INTERFERENCE-FREE TRANSMISSION OF SIGNALS BETWEEN DIFFERENT EARTH POTENTIALS

Abstract

The invention relates to a coupler (1) for differential transmission of an analogue signal (3) coming from at least one transmitter (2) with a first earth potential (2a), via at least one first signal line (4a) and a second signal line (4b), to a receiver (5) with a second earth potential (5a). wherein the coupler (1) has a filter assembly (6) for the portions (3a, 3b) of the signal (3) being transmitted via the first signal line (4a) or via the second signal line (4b). w herein this filter assembly (6) is potential-free or uses the second earth potential (5a), and wherein the portions (3a′, 3b′) of the signal (3) filtered by the filter assembly (6) are brought together in a comparator (7) in order to form the signal (8) to be supplied to the receiver (5), and wherein the comparator (7) uses the second earth potential (5a). The invention also relates to a system (50) for signal transmission and a voltage transformer (100) comprising the coupler (1) and/or system (50).

Claims

1. A coupler (1) for the differential transmission of an analog signal (3), output by at least one transmitter (2) having a first ground potential (2a), via at least a first signal line (4a) and a second signal line (4b), to a receiver (5) having a second ground potential (5a), wherein the coupler (1) comprises: a filter arrangement (6) for the components (3a, 3b) of the signal (3) that are transmitted via the first signal line (4a) and via the second signal line (4b), wherein this filter arrangement (6) is potential-free or uses the second ground potential (5a) and a comparator (7), wherein the components (3a′, 3b′) of the signal (3) that are filtered by the filter arrangement (6) are combined in the comparator (7) to form the signal (8) to be supplied to the receiver (5), and wherein the comparator (7) uses the second ground potential (5a).

2. The coupler (1) as claimed in claim 1, wherein the filter arrangement (6) comprises a common-mode choke.

3. The coupler (1) as claimed in claim 1, wherein the filter arrangement (6) comprises a first low-pass filter (6a) for that component (3a) of the signal (3) that is transmitted via the first signal line (4a) and a second low-pass filter (6b) for that component (3b) of the signal (3) that is transmitted via the second signal line (4b).

4. The coupler (1) as claimed in claim 3, wherein the low-pass filters (6a, 6b) have time constants of at most 5 μs.

5. The coupler (1) as claimed in claim 1, comprising at least one polarity reversal protection element (9) which is designed to divert a voltage that is present on at least one signal line (4a, 4b) and is outside of the specification of at least one input (7a, 7b) of the comparator (7) away from this input (7a, 7b).

6. The coupler (1) as claimed in claim 5, wherein the polarity reversal protection element (9) comprises a series circuit of two diodes (9c, 9d) that is connected in the reverse direction between two predetermined potentials (9a, 9b), and wherein the input (7a, 7b) of the comparator (7) is connected to the connection between the two diodes (9c, 9d) in the series circuit.

7. A system (50) for the differential transmission of an analog signal (3), output by at least one transmitter (2) having a first ground potential (2a), via at least a first signal line (4a) and a second signal line (4b), to a receiver (5) having a second ground potential (5a), the system comprising: a first, inverting amplifier (10a) that generates a component (3a) of the signal (3) that is transmitted via the first signal line (4a), a second, non-inverting amplifier (10b) that generates a component (3b) of the signal (3) that is transmitted via the second signal line (4b), and a coupler (1) having a filter arrangement (6) for the components (3a, 3b) of the signal (3), wherein the filter arrangement (6) is potential-free or uses the second ground potential (5a), and a comparator (7), and a comparator (7), wherein the components (3a′, 3b′) of the signal (3) that are filtered by the filter arrangement (6) are combined in the comparator (7) to form a signal (8) to be supplied to the receiver (5), and wherein the comparator (7) uses the second ground potential (5a), wherein the amplifiers (10a, 10b) use the first ground potential (2a).

8. The system (50) as claimed in claim 7, further comprising at least one polarity reversal protection element (11).

9. The system (50) as claimed in claim 8, wherein the polarity reversal protection element (11) comprises at least one diode connected between the output (10a′, 10b′) of the inverting or non-inverting amplifier (10a, 10b) and the first or second signal line (4a, 4b).

10. A voltage converter (100) for converting between a DC voltage at a DC voltage gate (101) and a multiphase AC voltage at an AC voltage gate (102), comprising an arrangement of switching elements (103a-103f), via which each phase (102a-102c) of the AC voltage gate (102) can be selectively connected to the positive pole or to the negative pole of the DC voltage gate (101), wherein a coupler (1) as claimed in claim 1 is provided for transmitting a control signal (3) between a first gate driver which is associated with the first switching element (103a-103f) of the arrangement and a second gate driver which is associated with a second switching element (103a-103f) which is associated with another phase (102a-102c) of the AC voltage gate (102).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further measures which improve the invention are described in more detail below together with the description of the preferred exemplary embodiments of the invention on the basis of figures.

[0025] FIG. 1 shows a block diagram of an exemplary system 50 having a coupler 1;

[0026] FIG. 2 shows an exemplary circuit diagram for implementing the system 50 having a coupler 1 and shown in FIG. 1;

[0027] FIG. 3 shows an exemplary voltage converter 100.

DETAILED DESCRIPTION

[0028] According to FIG. 1, a signal 3 is to be transmitted by a transmitter 2 having a first ground potential 2a to a receiver 5 having a second ground potential 5a. For this purpose, the system 50 contains an inverting amplifier 10a, at the output 10a′ of which a first component 3a of the signal 3 is output, and a non-inverting amplifier 10b, at the output 10b′ of which a second component 3b of the signal 3 is output. The two amplifiers 10a and 10b use the first ground potential 2a, that is to say they have this in common with the transmitter 2

[0029] The components 3a and 3b of the signal 3 are transmitted via signal lines 4a and 4b to the coupler 1 that produces the signal 8 to be supplied to the receiver 5. The coupler 1 contains a filter arrangement 6 on the input side. In this example, the filter arrangement 6 comprises a first low-pass filter 6a for that component 3a of the signal 3 that is transmitted via the first signal line 4a and a second low-pass filter 6b for that component 3b of the signal 3 that is transmitted via the second signal line 4b. The two filters use the second ground potential 5a, that is to say they have this in common with the receiver 5.

[0030] The components 3a′, 3b′ of the signal 3 that are filtered by the filters 6a and 6b are supplied to the inputs 7a and 7b of the comparator 7. The comparator 7 subtracts the components 3a′ and 3b′ from one another and uses the result to form the signal 8 to be supplied to the receiver 5. The comparator uses the ground potential 5a of the receiver 5.

[0031] FIG. 2 shows an exemplary circuit-based implementation of the system 1 shown in FIG. 1. Some details are visible here that have been omitted in FIG. 1 for the sake of clarity. The outputs 10a′, 10b′ of the amplifiers 10a, 10b are thus protected against overvoltages on the signal lines 4a and 4b by way of a polarity reversal protection element 11 that comprises two diodes in this example. Analogously, the two inputs 7a and 7b of the comparator 7 are protected by polarity reversal protection elements 9 that in each case contain a series circuit of two diodes 9c and 9d between the second ground potential 5a=9a and a further positive potential 9b. The respective input of the comparator 7a, 7b is in each case connected to the connection between the two diodes 9c, 9d in the series circuit. When the respective voltage leaves the range between the potentials 9a and 9b, it is diverted such that the comparator 7 is not loaded.

[0032] In FIG. 2, it can be additionally seen that the comparator 7, in addition to the integrated module with the inputs 7a and 7b, also has a circuit downstream of the output of this module. This circuit ensures that the signal 8 supplied to the receiver 5 is in the voltage range that the receiver 5 expects.

[0033] Within the coupler 1, it is furthermore evident that the low-pass filters 6a and 6b are each implemented as RC filters in the filter arrangement 6. Furthermore, the differences between the inverting amplifier 10a and the non-inverting amplifier 10b are discernible. The two amplifiers 10a and 10b are constructed with transistor stages in this case. Prefabricated operational amplifiers can also be used however, several of which can be combined in an integrated circuit, for example.

[0034] FIG. 3 shows an exemplary embodiment of a voltage converter 100 which is in the form of an inverter and has a DC voltage gate 101 and an AC voltage gate 102. The voltage converter 100 is designed to convert the intermediate circuit voltage U.sub.ZK, present at the DC voltage gate 101, into a multiphase AC voltage at the AC voltage gate 102 by way of temporal clocking of the switching elements 103a-103f so that the multiphase AC voltage drives a current Is through stator windings of an electric motor not depicted in FIG. 3.

[0035] Drive circuits, in particular gate drivers, for driving the gates of the switching elements 103a-103f are also not depicted in FIG. 3 for the sake of clarity. In particular, the drive circuits of the “high-side” switching elements 103a, 103c and 103e are supplied by separate voltage supplies independently of one another. The drive circuits of the “low-side” switching elements 103b, 103d and 103f are supplied by a common voltage supply, a common gate driver voltage supply. In the event of a fault, this can lead to particularly high ground offsets between the “low-side” switching elements 103b, 103d and 103f, in particular the drive circuits of the “low-side” switching elements 103b, 103d and 103f. To prevent the signal transmission between the “low-side” switching elements 103b, 103d and 103f, in particular the drive circuits of the “low-side” switching elements 103b, 103d and 103f, from responding incorrectly, it is necessary to transmit a control signal 3 reliably from a “low-side” switching element 103b, acting as transmitter 2, to the other two “low-side” switching elements 103d and 103f, acting as receiver 5, by means of the coupler in the system of the voltage converter. As a consequence of the independent rapid clocking of the switching elements 103b, 103d, 103f during normal operation of the AC voltage supply, voltages are induced in the unavoidable parasitic inductances L.sub.p in the respective connections to the negative pole of the DC voltage gate 101 and lead to a ground offset between the “low-side” switching elements 103b, 103d, 103f, in particular the drive circuits of the “low-side” switching elements 103b, 103d and 103f. Desired transmission of the control signal 3 is achieved by means of the system 50 with integrated coupler 1, despite the ground offset. The arrangement or placing of the systems 50 in FIG. 3 is purely schematic. In reality, the system 50 is positioned as closely as possible to the respective receiver 5.

[0036] In a similar way, the parasitic inductances L.sub.p are also present in the connections between the “high-side” switching elements 103a, 103c, 103e, on the one hand, and the positive pole of the DC voltage gate 101, on the other hand. This is not depicted in FIG. 3, however, since the effect of the voltages induced here is canceled out by the independent supply of the “high-side” switching elements 103a, 103c, 103e.