Abstract:
A device for triggering ignition circuits is used to increase safety without additional expenditures in the form of hardware or wiring. Plus and minus output elements of various ICs are used for this purpose. Ignition circuit diagnosis is now also distributed over two ICs. Ignition circuit diagnosis includes, in particular, the resistance measurement of the respective ignition circuit. Each substrate, in other words IC, therefore has at least one plus and one minus output element.

Description:
BACKGROUND INFORMATION  
         [0001]    Fully-integrated plus and minus output elements having diagnostic functions for ignition circuits on a common substrate are already known. Furthermore, it is known that such an IC can trigger multiple ignition circuits.  
         SUMMARY OF THE INVENTION  
         [0002]    The device according to the present invention for triggering ignition circuits has the advantage over the related art, that the safety of the device is increased without additional hardware and wiring, because the plus and minus output elements with their associated ignition circuit diagnosis are implemented independently of one another, and the plus and minus output elements for one ignition circuit can be located on two identical integrated circuits that are independent of one another. A separate implementation of plus and minus output elements is therefore possible.  
           [0003]    Furthermore, it is advantageous to have plus and minus output elements present on one substrate, giving the integrated circuit designer the option of choosing the suitable wiring regarding plus and minus output elements for any given ignition circuit, depending on the situation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 is a block diagram of the device according to the present invention.  
         [0005]    [0005]FIG. 2 is a diagnostic circuit. 
     
    
     DETAILED DESCRIPTION  
       [0006]    In order to be able to wire ignition circuits with increased safety and without additional outlay, the ignition circuits are provided, according to the present invention, with plus and minus output elements of different ICs and, therefore, substrates. Here, the term substrate designates an IC, which today is made primarily of silicon. However, it is possible to use other semiconductor materials to form a substrate, on which the circuit design can be implemented.  
         [0007]    [0007]FIG. 1 shows a diagram of the device according to the present invention. A processor  1  is connected via data inputs/outputs to substrate  2  and substrate  3 , each of which represents an ignition circuit triggering IC. It is possible for processor  1  to be connected to more than two substrates. Processor  1  controls and monitors the components of ignition circuit ICs  2  and  3  via the data inputs/outputs. Ignition circuit IC  2  has a plus output element transistor  11 , a minus output element transistor  10 , a diagnostic block  5 , and another diagnostic block  4 . In addition, ignition circuit triggering IC  2  is connected to the supply voltage via connector  14 , and to the ground via connector  17 .  
         [0008]    An ignition circuit is supplied by plus and minus output element transistors or, in short, plus and minus output elements, that are switched through when triggered, in order to supply the ignition circuit with ignition current. The plus output element transistor gets its name from the fact that it is connected to the supply voltage, while the minus output element transistor is connected to the ground.  
         [0009]    Ignition circuit IC  3  is built analogously to ignition circuit IC  2 . Ignition circuit IC  3  has a plus output element transistor  8 , a minus output element transistor  9 , and two diagnostic blocks  6  and  7 . Plus output element transistor  8  is connected on one side (here the collector) to the supply voltage at connector  15 . Minus output element transistor  9  is connected to the ground via connector  17 . On the other side, plus output element transistor  8  is connected to ignitor  13  and diagnostic block  6 . Ignitor  13  is located outside of ignition circuit triggering IC  3 . Minus output element transistor  9  is connected on its other side to ignitor  12  and diagnostic block  7 .  
         [0010]    Minus output element transistor  10  is connected, on one side, to the ground at connector  17 , and on the other side, to diagnostic block  4  and ignitor  13 . This places ignitor  13  between plus output element transistor  8  and minus output element transistor  10 , or diagnostic block  6  and diagnostic block  4 .  
         [0011]    Plus output element transistor  11  is connected on one side, as described above, to the supply voltage at connector  14 , and on its other side, with diagnostic block  5  and ignitor  12 , so that ignitor  12  lies between plus output element transistor  11  and minus output element transistor  9 , or between diagnostic block  5  and diagnostic block  7 . The bases, or gates, of transistors  8 ,  9 ,  10  and  11  are triggered by processor  1 , in order to switch these transistors through accordingly. Transistors  8 ,  9 ,  10  and  1   1  are switched through in order to fire ignitors  12  and  13 , in case restraining devices are to be deployed. Normally, i.e., when ignitors  12  and  13  are not supposed to be fired, diagnostic blocks  4 ,  5 ,  6  and  7  perform diagnostic measurements of ignitors  12  and  13 , during which ignitors  12  and  13  are measured for resistances that are either too large or too small. The resistances are measured via voltages that decrease due to diagnostic currents across ignitors  12  and  13 . If the voltages exceed or fall below the given values across ignitors  12  and  13 , there is a malfunction of ignitors  12  and  13 , the functionality of ignitors  12  and  13  is jeopardized and, therefore, also the use of the restraints. This can lead to a warning or disconnection of the restraints.  
         [0012]    [0012]FIG. 2 shows an example of a simple voltage measurement via ignitor  12 . A battery voltage Vbat is applied to an input of a constant current source  18 . Constant current source  18  supplies a constant diagnostic current coming from battery voltage Vbat. Constant current source  18  would thus correspond to diagnostic block  5  or diagnostic block  6 . Constant current source  18  is triggered by processor  1 . Processor  1  can, if need be, disconnect constant current source  18  or switch higher or lower currents in a later version. On one side, the output of constant current source  18  is connected to ignitor  12 , and on the other to a positive input of a comparator  21 . Since comparator  21  has a very high input resistance, all of the diagnostic current flows via ignitor  12 , which is connected on its other side to a constant current sink  19 . It is also possible to simply use a resistor here.  
         [0013]    Constant current sink  19  itself is connected on its other side to the ground and is also controlled by processor  1 . A constant voltage V 1  is applied to a negative input of comparator  21  via voltage source  20 , with which the voltage applied to the positive input of comparator  21  is compared. The shape of output signal  22  depends on whether voltage V 1  is greater or smaller than the voltage at the positive input. This makes it possible to check the resistance via the decreasing voltage at ignitor  12 .  
         [0014]    Constant current source  18  and constant current sink  19  are each made up of current balancing circuits. Ignition circuit ICs  2  and  3  can also have several plus and minus output elements and thus supply several ignition circuits.