Method for transmitting analog and digital information while transmitting energy

Abstract

The invention relates to a method for transmitting analog and digital information while transmitting energy between a power transmitter (10) and a power receiver (12) which is galvanically isolated from the power transmitter, having the following steps: a) providing the analog (22a) and digital (24a) information to be transmitted; b) defining the number n.sub.AD of possible values AD.sub.i, i=1 to n.sub.AD which are possible when digitizing the analog information and defining the value range of the values AD.sub.i; c) assigning a digital value D.sub.x (in binary notation) to the digital information; d) defining a minimum number of events n.sub.min to be transmitted; e) determining a maximum number of events n.sub.max to be transmitted; f) defining a first set of values n.sub.low defined by: n.sub.low (AD.sub.i)=n.sub.min+f1(AD.sub.i), i=1 to n.sub.AD; g) defining a second set of values n.sub.low defined by: n.sub.high(ADi)=n.sub.maxf2(AD.sub.i), i=1 to n.sub.AD; h) digitizing the analog information in order to obtain a digital analog value AD.sub.x; i) determining a number of events n.sub.low(ADx)=n.sub.min+f1(AD.sub.x) for the respective digital value D.sub.x bit to be transmitted if the current digital value D.sub.x bit to be transmitted is a 0; and defining a number of events n.sub.high(AD.sub.x)=n.sub.maxf2(AD.sub.x) for the respective digital value D.sub.x bit to be transmitted if the current digital value D.sub.x bit to be transmitted is a 1 or vice versa; and j) transmitting a signal which correlates at least to the number of events determined in step i). The invention further relates to a corresponding device for carrying out the method.

Claims

1. A method for transmitting analog and digital information while transmitting energy between a power transmitter and a power receiver galvanically isolated from said power transmitter, the method comprising the following steps: a) providing analog information and digital information to be transmitted; b) setting a number nAD of possible values ADi, i=1 to nAD, that are possible when digitizing the analog information, and a value range of the values ADi; c) assigning a digital value Dx to the digital information; d) setting a minimum event number nmin to be transmitted; e) setting a maximum event number nmax to be transmitted; f) setting a first image nlow defined by:
nlow(ADi)=nmin+f1(ADi), i=1 to nAD; g) setting a second image nhigh defined by:
nhigh(ADi)=nmaxf2(ADi), i=1 to nAD; h) digitizing the analog information for obtaining a digitized analog value ADx; i) determining an event number
nlow(ADx)=nmin+f1(ADx) for the bit of the digital value Dx to be transmitted in each case if the current bit of the digital value Dx to be transmitted is a logical 0; and determining an event number
nhigh(ADx)=nmaxf2(ADx) for the bit of the digital value Dx to be transmitted in each case if the current bit of the digital value Dx to be transmitted is a logical 1, or vice versa; and j) transmitting a signal that is correlated at least to the event number determined in step i).

2. The method as claimed in of claim 1, wherein a signal that is correlated to the serial sequence of the event number determined in step i) for each bit of the digital value D.sub.x is transmitted in step j).

3. The method of claim 1, wherein a signal is transmitted for the bit of the digital value to be transmitted, said signal being correlated to both a number of events according to the event number n.sub.low determined in step i) and a number of events according to the event number n.sub.high determined in step i), wherein a logical 1 of the bit of the digital value D.sub.x to be transmitted in each case is represented by a sequence n.sub.high-n.sub.low and a logical 0 is represented by a sequence n.sub.low-n.sub.high of the amplitude of the signal, or vice versa.

4. The method of claim 1, wherein in step j), the event number determined in step i) is transmitted in the form of a certain number of predeterminable events.

5. The method of claim 4, wherein between the individual bits to be transmitted of the digital value D.sub.x in the signal, a signal differing therefrom is inserted.

6. The method of claim 5, wherein the signal of the individual bits to be transmitted comprises a sequence of pulses, with the signal differing therefrom representing a pause; or in that the signal of the individual bits to be transmitted comprises a predeterminable time duration of a zero signal, with the signal differing therefrom representing a pulse.

7. The method of claim 4, wherein an amplitude change is undertaken in the signal between a current bit of the digital value D.sub.x to be transmitted and a next bit.

8. The method of claim 1, wherein the event number in the form of a signal, determined in step i), with a period duration depending on the event number determined in step i) is transmitted in step j).

9. The method of claim 8, wherein, for the purposes of producing the period duration, an excitation of the transmission with a predeterminable function is activated for a time duration
t.sub.on=n.sub.low*t*D or t.sub.on=n.sub.high*t*D and deactivated for a time duration
t.sub.off=n.sub.low*t*(1D) or t.sub.off=n.sub.high*t*(1D), where t is a predeterminable time duration and D is a predeterminable duty cycle.

10. The method of claim 9, wherein the time duration t and/or the duty cycle D is varied, in particular modulated, depending on the digitized analog value AD.sub.x to be transmitted.

11. The method of claim 1, wherein the following step is implemented at the receiver of the transmission: k) evaluating the received signal for determining the transmitted analog value and the transmitted digital value.

12. The method of claim 11, wherein the envelope of the received signal, in particular the period duration of the enveloping function, is evaluated in step k).

13. The method of claim 1, wherein f1(ADi) and f2(ADi) are chosen in such a way that the first image and the second image are disjoint.

14. The method of claim 11, wherein f1(ADi) and f2(ADi) are chosen in such a way that the first image and the second image have a common overlap region, wherein a previously created probability function is used in step k) for determining the transmitted analog value and the transmitted digital value for a value in the overlap region.

15. The method of claim 14, wherein said method furthermore comprises the following step: l) creating a statistic for the assignment of values in the overlap range to the first or second image depending on at least one previously transmitted value that is uniquely assignable to the first or the second image.

16. An apparatus comprising: a power transmitter configured to transmit energy and provide analog information to a power receiver galvanically isolated from the power transmitter and configured to receive the energy; a digital source configured to provide digital information related to the power receiver; a microcontroller configured to: set a number n.sub.AD of possible values AD.sub.i, i=1 to n.sub.AD, that are possible when digitizing the analog information and set a value range of the values AD.sub.i, assign a digital value D.sub.x to the digital information; set a minimum event number n.sub.min to be transmitted; set a maximum event number n.sub.max to be transmitted; set a first image n.sub.low defined by: n.sub.low(AD.sub.i)=n.sub.min+f1(AD.sub.i), i=1 to n.sub.AD; set a second image n.sub.high defined by: n.sub.high(AD.sub.i)=n.sub.maxf2(AD.sub.i), i=1 to n.sub.AD; digitize the analog information for obtaining a digitized analog value AD.sub.x; determine an event number n.sub.low(AD.sub.x)=n.sub.min+f1(AD.sub.x) for the bit of the digital value D.sub.x to be transmitted in each case if the current bit of the digital value D.sub.x to be transmitted is a logical 0, and determine an event number n.sub.high(AD.sub.x)=n.sub.maxf2(AD.sub.x) for the bit of the digital value D.sub.x to be transmitted in each case if the current bit of the digital value D.sub.x to be transmitted is a logical 1, or vice versa; a data transmitter configured to transmit a signal that is correlated at least to the determined event number; and a data receiver configured to receive the signal and communicate with the power transmitter.

Description

(1) Exemplary embodiments of the present invention are now described in more detail below with reference to the attached drawings. In the drawings:

(2) FIG. 1 shows a schematic illustration relating to the power and signal flow in a system for transmitting electrical energy between a power transmitter and a power receiver that is galvanically isolated from said power transmitter;

(3) FIG. 2 shows a schematic illustration of an apparatus according to the invention for parallel transmission of analog and digital data using the method according to the invention;

(4) FIG. 3 shows an example of an event table as used in an embodiment of the method according to the invention;

(5) FIG. 4 shows the event table of FIG. 3 for predetermined values of n.sub.min, n.sub.max, n.sub.AD and AD.sub.min;

(6) FIG. 5 shows a schematic illustration of an exemplary embodiment of an apparatus according to the invention for galvanically isolated energy transmission;

(7) FIG. 6 shows an illustration showing a temporally equidistant distribution of events;

(8) FIG. 7 shows an illustration showing a temporally arbitrary distribution of events;

(9) FIG. 8 shows a schematic illustration relating to a first exemplary embodiment of the method according to the invention;

(10) FIG. 9 shows a schematic illustration relating to a second exemplary embodiment of the method according to the invention;

(11) FIG. 10 shows the temporal sequence of the events to be transmitted in the case of the Manchester code;

(12) FIG. 11 shows a schematic illustration relating to a third exemplary embodiment of the method according to the invention;

(13) FIG. 12 shows a schematic illustration relating to a fourth exemplary embodiment of the method according to the invention;

(14) FIG. 13 shows a schematic illustration relating to a fifth exemplary embodiment of the method according to the invention;

(15) FIG. 14 shows a schematic illustration relating to a sixth exemplary embodiment of the method according to the invention;

(16) FIG. 15 shows a schematic illustration relating to a seventh exemplary embodiment of the method according to the invention; and

(17) FIG. 16 shows a schematic illustration relating to an eighth exemplary embodiment of the method according to the invention.

(18) The same reference signs are used for the same components and components with the same effect.

(19) In a schematic illustration, FIG. 2 shows an exemplary embodiment of an apparatus according to the invention for galvanically isolated energy transmission; see arrow 20 between a power transmitter 10 and a power receiver 12 whichas indicated by the two parallel lines 18are galvanically isolated from one another. Control data 22a produced by the power receiver 12 and status information 24a on the part of the power receiver are supplied to a data transmitter 14. The latter transmits, in parallel fashion, the analog control data 22a in digitized form and the status information 24a by analog-digital event modulationas indicated by the arrow 26to the power transmitter side. The transmitted data are demodulated in a data receiver 16 on the part of the power transmitter and provided as digital status information 24b, on the one hand, and control data 22b provided for the power transmitter 10.

(20) Consequently, the method according to the invention serves for the parallel transmission of a digitized analog variable with a high data rate and a parallel, digital information transmission with a lower data rate. Without the present invention being restricted thereto, the digitized analog variable preferably corresponds to a measurement variable that is needed to close a control loop 28, indicated in FIG. 2, in the following exemplary embodiments. However, this should not mean any restriction to control information. In the shown exemplary embodiments, the digital information with a lower data rate should correspond to status information and likewise be non-restrictive.

(21) In the exemplary embodiments of the present invention shown below, it is irrelevant in respect of the control information transmission of a system for wireless energy transmission whether the digital regulator is implemented on the part of the power transmitter or power receiver. In the first case, the digitized measurement value or the digitized system deviation is transmitted back to the power transmitter 10 by the power receiver 12 and supplied to a digital regulator. In the second case, the system deviation is supplied to a digital regulator already on the power receiver 12 and only the digitized manipulated variable is transmitted back to the power transmitter 10.

(22) Nor should the shown direction of information transmission be limited. Thus, the same method can be used to transmit a status value and a digitized analog value from a power transmitter 10 to a power receiver 12. A half-duplex or full-duplex transmission is also possible, i.e., a method in which transmission is always only carried out in one direction or a method in which transmission can be carried out in both directions.

(23) A discretization and quantization of a controlled variable, such as the output voltage, for example, is always required for the digital feedback control of an analog variable, such as the output voltage of a wireless energy transmission system, for example. In many cases, the analog variable to be controlled is sampled by means of an analog-digital converter (ADC) and converted into digital values for this purpose. Here, a digital value is assigned to each ascertained analog measurement value. The set or number of possible, digitized analog values, which is denoted by n.sub.AD below, is always restricted (quantization). By way of example, in the case of a 12 bit ADC, n.sub.AD is 2.sup.12=4096. The measured, digitized analog value AD.sub.x in this case has a value between 0 and 4095.

(24) It is irrelevant to the method according to the invention whether this digitized analog value is transmitted directly to the power transmitter 10 or whether there still is further processing, for example by a filter or digital regulator, on the part of the power receiver. All that is decisive is that a digitized analog value is transmitted in all cases.

(25) In order to facilitate transmission of the required information as efficiently as possible, the digitized analog value AD.sub.x at the signal transmitter 14 is converted directly to a number of events, which should be transmitted, after defining a minimum event number n.sub.min and a maximum event number n.sub.max. Here,
n.sub.low(AD.sub.x)=n.sub.min+f1(AD.sub.x)
and
n.sub.high(AD.sub.i)=n.sub.maxf2(AD.sub.x)

(26) apply. In the exemplary embodiment below, the functions f1 and f2 are selected to be very simple for the purposes of an easier understanding, and so the following arises:
n.sub.low(AD.sub.x)=n.sub.min+AD.sub.x
and
n.sub.high(AD.sub.x)=n.sub.maxAD.sub.x.

(27) Using these equations, it is possible to determine the general event table illustrated in FIG. 3. Said event table is based on setting a minimum event number n.sub.min, a maximum event number n.sub.max, the number of possible digitized analog values n.sub.AD and the minimum digitized analog value AD.sub.min. The second line defines a first value range n.sub.low(AD.sub.i), which starts at n.sub.min and ends at n.sub.min+AD.sub.max. The third line defines a second value range n.sub.high(AD.sub.i), which starts at n.sub.max and ends at n.sub.maxAD.sub.max.

(28) The minimum and maximum event numbers n.sub.min and n.sub.max can now be chosen in such a way that
n.sub.low(AD.sub.n.sub.AD=AD.sub.max)<n.sub.high(AD.sub.n.sub.AD=AD.sub.max)

(29) applies.

(30) Hence, the first and the second value range are disjoint and, in addition to directly determining the original, digitized analog value from a number n of transmitted results, it is also possible to directly determine whether a value is present in the event window n.sub.low (see FIG. 3, second line) or in the event window n.sub.high (see FIG. 3, third line).

(31) This number n of events is now transmitted immediately by way of any transmission channel. By receiving n.sub.min events, for example, it is known that the digitized analog value AD.sub.min was transmitted in the event window n.sub.low. By contrast, if n.sub.max(AD.sub.min+2) events are captured, for example, the digitized analog value AD.sub.min+2 is transmitted in the event window n.sub.high.

(32) In this way, respectively one event number in the window n.sub.low and one in the window n.sub.high is assigned to each digitized analog value AD.sub.x according to n.sub.low(AD.sub.x) and n.sub.high(AD.sub.x). This additional information can now be used to also transmit digital values in addition to the digitized analog values.

(33) The digitized analog value AD.sub.x is immediately available for the data receiver 16 after receiving the event number n. The digital protocol which may be required for the digital signal transmission using the event windows n.sub.low and n.sub.high should not be part of the notice of invention. Accordingly, two values are available, i.e., one in the event window n.sub.low and one in the event window n.sub.high, which values can be used in very different ways for data transmission purposes.

(34) With reference to FIG. 4, n.sub.AD=8 and the digitized analog values AD.sub.i (i=1 . . . n.sub.AD) should originate from the set 0, 1, 2, . . . 7 in the following example for elucidation purposes. These values should be modulated and transmitted. A minimum event number of n.sub.min=5 and a maximum event number of n.sub.max=24 are defined. Using these, it is possible to create the table illustrated in FIG. 4. From this table, the event numbers n.sub.low(3)=8 and n.sub.high(3)=21 can be read in the case of a digitized analog value AD.sub.x=3, for example.

(35) As an example embodiment of an apparatus according to the invention, FIG. 5 shows an inductive and galvanically isolated energy transmission system. Here, energy, see arrow 20, is transmitted from a power transmitter 10 to a power receiver 12. For the purposes of a feedback control of an exact output voltage U.sub.A, the latter should be captured (analog source), optionally processed and then supplied to a digital regulator. Since the manipulated variable of the energy transmission is situated on the transmission side, the transmission of a digitized analog value from the power receiver 12 to the power transmitter 10 is necessary. Here, the power receiver 12 acts as an analog source; the power transmitter 10 acts as an analog sink. Since the transmission of digital information should also be possible in addition to the feedback control, a digital data source 30 and a digital data receiver 32 are present. The remainder of the structure comprising the capacitors C1, C2 and the inductors L1 and L2 is well known in the art.

(36) The transmission of the digitized analog information AD.sub.x and the digital information D.sub.x is implemented by way of a common transmission channel, such as, e.g., an inductive coupling or an optical coupler (e.g., optocoupler), using the method according to the invention.

(37) It is possible to distinguish between direct and indirect modulation in the method according to the invention:

(38) In the case of direct ADEM, the event numbers n.sub.low(AD.sub.x) and n.sub.high(AD.sub.x) are each transmitted by a countable event, which occurs with a frequency of n.sub.low(AD.sub.x) or n.sub.high(AD.sub.x). In the simplest example of an optical transmission, the shining of a light-emitting diode could be activated and deactivated in a manner corresponding to the event number. The spacing of the events can be known, equidistant, or else arbitrary.

(39) FIG. 6 shows a temporal sequence of events with a predeterminable amplitude A1 in the case of an equidistant distribution of events. If only events are counted in the case of direct ADEM, the amplitude can vary and therefore plays only a subordinate role.

(40) FIG. 7 shows a corresponding representation in the case of an arbitrary distribution of events.

(41) By way of example, if the digitized analog value AD.sub.x=3 should be transmitted and the digital combination 0, 1, 1, 0 should be transmitted at the same time, event packets according to the representation in FIG. 8a can be transmitted in accordance with the events table in FIG. 4. Accordingly, an event number from the value range n.sub.low(AD.sub.i) is chosen for transmitting a digital 0 and an event number from the value range n.sub.high(AD.sub.i) is chosen for transmitting a digital 1. Since, as explained above, a digitized analog value AD.sub.x=3 should be transmitted in the example, eight events E are accordingly transmitted to transmit a digital 0 and 21 events E are accordingly transmitted to transmit a digital 1. A pause P is inserted for distinguishing the events. The transmitted signal, see arrow 26 in FIG. 5, is illustrated in FIG. 8b.

(42) An additional increase in the transmission speed can be realized by virtue of facilitating a distinction of the event packets by measurement. In this case, the pause P is no longer required. By way of example, if an additional modulation of the amplitude (ASK=Amplitude Shift Keying) is facilitated, an event packet change can be determined on the basis of a change in amplitude, with the digitized analog value AD.sub.x still being represented by the number of events.

(43) FIG. 9a shows the events to be transmitted, where an e event is denoted by the amplitude A2 and an E event is denoted by the amplitude A1.

(44) Equidistant sampling of the measurement variable is often very advantageous for digital feedback control purposes. If this is desired, a Manchester code can be used for the digital data transmission. By way of example, if the assumption is made that a logical 1 is described by a high-low change and a logical 0 is described by a low-high change when using equidistant events according to FIG. 6 and if, further, a digitized analog value applies to two event packets in each case, both the digitized analog values and the digital values are available in temporally equidistant form. The sequence as illustrated in abbreviated form in FIG. 10 emerges for the digital value 0, 1, 1, 0.

(45) In this example, a digitized symbol has the constant duration of two pauses [P] and 29 events [n.sub.min+n.sub.max] and, accordingly, it is independent of the digitized analog value. However, depending on the analog value, the transmission speed of analog and digital value is halved in comparison with the application example illustrated in FIG. 8 since a logical state is always represented by combination of low and high.

(46) However, for elucidation purposes, the transmission of the digital information 0, 1, 1, 0 should be specified with an increasing digitized analog value 3, 4, 5, 6. The sequence illustrated in FIG. 11a follows from the table according to FIG. 4. The associated temporal event modulation is shown in FIG. 11b.

(47) The duration of a digital symbol is constant with the sum of 29E and 2P.

(48) A further advantage of the Manchester code consists of a DC component freedom being facilitated depending on the form of the events; this is particularly advantageous in the case of inductive transmission methods, for example. At the same time, a timing recovery is possible.

(49) Here too, an additional increase in the transmission speed in accordance with the exemplary embodiment by means of ASK illustrated in conjunction with FIG. 9 is possible.

(50) It is also possible that even though use is made of a digital Manchester code, the analog value is adapted in each period packet. As a consequence of this, the number of digitized analog values doubles but the equidistant property only remains approximately present for the digital value in the steady-state condition of a feedback control. Since the transmission according to the Manchester code is implemented in terms of signal changes (low/high or high/low), it may be possible, for example, for a different analog value to be present when transmitting low digital information than when transmitting the high digital information. Hence, a signal length overall that is not constant would arise.

(51) Indirect ADEM:

(52) In the case of indirect ADEM, any signal with a controllable period duration can be used to transmit a digitized analog value. What is decisive is that an evaluation apparatus is present, the latter ascertaining the number of events that have occurred or could occur during the period duration T. The last-mentioned case becomes clearer with reference to FIG. 15, bottom. Here, the number of possible events are counted between the actually transmitted events.

(53) In general, a type of frequency modulation can be used for analog and parallel digital data transmission in the case of indirect ADEM, for example if the transmission channel is excited with any periodic signal form of the frequency 1/T(n) at every event package.

(54) In this context, FIG. 12 shows the temporal sequence of the transmission of the signal, known from FIG. 11a, by means of a sinusoidal, Manchester-encoded indirect ADEM.

(55) Particularly preferably, the excitation of the transmission channel per event packet can be activated for a time duration t.sub.on(n)=n*t*D and deactivated for a time duration t.sub.off(n)=n*t*(1D). The time duration t and the duty cycle D can be chosen as desired in this case; they can even likewise be modulated for extending the transmission options.

(56) In this context, FIG. 13 shows the transmission of the sequence of FIG. 11a by means of a rectangular, Manchester-encoded, indirect ADEM, where the duty cycle D was chosen to be 0.5.

(57) By way of an additional modulation of the duty cycle D, it is possible, for example, to increase the number of transmittable, digitized analog values or of the digital values as desired. Thus, for example, with n.sub.AD=8 and D=[0.3; 0.7], 16 signal forms could be produced and transmitted instead of eight, which can be used, for example, for doubling the number of analog values according to n.sub.AD.sub.eff=2*n.sub.AD. Moreover, D=f(AD.sub.x) could also hold true or be based on a third signal.

(58) In this context, FIG. 14 shows a rectangular, Manchester-encoded indirect ADEM with additional pulse width modulation by providing two values, specifically 0.3 and 0.7, for the duty ratio D for the example illustrated in FIG. 11a.

(59) The implementation of the sequence illustrated in FIG. 11a can be inverted according to FIG. 11b. By way of example, if a circuitry-based evaluation apparatus is present, which measures the duration between any two occurrences (this corresponds to the pauses in the specified example embodiments) and which determines the number of possible events between the occurrences, a parallel transmission of analog and digital values is likewise possible. In comparison with the illustration of FIG. 11b, there is a change in the polarity which may be advantageous for the electrical efficiency and the electromagnetic compatibility; in this respect, see FIG. 15.

(60) This form of modulation has advantageous effects on the electrical efficiency and on the electromagnetic compatibility because the excitation of the channel is very low on average. A similar effect can be obtained if the exemplary embodiment illustrated in FIGS. 13 and 14 is operated with a low value for the duty cycle D.

(61) If the direct determination of the number of events is not possible on account of an inertia of the transmission channel, an enveloping event function is preferably detected. By way of example, if the physical channel is excited in some way for the time t.sub.on(n) and not excited immediately following this for the time t.sub.off(n), it is possible to ascertain the period duration of the enveloping function and determine both the transmitted analog value and the digital value.

(62) In this context, FIG. 16 shows, for the example of FIG. 8a, that the transmitted information is contained in the envelope of a signal transmission.

(63) Here, the type of excitation is arbitrary. Thus, the channel can be excited with a constant value or frequency during the time t.sub.on(n), for example. Alternatively, instead of being at rest, the channel could also be excited during the second phase t.sub.off(n) in a fashion that is different from the first phase.