Circuit with resistive protector

Abstract

The invention describes a circuit (100) having (i) at least one electrical component (110) and (ii) at least one zero-ohmic resistor (120), where each of the zero-ohmic resistors (120) is connected in series with the associated electrical component (110), where the zero-ohmic resistors (120) are connected in series with the associated electrical component (110). Each of the zero ohmic resistors (120) is designed to interrupt an electrical connection with an associated electrical component (110) in the event of a failure of the associated electrical component (110).

Description

Technical Field

[0001] This disclosure relates to electronic circuits that use zero-ohm resistors to protect components. Background Technology

[0002] A short circuit in an electronic component can cause excessive heat generation and serious damage to the component itself, the circuitry containing it, or related products. In the worst case, a short circuit can cause the circuit to burn out, posing a serious safety risk.

[0003] For example, short circuits can occur in ceramic capacitors due to excessive bending stress. Such capacitors can be used, for instance, in EMC filters or in intermediate circuits used in inverters and converters. To mitigate the risk of short circuits, "open-circuit mode" ceramic capacitors or "soft-terminated" ceramic capacitors are typically used. However, despite having the same design, "open-circuit mode" ceramic capacitors have lower capacitance values. Furthermore, both types of capacitors are relatively expensive.

[0004] To mitigate the risk of short circuits, a fuse can be installed in the common power supply line leading to the circuit's voltage source. For example, such a fuse can be implemented by inserting a soldered spring wire into the power supply line. In the event of a short circuit, the wire detaches from the solder, and the spring action breaks the circuit. This prevents the short circuit and any potential burnout. However, at the same time, the circuit's function ceases. Summary of the Invention

[0005] Therefore, the purpose of this disclosure is to protect circuits from faults such as short circuits and the associated risks as efficiently and cost-effectively as possible. Where possible, even in the event of a fault, the basic functions of the circuit should be maintained to a large extent.

[0006] This objective is achieved by the circuit according to the independent claim. Advantageous and other embodiments of the circuit are shown in the dependent claims, the following description, and the accompanying drawings.

[0007] According to one aspect of this disclosure, a circuit is provided having: (i) at least one electrical component and (ii) at least one zero-ohm resistor, wherein each of the zero-ohm resistors is connected in series with an associated electrical component. Each of the zero-ohm resistors is designed to interrupt the electrical connection with the associated electrical component in the event of a failure of the associated electrical component.

[0008] In the context of this disclosure, the term "zero-ohm resistor" specifically refers to an electrical connection element that is physically designed as a resistor, such as a cylindrical resistor or an SMD (surface mount device) resistor. A zero-ohm resistor can be marked, for example, by a single black ring in the case of a cylindrical resistor, or by one or more zeros in the case of an SMD resistor. Zero-ohm resistors can be placed on a printed circuit board to connect to conductors on the printed circuit board.

[0009] According to one implementation, only the maximum resistance value and / or maximum power are specified for a zero-ohm resistor, and the maximum resistance value and / or maximum power depend specifically on the size and / or design of the zero-ohm resistor. Therefore, the specification can only specify the maximum resistance value of the zero-ohm resistor, not the minimum resistance value other than zero. The maximum resistance value can, for example, be at most 300 mΩ, particularly at most 100 mΩ, particularly at most 50 mΩ, particularly at most 20 mΩ. The actual resistance value can be greater than 0 mΩ.

[0010] According to one implementation, the value of a zero-ohm resistor, particularly its actual resistance value, is defined by an upper and lower limit. Therefore, the average resistance value can be specified as the nominal value, and the upper and lower limits of the resistance value can be specified as the tolerance of the resistance value. The upper limit can be, for example, 300 mΩ, particularly 100 mΩ, particularly 50 mΩ, particularly 20 mΩ. In other words, the resistance value of a zero-ohm resistor can be less than or equal to 300 mΩ, particularly less than or equal to 100 mΩ, particularly less than or equal to 50 mΩ, particularly less than or equal to 20 mΩ. The resistance value can be greater than 0 mΩ. The resistance value can be determined via a four-wire measurement method or a four-conductor measurement method. Determining the nominal resistance value may involve averaging multiple measurement results. The distribution of the resistance value's tolerance can be considered by taking into account multiple standard deviations, particularly three standard deviations.

[0011] According to one embodiment, a zero-ohm resistor is an SMD resistor. This resistor can be manufactured using thick-film or thin-film techniques. The resistor may have a ceramic substrate material, such as aluminum oxide. One or more resistive layers, such as one or more thick-film pastes, can be applied to this substrate material. The thick-film paste can be printed onto the substrate material and then fired.

[0012] In the context of this disclosure, the term "electrical component" specifically refers to a component of a circuit designed for a given function. For example, an electrical component may be a capacitor, inductor, diode, transistor, or integrated circuit, or may include capacitors, inductors, diodes, transistors, or integrated circuits. Electrical components may be active or passive. Preferably, the component is a capacitor, particularly a ceramic capacitor.

[0013] According to one embodiment, at least one zero-ohm resistor, and in particular multiple zero-ohm resistors, protect different types of components. According to an alternative embodiment, all zero-ohm resistors protect the same type of component, such as capacitors, particularly ceramic capacitors.

[0014] In one embodiment, the fault is a short circuit in an electrical component. If the component is a capacitor, particularly a ceramic capacitor, the short circuit may be caused by capacitor breakage due to excessive bending stress on the capacitor.

[0015] The described circuit enables cost-effective protection of one or more electrical components from faults and / or their consequences. For example, the power rating of a zero-ohm resistor can be adapted to the relevant application context. In particular, a zero-ohm resistor can be defined as a fuse element such that, under all relevant tolerance conditions, the functional state of the component—that is, normal operation of the component—is sufficiently different from a component failure (in which the resistive fuse is triggered).

[0016] By protecting each critical component, and especially by protecting different components separately, the circuit's function can be at least partially maintained even if one or more components fail. Furthermore, zero-ohm resistors, when designed as individual components, are easier to replace in the event of a failure than, for example, a damaged conductor on a printed circuit board. This makes it possible to use zero-ohm resistive fuses to ensure circuit function particularly effectively, and to easily and cost-effectively restore circuit function when necessary.

[0017] According to one implementation, the resistance value of a zero-ohm resistor is less than or equal to 50 mΩ, particularly less than or equal to 20 mΩ. Different zero-ohm resistors can have the same resistance value or different resistance values. Such resistance values ​​can be on the order of the conductor connections or solder joints. The resistance values ​​of other resistors used in the circuit can be larger than the resistance value of the zero-ohm resistor, particularly at least two, five, or ten times larger.

[0018] According to one implementation, in the event of a fault, the minimum short-circuit current and / or the minimum short-circuit power specified by the zero-ohm resistor are exceeded. This results in an interruption of the electrical connection to the associated component. The minimum short-circuit power can be defined based on the rated or nominal power of the zero-ohm resistor, for example, it can be defined as a factor greater than twice the nominal power, particularly greater than or equal to twice the nominal power. According to one design, if the specified minimum short-circuit power and / or the specified minimum short-circuit current are exceeded, a resistive fuse formed by the zero-ohm resistor is triggered. The tripping of the resistive fuse may interrupt the current flowing through the component.

[0019] Such an implementation can be advantageous because the zero-ohm resistor, in particular its minimum short-circuit current and / or minimum short-circuit power, can be adapted to a specific application, such as to prevent a specific fault. For example, the power rating of the zero-ohm resistor can be adapted to the application.

[0020] According to one implementation, the power rating of the zero-ohm resistor is selected based on the electrical components and / or circuitry. The zero-ohm resistor can be selected such that the minimum short-circuit current and / or minimum short-circuit power will not be reached when the electrical components or circuitry are operating correctly; however, in the event of a fault, the minimum short-circuit current and / or minimum short-circuit power will be exceeded.

[0021] According to one embodiment, at least one zero-ohm resistor and at least one electrical component are arranged on a printed circuit board.

[0022] According to one embodiment, the area of ​​the circuit board that includes at least one zero-ohm resistor is molded or encapsulated with plastic. All zero-ohm resistors can be molded or encapsulated with plastic. The plastic can be a thermosetting plastic or a thermoplastic plastic.

[0023] This implementation can be advantageous because zero-ohm resistance fuses retain their function even after being overmolded. However, conventional fuses, such as those using spring wires, no longer reliably trigger after being overmolded in plastic. During desoldering, the spring effect is not present because the spring wire is mechanically fixed by the overmolding and therefore cannot bounce. This can be avoided by leaving an unencapsulated area around the spring wire, but this involves considerable work. In the case of zero-ohm resistance fuses, such an unencapsulated area is unnecessary.

[0024] According to one embodiment, a zero-ohm resistor includes a substrate, particularly a ceramic body, and a resistive material applied to the substrate, wherein the zero-ohm resistor is arranged such that the resistive material faces the printed circuit board. For example, the resistive material can be applied to the substrate in the form of a layer. The resistive material can be a resistive paste or contain a resistive paste, such as a RuO2 paste. The substrate can have a ceramic support material, such as aluminum oxide.

[0025] The tripping time of a zero-ohm resistor can be adjusted by arranging the resistor material facing the circuit board. This reduces the trigger time compared to arranging a zero-ohm resistor with the resistor material facing the molding material. In other words, if the resistor material is oriented towards the molding material, the mass of the molded component may increase the trigger time of the zero-ohm resistor.

[0026] According to one embodiment, a zero-ohm resistor is a metal film resistor. In the context of this disclosure, a "metal film resistor" specifically refers to a resistor in which the resistive element is applied as a layer onto a carrier. Using a metal film resistor can be advantageous because it can have low tolerances. The layer can be applied, for example, in the form of a resistive paste, and particularly printed on.

[0027] This implementation can be advantageous because, in the event of a short circuit, the resistive paste melts, thereby disrupting the electrical connection with the component. The resistive paste may at least partially become gaseous and expand. However, the expansion may be small enough that the encapsulated molded part does not burst or crack.

[0028] According to one embodiment, the circuit has at least two zero-ohm resistors, each of which is connected in series with an associated electrical component, wherein the series-connected zero-ohm resistors and the associated electrical components are connected in parallel with each other.

[0029] This implementation can be advantageous because, in the event of a component failure, only the affected path fails due to the triggering of the associated resistive fuse, while the parallel-connected paths remain intact and thus at least partially maintain the circuit's function. Zero-ohm resistors may be particularly well-suited for such an arrangement because they are inexpensive, space-saving, and can be adapted to the corresponding component, for example, in terms of triggering criteria.

[0030] According to one embodiment, the circuit includes at least three zero-ohm resistors, particularly at least five zero-ohm resistors, particularly at least ten zero-ohm resistors, and at least three, five, or ten associated electrical components arranged as just described. The more components included, the smaller the impact of a single component failure, allowing functionality to be largely maintained. For example, in the case of twenty identical capacitors connected in parallel, the capacitance loss in the event of a short circuit is only 5%.

[0031] According to one embodiment, one of the zero-ohm resistors is connected in series with a sub-circuit comprising at least two electrical components, wherein the zero-ohm resistor connected in series with the sub-circuit is designed to disconnect the electrical connection with the sub-circuit in the event of a failure of the sub-circuit.

[0032] In the context of this disclosure, the term "subcircuit" specifically means, for example, a connection portion of a circuit connected by suitable electrical conductors.

[0033] Because the subcircuit is connected in series with the previously mentioned zero-ohm resistor, no current flows through the subcircuit when the zero-ohm resistive fuse is triggered. This implementation can be advantageous in this respect because when the resistive fuse is triggered, the entire subcircuit is disconnected from current, particularly at least two other components. Therefore, only one fuse is needed for multiple electrical components. Furthermore, the frequency response of the circuit can be affected by jointly protecting multiple components in the subcircuit.

[0034] According to one embodiment, a zero-ohm resistor connected in series with a sub-circuit is arranged in a longitudinal branch of the circuit, particularly in a longitudinal branch of an intermediate circuit. In the context of this disclosure, the term "longitudinal branch" can be specifically defined as an electrical line that originates from a voltage pole and is parallel to another electrical line originating from another voltage pole. The zero-ohm resistor can be placed in this electrical line.

[0035] Such an implementation can be advantageous in order to improve the high-frequency behavior of the circuit, particularly the intermediate circuitry. For example, this could be due to the reduction of inductance and / or alteration of the circuit's resonant point through the joint protection of the capacitor by a zero-ohm resistor.

[0036] According to one embodiment, an additional zero-ohm resistor is arranged in a cross branch of the circuit, particularly in a cross branch of an intermediate circuit. In the context of this disclosure, the term "cross branch" can be specifically defined as an electrical conductor connecting two other electrical conductors leading from corresponding voltage poles.

[0037] According to one embodiment, one of the zero-ohm resistors is connected in series with only one electrical component to protect that component, or connected in series with at least two components connected in parallel to protect them. Individual protection is advantageous because only one component fails in the event of a short circuit, and the function of the remaining circuit is largely maintained; joint protection of at least two parallel-connected electrical components saves space and cost.

[0038] According to one embodiment, at least one electrical component is a capacitor, particularly a ceramic capacitor. All electrical components can be capacitors. Alternatively, at least one of the electrical components may not be a capacitor.

[0039] This implementation can be advantageous because capacitors, especially ceramic capacitors, can be particularly prone to short circuits, for example, due to excessive bending stress on the capacitor. Therefore, "open-circuit mode" or "soft-terminated" ceramic capacitors are typically used, but these are expensive. In contrast, protecting the capacitor using a zero-ohm resistive fuse is a cost-effective alternative.

[0040] According to one embodiment, the circuit includes an EMC filter (electromagnetic compatibility filter), particularly a low-pass filter, or intermediate circuitry for an inverter and / or converter. Such a circuit may contain multiple capacitors, particularly ceramic capacitors, which must be protected against short circuits. According to one embodiment, the circuit is an EMC filter, particularly a low-pass filter, or intermediate circuitry for an inverter and / or converter. Attached Figure Description

[0041] Other advantages and advantageous implementations of the method and control unit, as well as further developments, are illustrated in the following exemplary embodiments, taken in conjunction with the accompanying drawings.

[0042] Figure 1 A circuit according to a first exemplary embodiment of the present disclosure is shown.

[0043] Figure 2 A circuit according to a second exemplary embodiment of the present disclosure is shown.

[0044] Identical, similar, or equivalent elements are designated with the same reference numerals in the accompanying drawings. In some drawings, individual reference numerals may be omitted for clarity. The scale of the drawings and the elements shown in them should not be considered to be proportional. Rather, individual elements may be shown at exaggerated dimensions to facilitate depiction and / or understanding. Detailed Implementation

[0045] Figure 1 A circuit 100 according to a first exemplary embodiment is shown. Circuit 100 has a zero-ohm resistor 120 and three electrical components 110 connected in parallel with each other, the electrical components to be protected and connected in series with the zero-ohm resistor 120. The component 110 to be protected is a capacitor. The zero-ohm resistor is designed to interrupt the electrical connection with component 110 (i.e., with the sub-circuit comprising the three components 110) in the event of a failure of the component 110 to be protected.

[0046] The 120 zero-ohm resistor is a 0 Ω SMD (surface mount device) resistor. SMD resistors are available in various power ratings, such as 0.1 W (type 0603), 0.125 W (type 0805), and 0.25 W (type 1206). This allows the resistive fuse to be adapted to all expected conditions in a functional application without triggering the protection.

[0047] With the help of (Equation 1) allows for the selection of component shape based on the required maximum power dissipation. Since the resistance value is defined as 0 Ω for a 0 Ω resistor, the actual value must be determined using a statistically significant number of measurements via a 4-wire measurement method. To obtain the lowest possible resistance tolerance, a metal film resistor should be used. The corresponding measurement series yielded the following results: at 0.1 W (0603): 17.5 mΩ ± 3.5 mΩ; at 0.125 W (0805): 7 mΩ ± 1 mΩ; at 0.25 W (1206): 14 mΩ ± 1 mΩ.

[0048] To ensure reliability across different batches, the circuit is designed with a higher assumed tolerance (±40%). Furthermore, when using multiple resistor suppliers, resistor values ​​must be determined for each supplier, which may lead to increased tolerances.

[0049] After resistor 120 has been reliably designed for normal operation of circuit 100, short-circuit conditions, i.e., fuse tripping, should now be considered. For this, the minimum short-circuit current at which the fuse should trip must be determined. This will inevitably lead to multiple overruns of the nominal power rating of resistor 120 (Equation 1). Besides the magnitude of the short-circuit power at the resistive fuse, the mounting conditions (thermal characteristics) of resistor 120 will also affect its tripping behavior, especially when the short-circuit current increases slowly. In the event of a rapid event, such as a rapid event due to the rupture of a ceramic capacitor, the effect of the thermal characteristics defined by the mounting conditions can be ignored. To ensure the same applies to the case of a molded / packaged printed circuit board, resistor 120 should be positioned such that its resistive plane faces the printed circuit board.

[0050] Figure 2 A circuit 100 according to a second exemplary embodiment is shown. Circuit 100 (here, an intermediate circuit of an inverter or converter) has ten capacitors 110 connected in parallel with each other. Eight zero-ohm resistors 120 are connected in series with each individual associated capacitor 110. These zero-ohm resistors 120 are designed to interrupt the electrical connection with the associated capacitor 110 in the event of a failure of the associated capacitor 110. However, the other capacitors 110 connected in parallel are unaffected, and their corresponding electrical connections remain intact.

[0051] Another zero-ohm resistor 122 is arranged in the longitudinal branch of the intermediate circuit, and is connected with the resistor containing... Figure 2 The sub-circuits of the two capacitors 110 shown on the right are connected in series. The additional zero-ohm resistor 122 is designed to interrupt the corresponding electrical connection with the capacitor 110 or sub-circuit in the event of a failure of one of the two aforementioned capacitors 110.

[0052] Because such resistive fuses are small and inexpensive, they can be used as... Figure 2 The capacitor 110 is connected in series with the corresponding capacitor 110. This means that in the event of a short circuit in capacitor 110, only the affected capacitor 110 itself is lost. For example, in an intermediate circuit with twenty identical capacitors 110 connected in parallel, this is equivalent to a capacitance loss of only 5%, meaning the converter / inverter remains functional. Multiple capacitors 110 connected in parallel can also be protected by a resistive fuse. Since the series connection of resistor 120 with capacitor 110 increases the inductance of the corresponding capacitor branch, a portion of capacitor 110 (e.g., capacitors in the intermediate circuit) can be protected by a resistive fuse 122 in the longitudinal branch, such as... Figure 2 As shown. This can improve the high-frequency performance of the overall device.

[0053] This invention is not limited to the description based on exemplary embodiments. Rather, the invention includes any new features and any combination of features, particularly any combination of features in the exemplary embodiments and the patent claims.

[0054] List of reference numerals 100 Electronic Circuits 110 Electronic Components 120 zero-ohm resistor 122 Another zero-ohm resistor

Claims

1. A circuit (100) having At least one electrical component (110) and At least one zero-ohm resistor (120), wherein, Each of the zero-ohm resistors (120) is connected in series with an associated electrical component (110). Each of the zero-ohm resistors (120) is designed to interrupt the electrical connection with the associated electrical component (110) in the event of a failure of the associated electrical component (110).

2. The circuit (100) according to the preceding claim, wherein, In the event of a fault, the minimum short-circuit current and / or the minimum short-circuit power specified by the zero-ohm resistor (120) are exceeded.

3. The circuit (100) according to any one of the preceding claims, wherein, The power rating of the zero-ohm resistor (120) is selected based on the electrical component (110) and / or the circuit (100).

4. The circuit (100) according to any one of the preceding claims, wherein, The at least one zero-ohm resistor (120) and the at least one electrical component (110) are arranged on a printed circuit board, and the area of ​​the printed circuit board including at least one of the zero-ohm resistors (120) is molded with plastic overlay.

5. The circuit (100) according to the preceding claim, wherein, The zero-ohm resistor (120) includes a substrate, particularly a ceramic body, and a resistive material applied to the substrate, wherein the zero-ohm resistor (120) is arranged such that the resistive material faces the printed circuit board.

6. The circuit (100) according to any one of the preceding claims, wherein, The zero-ohm resistor (120) is a metal film resistor.

7. The circuit (100) according to any one of the preceding claims, wherein the circuit has at least two zero-ohm resistors (120), wherein, Each of the zero-ohm resistors (120) is connected in series with an associated electrical component (110), wherein the series-connected zero-ohm resistors (120) and the associated electrical components (110) are connected in parallel with each other.

8. The circuit (100) according to any one of the preceding claims, wherein, One of the zero-ohm resistors (122) is connected in series with a sub-circuit comprising at least two electrical components (110), wherein the zero-ohm resistor (122) connected in series with the sub-circuit is designed to disconnect from the sub-circuit in the event of a failure of the sub-circuit.

9. The circuit (100) according to the preceding claim, wherein, The circuit (100) is an intermediate circuit, and the zero-ohm resistor (122) connected in series with the sub-circuit is arranged in the longitudinal branch of the intermediate circuit.

10. The circuit (100) according to any one of the preceding claims, wherein, The at least one electrical component (110) is a capacitor, particularly a ceramic capacitor.

11. The circuit (100) according to any one of the preceding claims, the circuit having an EMC filter, particularly a low-pass filter, or intermediate circuitry for an inverter and / or converter.

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