Power converters, power modules

Abstract

To provide a technique capable of suppressing conduction noise or radiation noise due to series resonance generated in a DC wiring unit or a power conversion unit by a simpler configuration.SOLUTION: A power conversion device 20 according to one embodiment comprises: a positive line PL and a negative line NL to which DC voltage is applied; an inverter circuit 24 connected to one end of the positive line PL and the negative line NL, converting the DC power supplied through the positive line PL and the negative line NL to a prescribed power on the basis of a switching operation of a semiconductor switch 24S connected between the positive line PL and the negative line NL, and outputting the converted power; and a semiconductor switch 26S connected between the positive line PL and the negative line NL and having a larger capacitance than the semiconductor switch 24S when a DC voltage is applied to the positive line PL and the negative line NL or a semiconductor diode 26D and the semiconductor switch 26S connected between the positive line PL and the negative line NL and having a synthetic capacitance larger than the capacitance of the semiconductor switch 24S when a DC voltage is applied to the positive line PL and the negative line NL.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to power conversion devices, etc. [Background technology]

[0002] For example, there are known techniques for suppressing motor noise and radiated noise caused by series resonance in DC wiring sections including positive and negative lines, and in power conversion sections that convert DC power to a predetermined power based on the switching operation of semiconductor switch elements (see Patent Document 1).

[0003] Patent Document 1 describes how a noise suppression capacitor is connected between the positive and negative lines, and how the parallel resonance generated by the capacitance of the noise suppression capacitor and the parasitic inductance component of the DC wiring reduces noise caused by series resonance. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-042040 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, for example, if ceramic capacitors are used as noise suppression capacitors, protective measures may be necessary to account for short-circuit failures. Also, for example, if noise suppression capacitors are mounted inside a module containing semiconductor switch elements in the power conversion section, different thermal management measures may be required than those for the semiconductor switch elements. As a result, the configuration of the power conversion device becomes more complex, which may lead to increased assembly man-hours and larger power conversion devices and modules.

[0006] Therefore, in view of the above problems, an object is to provide a technology capable of suppressing conduction noise and radiation noise due to series resonance generated in a DC wiring part and a power conversion part with a simpler configuration.

Means for Solving the Problems

[0007] To achieve the above object, in one embodiment of the present disclosure, a positive line and a negative line to which a DC voltage is applied, a power conversion unit that is connected to one ends of the positive line and the negative line and converts and outputs DC power supplied through the positive line and the negative line into a predetermined power based on a switching operation of a first semiconductor switch element connected between the positive line and the negative line, A closed-loop circuit including the positive line, the negative line, and the first semiconductor switch element, a semiconductor element having a capacitance larger than the capacitance of the first semiconductor switch element, or a plurality of semiconductor elements having a combined capacitance larger than the capacitance of the first semiconductor switch element, which is connected between the positive line and the negative line and is operative when a DC voltage is applied to the positive line and the negative line, A power conversion device is provided.

[0008] Also, in another embodiment of the present disclosure, <C000097> A power module used in a power conversion device including a first positive line and a first negative line to which a DC voltage is applied, Connected to the first positive line and the first negative line, a positive line and Second a negative line to which a DC voltage is applied, Second and the Second positive line and Second the negative line, which are connected to one ends of the Second positive line and Second the negative line, and a power conversion unit that converts and outputs DC power supplied through the Second positive line and Second the negative line into a predetermined power based on a switching operation of a first semiconductor switch element connected between the the Second [[ID=#]]positive line and SecondConnected between the negative line and the aforementioned Second The positive line and the aforementioned Second When a DC voltage is applied to the negative line, one semiconductor element having a capacitance greater than the capacitance of the first semiconductor switch element, or the Second The positive line and the aforementioned Second Connected between the negative line and the aforementioned Second The positive line and the aforementioned Second The invention comprises a plurality of semiconductor elements whose combined capacitance is greater than that of the first semiconductor switch element when a DC voltage is applied to the negative line. 、 The power converter includes a closed-loop circuit comprising the first positive line and the second positive line, the first negative line and the second negative line, and the first semiconductor switch element. ru, A power module will be provided. [Effects of the Invention]

[0009] According to the above-described embodiment, conducted noise and radiated noise caused by series resonance occurring in the DC wiring section and power conversion section can be suppressed with a simpler configuration. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows an example of a drive system. [Figure 2] This figure shows a first example of a power conversion device. [Figure 3] This diagram illustrates the operation of the brake circuit when it is not in operation. [Figure 4] This is a comparison diagram showing the noise levels of a power converter according to a comparative example and a power converter according to an embodiment. [Figure 5] This figure shows a second example of a power conversion device. [Figure 6] This figure shows a second example of a power conversion device. [Figure 7] This diagram illustrates the operation of the brake circuit when it is not in operation. [Figure 8] This figure shows a third example of a power conversion device. [Figure 9] This figure shows a third example of a power conversion device. [Modes for carrying out the invention]

[0011] The embodiments will be described below with reference to the drawings.

[0012] [Overview of the drive system] Referring to Figure 1, an overview of the drive system 1 according to this embodiment will be described.

[0013] Figure 1 shows an example of the drive system 1.

[0014] As shown in Figure 1, the drive system 1 includes a load device 10 and a power converter 20.

[0015] The drive system 1 uses AC power supplied from the AC power source PS to output drive power for the load device 10 from the power converter 20, thereby driving the load device 10.

[0016] The load device 10 is the object to be driven by the drive system 1. The load device 10 is, for example, an electric motor.

[0017] The power converter 20 converts the AC power supplied from the AC power source PS (e.g., R phase, S phase, and T phase) into AC power of a predetermined voltage and frequency (e.g., U phase, V phase, and W phase) and outputs it to the load device 10.

[0018] [First example of a power converter] Next, a first example of the power conversion device 20 according to this embodiment will be described with reference to Figures 2 to 4.

[0019] <Structure> Figure 2 shows a first example of the power converter 20.

[0020] As shown in Figure 2, the power converter 20 includes an input terminal 21, a rectifier circuit 22, a positive line PL and a negative line NL, a smoothing circuit 23, an inverter circuit 24, a snubber circuit 25, a brake circuit 26, a braking resistor 27, and an output terminal 28.

[0021] Input terminal 21 is used to input AC power from an external source. Input terminal 21 includes input terminals 21R, 21S, and 21T, which are connected to the R, S, and T phase output lines of an external AC power supply PS, respectively.

[0022] The rectifier circuit 22 is configured to rectify the three-phase AC power input through the input terminal 21 and output DC power. The rectifier circuit 22 has positive and negative output terminals, each connected to one end of the positive line PL and the negative line NL, and can output DC power to the smoothing circuit 23 through the positive line PL and the negative line NL. As shown in Figure 2, for example, the rectifier circuit 22 includes six semiconductor diodes 22D. Specifically, it is a bridge-type full-wave rectifier circuit in which three sets of two semiconductor diodes 22D corresponding to upper and lower arms are provided, and the three sets of upper and lower arms are connected in parallel between the positive and negative output lines. The input terminals 21R, 21S, and 21T are connected to the midpoints of the respective upper and lower arms.

[0023] The positive line PL and the negative line NL are to which the DC voltage output from the rectifier circuit 22 is applied. The positive line PL and the negative line NL electrically connect the rectifier circuit 22 and the inverter circuit 24.

[0024] The smoothing circuit 23 suppresses and smooths the pulsations of the DC power output from the rectifier circuit 22 and the DC power regenerated from the inverter circuit 24.

[0025] As shown in Figure 2, for example, the smoothing circuit 23 includes a smoothing capacitor 23C.

[0026] The smoothing capacitor 23C may be provided in parallel with the rectifier circuit 22 and the inverter circuit 24, in a path connecting the positive line PL and the negative line NL.

[0027] The smoothing capacitor 23C smooths the DC power output from the rectifier circuit 22 and the DC power output (regenerated) from the inverter circuit 24, while repeatedly charging and discharging as needed.

[0028] The smoothing capacitor 23C may be a single unit. Alternatively, multiple smoothing capacitors 23C may be provided, and these multiple smoothing capacitors 23C may be connected in parallel or in series between the positive line PL and the negative line NL. Furthermore, the multiple smoothing capacitors 23C may be configured in a way that multiple series connections of two or more smoothing capacitors are connected in parallel between the positive line PL and the negative line NL.

[0029] Furthermore, for example, the smoothing circuit 23 may include a reactor.

[0030] The reactor may be provided on the positive line PL between the rectifier circuit 22 and the smoothing capacitor 23C (specifically, at the branching point of the path where the smoothing capacitor 23C is located).

[0031] The reactor generates a voltage to appropriately oppose changes in current, while smoothing the DC power output from the rectifier circuit 22 and the DC power output (regenerated) from the inverter circuit 24.

[0032] The inverter circuit 24 (an example of a power conversion unit) is connected to one end of the positive line PL and the negative line NL, and converts the DC power input through the positive line PL and the negative line NL into three-phase AC power of the desired voltage and frequency in U-phase, V-phase, and W-phase, and outputs it from the output terminal 28.

[0033] The inverter circuit 24 includes semiconductor switches 24S and semiconductor diodes 24D. Specifically, three sets of series connections (switch legs) of two semiconductor switches 24S corresponding to the upper and lower arms are provided, and the three sets of switch legs are connected in parallel between the positive line PL and the negative line NL. Then, output lines for the U phase, V phase, and W phase are drawn out from the midpoint of the upper and lower arms of the three sets of switch legs and connected to the output terminals 28 (output terminals 28U, 28V, and 28W) for the U phase, V phase, and W phase. The semiconductor diodes 24D are connected in parallel to each semiconductor switch 24S with the forward direction from the negative line NL to the positive line PL.

[0034] The semiconductor switch 24S (an example of the first semiconductor switch element) is, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Alternatively, the semiconductor switch 24S may be an IGBT (Insulated Gate Bipolar Transistor) or a HEMT (High Electron Mobility Transistor), etc. Furthermore, the semiconductor switch 24S may be constructed primarily from silicon (Si), silicon carbide (SiC), or gallium nitride (GaN). The same applies to the semiconductor switch 26S.

[0035] The snubber circuit 25 is located between the smoothing circuit 23 and the inverter circuit 24. The snubber circuit 25 includes a snubber capacitor 25C.

[0036] The snubber capacitor 25C is placed in the path connecting the positive line PL and the negative line NL between the smoothing circuit 23 and the inverter circuit 24. The snubber capacitor 25C is, for example, a film capacitor.

[0037] The snubber capacitor 25C absorbs the energy stored in the parasitic inductance component of the DC wiring section, including the positive line PL and the negative line NL, when the semiconductor switch 24S is switched off, thereby suppressing the surge voltage of the semiconductor switch 24S. This suppresses element damage caused by the surge voltage of the semiconductor switch 24S. The snubber capacitor 25C has a relatively large capacitance (for example, a capacitance of several hundred nF) from the viewpoint of its surge voltage suppression effect.

[0038] The brake circuit 26 is provided between the snubber capacitor 25C and the inverter circuit 24. The brake circuit 26 includes a semiconductor diode 26D and a semiconductor switch 26S connected in series in a path connecting the positive line PL and the negative line NL.

[0039] The semiconductor diode 26D (an example of a rectifier element) is positioned on the positive line PL side of the semiconductor switch 26S, such that its forward direction is from the negative line NL to the positive line PL. This allows the semiconductor diode 26D to channel the surge current that occurs when the semiconductor switch 26S switches from the ON state to the OFF state to the positive line PL.

[0040] The semiconductor switch 26S (an example of a first semiconductor element and a second semiconductor switch element) is positioned on the negative line NL side of the semiconductor diode 26D. Switching the semiconductor switch 26S on and off allows the brake circuit 26 to be switched on and off.

[0041] The midpoint BP of the semiconductor diode 26D and the semiconductor switch 26S is connected to the damping resistor 27.

[0042] When the brake circuit 26 is inactive, the semiconductor switch 26S is in the off state, and the path between the positive line PL and the negative line NL through the brake circuit 26 is blocked. On the other hand, when the brake circuit 26 is active, the semiconductor switch 26S is in the on state, and the path between the positive line PL and the negative line NL through the brake circuit 26 is conductive.

[0043] The brake circuit 26 operates, for example, when the load device 10 (motor) is stopped, especially when it is necessary to quickly and abruptly stop the load device 10. This allows the brake circuit 26 to supply a regenerative current equivalent to the regenerative energy traced back through the inverter circuit 24 to the braking resistor 27 when the load device 10 is stopped. As a result, the regenerative power is consumed by the braking resistor 27 in the form of heat energy, which in turn quickly removes the kinetic energy of the load device 10 and allows the load device 10 (motor) to be brought to abrupt stop.

[0044] The braking resistor 27 is an electrical resistor provided in the path connecting the positive line PL and the midpoint BP of the brake circuit 26.

[0045] As described above, the braking resistance 27 can be consumed by converting the regenerative current flowing through the brake circuit 26 into thermal energy.

[0046] Output terminal 28 is used to output AC power from the inverter circuit 24 to the outside. Output terminal 28 includes output terminal 28U, output terminal 28V, and output terminal 28W, which are connected to the U-phase, V-phase, and W-phase input lines of the external load device 10, respectively.

[0047] <Operation of the brake circuit when it is not activated> Next, with reference to Figures 3 and 4, the operation of the brake circuit 26 when it is not in operation will be explained.

[0048] Figure 3 is a diagram illustrating the operation of the brake circuit 26 when it is not in operation. Figure 4 is a comparison diagram showing the noise levels of the power converter according to the comparative example and the power converter 20 according to the embodiment. Specifically, Figure 4 shows the frequency spectrum 401 representing the noise level of the power converter according to the comparative example and the frequency spectrum 402 representing the noise level of the power converter 20 according to the embodiment.

[0049] Furthermore, the power conversion device in the comparative example differs from the power conversion device 20 in this example (first example) in that the brake circuit 26 and the braking resistor 27 are omitted.

[0050] As shown in Figure 3, the semiconductor diode 26D and the semiconductor switch 26S each have a parasitic capacitance C d1 and capacitance C sw1 Therefore, when the power converter 20 is operating and the brake circuit 26 is not operating, the semiconductor diode 26D and the semiconductor switch 26S function as capacitance components (capacitors) in the path connecting the positive line PL and the negative line NL.

[0051] When the brake circuit 26 is not operating, no current flows through the braking resistor 27, and therefore there is no voltage drop across the braking resistor 27. As a result, the potential of the positive line PL and the potential of the midpoint BP are approximately equal. Therefore, the voltage V applied to the semiconductor diode 26D is... d1 Then, the voltage V applied to the semiconductor switch 26S sw1 The following relationship (1) holds between them.

[0052]

number

[0053] Furthermore, the parasitic capacitance of semiconductor diode 26D and semiconductor switch 26S has the characteristic that it decreases as the applied voltage increases. Specifically, the parasitic capacitance of semiconductor diode 26D and semiconductor switch 26S is proportional to the -1 / 2 power of the applied voltage. Therefore, the parasitic capacitance C of semiconductor diode 26D d1 And the parasitic capacitance C of semiconductor switch 26S sw1 The following relationship (2) holds between them.

[0054]

number

[0055] Therefore, from equations (1) and (2), the combined capacitance C of the semiconductor diode 26D and semiconductor switch 26S connected in series is obtained. brake This is expressed by (3) below.

[0056]

number

[0057] In this example, when a DC voltage is applied to the positive line PL and the negative line NL, the parasitic capacitance C of the semiconductor switch 26S sw1is set larger than the parasitic capacitance of the semiconductor switch 24S of the inverter circuit 24. For example, by varying the chip area between the semiconductor switches 24S and 26S and adjusting the area of the PN junction, the parasitic capacitance C sw1 of the semiconductor switch 26S is set larger than the parasitic capacitance of the semiconductor switch 24S. Also, by varying the impurity density of the semiconductor and adjusting the width of the depletion layer, the parasitic capacitance C sw1 of the semiconductor switch 26S may be set larger than the parasitic capacitance of the semiconductor switch 24S. Further, by both of these, the parasitic capacitance C sw1 of the semiconductor switch 26S may be set larger than the parasitic capacitance of the semiconductor switch 24S. Thereby, from the relationship of Equation (3), the combined capacitance C brake of the semiconductor diode 26D and the semiconductor switch 26S of the brake circuit 26 can be made larger than the parasitic capacitance of the semiconductor switch 24S of the inverter circuit 24.

[0058] Also, as described above, the snubber capacitor 25C has a relatively large capacitance of, for example, several hundred nF level from the viewpoint of the surge voltage suppression effect. On the other hand, the parasitic capacitance of the semiconductor switch 26S is generally on the order of several tens of pF to several nF. Therefore, the capacitance of the snubber capacitor 25C is overwhelmingly larger than the parasitic capacitance C sw1 of the semiconductor switch 26S. Thus, from the relationship of Equation (3), it can be said that the capacitance of the snubber capacitor 25C is overwhelmingly larger than the combined capacitance C brake of the semiconductor diode 26D and the semiconductor switch 26S of the brake circuit 26.

[0059] That is, in this example, the combined capacitance C brake of the semiconductor diode 26D and the semiconductor switch 26S connected in series between the positive line PL and the negative line NL is larger than the parasitic capacitance of the semiconductor switch 24S and smaller than the capacitance of the snubber capacitor 25C. Specifically, the parasitic capacitance C sw1The condition is met when the capacitance is set to be greater than the parasitic capacitance of the semiconductor switch 24S and less than the capacitance of the snubber capacitor 25C. The semiconductor switch 26S connects the positive line PL and the negative line NL via the damping resistor 27, thereby reducing the combined capacitance C of the semiconductor diode 26D and the semiconductor switch 26S. brake This is because it can be considered equal to the capacitance of the semiconductor switch 26S.

[0060] As a result, the combined capacitance C of the brake circuit 26 changes in conjunction with the switching operation of the semiconductor switch 24S. brake (That is, the capacitance C of the semiconductor switch 26S) sw1 ) and parasitic inductance components such as the wiring of the closed loop including the snubber circuit 25 and the brake circuit 26 can generate parallel resonance.

[0061] Here, during the switching operation of the semiconductor switch 24S, a series resonance occurs due to the capacitance of the semiconductor switch 24S and the parasitic inductance component of the closed-loop wiring including the semiconductor switch 24S and the snubber circuit 25. Therefore, for example, as shown in Figure 4 (frequency spectrum 401), in the power converter according to the comparative example, a very high level of noise peaking at the series resonance frequency fr1 is generated during the switching operation of the semiconductor switch 24S.

[0062] In contrast, in this example, as described above, parallel resonance can be generated by the action of the brake circuit 26 during the switching operation of the semiconductor switch 24S. Therefore, for example, as shown in Figure 4 (frequency spectrum 402), the noise caused by series resonance with a peak at series resonance frequency fr1 can be reduced by the parallel resonance at parallel resonance frequency fr2.

[0063] Furthermore, the brake circuit 26 does not function as a capacitance component because the semiconductor switch 26S is in the ON state (conductive state) when it is operating. However, the brake circuit 26 is used when the load device 10 stops, and at that time the inverter circuit 24 does not operate, so the switching operation of the semiconductor switch 24S does not occur when the brake circuit 26 is operating. Therefore, there is no need to suppress noise when the brake circuit 26 is operating, and no problem arises even if the brake circuit 26 does not function as a capacitance component.

[0064] Thus, in this example, when the brake circuit 26 is not operating, the parasitic capacitance components of the semiconductor diode 26D and the semiconductor switch 26S generate parallel resonance associated with the switching operation of the semiconductor switch 24S. This allows the noise caused by series resonance associated with the switching operation of the semiconductor switch 24S to be suppressed by the parallel resonance. Therefore, conducted noise and radiated noise caused by series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed.

[0065] Furthermore, in this example, the existing brake circuit 26 can be utilized. Therefore, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed without adding any new components. In other words, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed with a simpler configuration. Thus, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed while keeping the assembly man-hours and size of the power conversion device 20 under control.

[0066] Furthermore, if, for example, a ceramic capacitor is used as the capacitance component, protective measures may be necessary to account for short-circuit failures. As a result, the addition of components and structural complexity associated with these protective measures may lead to an increase in the assembly time and size of the power converter 20.

[0067] In contrast, in this example, the capacitance component is realized by the semiconductor diode 26D and semiconductor switch 26S of the brake circuit 26, thus eliminating the need for the aforementioned protection measures. Therefore, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed with a simpler configuration. Thus, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed while keeping the assembly man-hours and size of the power converter 20 under control.

[0068] [Second example of a power converter] Next, the power conversion device 20 according to this embodiment will be described with reference to Figures 5 to 7.

[0069] The following explanation will focus on the differences from the first example described above, and explanations that are the same as or correspond to the first example may be omitted.

[0070] <Structure> Figures 5 and 6 show a second example of the power converter 20. Specifically, Figure 5 shows the state in which the braking resistor 27 is connected to the connection terminal 29 of the power converter 20, and Figure 6 shows the state in which the braking resistor 27 is not connected to the connection terminal 29 of the power converter 20.

[0071] As shown in Figures 5 and 6, the power converter 20 in this example differs from the first example described above in that it is configured to allow the user to attach an external braking resistor 27 at their discretion.

[0072] The power converter 20 includes an input terminal 21, a rectifier circuit 22, a smoothing circuit 23, an inverter circuit 24, a snubber circuit 25, a brake circuit 26, an output terminal 28, and a connection terminal 29.

[0073] The connection terminal 29 is used to connect the braking resistor 27. The connection terminal 29 includes connection terminals 29A and 29B to which each end of the braking resistor can be connected. The connection terminal 29 is provided, for example, on the surface of the housing of the power converter 20.

[0074] <Operation of the brake circuit when it is not activated> Figure 7 illustrates the operation of the brake circuit 26 when it is not in operation. Specifically, Figure 7 illustrates the operation of the brake circuit 26 when it is not in operation, with the braking resistor 27 not connected to the connection terminal 29.

[0075] As described above, the parasitic capacitance C of the semiconductor switch 26S sw1 The applied voltage V sw1 It is proportional to the -1 / 2 power of . Similarly, the parasitic capacitance C of semiconductor diode 26D d1 The applied voltage V d1 It is proportional to the -1 / 2 power of . Therefore, the parasitic capacitance C of the semiconductor switch 26S sw1 and the parasitic capacitance C of semiconductor diode 26D d1 The proportionality constant a sw1 ,a d1 Using this, it can be expressed by the following equations (4) and (5).

[0076]

number

[0077] In this example, the parasitic capacitance C of the semiconductor switch 26S and semiconductor diode 26D sw1 ,C d1 By adjusting as appropriate, the proportionality constant a sw1 ,a d1 Both are positive numbers greater than 0.

[0078] If the damping resistor 27 is not connected to the connection terminal 29, the voltage V applied to the semiconductor switch 26S sw1 and the voltage V applied to the semiconductor diode 26D d1 The voltage V is between the positive line PL and the negative line NL. pn Using this, it can be expressed in the following equations (6) and (7).

[0079]

number

[0080] Therefore, from equations (4) to (7), the combined capacitance C of the brake circuit 26 (semiconductor diode 26D and semiconductor switch 26S) when the braking resistor 27 is not connected to the connection terminal 29 is obtained. brake1 This is expressed by the following equation (8).

[0081]

number

[0082] On the other hand, when the braking resistor 27 is connected to the connection terminal 29, the combined capacitance C of the brake circuit 26 (semiconductor diode 26D and semiconductor switch 26S) brake2 The same relationship as in equations (1) to (3) of the first example above holds. Therefore, from equations (1) to (4), the equivalent capacitance C of the brake circuit 26 when the braking resistor 27 is connected to the connection terminal 29 can be found. brake2 This can be expressed by the following equation (9).

[0083]

number

[0084] Therefore, from equations (8) and (9), the combined capacitance C of the brake circuit 26 in the cases where the braking resistor 27 is not connected to the connection terminal 29 and when it is connected is obtained. brake1 ,C brake2 The following equation (10) holds true for this.

[0085]

number

[0086] Here, as mentioned above, the proportionality coefficient a sw1 ,a d1 Since each of them is a positive number, the following equation (11) holds.

[0087]

number

[0088] Therefore, from equations (10) and (11), the combined capacitance C of the brake circuit 26 in the cases where the braking resistor 27 is not connected to the connection terminal 29 and when it is connected. brake1 ,C brake2 The following equation (12) holds true for this.

[0089]

number

[0090] In this example, when a DC voltage is applied to the positive line PL and the negative line NL, the combined capacitance C of the brake circuit 26 when the braking resistor 27 is not connected to the connection terminal 29. brake1 This is set to be greater than the parasitic capacitance of the semiconductor switch 24S. For example, as described above, by adjusting the capacitance of the semiconductor diode 26D and the relative capacitances of the semiconductor switches 24S and 26S, the combined capacitance C of the brake circuit 26 is determined. brake1 This is set to be greater than the parasitic capacitance of the semiconductor switch 24S.

[0091] Furthermore, in this example, from equation (12), the combined capacitance C of the brake circuit 26 when a DC voltage is applied to the positive line PL and the negative line NL and a braking resistor 27 is connected to the connection terminal 29 is calculated. brake2 This becomes greater than the parasitic capacitance of the semiconductor switch 24S.

[0092] Furthermore, as mentioned above, the snubber capacitor 25C has a relatively large capacitance, for example, on the order of several hundred nF, from the viewpoint of its surge voltage suppression effect. On the other hand, the parasitic capacitance of the semiconductor switch 26S and semiconductor diode 26D is generally on the order of several tens of pF to several nF. Therefore, the capacitance of the snubber capacitor 25C is overwhelmingly larger than the parasitic capacitance of the semiconductor switch 26S and semiconductor diode 26D. Thus, the capacitance of the snubber capacitor 25C is equal to the combined capacitance C of the brake circuit 26.brake1 ,C brake2 It can be said that it is overwhelmingly larger than that.

[0093] In other words, in this example, regardless of the presence or absence of the damping resistor 27, the combined capacitance of the semiconductor diode 26D and the semiconductor switch 26S (an example of multiple semiconductor elements) is greater than the parasitic capacitance of the semiconductor switch 24S and less than the capacitance of the snubber capacitor 25C.

[0094] As a result, similar to the first example described above, parallel resonance can be generated in conjunction with the switching operation of the semiconductor switch 24S, due to the combined capacitance of the brake circuit 26 and the parasitic inductance component of the closed loop including the snubber circuit 25 and the brake circuit 26. Therefore, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed.

[0095] Furthermore, in this example, as in the first example described above, the existing brake circuit 26 can be used. Therefore, while suppressing an increase in assembly man-hours and size of the power converter 20, it is possible to suppress conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S.

[0096] Furthermore, in this example, as in the first example described above, the capacitance component is realized by the semiconductor diode 26D and semiconductor switch 26S of the brake circuit 26, thus eliminating the need for the protection measures described above when using a ceramic capacitor as the capacitance component. Therefore, it is possible to suppress conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S with a simpler configuration, while suppressing an increase in assembly man-hours and size of the power conversion device 20.

[0097] [Third example of a power converter] Next, with reference to Figure 8, a third example of the power converter 20 according to this embodiment will be described.

[0098] The following explanation will focus on the differences from the first and second examples described above, and explanations that are the same as or correspond to those in the first and second examples may be omitted.

[0099] <Structure> Figures 8 and 9 show a third example of the power converter 20. Specifically, Figure 8 shows the state in which the braking resistor 27 is connected to the connection terminal 31 of the power module 30, and Figure 9 shows the state in which the braking resistor 27 is not connected to the connection terminal 31 of the power module 30.

[0100] As shown in Figures 8 and 9, the power conversion device 20 in this example differs from the first and second examples described above in that it incorporates a power module 30 that has a brake circuit 26 and an inverter circuit 24 built into it.

[0101] The power converter 20 includes an input terminal 21, a rectifier circuit 22, a smoothing circuit 23, a snubber circuit 25, a brake circuit 26, an output terminal 28, and a power module 30.

[0102] The power module 30 includes an inverter circuit 24, a brake circuit 26, and connection terminals 31 and 32. In other words, the power module 30 is realized by incorporating the brake circuit 26 into a 6-in-1 type power module corresponding to the inverter circuit 24.

[0103] The connection terminal 31 includes connection terminals 31P, 31N, and 31B.

[0104] The connection terminal 31P is connected inside the power module 30 to one portion of the positive line PL that is drawn from the inverter circuit 24. The connection terminal 31P is used outside the power module 30 and inside the power converter 20 to connect to the other portion of the positive line that extends from the rectifier circuit 22.

[0105] Furthermore, as shown in Figure 8, the connection terminal 31P is used to connect one end of the braking resistor 27, both outside the power module 30 and inside the power converter 20.

[0106] The connection terminal 31N is connected inside the power module 30 to one portion of the negative line NL that is drawn from the inverter circuit 24. The connection terminal 31N is used outside the power module 30 and inside the power converter 20 to connect to the other portion of the negative line that extends from the rectifier circuit 22.

[0107] The connection terminal 31B is drawn out from the midpoint BP of the brake circuit 26 inside the power module 30. The connection terminal 31B is used to connect the other end of the braking resistor 27 outside the power module 30 and inside the power converter 20.

[0108] The connection terminal 32 includes connection terminals 32U, 32V, and 32W.

[0109] The connection terminal 32U is connected to the U-phase output line of the inverter circuit 24 inside the power module 30. The connection terminal 32U is used to connect to the output terminal 28U outside the power module 30 and inside the power converter 20.

[0110] The 32V connection terminal is connected to the V-phase output line of the inverter circuit 24 inside the power module 30. The 32V connection terminal is also used to connect to the 28V output terminal outside the power module 30 and inside the power converter 20.

[0111] The connection terminal 32W is connected to the W-phase output line of the inverter circuit 24 inside the power module 30. The connection terminal 32W is used to connect to the output terminal 28W outside the power module 30 and inside the power converter 20.

[0112] <Operation of the brake circuit when it is not activated> As shown in Figure 8, consider the case where it is predetermined that the braking resistor 27 will be connected to the power module 30.

[0113] In this case, similar to the first example described above, when a DC voltage is applied to the positive line PL and the negative line NL, the parasitic capacitance C of the semiconductor switch 26S sw1 This can be set to be greater than the parasitic capacitance of the semiconductor switch 24S of the inverter circuit 24. This will produce the same effects and benefits as in the first example described above.

[0114] Furthermore, as shown in Figures 8 and 9, we consider both cases: one in which the braking resistor 27 is connected to the power module 30 and incorporated into the power converter 20, and another in which the braking resistor 27 is not connected and incorporated into the power converter 20.

[0115] In this case, when a DC voltage is applied to the positive line PL and the negative line NL, the combined capacitance C of the brake circuit 26 when the braking resistor 27 is not connected to the connection terminal 29 is... brake1 This can be set to be greater than the parasitic capacitance of the semiconductor switch 24S. This produces the same effect as in the second example described above.

[0116] Furthermore, if, for example, a capacitor is incorporated into the power module 30 as a capacitance component instead of the brake circuit 26, then different thermal countermeasures will need to be applied to the capacitor than those for the semiconductor switch 24S and semiconductor diode 24D of the inverter circuit 24. As a result, the additional components and structural complexity associated with these additional thermal countermeasures may lead to an increase in the assembly time and size of the power conversion device 20.

[0117] In contrast, in this example, the capacitance component is realized by the semiconductor switch 26S and semiconductor diode 26D of the brake circuit 26, so the same thermal countermeasures as those for the semiconductor switch 24S and semiconductor diode 24D of the inverter circuit 24 can be used. Therefore, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed with a simpler configuration. Thus, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be suppressed while keeping the assembly man-hours and size of the power conversion device 20 under control.

[0118] [Other embodiments] The embodiments described above may be modified or altered as appropriate.

[0119] For example, in the embodiments described above (Examples 1 to 3), the smoothing circuit 23 (smoothing capacitor 23C) may be omitted.

[0120] Furthermore, for example, in the embodiments and their variations described above, the snubber circuit 25 may be omitted.

[0121] Furthermore, in the embodiments and their modifications described above, the power converter 20 may generate and output the drive power for the load device 10 using DC power input from an external DC power source. In this case, for example, input terminals capable of receiving DC power are added to the positive line PL and negative line NL of the power converter 20. In this case, the input terminal 21 and the rectifier circuit 22 may be omitted.

[0122] Furthermore, in the embodiments and modifications described above, for example, the brake circuit 26 may be replaced with any one or more semiconductor elements that act as a capacitance component to generate parallel resonance during the switching operation of the semiconductor switch 24S. The semiconductor elements are, for example, semiconductor switches or semiconductor diodes, as in the case where the brake circuit 26 is employed. In this case, one semiconductor element may be provided to connect the positive line PL and the negative line NL and to be non-conductive when a DC voltage is applied to the positive line PL and the negative line NL. The one semiconductor element may be configured to have a parasitic capacitance greater than that of the semiconductor switch 24S when a DC voltage is applied to the positive line PL and the negative line NL. Similarly, multiple semiconductor elements are connected in series on the path connecting the positive line PL and the negative line NL so as to be non-conductive when a DC voltage is applied to the positive line PL and the negative line NL. The multiple semiconductor elements may be configured so that their combined capacitance is greater than the parasitic capacitance of the semiconductor switch 24S when a DC voltage is applied to the positive line PL and the negative line NL. Furthermore, multiple semiconductor elements may be connected in parallel so that each connects the positive line PL and the negative line NL. In this case, the multiple semiconductor elements may be configured so that each has a capacitance greater than that of the semiconductor switch 24S when a DC voltage is applied to the positive line PL and the negative line NL. Also, in this case, the multiple semiconductor switches may be configured so that their capacitance increases as they move away from the inverter circuit 24. This makes it possible to generate parallel resonance during the switching operation of the semiconductor switch 24S due to the parasitic inductance component of the closed loop including two adjacent semiconductor elements and the parasitic capacitance of the semiconductor element with the larger capacitance. Therefore, conducted noise and radiated noise due to series resonance associated with the switching operation of the semiconductor switch 24S can be further suppressed.

[0123] Furthermore, for example, in the above-described embodiment (third example) and its modifications, the power converter 20 may incorporate three 2-in-1 type power modules instead of the power module 30, each containing only one upper and lower arm with two semiconductor switches 24S connected in series. In this case, at least one of the 2-in-1 type power modules may incorporate one or more semiconductor elements that act as capacitance components to generate parallel resonance during the switching operation of the semiconductor switches 24S.

[0124] Furthermore, the configuration for suppressing noise due to series resonance during the switching operation of the inverter circuit 24 in the above-described embodiments and modifications may also be applied to power converters having other types of inverter circuits. For example, it may be applied to power converters including inverter circuits that output AC power other than three phase (e.g., single phase) or multi-level inverter circuits.

[0125] Furthermore, for example, the configuration for suppressing noise due to series resonance during the switching operation of the inverter circuit in the above-described embodiments and modifications may also be applied to power converters having other types of power conversion units. For example, it may be applied to a power converter having a DC chopper that converts a DC voltage to a different DC voltage by the switching operation of a semiconductor switch, i.e., a DC (Direct Current)-DC converter.

[0126] [Effect] Next, the operation of the power converter 20 and power module 30 according to this embodiment will be described.

[0127] In this embodiment, the power conversion device 20 comprises a positive line PL and a negative line NL, a power conversion unit (e.g., an inverter circuit 24), and one or more semiconductor elements (e.g., a semiconductor diode 26D and a semiconductor switch 26S). Specifically, a DC voltage is applied to the positive line PL and the negative line NL. The power conversion unit is connected to one end of the positive line PL and the negative line NL, and based on the switching operation of a first semiconductor switch element (e.g., a semiconductor switch 24S) connected between the positive line PL and the negative line NL, it converts the DC power supplied through the positive line PL and the negative line NL into a predetermined power and outputs it. One semiconductor element is connected between the positive line PL and the negative line NL and has a capacitance greater than the capacitance of the first semiconductor switch element when a DC voltage is applied to the positive line PL and the negative line NL. Multiple semiconductor elements are connected between the positive line PL and the negative line NL and have a combined capacitance greater than the capacitance of the first semiconductor switch element when a DC voltage is applied to the positive line PL and the negative line NL.

[0128] As a result, parallel resonance can be generated by the parasitic inductance component of the DC wiring section, including the positive line PL and the negative line NL, and the capacitance component of one or more semiconductor elements, in conjunction with the switching operation of the first semiconductor switch element. Therefore, conducted noise and radiated noise caused by series resonance that occurs in the DC wiring section and power conversion section in conjunction with the switching operation of the first semiconductor switch element can be suppressed by parallel resonance. Consequently, for example, protective measures for short-circuit failures when using a ceramic capacitor as the capacitance component become unnecessary, and as a result, conducted noise and radiated noise caused by series resonance that occurs in the DC wiring section and power conversion section can be suppressed with a simpler configuration.

[0129] Furthermore, in this embodiment, the power converter 20 may also include a brake circuit 26. Specifically, the brake circuit 26 may include a semiconductor diode 26D and a semiconductor switch 26S connected in series between the positive line PL and the negative line NL. The aforementioned semiconductor element may be a semiconductor switch 26S.

[0130] This allows the semiconductor switch 26S of the brake circuit 26, which rapidly stops the load device 10 (motor), to suppress conducted noise and radiated noise caused by series resonance in the DC wiring section and power conversion section. Therefore, conducted noise and radiated noise caused by series resonance in the DC wiring section and power conversion section can be suppressed without adding any new components.

[0131] Furthermore, in this embodiment, the power converter 20 may also include a brake circuit 26. The plurality of semiconductor elements described above may also be semiconductor diodes 26D and semiconductor switches 26S.

[0132] As a result, conducted noise and radiated noise caused by series resonance occurring in the DC wiring section and power conversion section can be suppressed using the semiconductor diode 26D and semiconductor switch 26S of the brake circuit 26 for rapidly stopping the load device 10 (motor motor). Therefore, conducted noise and radiated noise caused by series resonance occurring in the DC wiring section and power conversion section can be suppressed without adding any new components.

[0133] Furthermore, in this embodiment, the power converter 20 may also include a damping resistor 27 connected between the positive line PL and the midpoint BP of the semiconductor diode 26D and the semiconductor switch 26S.

[0134] As a result, the semiconductor switch 26S of the brake circuit 26 connects the positive line PL and the negative line NL via the braking resistor 27. Therefore, by making the capacitance of the semiconductor switch 26S larger than the capacitance of the first semiconductor switch element, parallel resonance can be generated due to the capacitance component of the semiconductor switch 26S and the parasitic inductance component of the DC wiring section.

[0135] Furthermore, in this embodiment, the power conversion device 20 may also include a snubber capacitor 25C. Specifically, the snubber capacitor may be connected between the positive line PL and the negative line NL on the opposite side of the power conversion unit from the perspective of one or more semiconductor elements as described above.

[0136] This makes it possible to suppress conducted noise and radiated noise associated with series resonance caused by the capacitance component of the snubber capacitor and the parasitic inductance component of the DC wiring.

[0137] Furthermore, in this embodiment, the power conversion unit may be an inverter circuit 24 that converts the DC voltage applied to the positive line PL and the negative line NL into an AC voltage and outputs it.

[0138] This makes it possible to suppress conducted noise and radiated noise associated with series resonance occurring in the DC wiring section, including the positive line PL and the negative line NL, and in the inverter circuit 24.

[0139] In this embodiment, the power module 30 comprises a positive line PL and a negative line NL, a power conversion unit (e.g., an inverter circuit 24), and one or more semiconductor elements (e.g., a semiconductor diode 26D and a semiconductor switch 26S). Specifically, a DC voltage is applied to the positive line PL and the negative line NL. The power conversion unit is connected to one end of the positive line PL and the negative line NL, and based on the switching operation of a first semiconductor switch element (e.g., a semiconductor switch 24S) connected between the positive line PL and the negative line NL, it converts the DC power supplied through the positive line PL and the negative line NL into a predetermined power and outputs it. One semiconductor element is connected between the positive line PL and the negative line NL and has a capacitance greater than the capacitance of the first semiconductor switch element when a DC voltage is applied to the positive line PL and the negative line NL. Multiple semiconductor elements are connected between the positive line PL and the negative line NL and have a combined capacitance greater than the capacitance of the first semiconductor switch element when a DC voltage is applied to the positive line PL and the negative line NL.

[0140] As a result, as described above, conducted noise and radiated noise caused by series resonance in the DC wiring section and power conversion section due to the switching operation of the first semiconductor switch element can be suppressed by parallel resonance caused by the action of one or more semiconductor elements. Therefore, for example, the same or similar thermal countermeasures as those for the first semiconductor switch element can be applied to one or more semiconductor elements inside the power module 30. Thus, additional thermal countermeasures, such as those used when a capacitor is used as the capacitance component, become unnecessary, and conducted noise and radiated noise caused by series resonance in the DC wiring section and power conversion section can be suppressed with a simpler configuration.

[0141] Furthermore, in this embodiment, the power module 30 may also include a brake circuit 26. Specifically, the brake circuit 26 may include a semiconductor diode 26D and a semiconductor switch 26S connected in series between the positive line PL and the negative line NL. The aforementioned semiconductor element may be a semiconductor switch 26S.

[0142] This allows the semiconductor switch 26S of the brake circuit 26 built into the power module 30 to suppress conducted noise and radiated noise caused by series resonance in the DC wiring section and power conversion section. Therefore, conducted noise and radiated noise caused by series resonance in the DC wiring section and power conversion section can be suppressed without adding any new components.

[0143] Furthermore, in this embodiment, the power module 30 may also include a brake circuit 26. The plurality of semiconductor elements described above may also be semiconductor diodes 26D and semiconductor switches 26S.

[0144] This allows the semiconductor diode 26D and semiconductor switch 26S of the brake circuit 26 built into the power module 30 to suppress conducted noise and radiated noise caused by series resonance in the DC wiring section and power conversion section. Therefore, conducted noise and radiated noise caused by series resonance in the DC wiring section and power conversion section can be suppressed without adding any new components.

[0145] Although embodiments have been described in detail above, this disclosure is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist described in the claims. [Explanation of Symbols]

[0146] 1. Drive System 10 Load device 20 Power converter 21 Input terminals 21R Input Terminal 21S Input Terminal 21T Input Terminal 22 Rectifier circuit 22D semiconductor diode 23 Smoothing circuit 23C smoothing capacitor 24 Inverter Circuit 24D semiconductor diode 24S semiconductor switch 25 Snubber Circuit 25C Snubber Capacitor 26 Brake Circuit 26D semiconductor diode 26S semiconductor switch 27 Braking resistance 28 output terminals 28U output terminal 28V output terminal 28W output terminal 29 Connection terminals 29A Connection terminal 29B Connection terminal 30 Power Modules 31 Connection terminals 31B Connection terminal 31N Connection terminal 31P connector 32 connection terminals 32U connection terminals 32V connection terminal 32W connection terminal BP midpoint NL Negative Line PL (Positive Line) PS AC power supply

Claims

1. A positive line and a negative line to which a DC voltage is applied, A power conversion unit that converts the DC power supplied through the positive line and the negative line into a predetermined power and outputs it based on the switching operation of a first semiconductor switch element connected to one end of the positive line and the negative line and connected between the positive line and the negative line, A closed-loop circuit including the positive line, the negative line, and the first semiconductor switch element, The system comprises: a single semiconductor element connected between the positive line and the negative line, having a capacitance greater than that of the first semiconductor switch element when a DC voltage is applied to the positive line and the negative line; or a plurality of semiconductor elements connected between the positive line and the negative line, having a combined capacitance greater than that of the first semiconductor switch element when a DC voltage is applied to the positive line and the negative line. Power converter.

2. The brake circuit includes a rectifier element and a second semiconductor switch element connected in series between the positive line and the negative line, The first semiconductor element is the second semiconductor switch element. The power conversion device according to claim 1.

3. The brake circuit includes a rectifier element and a second semiconductor switch element connected in series between the positive line and the negative line, The plurality of semiconductor elements are the rectifier element and the second semiconductor switch element. The power conversion device according to claim 1.

4. The system includes a damping resistor connected between the positive line and the midpoint between the rectifier element and the second semiconductor switch element. The power conversion device according to claim 2.

5. The system includes a snubber capacitor connected between the positive line and the negative line on the side opposite to the power conversion unit when viewed from the one semiconductor element or the plurality of semiconductor elements, A power conversion device according to any one of claims 1 to 4.

6. The power conversion unit is an inverter circuit that converts the DC voltage applied to the positive line and the negative line into an AC voltage and outputs it. A power conversion device according to any one of claims 1 to 5.

7. A power module used in a power conversion device including a first positive line and a first negative line to which a DC voltage is applied, A second positive line and a second negative line are connected to the first positive line and the first negative line, respectively, and a DC voltage is applied to them. A power conversion unit that converts the DC power supplied through the second positive line and the second negative line into a predetermined power and outputs it, based on the switching operation of a first semiconductor switch element connected to one end of the second positive line and the second negative line and connected between the second positive line and the second negative line, The system comprises: a single semiconductor element connected between the second positive line and the second negative line, having a capacitance greater than that of the first semiconductor switch element when a DC voltage is applied to the second positive line and the second negative line; or a plurality of semiconductor elements connected between the second positive line and the second negative line, having a combined capacitance greater than that of the first semiconductor switch element when a DC voltage is applied to the second positive line and the second negative line. The power converter includes a closed-loop circuit comprising the first positive line and the second positive line, the first negative line and the second negative line, and the first semiconductor switch element. Power module.

8. The brake circuit includes a rectifier element and a second semiconductor switch element connected in series between the second positive line and the second negative line, The first semiconductor element is the second semiconductor switch element. The power module according to claim 7.

9. The brake circuit includes a rectifier element and a second semiconductor switch element connected in series between the second positive line and the second negative line, The plurality of semiconductor elements are the rectifier element and the second semiconductor switch element. The power module according to claim 7.

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