Patent Publication Number: US-2023134710-A1

Title: Electronic control device and power supply input circuit

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This disclosure relates to an electronic control device and a power supply input circuit. 
     2. Description of the Related Art 
     In a related-art on-vehicle electronic control device, in some cases, a reverse-current interrupting element remains closed even when a voltage of an on-vehicle battery serving as an external power supply is momentarily reduced. Accordingly, in order to prevent an output voltage of the reverse-current interrupting element from being reduced together with the voltage of the on-vehicle battery when the voltage of the on-vehicle battery is momentarily reduced, a capacitor is connected to an output side of the reverse-current interrupting element (see, for example, Japanese Patent Application Laid-open No. 2015-140094). 
     In the related-art on-vehicle electronic control device described above, in order to maintain the output voltage of the reverse-current interrupting element until the reduced voltage of the on-vehicle battery is recovered to a normal voltage, the capacitor on the output side of the reverse-current interrupting element is required to be a large-capacitance capacitor. Accordingly, there has been a problem in that the capacitor on the output side of the reverse-current interrupting element is increased in size, and as a result, the device is increased in size. 
     SUMMARY OF THE INVENTION 
     This disclosure has been made in order to solve the above-mentioned problem, and has an object to provide an electronic control device and a power supply input circuit with which an increase in size of the electronic control device can be suppressed. 
     According to at least one embodiment of this disclosure, there is provided an electronic control device including: a plurality of circuit blocks; and a power supply input circuit configured to supply power supplied from an external power supply to the plurality of circuit blocks, wherein the plurality of circuit blocks include a first-type block and a second-type block, and wherein the power supply input circuit includes: a power supply input terminal to be connected to the external power supply; a power supply input line including a first end portion connected to the power supply input terminal, and a second end portion being an end portion on an opposite side of the first end portion; a plurality of branching lines connected between the second end portion and each of the plurality of circuit blocks; a first reverse-current preventing element which is provided on the power supply input line, and is configured to prevent a reverse current from flowing; and a second reverse-current preventing element which is provided on one of the plurality of branching lines that is connected to the first-type block, and is configured to prevent a reverse current from flowing. 
     According to the electronic control device and the power supply input circuit of the at least one embodiment of this disclosure, an increase in size of the electronic control device can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a configuration diagram for illustrating an electronic control device according to a first embodiment of this disclosure. 
         FIG.  2    is a configuration diagram for illustrating an electronic control device serving as a comparative example. 
         FIG.  3    is a timing chart for illustrating an operation of a power supply input circuit of  FIG.  1    and an operation of a power supply input circuit of  FIG.  2   . 
         FIG.  4    is a configuration diagram for illustrating an electronic control device according to a second embodiment of this disclosure. 
         FIG.  5    is a configuration diagram for illustrating an electronic control device according to a third embodiment of this disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Now, embodiments of this disclosure are described with reference to the drawings. 
     First Embodiment 
       FIG.  1    is a configuration diagram for illustrating an electronic control device according to a first embodiment of this disclosure. In the first embodiment, an electronic control device  10  is an on-vehicle electronic control device. The electronic control device  10  includes a power supply input circuit  20  and a plurality of circuit blocks. The plurality of circuit blocks include a first circuit block  40  serving as a first-type block, and a second circuit block  50  serving as a second-type block. 
     The second circuit block  50  is one of the plurality of circuit blocks. Further, among the plurality of circuit blocks, a circuit block excluding the second circuit block  50  is the first-type block, that is, the first circuit block  40 . In the first embodiment, the number of the first-type blocks is one, and the number of the second-type blocks is one. 
     The power supply input circuit  20  includes a power supply input terminal  21 , a power supply input line  22 , a first branching line  23   a , a second branching line  23   b , a first reverse-current preventing element  24 , and a second reverse-current preventing element  25 . The power supply input circuit  20  supplies power supplied from a first external power supply  31  serving as an external power supply to the first circuit block  40  and the second circuit block  50 . 
     The power supply input terminal  21  is connected to a positive terminal of the first external power supply  31 . In the first embodiment, an on-vehicle battery is used as the first external power supply  31 . A negative terminal of the first external power supply  31  is connected to a first ground GND 1 . The first ground GND 1  is a ground inside of the electronic control device  10 . A second external power supply  32  supplies power to another device different from the electronic control device  10 . A negative terminal of the second external power supply  32  is connected to a second ground GND 2 . The second ground GND 2  is connected to the first ground GND 1  at the outside of the electronic control device  10 . 
     The power supply input line  22  includes a first end portion  22   a  and a second end portion  22   b . The first end portion  22   a  is electrically connected to the power supply input terminal  21 . The second end portion  22   b  is an end portion on the opposite side of the first end portion  22   a.    
     The first branching line  23   a  is electrically connected between the second end portion  22   b  and the first circuit block  40 . The second branching line  23   b  is electrically connected between the second end portion  22   b  and the second circuit block  50 . The first branching line  23   a  and the second branching line  23   b  form a plurality of branching lines. 
     The first reverse-current preventing element  24  is provided on the power supply input line  22 . The first reverse-current preventing element  24  prevents a reverse current from flowing. In other words, the first reverse-current preventing element  24  causes a current to flow in a forward direction, and prevents a current from flowing in a reverse direction. In the following, a portion into which the current in the forward direction flows is referred to as “input portion of the first reverse-current preventing element  24 ,” and a portion from which the current in the forward direction flows out is referred to as “output portion of the first reverse-current preventing element  24 .” 
     The input portion of the first reverse-current preventing element  24  is electrically connected to the first end portion  22   a , and the output portion of the first reverse-current preventing element  24  is electrically connected to the second end portion  22   b . As the first reverse-current preventing element  24 , for example, a diode is used. In this case, the input portion of the first reverse-current preventing element  24  is an anode, and the output portion of the first reverse-current preventing element  24  is a cathode. 
     The second reverse-current preventing element  25  is provided on the first branching line  23   a . The second reverse-current preventing element  25  prevents a reverse current from flowing. In other words, the second reverse-current preventing element  25  causes a current to flow in a forward direction, and prevents a current from flowing in a reverse direction. In the following, a portion into which the current in the forward direction flows is referred to as “input portion of the second reverse-current preventing element  25 ,” and a portion from which the current in the forward direction flows out is referred to as “output portion of the second reverse-current preventing element  25 .” 
     The input portion of the second reverse-current preventing element  25  is electrically connected to the second end portion  22   b , and the output portion of the second reverse-current preventing element  25  is electrically connected to the first circuit block  40 . As the second reverse-current preventing element  25 , for example, a diode is used. In this case, the input portion of the second reverse-current preventing element  25  is an anode, and the output portion of the second reverse-current preventing element  25  is a cathode. 
     The first circuit block  40  includes a first input capacitor  41 , a first internal power supply  42  serving as a first-type internal power supply, and a first load  43 . The first input capacitor  41  is connected between the first branching line  23   a  and the first ground GND 1 . That is, the first input capacitor  41  is electrically connected to the output portion of the second reverse-current preventing element  25 . The first internal power supply  42  and the first load  43  are connected in series to each other between the first branching line  23   a  and the first ground GND 1 . That is, the first input capacitor  41  is connected in parallel to the first internal power supply  42  and the first load  43 . 
     An input portion of the first load  43  is connected to an output portion of the first internal power supply  42 . An output portion of the first load  43  is connected to the first ground GND 1 . 
     The first internal power supply  42  generates a first output voltage Vout 1  through use of power supplied from the first external power supply  31 . A first load current IL 1  flows through the first circuit block  40 . 
     The second circuit block  50  includes a second input capacitor  51 , a second internal power supply  52  serving as a second-type internal power supply, and a second load  53 . The second input capacitor  51  is connected between the second branching line  23   b  and the first ground GND 1 . The second internal power supply  52  and the second load  53  are connected in series to each other between the second branching line  23   b  and the first ground GND 1 . That is, the second input capacitor  51  is connected in parallel to the second internal power supply  52  and the second load  53 . 
     An input portion of the second load  53  is connected to an output portion of the second internal power supply  52 . An output portion of the second load  53  is connected to the first ground GND 1 . 
     The second internal power supply  52  generates a second output voltage Vout 2  through use of power supplied from the first external power supply  31 . A second load current IL 2  flows through the second circuit block  50 . The second load current IL 2  is larger than the first load current IL 1 . 
     Further, in the first embodiment, a lower limit value Vmin 2  of an operating voltage of the second internal power supply  52  is lower than a lower limit value Vmin 1  of an operating voltage of the first internal power supply  42 . The operating voltage is an input voltage that allows the internal power supply to generate a normal output voltage. 
       FIG.  2    is a configuration diagram for illustrating an electronic control device serving as a comparative example. An electronic control device  910  of  FIG.  2    includes a power supply input circuit  920 , the first circuit block  40 , and the second circuit block  50 . 
     The power supply input circuit  920  is different from the power supply input circuit  20  of  FIG.  1    only in not including the second reverse-current preventing element  25  of  FIG.  1   . Accordingly, the electronic control device  910  is different from the electronic control device  10  of  FIG.  1    only in that the power supply input circuit  920  does not include the second reverse-current preventing element. 
     Further, in the electronic control device  910  of  FIG.  2   , similarly to the electronic control device  10  of  FIG.  1   , the second load current IL 2  is larger than the first load current IL 1 . 
       FIG.  3    is a timing chart for illustrating an operation of the power supply input circuit  20  of  FIG.  1    and an operation of the power supply input circuit  920  of  FIG.  2   . 
     In  FIG.  3   , a section A is a section in which the output voltage of the first external power supply  31  is momentarily reduced. A length of the section A is a length of time for which, even when the output voltage of the first external power supply  31  is momentarily reduced, a continuous normal operation of the electronic control device  10  is required to be ensured. In other words, during a period of the section A, regardless of the output voltage of the first external power supply  31 , the electronic control device  10  is required to be normally operated continuously. That is, during the period of the section A, the first internal power supply  42  and the second internal power supply  52  are required to continuously output normal voltages. 
     In this case, in the section A, a slope in which a voltage Vin 1 ′ across both ends of the first input capacitor  41  of  FIG.  2    is reduced and a slope in which a voltage Vin 2  across both ends of the second input capacitor  51  of  FIG.  2    is reduced are equal to each other. 
     The voltage Vin 1 ′ across both ends of the first input capacitor  41  of  FIG.  2    is reduced due to discharge via the first load  43  and discharge via the second load  53 . When the second load current IL 2  is sufficiently larger than the first load current IL 1 , the discharge via the second load  53  is dominant over the discharge via the first load  43  in the degree of influence to the slope in which the voltage Vin 1 ′ across both ends of the first input capacitor  41  of  FIG.  2    is reduced. 
     When the reduced voltage Vin 2  across both ends of the second input capacitor  51  is equal to or larger than the lower limit value Vmin 2  of the operating voltage of the second internal power supply  52 , the output voltage Vout 2  of the second internal power supply  52  is continuously output as a normal voltage. 
     Further, in  FIG.  3   , a section B is a section in which the voltage Vin 1 ′ across both ends of the first input capacitor  41  of  FIG.  2    is lower than the lower limit value Vmin 1  of the operating voltage of the first internal power supply  42 . 
     Thus, in the section B, an output voltage Vout 1 ′ of the first internal power supply  42  of  FIG.  2    does not become a normal value. Accordingly, in general, in order to prevent the voltage Vin 1 ′ across both ends of the first input capacitor  41  of  FIG.  2    from becoming lower than the lower limit value Vmin 1  of the operating voltage of the first internal power supply  42 , an electrostatic capacitance of the first input capacitor  41  is increased. However, when the electrostatic capacitance of the first input capacitor  41  is increased, a mounting area of the device is occupied, and a component cost is increased. 
     In view of the above, in the power supply input circuit  20  of  FIG.  1   , when the output voltage of the first external power supply  31  is momentarily reduced, the second reverse-current preventing element  25  prevents a sneak current from flowing from the first input capacitor  41  to the second internal power supply  52 . Further, in this case, the first reverse-current preventing element  24  prevents a sneak current from flowing from the second input capacitor  51  to the first external power supply  31 . 
     That is, when the output voltage of the first external power supply  31  is momentarily reduced, charges of the first input capacitor  41  are discharged to the first ground GND 1  via the first internal power supply  42  and the first load  43 . Further, at this time, charges of the second input capacitor  51  are discharged to the first ground GND 1  via the second internal power supply  52  and the second load  53 . 
     When a current is interrupted by the second reverse-current preventing element  25 , a sneak current is prevented from flowing from the first input capacitor  41  to the second internal power supply  52 . That is, outflow of charges to the outside of the first circuit block  40  is suppressed. As a result, when the output voltage of the first external power supply  31  is momentarily reduced, the discharge via the first load  43  becomes dominant in the degree of influence to the slope of voltage reduction of a voltage Vin 1  across both ends of the first input capacitor  41 . Thus, the first output voltage Vout 1  of the first internal power supply  42  is maintained to a normal value. 
     Accordingly, an amount of charges of the first input capacitor  41  required for maintaining the operating voltage of the first internal power supply  42  when the output voltage of the first external power supply  31  is momentarily reduced can be reduced. Thus, a capacitor having a smaller electrostatic capacitance can be used as the first input capacitor  41 . 
     As described above, the electronic control device  10  according to the first embodiment includes the plurality of circuit blocks and the power supply input circuit  20 . The plurality of circuit blocks include the first circuit block  40  serving as the first-type block, and the second circuit block  50  serving as the second-type block. The power supply input circuit  20  includes the power supply input terminal  21 , the power supply input line  22 , the first branching line  23   a , the second branching line  23   b , the first reverse-current preventing element  24 , and the second reverse-current preventing element  25 . 
     The power supply input terminal  21  is electrically connected to the first external power supply  31 . The power supply input line  22  includes the first end portion  22   a  and the second end portion  22   b . The first end portion  22   a  is electrically connected to the power supply input terminal  21 . The second end portion  22   b  is an end portion on the opposite side of the first end portion  22   a . The plurality of branching lines  23   a  and  23   b  are electrically connected between the second end portion  22   b  and each of the plurality of circuit blocks  40  and  50 . 
     The first reverse-current preventing element  24  is provided on the power supply input line  22 , and prevents a reverse current from flowing. The second reverse-current preventing element  25  is provided on the first branching line  23   a , and prevents a reverse current from flowing. The first branching line  23   a  is connected to the first circuit block  40 , that is, the first-type block. 
     With this configuration, the second reverse-current preventing element  25  can prevent a sneak current from flowing from the first input capacitor  41  to the second internal power supply  52 . Thus, a capacitor having a smaller electrostatic capacitance can be used as the first input capacitor  41 , and hence an increase in size of the electronic control device  10  can be suppressed. 
     Further, the first circuit block  40  serving as the first-type block includes the first internal power supply  42 . The first internal power supply  42  generates the first output voltage Vout 1  through use of the power supplied from the first external power supply  31 . The second circuit block  50  serving as the second-type block includes the second internal power supply  52 . The second internal power supply  52  generates the second output voltage Vout 2  through use of the power supplied from the first external power supply  31 . The lower limit value of the input voltage that allows the second internal power supply  52  to normally generate the second output voltage Vout 2  is lower than the lower limit value of the input voltage that allows the first internal power supply  42  to normally generate the first output voltage Vout 1 . 
     With this configuration, even when the output voltage of the first external power supply  31  is momentarily reduced, both of the first circuit block  40  and the second circuit block  50  can be more stably operated. 
     Further, the second load current IL 2  being a load current flowing through the second circuit block  50  is larger than the first load current IL 1  being a load current flowing through the first circuit block  40 . 
     With this configuration, even when the output voltage of the first external power supply  31  is momentarily reduced, both of the first circuit block  40  and the second circuit block  50  can be more stably operated. 
     In the first embodiment, the lower limit value of the operating voltage of the second internal power supply  52  is set to be lower than the lower limit value of the operating voltage of the first internal power supply  42 , but the lower limit value of the operating voltage of the second internal power supply  52  may be set to be higher than the lower limit value of the operating voltage of the first internal power supply  42 . In this case, the first internal power supply  42  is the second-type internal power supply, and the second internal power supply  52  is the first-type internal power supply. The first circuit block  40  is the second-type block, and the second circuit block  50  is the first-type block. In this case, it suffices that the second reverse-current preventing element is provided not on the first branching line  23   a , but on the second branching line  23   b.    
     Further, in the first embodiment, the second load current IL 2  is larger than the first load current IL 1 , but the first load current IL 1  may be larger than the second load current IL 2 . In this case, the second circuit block  50  is the first-type block, and the first circuit block  40  is the second-type block. In this case, it suffices that the second reverse-current preventing element is provided not on the first branching line  23   a , but on the second branching line  23   b.    
     Further, in the first embodiment, the electronic control device  10  includes two circuit blocks, but the electronic control device  10  may include three or more circuit blocks. In this case, it suffices that, among the plurality of internal power supplies, an internal power supply having the lowest lower limit value of the operating voltage is selected as the second-type internal power supply. In addition, it suffices that circuit blocks each including the first-type internal power supply are set as the first-type blocks, and that the second reverse-current preventing element is provided on each of a plurality of branching lines connected to the first-type blocks. 
     Further, when the electronic control device  10  includes three or more circuit blocks, it suffices that a circuit block through which the largest load current flows is selected as the second-type block. In addition, it suffices that the second reverse-current preventing element is provided on each of the plurality of branching lines connected to the first-type blocks. 
     Second Embodiment 
       FIG.  4    is a configuration diagram for illustrating an electronic control device according to a second embodiment of this disclosure. In the electronic control device  10  of  FIG.  4   , a third circuit block  60  is added to the electronic control device  10  of  FIG.  1   . Further, in the power supply input circuit  20  of  FIG.  4   , a third branching line  23   c  is added to the power supply input circuit  20  of  FIG.  1   , and another second reverse-current preventing element  26  is added to the second branching line  23   b . In the second embodiment, the number of the first-type blocks is two, and the number of the second-type blocks is one. 
     Configurations other than the above-mentioned configurations are similar to those of the electronic control device  10  of  FIG.  1   . In the following, description of the configurations similar to those of the electronic control device of  FIG.  1    is omitted. 
     The third branching line  23   c  is connected between the second end portion  22   b  and the third circuit block  60 . 
     The other second reverse-current preventing element  26  prevents a reverse current from flowing. In other words, the other second reverse-current preventing element  26  causes a current to flow in a forward direction, and prevents a current from flowing in a reverse direction. In the following, a portion into which the current in the forward direction flows is referred to as “input portion of the other second reverse-current preventing element  26 ,” and a portion from which the current in the forward direction flows out is referred to as “output portion of the other second reverse-current preventing element  26 .” 
     As the other second reverse-current preventing element  26 , for example, a diode is used. In this case, the input portion of the other second reverse-current preventing element  26  is an anode, and the output portion of the other second reverse-current preventing element  26  is a cathode. 
     The third circuit block  60  includes a third input capacitor  61  and a third load  63 . The third input capacitor  61  is connected between the third branching line  23   c  and the first ground GND 1 . The third load  63  is connected between the third branching line  23   c  and the first ground GND 1 . That is, the third input capacitor  61  is connected in parallel to the third load  63 . 
     Accordingly, in the second embodiment, the first circuit block  40  and the second circuit block  50  are each the first-type block, and the third circuit block  60  is the second-type block. 
     The first circuit block  40  being the first-type block includes the first internal power supply  42  and the first load  43 . The second circuit block  50  being the first-type block includes the second internal power supply  52  and the second load  53 . The third circuit block  60  being the second-type block includes the third load  63 , but does not include an internal power supply. 
     When the output voltage of the first external power supply  31  is momentarily reduced, the second reverse-current preventing element  25  prevents a sneak current from flowing from the first input capacitor  41  to the second internal power supply  52  and the third load  63 . When the output voltage of the first external power supply  31  is momentarily reduced, the other second reverse-current preventing element  26  prevents a sneak current from flowing from the second input capacitor  51  to the first internal power supply  42  and the third load  63 . 
     When the output voltage of the first external power supply  31  is momentarily reduced, the first reverse-current preventing element  24  prevents a sneak current from flowing from the third input capacitor  61  to the first external power supply  31 . At this time, the charges of the first input capacitor  41  are discharged to the first ground GND 1  via the first load  43  due to the function of the second reverse-current preventing element  25 . Further, the charges of the second input capacitor  51  are discharged to the first ground GND 1  via the second load  53  due to the function of the other second reverse-current preventing element  26 . 
     As a result, when the output voltage of the first external power supply  31  is momentarily reduced, a current interrupted by the second reverse-current preventing element  25  is prevented from flowing to another circuit block as a sneak current. Accordingly, the discharge via the first load  43  becomes dominant in the degree of influence to the discharge speed of the first input capacitor  41 . Further, at this time, a current interrupted by the other second reverse-current preventing element  26  is prevented from flowing to another circuit block as a sneak current. Accordingly, the discharge via the second load  53  becomes dominant in the degree of influence to the discharge speed of the second input capacitor  51 . 
     Thus, when the output voltage of the first external power supply  31  is momentarily reduced, an amount of charges required for the first input capacitor  41  to maintain the operating voltage of the first internal power supply  42  can be reduced. Similarly, when the output voltage of the first external power supply  31  is momentarily reduced, an amount of charges required for the second input capacitor  51  to maintain the operating voltage of the second internal power supply  52  can be reduced. 
     As described above, according to the electronic control device  10  of the second embodiment, the first-type block includes the first-type internal power supply which generates the output voltage through use of the power supplied from the external power supply  31 , and the load connected to the output portion of the first-type internal power supply. Further, the second-type block includes the load, but does not include an internal power supply. 
     With this configuration, a capacitor having a smaller electrostatic capacitance can be used as each of the first input capacitor  41  and the second input capacitor  51 , and hence an increase in size of the electronic control device  10  can be suppressed. 
     In the second embodiment, the second-type block is the third circuit block  60 , but the second-type block may be the first circuit block  40 . In this case, it suffices that the second reverse-current preventing element is provided on each of the second branching line  23   b  and the third branching line  23   c.    
     Further, the second-type block may be the second circuit block  50 . In this case, it suffices that the second reverse-current preventing element is provided on each of the first branching line  23   a  and the third branching line  23   c.    
     Further, in the second embodiment, the electronic control device  10  includes three circuit blocks, but the number of the circuit blocks may be two, or four or more. In this case, it suffices that a circuit block including no internal power supply is set as the second-type block. 
     Third Embodiment 
       FIG.  5    is a configuration diagram for illustrating an electronic control device according to a third embodiment of this disclosure. The electronic control device  10  includes the power supply input circuit  20 , the first circuit block  40 , and the second circuit block  50 . 
     The power supply input circuit  20  includes the power supply input terminal  21 , the power supply input line  22 , the first branching line  23   a , the second branching line  23   b , a reverse-current preventing element  27 , and another reverse-current preventing element  28 . 
     The power supply input terminal  21  is connected to the positive terminal of the first external power supply  31  serving as an external power supply. In the third embodiment, an on-vehicle battery is used as the first external power supply  31 . The negative terminal of the first external power supply  31  is connected to the first ground GND 1 . The first ground GND 1  is a ground inside of the electronic control device  10 . The second external power supply  32  supplies power to another device different from the electronic control device  10 . The negative terminal of the second external power supply  32  is connected to the second ground GND 2 . The second ground GND 2  is connected to the first ground GND 1  at the outside of the electronic control device  10 . 
     The power supply input line  22  includes the first end portion  22   a  and the second end portion  22   b . The first end portion  22   a  is electrically connected to the power supply input terminal  21 . The second end portion  22   b  is an end portion on the opposite side of the first end portion  22   a.    
     The first branching line  23   a  is electrically connected between the second end portion  22   b  and the first circuit block  40 . The second branching line  23   b  is electrically connected between the second end portion  22   b  and the second circuit block  50 . The first branching line  23   a  and the second branching line  23   b  form a plurality of branching lines. 
     The reverse-current preventing element  27  is provided on the first branching line  23   a . The other reverse-current preventing element  28  is provided on the second branching line  23   b . The reverse-current preventing elements  27  and  28  prevent a reverse current from flowing. In other words, the reverse-current preventing elements  27  and  28  cause a current to flow in a forward direction, and prevent a current from flowing in a reverse direction. In the following, a portion into which the current in the forward direction flows is referred to as “input portion of the reverse-current preventing element  27  or  28 ,” and a portion from which the current in the forward direction flows out is referred to as “output portion of the reverse-current preventing element  27  or  28 .” 
     The input portion of the reverse-current preventing element  27  is electrically connected to the second end portion  22   b , and the output portion of the reverse-current preventing element  27  is electrically connected to the first circuit block  40 . The input portion of the other reverse-current preventing element  28  is electrically connected to the second end portion  22   b , and the output portion of the other reverse-current preventing element  28  is electrically connected to the second circuit block  50 . As each of the reverse-current preventing elements  27  and  28 , for example, a diode is used. In this case, the input portion of each of the reverse-current preventing elements  27  and  28  is an anode, and the output portion of each of the reverse-current preventing elements  27  and  28  is a cathode. 
     The first circuit block  40  includes the first input capacitor  41 , the first internal power supply  42 , and the first load  43 . The first input capacitor  41  is connected between the first branching line  23   a  and the first ground GND 1 . That is, the first input capacitor  41  is electrically connected to the output portion of the reverse-current preventing element  27 . The first internal power supply  42  and the first load  43  are connected in series to each other between the first branching line  23   a  and the first ground GND 1 . That is, the first input capacitor  41  is connected in parallel to the first internal power supply  42  and the first load  43 . 
     An input portion of the first load  43  is connected to an output portion of the first internal power supply  42 . An output portion of the first load  43  is connected to the first ground GND 1 . 
     The first internal power supply  42  generates the first output voltage Vout 1  through use of power supplied from the first external power supply  31 . The first load current IL 1  flows through the first circuit block  40 . 
     The second circuit block  50  includes the second input capacitor  51 , the second internal power supply  52 , and the second load  53 . The second input capacitor  51  is connected between the second branching line  23   b  and the first ground GND 1 . That is, the second input capacitor  51  is electrically connected to the output portion of the other reverse-current preventing element  28 . The second internal power supply  52  and the second load  53  are connected in series to each other between the second branching line  23   b  and the first ground GND 1 . That is, the second input capacitor  51  is connected in parallel to the second internal power supply  52  and the second load  53 . 
     The input portion of the second load  53  is connected to the output portion of the second internal power supply  52 . The output portion of the second load  53  is connected to the first ground GND 1 . 
     The second internal power supply  52  generates the second output voltage Vout 2  through use of power supplied from the first external power supply  31 . The second load current IL 2  flows through the second circuit block  50 . 
     When the output voltage of the first external power supply  31  is momentarily reduced, the reverse-current preventing element  27  prevents a sneak current from flowing from the first input capacitor  41  to the second internal power supply  52 . Further, in this case, the other reverse-current preventing element  28  prevents a sneak current from flowing from the second input capacitor  51  to the first internal power supply  42 . 
     When the output voltage of the first external power supply  31  is momentarily reduced, the charges of the first input capacitor  41  are discharged to the first ground GND 1  via the first load  43  due to the function of the reverse-current preventing element  27 . When the output voltage of the first external power supply  31  is momentarily reduced, the charges of the second input capacitor  51  are discharged to the first ground GND 1  via the second load  53  due to the function of the other reverse-current preventing element  28 . 
     As a result, when the output voltage of the first external power supply  31  is momentarily reduced, a current interrupted by the reverse-current preventing element  27  is prevented from flowing from the first input capacitor  41  to the second internal power supply  52  as a sneak current. Accordingly, the discharge via the first load  43  becomes dominant in the degree of influence to the discharge speed of the first input capacitor  41 . 
     Accordingly, an amount of charges required for maintaining the operating voltage of the first internal power supply  42  when the output voltage of the first external power supply  31  is momentarily reduced can be reduced. Thus, a capacitor having a smaller electrostatic capacitance can be used as the first input capacitor  41 . 
     As described above, the electronic control device  10  according to the third embodiment includes the plurality of circuit blocks and the power supply input circuit  20 . The power supply input circuit  20  includes the power supply input terminal  21 , the power supply input line  22 , the plurality of first branching lines  23   a  and  23   b , and the plurality of reverse-current preventing elements  27  and  28 . The power supply input terminal  21  is connected to the first external power supply  31 . The power supply input line  22  includes the first end portion  22   a  and the second end portion  22   b . The first end portion  22   a  is connected to the power supply input terminal  21 . The second end portion  22   b  is an end portion on the opposite side of the first end portion  22   a . The plurality of branching lines  23   a  and  23   b  are connected between the second end portion  22   b  and each of the plurality of circuit blocks. The plurality of reverse-current preventing elements  27  and  28  are provided on the plurality of branching lines  23   a  and  23   b , respectively, and prevent a reverse current from flowing. 
     With this configuration, an increase in size of the electronic control device  10  can be suppressed. 
     In the third embodiment, the electronic control device  10  includes two circuit blocks, but the number of the circuit blocks may be three or more. In this case, it suffices that the reverse-current preventing element is provided on each of the branching lines corresponding to the respective circuit blocks. 
     Further, in the first to third embodiments, a diode is used as the reverse-current preventing element, but, as the reverse-current preventing element, for example, a fast recovery diode, a Schottky barrier diode, a thyristor, and back-to-back metal-oxide-semiconductor field effect transistors (MOSFETs) may be used. 
     Further, in the first to third embodiments, all of the input capacitors and the loads in the plurality of circuit blocks are connected to the first ground GND 1 , but any of the input capacitors and any of the loads may be connected to the second ground GND 2 . 
     Further, in the first to third embodiments, the second external power supply  32  is provided, but the second external power supply  32  is not required to be provided. 
     Further, in the first to third embodiments, the electronic control device  10  is the on-vehicle electronic control device, but the electronic control device  10  is not required to be an on-vehicle device as long as the electronic control device  10  uses an external power supply. Further, the external power supply to be used is not limited to the on-vehicle battery.