DE102013114135A1 - Electronic circuit for generating an ASK signal and measuring system - Google Patents

Abstract

The invention relates to an electronic circuit (1) for generating an ASK signal, wherein the ASK signal comprises at least one data signal (data), wherein the data signal (data) reproduces the data to be transmitted, between a first page having a first interface ( 23), and a second side having a second interface (24) corresponding to the first interface (23), wherein the first interface (23) and the second interface (24) are configured to transmit the data and energy, and wherein First interface 23 () and the second interface (24) are designed as galvanically isolated, in particular as inductive, interfaces, wherein the circuit (1) comprises at least: - a carrier source (3) for generating a carrier signal, - a supply voltage (VCC) for powering the circuit (1), - a load circuit (2) for converting the data signal (data) into a useful signal, and - a feed unit (4) for combining ② of the desired signal with the carrier signal to the ASK signal having an amplitude, wherein the useful signal determines the amplitude of the ASK signal, characterized in that the load circuit (2) is connected to the supply voltage (VCC). The invention further relates to a measuring system (20) comprising such an electronic circuit (1).

Description

The invention relates to an electronic circuit for generating an ASK signal. The invention further relates to a measuring system comprising such an electronic circuit.

In process automation, a measuring system usually consists of a higher-level unit, for example a transmitter (also called a transmitter), and a consumer, for example a sensor. Frequently, data is transmitted in the form of a data signal and additional energy. Data becomes bidirectional, and energy is typically transmitted unidirectionally from transmitter to sensor. Alternatively, the parent unit is designed as a control system and the sensor is connected directly to the control system.

The data to be transmitted must be converted into a suitable format for transmission. For this purpose, a so-called carrier signal is changed by the data signal. This process is called modulation. The opposite process, ie the filtering out of a data signal from a carrier signal, is called demodulation.

Frequently, the data is transmitted in digital form. The binary transmission of digital signals is in the simplest case in that a two-level square wave signal is used. In this case, it is possible to switch between two amplitudes, frequencies or phases. In the transmission of digital signals is spoken instead of modulation of keying, so for example, amplitude shift keying (ASK). The present invention deals with this type of modulation.

Such forms of data transmission are suitable for example for inductively coupling connector coupling with at least one primary and secondary coil, as sold by the applicant under the name "Memosens". In addition to data, energy is also transmitted to the sensor via the inductive interfaces.

With amplitude keying the modulation is often achieved by a load modulation, 1 shows such a circuit 1.StdT. In this case - controlled by the data by means of a switching means T - an impedance, usually a resistor R to the circuit 1.StdT switched. If the resistor R is switched on, the power consumption increases significantly, because in addition to the actual circuit, the resistor R receives electrical power.

Needless to say, an adequate supply of the sensor must be guaranteed. Especially with the addressed data and Energieübertragungsart using inductive interfaces, this can require a lot of effort, especially in two-wire connections and / or under Ex-conditions.

The invention has for its object to reduce the power consumption of a circuit in the amplitude modulation, in particular by means of load modulation.

The object is achieved by an electronic circuit for generating an ASK signal, wherein the ASK signal comprises at least one data signal, wherein the data signal reproduces the data to be transmitted; between a first page having a first interface, and a second page having a second interface corresponding to the first interface, wherein the first interface and the second interface are configured to transmit the data and energy, and wherein the first interface and the second interface are designed as galvanically isolated, in particular as inductive, interfaces, wherein the circuit comprises at least: a carrier source for generating a carrier signal; a supply voltage for powering the circuit; a load circuit for converting the data signal into a payload signal; and a supply unit for combining the useful signal with the carrier signal to the ASK signal with an amplitude, wherein the useful signal determines the amplitude of the ASK signal. The circuit is characterized in that the load circuit is connected to the supply voltage.

An additional power consumption is thus avoided and it can - compared to the above-described prior art - energy saved.

In a first advantageous variant, the load circuit is configured with at least one switching means and at least one switchable by the switching means impedance and the data signal indicates the switching of the switching means, and the impedance comprises a first terminal and a second terminal, wherein the first terminal of the impedance with the supply unit is connected.

In a second advantageous variant, the load circuit with at least one switching means and at least one impedance switchable by the switching means and the data signal indicates the switching of the switching means, and the impedance comprises a first terminal and a second terminal, wherein the first terminal of the impedance is connected to the first interface.

In a third advantageous variant, the load circuit is configured with at least one switching means and at least one switchable by the switching means impedance and the data signal indicates the switching of the switching means, and the impedance comprises a first terminal and a second terminal, wherein the first terminal of the impedance with connected to the second interface.

The circuit thus basically allows at least three variants of the connection of the load. The common basic principle is that the load is switched to the supply voltage.

In a preferred embodiment, the switching means is a bipolar transistor, in particular a pnp transistor, having a base terminal, a collector terminal and an emitter terminal, wherein the emitter terminal is connected to the second terminal of the impedance, wherein the collector terminal is connected to the supply voltage, and wherein the base terminal, the data signal is supplied.

As an advantageous development, a second switching means is provided, wherein the second switching means is a bipolar transistor, in particular an npn transistor, with a base terminal, a collector terminal and an emitter terminal, wherein the collector terminal of the second Transistor is connected to the base terminal of the first transistor, wherein the emitter terminal of the second transistor via at least a second impedance, in particular a resistor, is connected to ground, and wherein the base terminal of the second transistor, the data signal is supplied. It can thus be achieved a higher turn-on speed.

So that a higher turn-off speed of the first switching means can be achieved, an accelerator circuit is provided, wherein the accelerator circuit comprises at least one further switching means, wherein the further switching means is a bipolar transistor, in particular a pnp transistor, with a base terminal, a collector Terminal and an emitter terminal, wherein the emitter terminal is connected to the second terminal of the impedance, wherein the collector terminal is connected to the base terminal of the first transistor, and wherein the base terminal, the data signal is supplied inverted ,

As an advantageous development, the accelerator circuit comprises a second further switching means, wherein the second further switching means is a bipolar transistor, in particular an npn transistor, with a base terminal, a collector terminal and an emitter terminal, wherein the collector Connection of the second further transistor is connected to the base terminal of the first further transistor, wherein the emitter terminal of the second further transistor via at least a second further impedance, in particular a resistor, connected to ground, and wherein the base terminal of the second further transistor, the data signal is supplied inverted. Thus, a higher turn-on speed of the accelerator circuit can be achieved.

As an alternative to a bipolar transistor, the switching means is advantageously a field-effect transistor, in particular a MOSFET, in particular an n-channel MOSFET, with a gate terminal, a drain terminal and a source terminal, wherein the drain terminal with the second terminal of the impedance is connected via a diode, wherein the source terminal is connected to the supply voltage, and wherein the gate terminal, the data signal is supplied via a gate capacitor.

In a preferred embodiment, the gate terminal is connected to the supply voltage at least via a diode.

In an advantageous embodiment, the feed unit is a resonator circuit. The resonator circuit comprises at least one externally excited resonant circuit, wherein the resonant circuit is excited by the carrier signal to oscillate. The externally excited resonant circuit is in particular a series resonant circuit, with at least one first inductance and one capacitor, wherein the first inductance corresponds to the first interface; and a carrier switching means, in particular a field effect transistor, in particular a MOSFET, having a gate terminal, a drain terminal and a source terminal. The capacitor is configured to be split as a first capacitor and a second capacitor, and a switching node connects the first capacitor to the second capacitor, wherein the first capacitor is connected to ground, wherein the second capacitor switches the switching node to ground at least via the first inductance. At least one second inductance connects the switching node to the supply voltage, wherein the drain terminal is connected to the switching node, wherein the useful signal is supplied to the switching node, and wherein the gate terminal, the carrier signal is supplied.

The object is further achieved by a measuring device comprising an electronic circuit described above.

In one development, the measuring device comprises a higher-level unit, in particular a transmitter, and a consumer, in particular a sensor, wherein the higher-level unit with the consumer via the first interface and the second interface, wherein the superordinate unit corresponds to the first side, and wherein the consumer corresponds to the second side.

The invention will be explained in more detail with reference to the following figures. Show it

1 a symbolic representation of a circuit of the prior art,

2 an inventive measuring system,

3a a symbolic representation of the circuit according to the invention,

3b a symbolic representation of the circuit according to the invention in a first embodiment,

3c a symbolic representation of the circuit according to the invention in a second embodiment,

4a a first embodiment of the circuit according to the invention,

4b a variant of the first embodiment of the circuit according to the invention, and

5 a second embodiment of the circuit according to the invention

In the figures, the same features are identified by the same reference numerals.

First, it is intended to indicate a measuring device according to the invention 20 be received in which the inventive electronic circuit 1 can be applied. This is in 2 shown. Via an interface 24 communicates a consumer, such as a sensor 22 with a higher-level unit, such as directly with a control system or with a transmitter 21 , Without limitation, it should be assumed in the following that the sensor to a transmitter 21 connected. At the transmitter 21 is a cable 25 provided, at the other end to the first interface 24 complementary interface 23 is provided. The interfaces 23 . 24 are designed as galvanically isolated, in particular as inductive interfaces which can be coupled to one another by means of a mechanical plug connection. About the interfaces 23 . 24 be data (bidirectional) and energy (unidirectional, ie from transmitter 21 to the sensor 22 ) Posted.

The transmission of the data takes place in digital form. In the example, the binary transmission takes place in that a two-level square-wave signal is used. It is switched between two amplitudes. The signal to be transmitted is thus an amplitude modulated, as mentioned in digital signals then one speaks of an amplitude shift or English amplitude shift keying, abbreviated ASK. The signal to be transmitted is therefore an ASK signal.

The measuring device 20 is mainly used in process automation. At the sensor 22 it is therefore about a pH, redox potential, also ISFET, temperature, conductivity, pressure, oxygen, in particular dissolved oxygen, or carbon dioxide sensor; an ion-selective sensor; an optical sensor, in particular a turbidity sensor, a sensor for optically determining the oxygen concentration, or a sensor for determining the number of cells and cell structures; a sensor for monitoring certain organic or metallic compounds; a sensor for determining a concentration of a chemical substance, for example a particular element or a particular compound; or a biosensor, eg a glucose sensor.

The electronic circuit according to the invention 1 is in a first embodiment in the transmitter 21 , but preferably in the sensor-side end of the cable 25 , Basically, the circuit 1 also in the sensor 22 be used; below, however, unless otherwise stated, it shall be assumed that the circuit 1 is applied on the transmitter side.

The circuit 1 in its entirety has the reference number 1 and is symbolic in 3a shown. Compared with the prior art ( 1 ) is the load circuit 2 no longer switched to ground, but against the supply voltage VCC. Thus, the load current flows in the modulation of the load node N via the resistor R and then serves to power the circuit 1 , The additional power consumption (when switching on the load) can thus be reduced compared to the state of the art. Experiments showed a reduced power consumption of up to 50%. With the (unspecified in this figure) diode can be ensured that no load current flows out of the circuit.

The supply voltage VCC is approximately directly from the parent unit, so in this case from the transmitter 21 made available.

The carrier source 3 provides a high frequency carrier signal. The carrier source 3 is about the digital output of a microcontroller (not shown, such as in the transmitter 21 ). The carrier source 3 is connected to the load node N. On this carrier signal, the data signal data is modulated.

Next is a feeder unit 4 connected to the load node N. The first interface 23 is as part of the feeder unit 4 realized, in particular, is the first interface 23 as already mentioned realized as inductance L. The feeder unit 4 leads the load circuit 2 - And thus the data signal - with the carrier source 3 - And thus the carrier signal - at the load node N together. The feeder unit 4 is designed as a resonator circuit. The resonator circuit is a third-excited resonant circuit, wherein the resonant circuit is excited by the carrier signal to oscillate.

The resonator circuit in the example in 3a is designed as a series resonant circuit with a capacity and the already mentioned inductance L. The capacity is realized as a shared capacitance with the capacitors CT1 and CT2. The capacitance CT1 from the load node N is directly connected to ground. The capacitance CT2 connects the inductance L to ground. Further embodiments, such as with additional resistance (cf. 4 and 5 ) are conceivable.

The load node N is connected to the supply voltage via a further inductance LVCC. This results in a vibratory system with the components LVCC, L, CT1, CT2 and the carrier source 3 , In this or similar form, one often speaks of a class E amplifier.

Parallel to the inductance LVCC is the load circuit 2 at. The load circuit 2 is realized as a resistor R with a switching means T. The switching means T can be switched by the data data. Thus, the data signal is modulated onto the carrier signal.

Basically, there are various possibilities to switch on the load R. In 3a this is realized at the switching node N, ie between the shared capacitance CT1 and CT2. In a variant, the load R but also directly to the first inductance (see 3b ) are shot. In a third variant, the load is connected to the second inductance, ie to the second interface 24 , compare to this 3c , In this latter variant are at least parts of the circuit 1 on the side of the sensor 22 , In particular, the load circuit 2 (see below) and / or the accelerator circuit 3 (see below) are then placed on the sensor side. In this case, the supply voltage VCC is not directly from the transmitter 21 but is delivered through the interfaces 23 . 24 , possibly via certain additional circuits such as rectifiers, etc., transported to the sensor side and made available to the circuit.

4a shows a first concrete realization of the electronic circuit 1 ,

The load circuit 2 In this example, it consists essentially of the load R, the transistor T1, the transistor T2, the resistor R1 and the capacitor C1.

The load R represents a resistance, but in general an impedance is meant. The transistor T1 is designed as a bipolar transistor, more precisely as a pnp transistor. The transistor T2 is configured as a bipolar transistor, more precisely as an NPN transistor.

The emitter terminal of the transistor T1 is connected to the load R. The collector terminal of the transistor T1 is connected to the supply voltage VCC. The base terminal of the transistor T1 is connected to the collector terminal of the transistor T2. The emitter terminal of the transistor T2 is connected to ground via the resistor R1 and the parallel capacitance C1. The resistor R1 serves to set a corresponding base current of the transistor T2. The capacitor C1 accelerates the turn-on phase of the turn-on of the transistor T2 and thus also of the transistor T1. About the base terminal of the transistor T2 data, ie the data signal data, supplied. The voltage level of the data signal data is either 0 V or VCC, ie the data signal has the same voltage level as the supply voltage. Basically, the circuit works 1 also with other voltage levels, the components or their values would have to be adjusted accordingly. If, for example, the levels are inverted in their logical interpretation, a corresponding inverter must be connected upstream.

The already mentioned diode for preventing the backflow of the load current into the circuit is not necessary in this variant with bipolar transistor because of the inherent diode of the transistor.

A realization without the transistor T2 is conceivable, then the data signal is fed directly to the base terminal of the transistor T1. However, a circuit with transistor T2 has the advantage that a higher turn-on speed can be achieved. This is necessary so that the switching edges of the modulated signal are steep enough and thus recognized as a level change.

In the case of a "digital 1", that is to say a "high" of the data signal, the transistor T2 switches and in time with the high-frequency carrier signal of the carrier source 3 turns on the transistor T1, voltage drops across the load R and a current flows through the load R. This current flows into the circuit 1 and serves to supply the circuit 1 , This additional power consumption in a modulation can be the total power consumption of the circuit 1 reduce.

4b shows a variant of the circuit 1 out 4a , For an even higher turn-off speed of the transistor T1 can be achieved, is an accelerator circuit 5 intended. The accelerator circuit 5 consists essentially of transistor TB1, the transistor TB2, the resistor R2 and the capacitor C2 The transistor TB1 is designed as a bipolar transistor, more precisely as a PNP transistor. The transistor TB2 is designed as a bipolar transistor, more precisely as an NPN transistor.

The emitter terminal of the transistor TB1 is connected to the load R. The collector terminal of the transistor TB1 is connected to the base terminal of the transistor T1. The base terminal of the transistor TB1 is connected to the collector terminal of the transistor TB2. The emitter terminal of the transistor TB2 is grounded through the resistor R2 and the parallel capacitor C2. The resistor R2 is for setting a corresponding base current of the transistor TB2. The capacitance C2 accelerates the turn-on phase of the turn-on of the transistor TB2 and thus also of the transistor TB. About the base terminal of the transistor TB2 data, ie the data signal, are supplied inversely.

5 shows a further embodiment of the load circuit 2 , Here is the load circuit 2 realized with a unipolar transistor T1. The transistor T1 is a self-blocking NMOS transistor. Alternatives as PMOS or in a self-conducting design are conceivable with small modifications of the circuit.

The source terminal of the transistor T1 is connected to the supply voltage VCC. The drain terminal of the transistor T1 is connected to the load node N via a diode D1 (cathode points in the direction of the drain terminal) and via the load R. The diode D1 prevents unwanted current flow of VCC via the body diode of T1 and R to the load node N. Diode D2, capacitor C3 and resistor R3 form a bootstrap circuit for driving the gate terminal of the transistor T1. The data signal changes between 0 V and VCC. Because of the bootstrap effect, the voltage at the gate of T1 then changes between 0V + VCC and VCC + VCC.

LIST OF REFERENCE NUMBERS

1

 Electronic switch

2

 Powershift

3

 carrier source

4

 feed

5

 accelerator circuit

20

 measuring system

21

 transmitter

22

 sensor

23

 interface

24

 interface

25

 electric wire

data

 data signal

D1

 diode

D2

 diode

L

 inductance

N

 Last node

R

 load

R1

 resistance

R2

 resistance

R3

 resistance

R4

 resistance

C1

 capacity

C2

 capacity

C3

 capacity

CT1

 capacity

CT2

 capacity

T1

 switching means

T2

 switching means

TB1

 switching means

TB2

 switching means

VCC

 supply voltage

Claims (13)

Electronic switch ( 1 ) for generating an ASK signal, wherein the ASK signal comprises at least one data signal (data), wherein the data signal (data) reproduces the data to be transmitted, between a first page with a first interface ( 23 ), and a second page with a, to the first interface ( 23 ), second interface ( 24 ), the first interface ( 23 ) and the second interface ( 24 ) for transmitting the data and energy, and wherein the first interface 23 () and the second interface ( 24 ) are designed as galvanically isolated, in particular as inductive, interfaces, wherein the circuit ( 1 ) at least comprises: - a carrier source ( 3 ) for generating a carrier signal, - a supply voltage (VCC) for supplying the circuit ( 1 ) with energy, - a load circuit ( 2 ) for converting the data signal (data) into a useful signal, and A feed unit ( 4 ) for combining the useful signal with the carrier signal to the ASK signal with an amplitude, wherein the useful signal determines the amplitude of the ASK signal, characterized in that the load circuit ( 2 ) is connected to the supply voltage (VCC). Electronic switch ( 1 ) according to claim 1, wherein the load circuit ( 2 ) is configured with at least one switching means (T1) and at least one switchable by the switching means (T1) impedance (R) and the data signal (data), the switching of the switching means (T1) pretending, and wherein the impedance (R) a first terminal and a second terminal, wherein the first terminal of the impedance (R) with the feed unit ( 4 ) connected is. Electronic switch ( 1 ) according to claim 1, wherein the load circuit ( 2 ) is configured with at least one switching means (T1) and at least one switchable by the switching means (T1) impedance (R) and the data signal (data), the switching of the switching means (T1) pretending, and wherein the impedance (R) a first terminal and a second terminal, wherein the first terminal of the impedance (R) is connected to the first interface ( 23 ) connected is. Electronic switch ( 1 ) according to claim 1, wherein the load circuit ( 2 ) is configured with at least one switching means (T1) and at least one switchable by the switching means (T1) impedance (R) and the data signal, the switching of the switching means (T1) specifies, and wherein the impedance (R) a first terminal and a second terminal wherein the first terminal of the impedance (R) is connected to the second interface ( 24 ) connected is. Electronic switch ( 1 ) according to at least one of claims 2 to 4, wherein the switching means (T1) is a bipolar transistor, in particular a pnp transistor, having a base terminal, a collector terminal and an emitter terminal, wherein the emitter terminal is connected to the second terminal of the impedance (R), wherein the collector terminal is connected to the supply voltage (VCC), and wherein the base terminal, the data signal (data) is supplied. Electronic switch ( 1 ) according to claim 5, wherein a second switching means (T2) is provided, wherein the second switching means (T2) is a bipolar transistor, in particular an npn transistor, with a base terminal, a collector terminal and an emitter terminal is, wherein the collector terminal of the second transistor is connected to the base terminal of the first transistor, wherein the emitter terminal of the second transistor via at least one second impedance (R1), in particular a resistor, connected to ground, and wherein the Base terminal of the second transistor, the data signal (data) is supplied. Electronic switch ( 1 ) according to claim 5 or 6, wherein an accelerator circuit ( 5 ), wherein the accelerator circuit ( 5 ) comprises at least one further switching means (TB1), wherein the further switching means (TB1) is a bipolar transistor, in particular a pnp transistor, having a base terminal, a collector terminal and an emitter terminal, wherein the emitter Terminal is connected to the second terminal of the impedance (R), wherein the collector terminal is connected to the base terminal of the first transistor, and wherein the base terminal, the data signal (data) are supplied inverted. Electronic switch ( 1 ) according to claim 7, wherein the accelerator circuit ( 5 ) comprises a second further switching means (TB2), wherein the second further switching means (TB2) is a bipolar transistor, in particular an npn transistor, having a base terminal, a collector terminal and an emitter terminal, wherein the Collector terminal of the second further transistor is connected to the base terminal of the first further transistor, wherein the emitter terminal of the second further transistor via at least one second further impedance (R2), in particular a resistor connected to ground, and wherein the Base terminal of the second further transistor, the data signal (data) is supplied inverted. Electronic switch 1 () according to at least one of claims 2 to 4, wherein the switching means (T1) is a field-effect transistor, in particular a MOSFET, in particular an n-channel MOSFET, with a gate terminal, a drain terminal and a source terminal wherein the drain terminal is connected to the second terminal of the impedance (R) via a diode (D1), wherein the source terminal is connected to the supply voltage (VCC), and wherein the gate terminal, the data signal (data) via a gate capacitor (C3) is supplied. Electronic ( 1 A circuit according to claim 9, wherein the gate terminal is connected to the supply voltage (VCC) at least via a diode (D2). Electronic switch ( 1 ) according to at least one of claims 1 to 10, wherein it is in the feed unit ( 4 ) is a resonator circuit and at least - a third-excited resonant circuit, in particular a series resonant circuit, with at least a first inductance (L) and a capacitor, wherein the first inductance (L) of the first interface ( 23 ), and - a carrier switching means ( 3 ), in particular a field-effect transistor, in particular a MOSFET, having a gate terminal, a drain terminal and a source terminal, wherein the capacitor is designed divided as a first capacitor (CT1) and second capacitor (CT2), and a switching node (N) connects the first capacitor (CT1) to the second capacitor (CT2), the first capacitor (CT1) being connected to ground, the second capacitor (CT2) transmitting the switching node (N) at least via the first inductance (L) switches to ground, wherein at least one second inductance (LVCC) connects the switching node (N) to the supply voltage (VCC), wherein the drain terminal is connected to the switching node (N), wherein the useful signal is supplied to the switching node, and wherein the Gate terminal, the carrier signal is supplied. Measuring device ( 20 ) comprising an electronic circuit ( 1 ) according to at least one of claims 1 to 11. Measuring device ( 20 ) according to claim 12, wherein the measuring device ( 20 ) a parent unit ( 21 ), in particular a transmitter, and a consumer ( 22 ), in particular a sensor, wherein the higher-order unit ( 21 ) with the consumer ( 22 ) via the first interface ( 23 ) and the second interface ( 24 ), the parent unit ( 21 ) corresponds to the first page, and where the consumer ( 22 ) corresponds to the second page.

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