Abstract:
Supply system for electronic boards of an electrical distribution system comprising at least two protection boards ( 2   a,    2   b ) each able to control the supply of at least one protected pathway ( 3   a,    3   b ) on the basis of a power line ( 4   a,    4   b ), characterized by the fact that each protection board ( 2   a,    2   b ) comprises at least one voltage converter ( 13   a,    13   b ) able to provide an internal supply voltage of the protection board on the basis of a supply voltage, the voltage converter ( 13   a ) of a first protection board ( 2   a ) being connected to at least one second protection board ( 2   b ) so as to be able to provide the internal supply of the second protection board ( 2   b ) in case of failure of the voltage converter ( 13   b ) of the second protection board ( 2   b ).

Description:
[0001]    The invention lies within the technical field of the electrical power supplies of electronic boards, and more particularly such electrical power supplies of electronic boards in an electrical distribution system. 
         [0002]    An aircraft generally possesses an electrical system comprising in particular a primary distribution system for distributing electrical energy and a secondary distribution system. This secondary distribution system makes it possible to protect and to distribute the electrical power originating from internal sources, for example generators or batteries, or from external sources, such as ground power facilities. 
         [0003]    The secondary distribution system is composed of several electronic boards: computation and communication boards (EDMU) and protection boards (SSPC). Certain configurations sometimes comprise specific supply boards. 
         [0004]    The internal electronic functions of the boards are generally supplied through dedicated 28V lines, either directly on the basis of a source taken from the primary core, or via a supply board internal to the secondary distribution system. 
         [0005]      FIG. 1  illustrates the supply system for a rack  1  equipped with protection boards, referenced  2   a,    2   b  and  2   c,  ensuring the protection of three sets of SSPC pathways termed protected pathways, referenced  3   a,    3   b  and  3   c.  The EDMU boards intended for the logic control of the protection boards are not represented, for the sake of clarity. 
         [0006]    Each protection board  2   a,    2   b  and  2   c  comprises two supply inputs, a first input  4   a ,  4   b  and  4   c  connected to a power line intended to be distributed by the protection board to the various loads connected by way of at least one protected pathway and a second input  5   a,    5   b  and  5   c  connected to an auxiliary supply line intended for the internal supply of the protection board and of the protected pathway. The input intended for the internal supply is optionally made redundant (two inputs) for availability reasons. Internal buses are linked by inputs  6   a,    6   b,    6   c,    7   a,    7   b  and  7   c  to the protection boards. 
         [0007]    Each protection board comprises a single DC/DC converter ( 8   a,    8   b  and  8   c  transforming the voltage received on the second input  5   a,    5   b  and  5   c  into voltages (typically 12V, 3V3, etc.) that are usable by the internal electronic functions of the protection board, in particular the supply of the microprocessors  9   a,    9   b  and  9   c,  the generation of the control signals for the transistors  10   a,    10   b  and  10   c  controlling the protected pathways and the measurements of current and of voltage. 
         [0008]    Given that the other elements of the protection board are either made redundant, or dedicated to a protected pathway, this DC/DC converter becomes de facto the common point shared by all the functions of the protection board and of the protected pathway. In case of fault of the DC/DC converter, all the functions of the protection board and of the protected pathway of the board are lost. 
         [0009]    Moreover, segregation is generally effected between the power supply and the internal supply of the SSPC, so as to prevent a simple fault on the power supply from propagating to the electronics of the SSPC. 
         [0010]    In another exemplary embodiment, illustrated by  FIG. 2 , the internal supply is provided by a supply board  11 . The supply board  11  comprises a DC/DC converter, bearing the reference  11   a , which provides a regulated and protected voltage, thereby making it possible to simplify the design of the DC/DC converters  8   a,    8   b  and  8   c  of the protection boards. 
         [0011]    This voltage can also be made redundant if the safety demands so require. The redundancy can be extended to the DC/DC converter  11   a  of the supply board  11 . Such an example is illustrated by  FIG. 3 , in which the supply board  11  comprises two DC/DC converters  11   a  and  11   b  supplying two regulated-voltage rails, each rail supplying in a redundant manner each DC/DC converter  8   a,    8   b  and  8   c  of each protection board. 
         [0012]    Finally, the redundancy can be extended to the DC/DC internal converters  8   a,    8   b  and  8   c  of the protection boards, thereby eliminating the common point represented by this function in  FIGS. 1 to 3 . Such an example is illustrated by  FIG. 4  in which each protection board  2   a,    2   b  and  2   c  comprises two DC/DC converters respectively  8   a  and  11   a ,  8   b  and  11   b  and  8   c  and  11   c,  each DC/DC converter being supplied by a different DC/DC converter  11   a  and  11   b  of the supply board  11 . The two DC/DC converters of each protection board providing the internal supply voltage of the protection board. 
         [0013]    Such structures present the advantage of separation between power functions and logic functions as well as of availability and SSPC cost varying according to the scheme adopted. However, they also exhibit the drawback of requiring a dedicated supply board, involving an additional reference and an additional mass in the rack of boards, as well as additional development, manufacturing and maintenance costs. These additional costs also apply to the twinning of the lines for the external supply and to the twin rail for the internal supply, for each rack of protection boards. 
         [0014]    A need exists for a supply system for electronic boards not requiring any supply boards and providing the highest availability level with the lowest cost. 
         [0015]    The subject of the invention is a supply system for electronic boards comprising at least two protection boards each able to control the supply of at least one protected pathway on the basis of a power line. Each protection board comprises at least one voltage converter able to provide an internal supply voltage of the protection board on the basis of a supply voltage, the voltage converter of a first protection board being connected to at least one second protection board so as to be able to provide the internal supply of the second protection board in case of failure of the voltage converter of the second protection board. 
         [0016]    The voltage converter may be able to be supplied by the power line and by an auxiliary supply line exhibiting different voltages. 
         [0017]    The system may comprise a passive means of supply selection able to provide the internal supply of a first protection board with the voltage provided by the voltage converter of a second protection board when the voltage provided by the voltage converter of the first protection board is absent. The passive means of supply selection comprises a first input connected to the voltage converter of a second protection board and a second input connected to the voltage converter of the first protection board and an output connected to the internal supply of the first protection board. The first input is connected to the anode of a first diode, the cathode of the first diode being connected to the anode of a second diode, the cathode of the second diode being connected to the output. The second input is connected to the anode of a third diode, the cathode of the third diode being connected to the output. 
         [0018]    The voltage converter of each protection board can be connected to the internal supply of at least one other protection board by way of a common backup supply bus. 
         [0019]    The voltage converter of each protection board may be able to provide the internal supply of at least two protection boards. 
         [0020]    The system may comprise an interconnection means able to provide the internal supply of a first protection board with the voltage provided by the voltage converter of a second protection board when the voltage provided by the voltage converter of the first protection board is absent, the interconnection means comprising the voltage converter of the first protection board linked at input to the power line and to the auxiliary supply line, the voltage converter being linked at output to a protection unit which is itself connected at output to a first diode by its anode, the cathode of the first diode being connected to the common backup supply bus, the anode of a second diode being connected between the output of the voltage converter and the input of the protection unit, the cathode of the second diode being connected to the internal supply of the first protection board, the interconnection means comprising an input connected to the common backup supply bus and linked to a first terminal of a breaker, the second terminal of the breaker being connected to the anode of a third diode, the cathode of the third diode being linked to the cathode of the second diode and to the internal supply of the first protection board. 
         [0021]    Each connection between a voltage converter of a first protection board and the internal supply of another board may be protected at input by a fuse intended to isolate the voltage converter of the first board from the internal supply of a second board so as to limit the propagation of a fault of the voltage converter of the first board to the internal supply of the second board, and each connection also being protected at output by a protection unit so as to avoid propagation of a fault of the internal supply of the second board to the voltage converter of the first board. 
         [0022]    A protection unit can be a discrete with limitation based on current or a fuse. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0023]    Other aims, characteristics and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example and with reference to the appended drawings in which: 
           [0024]      FIG. 1  illustrates the supply system for a rack equipped with protection boards, 
           [0025]      FIG. 2  illustrates another exemplary supply system for a rack equipped with protection boards comprising boards PS, 
           [0026]      FIG. 3  illustrates another exemplary supply system for a rack equipped with protection boards with redundant supply board, 
           [0027]      FIG. 4  illustrates another exemplary supply system for a rack equipped with protection boards with redundant supply and with redundant supply board, 
           [0028]      FIG. 5  illustrates a first embodiment of a supply system for electronic boards according to the invention, 
           [0029]      FIG. 6  illustrates a passive means of supply selection, 
           [0030]      FIG. 7  illustrates a second embodiment of a supply system for electronic boards according to the invention, and 
           [0031]      FIG. 8  illustrates a means of interconnection with a common backup supply bus. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 5  illustrates a first embodiment of a protection boards supply system in which the internal power supplies are strung together. 
         [0033]    With respect to the previous examples, such a system is devoid of supply board  11 . 
         [0034]    It may be seen that this embodiment differs in addition from those described hereinabove on account of the fact that the voltage converter  13   a,    13   b  and  13   c  specific to each protection board is connected to the auxiliary supply line in a similar manner to the internal supply of the protection boards in the previous examples, and to the power line  4   a,    4   b  and  4   c  supplying the protected pathways. 
         [0035]    The voltage converter  13   a,    13   b  and  13   c  thus comprises similar DC/DC conversion functions to those of the DC/DC converters described hereinabove and also comprises a function for rectifying an AC voltage so as to be able to operate with two different supply voltages, including if they are of different nature (e.g.: 115VAC power line, 28VDC auxiliary line). 
         [0036]    This solution makes it possible to have a stable supply in case of defect on the power line, for example a voltage null during a transfer, thereby avoiding a reinitialization of the protection boards and therefore the fastest possible return of the supply to the loads, or a short-circuit on a load entailing a plunge in the supply via the protection boards. 
         [0037]    This solution also makes it possible to have a stable supply in case of operation of the aeroplane on the ground where all or some of the primary supplies are inactive. The protection boards may then be supplied by the auxiliary supply for maintenance operations. 
         [0038]    This solution avoids having to make the auxiliary supply input  5   a,    5   b  and  5   c  redundant since redundancy is already afforded by the power line  4   a,    4   b  and  4   c.    
         [0039]    Moreover, the redundancy of the voltage converters  13   a,    13   b  and  13   c  of the protection boards is ensured by stringing the boards together so that the DC/DC converter of a protection board supplies the adjacent protection board. The voltage converter  13   a ,  13   b  and  13   c  is then rated so as to supply two protection boards. In case of fault on the voltage converter  13   a,    13   b  and  13   c  of a protection board, the adjacent protection board ensures continuity of supply. 
         [0040]    This solution is more advantageous than twinning the voltage converters  13   a,    13   b  and  13   c  on the protection boards, since a supply of double the power is always less bulky and above all less expensive than two supplies. 
         [0041]    At the level of each protection board, the external supply input  14   a,    14   b,    14   c  originating from the adjacent board is placed in common with the internal supply originating from the voltage converter  13   a,    13   b  and  13   c  in such a way that the internal supply has priority.  FIG. 6  illustrates a passive means of supply selection comprising a first diode  15  linked by its anode to the external supply  14  and by its cathode to the anode of a second diode  16 , the cathode of the second diode  16  being connected to the internal supply of the protection board. The passive means of supply selection moreover comprises a third diode  17  connected by its cathode to the internal supply of the protection board and by its anode to the voltage produced by the voltage converter  13 . On account of the regulated nature of the supply voltages and on account of the voltage drop appearing across the terminals of a non-ideal diode, the external supply can only supply the protection board if the voltage produced by the DC/DC converter of this same board is absent. 
         [0042]    A voltage measurement at the various points (12V internal, 12V external at the midpoint of the diodes, 12V) makes it possible to diagnose a supply fault or diode fault. 
         [0043]    The external supply line  14  exported from one board to the other is protected (for example by fuse) so as to avoid a fault being propagated between the boards. 
         [0044]    Such an embodiment presents the advantage of availability equivalent to the most complex solution according to the prior art with the cost of the simplest solution. 
         [0045]      FIG. 7  illustrates a second embodiment of a protection boards supply system in which the internal supplies are made redundant by way of a common backup supply bus  18 . 
         [0046]    The voltage converter  13   a,    13   b  and  13   c  of each board is rated so as to provide a supply equivalent to that necessary for the supply of two protection boards. The output of the voltage converter  13   a,    13   b  and  13   c  of each board is connected to a common backup supply bus  18 . In case of supply fault of a board, the common backup supply bus  18  provides the supply to the faulty board. 
         [0047]    With respect to the previous embodiment, it appears that the supply system for n protection boards can maintain all the boards under function if the DC/DC converters of n/2−1 protection boards suffer a fault. 
         [0048]      FIG. 8  illustrates a means for interconnecting a protection board to the common backup supply bus  18  and to the supplies arising from the power line  4 , of the auxiliary supply line  3 . 
         [0049]    The interconnection means comprises a voltage converter  13  linked, as in the case of the first embodiment, at input to the power line  4  and to the auxiliary supply line  3 . The voltage converter  13  is linked at output to a protection unit  19 , of protected or fused discrete output DSO type, itself connected at output to a first diode  20  by its anode, the first diode  20  being connected at output to the common backup supply bus  18  by way of its cathode. 
         [0050]    Between the output of the voltage converter  13  and the input of the protection unit  19  is connected the anode of a second diode  21 . The cathode of the second diode  21  is connected to the internal supply of the protection board. 
         [0051]    Moreover, the interconnection means comprises an input connected to the common backup supply bus  18  and linked to a first terminal of a breaker  22 , the second terminal of the breaker  22  being connected to the anode of a third diode  23 . The cathode of the third diode  23  is linked to the cathode of the second diode  21  and to the internal supply of the protection board. 
         [0052]    The interconnection means allows the common pooling of the supplies through diodes. The supply arising from the common backup supply bus is drawn by a board only if the internal voltage of the board has failed. 
         [0053]    Moreover, each point of connection to the common backup supply bus  18  is protected. At input, a fuse is placed at the head and is intended to isolate the board from the bus in case of internal short-circuit and thus to avoid propagation of a fault from the board to the bus. 
         [0054]    At output, the supply arising from the voltage converter  13  destined for the backup supply bus is protected by a discrete output (DSO) with limitation based on current. In case of current overshoot, the discrete output DSO cuts the line so as to avoid the propagation of the fault from the bus to the internal supply. 
         [0055]    The various voltages are measured by the microprocessors of the board so as to diagnose any fault (fuse, diodes, converters). With this aim, various measurement points may be envisaged, in particular at the output of the voltage converter  13 , between the anode of the second diode  21  and the protection unit  19 , between the output of the protection unit  19  and the anode of the first diode  20 , between the second terminal of the breaker  22  and the anode of the third diode  23 , and downstream of the cathodes of the second and third diodes. These various measurement points make it possible to determine the failure of all or some of the components of the interconnection means. 
         [0056]    It should be noted that this type of protection may be applied to the first embodiment. 
         [0057]    The embodiment illustrated by  FIGS. 7 and 8  presents the advantage of availability equivalent to the most complex solution with the cost of the simplest solution, among the solutions illustrated by  FIGS. 1 to 4 . 
         [0058]    Moreover, the creation of a common point situated at the level of the backup bus has no effect on safety in view of the protection devices described at the level of the interconnection means. 
         [0059]    As a variant, it is possible to create several backup supply buses within one and the same rack of protection boards so that a first part of the boards share a first backup bus, while a second part of the boards share a second backup bus. This makes it possible to avoid deploying a common point on the rack as a whole.