Power semiconductor module having interference-insensitive measurement

Abstract

The invention relates to a power semiconductor module having a power current path (17) in which a shunt resistor (1), in particular a resistor less than or equal to 50 milliohms, is arranged, the shunt resistor (1) having two mutually spaced main measuring contacts (2, 3) of different polarities (+,-) and an auxiliary measuring contact (4) being arranged immediately adjacent to the shunt resistor (1), the auxiliary measuring contacts are not directly electrically connected to the shunt resistor, and wherein a measuring line (20, 21, 22) leads from each measuring contact (2, 3, 4) to the evaluation unit (6) and forms a loop (18, 19) having an approximately identical area.

Description

Technical Field

[0001] This invention relates to a power semiconductor module with interference-insensitive measurement function for shunt voltage of a power semiconductor module, and a method for measuring interference-insensitive shunt voltage in a power semiconductor module. Background Technology

[0002] Due to the increasing power density requirements of power electronic devices, current measurement in converters is achieved using compact shunt resistors integrated into power semiconductor modules.

[0003] Here, the shunt resistor is fixed very close to the power semiconductor within the power semiconductor module. This proximity causes interference coupling to the measurement circuitry leading to the shunt resistor, which in turn leads to measurement errors.

[0004] One known and effective solution for interference-coupled inputs is stranded wire. This solution can only be implemented manually in the manufacture of power semiconductor modules. Automating this solution is very complex and expensive. Furthermore, parallel wiring arrangements are still present at the pins of the power module. Despite the use of stranded wire, this area continues to act as a window for interference-coupled inputs.

[0005] Another solution to reduce this interference coupling input is to increase the useful signal. However, in a shunt resistor, this results in an increase in resistance. Consequently, the ratio of interference to the measured signal decreases.

[0006] The known and commonly used analog-to-digital converters to date have a measurement range of 50mV or 200mV. Shunt designs for a 50mV measurement range result in relatively high interference coupling input due to their low voltage drop.

[0007] However, the shift to a higher measurement range, particularly 200mV, means a doubling, and especially a quadrupling, of the shunt's ohmic resistance. Consequently, power losses also increase, specifically quadrupling. To mitigate these losses, parallel connection of the shunt resistors is necessary. However, this increases the cost and space requirements of the power semiconductor module. Summary of the Invention

[0008] Therefore, the basic objective of this invention is to provide a compact power semiconductor module with interference-insensitive measurement capabilities.

[0009] The objective is successfully achieved through the features of the independent claims.

[0010] Advantageous design solutions can be provided by the dependent claims.

[0011] Therefore, according to the present invention, interference-insensitive current measurement is achieved in a power semiconductor module having a power current path in which a shunt resistor, particularly a resistor less than or equal to 50 milliohms, is arranged. Here, there are two main measurement contacts spaced apart from each other with different polarities (+, -), and an auxiliary measurement contact is arranged adjacent to the shunt resistor, wherein the auxiliary measurement contact is not directly electrically connected to the shunt resistor. With this arrangement, interference-insensitive current measurement can be achieved at the shunt resistor in such a way that the measurement line is guided from each measurement contact, i.e., the main measurement contact and the auxiliary measurement contact, to the evaluation unit, simultaneously forming a loop of almost equal area.

[0012] Here, a power semiconductor is a semiconductor device designed in power electronic devices to control and switch large currents and voltages (greater than 1 ampere and greater than about 24 volts). The upper limits for these parameters are in the thousands of amperes and volts, respectively.

[0013] Therefore, modified variations of standard semiconductor components are used because large currents and voltages would damage conventional components. The following components are preferred: A power diode (is a switching element that, in principle, allows current to flow in only one direction or only when a certain voltage value is exceeded). thyristor A GTO (Gateway Turn-Off Thyristor) or SCR (Silicon Controlled Rectifier) ​​is a switching element that allows the switching point to be set arbitrarily and flexibly by a controllable voltage at the control electrode. A triac (a three-terminal bidirectional thyristor) is two thyristor elements in a single device, connected in reverse parallel and controlled together. Power MOSFETs and IGBTs are transistors that have special switching and power characteristics due to their atomic semiconductor structure.

[0014] Here, the power semiconductor is electrically connected to the power contacts of the corresponding power semiconductor module.

[0015] According to the present invention, the current-measuring resistor is referred to as a shunt resistor, which is a low-ohm electrical measuring resistor, typically equipped with separate current and voltage terminals. The current-measuring resistor is directly connected to the current-carrying cable, i.e., the power current path of the power semiconductor. By means of an evaluation unit connected in parallel with this shunt resistor, only a relatively small current is derived, and the voltage “dropped” across it is detected.

[0016] For large current intensities, such as greater than 10A, current measurement is performed by measuring the voltage at the shunt. To measure very large currents (>100A), the shunt resistor is mechanically robustly constructed, for example, consisting of a metal strip or rod with strong threaded contacts for the load circuit (consumption circuit) and two smaller measuring contacts for connecting, for example, measuring instruments. Large shunt resistors made of parallel metal rods can also be directly screwed between busbars. Materials used for such shunt resistors are, for example, manganin, isomeric, or manganese-based resistive materials, characterized by a low temperature coefficient of resistance and a relatively small thermal voltage relative to copper. Adequate heat dissipation is essential.

[0017] Shunts are typically designed for voltages of 50mV or 200mV at rated current intensity in the power path. The current intensity in a shunt is calculated according to Ohm's law.

[0018] A shunt resistor is inserted into the circuit through which the current is to be measured. The voltage drop across this resistor is measured. The contact resistance in the current terminals is typically greater than the measuring resistance, and its value is unknown.

[0019] Because current in power electronic devices and converters must also be measured with short rise times or high frequencies, shunt resistors, especially those with low parasitic inductance, are used. Here, axially wound or axially oriented resistors can be used only to a limited extent. More suitable for such shunt resistors are double-wound resistors or special structures, such as coaxial shunts, which consist of two interlocking tubes through which current flows in opposite directions. Other known low-inductance structures are Möbius resistors or corrugated foil resistors.

[0020] Shunt resistors are an inexpensive and accurate method of current measurement, and in principle, they are used not only in measuring instruments but also in power electronic equipment components for current monitoring and regulation.

[0021] This power semiconductor module is incorporated into a power converter. A power converter should be understood, for example, as a rectifier, inverter, AC converter, or DC-DC voltage converter.

[0022] According to the present invention, an auxiliary measuring contact is created directly at the shunt resistor, particularly by means of a bridging element, and the auxiliary measuring contact is at the same potential as the second measuring contact.

[0023] By alternating the arrangement of measurement signals (-+-, or alternatively: +-+), a feasible scheme for implementing interference-insensitive measurements of voltage drop is obtained.

[0024] Here, three measurement lines extend from the shunt resistor to the evaluation unit, forming loops of equal size. The measurement lines are particularly parallel and extend as close to each other as possible. By arranging the two main measurement contacts at different potentials and the auxiliary measurement contact at the potential of the second main measurement contact, i.e., the "+" or alternatively "-" contact, a loop of substantially equal area is formed between these three measurement lines. Interference fields are coupled into the measurement lines via this loop.

[0025] As described above, such interference-coupled inputs can be reduced to date, but not easily prevented.

[0026] Therefore, according to the present invention, interference coupling input is explicitly permitted first.

[0027] Interference coupling input (dB / dt) is preferably performed in the plane expanded by each loop. The interference signal induces an electric field (dE / dt) in the conductor loop formed by the measurement lines and causes interference voltages with different directions at the input of the evaluation unit.

[0028] In one operational amplifier of the evaluation unit, the interference amplifies the actual measured signal, while in another operational amplifier of the evaluation unit, the interference has the opposite effect on the measured signal.

[0029] By subsequently summing the two signals using analog methods, such as with the aid of a resistor circuit, the interference signal is eliminated before it enters the A / D (analog-to-digital) converter.

[0030] Due to the strong gradient of the interference field, interference voltages can be induced at different amplitudes in the two loops. This effect can be further avoided or at least significantly reduced by ensuring that the measurement lines are as closely parallel as possible.

[0031] Therefore, with the proposed solution, it is still possible to measure small voltage signals that are insensitive to interference with the shunt resistor. This allows for the use of relatively small resistors, particularly those less than or equal to 50 milliohms, for the 50mV measurement range of the A / D converter.

[0032] The advantages and preferred design schemes listed below regarding power semiconductors can be transferred accordingly to methods for interference-insensitive current measurements.

[0033] According to the invention, the following advantages are achieved: faster current measurement is possible at the power semiconductor module because the filter cutoff frequency of the anti-aliasing filter can be increased. Furthermore, the number of shunt resistors is reduced by using a voltage measurement range of 50mV. The compact structure for current measurement reduces the assembly area required for this purpose within the power semiconductor module. Power loss is reduced, particularly within the power semiconductor module, by the structure and method according to the invention. This structure can be advantageously manufactured automatically compared to structures to date. Attached Figure Description

[0034] The present invention and other advantageous embodiments thereof will be described in detail based on embodiments illustrated in principle, wherein: Figure 1 This shows the basic structure and arrangement of the shunt resistor. Figure 2 This demonstrates how the measurement method operates. Figure 3 The signal curve is shown.

[0035] For clarity, in the accompanying drawings, where components are present multiple times, reference numerals are not typically assigned to all shown components. Detailed Implementation

[0036] The described embodiments can be combined arbitrarily. Similarly, individual features of the corresponding embodiments can also be combined without departing from the spirit and scope of the invention.

[0037] Figure 1 A shunt resistor 1 is shown, which is arranged in the power current path of the power semiconductor. In addition to the two main measurement contacts, namely the first main measurement contact 2 and the second main measurement contact 3, an auxiliary measurement contact 4, i.e., the third connector, is formed directly at the shunt resistor 1 by means of a bridging element 5. The auxiliary measurement contact 4 is at the same potential as the second main measurement contact 3.

[0038] By alternating the arrangement of measurement signals (-+-, or alternatively: +-+), a feasible scheme is obtained to implement a measurement that is insensitive to interference of the voltage drop at shunt resistor 1.

[0039] According to the invention, three measuring lines 20, 21, and 22 extend parallel to each other and close to one another. By arranging them in a -+- (or alternatively +-+) configuration, loops 18 and 19 of the same size are formed (see also). Figure 2 Interference signal 7 is coupled into measurement lines 20, 21, and 22 via this loop.

[0040] according to Figure 2Interference coupling input (dB / dt) enters the plane. Interference signal 7 induces an electric field 8 (dE / dt) in loops 18 and 19 and causes interference signal 14, particularly interference voltage, at the input of evaluation unit 6. The evaluation unit is preferably located directly at pin 15 of the housing 16 of the power semiconductor module. Operational amplifiers 9 and 10 are arranged in evaluation unit 6, according to... Figure 2 The measurement signal is sent to the operational amplifier.

[0041] In the first operational amplifier 9, the interference signal 7 amplifies the useful signal 13, while in the second operational amplifier 10, the interference acts in the opposite direction to the useful signal 13. Through subsequent analog summation performed by operational amplifiers 9 and 10, particularly through the resistor circuit 11 of the two signals, the interference signal 7 (see...) is amplified. Figure 3 )wipe out.

[0042] Due to the strong gradient of the interference field, interference voltages can be induced in the two loops 18 and 19 at different values. This effect can be avoided or at least significantly reduced by guiding the measurement lines 20, 21, and 22 to be particularly closely parallel. Importantly, the unfolded areas of loops 18 and 19 should be as similar as possible to obtain signals 14 with the same absolute value.

[0043] Therefore, with the proposed solution, small voltage signals from shunt resistor 1 can be measured in an interference-insensitive manner. Thus, it is practically possible to use a small shunt resistor 1 for a 50mV measurement range of analog-to-digital converter 12.

[0044] The following advantages are achieved by using a power semiconductor module with shunt resistor 1 and a method for measuring the current in power current path 17: According to the present invention, relatively fast current measurements are now possible because the filter cutoff frequency of the anti-aliasing filter can be increased from less than 100 kHz to greater than or equal to 300 kHz.

[0045] The difference in shunt resistor 1 can be reduced, thus saving the number of shunt resistors 1 by measuring a voltage range of 50mV.

[0046] - The required assembly area in power semiconductor modules can be reduced, which facilitates more compact designs.

[0047] - The design according to the invention also results in a reduction in power loss, particularly at the shunt resistor 1.

[0048] - The design according to the invention also allows for automated manufacturing, at least within this range of power semiconductor modules.

Claims

1. A power semiconductor module having a power current path (17) in which a shunt resistor (1) is arranged, said shunt resistor being, in particular, a resistor less than or equal to 50 milliohms. in, The shunt resistor (1) has two main measuring contacts (2, 3) spaced apart from each other with different polarities (+, -), and an auxiliary measuring contact (4) is arranged adjacent to the shunt resistor (1). The auxiliary measuring contact is not directly electrically connected to the shunt resistor. The measurement lines (20, 21, 22) are guided from each measurement contact (2, 3, 4) to the evaluation unit (6) and the measurement lines simultaneously form loops (18, 19) of almost the same area, such that there are three measurement lines (20, 21, 22) forming two loops (18, 19) that are symmetrical to each other, such that the interference coupling input at the input of the evaluation unit (6) causes interference voltages with different directions.

2. The power semiconductor module with a power current path (17) according to claim 1, characterized in that, The distance from the auxiliary measuring contact (4) to the first main measuring contact (2) is equal in size to the distance between the first main measuring contact (2) and the second main measuring contact (3).

3. The power semiconductor module having a power current path (17) according to claim 1 or 2, characterized in that, The auxiliary measurement contact (4) is formed by means of an electrical bridge (5) from the second main measurement contact (3).

4. A power semiconductor module having a power current path (17) according to any one of the preceding claims, characterized in that, The measurement lines (20, 21, 22) extend substantially in a plane.

5. A power semiconductor module having a power current path (17) according to any one of the preceding claims, characterized in that, The measurement lines (20, 21, 22) are adjacent to each other and extend parallel to the evaluation unit (6).

6. A power semiconductor module having a power current path (17) according to any one of the preceding claims, characterized in that, The evaluation unit (6) has a summing circuit and at least two operational amplifiers (9, 10).

7. A power converter for a drive unit, the power converter having at least one power semiconductor module according to any one of claims 1 to 6.

8. A method for performing interference-insensitive current measurement in a power semiconductor module having a power current path (17), wherein a shunt resistor (1) is arranged in the power current path, the shunt resistor being, in particular, a resistor less than or equal to 50 milliohms. in, The shunt resistor (1) has two main measuring contacts (2, 3) spaced apart from each other with different polarities (+, -), and an auxiliary measuring contact (4) is arranged adjacent to the shunt resistor (1). The auxiliary measuring contact is not directly electrically connected to the shunt resistor. The measurement lines (20, 21, 22) lead from each measurement contact (2, 3, 4) to the evaluation unit (6), and the measurement lines simultaneously form loops (18, 19) of almost the same area, resulting in three measurement lines (20, 21, 22). These three measurement lines form two mutually symmetrical loops (18, 19), causing interference coupling input at the input of the evaluation unit (6) to induce interference voltages with different directions. The method comprises the following steps: - Acquire measurement signals at measurement contacts (2, 3, 4). The measurement signals are provided to the evaluation unit (6) via measurement lines (20, 21, 22). - Within the evaluation unit (6), a corrected measurement signal (useful signal) is generated by means of an operational amplifier (9, 10) and analog summation of the two outputs of the operational amplifier (9, 10), especially by means of a resistor circuit. The useful signal is then sent to the analog-to-digital converter (12) for further processing in the controller, particularly the drive controller.

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