Circuit board for current detection

Abstract

A circuit board (100) for current detection according to the present disclosure comprises: a plurality of detection resistors (1a-1d); an input conductive pattern (10) that has a rectangular shape in which a first side (12) to which one end of each of the plurality of detection resistors is connected, and a first end part (13) and a second end part (14), which are end parts of the first side, are formed, a current to be detected being inputted into the detection resistors via a current input part (11); and an output conductive pattern (20) to which the other end of each of the plurality of detection resistors connected to the first side is connected, the current flowing through the detection resistors being outputted via a current output part (21). The detection resistors are arranged at equal intervals in a first direction along the first side, and are arranged such that a first end part-resistor interval (W1), which is the interval between the detection resistor closest to the first end part and the first end part, and a second end part-resistor interval (W2), which is the interval between the detection resistor closest to the second end part and the second end part, are less than or equal to 1 / 2 a resistor interval (Wr), which is the interval between adjacent detection resistors.

Description

Circuit board for current detection

[0001] The present disclosure relates to a circuit board for current detection.

[0002] As a method for detecting the current of a power converter or the like, there is a method of connecting a shunt resistor on a wiring through which current flows and detecting the current based on the voltage generated at both ends of the shunt resistor. However, when detecting the current by connecting a plurality of shunt resistors in parallel to suppress the heat generation of the shunt resistor, the current is divided among the plurality of shunt resistors. Therefore, due to factors such as the current distribution, variations occur in the current flowing through each shunt resistor, and the accuracy of detecting the current may decrease.

[0003] Therefore, it is necessary to use a technique for suppressing variations in the current flowing through shunt resistors connected in parallel. As a technique for suppressing variations in the current flowing through shunt resistors connected in parallel, for example, Patent Document 1 discloses an inverter device that suppresses variations in the current flowing through shunt resistors by adjusting the area of a conductive pattern to which the shunt resistors are connected and improves the current detection accuracy.

[0004] Japanese Patent Application Laid-Open No. 2017-011794

[0005] In the above inverter device, it is disclosed that variations in the current flowing through shunt resistors arranged in parallel are suppressed by changing the width of the conductive pattern to which the shunt resistors on the circuit board are connected and adjusting the area. However, in reality, due to constraints that occur when mounting the circuit board, such as the balance of the arrangement with other wirings on the same circuit board or the limitation of the circuit board size, it may not be possible to provide a conductive pattern with a sufficient width on the circuit board to suppress current variations.

[0006] The present disclosure has been made to solve the above problems, and provides a circuit board for current detection that can equalize the current flowing through each detection resistor and accurately detect the current without widening the width of the conductive pattern on the circuit board.

[0007] The current detection circuit board according to this disclosure comprises an insulating substrate, a plurality of detection resistors arranged on one surface of the insulating substrate, an input conductive pattern arranged on one surface and having a rectangular shape with a first side to which one end of the plurality of detection resistors is connected, and a first end and a second end which are the ends of the first side, and through which the current to be detected is input to the detection resistors via a current input section, and an output conductive pattern arranged on one surface and to which the other ends of the plurality of detection resistors connected to the first side are connected, and through which the current that has flowed through the detection resistors is output via a current output section, wherein the detection resistors are arranged at equal intervals in a first direction along the first side, and the first end resistance interval, which is the distance between the detection resistor closest to the first end and the first end, and the second end resistance interval, which is the distance between the detection resistor closest to the second end and the second end, are arranged to be less than or equal to half the resistance interval, which is the distance between adjacent detection resistors.

[0008] The current detection circuit board according to this disclosure has multiple detection resistors connected to the first side of an input conductive pattern, arranged at equal intervals along the first side, and the detection resistors are arranged such that the first end resistance interval and the second end resistance interval are less than half of the resistance interval. This prevents more current from flowing to the detection resistor closest to the first end and the detection resistor closest to the second end of the first side of the input conductive pattern than to other detection resistors. In this way, the width of the conductive pattern is restricted by making the first end resistance interval and the second end resistance interval shorter than the resistance interval, so that the current flowing through each detection resistor is equalized by adjusting the placement position of the detection resistors without widening the width of the conductive pattern on the circuit board, and the current can be detected with high accuracy.

[0009] This figure shows an example configuration of a current detection circuit board according to Embodiment 1. This figure shows a comparative example when the current flowing through the detection resistor varies. This figure shows an example configuration when the current flowing through the detection resistor is equalized according to Embodiment 1. This figure shows an analysis model of the current detection circuit board according to Embodiment 1. This figure shows the analysis results regarding the voltage fluctuation rate according to Embodiment 1. This figure shows the analysis results regarding the temperature fluctuation rate according to Embodiment 1. This figure shows an example configuration in which the current detection circuit board according to Embodiment 1 is mounted inside a power converter. This figure shows an example configuration of a current detection circuit board according to Embodiment 2. This figure shows a comparative example when the current flowing through the detection resistor varies. This figure shows an example configuration when the current flowing through the detection resistor is equalized according to Embodiment 2. This figure shows an analysis model of the current detection circuit board according to Embodiment 2. This figure shows the analysis results regarding the voltage fluctuation rate according to Embodiment 2. This figure shows an example configuration of a current detection circuit board according to Embodiment 2. This figure shows an example configuration of a current detection circuit board according to Embodiment 2. This figure shows an example configuration of a current detection circuit board according to Embodiment 2. This figure shows a comparative example when the current flowing through the detection resistor varies. This figure shows an example configuration of a current detection circuit board according to Embodiment 2. This figure shows an example configuration of a current detection circuit board according to Embodiment 2. This figure shows an example configuration of a current detection circuit board according to Embodiment 2. This figure shows an example configuration of a current detection circuit board according to Embodiment 3. This figure shows an example configuration of a current detection circuit board according to Embodiment 3.

[0010] The embodiments will be described in detail below with reference to the drawings. Note that the embodiments described below are illustrative examples. Furthermore, each embodiment can be combined as appropriate.

[0011] Embodiment 1. The current detection circuit board according to Embodiment 1 will be described with reference to Figures 1 to 7. Figure 1 is a diagram showing an example of the configuration of the current detection circuit board according to Embodiment 1. The current detection circuit board is constructed by mounting detection resistors 1a, 1b, 1c, 1d, an input conductive pattern 10, and an output conductive pattern 20 on one surface of an insulating substrate 100. In this embodiment, four detection resistors are used, but the number of detection resistors is not limited to this, and any number of detection resistors is acceptable.

[0012] The input conductive pattern 10 is arranged on one surface of the insulating substrate 100 and is a rectangular conductive pattern having a first side 12 and a first end 13 and a second end 14 which are the ends of the first side 12. One end of each of the detection resistors 1a, 1b, 1c, and 1d is connected in parallel to the first side 12 of the input conductive pattern 10. The input conductive pattern 10 has a current input section 11, and the current to be detected, input via the current input section 11, flows through the input conductive pattern 10 and is input to the detection resistors 1a, 1b, 1c, and 1d.

[0013] The output conductive pattern 20 is arranged on one surface of the insulating substrate 100 and is a rectangular conductive pattern having a second side 22 and third and fourth ends 23 and 24, which are the ends of the second side 22. The other ends of the detection resistors 1a, 1b, 1c, and 1d, which are connected to the first side 12, are connected in parallel to the second side 22 of the output conductive pattern 20. The output conductive pattern 20 has a current output section 21, and the current of the object to be detected that flows through the detection resistors 1a, 1b, 1c, and 1d flows through the output conductive pattern 20 and is output via the current output section 21.

[0014] The detection resistors 1a, 1b, 1c, and 1d are arranged on one surface of the insulating substrate 100 and connected to the input conductive pattern 10 and the output conductive pattern 20, and are current detection resistors through which the current to be detected flows. The detection resistors 1a, 1b, 1c, and 1d are arranged at equal intervals along the first side 12, and the resistance interval Wr, which is the distance between adjacent detection resistors, is the same value for all of them. Here, the distance between the detection resistor 1a closest to the first end 13 and the first end 13 is defined as the first end resistance interval W1, and the distance between the detection resistor 1d closest to the second end 14 and the second end 14 is defined as the second end resistance interval W2.

[0015] By connecting multiple detection resistors 1a, 1b, 1c, and 1d in parallel and distributing the current to be detected, the heat generated in each detection resistor 1a, 1b, 1c, and 1d can be reduced. On the other hand, because the current to be detected is divided, variations may occur in the current flowing through each detection resistor 1a, 1b, 1c, and 1d, potentially reducing the accuracy of current detection.

[0016] Figure 2 is a reference example, and a comparative example is described for cases where there is variation in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. Here, the white arrows shown on the input conductive pattern 10 in Figure 2 indicate the current flowing on the input conductive pattern 10 and input to the detection resistors 1a, 1b, 1c, and 1d. The current detection circuit board shown in Figure 2 is a current detection circuit board shown in Figure 1, with the spacing of the detection resistors 1a, 1b, 1c, and 1d changed.

[0017] In Figure 2, the detection resistors 1a, 1b, 1c, and 1d are arranged at equal intervals so as to be close to the center of the first side 12. In this case, the current inflow area, which is the area through which current flows to the detection resistor 1a closest to the first end 13, is larger than the current inflow areas for detection resistors 1b and 1c, respectively, so that more current flows into detection resistor 1a. Similarly, the current inflow area for detection resistor 1d closest to the second end 14 is larger than the current inflow areas for detection resistors 1b and 1c, respectively, so that more current flows into detection resistor 1d.

[0018] Thus, variations in the current flowing through each of the detection resistors 1a, 1b, 1c, and 1d occur because the current inflow areas for each of the detection resistors 1a, 1b, 1c, and 1d are different. Therefore, one way to suppress variations in the current flowing through each of the detection resistors 1a, 1b, 1c, and 1d is to make the current inflow areas for each of the detection resistors 1a, 1b, 1c, and 1d the same.

[0019] Using Figure 3, an example configuration in which variations in the current flowing through each detection resistor 1a, 1b, 1c, and 1d are suppressed will be explained. Here, the white arrows shown on the input conductive pattern 10 in Figure 3 indicate the current flowing along the input conductive pattern 10 and input to the detection resistors 1a, 1b, 1c, and 1d.

[0020] In Figure 3, in order to equalize the current inflow area for multiple detection resistors 1a, 1b, 1c, and 1d, the spacing between the detection resistors 1a, 1b, 1c, and 1d is adjusted so that the width of the current inflow area is the same. For example, by arranging the detection resistors 1a, 1b, 1c, and 1d at equal intervals along the first side 12, and arranging them so that the first end resistance spacing W1 and the second end resistance spacing W2 are half the resistance spacing Wr, the width of the current inflow area for multiple detection resistors 1a, 1b, 1c, and 1d is equalized, as shown in Figure 3. By equalizing the width of the current inflow area for multiple detection resistors 1a, 1b, 1c, and 1d, the current flowing into each detection resistor 1a, 1b, 1c, and 1d becomes approximately the same, and the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized.

[0021] Next, we will explain the necessary conditions for equalizing the current inflow area for detection resistors 1a, 1b, 1c, and 1d, and for equalizing the current flowing through each detection resistor 1a, 1b, 1c, and 1d. In Figure 3, the detection resistors 1a, 1b, 1c, and 1d are arranged symmetrically vertically. In this case, the resistance spacing W1 at the first end and the resistance spacing W2 at the second end are the same value, so the following equation (1) holds: W1 = W2 (1)

[0022] Furthermore, if the resistance gap Wr is α times the resistance gap W1 at the first end, then the resistance gap Wr can be expressed by the following equation (2): Wr = αW1 (2)

[0023] Next, let the direction along the first side 12, which is the direction of A1 shown in Figure 3, be defined as the first direction. If the detection resistance width, which is the length of the detection resistors 1a, 1b, 1c, 1d in the first direction, is Ws, and the number of detection resistors 1a, 1b, 1c, 1d is N, then the input conductivity pattern width, which is the length of the input conductivity pattern 10 in the first direction, is expressed by the following equation (3): Wp = 2W1 + (N-1)αW1 + NWs = {2 + α(N-1)W1} + NWs (3)

[0024] If we subtract the term relating to the detection resistance width Ws from the input conductive pattern width Wp and divide by the number of detection resistors N, then Wn is expressed by the following equation (4): Wn = {2 + α(N-1)W1} / N (4)

[0025] By arranging the detection resistors 1a, 1b, 1c, and 1d such that the sum of Wn shown in equation (4) and the detection resistance width Ws equals the current inflow width, which is the width of the current inflow area in the first direction for each detection resistor 1a, 1b, 1c, and 1d, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized. In order for the sum of Wn and the detection resistance width Ws to equal the current inflow width, the first end resistance spacing W1 must be smaller than Wn, and this condition is expressed by the following equation (5): W1 < Wn (5)

[0026] Therefore, equation (6) is derived from equations (4) and (5): α > (N-2) / (N-1) (6)

[0027] Therefore, in order to equalize the current inflow width of the current inflow area for each detection resistor 1a, 1b, 1c, and 1d, and to equalize the current flowing through each detection resistor 1a, 1b, 1c, and 1d, equation (6) is a necessary condition.

[0028] Next, we will explain the analysis and results regarding the relationship between the placement of the multiple detection resistors 1a, 1b, 1c, and 1d and the variation in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. The analysis model used for the analysis is shown in Figure 4, and the analysis results are shown in Figures 5 and 6. The detection resistors 1a, 1b, 1c, and 1d, the input conductive pattern 10, and the output conductive pattern 20 shown in Figure 4 are arranged symmetrically with respect to the dashed line shown in Figure 4, and the relationships shown in equations (1) and (2) hold. Because the analysis model is designed to be symmetrical with respect to the dashed line shown in Figure 4, the flow of current input from the current input unit 11, flowing through the input conductive pattern 10, detection resistors 1a, 1b, 1c, and 1d, and output conductive pattern 20, and output from the current output unit 21 is also symmetrical with respect to the dashed line shown in Figure 4. Therefore, during the analysis, the current flow was calculated only on either the upper or lower side of the dashed line shown in Figure 4, thereby calculating the voltage generated at each of the detection resistors 1a, 1b, 1c, and 1d, as well as their respective temperatures.

[0029] Using the analysis model shown in Figure 4, the ratio α of the resistance spacing Wr to the first end resistance spacing W1 was changed, and current was input from the current input unit 11. When the current flowed through the input conductive pattern 10, detection resistors 1a, 1b, 1c, 1d, and output conductive pattern 20, and current was output from the current output unit 21, the voltage generated at each of the detection resistors 1a, 1b, 1c, and 1d, and their respective temperatures were calculated. The voltage fluctuation rate and temperature fluctuation rate, which show the variation in voltage and temperature at each detection resistor 1a, 1b, 1c, and 1d, are shown in Figures 5 and 6. Figure 5 is a diagram showing the voltage fluctuation rate related to the voltage generated at each detection resistor 1a, 1b, 1c, and 1d calculated using the analysis model in Figure 4, and Figure 6 is a diagram showing the temperature fluctuation rate related to the temperature of each detection resistor 1a, 1b, 1c, and 1d calculated using the analysis model in Figure 4.

[0030] Here, if we let Vnmax be the maximum value of the voltages generated by the detection resistors 1a, 1b, 1c, and 1d, Vnmin be the minimum value of the voltages generated by the detection resistors 1a, 1b, 1c, and 1d, and V0 be the median value of the voltages generated by the detection resistors 1a, 1b, 1c, and 1d, then the voltage regulation εv is expressed by the following equation (7): εv = (100 × (Vnmax - V0) / V0) - (100 × (Vnmin - V0) / V0) (7)

[0031] Furthermore, if Tnmax is the maximum value among the temperatures of detection resistors 1a, 1b, 1c, and 1d, Tnmin is the minimum value among the temperatures of detection resistors 1a, 1b, 1c, and 1d, and T0 is the median value among the temperatures of detection resistors 1a, 1b, 1c, and 1d, then the temperature fluctuation rate εt is expressed by the following equation (8): εt = (100 × (Tnmax - T0) / T0) - (100 × (Tnmin - T0) / T0) (8)

[0032] Figure 5 shows that in the range of magnification α from 0.5 to 2.0, the voltage fluctuation rate decreases as the magnification α increases, and in the range of magnification α greater than 2.0, the voltage fluctuation rate remains small and hardly changes. From this, it can be seen that increasing the magnification α reduces the voltage fluctuation rate of the voltage generated by the current flowing through each detection resistor 1a, 1b, 1c, and 1d.

[0033] The permissible range of voltage fluctuation in actual use to ensure current detection accuracy is within 0.5%, and as shown in Figure 5, this is satisfied only when the magnification α is 2.0 or greater. In other words, by arranging the detection resistors 1a, 1b, 1c, and 1d such that the first end resistance spacing W1 is less than or equal to half the resistance spacing Wr, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and the current can be detected with high accuracy.

[0034] This analysis uses the vertically symmetrical model shown in Figure 4 and analyzes only one side of the dashed line shown in Figure 4, either the upper or lower side. However, even when the first end resistance spacing W1 and the second end resistance spacing W2 have different widths, similar results can be obtained as long as both the first end resistance spacing W1 and the second end resistance spacing W2 are less than or equal to half the resistance spacing Wr. In other words, by arranging the detection resistors 1a, 1b, 1c, and 1d such that the first end resistance spacing W1 and the second end resistance spacing W2 are less than or equal to half the resistance spacing Wr, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and the current can be detected with high accuracy.

[0035] The analysis results shown in Figure 5 demonstrate that adjusting the placement of the detection resistors 1a, 1b, 1c, and 1d equalizes the current flowing through each of them. On the other hand, the resistance values ​​of the detection resistors 1a, 1b, 1c, and 1d are dependent on temperature. If R0 is the resistance value at 20 degrees, k is the temperature coefficient of resistance at 20 degrees, and t is the temperature of the detection resistors 1a, 1b, 1c, and 1d, then the resistance value R of the detection resistors 1a, 1b, 1c, and 1d is expressed by the following equation (9): R = R0 × {1 + k(t - 20)} (9) Therefore, if the temperature of the detection resistors 1a, 1b, 1c, and 1d varies, the resistance values ​​of the detection resistors 1a, 1b, 1c, and 1d will be affected by this temperature dependence. Therefore, when detecting current using detection resistors 1a, 1b, 1c, and 1d, in addition to equalizing the current flowing through each detection resistor 1a, 1b, 1c, and 1d, it is also necessary to suppress temperature variations in each detection resistor 1a, 1b, 1c, and 1d in order to detect the current with greater accuracy.

[0036] Figure 6 shows that in the range where the magnification α is between 0.5 and 1.5, the temperature fluctuation rate increases as the magnification α increases, while in the range where the magnification α is greater than 1.5, the temperature fluctuation rate hardly changes even if the magnification α is increased.

[0037] To ensure accurate current detection, the fluctuation in resistance values ​​during actual use must be within 1.0%. Here, the relationship between the resistance values ​​of the detection resistors 1a, 1b, 1c, and 1d and temperature is expressed by equation (9). Therefore, in order to keep the fluctuation in resistance values ​​within 1.0%, the temperature fluctuation rate must be within 5.0%. Accordingly, the allowable range of the temperature fluctuation rate during actual use to ensure accurate current detection is within 5.0%, and since the temperature fluctuation rate is 5.0% or less throughout the entire range of magnification α shown in Figure 6, the temperature fluctuation rate is within the allowable range when magnification α is 3.5 or less.

[0038] Since the analysis results for cases where the magnification α is greater than 3.5 are not shown in Figure 6, we will explain the case where the magnification α is greater than 3.5. As the input conductive pattern width Wp is expressed by equation (3), the larger the magnification α, the larger the input conductive pattern width Wp becomes. Therefore, when the magnification α is greater than 3.5, the input conductive pattern width Wp becomes even larger, which restricts the placement and wiring of other components other than the input conductive pattern 10 on the circuit board, thus reducing the design freedom. Consequently, it is not appropriate to set the magnification α to a value greater than 3.5 because it reduces the design freedom on the circuit board.

[0039] Based on these considerations, the range in which the magnification α is 3.5 or less satisfies the acceptable range of temperature fluctuation rate in actual use, while taking into account the design freedom on the circuit board. In other words, by arranging the detection resistors 1a, 1b, 1c, and 1d such that the resistance spacing Wr is 2.0 to 3.5 times the resistance spacing W1 at the first end, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and temperature variations in each detection resistor 1a, 1b, 1c, and 1d are suppressed, allowing for accurate current detection.

[0040] This analysis uses the vertically symmetrical analysis model shown in Figure 4, and the analysis is performed only on either the upper or lower side of the dashed line shown in Figure 4. However, even when the resistance spacing W1 at the first end and the resistance spacing W2 at the second end have different widths, similar results can be obtained if the resistance spacing Wr is between 2.0 and 3.5 times the resistance spacing W1 and W2 at the second end, respectively. In other words, by arranging the detection resistors 1a, 1b, 1c, and 1d such that the resistance spacing Wr is between 2.0 and 3.5 times the resistance spacing W1 at the first end, and between 2.0 and 3.5 times the resistance spacing W2 at the second end, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and temperature variations in each detection resistor 1a, 1b, 1c, and 1d are suppressed, allowing for accurate current detection.

[0041] Based on these findings, by adjusting the placement positions of the multiple detection resistors 1a, 1b, 1c, and 1d relative to the first side 12 of the input conductive pattern 10, the current flowing through each detection resistor 1a, 1b, 1c, and 1d can be equalized, thereby improving the accuracy of current detection.

[0042] The current detection circuit board according to the above-described embodiment is a rectangular conductive pattern having a second side 22, a third end 23, and a fourth end 24, as shown in Figure 1, but is not limited to this. As long as the condition is met that the detection resistors 1a, 1b, 1c, and 1d are arranged such that the resistance spacing W1 at the first end and the resistance spacing W2 at the second end are less than or equal to half the resistance spacing Wr with respect to the first side 12 of the input conductive pattern 10, the current flowing through each detection resistor 1a, 1b, 1c, and 1d can be equalized regardless of the shape of the output conductive pattern 20, thereby improving the accuracy of current detection.

[0043] Furthermore, by setting conditions not only for the placement of the detection resistors 1a, 1b, 1c, and 1d relative to the input conductive pattern 10, but also for the placement of the detection resistors 1a, 1b, 1c, and 1d relative to the output conductive pattern 20, variations in the current flowing through each detection resistor 1a, 1b, 1c, and 1d can be further suppressed, thereby improving the accuracy of current detection.

[0044] Using the comparative example shown in FIG. 2, the relationship between the arrangement positions of the detection resistors 1a, 1b, 1c, 1d with respect to the second side 22 of the output conductive pattern 20 and the variation in the current flowing through each detection resistor 1a, 1b, 1c, 1d will be described. Here, the distance between the detection resistor 1a closest to the third end portion 23 of the output conductive pattern 20 and the third end portion 23 is defined as the third end portion resistance interval W3, and the distance between the detection resistor 1d closest to the fourth end portion 24 of the output conductive pattern 20 and the fourth end portion 24 is defined as the fourth end portion resistance interval W4.

[0045] In FIG. 2, the detection resistors 1a, 1b, 1c, 1d are arranged at equal intervals so as to be closer to the vicinity of the center of the first side 12. The third end portion resistance interval W3 is larger than the resistance interval Wr, and the width of the current outflow area from which current flows out from the detection resistor 1a closest to the third end portion 23 is larger compared to the detection resistors 1b, 1c. Generally, the wider the width through which current flows, the smaller the resistance. Therefore, the resistance of the portion where the current flowing out from the detection resistor 1a flows is smaller than that of the detection resistors 1b, 1c. Since current flows more easily through a portion with a smaller resistance and more current flows through the portion with a smaller resistance, more current flows through the detection resistor 1a where the resistance of the portion where the outflowing current flows is smaller compared to the detection resistors 1b, 1c. Similarly, when the width of the current outflow area from which current flows out from the detection resistor 1d closest to the fourth end portion 24 is larger compared to the width of the current outflow area from which the current flowing out from each of the detection resistors 1b, 1c flows, more current flows through the detection resistor 1d.

[0046] Thus, due to the different widths of the current outflow areas for each of the plurality of detection resistors 1a, 1b, 1c, 1d, variations occur in the current flowing through each detection resistor 1a, 1b, 1c, 1d. Therefore, similar to the conditions regarding the arrangement positions of the detection resistors 1a, 1b, 1c, 1d with respect to the input conductive pattern 10, by making the widths of the current outflow areas for each of the plurality of detection resistors 1a, 1b, 1c, 1d uniform, the variations in the current flowing through each detection resistor 1a, 1b, 1c, 1d can be suppressed.

[0047] Therefore, in order to adjust the width of the current inflow area for the detection resistors 1a, 1b, 1c, 1d, it is the same phenomenon as adjusting the arrangement positions of the detection resistors 1a, 1b, 1c, 1d with respect to the first side 12 of the input conductive pattern 10, and in order to adjust the width of the current outflow area for the detection resistors 1a, 1b, 1c, 1d, adjusting the arrangement positions of the detection resistors 1a, 1b, 1c, 1d with respect to the second side 22 of the output conductive pattern 20. Thus, in the analysis shown in FIGS. 4 to 6 described above, the analysis results regarding the arrangement positions of the detection resistors 1a, 1b, 1c, 1d with respect to the first side 12 of the input conductive pattern 10 were calculated. However, it is considered that the same analysis results can be obtained even when the analysis is performed regarding the arrangement positions of the detection resistors 1a, 1b, 1c, 1d with respect to the second side 22 of the output conductive pattern 20.

[0048] Therefore, by arranging the detection resistors 1a, 1b, 1c, 1d so that the third end resistance interval W3 and the fourth end resistance interval W4 are less than or equal to one-half of the resistance interval Wr, the current flowing through each of the detection resistors 1a, 1b, 1c, 1d is equalized, and the current can be detected accurately. Further, by arranging the detection resistors 1a, 1b, 1c, 1d so that the resistance interval Wr is 2.0 times or more and 3.5 times or less the third end resistance interval W3, and the resistance interval Wr is 2.0 times or more and 3.5 times or less the fourth end resistance interval W4, after the current flowing through each of the detection resistors 1a, 1b, 1c, 1d is equalized, the variation in the temperature of each of the detection resistors 1a, 1b, 1c, 1d is suppressed, and the current can be detected accurately.

[0049] Thus, in addition to adjusting the arrangement positions of the plurality of detection resistors 1a, 1b, 1c, 1d with respect to the first side 12 of the input conductive pattern 10, by adjusting the arrangement positions of the plurality of detection resistors 1a, 1b, 1c, 1d with respect to the second side 22 of the output conductive pattern 20, the current flowing through each of the detection resistors 1a, 1b, 1c, 1d is further equalized, and the detection accuracy of the current can be further improved.

[0050] The current detection circuit board described above is installed, for example, in a power conversion device such as a compressor inverter. By inserting multiple detection resistors 1a, 1b, 1c, 1d, an input conductive pattern 10, and an output conductive pattern 20 into the current path flowing through the power conversion device, the current to be detected is divided by the multiple detection resistors 1a, 1b, 1c, 1d connected in parallel, reducing the heat generated in each detection resistor 1a, 1b, 1c, 1d. Furthermore, the current flowing through each detection resistor 1a, 1b, 1c, 1d is equalized, improving the accuracy of current detection and enabling high-precision control of the power conversion device.

[0051] Figure 7 shows a specific example in which a current detection circuit board is provided within a compressor inverter. Here, the multiple detection resistors 1a, 1b, 1c, 1d, input conductive pattern 10, and output conductive pattern 20 provided on the current detection circuit board are collectively referred to as the detection resistor section 110. As shown in Figure 7, the compressor inverter is a circuit provided on an insulating substrate 100, connecting a power supply 111 and a compressor 112, and includes a converter circuit 113, an inverter circuit 114, and a control unit 115. In such a compressor inverter, for example, as shown in Figure 7, the detection resistor section 110 is inserted in the current path connecting the converter circuit 113 and the inverter circuit 114. Here, the compressor inverter and the detection resistor section 110 are provided on the same insulating substrate 100.

[0052] By using this current detection circuit board, the current in the current path within the compressor inverter can be detected with high accuracy, and the control unit 115 can accurately control the compressor inverter based on this detection result. Note that the location of the detection resistor 110 within the compressor inverter is not limited to the location shown in Figure 7, but can be anywhere on the electrical path through which the current to be detected flows.

[0053] As described above, in the current detection circuit board according to Embodiment 1, a plurality of detection resistors 1a, 1b, 1c, and 1d connected to the first side 12 of the input conductive pattern 10 are arranged at equal intervals along the first side 12, and the detection resistors 1a, 1b, 1c, and 1d are arranged such that the first end resistance interval W1 and the second end resistance interval W2 are less than or equal to half the resistance interval Wr. With this configuration, the width of the input conductive pattern 10 is restricted by making the first end resistance interval W1 and the second end resistance interval W2 shorter than the resistance interval Wr, so that the width of the input conductive pattern 10 on the insulating substrate 100 is not widened, and it is prevented that more current flows into the detection resistor 1a closest to the first end 13 and the detection resistor 1d closest to the second end 14 of the first side 12 of the input conductive pattern 10 than into the other detection resistors 1b and 1c. As a result, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and the current can be detected with high accuracy.

[0054] Furthermore, in Embodiment 1, the detection resistors 1a, 1b, 1c, and 1d are arranged such that the resistance spacing Wr is 3.5 times or less the resistance spacing W1 at the first end, and the resistance spacing Wr is 3.5 times or less the resistance spacing W2 at the second end. With this configuration, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and temperature variations in each detection resistor 1a, 1b, 1c, and 1d are suppressed, thereby enabling more accurate current detection.

[0055] Furthermore, in Embodiment 1, in addition to adjusting the placement positions of the multiple detection resistors 1a, 1b, 1c, and 1d with respect to the first side 12 of the input conductive pattern 10, the placement positions of the multiple detection resistors 1a, 1b, 1c, and 1d with respect to the second side 22 of the output conductive pattern 20 are also adjusted. With this configuration, the width of the current outflow area for each of the multiple detection resistors 1a, 1b, 1c, and 1d is made equal, so that the resistance of each part through which current flows out of the detection resistors 1a, 1b, 1c, and 1d becomes approximately the same. As a result, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is further equalized, and the accuracy of current detection can be further improved.

[0056] Embodiment 2. The current detection circuit board according to Embodiment 2 will be described with reference to Figures 8 to 19. In Embodiment 2, the same reference numerals are used for the same components as in Embodiment 1, and the differences from Embodiment 1 will be mainly described.

[0057] Figure 8 shows an example of the configuration of a current detection circuit board according to Embodiment 2. The current detection circuit board shown in Figure 8 includes a first region 15 and a second region 25 in addition to the current detection circuit board shown in Figure 1. In Figure 8, the first direction, which is the direction along the first side 12, is indicated by the arrow A1, the second direction, which is perpendicular to the first direction, is indicated by the arrow A2, and the third direction, which is perpendicular to the second side 22, is indicated by the arrow A3.

[0058] The first region 15 is a rectangular region having a first side 12 and extending in a second direction perpendicular to the first direction. The inside of the first region 15 is composed of a conductive pattern, and the current input section 11 is provided outside the first region 15 on the second direction side. Here, if the length of the first region 15 in the second direction is L1, the length L1 of the first region 15 is set to satisfy the following equation (10) using the number N of detection resistors 1a, 1b, 1c, 1d and the resistance interval Wr: L1 ≥ 3.67(N-1)Wr (10)

[0059] The presence of this first region 15 in the input conductive pattern 10 suppresses variations in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. Using Figures 9 to 12, we will explain how the presence of the first region 15 in the input conductive pattern 10 equalizes the current flowing through each detection resistor 1a, 1b, 1c, and 1d.

[0060] First, using Figures 9 and 10, we will explain the relationship between the distance L0 between the first side 12 and the current input section 11 and the variation in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. Figure 9 is a reference example and shows a comparative example where there is variation in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. In Figure 9, the distance L0 between the first side 12 and the current input section 11 is small, and the distances from the current input section 11 to each detection resistor 1a, 1b, 1c, and 1d are all significantly different. In Figure 9, the distances from the current input section 11 to each detection resistor 1a, 1b, 1c, and 1d are indicated by dashed arrows. The impedance of each current path is determined by the distance from the current input section 11 to each detection resistor 1a, 1b, 1c, and 1d, and the longer the distance from the current input section 11, the greater the impedance and the more difficult it is for current to flow. Therefore, as shown in Figure 9, if the distances from the current input unit 11 to each of the detection resistors 1a, 1b, 1c, and 1d are significantly different, more current will flow through the detection resistors 1b and 1c, which are closer to the current input unit 11, than through the detection resistors 1a and 1d, resulting in greater variation in the current flowing through each of the detection resistors 1a, 1b, 1c, and 1d.

[0061] Thus, when the distance L0 between the first side 12 and the current input section 11 is small, the distances from the current input section 11 to the multiple detection resistors 1a, 1b, 1c, and 1d are all different, resulting in variations in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. Therefore, one way to suppress variations in the current flowing through each detection resistor 1a, 1b, 1c, and 1d is to widen the distance L0 between the first side 12 and the current input section 11.

[0062] Figure 10 shows an example configuration in which variations in the current flowing through each detection resistor 1a, 1b, 1c, and 1d are suppressed. In Figure 10, the distance L0 between the first side 12 and the current input section 11 is assumed to be larger than the distance L0 shown in Figure 9. In Figure 10, the distance from the current input section 11 to each detection resistor 1a, 1b, 1c, and 1d is indicated by a dashed arrow. In this case, compared to the comparative example shown in Figure 9, the distances from the current input section 11 to each detection resistor 1a, 1b, 1c, and 1d are all close, so the impedance of the current path connecting the current input section 11 to the detection resistors 1a, 1b, 1c, and 1d is close. Therefore, the current flowing through each detection resistor 1a, 1b, 1c, and 1d will be approximately the same, and the current flowing through each detection resistor 1a, 1b, 1c, and 1d will be equalized.

[0063] Next, we will explain the analysis and results regarding the relationship between the distance L0 between the first side 12 and the current input section 11 and the variation in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. The analysis model used for the analysis is shown in Figure 11, and the analysis results are shown in Figure 12.

[0064] Using the analysis model shown in Figure 4, the voltage generated at each detection resistor 1a, 1b, 1c, and 1d was calculated when the current input from the current input unit 11 flows through the input conductive pattern 10, detection resistors 1a, 1b, 1c, and 1d, and the output conductive pattern 20, and the current is output from the current output unit 21, by changing the distance L0 between the first side 12 and the current input unit 11. Here, the number of detection resistors 1a, 1b, 1c, and 1d N was set to 4, the distance between the first end resistors W1 and the distance between the second end resistors W2 was set to 1.82 mm, and the distance between the resistors Wr was set to 5.46 mm, which is three times the distance between the first end resistors W1 and the distance between the second end resistors W2. The results of calculating the voltage fluctuation rate, which shows the variation in the voltage generated at each detection resistor 1a, 1b, 1c, and 1d, are shown in Figure 12.

[0065] Figure 12 shows that, in the range where the interval L0 is less than 60 mm, the voltage fluctuation rate generally decreases as the interval L0 increases. Furthermore, in the range where the interval L0 is 60 mm or more, the voltage fluctuation rate tends to remain small and hardly change. From this, it can be seen that increasing the interval L0 reduces the voltage fluctuation rate of the voltage generated at each detection resistor 1a, 1b, 1c, and 1d, thereby suppressing the variation in the current flowing through them.

[0066] To ensure the accuracy of current detection, the permissible range of voltage fluctuation in actual use is within 0.5%, which is satisfied when the spacing L0 is 60 mm or more. In other words, by arranging the current input section 11 so that the spacing L0 is 60 mm or more, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and the current can be detected with high accuracy.

[0067] The range of intervals L0 in which the current flowing through each detection resistor 1a, 1b, 1c, and 1d can be equalized depends on the length of the first side 12, which is the width of the input conductive pattern 10 in the first direction, and the placement positions of the detection resistors 1a, 1b, 1c, and 1d. Therefore, the interval L0 is expressed using at least one of the following values: the resistance interval Wr related to the placement positions of the detection resistors 1a, 1b, 1c, and 1d on the first side 12, the first end resistance interval W1, and the second end resistance interval W2. In the analysis model shown in Figure 11, the sum of the resistance intervals Wr provided between each detection resistor 1a, 1b, 1c, and 1d is 16.38 mm. The minimum value of the range of intervals L0 in which the current can be equalized, which is 60 mm, is approximately 3.663 times the sum of the resistance intervals Wr provided between each detection resistor 1a, 1b, 1c, and 1d, which is 16.38 mm. Even if the vertical and horizontal dimensions of the conductive pattern change proportionally, the distribution of current flowing through the conductive pattern is considered to remain unchanged. Therefore, if the interval L0 is 3.67 times or more the sum of the resistance intervals Wr provided between each detection resistor 1a, 1b, 1c, 1d, then the voltage fluctuation rate of the voltage generated across each detection resistor 1a, 1b, 1c, 1d will be within 0.5%, and the current flowing through each detection resistor 1a, 1b, 1c, 1d can be equalized. Accordingly, the interval L0 at which the current flowing through each detection resistor 1a, 1b, 1c, 1d can be equalized is expressed by the following equation (11), using the number of detection resistors 1a, 1b, 1c, 1d N and the resistance interval Wr: L0 ≥ 3.67(N-1)Wr (11)

[0068] Therefore, by setting the distance L0 between the first side 12 and the current input section 11 to be within the range shown in equation (11), the impedance of the current path connecting the current input section 11 to the detection resistors 1a, 1b, 1c, and 1d will be approximately the same, the current flowing through each detection resistor 1a, 1b, 1c, and 1d will be equalized, and the accuracy of current detection can be improved.

[0069] Furthermore, since the current input section 11 is provided on the second direction side outside the first region 15, by setting the length L1 of the first region 15 to be within the range shown in equation (10) in order to set the distance L0 between the first side 12 and the current input section 11 to be within the range shown in equation (11), the current flowing through each detection resistor 1a, 1b, 1c, 1d is equalized, and the accuracy of current detection can be improved. In other words, the input conductive pattern 10 has a first region 15 and a current input section 11 provided on the second direction side outside the first region 15, and by setting the length L1 of the first region 15 to be within the range shown in equation (10), the current flowing through each detection resistor 1a, 1b, 1c, 1d is equalized, and the accuracy of current detection can be improved.

[0070] In the input conductive pattern 10, the shape of the area outside the first region 15 is not limited to any shape, as long as the current input section 11 is provided outside the first region 15 on the second direction side and the conductive pattern within the first region 15 is ensured. Similarly, the shape of the output conductive pattern 20 is not limited to any shape, as long as the current input section 11 is provided outside the first region 15 of the input conductive pattern 10 and the conductive pattern within the first region 15 is ensured.

[0071] Figures 13 to 15 show examples of the configuration of a current detection circuit board in which circuit component placement areas 16a, 16b, 16c, 26a, 26b, and 26c are formed in at least one of the second direction side outside the first region 15 of the input conductive pattern 10 and the output conductive pattern 20, where conductive patterns are missing. The circuit component placement areas 16a, 16b, 16c, 26a, 26b, and 26c are areas where conductive patterns are missing, and the current to be detected, which is input from the current input unit 11 and output from the current output unit 21, does not flow through these areas, allowing for the placement of circuit components such as wiring necessary for other devices or circuits other than the current detection circuit board.

[0072] Figure 13 shows an example configuration in which rectangular circuit component placement areas 16a and 26a are provided on at least one of the input conductive pattern 10 and the output conductive pattern 20, leaving each side of the input conductive pattern 10 and the output conductive pattern 20 intact. Figure 14 shows an example configuration in which rectangular circuit component placement areas 16b and 26b are provided on at least one of the input conductive pattern 10 and the output conductive pattern 20, cutting off the corners of the input conductive pattern 10 and the output conductive pattern 20. Figure 15 shows an example configuration in which triangular circuit component placement areas 16c and 26c are provided on at least one of the input conductive pattern 10 and the output conductive pattern 20, cutting off the corners of the input conductive pattern 10 and the output conductive pattern 20.

[0073] As shown in Figures 13(a), 14(a), and 15(a), the circuit component placement areas 16a, 16b, 16c, 26a, 26b, and 26c may be provided on both the input conductive pattern 10 and the output conductive pattern 20. As shown in Figures 13(b), 14(b), and 15(b), the circuit component placement areas 16a, 16b, and 16c may be provided only on the input conductive pattern 10. As shown in Figures 13(c), 14(c), and 15(c), the circuit component placement areas 26a, 26b, and 26c may be provided only on the output conductive pattern 20.

[0074] In this way, by forming circuit component placement areas 16a, 16b, and 16c outside the first region 15 of the input conductive pattern 10 on the second direction side, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and other necessary circuit components such as wiring for other devices or circuits can be placed in the circuit component placement areas 16a, 16b, and 16c. As a result, the degree of design freedom for other structures on the insulating substrate 100 or within the device on which the current detection circuit board is provided can be improved.

[0075] As described above, the input conductive pattern 10 has a first region 15, and the current input section 11 is provided outside the first region 15 on the second direction side, thereby equalizing the current flowing through each detection resistor 1a, 1b, 1c, and 1d. In addition, the output conductive pattern 20 has a second region 25, and the current output section 21 is provided outside the second region 25 on the third direction side, thereby further suppressing variations in the current flowing through each detection resistor 1a, 1b, 1c, and 1d, and further improving the accuracy of current detection.

[0076] As shown in Figure 8, the second region 25 is a rectangular region having a second side 22 and extending in a third direction perpendicular to the second side 22. The inside of the second region 25 is composed of a conductive pattern, and the current output section 21 is provided outside the second region 25 on the third direction side. Here, if the length of the second region 25 in the third direction is L2, the length L2 of the second region 25 is set to satisfy the following equation (12) using the number N of detection resistors 1a, 1b, 1c, 1d and the resistance interval Wr: L2 ≥ 3.67(N-1)Wr (12)

[0077] Here, using Figure 16, we will explain the relationship between the distance L0' between the second side 22 and the current output unit 21 and the variation in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. Figure 16 is a reference example and shows a comparative example where there is variation in the current flowing through each detection resistor 1a, 1b, 1c, and 1d. In Figure 16, the distance L0' between the second side 22 and the current output unit 21 is small, and the distances from each detection resistor 1a, 1b, 1c, and 1d to the current output unit 21 are all significantly different. In Figure 16, the distances from each detection resistor 1a, 1b, 1c, and 1d to the current output unit 21 are indicated by dashed arrows. In this case, the impedance of the current path from detection resistors 1b and 1c to the current output unit 21 is lower than that of the current path from detection resistors 1a and 1d to the current output unit 21. As a result, more current flows through detection resistors 1b and 1c, which have lower impedance in their current paths than detection resistors 1a and 1d, leading to greater variation in the current flowing through each detection resistor 1a, 1b, 1c, and 1d.

[0078] Thus, when the distance L0' between the second side 22 and the current output section 21 is small, the distance from each of the multiple detection resistors 1a, 1b, 1c, 1d to the current output section 21 is different, resulting in variations in the current flowing through each detection resistor 1a, 1b, 1c, 1d. Therefore, it can be seen that the variation in current flowing through each detection resistor 1a, 1b, 1c, 1d when the distance L0 between the first side 12 and the current input section 11 of the input conductive pattern 10 is small is a similar phenomenon to the variation in current flowing through each detection resistor 1a, 1b, 1c, 1d when the distance L0' between the second side 22 and the current output section 21 is small. For this reason, although the analysis results shown in Figures 11 and 12 above were calculated with respect to the distance L0 between the first side 12 of the input conductive pattern 10 and the current input section 11, it is thought that similar analysis results can be obtained when the analysis is performed with respect to the distance L0' between the second side 22 and the current output section 21 of the output conductive pattern 20.

[0079] Therefore, in order to further suppress variations in the current flowing through each detection resistor 1a, 1b, 1c, and 1d, the distance L0' between the second side 22 and the current output section 21 should be increased. In other words, the length L2 of the second region 25 should be set to be within the range shown in equation (12), similar to the range of length L1 of the first region 15 shown in equation (10).

[0080] Therefore, the input conductive pattern 10 has a first region 15, a current input section 11 is provided outside the first region 15 on the second direction side, and the length L1 of the first region 15 is set to be within the range shown in equation (10). Then, the output conductive pattern 20 has a second region 25, a current output section 21 is provided outside the second region 25 on the third direction side, and the length L2 of the second region 25 is set to be within the range shown in equation (12). As a result, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is further equalized, and the accuracy of current detection can be further improved.

[0081] Furthermore, as long as the current output section 21 is provided outside the second region 25 on the third direction side, it may be provided at any position within the output conductive pattern 20 in the direction along the second side. Also, in the output conductive pattern 20, as long as the current output section 21 is provided outside the second region 25 on the third direction side and the conductive pattern within the second region 25 is secured, the shape of the area outside the second region 25 may be any shape.

[0082] Figures 17 to 19 show an example configuration of a current detection circuit board in which circuit component placement areas 16a, 16b, 16c, 26d, 26e, and 26f are formed in at least one of the second direction side outside the first region 15 of the input conductive pattern 10 and the third direction side outside the second region 25 of the output conductive pattern 20, where conductive patterns are absent. The circuit component placement areas 16a, 16b, 16c, 26d, 26e, and 26f are areas where conductive patterns are absent, and since the current to be detected, which is input from the current input unit 11 and output from the current output unit 21, does not flow through these areas, they are areas where circuit components such as wiring necessary for other devices or circuits other than the current detection circuit board can be placed.

[0083] Note that the circuit component placement areas 16a, 16b, and 16c shown in Figures 17 to 19 are the same as the circuit component placement areas 16a, 16b, and 16c shown in Figures 13 to 15. Also, the circuit component placement areas 26d, 26e, and 26f shown in Figures 17 to 19 are areas located on the third direction side outside the second region 25 of the output conductive pattern 20, and the difference from the circuit component placement areas 26a, 26b, and 26c shown in Figures 13 to 15 is that the second region 25 is taken into consideration.

[0084] Figure 17 shows an example configuration in which rectangular circuit component placement areas 16a and 26d are provided on at least one of the input conductive pattern 10 and the output conductive pattern 20, leaving each side of the input conductive pattern 10 and the output conductive pattern 20 intact. Figure 14 shows an example configuration in which rectangular circuit component placement areas 16b and 26e are provided on at least one of the input conductive pattern 10 and the output conductive pattern 20, cutting off the corners of the input conductive pattern 10 and the output conductive pattern 20. Figure 15 shows an example configuration in which triangular circuit component placement areas 16c and 26f are provided on at least one of the input conductive pattern 10 and the output conductive pattern 20, cutting off the corners of the input conductive pattern 10 and the output conductive pattern 20.

[0085] As shown in Figures 13(a), 14(a), and 15(a), the circuit component placement areas 16a, 16b, 16c, 26d, 26e, and 26f may be provided on both the input conductive pattern 10 and the output conductive pattern 20. As shown in Figures 13(b), 14(b), and 15(b), the circuit component placement areas 16a, 16b, and 16c may be provided only on the input conductive pattern 10. As shown in Figures 13(c), 14(c), and 15(c), the circuit component placement areas 26d, 26e, and 26f may be provided only on the output conductive pattern 20.

[0086] In this way, circuit component placement areas 26d, 26e, and 26f are formed outside the second region 25 of the output conductive pattern 20 on the third direction side, thereby equalizing the current flowing through each detection resistor 1a, 1b, 1c, and 1d, and allowing other necessary circuit components such as wiring for other devices or circuits to be placed in the circuit component placement areas 26d, 26e, and 26f. As a result, the degree of design freedom for other structures on the insulating substrate 100 or within the device on which the current detection circuit board is provided can be improved.

[0087] As described above, the current detection circuit board according to Embodiment 2 has an input conductive pattern 10 that has a first region 15 of length L1 that satisfies the relationship shown in equation (10), and the current input section 11 is arranged outside the first region 15 on the second direction side. With this configuration, the impedance of each current path connecting the current input section 11 to each detection resistor 1a, 1b, 1c, and 1d becomes closer in value compared to the case where the length L1 of the first region 15 does not satisfy equation (10). As a result, the current flowing through each detection resistor 1a, 1b, 1c, and 1d becomes approximately the same, and the current flowing through each detection resistor 1a, 1b, 1c, and 1d is further equalized, allowing for more accurate current detection.

[0088] Furthermore, in the second embodiment, the output conductive pattern 20 has a second region 25 with a length L2 that satisfies the relationship shown in equation (12), and the current output unit 21 is arranged outside the second region 25 on the third direction side. With this configuration, the impedance of each current path connecting each detection resistor 1a, 1b, 1c, 1d to the current output unit 21 becomes closer in value compared to the case where the length L2 of the second region 25 does not satisfy equation (12). As a result, the current flowing through each detection resistor 1a, 1b, 1c, 1d becomes approximately the same, further equalizing the current flowing through each detection resistor 1a, 1b, 1c, 1d, and enabling more accurate current detection.

[0089] Furthermore, in Embodiment 2, circuit component placement areas 16a, 16b, 16c, 26a, 26b, 26c, 26d, 26e, and 26f are formed on at least one of the input conductive pattern 10 and the output conductive pattern 20. With this configuration, circuit components such as wiring necessary for other devices or circuits can be placed in the circuit component placement areas 16a, 16b, 16c, 26a, 26b, 26c, 26d, 26e, and 26f. As a result, the current flowing through each detection resistor 1a, 1b, 1c, and 1d is equalized, and the degree of design freedom for other structures on the insulating substrate 100 or within the device on which the current detection circuit board is provided can be improved.

[0090] Embodiment 3. The current detection circuit board according to Embodiment 3 will be described with reference to Figures 20 and 21. In Embodiment 3, the same reference numerals are used for components that are the same as those in Embodiments 1 and 2, and the description will mainly focus on configurations that differ from Embodiments 1 and 2.

[0091] Figures 20 and 21 show an example configuration of a current detection circuit board according to Embodiment 3. The current detection circuit board shown in Figures 20 and 21 includes, in addition to the current detection circuit board shown in Figure 1, detection resistors 1e, 1f, 1g, an input conductive pattern 10a, and an output conductive pattern 20a. In this embodiment, a two-layer substrate is used as the insulating substrate 100, but the invention is not limited to this; any insulating substrate 100 having two or more surfaces on which wiring can be performed, such as a multilayer substrate, may be used.

[0092] The top view shown in Figure 20 is similar to the current detection circuit board shown in Figure 1, and the detection resistors 1a, 1b, 1c, and 1d are arranged such that the resistance spacing W1 at the first end and the resistance spacing W2 at the second end are less than or equal to half of the resistance spacing Wr. The current detection circuit board shown in the top view of Figure 20 is shown as a side view from direction B shown in Figure 20. As shown in the side view of Figure 20, the current detection circuit board according to Embodiment 3 has the current detection circuit board shown in Figure 1 mounted on one side of the insulating substrate 100, and the current detection circuit board is also mounted on the other side of the insulating substrate 100.

[0093] The side view shown in Figure 21 is the same as the side view shown in Figure 20. The side of the insulating substrate 100 visible from direction C in the side view of Figure 21 is considered the bottom surface, and the opposite side is considered the top surface. The current detection circuit board shown in the side view of Figure 21 is shown as a bottom view when viewed from direction C in Figure 21. The current detection circuit board shown in the side view of Figure 21 has the current detection circuit board shown in Figure 1 mounted on the top surface of the insulating substrate 100, and detection resistors 1e, 1f, 1g, input conductive pattern 10a, and output conductive pattern 20a mounted on the bottom surface of the insulating substrate 100. In this embodiment, three detection resistors are mounted on the bottom surface of the insulating substrate 100, but this is not limited to this, and it is sufficient to have one or more detection resistors mounted on the bottom surface of the insulating substrate 100.

[0094] Using the bottom view shown in Figure 21, the detection resistors 1e, 1f, 1g, input conductive pattern 10a, and output conductive pattern 20a mounted on the bottom surface of the insulating substrate 100 will be described. The input conductive pattern 10a is located on the bottom surface of the insulating substrate 100 and is electrically connected to the input conductive pattern 10 located on the bottom surface of the insulating substrate 100 at the input connection section 31. One end of the detection resistors 1e, 1f, 1g is connected to the input conductive pattern 10a, and the current to be detected, input from the input connection section 31, flows through the input conductive pattern 10a and is input to the detection resistors 1e, 1f, 1g.

[0095] The output conductive pattern 20a is positioned on the lower surface of the insulating substrate 100 and is electrically connected to the output conductive pattern 20 positioned on the lower surface of the insulating substrate 100 at the output connection section 32. The other ends of the detection resistors 1e, 1f, and 1g connected to the input conductive pattern 10a are connected to the output conductive pattern 20a, and the current of the object to be detected that flows through the detection resistors 1e, 1f, and 1g flows through the output conductive pattern 20a and is output from the output connection section 32.

[0096] The detection resistors 1e, 1f, and 1g are placed on the lower surface of the insulating substrate 100 and connected to the input conductive pattern 10a and the output conductive pattern 20a. They are current detection resistors through which the current to be detected flows. In this way, the detection resistors can be placed on both sides of the insulating substrate 100. Therefore, the detection resistors 1a, 1b, 1c, and 1d can be placed on the upper surface of the insulating substrate 100, and the detection resistors 1e, 1f, and 1g can be placed on the lower surface of the insulating substrate 100. In this case, compared to the case where all of the detection resistors 1a, 1b, 1c, 1d, 1e, 1f, and 1g are connected to the first side 12 of the input conductive pattern 10a provided on the upper surface of the insulating substrate 100, the number of detection resistors provided on the upper surface of the insulating substrate 100 is reduced, and the resistance spacing Wr can be widened. As a result, the heat generated by each detection resistor 1a, 1b, 1c, 1d, 1e, 1f, and 1g can be sufficiently dissipated. As a result, excessive temperature rise in the detection resistors 1a, 1b, 1c, 1d, 1e, 1f, and 1g is prevented, and the current can be detected with high accuracy.

[0097] As described above, the current detection circuit board according to Embodiment 3 has the current detection circuit board provided on one surface of the insulating substrate 100, and other detection resistors 1e, 1f, 1g, other input conductive patterns 10a, and other output conductive patterns 20a provided on the other surface of the insulating substrate 100. With this configuration, the detection resistors 1a, 1b, 1c, 1d, 1e, 1f, 1g can be arranged on two surfaces of the insulating substrate 100, thereby equalizing the current flowing through each detection resistor 1a, 1b, 1c, 1d, 1e, 1f, 1g, preventing excessive temperature rise of the detection resistors 1a, 1b, 1c, 1d, 1e, 1f, 1g, and enabling more accurate detection of the current.

[0098] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are envisioned within the scope of the art disclosed in this specification. For example, these include modifying, adding or omitting at least one component, or extracting at least one component and combining it with a component from another embodiment.

[0099] 1a, 1b, 1c, 1d, 1e, 1f, 1g Detecting resistors, 10, 10a Input conductive patterns, 11 Current input section, 12 First side, 13 First end, 14 Second end, 15 First region, 16a, 16b, 16c Circuit component placement areas, 20, 20a Output conductive patterns, 21 Current output section, 22 Second side, 23 Third end, 24 Fourth end, 25 Second region, 26a, 26b, 26c, 26d, 26e, 26f Circuit component placement areas, 31 Input connection section, 32 Output connection section, 100 Insulating substrate, 110 Detecting resistor section, 111 Power supply, 112 Compressor, 113 Converter circuit, 114 Inverter circuit, 115 Control unit, W1 First end resistance spacing, W2 Second end resistance spacing, W3 Third end resistance spacing, W4 Fourth end resistance gap, Wr resistance gap

Claims

Insulating substrate and A plurality of detection resistors arranged on one surface of the insulating substrate, An input conductive pattern is provided, which is arranged on the aforementioned surface and has a rectangular shape with a first side to which one end of a plurality of the detection resistors is connected, and a first end and a second end which are the ends of the first side, and the current to be detected is input to the detection resistor via a current input section, The system includes an output conductive pattern arranged on one surface, to which the other ends of a plurality of detection resistors connected to the first side are connected, and to which the current flowing through the detection resistors is output via a current output unit, The detection resistors are arranged at equal intervals in a first direction along the first side, and the first end resistance interval, which is the distance between the detection resistor closest to the first end and the first end, and the second end resistance interval, which is the distance between the detection resistor closest to the second end and the second end, are arranged such that the resistance interval, which is the distance between adjacent detection resistors, is 1 / 2 or less. 　 The current detection circuit board according to claim 1, wherein the detection resistors are arranged such that the resistor spacing is 3.5 times or less the resistor spacing at the first end and 3.5 times or less the resistor spacing at the second end. 　 The input conductive pattern has a first region having the first side and extending in a second direction perpendicular to the first direction, and a current input portion provided outside the first region on the side of the second direction. If L1 is the length of the first region in the second direction, N is the number of detection resistors, and Wr is the resistor spacing, L1≧3.67(N-1)Wr The current detection circuit board according to claim 1 or 2, characterized in that the length of the first region is set such that the following relationship holds. 　 The current detection circuit board according to claim 3, wherein the input conductive pattern has a circuit component placement area formed outside the first region in the second direction where the conductive pattern is missing. 　 The output conductive pattern is rectangular in shape, having a second side to which the other end of the detection resistor is connected, and a third end and a fourth end which are the ends of the second side. The current detection circuit board according to any one of claims 1 to 4, wherein the detection resistors are arranged such that the third end resistance interval, which is the distance between the detection resistor closest to the third end and the third end, and the fourth end resistance interval, which is the distance between the detection resistor closest to the fourth end and the fourth end, are less than or equal to half of the total resistance interval. 　 The current detection circuit board according to claim 5, wherein the detection resistors are arranged such that the resistor spacing is 3.5 times or less the resistor spacing at the third end and 3.5 times or less the resistor spacing at the fourth end. 　 The output conductive pattern has a second region having the second side and extending in a third direction perpendicular to the second side, and a current output section provided outside the second region on the third direction side. If the length of the second region in the third direction is L2, the number of detection resistors is N, and the resistor spacing is Wr, L2≧3.67(N-1)Wr The current detection circuit board according to claim 5 or 6, characterized in that the length of the second region is set such that the following relationship holds. 　 The current detection circuit board according to claim 7, wherein the output conductive pattern has a circuit component placement area formed outside the second region on the third direction side where the conductive pattern is missing. 　 Another detection resistor disposed on the other side of the insulating substrate, Displaced on the other surface, electrically connected to the input conductive pattern, and connected to another input conductive pattern to which one end of the other detection resistor is connected, A current detection circuit board according to any one of claims 1 to 8, comprising another output conductive pattern arranged on the other surface, electrically connected to the output conductive pattern, and to which the other end of the other detection resistor connected to the other input conductive pattern is connected.

Images