Noise Attenuation Circuit

Abstract

To provide a noise attenuation circuit capable of improving an attenuation effect of a common mode noise.SOLUTION: A noise attenuation circuit 5 is a circuit that is provided between a power accumulation device 2 and an inverter 4 that converts a DC power supplied from the power accumulation device 2 to an AC power and outputs the power to a motor M, and generates an attenuation current for attenuating a noise current generated in the inverter 4. The noise attenuation circuit comprises: an auxiliary coil 50 that is wound to a core of a first common mode coil 31 and a second common mode coil 32, provided between the power accumulation device 2 and the inverter 4; a conversion circuit 51 that amplifies a current detected by the auxiliary coil 50, and converts the current to the attenuation current; a voltage supply circuit 52 that supplies a power supply voltage to the conversion circuit 51; and a control circuit 53 that changes a voltage value of the power supply voltage on the basis of a voltage value of a power accumulation voltage as a voltage of the power accumulation device 2 or a rotational number of the motor M.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to noise attenuation circuits. [Background technology]

[0002] Canceller circuits that attenuate common-mode noise generated in motors and the like are known. For example, Patent Document 1 describes a common-mode noise cancellation circuit device that includes a primary coil provided between a DC high-voltage power supply and a three-phase inverter circuit, a secondary coil electromagnetically coupled to the primary coil, and a noise cancellation circuit. In this device, when a common-mode current flows through the primary coil, a common-mode voltage is generated in the secondary coil, and a common-mode cancellation current that is opposite in phase to the common-mode current is generated by the noise cancellation circuit based on the common-mode voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-333647 Summary of the Invention [Problem to be solved by the invention]

[0004] Since the common-mode current can vary depending on the operating conditions, the common-mode voltage detected by the secondary coil can also vary. For example, if the common-mode voltage becomes higher than the power supply voltage of the canceller circuit, the canceller circuit may not operate properly and may not be able to sufficiently attenuate the common-mode noise.

[0005] The present disclosure describes a noise attenuation circuit that can improve the attenuation effect of common-mode noise. [Means for solving the problem]

[0006] A noise attenuation circuit according to one aspect of the present disclosure is provided between a power storage device and an inverter that converts DC power supplied from the power storage device into AC power and outputs it to a motor, and generates an attenuation current for attenuating noise current generated in the inverter. The noise attenuation circuit includes an auxiliary coil wound around the core of a common mode coil provided between the power storage device and the inverter, a conversion circuit that amplifies the current detected by the auxiliary coil and converts it into an attenuation current, a voltage supply circuit that supplies a power supply voltage to the conversion circuit, and a control circuit that changes the voltage value of the power supply voltage based on the voltage value of a storage voltage, which is the voltage of the power storage device, or the rotation speed of the motor.

[0007] In this noise attenuation circuit, the value of the power supply voltage is set based on the voltage value of the storage voltage of the power storage device or the rotation speed of the motor, and the power supply voltage is supplied to the conversion circuit. The common-mode voltage can vary depending on the storage voltage and the rotation speed of the motor. For example, as the storage voltage increases, the common-mode voltage also increases. Therefore, by taking into account the voltage value of the storage voltage or the rotation speed of the motor, the voltage value of the power supply voltage of the conversion circuit can be set to the voltage value of the power supply voltage required for the conversion circuit to operate normally. As a result, it is possible to improve the attenuation effect of common-mode noise.

[0008] In some embodiments, the voltage supply circuit may generate the power supply voltage based on the stored voltage. In this configuration, there is no need to provide a separate power supply circuit for the power supply voltage of the conversion circuit, so the noise attenuation circuit can be made smaller. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to improve the effect of attenuating common-mode noise. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a power supply device including a noise attenuation circuit according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a noise attenuation circuit according to an embodiment will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0012] The configuration of a power supply device including a noise attenuation circuit according to one embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of a power supply device including a noise attenuation circuit according to one embodiment. The power supply device 1 shown in Fig. 1 is a device that supplies AC power to a motor M. The power supply device 1 includes a power storage device 2, a main circuit 3, an inverter 4, a noise attenuation circuit 5, and a power transformer 6. In the power supply device 1, the noise current In generated in the inverter 4 is attenuated by the noise attenuation circuit 5.

[0013] The power storage device 2 supplies DC power to the inverter 4. The power storage device 2 can be used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 2 is configured by, for example, a lithium-ion battery, a lead-acid battery, or a nickel-metal hydride battery. The storage voltage, which is the voltage of the power storage device 2, can vary depending on the type of the power storage device 2 and the amount of electricity stored in the power storage device 2. The storage voltage is the open-circuit voltage of the power storage device 2. In other words, the storage voltage is the voltage between the positive terminal and the negative terminal of the power storage device 2.

[0014] The main circuit 3 includes a first common mode coil 31, a second common mode coil 32, a first connecting line 33, a second connecting line 34, a capacitor 35, and a capacitor 36. The first common mode coil 31 and the second common mode coil 32 are wound around a core made of a magnetic material to form a common mode choke coil.

[0015] In the common mode choke coil, when a common mode current (hereinafter referred to as "common mode current") flows through the first common mode coil 31 and the second common mode coil 32, magnetic flux is generated by the electromagnetic induction phenomenon in the first common mode coil 31 and the second common mode coil 32. In this case, the generated magnetic fluxes are oriented in the same direction, and the magnetic fluxes reinforce each other, causing the common mode choke coil to function as an inductor. When a differential mode current flows through the first common mode coil 31 and the second common mode coil 32, the generated magnetic fluxes are oriented in opposite directions, causing the magnetic fluxes to cancel each other out. As a result, the common mode choke coil does not function as an inductor for differential mode currents.

[0016] The first common mode coil 31 and the second common mode coil 32 are provided between the power storage device 2 and the inverter 4. One end of the first common mode coil 31 is connected to the positive terminal of the power storage device 2. The other end of the first common mode coil 31 is connected to a first connection line 33. One end of the second common mode coil 32 is connected to the negative terminal of the power storage device 2. The other end of the second common mode coil 32 is connected to a second connection line 34.

[0017] The first connecting line 33 connects the first common mode coil 31 and the inverter 4. Specifically, one end of the first connecting line 33 is connected to the other end of the first common mode coil 31. The other end of the first connecting line 33 is connected to the inverter 4.

[0018] The second connecting line 34 connects the second common mode coil 32 and the inverter 4. Specifically, one end of the second connecting line 34 is connected to the other end of the second common mode coil 32. The other end of the second connecting line 34 is connected to the inverter 4.

[0019] The capacitors 35 and 36 are Y capacitors and are provided between the first connection line 33 and the ground potential (earth) and between the second connection line 34 and the ground potential (earth). Specifically, one end of the capacitor 35 is connected to the first connection line 33. The other end of the capacitor 35 is connected to the ground potential (earth). One end of the capacitor 36 is connected to the ground potential (earth). The other end of the capacitor 36 is connected to the second connection line 34.

[0020] The inverter 4 converts DC power, which is input power supplied from the power storage device 2, into AC power and outputs it to the motor M. In this embodiment, the inverter 4 is a three-phase inverter and has a plurality of switching elements (not shown). The switching elements are elements that can be electrically switched between open and closed. Examples of switching elements that can be used include MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), and bipolar transistors. The inverter 4 includes a drive circuit (not shown), and a power supply voltage is supplied to the drive circuit from a power transformer 6.

[0021] The noise attenuation circuit 5 is a circuit that generates an attenuation current Ic for attenuating the noise current In generated in the inverter 4. The noise attenuation circuit 5 is provided between the power storage device 2 and the inverter 4. The noise attenuation circuit 5 has an auxiliary coil 50, a conversion circuit 51, a voltage supply circuit 52, and a control circuit 53. The noise attenuation circuit 5 detects a common mode current in the auxiliary coil 50 and generates an attenuation current Ic that is in opposite phase to the common mode current, thereby attenuating the noise current In generated in the inverter 4.

[0022] The auxiliary coil 50 is wound around the cores of the first common mode coil 31 and the second common mode coil 32, and detects the common mode current. One end of the auxiliary coil 50 is connected to a ground potential (earth). The other end of the auxiliary coil 50 is connected to a conversion circuit 51. The auxiliary coil 50 outputs the detected common mode current to the conversion circuit 51.

[0023] The conversion circuit 51 amplifies the common mode current detected by the auxiliary coil 50 and converts it into an attenuation current Ic. An input terminal of the conversion circuit 51 is connected to the other end of the auxiliary coil 50. An output terminal of the conversion circuit 51 is connected to the second connection line 34. The conversion circuit 51 generates a current that is opposite in phase to the common mode current and outputs it as the attenuation current Ic, thereby attenuating the noise current In generated in the inverter 4. The conversion circuit 51 includes an amplifier circuit (not shown) that amplifies the common mode current. A power supply voltage is supplied to the amplifier circuit from a voltage supply circuit 52. Note that the conversion circuit 51 only needs to be able to generate the attenuation current Ic from the common mode current, and as such a circuit configuration is well known, a detailed description thereof will be omitted here.

[0024] The voltage supply circuit 52 is a circuit that supplies a power supply voltage to the conversion circuit 51. For example, a DC / DC converter and a voltage regulator circuit are used as the voltage supply circuit 52. The voltage supply circuit 52 receives a signal for changing (setting) the voltage value of the power supply voltage from the control circuit 53, and changes (sets) the voltage value of the power supply voltage to be supplied to the conversion circuit 51 based on the signal. The voltage supply circuit 52 generates a power supply voltage based on the stored voltage of the power storage device 2. Specifically, the voltage supply circuit 52 converts the voltage supplied from the power transformer 6 to generate a power supply voltage having a voltage value set by the control circuit 53.

[0025] The control circuit 53 is a circuit that changes the voltage value of the power supply voltage supplied to the conversion circuit 51. In this embodiment, the control circuit 53 has a table that defines the relationship between the voltage value of the storage voltage, the rotation speed of the motor M, and the voltage value of the power supply voltage required for the conversion circuit 51 (hereinafter, may be referred to as the "required voltage value"). In other words, the table sets the required voltage values ​​for various combinations of the voltage value of the storage voltage and the rotation speed of the motor M.

[0026] A method for setting the required voltage value will now be described in detail. For the conversion circuit 51 to operate normally, a power supply voltage equal to or greater than the common-mode voltage must be supplied to the conversion circuit 51. For this reason, the power supply device 1 is operated for each combination (voltage value of the storage voltage and the rotation speed of the motor M) and the common-mode voltage generated in the auxiliary coil 50 is measured, and the required voltage value is determined based on the measured value of the common-mode voltage. The required voltage value may be, for example, equal to the measured value or greater than the measured value.

[0027] The control circuit 53 changes (sets) the voltage value of the power supply voltage supplied to the conversion circuit 51 based on the voltage value of the storage voltage and the rotation speed of the motor M. Specifically, the control circuit 53 acquires the voltage value of the storage voltage and the rotation speed of the motor M, and acquires, from the table, a required voltage value corresponding to the combination of the acquired voltage value of the storage voltage and the rotation speed of the motor M. Then, the control circuit 53 outputs a signal to the voltage supply circuit 52 to change (set) the voltage value of the power supply voltage of the conversion circuit 51 to the required voltage value.

[0028] The control circuit 53 acquires the voltage value of the stored voltage from, for example, a voltage sensor provided between the positive and negative terminals of the power storage device 2. In this embodiment, the control circuit 53 also functions as a control unit for the inverter 4. Therefore, the control circuit 53 supplies a control signal to the inverter 4 so that the motor M is driven at a predetermined rotation speed, and therefore knows the rotation speed of the motor M. The control circuit 53 may acquire the rotation speed of the motor M from a rotation sensor provided in the motor M, or may calculate the rotation speed of the motor M based on the motor current or motor voltage.

[0029] The power transformer 6 is connected to the power storage device 2. The power transformer 6 converts the stored voltage of the power storage device 2 into a voltage to be supplied to the drive circuit of the inverter 4 and the noise attenuation circuit 5, and supplies the converted voltage to the drive circuit of the inverter 4 and the noise attenuation circuit 5.

[0030] Next, the operation of the power supply device 1 will be described with reference to FIG.

[0031] When DC power is supplied from the power storage device 2 to the inverter 4, a noise current In is generated by the switching operation of the inverter 4. At this time, a common mode current flows through the first common mode coil 31 and the second common mode coil 32, and the auxiliary coil 50 detects the common mode current flowing through the first common mode coil 31 and the second common mode coil 32. Then, the conversion circuit 51 generates an attenuation current Ic having an opposite phase to the common mode current from the common mode current detected by the auxiliary coil 50, and supplies the attenuation current Ic to the inverter 4 (second connection line 34). This attenuates the noise current In.

[0032] Here, the control circuit 53 acquires the voltage value of the stored voltage of the power storage device 2 and the rotation speed of the motor M, and determines the required voltage value according to the combination of these values ​​by referring to the table. Then, the control circuit 53 outputs a signal to the voltage supply circuit 52 to change (set) the voltage value of the power supply voltage of the conversion circuit 51 to the required voltage value. As a result, the power supply voltage of the required voltage value is supplied to the conversion circuit 51.

[0033] Next, the effects of the noise attenuation circuit 5 will be described. Because the storage voltage of the power storage device 2 is the input voltage of the inverter 4, as the storage voltage increases, the noise current In (common mode current) also increases. Furthermore, when the rotation speed of the motor M changes, the magnitude of the noise current In can also fluctuate. The common mode voltage generated in the auxiliary coil 50 fluctuates according to the common mode current detected in the auxiliary coil 50. At this time, in order for the conversion circuit 51 to operate normally, it is necessary for a power supply voltage equal to or greater than the common mode voltage to be supplied to the conversion circuit 51.

[0034] In the noise attenuation circuit 5, the voltage value of the power supply voltage supplied to the conversion circuit 51 is set based on the voltage value of the storage voltage of the power storage device 2 and the rotation speed of the motor M. Therefore, by taking the voltage value of the storage voltage and the rotation speed of the motor into consideration, the voltage value of the power supply voltage supplied to the conversion circuit 51 can be set to the voltage value of the power supply voltage necessary for the conversion circuit 51 to operate normally. As a result, it is possible to improve the attenuation effect of common mode noise.

[0035] Specifically, the voltage value of the power supply voltage supplied to the conversion circuit 51 is set to a required voltage value corresponding to the combination of the voltage value of the storage voltage and the rotation speed of the motor M. Therefore, it is possible to prevent an excessively high power supply voltage from being supplied to the conversion circuit 51, thereby improving the attenuation effect of common mode noise and reducing losses in the conversion circuit 51.

[0036] The voltage supply circuit 52 generates the power supply voltage based on the stored voltage. Therefore, there is no need to provide a separate power supply circuit for the power supply voltage of the conversion circuit 51, and the power supply device 1 and the noise attenuation circuit 5 can be made smaller.

[0037] Although one embodiment of the present disclosure has been described in detail above, the noise attenuation circuit according to the present disclosure is not limited to the above embodiment.

[0038] In the above embodiment, the voltage supply circuit 52 generates the power supply voltage for the conversion circuit 51 based on the stored voltage of the power storage device 2, but this is not limiting. For example, the voltage supply circuit 52 may generate the power supply voltage for the conversion circuit 51 based on a voltage supplied from a power source other than the power storage device 2.

[0039] The control circuit 53 does not have to function as a control unit for the inverter 4. In other words, the power supply device 1 may include a control unit for the inverter 4 in addition to the control circuit 53.

[0040] The control circuit 53 may change (set) the voltage value of the power supply voltage of the conversion circuit 51 based on either the voltage value of the stored voltage of the power storage device 2 or the rotation speed of the motor M.

[0041] For example, the control circuit 53 may have a table that defines the relationship between the voltage value of the storage voltage and the required voltage value. The required voltage value stored in the table is determined based on the measurement value of the common mode voltage generated in the auxiliary coil 50 by operating the power supply device 1 at each voltage value of the storage voltage. For example, the required voltage value is set to a value obtained by adding the maximum increase in the common mode voltage due to the rotation speed of the motor M to the measurement value of the common mode voltage. By using this table, the control circuit 53 can change (set) the voltage value of the power supply voltage of the conversion circuit 51 based on the voltage value of the storage voltage. The same applies when changing (setting) the voltage value of the power supply voltage of the conversion circuit 51 based on the rotation speed of the motor M.

[0042] As described above, the common mode voltage can vary depending on the voltage value of the storage voltage and the rotation speed of the motor M. Therefore, by taking into consideration at least one of the voltage value of the storage voltage and the rotation speed of the motor M, it is possible to set the voltage value of the power supply voltage supplied to the conversion circuit 51 to the voltage value of the power supply voltage necessary for the conversion circuit 51 to operate normally. As a result, it is possible to improve the attenuation effect of common mode noise. [Explanation of symbols]

[0043] 1...power supply device, 2...power storage device, 4...inverter, 5...noise attenuation circuit, 6...power transformer, 31...first common mode coil, 32...second common mode coil, 50...auxiliary coil, 51...conversion circuit, 52...voltage supply circuit, 53...control circuit, M...motor.

Claims

1. A noise attenuation circuit is provided between a power storage device and an inverter that converts DC power supplied from the power storage device into AC power and outputs the AC power to a motor, and generates an attenuation current for attenuating a noise current generated in the inverter, an auxiliary coil wound around a core of a common mode coil provided between the power storage device and the inverter; a conversion circuit that amplifies the current detected by the auxiliary coil and converts it into the attenuated current; a voltage supply circuit that supplies a power supply voltage to the conversion circuit; a control circuit that acquires a voltage value of a storage voltage, which is a voltage of the storage device, or a rotation speed of the motor, and changes the voltage value of the power supply voltage according to the voltage value of the storage voltage or the rotation speed of the motor so that the power supply voltage becomes a required voltage value that is a voltage value equal to or greater than a common mode voltage; A noise attenuation circuit comprising:

2. The noise attenuation circuit of claim 1 , wherein the voltage supply circuit generates the power supply voltage based on the stored voltage.

3. A noise attenuation circuit as described in claim 1 or claim 2, wherein the control circuit obtains the rotation speed of the motor by calculating the rotation speed of the motor based on the motor current or motor voltage.

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