, a power conversion device, a vehicle, and a noise reduction method that can suppress problems caused by noise components generated in a load. [Means for solving the problem]

[0006] The noise reduction device according to the present disclosure includes a noise reduction circuit and a fault diagnosis circuit. Control circuit and The noise reduction circuit generates a cancellation signal. The cancellation signal is a signal of opposite polarity to the noise component generated in the load, and the fault diagnosis circuit detects the level of the cancellation signal. The fault diagnosis circuit determines whether the detected level is within an appropriate range. The fault diagnosis circuit diagnoses a fault in the noise reduction circuit based on the determination result. When the fault diagnosis circuit diagnoses that a fault has occurred in the noise reduction circuit, the control circuit stops the switching circuit connected to the load, waits for a predetermined time, and then resumes operation of the switching circuit. [Effects of the Invention]

[0007] According to the noise reduction device according to the present disclosure, problems caused by noise components occurring in a load can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a vehicle equipped with a power conversion device including a noise reduction device according to an embodiment; [Figure 2] 1 is a diagram showing the functional configuration of a power conversion device including a noise reduction device according to an embodiment; [Figure 3] 1 is a circuit diagram showing the configuration of a power conversion device including a noise reduction device according to an embodiment. [Figure 4] 4 is a flowchart showing the operation of a power conversion device including a noise reduction device according to an embodiment. [Figure 5] FIG. 10 is a diagram showing the configuration of a power conversion device including a noise reduction device according to a first modified example of an embodiment. [Figure 6] FIG. 10 is a diagram showing the configuration of a power conversion device including a noise reduction device according to a second modification of the embodiment. [Figure 7] FIG. 10 is a diagram showing the configuration of a power conversion device including a noise reduction device according to a third modified example of the embodiment. [Figure 8] FIG. 10 is a diagram showing the configuration of a power conversion device including a noise reduction device according to a fourth modified example of an embodiment. [Figure 9] 10 is a flowchart showing the operation of a noise reduction device according to a fifth modified example of an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of a noise reduction device according to the present disclosure will be described with reference to the drawings.

[0010] (Embodiment) The noise reduction device according to the embodiment performs a noise reduction operation by generating a cancellation signal of opposite polarity to a noise component occurring in a load of a predetermined circuit and supplying the cancellation signal to the predetermined circuit, but is devised to perform the noise reduction operation appropriately. The noise reduction device 1 can be mounted on a vehicle 100 as shown in Fig. 1. Fig. 1 is a diagram showing the vehicle 100 on which the noise reduction device 1 is mounted.

[0011] The vehicle 100 includes a plurality of wheels 102-1 to 102-4, a vehicle body 101, and a noise reduction device 1.

[0012] The wheels 102-1 to 102-4 are each rotatable around an axle. Wheels (second wheels) 102-3 and 102-4 are disposed behind the wheels (first wheels) 102-1 and 102-2, and corresponding front and rear axles (not shown) are disposed accordingly. The wheels 102-1 and 102-2 are coupled to one end and the other end of the front axle, respectively. The wheels 102-3 and 102-4 are coupled to one end and the other end of the rear axle, respectively. While FIG. 1 illustrates a configuration in which the vehicle 100 has four wheels 102, the number of wheels 102 may be three or less, or five or more.

[0013] The vehicle body 101 rotatably supports axles, and wheels 102-1 to 102-4 are coupled to the axles via the axles. The vehicle body 101 can move forward by the rotation of the wheels 102-1, 102-2 and the wheels 102-3, 102-4.

[0014] The noise reduction device 1 is disposed inside a vehicle body 101 and is included in a power conversion device 103 such as an AC / DC converter, a DC / DC converter, or an inverter in the vehicle 100. The power conversion device 103 is connected between a power source PS and a load LD, and performs power conversion on the power received from the power source PS and supplies the power to the load LD.

[0015] For example, if the vehicle 100 is an electric vehicle or a hybrid vehicle, the power conversion device 103 is, for example, a drive device connected between a motor 106 serving as a load LD and a battery 105 serving as a power source. The power conversion device 103 converts DC power supplied from the battery 105 into AC power and supplies it as drive power to the motor 106. The motor 106 functions as a power source for rotating the wheels 102-1, 102-2 and the wheels 102-3, 102-4.

[0016] Alternatively, when the vehicle 100 is equipped with a battery 105 that can be charged from an external power source, the power conversion device 103 is, for example, an on-board charger connected between a connection terminal 104 to which a power source PS, such as a commercial power source or a charger at a charging station, is to be connected and the battery 105 as a load LD. In the on-board charger, AC power input from the power source PS passes through a passive noise filter (ACF: AC filter), is converted to DC power by a rectifier circuit, and the power factor and voltage are controlled by a PFC circuit (power factor correction circuit). The controlled DC power is converted into high-frequency AC power by a subsequent inverter to drive an isolation transformer, and is then converted back to DC power by a rectifier circuit connected to the secondary side via the isolation transformer, and the battery 105 is charged with the DC power.

[0017] Alternatively, the power conversion device 103 is, for example, a DC-DC converter connected between a low-voltage second battery (not shown) as a load LD and the battery 105 as a power source. The power conversion device 103 insulates and converts DC power supplied from the battery 105 into low-voltage DC power, and charges the second battery.

[0018] An active noise cancellation (ANC) function may be provided in the power conversion device 103. The ANC function receives noise components in the power conversion device 103 and generates and outputs a cancellation signal of opposite phase to the noise components, thereby suppressing the effects of the noise components (such as EMI (Electromagnetic Interference) noise) from being emitted to the outside.

[0019] The power conversion device 103 may be functionally configured as shown in Fig. 2. Fig. 2 is a diagram showing the functional configuration of the power conversion device 103 including the noise reduction device 1.

[0020] The power conversion device 103 has a power conversion function 103a and a noise reduction device 1. The noise reduction device 1 has a noise reduction function 103b. The noise reduction function 103b has an active noise cancellation (ANC) function 103b1 and a fault diagnosis function 103b2. The fault diagnosis function 103b2 is a function that autonomously diagnoses faults and can also be called a self-diagnosis function. The fault diagnosis function 103b2 has a control function 103b21, a detection function 103b22, an ON / OFF switching function 103b23, and an injection function 103b24.

[0021] The ANC function 103b1 applies a cancellation signal of opposite polarity to the noise component to the circuitry of the power conversion function 103a. The ON / OFF switching function 103b23 switches the operation of the ANC function 103b1 ON / OFF. For example, the power conversion device 103 is connected to an external power source PS. When a charging command is issued from an ECU (Electric Control Unit) (not shown) to the overall control unit of the power conversion device 103, the control function 103b21 instructs the injection function 103b24 to apply a cancellation signal to the circuitry of the power conversion function 103a. The detection function 103b22 monitors the level of the cancellation signal at that time. The control function 103b21 checks whether the level of the cancellation signal is outside a predetermined tolerance range. At this time, the control function 103b21 may switch the ON / OFF switching function 103b23 as needed. The control function 103b21 checks whether the level of the cancellation signal is outside a predetermined tolerance range in response to the operation of the ANC function 103b1.

[0022] For example, if it is determined that the level of the cancellation signal is outside the allowable range, control function 103b21 commands ON / OFF switching function 103b23 to turn off the operation of ANC function 103b1. This makes it possible to suppress the effects of EMI noise above a specified value due to a malfunction of ANC function 103b1, etc.

[0023] Alternatively, if it is determined that the level of the cancellation signal is outside the allowable range, the control function 103b21 commands the ECU to notify the occurrence of a malfunction by an alarm device (for example, a warning lamp), thereby urging the driver of the vehicle to take measures to deal with the malfunction of the ANC function 103b1 and preventing EMI noise above a specified value from being left unattended.

[0024] In the case of the above-described driving device, a power conversion device 103 including the noise reduction device 1 can be configured as shown in Fig. 3. Fig. 3 is a circuit diagram showing the configuration of the power conversion device 103 including the noise reduction device 1.

[0025] The power conversion device 103 includes a noise reduction device 1, a switching circuit 9, a switching control circuit 10, a noise filter circuit 11-1, and a noise filter circuit 11-2. The noise reduction device 1 includes a noise reduction control circuit 2, a noise reduction circuit 3, a fault diagnosis circuit 4, a control circuit 5, an alarm device 6, a detection circuit 7, and an injection circuit 8.

[0026] In the power conversion device 103, the power conversion function 103a (see FIG. 2) is mainly realized by the switching circuit 9 and the switching control circuit 10. The noise reduction function 103b is mainly realized by the noise reduction device 1. The ANC function 103b1 is mainly realized by the noise reduction circuit 3. The fault diagnosis function 103b2 is mainly realized by the noise reduction control circuit 2, the fault diagnosis circuit 4, the control circuit 5, the alarm device 6, the detection circuit 7, and the injection circuit 8. The control function 103b21 is mainly realized by the noise reduction control circuit 2, the fault diagnosis circuit 4, the control circuit 5, the alarm device 6, and the detection circuit 7. The detection function 103b22 is mainly realized by the fault diagnosis circuit 4. The ON / OFF switching function 103b23 is mainly realized by the fault diagnosis circuit 4 or the control circuit 5. The injection function 103b24 is mainly realized by the injection circuit 8.

[0027] The switching circuit 9 is connected between the power supply PS and the load LD. The noise filter circuit 11-1 and the noise filter circuit 11-2 are connected between the power supply PS and the switching circuit 9. The switching circuit 9 has a plurality of switching elements. The plurality of switching elements perform switching operations in response to gate signals supplied from a switching control circuit 10. As a result, the switching circuit 9 performs normal power conversion on the power supplied from the power supply PS via the noise filter circuits 11-1 and 11-2, and supplies the power to the load LD.

[0028] The noise filter circuit 11-1 is disposed between the power supply PS and the injection circuit 8, and includes, for example, common mode coils L3 and L4, line-to-line capacitors C7 and C6, and line-to-earth capacitors C12, C11, C14, and C13.

[0029] Common mode coils L3 and L4 have one end connected to input nodes Nin1 and Nin2, respectively, and the other end connected to injection circuit 8. Common mode coils L3 and L4 are wound in phase with each other on the core, and magnetic fluxes of currents flowing through the coils cancel each other out, thereby attenuating common mode noise.

[0030] One end of each of the line-to-line capacitors C7 and C6 is connected to a line connecting the input node Nin1 and the injection circuit 8, and the other end is connected to a line connecting the input node Nin2 and the injection circuit 8. The line-to-line capacitors C7 and C6 can bypass noise between the lines and attenuate normal mode noise.

[0031] One end of each of the line-to-earth capacitors C12 and C11 is connected to the line connecting the input node Nin1 and the injection circuit 8, and the other end is connected to ground potential. The line-to-earth capacitors C12 and C11 can bypass noise to ground potential and attenuate common-mode noise.

[0032] One end of each of the line-to-earth capacitors C14 and C13 is connected to the line connecting the input node Nin2 and the injection circuit 8, and the other end is connected to ground potential. The line-to-earth capacitors C14 and C13 can bypass noise to ground potential and attenuate common-mode noise.

[0033] The noise filter circuit 11-2 is disposed between the injection circuit 8 and the switching circuit 9, and includes, for example, common mode coils L5 and L6, a line-to-line capacitor C8, and line-to-earth capacitors C15 and C16.

[0034] One end of each of the common mode coils L5 and L6 is connected to the injection circuit 8, and the other end is connected to the switching circuit 9. The common mode coils L5 and L6 are wound in phase with each other on the core, and the magnetic fluxes of the currents flowing through the coils cancel each other out, thereby attenuating common mode noise.

[0035] The line-to-line capacitors C8 are connected at one end to the P-side line L that connects the injection circuit 8 and the switching circuit 9. P and the other end of the N-side line L connecting the injection circuit 8 and the switching circuit 9. N The line-to-line capacitor C8 can bypass noise between the lines and attenuate normal mode noise.

[0036] The line-to-earth capacitor C15 has one end connected to the P-side line L that connects the injection circuit 8 and the switching circuit 9. P and the other end is connected to ground potential. The line-to-ground capacitor C15 bypasses noise to the ground potential and can attenuate common-mode noise.

[0037] The line-to-earth capacitor C16 has one end connected to the N-side line L that connects the injection circuit 8 and the switching circuit 9. N and the other end is connected to the ground potential. The line-to-ground capacitor C16 bypasses noise to the ground potential and can attenuate common-mode noise.

[0038] In the power conversion device 103, there is a possibility that noise components that cannot be completely removed by the noise filter circuits 11-1 and 11-2 may exist, and in order to suppress the noise components that cannot be completely removed, the noise reduction device 1 is provided.

[0039] In the noise reduction device 1, the detection circuit 7 is disposed between the switching circuit 9 and the load LD. The detection circuit 7 detects parameters corresponding to noise components. When three-phase AC power is supplied from the switching circuit 9 to the load LD, the detection circuit 7 may detect a current corresponding to an imbalance between the three phases, for example. The detection circuit 7 supplies the detected parameters to the noise reduction control circuit 2.

[0040] The noise reduction control circuit 2 is disposed between the detection circuit 7 and the noise reduction circuit 3. The noise reduction control circuit 2 generates a control signal CS in accordance with the supplied parameters. The parameters (e.g., three-phase current) change at a timing synchronized with the power supplied from the switching circuit 9 to the load LD. Therefore, the noise reduction control circuit 2 can generate a control signal CS that operates the noise reduction device 1 in synchronization with the power supplied from the switching circuit 9 to the load LD in accordance with the supplied parameters. The noise reduction control circuit 2 supplies the control signal CS to the noise reduction circuit 3.

[0041] The noise reduction circuit 3 is arranged between the noise reduction control circuit 2, the fault diagnosis circuit 4, the injection circuit 8, and the detection circuit 7. The noise reduction circuit 3 generates a cancellation signal of opposite polarity to the noise component occurring in the load LD. The noise reduction circuit 3 can generate the cancellation signal in the form of a voltage. The noise reduction circuit 3 supplies the cancellation signal to the injection circuit 8.

[0042] The noise reduction circuit 3 includes a power supply E, a capacitance element C1, a capacitance element C2, an amplifier AM, a transistor Q1, a transistor Q2, a capacitance element C3, an isolation transformer TR, a capacitance element C4, and a capacitance element C5.

[0043] Power supply E is a DC power supply. Transistors Q1 and Q2 are connected in series across power supply E. The output node of noise reduction control circuit 2 is connected to the control terminals of transistors Q1 and Q2 via amplifier AM. The common connection terminal of transistors Q1 and Q2 is connected to one end of secondary winding L2 via capacitance element C3.

[0044] Transistors Q1 and Q2 are bridge-connected. Transistors Q1 and Q2 may be bipolar transistors or MOSFETs. If they are bipolar transistors, transistor Q1 is an NPN-type transistor and transistor Q2 is a PNP-type transistor. If they are MOSFETs, transistor Q1 is a P-channel MOSFET and transistor Q2 is an N-channel MOSFET.

[0045] Capacitance elements C1 and C2 are connected in series across both ends of a power supply E, in parallel with the series connection of transistors Q1 and Q2. One end of the capacitance element C1 is connected to the positive electrode of the power supply E, one end of the capacitance element C2 is connected to the negative electrode of the power supply E, and the other ends of the capacitance elements C1 and C2 are connected together and to one end of a secondary winding L2.

[0046] The isolation transformer TR has a primary winding L1 and a secondary winding L2. The ratio of the number of turns of the primary winding L1 to the number of turns of the secondary winding L2 is 1:1. The primary winding L1 and the secondary winding L2 are arranged in positions where they can be magnetically coupled to each other. The isolation transformer TR may have a magnetic core. The primary winding L1 and the secondary winding L2 may be magnetically coupled via the magnetic core.

[0047] A capacitive element C4 is connected to both ends of the primary winding L1. One end of the capacitive element C4 is connected to one end of the primary winding L1, the injection circuit 8, and the detection node 4a of the fault diagnosis circuit 4, and the other end is connected to the other end of the primary winding L1, the detection node 4b of the fault diagnosis circuit 4, and one end of the capacitive element C5.

[0048] The capacitive element C5 is connected between the capacitive element C4 and a reference potential (for example, ground potential). One end of the capacitive element C5 is connected to the other end of the capacitive element C4, the other end of the primary winding L1, and the detection node 4b of the fault diagnosis circuit 4, and the other end is connected to the reference potential.

[0049] Here, for example, the housing of the load LD is connected to a reference potential, and noise components may leak through the housing to the reference potential. These noise components flow through the reference potential to the other end of the capacitive element C5, generating a voltage corresponding to the noise components across the capacitive element C5. In response, a voltage of opposite polarity to the voltage across the capacitive element C5, i.e., a voltage of opposite polarity to the noise components, can be generated across the capacitive element C4. At this time, transistors Q1 and Q2 are turned on and off in response to the control signal CS, and a signal corresponding to the control signal CS is transmitted from the capacitive element C3 to the secondary winding L2 to the primary winding L1. As a result, a cancellation signal of opposite polarity to the noise components appears as a voltage across the capacitive element C4 and is transmitted to the injection circuit 8. It is desirable that the absolute amplitude of the cancellation signal be within an appropriate range that can be considered approximately equal to the absolute amplitude of the noise components.

[0050] The injection circuit 8 is connected between the power supply PS and the switching circuit 9, for example, between the noise filter circuit 11-1 and the noise filter circuit 11-2. The injection circuit 8 injects a cancellation signal between the noise filter circuit 11-1 and the noise filter circuit 11-2. The injection circuit 8 includes, for example, capacitive elements C21 and C22. The capacitive elements C21 and C22 are connected in series between the P-side line and the N-side line, and one end of the capacitive element C4 that holds the cancellation signal is connected to the connection point between the capacitive elements C21 and C22. If the capacitance values ​​of the capacitive elements C21 and C22 are equal, a common-mode component of the P-side signal and the N-side signal appears at the connection point. The cancellation signal can be injected into the common-mode component.

[0051] A cancellation signal is injected between the noise filter circuits 11-1 and 11-2, and the cancellation signal can be injected into the noise components that have passed through the noise filter circuits 11-1 and 11-2, so that the noise components can be cancelled out effectively. The noise filter circuits 11-1 and 11-2 reduce the effect of the cancellation signal on the power supply PS or the load LD.

[0052] If the noise reduction circuit 3 malfunctions, the absolute amplitude value of the cancellation signal may fall below the appropriate range, making it difficult to cancel out the noise component. Alternatively, if the noise reduction circuit 3 malfunctions, the absolute amplitude value of the cancellation signal may increase beyond the appropriate range, causing the noise component to be over-cancelled, resulting in the cancellation signal itself becoming a new noise component.

[0053] Therefore, fault diagnosis circuit 4 detects the level of the cancellation signal. Fault diagnosis circuit 4 detects the voltage at one end of capacitive element C4 via detection node 4a and the voltage at the other end of capacitive element C4 via detection node 4b. Fault diagnosis circuit 4 can detect the level of the cancellation signal by calculating the difference between the voltage detected at detection node 4a and the voltage detected at detection node 4b.

[0054] Fault diagnosis circuit 4 determines whether the detected level is outside an appropriate range. Fault diagnosis circuit 4 determines the level of the noise component by calculating the difference between the voltage detected at detection node 4b and a reference potential (e.g., ground potential). Fault diagnosis circuit 4 may set the level of the noise component with the opposite polarity as the target level of the cancellation signal, and may set the range of variation of a predetermined percentage (e.g., ±5%) from the target level as the appropriate range of the cancellation signal.

[0055] The fault diagnosis circuit 4 diagnoses a fault in the noise reduction circuit 3 according to the judgment result. If the detected level is outside the appropriate range, the fault diagnosis circuit 4 diagnoses that a fault has occurred in the noise reduction circuit 3. If the detected level is within the appropriate range, the fault diagnosis circuit 4 diagnoses that no fault has occurred in the noise reduction circuit 3. The fault diagnosis circuit 4 supplies the diagnosis result to the control circuit 5.

[0056] The control circuit 5 may receive a diagnosis result from the fault diagnosis circuit 4 and control the switching control circuit 10 in accordance with the diagnosis result. The control circuit 5 may be an ECU or the like.

[0057] For example, the control circuit 5 may operate the switching circuit 9 at a predetermined low power level in response to a diagnosis result indicating a fault. The predetermined low power level is lower than the normal power level and allows the noise filter circuits 11-1 and 11-2 to remove noise components to an acceptable level. The control circuit 5 controls the switching control circuit 10 to continue operating the switching circuit 9 at the current power level in response to a diagnosis result indicating no fault has occurred. The control circuit 5 controls the switching control circuit 10 to operate the switching circuit 9 at the predetermined low power level in response to a diagnosis result indicating a fault has occurred. If the switching control circuit 10 performs PWM control, the control circuit 5 may control the switching control circuit 10 to limit the pulse width of a gate signal to be supplied to the switching circuit 9 to a predetermined pulse width or less. If the switching control circuit 10 performs PFM control, the control circuit 5 may control the switching control circuit 10 to limit the frequency of a gate signal to be supplied to the switching circuit 9 to a predetermined frequency or less. This allows the level of EMI noise emitted from the power conversion device 103 to be kept below a legally regulated value or a predetermined noise level.

[0058] Furthermore, the control circuit 5 may restart the switching circuit 9 in accordance with the diagnosis result of the occurrence of a fault. In accordance with the diagnosis result of the occurrence of a fault, the control circuit 5 operates the switching circuit 9 at a predetermined low power for a predetermined time, and then restarts the switching circuit 9. This may allow unnecessary charges, if any, to be discharged in the switching circuit 9, thereby enabling the failure state to be overcome. Alternatively, it may allow the noise reduction circuit 3 to overcome the failure state. This may reduce EMI noise in the power conversion device 103.

[0059] Alternatively, the control circuit 5 may stop the switching circuit 9 in accordance with the diagnosis result that a fault has occurred. The control circuit 5 controls the switching control circuit 10 to continue supplying the gate signal to the switching circuit 9 in accordance with the diagnosis result that no fault has occurred. The control circuit 5 controls the switching control circuit 10 to stop supplying the gate signal to the switching circuit 9 in accordance with the diagnosis result that a fault has occurred. That is, the control circuit 5 stops the switching circuit 9 in accordance with the diagnosis result that a fault has occurred. This makes it possible to prevent EMI noise from occurring in the power conversion device 103.

[0060] The control circuit 5 may also control the alarm device 6 in accordance with the diagnosis result. The control circuit 5 controls the alarm device 6 to wait in response to a diagnosis result that no fault has occurred. The control circuit 5 controls the alarm device 6 to notify the occurrence of a fault in response to a diagnosis result that a fault has occurred. The alarm device 6 may notify by visual means or by auditory means. The visual means may be, for example, displaying an error message on a display in the vehicle cabin, or turning on or flashing an alarm lamp in the vehicle cabin. The auditory means may be, for example, outputting an error message as sound from a speaker in the vehicle cabin, or sounding a buzzer. This allows the user to recognize that the noise reduction circuit 3 has failed, and the user can be prompted to perform maintenance (repair, etc.) on the noise reduction circuit 3.

[0061] Incidentally, instead of control circuit 5, fault diagnosis circuit 4 may directly control switching control circuit 10 in accordance with the diagnosis result.

[0062] Alternatively, the fault diagnosis by the noise reduction device 1 may be performed in stages as shown in Fig. 4. Fig. 4 is a flowchart showing the operation of the power conversion device 103 including the noise reduction device 1.

[0063] For example, when fault diagnosis is performed in two stages, the optimum ranges used in the fault diagnosis may be a first optimum range that includes the target level of the cancellation signal and a second optimum range that includes the target level and the first optimum range. The first optimum range may be a range that varies by a predetermined percentage (e.g., ±3%) from the target level of the cancellation signal. The second optimum range may be a range that varies by an even larger predetermined percentage (e.g., ±6%) from the target level of the cancellation signal.

[0064] When power supply from power supply PS begins, power conversion device 103 operates switching circuit 9 with normal power (S1). Noise reduction device 1 detects noise components occurring in load LD and generates a cancellation signal of opposite polarity to the noise components. Noise reduction device 1 injects the generated cancellation signal between power supply PS and switching circuit 9 via injection circuit 8.

[0065] The noise reduction device 1 detects the noise signal to set a first optimum range, detects the level of the cancellation signal, and determines whether the cancellation signal falls outside the first optimum range (S2). Until the cancellation signal falls outside the first optimum range (No in S2), the noise reduction device 1 determines that no failure has occurred in the noise reduction circuit 3, and operates the switching circuit 9 with normal power (S1).

[0066] If the cancellation signal falls outside the first appropriate range (Yes in S2), the noise reduction device 1 determines that a failure has occurred in the noise reduction circuit 3, and operates the switching circuit 9 at a predetermined low power (S3). The predetermined low power is lower than the normal power and is a power that allows the noise filter circuits 11-1 and 11-2 to remove noise components to an acceptable level. The noise reduction device 1 may have, for example, a timer (not shown) in the control circuit 5, and use the timer to measure the duration of operation at the predetermined low power (S3).

[0067] When the duration of the operation at a predetermined low power (S3) reaches a predetermined time, the noise reduction device 1 restarts (S4) the switching circuit 9. That is, the noise reduction device 1 temporarily stops the switching circuit 9, waits for a predetermined time, and then restarts the operation of the switching circuit 9.

[0068] The noise reduction device 1 detects the noise signal to set a second optimum range, and detects the level of the cancellation signal to determine whether the cancellation signal falls outside the second optimum range (S5). If the cancellation signal is within the second optimum range (No in S5), the noise reduction device 1 determines that the failure of the noise reduction circuit 3 is temporary and has already been resolved, and operates the switching circuit 9 with normal power (S1).

[0069] If the cancellation signal is outside the second appropriate range (Yes in S5), the noise reduction device 1 determines that the failure of the noise reduction circuit 3 is not temporary but is still ongoing, and stops the switching circuit 9 (S6) and notifies the user of the occurrence of the failure (S7).

[0070] The fault diagnosis may be performed in n stages (n is an integer equal to or greater than 3). In this case, the appropriate ranges used in the fault diagnosis may include a first appropriate range that includes the target level of the cancellation signal, a second appropriate range that includes the target level and the first appropriate range, and an nth appropriate range that includes the target level, the first appropriate range, and the (n-1)th appropriate range. The first appropriate range may be a range of the cancellation signal that varies by a predetermined percentage (e.g., ±1%) from the target level of the cancellation signal. The second appropriate range may be a range of the cancellation signal that varies by an even larger predetermined percentage (e.g., ±2%) from the target level of the cancellation signal. The nth appropriate range may be a range of the cancellation signal that varies by an even larger predetermined percentage (e.g., ±n%) from the target level of the cancellation signal.

[0071] As described above, in this embodiment, the noise reduction device 1 detects the level of the cancellation signal using the fault diagnosis circuit 4 to determine whether it is outside the appropriate range, and diagnoses a fault in the noise reduction circuit 3 based on the result of the determination. Depending on the diagnosis result of the occurrence of a fault, the noise reduction device 1 operates the switching circuit 9 at low power, stops the switching circuit 9, or notifies the occurrence of a fault using the alarm device 6. This makes it possible to suppress an increase in EMI noise due to a fault in the noise reduction circuit 3, and provides a power conversion device that complies with noise-related laws and regulations.

[0072] Furthermore, in this embodiment, in the power conversion device 103, noise accompanying power conversion is suppressed by the noise filter circuits 11-1 and 11-2 and the noise reduction device 1, so the noise filter circuits 11-1 and 11-2 can be made smaller than when noise is suppressed by the noise filter circuits 11-1 and 11-2 alone. Furthermore, the noise reduction device 1 performs a fault diagnosis on the noise reduction circuit 3, and when a fault is diagnosed, processing is performed to suppress the effects of the fault. This allows the power conversion device 103 to be made smaller while suppressing an increase in noise.

[0073] In the embodiment, the injection circuit 8 is connected between the noise filter circuit 11-1 and the noise filter circuit 11-2, but the injection circuit 8 may be connected between the noise filter circuit 11-2 and the switching circuit 9.

[0074] Furthermore, in the embodiment, the noise reduction device 1 that injects the cancellation signal in the form of a voltage is exemplified, but the noise reduction device may have any configuration that can reduce the noise of the power conversion device 103.

[0075] For example, as a first modified example of the embodiment, the noise reduction device 1i may be configured to inject the cancellation signal in the form of a current, as shown in Fig. 5. Fig. 5 is a diagram showing the configuration of a power conversion device 103i including the noise reduction device 1i according to the first modified example of the embodiment.

[0076] Noise reduction device 1i has a noise reduction circuit 3i, a fault diagnosis circuit 4i, a detection circuit 7i, and an injection circuit 8i instead of noise reduction circuit 3, fault diagnosis circuit 4, detection circuit 7, and injection circuit 8 (see FIG. 3).

[0077] The noise reduction circuit 3i generates a current signal that cancels out the noise component generated in the load and has a polarity opposite to that of the noise component.The noise reduction circuit 3i includes a power supply E, a capacitance element C1, a capacitance element C2, a transistor Q1, and a transistor Q2.

[0078] The detection circuit 7i detects a parameter corresponding to the noise component. The detection circuit 7i includes a capacitance element C12, a capacitance element C14, and a current detector 72. The current detector 72 may be, for example, a device that utilizes the Hall effect or a zero-phase current transformer having an annular core. The current detector 72 detects the difference between the currents passing through a line 73 connecting the capacitance element C12 to the ground and a line 74 connecting the capacitance element C14 to the ground as a parameter corresponding to the noise component.

[0079] Here, the detection circuit 7i is inserted between the noise filter circuit 11-1 and the noise filter circuit 11-2, and can detect the noise component that has passed through the noise filter circuit 11-1 or the noise filter circuit 11-2, so that the noise component to be cancelled can be effectively detected.

[0080] The detection circuit 7i supplies the noise reduction control circuit 2 with parameters corresponding to the detected noise components.

[0081] The noise reduction control circuit 2 controls the on / off of the transistors Q1 and Q2 of the noise reduction circuit 3i according to the parameters. As a result, the noise reduction circuit 3i generates a cancellation signal in the form of a current and supplies it to the injection circuit 8i. The injection circuit 8i has a capacitive element C23, and uses the capacitive element C23 to inject the cancellation signal in the form of a current into a reference potential commonly connected to the housing of the load LD.

[0082] Fault diagnosis circuit 4i has detection node 4b, detection node 4c, and detector 4d. Detection node 4b is connected to detection circuit 7i. Fault diagnosis circuit 4i receives parameters corresponding to the noise component at detection node 4b and determines the level of the noise component according to the parameters. Fault diagnosis circuit 4i may set the level of the noise component with the opposite polarity as the target level of the cancellation signal, and may set the range of variation of a predetermined percentage (e.g., ±5%) from the target level as the appropriate range of the cancellation signal.

[0083] Detector 4d is disposed between injection circuit 8i and the reference potential and detects the offset signal injected from injection circuit 8i to the reference potential. Fault diagnosis circuit 4i receives the level of the offset signal detected by detector 4d at detection node 4c.

[0084] The fault diagnosis circuit 4i determines whether the detected level is outside the appropriate range and diagnoses a fault in the noise reduction circuit based on the result of the determination, similar to the embodiment. The operation of the control circuit 5 and the alarm device 6 based on the diagnosis result of the fault diagnosis circuit 4i is also similar to the embodiment.

[0085] In this way, even with the noise reduction device 1i that extracts the cancellation signal in the form of a current, depending on the diagnosis result of the occurrence of a fault, the switching circuit 9 is operated with low power, the switching circuit 9 is stopped, or the occurrence of a fault is notified by the alarm device 6. This makes it possible to suppress an increase in EMI noise due to a fault in the noise reduction circuit 3i, and provides a power conversion device that complies with noise-related regulations.

[0086] 6, in a power conversion device 103p, a noise reduction device 1p may detect a noise signal between a noise filter circuit 11-2 and a switching circuit 9. FIG. 6 is a diagram showing the configuration of a power conversion device 103p including a noise reduction device 1p according to the second modification of the embodiment.

[0087] In the noise reduction device 1p, the detection circuit 7p is connected between the noise filter circuit 11-2 and the switching circuit 9. The detection circuit 7p detects a parameter corresponding to the noise component between the noise filter circuit 11-2 and the switching circuit 9. The detection circuit 7p has capacitance elements C15 and C16 and a current detector 72. The current detector 72 may be a zero-phase current transformer having an annular core or the like. The current detector 72 detects the difference between the currents passing through the lines 73 and 74 as a parameter corresponding to the noise component.

[0088] At this time, the injection circuit 8 is connected between the power supply PS and the switching circuit 9. The injection circuit 8 may be connected between the noise filter circuit 11-1 and the noise filter circuit 11-2, or may be connected between the power supply PS and the noise filter circuit 11-1.

[0089] In this way, the detection circuit 7p is inserted between the noise filter circuit 11-2 and the switching circuit 9, and the noise components that have passed through the noise filter circuits 11-1 and 11-2 can be detected, so that the noise components to be cancelled can be effectively detected.

[0090] 7, in a case where a power conversion device 103j is provided with one noise filter circuit 11-1 and no noise filter circuit 11-2, the noise reduction device 1 may inject a cancellation signal between the noise filter circuit 11-1 and the switching circuit 9. FIG. 7 is a diagram showing the configuration of a power conversion device including a noise reduction device 1 according to the third modification of the embodiment.

[0091] In the noise reduction device 1, the injection circuit 8 is connected between the noise filter circuit 11-1 and the switching circuit 9. The injection circuit 8 injects a cancellation signal between the noise filter circuit 11-1 and the switching circuit 9. The injection circuit 8 has a capacitance element C21 and a capacitance element C22. The capacitance elements C21 and C22 are connected to the P-side line L P and N side line L NOne end of a capacitance element C4 that holds a cancellation signal is connected to the connection point between capacitance elements C21 and C22. If capacitance values ​​of capacitance elements C21 and C22 are equal, a common mode component of the P-side signal and the N-side signal appears at the connection point. The cancellation signal can be injected into the common mode component.

[0092] In this way, the cancellation signal is injected between the noise filter circuit 11-1 and the switching circuit 9, and the cancellation signal can be injected into the noise component that has passed through the noise filter circuit 11-1, so the noise component can be cancelled out effectively. At the same time, the noise filter circuit 11-1 can reduce the influence of the cancellation signal on the power supply PS side.

[0093] 8, in a fourth modification of the embodiment, when a power conversion device 103k is provided with one noise filter circuit 11-1 and does not have a noise filter circuit 11-2, the noise reduction device 1i may detect a noise signal between the noise filter circuit 11-1 and the switching circuit 9. Fig. 8 is a diagram showing the configuration of a power conversion device 103k including a noise reduction device 1i according to the fourth modification of the embodiment.

[0094] In the noise reduction device 1i, the detection circuit 7i is connected between the noise filter circuit 11-1 and the switching circuit 9. The detection circuit 7i detects a parameter corresponding to the noise component between the noise filter circuit 11-1 and the switching circuit 9. The detection circuit 7i has capacitance elements C12 and C14, and a current detector 72. The current detector 72 may be, for example, a zero-phase current transformer having an annular core. The current detector 72 detects the difference between the currents passing through a line 73 connecting the capacitance element C12 to ground and a line 74 connecting the capacitance element C14 to ground, as the parameter corresponding to the noise component.

[0095] In this way, the detection circuit 7i is inserted between the noise filter circuit 11-1 and the switching circuit 9, and the noise component that has passed through the noise filter circuit 11-1 can be detected, so that the noise component that should be canceled out can be effectively detected.

[0096] As a fifth modification of the embodiment, as shown in Fig. 9, the switching circuit 9 may be stopped multiple times in response to stepwise fault diagnosis by the noise reduction device 1. Fig. 9 is a flowchart showing the operation of a power conversion device 103 including the noise reduction device 1 according to the fifth modification of the embodiment.

[0097] In the power conversion device 103, after S1 and S2 are performed, if the cancellation signal falls outside the first optimum range (Yes in S2), the noise reduction device 1 stops the switching circuit 9 (S11), and after a predetermined time has elapsed, operates the switching circuit 9 at a predetermined low power (S3). Thereafter, after S4 and S5 are performed, if the cancellation signal falls outside the second optimum range (Yes in S5), the noise reduction device 1 stops the switching circuit 9 (S6) and notifies the user of the occurrence of a fault (S7).

[0098] In this way, the switching element 9 is stopped multiple times in response to the step-by-step fault diagnosis by the noise reduction device 1, so if unnecessary charges remain in the switching circuit 9, the unnecessary charges can be discharged, increasing the possibility of escaping from the fault state.

[0099] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit and scope of the invention. For example, the power supply PS may be an AC power supply, the load LD may be a battery, and the power conversion device may be an on-board charger. Alternatively, the power supply PS may be a battery, the load LD may be a low-voltage second battery, and the power conversion device may be a DC-DC converter. These embodiments and modifications are within the scope and spirit of the invention, as well as the scope of the claims and their equivalents. [Explanation of symbols]

[0100] 1,1i noise reduction device 3,3i noise reduction circuit 4,4i Fault diagnosis circuit 9 Switching Circuits 11-1, 11-2 Noise filter circuit 100 vehicles 103, 103i, 103j, 103k Power conversion measures

Claims

1. a noise reduction circuit that generates a canceling signal of opposite polarity to the noise component occurring in the load; a fault diagnosis circuit that detects the level of the cancellation signal, determines whether the detected level is outside an appropriate range, and diagnoses a fault in the noise reduction circuit according to the determination result; a control circuit that, when the fault diagnosis circuit diagnoses that a fault has occurred in the noise reduction circuit, stops a switching circuit connected to the load, waits for a predetermined time, and then resumes operation of the switching circuit; A noise reduction device comprising:

2. The fault diagnosis circuit diagnoses that a fault has occurred in the noise reduction circuit when the detected level is outside the appropriate range, and diagnoses that no fault has occurred in the noise reduction circuit when the detected level is within the appropriate range. The noise reduction device according to claim 1 .

3. The noise reduction circuit detects a noise component occurring in the load and generates a canceling voltage of an opposite polarity to the detected noise component. The noise reduction device according to claim 1 .

4. The noise reduction circuit detects a noise component occurring in the load and generates a canceling current having a polarity opposite to that of the detected noise component. The noise reduction device according to claim 1 .

5. the noise reduction circuit includes an isolation transformer including a primary winding and a secondary winding; The ratio of the number of turns of the primary winding to the number of turns of the secondary winding is 1:1 The noise reduction device according to claim 1 .

6. The noise reduction circuit further includes a control circuit that, when the fault diagnosis circuit determines that a fault has occurred in the noise reduction circuit, operates a switching circuit connected to the load at a power lower than a normal power. The noise reduction device according to claim 1 .

7. The noise reduction circuit further includes a control circuit that stops a switching circuit connected to the load when the failure diagnosis circuit diagnoses that a failure has occurred in the noise reduction circuit. The noise reduction device according to claim 1 .

8. The noise reduction circuit further includes a notification device that notifies the user of the occurrence of a failure when the failure diagnosis circuit diagnoses that a failure has occurred in the noise reduction circuit. The noise reduction device according to claim 1 .

9. A power conversion device comprising the noise reduction device according to any one of claims 1 to 8.

10. a switching circuit connected to the load; a first filter circuit disposed between a power supply and the switching circuit; Furthermore, The noise reduction device further includes a detection circuit connected between the first filter circuit and the switching circuit to detect noise components generated in the load. The power conversion device according to claim 9.

11. a switching circuit connected to the load; a first filter circuit disposed between a power supply and the switching circuit; Furthermore, The noise reduction device further includes an injection circuit connected between the first filter circuit and the switching circuit, which injects a cancellation signal having an opposite polarity to the noise component generated in the load. The power conversion device according to claim 9.

12. a switching circuit connected to the load; a first filter circuit disposed between a power supply and the switching circuit; Furthermore, The noise reduction device comprises: a detection circuit connected between the first filter circuit and the switching circuit to detect a noise component occurring in the load; an injection circuit connected between the first filter circuit and the switching circuit for injecting a cancellation signal having a polarity opposite to that of a noise component generated in the load; Further having The power conversion device according to claim 9.

13. a switching circuit connected to the load; a first filter circuit disposed between a power supply and the switching circuit; a second filter circuit disposed between the first filter circuit and the switching circuit; Furthermore, The noise reduction device further includes an injection circuit connected between the first filter circuit and the second filter circuit, which injects a cancellation signal having an opposite polarity to the noise component occurring in the load. The power conversion device according to claim 9.

14. a switching circuit connected to the load; a first filter circuit disposed between a power supply and the switching circuit; a second filter circuit disposed between the first filter circuit and the switching circuit; Furthermore, The noise reduction device comprises: a detection circuit connected between the second filter circuit and the switching circuit to detect a noise component occurring in the load; an injection circuit connected between the first filter circuit and the second filter circuit, which injects a cancellation signal having an opposite polarity to a noise component generated in the load; Further having The power conversion device according to claim 9.

15. A vehicle comprising the power conversion device according to claim 9.

16. generating a canceling signal of opposite polarity to the noise component occurring in the load by a noise reduction circuit; detecting a level of the generated cancellation signal; determining whether the detected level falls outside an appropriate range; diagnosing a fault in the noise reduction circuit according to the determination result; When it is diagnosed that a failure has occurred in the noise reduction circuit, stopping a switching circuit connected to the load, waiting for a predetermined time, and then restarting the operation of the switching circuit; A noise reduction method comprising:

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