EP1374365A2

EP1374365A2 - Sensor for connection to a bus and method for supplying energy to a sensor connected to a bus

Info

Publication number: EP1374365A2
Application number: EP02729809A
Authority: EP
Inventors: Werner Nitschke; Klaus-Dieter Meier; Knut Balzer; Ewald Mauritz; Heiko Buehring; Hans Bogenrieder; Bernd Pfaffeneder; Holger Wulff
Original assignee: Robert Bosch GmbH; Conti Temic Microelectronic GmbH; Siemens AG
Current assignee: Robert Bosch GmbH; Conti Temic Microelectronic GmbH; Continental Automotive GmbH
Priority date: 2001-03-29
Filing date: 2002-03-21
Publication date: 2004-01-02
Also published as: US7176587B2; US20040172205A1; WO2002080130A2; WO2002080130A3; JP4129184B2; DE10115411A1; JP2005502935A

Abstract

The invention relates to a sensor for connection to a bus and to a method for supplying energy to a sensor that is connected to a bus, which is designed to minimize energy consumption of a sensor connected to a bus. To this end, energy for a sensor is charged in an energy accumulator during a first period and discharged during a second period, that is, during the measuring time, with the purpose of supplying energy to the sensor element. A capacitor is used as energy accumulator and charging of the capacitor is monitored by the voltage monitoring device.

Description

Sensor for connection to a bus and method for

Power supply for a sensor connected to a bus

State of the art

The invention is based on a sensor for connection to a bus or a method for supplying energy to a sensor connected to a bus according to the type of the independent claims.

It is already known from the patent DE 38 11 217

Connect sensors for a restraint system to a bus.

Advantages of the invention

The sensor according to the invention for connection to a bus or the method according to the invention for supplying energy to a sensor connected to a bus with the features of the independent claims has the advantage that the energy consumption of sensors connected to the bus is limited to a minimum. The sensors then achieve characteristic electrical data of conventional ignition means, ie the operating energy of the sensors is not greater than that of a ignition agent. This allows more sensors to be connected to a bus. This is achieved by the so-called snapshot measurement is carried out. This means that the sensors and in particular slow sensors with a sampling rate of a few Hertz only carry out a few measuring cycles and are in a sleep mode most of the time, that is to say they require little or no current. The measurement result is then stored in a logic module and, if necessary, transmitted via the bus. The charging of the energy store for the sensor element of the sensor is monitored by an energy monitor in order to recognize when the energy store is charged to such an extent that the

Sensor element can be supplied with energy by the energy store for at least one measurement. In particular, the lower energy consumption of the sensors makes it possible to design a bus with more than seven sensors, for example, and the simultaneous operation of ignition means.

The measures and developments listed in the dependent claims permit advantageous improvements of the sensor specified in the independent patent claims for connection to a bus or method for energy supply of a sensor connected to a bus.

It is particularly advantageous that there is a further energy store which supplies the logic module with energy in an active bus phase, that is to say when communication is taking place via the bus, since the logic module cannot be supplied via the bus during this time. This energy store is charged during the inactive bus phase.

In addition, it is advantageous that the energy monitoring is assigned to the logic module and is therefore additionally designed as voltage monitoring. In this way, the voltage monitor is also continuously supplied with electrical energy at the same time as the logic module, so that the energy store for the sensor element is continuously monitored in relation to the electrical energy stored in it.

It is also advantageous that the energy stores are designed as capacitors that can be made small and compact.

Finally, it is also advantageous that the logic module then stores the signals from the sensor element and later sends them via the bus. This enables data to be sent via the bus either on request by a bus master or automatically by a sensor.

drawing

Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the description below. FIG. 1 shows a circuit diagram of the sensor according to the invention, FIG. 2 shows a bus system with a connected sensor according to the invention and FIG. 3 shows a flow diagram of the method according to the invention.

description

Due to the increasing number of restraint devices and sensors in a motor vehicle, it is advantageous to use a bus to ignite and sensors for such

To connect restraint systems with each other to reduce cable expenditure. In some applications it is desirable to be able to operate so-called slow sensors with a sampling rate of a few Hertz and ignition means together on one bus. An example of this is the operation of Belt buckle switches and the occupant weight sensor as well as the belt tensioner in the motor vehicle on a bus.

In a typical bus system for restraint systems, a control device is used as the bus master, while sensors and ignition devices are operated as slaves. Upon request, the slaves send their data to the master in specified time periods. A trigger algorithm is then calculated in the control unit with the sensor values, which possibly leads to a trigger decision, which is then transmitted to the ignition means via the bus. In a special embodiment of a bus, which is described in the following, the connected sensors and ignition means are assigned as slaves in an initialization phase, in which the slaves can transmit. In these time periods, the bus master switches the voltage on the bus lines to a lower value U _actlv than is the case in the inactive bus phase U _ιnacιtv . Modulation of the energy on the bus lines by the individual slaves is only _permitted with U _actlv .

According to the invention, the sensor is now developed in such a way that the sensor element as a main current consumer is only operated in short measuring cycles, but is not used for measurement most of the time. This is achieved by charging an energy store and only when the energy store reaches a predetermined threshold value does a measurement cycle begin. These measurement results are then transmitted by the sensor either on request or automatically via the bus. The sensor element is therefore not operated during the charging phase of the energy store. In a further development it is provided that the logic module, which is used for sequence control in the sensor, and also the voltage monitoring of the energy store carries out, is assigned to an energy store, which ensures that during the active communication phase, during which the logic module cannot be supplied with energy via the bus, the necessary electrical energy is supplied by this additional energy store.

FIG. 2 shows a configuration of a bus system to which a bus master 1, which here is a control device as described above, is connected via a bus line 2 to a sensor 3 according to the invention and two ignition means 4 and 5. The sensor 3 is here a belt buckle sensor that is only operated with a low sampling rate. It is therefore not necessary to make the sensor 3 take a measurement frequently, so it can be in one at most times

Sleep mode. The ignition means 4 and 5 are belt tensioners. Instead of the parallel bus system shown here, it is possible to choose a ring or a daisy channel or a combination of different bus configurations. The control device 1 uses the sensor values to calculate the triggering algorithm and, if necessary, transmits a triggering decision to the ignition means 4 and 5. The bus line 2 is here a two-wire line, which can alternatively also be designed as a single-wire line.

Figure 1 shows a circuit diagram of the sensor according to the invention. Two bus connections a and b are connected to a rectifier G. Because a bus system for restraint systems is high due to the necessary safety

Must have reliability and the bus stations connected to the bus 2 are supplied with energy in the form of a direct current via the bus 2, error handling in the event of a short circuit in the positively biased bus line must be reversed, so that then the original ground line is used as the signal-carrying line. It is therefore uncertain which polarity the bus connections a and b will have. The rectifier G, however, makes this irrelevant.

A diode D1 and a switch S4 are each connected to the rectifier G with their anode. The other side of the switch S4, a logic module L, a sensor element S, a switch S2, an anode of a diode D2, a switch S3 and an anode of a diode D3 are connected to a further connection of the rectifier G. Another connection of the logic module L, an anode of a diode D4 and a capacitor C _E ι are connected to the cathode of the diode Dl.

The switch S2 is on its other side with a

Capacitor C _E2 and the cathode of diode D3 connected. The switch S3 is connected on its other side to the capacitor C _Eι and the cathode of the diode D2. The cathode of the diode D4 is connected to a switch S4. The other side of the switch Sl leads to a second contact of the

Sensor element S. The switch S1 connects the cathode of the diode D4 to the capacitor C _E2 in a first position and the sensor element S to the capacitor C _E2 in a second position. The control of the switch S1 is carried out by a line, not shown here, through the logic module L.

A voltage monitoring line is also connected to the capacitor C _E2 and the switch S1, which leads to the logic module L, so that there is a

Voltage monitoring of the capacitor C _E2 can be performed. The sensor element S is connected to the logic module L via an output via which an analog signal is transmitted from the sensor element S, and the sensor element S is connected to the logic module L via an input. This input is used to trigger the measurement carried out by the sensor element S.

The logic module L is connected to the switch S2 via a second output in order to actuate the switch S2. The logic module L is connected to the switch S3 via a third output in order to actuate the switch S3. The logic module L is connected to the switch S1 via a fourth output in order to actuate the switch S1.

During a first time, while the sensor shown here is not measuring, the switches S2 and S3 are closed, so that the capacitors C _E1 and C _{E2 can} charge. They charge themselves up to a voltage around the value U _ιnactlv . The diode D4 ensures that the capacitor does not discharge through the capacitor C _E ι. In addition, the diode D4 serves to charge the capacitor C _E2 more slowly. In addition, the switch S1 is in the upper position, so that the switch S1 connects the capacitor C _E2 to the cathode of the diode D4. The capacitor C _E2 can then be charged with the charging current I _L2 . The capacitor C _E1 , which is connected directly to the cathode of the diode Dl, charges with the charging current I _L1 .

Switch S4 is open because it is only closed when the measurement result is sent. The switch S4 is used to modulate the energy. It is also opened in the active bus phase to generate a logical 0, while closing S4 generates a logical 1. In this active bus phase, the voltage U _{actlv is} on the

Bus line 2, so that the capacitors C _E ι and C _{E2 are} no longer charged. A discharge of these capacitors prevents the diode Dl. The logic module L recognizes via the voltage monitoring line when the capacitor C _E2 is charged to such an extent that a measurement with the sensor element S with the energy that is charged in the capacitor C _E2 is possible. Once this time has been reached, the second time begins and the switch S1 is switched to the lower position in order to connect the sensor element S to the capacitor C _E2 , which can now discharge via the sensor element S and thus the sensor element S with electrical Energy supplied. The switch S2 is opened so that the capacitor C _E2 can discharge only via the switch S1 and the sensor element S. The capacitor C _E1 discharges through the logic module L if the switch S4 is closed and the voltage on the bus line is switched to Uactiv. This enables the

Logic module L is always supplied with electrical energy. The diode D1 prevents drainage via the bus line a and b. Here the voltage level on the bus lines is switched between two levels, U _ιnactlv and U _actl v U _{act; LV} is significantly smaller than U _ιnactlϊ . Since C _Ei and C _E2 are charged as energy reserves to a voltage around U _ιnactlv , the diode Dl blocks during the time of active data transmission, ie a level of U _actιV on the bus line. The current source via S4 therefore loads the bus, but not the sensor circuit decoupled via DI.

If the measurement was carried out with the sensor element S, which is designed here as a Hall element, then the sensor element S transmits via its output an analog signal corresponding to the measurement, which the logic module L digitizes with an integrated analog / digital converter and in one stores registers arranged in logic module L. First, however, the logic module L has transmitted a signal triggering the measurement to the sensor element S via the first output, so that the measurement by the Sensor element S can begin. The logic module L either sends the measurement results via the connections a and b and the bus 2 after completion of the measurement or on request, for example by the bus master 1. For this purpose, the switch S4 is closed and the current I _TR is used as the transmission current. By closing and opening switch S4 in the active bus phase (Uactiv on bus line 2), digital signals can be generated. The Manchester coding is used here as coding.

The switches S1, S2, S3 and S4 are designed here as transistors. The diodes D1 and D2 on the one hand enable the capacitors C _E2 and C _E ι to be charged and on the other hand that the capacitors discharge in the corresponding direction.

Here, as shown in FIG. 2, the sensor 3 is also the ignition means 4 and 5 slaves in comparison to the bus master 1.

In Figure 3 is the inventive flow chart

Procedure shown. In method step 6, the energy stores, that is to say the capacitors C _E ι and C _E2 , are charged via the diode Dl and by the switch S1 in the upper position and the closed switches S2 and S3. The charging currents I ι and I ₂ then flow. The switch S4, however, is open, so that the subsequent circuit is not short-circuited. The logic module L has the voltage monitoring, which detects when the capacitor C _{E2 has} enough energy to supply the sensor element S for at least one measurement. Instead of one measurement, several measurements can be carried out. It is therefore checked in method step 7 whether the voltage across the capacitor C _{E2 is} above a predetermined threshold value. This threshold value characterizes the energy required for the sensor element S. If this has not been achieved, the charging of the capacitor C _{E2 is continued} in step 6. If, however, the voltage is above the threshold value, then switch S2 is opened in method step 8 and switch S1 is switched to the lower position in order to supply the sensor element S with energy by C _E2 . Furthermore, the logic element L transmits a signal triggering the measurement to the sensor element S. The actual measurement is then carried out in method step 9.

In method step 10, these measurement signals are then transferred to the logic module L from the sensor element S as an analog signal. The logic module L stores the measurement signals in a register after digitization. Then the

Switch S4 is used, either on request by bus master 1 or automatically, to transmit the measurement signal via bus 2 to bus master 1. For this purpose, switch S4 is opened and closed in order to generate digital signals. This then creates the transmission current I _TR .

During the active bus phase, the switch S3 is opened at the same time, so that the energy store C _{Eι supplies} the logic module with energy during this time of the bus communication. Even if the capacitor C _E2 discharges via the sensor element S, the capacitor C _E ι continues to be charged by the current on the bus 2 via the connections a and b. C _E ι is only discharged in the active bus phase, since then the voltage on the bus line is switched to U _actlv and the logic _module L must be supplied by C _E ι.

After the transmission, the switch S4 is continuously opened again and the switches S2 and S3 are closed and the switch S1 is switched to the upper position, so that the charging of the capacitors C _Eι and C _E2 can begin again. This is then done in process steps 11 and 12. The system then jumps back to step 6 accordingly.

A distinction must therefore be made between the active and inactive bus phase on the one hand and the measurement phase and charging phase of C _E2 on the other hand, C _E1 charging in the inactive bus phase. C _E2 can also only charge in the inactive bus phase, but can also discharge again when C _{E2 has reached} the specified voltage value in order to enable measurement by the sensor element,

Claims

Expectations

1. Sensor for connection to a bus (2), the sensor (3) a sensor element (S), a logic module (L) for

Sequence control and a connection (a, b) to the bus (2), characterized in that the sensor element (S) can be connected to a first energy store (C _E2 ) and in the sensor (3) means (Sl, G) for Charging the first energy store (C _E2 ) via the bus (2) in a first time and means (L, S2) for supplying the sensor element (S) in a second time, with energy monitoring (L) charging the first energy store (C _E2 ) monitors.

2. Sensor according to claim 1, characterized in that a second energy store (C _E ι) is present, which serves to supply energy to the logic module (L) during bus communication.

3. Sensor according to claim 1 or 2, characterized in that the energy monitoring is assigned to the logic module (L) and is designed as voltage monitoring.

4. Sensor according to claim 1 or 2, characterized in that the first and second energy stores (C _Eι , C _E2 ) are each designed as capacitors.

5. Sensor according to one of the preceding claims, characterized in that the logic module (L) stores signals from the sensor element (S) and sends them via the bus (2).

6. A method for supplying energy to a sensor (3) connected to a bus (2), a logic module (L) being connected to a bus line (2) for its supply of energy during a first time, characterized in that a first time is in the first time Energy store (C _E2 ) for a sensor element (S) of the sensor (3) is charged, the energy monitoring system monitoring the charge, and the sensor element (S) being supplied by the first energy store (C _E2 ) in a second time.

7. The method according to claim 6, characterized in that a second energy store (C _Eι ) is charged, which is used during bus communication to supply energy to the logic module (L).