WO2009065437A1 - Arrangement comprising two galvanically isolated devices communicating bidirectionally with each other - Google Patents

Abstract

The invention for the first time provides an arrangement comprising two galvanically isolated devices (A, B) between which communication signals can be exchanged, wherein the communication signals are exchanged via a single line (P). This can be used, for example, for a device for generating control signals for a display, which communicates with another device used for the physical operation of the display. The arrangement operates particularly efficiently in that transmitters (12, 18) of the devices can emit precisely two different potentials, and that potential combinations of the two transmitters make it possible that four different potentials are present in one point (P) of the single line. In this way, it is possible for receivers (14, 20) to capture the statuses of the respectively other transmitters (18, 12).

Description

 description

ARRANGEMENT OF TWO GALVANIC ISOLATED BIDIRECTIONAL WITH COMMUNICATING EQUIPMENT

Technical area

The invention relates to an arrangement of two galvanically separated devices, between which communication signals are interchangeable. Such an arrangement is required regularly in modern lighting systems in which the lighting is controlled electronically via control signals, so that an electronic device which generates the control signals must communicate with the device used directly for the actual operation of light sources. The above applies in particular to video projection devices which have video projector electronics on the one hand and an electronic ballast for operating a HID projection lamp on the other hand, which are to be electrically isolated from one another. In this case, the video projector electronics not only send control signals to the electronic ballast, but also, for example, return status signals from the electronic ballast to the video projector electronics. Thus, communication signals between the two galvanically separated devices must be interchangeable, so the communication must be bidirectional.

State of the art

So far, with electrically isolated, ie galvanically separated data connections, per data channel and communication cation direction each used at least one data line and a common reference line. For example, a component is driven per data channel and transmission direction, which is used for information transmission in galvanic separation, which z. B. in an optocoupler o- a transformer is the case. It is even known to provide two lines per data channel and communication direction. Two lines per data channel and communication direction are required in particular if the isolating component is controlled with differential signals.

The use of a single data line for bidirectional communication is known only in non-galvanic communication. For example, Philips' so-called I2C bus enables bi-directional communication over a single data line.

The cable outlay for galvanically isolated data connections is extremely high. It would be desirable if this overhead could be reduced.

Presentation of the invention

The object of the present invention is to provide an arrangement of two galvanically separated devices, between which communication signals are interchangeable, in which the least possible amount of wiring has to be operated.

The object is achieved in that the communication signals are exchanged only over a single line. The ideas of the invention that are presented below in the discussion of the dependent claims make it possible for the first time the saving of the further lines. As mentioned above, a preferred application is given when the one device is used to generate control signals for one display and the other device is used to physically operate the display.

In a preferred embodiment of the invention, each device includes a transmitter and a receiver. Each transmitter can switch between two states and, in particular, impose two different states on one line. The arrangement is now constructed in such a way that the states of the transmitters can still be recognized by the receivers. Each receiver has to be able to detect a plurality of states and, because of the detected state, to be able to unambiguously refer back to the state of the respective transmitter belonging to the other device such as the receiver. In that case, the transmitter of the one device can in each case transmit information digitally to the receiver of the respective other device.

Theoretically, it is possible that both transmitters impose such states that on the receiver side only two states can be distinguished and it is not clear from which transmitter these states were caused. In this case, the receiver must receive a signal from the sender of the device to which it belongs if that sender is active, so that the receiver can distinguish between the condition that it must evaluate the signals (signals originate from the sender of the other Device) or does not need to evaluate (signals come from the transmitter of their own institution). The situation is simplified if the arrangement is constructed in such a way that an excellent point in the line can lie at four different potentials, these potentials corresponding in each case to a state combination of the states of the first and second transmitter. The first transmitter has two states and the second also two states, so that there are exactly four combinations. By means of suitable interconnection, it can then be ensured in the case of both receivers that only the signals of interest to these receivers, namely the signals originating from the transmitter of the respective other device, must be evaluated.

The potential at an excellent point may, as in a preferred embodiment, be affected by a transmitter that can apply only two potentials at a potential tap if that excellent point is a voltage divider tap or coupled to one that taps between a reference potential and just the potential tap of the transmitter is provided. The two potentials which the transmitter can apply to the potential tap can be chosen so that a switch coupled to the marked point is or will not be actuated, which triggers the communication via the galvanic barrier. A particularly sensitive switch is a transistor, so that this idea is preferably realized so that the excellent point in the line is coupled to the base of such a transistor, which is connected as a switch in series with a transmitter side of an optical coupler, wherein the Receiver side of the optocoupler with the receiver of the device with the voltage divider circuit is coupled to different means of the two devices.

The coupling of the salient point to a reference potential across an impedance element (preferably a resistor) will cause a determination of the potential applied to the salient point, even if the salient point is coupled to a third potential. This coupling is expediently carried out via the phototransistor of an opto-coupler. Then its transmitter side can be connected to the transmitter of the one device, and this transmitter can cause the phototransistor to turn on or off by setting two different potentials, the excellent point is connected to ground via this phototransistor and thus the potential at the excellent point is affected by compound with mass or not.

In the device in which no galvanic isolation occurs, the potential at the excellent point can be simply analogized by a receiver coupled to the excellent point, e.g. B. via a resistor. The potential at the excellent point can also be supplied to an input of a comparator, at whose second input a reference potential is present. In this embodiment, it can be considered whether the transmitter belonging to the same device as said receiver assumes the one state or the other state. Since the state of the transmitter affects the potential at the point of excellence, as well as the transmitter of the unit which is galvanically isolated from the point of excellence, may be supplied to the other input of the comparator such a reference potential, which is dependent on the state of the own transmitter, so that the output of the comparator is a binary information which gives information about the transmitter which drives the optocoupler. In this case, the receiver operates digitally and is arranged downstream of the comparator.

The invention is also realized by two units of equipment, namely a device unit according to claim 11 and a device unit according to claim 12. The device unit according to claim 11 is the one in which the electrical isolation between transmitter and receiver and an external connection. In the above nomenclature, the transmitter and receiver then belong to the one of the two galvanically isolated devices of the device, while the external connection already no longer belongs to this device and is in doubt part of the line or line connection for this line.

In the device unit in which the galvanic isolation takes place, this is made possible by optocouplers, namely, two optocouplers are required, which comprise a photodiode and a phototransistor in a conventional manner. The photodiode of the first optocoupler is coupled to the transmitter, and the phototransistor of the opto-coupler is coupled to the external terminal, preferably instead of the emitter to the collector. The phototransistor of the second optocoupler is now coupled to the receiver, and the photodiode of this opto-coupler is coupled to the emitter or collector, preferably the collector, of another transistor whose base is coupled to the external terminal. In summary, This means that one and the same connection is coupled, on the one hand, to the base of a switching transistor for the activation of a first optocoupler and, on the other hand, to the phototransistor on the receiver side of a second opto-coupler. This circuit makes it possible for the first time despite the galvanic separation to exchange communication signals via a single line.

The second device unit which can be used in the arrangement according to the invention comprises a transmitter and a receiver and an external terminal, which is coupled to a voltage divider tap (or even this voltage divider tap), wherein the voltage divider tap between a terminal for a reference potential and the transmitter (more specifically, a potential tap of the transmitter). At the same time, the voltage divider tap is coupled to the receiver.

As mentioned above, the voltage divider tap is either (more or less directly, preferably via a resistor) coupled to an analog input of the receiver, and the receiver should then be configured to detect the potential applied to the analog input. It is also possible to couple the voltage divider tap to a first input of a comparator, the output of which is coupled to the receiver, and a reference potential applied by a suitable device to the second input. This device is preferably coupled to the transmitter of the device unit and applies a reference potential dependent on the potential applied to the potential tap of the transmitter to the second input of the comparator. The arrangement according to the invention is preferably formed from the two unit units described above, wherein simply their external terminals are to be coupled together, wherein preferably a line is connected. Usually, one will provide a plug at each of the external terminals, and the two plugs of the unit units are then connected to each other via a plug cable.

Brief description of the drawings

In the following, the invention will be explained in more detail with reference to several exemplary embodiments. Show it:

Fig. 1 shows the circuit diagram of an inventive arrangement according to a first embodiment and

2 shows the circuit diagram of an inventive arrangement according to a second embodiment,

Fig. 3 shows the dependence of the potential at an excellent point in the arrangements of Figs. 1 and 2, respectively, on the potential impressed by the transmitters in this arrangement.

Preferred embodiment of the invention

An arrangement shown schematically in FIGS. 1 and 2 is formed from two units, the components of unit A being shown on the left side of the figure and the components of unit B being on the right side of the figure. To illustrate the boundary, a dividing line 10 is shown. This dividing line 10 may correspond mechanically to one Interface, for example, a connector, where quite two different device units can each have a plug-in connection, which is connected to one another via a plug cable. For the invention, it does not matter in which of the units the galvanic coupling takes place. Thus, the device unit A may include video projector control electronics (not shown) or an electronic ballast. Conversely, the appliance unit B may be an electronic ballast if the appliance unit A is the video projector control electronics, and it may comprise video projector control electronics if the appliance unit A is the electronic ballast. For the invention, it does not matter which data is exchanged between the device units. On the other hand, it is essential that two different units, namely a first unit comprising a transmitter 12 and a receiver 14, preferably as part of a microprocessor 16, with a second unit, which also includes a transmitter 18 and a receiver 20, preferably also formed in a microprocessor 22, communicate with each other via a single data line. This single data line is symbolized here by the point P. At the same time, the two units should be galvanically isolated from each other. This is done by means of optocouplers 24 and 26 in the device unit A, which are constructed in a conventional manner from a photodiode and a phototransistor. The galvanic isolation is symbolized in FIGS. 1 and 2 by a line 28. It should be noted that the electrical isolation takes place within a device unit, namely the unit A, so that the unit A and B itself is not must be galvanically separated from each other. In addition to the communication line, there are in particular two line connections which are provided for the coupling of potentials. A potential VCC Bl of 15 V, generated by a voltage source 32, is transmitted from the device unit A to the device unit B via a first line connection 30. Via the second line 34, a coupling of the masses (GND B) is made possible.

In the device unit A, the structure is now as follows: The transmitter 12 is connected via a resistor R7 of 1 kΩ to the photodiode of the optocoupler 24 and this with the ground potential GND_A (which is galvanically yes of GND_B yes, but in principle can be identical) , The phototransistor of the optocoupler 24 is connected on the emitter side to the ground terminal GND_B. The collector side of the phototransistor is connected to the data line via a resistor R6 of 1 kΩ and, in particular, coupled to the potential P. The potential point P, which symbolizes an external connection for the device unit A, is now coupled via a resistor R4 of 47 kΩ to the base of a transistor T1, which is simultaneously coupled to GND_B via a resistor R3 of 47 kΩ. The emitter of the transistor Tl is also connected to the ground terminal GND_B. The collector terminal of the transistor Tl is now connected in series with a resistor R5 of 1 kΩ and the photodiode of the optocoupler 26, up to the connection of the voltage source 32, at which the potential of 15 V is provided.

The phototransistor of the optocoupler 26 is connected on the collector side to a reference potential VCC_A of 5 V and emitter-side to the receiver 14, whereby the emitters terseite at the same time via a resistor R8 of 1 kΩ to the ground potential GND_A is connected.

Now to the device unit B: In the device unit B a reference potential VCC_B2 of 5 V is to be provided at a point 36. Preferably, but not necessarily, this potential is provided by means of a DC-to-AC converter 38, which is coupled via a connection to the line 30, via which of the device unit A, more precisely from its voltage source 32, the potential of 15V is provided.

The point 36 is coupled to the designated point P via a resistor R9 of 10 kΩ. Also from the point of view of the device unit B, the point P stands for an external connection or the entire data line. The point P is connected to the ground potential GND_B via a capacitor having a capacitance Cl of 100 nF. In addition, it is connected to the transmitter 18 via a resistor Rl of 1 kΩ. Somehow, the potential point P has to be coupled to the receiver 20. This can be done either directly via a resistor R2 of 22 kΩ, the receiver then has to be designed to sample a potential analog and evaluate. This embodiment is shown in FIG. In an alternative to this, which is shown in Fig. 2, the point P with an input 38, in this case the positive input IN +, a comparator 40 is connected. The comparator 40 has a second input 42, namely in the present case the negative input IN-, to which a reference voltage VREF1 or VREF2 is applied, which depends on a state assumed by the transmitter 18 (or a potential connection, not shown in the figure) ) is dependent.

In the present case, the transmitters 12 and 18 of both device units A and B are now designed to be connected to a power source. potential of 0 V or 5 V. The values of the impedance elements and characteristics of the optocouplers 24, 26 of the transistor Tl and the values of the reference potentials are now selected such that at the point P there is a potential which depends both on the potential impressed by the transmitter 12 and on that of the sensor Sender 18 imprinted potential is dependent. The dependence will be explained with reference to FIG. Three curves are shown in FIG. 3: The curve 46 represents an exemplary behavior of the transmitter 12 that is alternately logically high in short sections, namely in the sections labeled 48, and is logically deep between them, namely those indicated at 50 sections. The curve 52 reproduces the behavior of the transmitter 18, which is logically low in one large section 54 and logically high in another large section 54.

If the transmitter 18 is logically low, then a current flows through the resistors R9 and Rl. The voltage at point P is determined by the current. In addition, a current can now flow from point 36 to GND_B, namely when the optocoupler 24 switches. This is the case during sections 48 of curve 46. The additional current causes an additional voltage drop across the resistor R6 (and the phototransistor) and pulls the potential P down to a value of 0.25V. This value can be read off curve 58, which represents the potential at point P. In Sections 60, this value is 0.25V. During sections 50, at logic low (corresponding to section 54) of permanent transmitter 18, potential P is determined almost exclusively by the current flowing through R9 and Rl and is 0.45 V, namely at sections 62 of curve 58.

The situation clearly changes when the transmitter 18 changes over to the curve section 56, that is to say switched up logically. Then no current flows from point 36 to the transmitter 18 because transmitter 18 and point 36 have the same potential. The voltage at the point P is now determined mainly via the leading via the optocoupler 24 branch. During sections 48, that is, when the transmitter 12 is logically high, the photodiode of the opto-coupler 24 sends light to the phototransistor of the opto-coupler 24, which switches and a current flows from point 36 through R9, R6 to GND_B. The potential at point P then settles to a value of 2.6 V, see sections 64 of the curve 58. If the phototransistor of the optocoupler 24 now blocks, which is the case during the sections 50, the potential at point P is established logical high-end transmitter 18 (see section 56) to a value of 4.6 V, cf. Sections 66 of the curve 58.

In curve 58, it is possible to distinguish between four sections, and thus four potential values, which are distinguishable at point P. These four values correspond to state combinations of the states assumed by the transmitter 12 and the transmitter 18. It must now be detected by the respective receivers 14 and 20, the information from each belonging to the other unit unit transmitter 18 and 12 respectively.

In device unit A, both potential values taken at logic low transmitter 18 are less than 0.25 V potential value (portions 60 of curve 58) and 0.45 V potential value (portions 62 of curve 48) the forward voltage of the transistor Tl, so that it locks. No current can flow through the photodiode of the optocoupler 26, and the receiver detects that the phototransistor of the receiver 14 is not switching. However, as soon as the transmitter 18 logically upshifts (see section 56 in curve 52), the potential at point P exceeds the forward voltage of the transistor T1. It does not matter what the transmitter 12 does, whether the potential at the point P is on the Value of 2.6 V is (ab- 64) or 4.6V (sections 66). The transistor Tl switches in any case, flows through the potential difference from the output from the voltage source 32 15 V to GND_B a current through the photodiode of the optocoupler 26, the resistor R5 and the transistor Tl, the photodiode provides light to the phototransistor of the optocoupler 26, this switches, and the receiver 14 detects this. Thus, the receiver 14 can always distinguish whether the transmitter 18 outputs a logic high or logic low signal. The communication from the device unit B to the unit A is therefore possible.

On the receiver side of the device unit B, the situation is much simpler. In the embodiment according to FIG. 1, the receiver 20 simply samples the potential P, a partial potential still dropping at the resistor R2. The receiver 20 has a simple analog input and measures the potential. The fineness of the scan must enable a distinction between the states corresponding to the sections 60 on the one hand and the sections 62 on the other hand and also a distinction between the states corresponding to sections 64 on the one hand and the states corresponding to sections 66 on the other. Then, the receiver 20 can detect what the transmitter 12 is doing, namely whether it is logically upshifting corresponding to the portions 48 of the curve 46 or switching logic low corresponding to the portions 50 of the curve 46.

In the embodiment of FIG. 2, the potential at point P is supplied directly to the input of comparator 40. In order to be able to deduce the state of the transmitter 12, irrespective of the state of the transmitter 18, due to the potential at the point P, it is necessary to differentiate between the transmitter 18 logically low and the transmitter 18 logically high. In case the transmitter 18 is logically low, At the comparator input IN- through the unit 44 a reference voltage VREFl of 0.35 V is applied. Then it can be distinguished whether the potential of 0.25 V is applied or the potential of 0.45 V, because once the reference voltage is exceeded and exceeded once. The comparator 40 outputs a corresponding digital signal to the receiver 20, which can also evaluate this. In the case that the transmitter 18 is logically high, a distinction must be made between the potentials of 2.6 V and 4.6. For this purpose, the voltage VREF2 of 3.6 V is applied to the comparator input 42. This is also chosen so that in the event that the transmitter 12 is logically low, this voltage is exceeded, because then the potential of 4.6 V is applied, and in the case that the transmitter 12 is logically high, is exceeded, because then the potential of 2.6 V is applied, and even then the comparator 40 can output a digital signal to the receiver 20, which directly reflects the state of the transmitter 12.

The arrangement thus also enables communication from the transmitter 12 of the device unit A to the receiver 20 of the device unit B.

Bidirectional communication can thus take place via the line represented by the potential point P, and this despite a galvanic isolation (see dividing line 28) between the first device with transmitter 12 and receiver 14 and the second device with transmitter 18 and receiver 20.

Claims

claims 1. Arrangement of two galvanically separated devices, between which communication signals are interchangeable, wherein the communication signals are exchanged over a single line. 2. Arrangement according to claim 1, wherein the one device for generating control signals for a display and the other device is used in the physical operation of the display. 3. Arrangement according to claim 1 or 2, wherein each device comprises a transmitter (12, 18) and a receiver (14, 20), and wherein each transmitter (12, 18) can switch between two states (48, 50; 54, 56) and the arrangement is such that each receiver (14, 20) has a plurality of states - Is tangible and due to the detected state clearly on the state of each belonging to the other device such as the receiver transmitter is zurückschließbar. 4. Arrangement according to claim 3, wherein the arrangement is constructed such that an excellent point (P) in the line can lie on four different potentials (60, 62, 64, 66), each of a state combination of States (48, 50, 54, 56) of the first transmitter (12) and the second transmitter (18) correspond. 5. Arrangement according to one of the preceding claims, in which an excellent point (P) in the line is a voltage divider tap between a reference potential tap (36) and a potential tap on which a potential can be impressed by the transmitter (18) of a first device , 6. Arrangement according to claim 5, wherein the excellent point (P) in the line to the base of a transistor (Tl) is coupled, which is connected as a switch in series with a transmitter side of an optocoupler (26), the receiver side with the receiver (14) is coupled to the device other than the first device of the two devices. 7. Arrangement according to one of the preceding claims, in which an excellent point (P) in the line is coupled on the one hand via an impedance element with a reference potential tap (36) and on the other hand with a phototransistor, preferably its collector, is coupled on the receiving side of an optocoupler, wherein the transmitter side of the optocoupler is coupled to the transmitter (12) of a second device of the two devices. An arrangement according to claim 7, wherein the excellent point (P) in the line is coupled through an impedance element (R2) to the receiver (20) of the device other than the second device and is adapted to be an analogue one Evaluate potential. 9. The arrangement of claim 7, wherein the excellent point (P) in the line is coupled to a first input (38) of a comparator (40) coupled to the receiver (20), the second input (42) of the comparator (40) has a reference potential. 10. Arrangement according to claim 9, wherein a device (44) for applying a reference potential to the second input (42) of the comparator (40) is coupled to the transmitter (18) of the device other than the second device of the two devices, and wherein the device, the reference potential to be applied from at least two values ( Vref, Vref2) depending on the state of this transmitter (18). 11. Device unit (A) with a transmitter (12) and a receiver (14) and with an external terminal (P), wherein the terminal (P) by two optocouplers (24, 26) with a photodiode and a phototransistor galvanic is separated from the transmitter (12) and receiver (14), wherein the photodiode of the first optocoupler (24) is coupled to the transmitter and the phototransistor, in particular its collector, of the first optocoupler (24) coupled to the external terminal (P). pelt, and wherein the phototransistor of the second optocoupler (26) is coupled to the receiver (14) and the photodiode of the second optocoupler (26) is coupled to another transistor (T1), preferably its collector, whose base is connected to the first external connection (P) is coupled. A device unit (B) comprising a transmitter (18) and a receiver (20) and an external terminal (P) coupled to a voltage divider tap, the voltage divider tap being connected between a reference potential terminal (36) and the transmitter (18 ) and simultaneously coupled to the receiver (20). 13. The device unit of claim 12, wherein the voltage divider tap (P) is coupled to an analog input of the receiver (20) and the receiver (20) is adapted to detect the potential applied to the analog input. 14. The device unit (B) according to claim 12, wherein the voltage divider tap is coupled to a first input (38) of a comparator (40) whose output is coupled to the receiver (20 '). 15. Arrangement according to one of claims 1 to 10, which is formed from a device unit (A) according to claim 11 on the one hand and a device unit (B) according to one of claims to claims 12 to 14 on the other hand, whose external terminals (P) are coupled together , 16. Arrangement according to claim 5, wherein in each case one end of a line is connected to the external claims, which connects the two units together.