Printed board

Abstract

To aim for a solution with obviously lower inductance to fully exploit the potential of the PCB clamping path.SOLUTION: In a printed board (10) with a braking resistor mounted inside, which is formed as a clamping path (12), the clamping path (12) is composed of at least two conductive layers in the printed board, these conductive layers are spaced from each other and allow for reciprocating current flow.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a printed circuit board provided with a braking resistor and an intelligent current distributor provided with such a printed circuit board. The present invention further relates to a method implemented by such a printed circuit board.

Background Art

[0002] A printed circuit board (PCB) is used as a support for electronic components and enables mechanical fixation and electrical connection of these components. Printed circuit boards are used in various electrical and electronic devices, for example, in intelligent current distributors, also called power network guardians (PNGs). PNGs provide a comprehensive concept, especially for the energy on-board network in motor vehicles. In motor vehicles, PNGs always guarantee the current supply to safety-related consumer devices. For this reason, in case of a defect, an electronic disconnect switch that disconnects the safety on-board network from the remaining on-board network can be used.

[0003] A braking resistor is always installed when the current needs to be limited. For example, it is known that a braking circuit having such a braking resistor can shorten the deceleration time of an electric motor. This is achieved by short-circuiting the voltage of the electric motor as a generator during deceleration via a load resistor, thereby generating an electromagnetic braking torque. In particular, when high currents are to be switched on and off, it is necessary to provide a braking path, for example a clamp path, which can convert the energy of the electromagnetic field into thermal energy.

[0004] The function of the braking resistor will be described in detail.

[0005] During pre-charging, the electrical capacitance of the on-board network is charged. To limit the current during charging, a pre-charge path having a resistance of approximately 55 mΩ is required.

[0006] Magnetic energy must be consumed or burned during the disconnection of the channel. A 55 mΩ resistance path can be used to reduce the load on the clamp diode.

[0007] Both functions are realized by the same resistance path. The precharge / clamp path is typically realized by SMD resistors.

[0008] The resistance of the conductor path is

[0009]

Number

[0010] where ρ 20℃ = 17.2 μΩ·mm and

[0011]

Number

[0012] can be calculated using.

[0013] h is the thickness of the conductor path, typically 30 μm or 70 μm.

[0014] The resistance of the conductor path can be adjusted to a specific value.

[0015] The inductance of a two-wire PCB trace is

[0016]

Number

[0017] where

[0018]

Number

[0019] and μ R = 1 can be calculated using

[0020] h is the cloth thickness between both conductor paths and is typically 130 to 150 μm.

[0021] Since both functions, clamping and pre - charge, are in the same time range of a few milliseconds, the heat capacity mainly defines the performance of the resistance.

[0022] The heat capacity can be calculated as follows. C Th = c Th · p · l · w · h Wherein,

[0023]

Number

[0024] and

[0025]

Number

[0026] For example, when a high current is to be switched on or off by a MOSFET, it is necessary to provide a clamping path that can convert the energy of the electromagnetic field into thermal energy.

[0027] As a braking resistor, for example, a so - called clamping path can be used. For example, it is known to realize clamping via a suppressor diode or a measuring resistor, that is, a shunt, which provides sufficient thermal mass.

[0028] The clamping path must have a defined electrical resistance, sufficient thermal mass to absorb energy, and as low an inductance as possible to avoid time delay.

[0029] It is also known to realize a clamping resistance in the outer layer of a printed circuit board. In this regard, the value of the electrical resistance is adjusted via the length L and width B of the conductor path. The heat capacity of the clamping path can be further adjusted without affecting the electrical resistance in the case of a constant L / B ratio. However, this approach generates a relatively large inductance. In particular, when the current in the clamping path should be increased in a very short time, a high induced voltage U = L * di / dt is generated, which hinders the current flow through the clamping path.

Summary of the Invention

Problems to be Solved by the Invention

[0030] Therefore, in order to fully utilize the potential of the PCB clamping path, a solution with a significantly lower inductance is aimed for.

Means for Solving the Problems

[0031] Based on this, a printed circuit board having the features of claim 1, an intelligent current distributor according to claim 6, and a method according to claim 8 are introduced. The embodiments are apparent from the dependent claims and the specification.

[0032] A printed circuit board in which a braking resistor formed as a clamping path is internally mounted, the clamping path being composed of at least two conductive layers in the printed circuit board, these conductive layers extending with a particularly small interval with respect to each other and enabling a reciprocating flow of current, is introduced. Thus, a closed conductor loop for current can be formed.

[0033] This provides a particularly low inductance clamp path within the printed circuit board, in which current flows, for example, in two layers of one core, in the forward path and then back again in the return path. The small spacing of the layers of the printed circuit board achieves a very low inductance. The additional meander-like arrangement within both layers can further reduce the inductance. The connection between these layers can be realized via through-holes.

[0034] If the forward and return conductors in both layers of the core always overlap, the clamp path can also be distributed to multiple cores.

[0035] Implementation in the inner layer has the advantage that, among other things, a particularly small tolerance of the copper thickness can be achieved.

[0036] Moreover, the printed circuit board-based clamp path can be formed self-actively, and the resistance increases during the clamping process. The heat capacity of the clamp path can be adjusted without affecting the electrical resistance or inductance in the case of a constant L / B ratio. The temperature rise of the clamp path can be further adjusted via the heat capacity for a known load state.

[0037] Based on the high temperature coefficient of copper, the following must be noted.

[0038] At the beginning of the clamping process, the clamp path is cold and thus has a low resistance. Therefore, the switch is very well load-reduced. At the end of the clamping process, the clamp path is hot and thus has a high resistance. Therefore, little energy remains for the suppressor diode.

[0039] For example, for a temperature rise of 40 K, the resistance increases by 15%.

[0040] The intelligent current distributor, also referred to as a power network guardian (PNG), has at least one printed circuit board of the type described here.

[0041] This intelligent current distributor is adapted, for example, within an on-board network, to disconnect a channel having safety-related consumer devices from a further channel, and in this regard the clamping path within the printed circuit board is adapted to convert the electrical energy supplied by the disconnection into thermal energy.

[0042] The method described is used to convert electrical energy into thermal energy by means of a printed circuit board of the kind described herein. This method is used, for example, to convert electrical energy supplied by switching of a current using a MOSFET into thermal energy or to shorten the deceleration time of an electric motor. In particular, this method is carried out by an intelligent current distributor.

[0043] Further advantages and aspects of the invention are apparent from the description and the accompanying drawings.

[0044] It is self-evident that the features mentioned above and the features explained further below can be used not only in the presented combinations but also in other combinations or alone without departing from the scope of the invention.

Brief Description of the Drawings

[0045]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0046] The invention is schematically illustrated in the drawings based on embodiments and will be explained in detail below with reference to the drawings.

[0047] Figure 1 schematically shows a printed circuit board 10 incorporating a clamp path 12, and this clamp path 12 also mounts a braking resistor here. This clamp path 12 is a low-inductance clamp path and is incorporated in the printed circuit board 10. This printed circuit board 10 has a thickness of about 1.6 mm.

[0048] The possible layers of the clamp path 12 are clarified on the upper side of this figure. The clamp path 12 includes a first copper layer 20, a first cloth layer 22, a second cloth layer 24, a second copper layer 26, a third cloth layer 28, a third copper layer 30, a fourth cloth layer 32, a fifth cloth layer 34, a fourth copper layer 36, a sixth cloth layer 38, a fifth copper layer 40, a seventh cloth layer 42, an eighth cloth layer 44, and a sixth copper layer 46. The copper layers 20, 26, 30, 36, 40, 46 each have a thickness of, for example, 35 μm.

[0049] Since the current flows in the forward path and then returns in the reverse path in two layers of one core, a particularly low-inductance clamp path is realized. In addition to this, a very small inductance is brought about by the small intervals between the copper layers. The additional meandering arrangement of the copper layers further promotes this.

[0050] If the reciprocating conductors, as clarified by arrows 50 and 52, always overlap in both layers of the core, the clamp path may be distributed among multiple cores.

[0051] Figure 2 shows a possible implementation of the introduced printed circuit board within an intelligent current distributor, a so-called power net guardian (PNG). This figure shows a printed circuit board 100 connected to a load 102 and a battery 104. A first inductance 106 and a second inductance 108 in a switched electrical circuit are further shown.

[0052] Inside the printed circuit board 100, there are provided a logic module 110, a first switching element 112, and a braking resistor 114 to which a second switching element 116 is assigned. When the first switching element 112 opens, the second switching element 116 closes, whereby the energy supplied to the electric circuit, particularly by both inductances 106 and 108, can be converted into heat within the braking resistor 114. That is, the first switching element 112 is an electronic cut-off switch as described above.

[0053] Therefore, both switching elements 112 and 116 typically open and close alternately.

Explanation of Signs

[0054] 10, 100 Printed circuit board 12 Clamping path 20 First copper layer 22 First cloth layer 24 Second cloth layer 26 Second copper layer 28 Third cloth layer 30 Third copper layer 32 Fourth cloth layer 34 Fifth cloth layer 36 Fourth copper layer 38 Sixth cloth layer 40 Fifth copper layer 42 Seventh cloth layer 44 Eighth cloth layer 46 Sixth copper layer 50 Arrow 52 Arrow 102 Load 104 Battery 106 First inductance 108 Second inductance 110 Logic module 112 First switching element 114 Braking resistor 116 Second switching element

Claims

1. A printed circuit board having a braking resistor (114) mounted therein, the braking resistor being formed as a clamp path (12), the clamp path (12) being constituted by at least two conductive layers in the printed circuit board (10, 100), the conductive layers extending at a distance from each other and allowing a reciprocating flow of electric current.

2. 2. The printed circuit board of claim 1, wherein the clamping path (12) is formed by two layers of one core of the printed circuit board (10, 100).

3. The printed circuit board of claim 1, wherein the clamping paths (12) are distributed over a number of cores of the printed circuit board (10, 100).

4. 4. The printed circuit board according to claim 1, wherein a layer of fabric is arranged at least partially between both layers.

5. A printed circuit board according to any one of the preceding claims, wherein a meandering arrangement of copper structures in both layers of one or more cores is provided.

6. An intelligent current distributor comprising at least one printed circuit board (10, 100) according to any one of claims 1 to 5.

7. 7. The intelligent current distributor according to claim 6, adapted to disconnect a channel having a consumer device from a further channel in an on-board network, in which case the clamp path (12) in the printed circuit board (10, 100) is adapted to convert the electrical energy provided by the disconnection into thermal energy.

8. Method for converting electrical energy into thermal energy by means of a printed circuit board (10, 100) according to any one of the preceding claims.

9. 10. The method of claim 8 used to convert electrical energy provided by switching current with MOSFETs into thermal energy.

10. 10. The method according to claim 8 or 9, used to reduce the deceleration time of an electric motor.

11. The method according to any one of claims 8 to 10, implemented by an intelligent current distributor.

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