POWER SWITCHING CIRCUIT

Abstract

A power switching circuit (101) is connected to a first power supply (210), a second power supply (220), a first switching circuit (310), and a second switching circuit (320). The power switching circuit has a first main path (1m), a second main path (2m), a first switching path (3), and a second switching path (4). The power switching circuit has a control circuit (20) that forms a power supply path by controlling each of the first main path, the second main path, the first switching path, and the second switching path to either a conductive or non-conductive state. When a fault is generated in one of the first circuit and the second circuit, the control circuit forms a power supply path that does not affect the operation of the other of the first circuit and the second circuit.

Description

TECHNICAL FIELDThe present disclosure relates to a power switching circuit.PRIOR ARTJP 2001-513318 A discloses a multi-battery circuit as a power switching circuit. The multi-battery circuit selectively connects one of the batteries to a load or a charger.SUMMARY OF THE INVENTIONThe power switching circuit has: a first path that supplies power from a first power supply to a first circuit; a second path that supplies power from a second power supply to a second circuit; a third path that supplies power from the first power supply to the second circuit; and a fourth path that supplies power from the second power supply to the first circuit.In such a configuration, when the first circuit has a short-circuit failure while power is supplied to the second circuit, a short-circuit current may flow from both the first power supply and the second power supply to the first circuit. In this case, the power switching circuit cannot supply power to the second circuit, and the operation of the second circuit cannot be maintained. Further improvements are required in a power switching circuit among the viewpoints described above or other non-mentioned viewpoints.An object of the present disclosure is to provide a power switching circuit that can maintain an operation of a circuit that is not defective.A power switching circuit is connected to a first power supply, a second power supply, a first circuit, and a second circuit. The power switching circuit includes: a first main path for supplying power from the first power supply to the first circuit; a second main path for supplying power from the second power supply to the second circuit; a first switching path for switching a power supply source to the first circuit from the first power supply to the second power supply when the first power supply is faulty; a second switching path for switching a power supply source to the second circuit from the second power supply to the first power supply when the second power supply is faulty; and a control circuit forming a power supply path by controlling each of the first main path, the second main path, the first switching path, and the second switching path into either a conductive or non-conductive state. When one of the first circuit and the second circuit fails, the control circuit forms a power supply path that does not impair the operation of the other circuit.According to the power switching circuit, when a fault occurs in one of the first and second switching circuits, a power supply path that does not affect the operation of the other switching circuit is formed. Thus, the power switching circuit can maintain the operation of the other of the first and second circuits that is not defective.The disclosed aspects in the specification adopt different technical solutions from each other to achieve their respective objects. The objects, features and effects disclosed herein will be further clarified by reference to the following detailed description and the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a circuit diagram illustrating a schematic configuration of a power switching circuit according to a first embodiment. FIG. 2 is a circuit diagram showing a processing operation of a control circuit. FIG. 3 is a plan view of the power switching circuit in the first embodiment. FIG. 4 is a cross-sectional view taken along a line IV-IV of FIG. 3 ; FIG. 5 is a flowchart showing an operation of the power switching circuit. FIG. 6 is a flowchart showing operations when an idle fault is determined. FIG. 7 is a view showing on / off of a MOSFET under normal, power failure, and short circuit conditions. FIG. 8 is a view showing on / off of a MOSFET during an open circuit failure. FIG. 9 is a timing chart showing an operation of the power switching circuit under normal condition. FIG. 10 is a timing chart showing an operation of the power switching circuit in a short circuit failure. FIG. 11 is a flowchart showing an operation in a power switching circuit of a first modification. FIG. 12 is a timing chart showing an operation in the power switching circuit of the first modification. FIG. 13 is a flowchart showing an operation in a power switching circuit of a second modification. FIG. 14 is a flowchart showing an operation of the power switching circuit when the first power supply is chargeable. FIG. 15 is a flowchart showing an operation of the power switching circuit when the second power supply is chargeable. FIG. 16 is a circuit diagram illustrating a schematic configuration of a power switching circuit according to a second embodiment. FIG. 17 is a circuit diagram illustrating a schematic configuration of a power switching circuit according to a third embodiment. FIG. 18 is a circuit diagram illustrating a schematic configuration of a power switching circuit according to a fourth embodiment. FIG. 19 is a view showing on / off of each mechanical switch under a normal condition. FIG. 20 is a plan view of the power switching circuit in the fourth embodiment.DETAILED DESCRIPTIONEmbodiments for implementing the present disclosure will be described according to the drawings. In each embodiment, portions corresponding to those described in the foregoing embodiment are denoted by the same reference numerals, and redundant descriptions are omitted in some cases. In each embodiment, in a case where only a part of the configuration is described, the other part of the configuration may be applied with respect to the other embodiment described above.(First Embodiment)A power switching circuit 101 according to a first embodiment will be described with reference to FIGS. 1 to 10. The power switching circuit 101 is mountable to a mobile object, for example. Examples of the mobile object include vehicles such as an electric car, a hybrid car, and a fuel cell car, flying objects such as an aircraft and a drone that lift and land electrically vertically, ships, construction machines, and agricultural machines.The power switching circuit 101 is connected to the first power supply 210 and the second power supply 220. The power switching circuit 101 is connected to the first switching circuit 310 and the second switching circuit 320. The power switching circuit 101 provides a power supply path for supplying power from the first power supply 210 to the first circuit 310. The power switching circuit 101 provides a power supply path for supplying power from the second power supply 220 to the second circuit 320. In the drawing, the first power supply 210 is described as PS 1, the second power supply 220 is described as PS 2, the first switching circuit 310 is described as CKT 1, and the second switching circuit 320 is described as CKT 2.The power switching circuit 101 switches the power supply path for the first switching circuit 310 and the second switching circuit 320. That is, the power switching circuit 101 switches the power supply for the first circuit 310 from the first power supply 210 to the second power supply 220, and switches the power supply for the second circuit 320 from the second power supply 220 to the first power supply 210. Thus, the power switching circuit 101 has a switching function. In other words, the power switching circuit 101 switches the power supplies mutually.Each of the first power supply 210 and the second power supply 220 may employ a rechargeable secondary battery or non-rechargeable primary battery. The first power supply 210 and the second power supply 220 may both be secondary batteries or primary batteries, or one may be a secondary battery and the other may be a primary battery. A rechargeable secondary battery may be considered as a power source that is allowed to be recharged. A primary battery that cannot be recharged may be referred to as a power source that is prohibited from being charged.Each of the first switching circuit 310 and the second switching circuit 320 is connected to a load, and is an electronic controller that controls the load.FIGS. 1, 2, and 3 are used to describe the configuration of the power switching circuit 101. The power switching circuit 101 includes MOSFETs 11 to 18, a control circuit 20, a board 30, and capacitors 61, 62, and each of the MOSFETs 11 to 18 is described as SW 1 to SW 8 in the drawings.The MOSFETs 11 to 18 are mounted on the board 30 described later. The MOSFETs 11 to 18 are connected to the wiring provided on the board 30. The MOSFETs 11 to 18 each include body diodes.The first MOSFET 11 and the second MOSFET 12 are connected to each other through drain electrodes. The first MOSFET 11 and the second MOSFET 12 are connected to each other through the cathodes of the body diodes.The third MOSFET 13 and the fourth MOSFET 14 are connected to each other through drain electrodes. The third MOSFET 13 and the fourth MOSFET 14 are connected to each other through the cathodes of the body diodes.The fifth MOSFET 15 and the sixth MOSFET 16 are connected to each other through drain electrodes. The fifth MOSFET 15 and the sixth MOSFET 16 are connected to each other through the cathodes of the body diodes.The seventh MOSFET 17 and the eighth MOSFET 18 are connected between drain electrodes. The seventh MOSFET 17 and the eighth MOSFET 18 are connected to each other through the cathodes of the body diodes.In this embodiment, Nch MOSFETs are used as the MOSFETs 11 to 18. Alternatively, Pch MOSFETs may be used as the MOSFETs 11 to 18. In this case, the two corresponding MOSFETs are connected to each other by the source electrodes. The two corresponding MOSFETs are, for example, the first MOSFET 11 and the second MOSFET 12, or the third MOSFET 13 and the fourth MOSFET 14.As shown in FIGS. 3 and 4, the board 30 has conductive wiring formed on an insulating substrate. The board 30 is mounted with the MOSFETs 11 to 18. The wiring includes a first main wiring 31 m, a first sub wiring 31 s, a second main wiring 32 m, a second sub wiring 32 s, a switching wiring 33, and a gate wiring 40.At least the first main wiring 31 m, the first sub wiring 31 s, the second main wiring 32 m, the second sub wiring 32 s, and the switching wiring 33, which are power supply wiring, may be provided without crossing in three dimensions. In other words, the power supply wirings can be provided without overlapping each other. Thus, the power supply wiring may be formed on the same side of the insulating substrate. In other words, the power supply wiring is formed without via (interlayer connection material). It can be said that the first main path 1 m, the second main path 2 m, the first switching path 3 and the second switching path 4 which will be explained later are formed on the same plane of the board 30. As an example, in this embodiment, a power line is formed on the surface layer of the insulating substrate.Thus, the power switching circuit 101 can simplify routing of the gate wiring 40. In this embodiment, the board 30 has the gate wiring 40 as an example of the signal wiring. However, the board 30 may have another signal wiring in addition to the gate wiring 40. In this configuration, the power switching circuit 101 can also facilitate routing of the signal wiring other than the gate wiring 40. Further, the arrangement of the circuit components of the power switching circuit 101 can be simplified, and the board area can be effectively used.Further, since the power switching circuit 101 has the power supply wiring on the surface layer, the rise of temperature of the board 30 can be suppressed compared to a configuration in which the power supply wiring is provided in the inner layer. The power switching circuit 101 has the MOSFETs 11 to 18 on the same side of the board 30, and thus the power switching circuit 101 can simplify the heat dissipation structure when heat dissipation of the MOSFETs 11 to 18 is required.The first MOSFET 11 and the second MOSFET 12 are connected to the first main wiring 31 m. The first main wiring 31 mis connected between the drain electrodes of the first MOSFET 11 and the second MOSFET 12. The first main wiring 31 mis connected to the source electrode of the first MOSFET 11 and the source electrode of the second MOSFET 12. The source electrode of the first MOSFET 11 is connected to the first power supply 210 via the first main wiring 31 m. The source electrode of the second MOSFET 12 is connected to the first switching circuit 310 via the first main wiring 31 m.The first main path 1 mincludes the first MOSFET 11, the second MOSFET 12, and the first main wiring 31 m. The first main path 1 mis connected to the first power supply 210 at one end and the first switching circuit 310 at the other end. The first main path 1 mis configured to supply power from the first power supply 210 to the first switching circuit 310. In other words, the first main path 1 mis the power supply path from the first power supply 210 to the first switching circuit 310 when the first MOSFET 11 and the second MOSFET 12 are turned on. The first MOSFET 11 and the second MOSFET 12 connected by the first main wiring 31 mmay be regarded as a first main switching portion.The third MOSFET 13 and the fourth MOSFET 14 are connected to the first sub wiring 31 s. The first sub wiring 31 sconnects between the drain electrodes of the third MOSFET 13 and the fourth MOSFET 14. The first sub wiring 31 sis connected to the source electrode of the third MOSFET 13 and the source electrode of the fourth MOSFET 14. The source electrode of the third MOSFET 13 is connected to the first power supply 210 via the first sub wiring 31 s. The source electrode of the fourth MOSFET 14 is connected to the first switching circuit 310 via the first sub wiring 31 s.The first sub path 1 sincludes the third MOSFET 13, the fourth MOSFET 14, and the first sub wiring 31 s. The first sub-path 1 sis redundant to the first main path 1 m The first sub-path 1 smay be used as a power supply path instead of the first main path 1 mwhen the third MOSFET 13 and the fourth MOSFET 14 are turned on.The seventh MOSFET 17 and the eighth MOSFET 18 are connected to the second main wiring 32 m. The second main wiring 32 mis connected between the drain electrodes of the seventh MOSFET 17 and the eighth MOSFET 18. The second main wiring 32 mis connected to the source electrode of the seventh MOSFET 17 and the source electrode of the eighth MOSFET 18. The source electrode of the seventh MOSFET 17 is connected to the second power supply 220 via the second main wiring 32 m. The source electrode of the eighth MOSFET 18 is connected to the second switching circuit 320 via the second main wiring 32 m.The second main path 2 mincludes the seventh MOSFET 17, the eighth MOSFET 18, and the second main wiring 32 m. The second main path 2 mis connected to the second power supply 220 at one end and the second switching circuit 320 at the other end. The second main path 2 mis configured to supply power from the second power supply 220 to the second switching circuit 320. In other words, the second main path 2 mis the power supply path from the second power supply 220 to the second switching circuit 320 when the seventh MOSFET 17 and the eighth MOSFET 18 are turned on. The seventh MOSFET 17 and the eighth MOSFET 18 connected to the second main wiring 32 mmay be regarded as a second main switching portion.The fifth MOSFET 15 and the sixth MOSFET 16 are connected to the second sub wiring 32 s. The second sub wiring 32 sconnects between the drain electrodes of the fifth MOSFET 15 and the sixth MOSFET 16. The second sub wiring 32 sis connected to the source electrode of the fifth MOSFET 15 and the source electrode of the sixth MOSFET 16. The source electrode of the fifth MOSFET 15 is connected to the second power supply 220 via the second sub wiring 32 s. The source electrode of the sixth MOSFET 16 is connected to the second switching circuit 320 via the second sub wiring 32 s.The second sub-path 2 sincludes the fifth MOSFET 15, the sixth MOSFET 16, and the second sub-wiring 32 s. The second sub-path 2 sis redundant to the second main path 2M. The second sub-path 2 smay be used as a power supply path instead of the second main path 2 mwhen the fifth MOSFET 15 and the sixth MOSFET 16 are turned on.The first sub wiring 31 sconnecting between the drain electrodes of the third MOSFET 13 and the fourth MOSFET 14 is connected to the switching wiring 33. The second sub wiring 32 sconnecting between the drain electrodes of the fifth MOSFET 15 and the sixth MOSFET 16 is connected to the switching wiring 33. Thus, the switching wiring 33 connects the first sub-path 1 sand the second sub-path 2 s.The fourth MOSFET 14 and the fifth MOSFET 15 are connected to each other through the cathodes of the body diodes via the switch wiring 33. The first switching path 3 includes the fourth MOSFET 14, the fifth MOSFET 15, a part of the second sub wiring 32 s, a part of the first sub wiring 31 s, and the switching wiring 33. the first switching path 3 is connected to the second power supply 220 at one end and the first switching circuit 310 at the other end. The first switching path 3 is configured to switch the power supply source to the first switching circuit 310 from the first power supply 210 to the second power supply 220 when the first power supply 210 is faulty. In other words, the power supply path to the first switching circuit 310 is configured to be switchable from the first main path 1 mto the first switching path 3.The third MOSFET 13 and the sixth MOSFET 16 are connected to each other through the cathodes of the body diodes via the switch wiring 33. The second switching path 4 includes the third MOSFET 13, the sixth MOSFET 16, a part of the first sub wiring 31 s, a part of the second sub wiring 32 s, and the switching wiring 33. The second switching path 4 is configured to switch a power supply source to the second switching circuit 320 from the second power supply 220 to the first power supply 210 when the second power supply 220 is faulty. In other words, the power supply path to the second switching circuit 320 is configured to be switchable from the second main path 2 mto the second switching path 4.The first main wiring 31 mconnecting the first switching path 3 to the first switching circuit 310 is connected to the first capacitor 61. The first capacitor 61 is connected to the first main wiring 31 min one end and to ground at the other end. Similarly, the second main wiring 32 mconnecting the second switching path 4 to the second switching circuit 320 is connected to the second capacitor 62. The second capacitor 62 is connected to the second main wiring 32m at one end and to ground at the other end. This allows the power switching circuit 101 to reduce voltage fluctuations when switching power supply paths. However, the power switching circuit 101 does not need to include the capacitor 61, 62.As shown in FIG. 1, the control circuit 20 is connected to the first main path 1 m, the second main path 2 m, the first switching path 3, and the second switching path 4. The control circuit 20 forms a power supply path by controlling each of the first main path 1 m, the second main path 2 m, the first switching path 3, and the second switching path 4 into either a conductive or non-conductive state (on and off). The control circuit 20 forms a power supply path by controlling each of the first sub-path 1 sand the second sub-path 2 sin either a conductive or non-conductive state. The control circuit 20 controls each path to be in either the conductive or non-conductive state by controlling the MOSFETs 11 to 18 to be on and off.The control circuit 20 forms a power supply path that does not interfere with the operation of the other circuit in the event of a failure in either of the first circuit 310 and the second circuit 320. The control circuit 20 also forms a power supply path so that power is supplied to the first circuit 310 and the second circuit 320 in the event of a failure in the first main path 1 mor the second main path 2 m. These points will be described in more detail later.The control circuit 20 includes a first control circuit section 21, a second control circuit section 22, a third control circuit section 23, and a fourth control circuit section 24. The control circuit portions 21 to 24 may be configured to communicate with each other. In the drawings, the control circuit section is described as a CC.The first control circuit portion 21 is supplied with operation power from the first operation power supply 51. The first control circuit portion 21 is connected to the gate electrodes of the first MOSFET 11 and the second MOSFET 12 via the gate wiring 40. The first control circuit portion 21 controls on and off the first MOSFET 11 and the second MOSFET 12. The first MOSFET 11 and the second MOSFET 12 correspond to a first semiconductor switching element. The first control circuit section 21 corresponds to a first control section. The first MOSFET 11 and the second MOSFET 12 may hereinafter be collectively referred to as a first switching portion.The second control circuit portion 22 is supplied with operation power from the second operation power supply 52. The second control circuit portion 22 is connected to the gate electrodes of the fourth MOSFET 14 and the fifth MOSFET 15 via the gate wiring 40. The second control circuit portion 22 controls on and off the fourth MOSFET 14 and the fifth MOSFET 15. The fourth MOSFET 14 and the fifth MOSFET 15 correspond to a third semiconductor switching element. The second control circuit section 22 corresponds to a third control section. The fourth MOSFET 14 and the fifth MOSFET 15 may be hereinafter collectively referred to as a third switching section.The third control circuit portion 23 is supplied with operation power from the third operation power supply 53. The third control circuit portion 23 is connected to the gate electrodes of the third MOSFET 13 and the sixth MOSFET 16 via the gate wiring 40. The third control circuit portion 23 controls the third MOSFET 13 and the sixth MOSFET 16 to be on and off. The third MOSFET 13 and the sixth MOSFET 16 correspond to a fourth semiconductor switching element. The third control circuit section 23 corresponds to a fourth control section. The third MOSFET 13 and the sixth MOSFET 16 may hereinafter be collectively referred to as a fourth switching section.The fourth control circuit section 24 is supplied with operation power from the fourth operation power supply 54. The fourth control circuit portion 24 is connected to the gate electrodes of the seventh MOSFET 17 and the eighth MOSFET 18 via the gate wiring 40. The fourth control circuit section 24 controls the seventh MOSFET 17 and the eighth MOSFET 18 on and off. The seventh MOSFET 17 and the eighth MOSFET 18 correspond to a second semiconductor switching element. The fourth control circuit section 24 corresponds to a second control section. The seventh MOSFET 17 and the eighth MOSFET 18 may hereinafter be collectively referred to as a second switching section.Thus, the power switching circuit 101 has the control circuit sections 21 to 24 for the switching sections, respectively. Thus, the power switching circuit 101 can supply power to each of the first switching circuit 310 and the second switching circuit 320 even in a single failure.The power switching circuit 101 has the operation power supplies 51 to 54 connected to the control circuit sections 21 to 24, respectively. In other words, each of the control circuit portions 21 to 24 is individually supplied with operation power. Thus, the power switching circuit 101 can maintain the switching function when a power failure is generated, compared to a configuration in which a common operation power supply is connected to the control circuit portions 21 to 24.Each of the control circuit portions 21 to 24 may be supplied with operation power from the first power supply 210 and the second power supply 220. In this case, it is preferable that the first control circuit portion 21 and the second control circuit portion 22 have different power supplies, and that the third control circuit portion 23 and the fourth control circuit portion 24 have different power supplies.For example, the first control circuit portion 21 is supplied with operation power from the first power supply 210, the second control circuit portion 22 is supplied with operation power from the second power supply 220, the third control circuit portion 23 is supplied with operation power from the first power supply 210, and the fourth control circuit portion 24 is supplied with operation power from the second power supply 220 (first supply mode). Alternatively, for each of the control circuit portions 21 to 24, the first power supply 210 and the second power supply 220 may be OR (parallel)-connected. In this case, each of the control circuit portions 21 to 24 is supplied with operation power from the first power supply 210 or the second power supply 220 at the higher voltage (second supply mode). Even with this configuration, it is possible to suppress the failure in the energization as described above.The first control circuit portion 21 may be supplied with operation power from the second power supply 220, the second control circuit portion 22 from the first power supply 210, the third control circuit portion 23 from the second power supply 220, and the fourth control circuit portion 24 from the first power supply 210. However, this mode of supplying operation power is accompanied with the following restrictions.When the first power supply 210 is in fault (low voltage), the first switching circuit 310 is powered from the second power supply 220 with the MOSFETs 14 and 15 turned on. When the operation power supply 52 of the second control circuit portion 22 is connected to the first power supply 210, the MOSFETs 14 and 15 may be turned on when the voltage of the first power supply 210 is higher than a predetermined voltage at which the second control circuit portion 22 can operate (for example, 3 volts). Thus, the second power supply 220 may supply power to the first switching circuit 310.However, when the voltage of the first power supply 210 falls below the predetermined voltage at which the second control circuit portion 22 can operate, the MOSFETs 14 and 15 cannot be turned on. Thus, the first switching circuit 310 cannot be supplied with power from the second power supply 220.When the first power supply 210 is faulty, the second switching circuit 320 is supplied with power from the second power supply 220 with the MOSFETs 17 and 18 turned on. When the operation power supply 54 of the fourth control circuit portion 24 is connected to the first power supply 210, the MOSFETs 17 and 18 may be turned on when the voltage of the first power supply 210 is higher than a predetermined voltage at which the fourth control circuit portion 24 can operate (for example, 3 volts). Thus, the second power supply 220 may supply power to the second switching circuit 320.However, when the voltage of the first power supply 210 falls below the predetermined voltage at which the fourth control circuit portion 24 can operate, the MOSFETs 17 and 18 may be turned on. Accordingly, power cannot be supplied from the second power supply 220 to the second switching circuit 320.When the second power supply 220 is in fault (low voltage), the first switching circuit 310 is supplied with power from the first power supply 210 with the MOSFETs 11 and 12 turned on. When the operation power supply 51 of the first control circuit portion 21 is connected to the second power supply 220, the MOSFETs 11 and 12 may be turned on when the voltage of the second power supply 220 is higher than the predetermined voltage at which the first control circuit portion 21 can operate (for example, 3 volts). Thus, power may be supplied to the first switching circuit 310 from the first power supply 210.However, when the voltage of the second power supply 220 falls below the predetermined voltage at which the first control circuit portion 21 can operate, the MOSFETs 11 and 12 cannot be turned on. Thus, power cannot be supplied from the first power supply 210 to the first switching circuit 310.When the second power supply 220 is faulty, the second switching circuit 320 is supplied with power from the first power supply 210 with the MOSFETs 13 and 16 turned on. When the operation power supply 53 of the third control circuit portion 23 is connected to the second power supply 220, the MOSFETs 13 and 16 may be turned on when the voltage of the second power supply 220 is higher than the predetermined voltage at which the third control circuit portion 23 can operate (for example, 3 volts). Thus, power may be supplied to the second switching circuit 320 from the first power supply 210.However, when the voltage of the second power supply 220 falls below the predetermined voltage at which the third control circuit portion 23 can operate, the MOSFETs 13 and 16 cannot be turned on. Thus, power cannot be supplied from the first power supply 210 to the second switching circuit 320. Accordingly, the first or second supply mode for the operating energy is preferred.Switching between the power supplies 210 and 220 for each of the switching circuits 310 and 320 will be described later. A failure of the first power supply 210 represents a situation where the voltage falls below the predetermined voltage at which the first switching circuit 310 can operate (e.g., 8 volts). A failure of the second power supply 220 represents a situation where the voltage falls below the predetermined voltage at which the second switching circuit 320 can operate (for example, 8 volts).The control circuit 20 may be provided to the MOSFETs 11 to 18 in common. In this case, the control circuit 20 is supplied with operation power from a single power source. The control circuit 20 may share the second control circuit section 22 and the third control circuit section 23. In this case, the common control circuit, which also serves as the first control circuit portion 21, the fourth control circuit portion 24, the second control circuit portion 22, and the third control circuit portion 23, is supplied with the operation power by the two power supplies connected in OR (parallel).As shown in FIG. 2, the control circuit 20 includes a power supply determiner 25 a, 25 b, a both-end voltage determiner (both-end voltage determiner) 26 a, 26 b, a voltage difference determiner 27 a, and an overcurrent determiner 28 ato 28 d. Each determiner may be provided in each of the control circuit portions 21 to 24, or may be provided collectively to the control circuit portions 21 to 24. The first control circuit section 21 and the second control circuit section 22 determine the states of the first main path 1 m, the first switching path 3, the power supply 210, 220, and the switching circuit 310, 320 based on the determiners 25 ato 28 a, 28 c. The third control circuit section 23 and the fourth control circuit section 24 determine the status of the second main path 2 m, the second switching path 4, the power supply 210, 220, and the switching circuit 310, 320 based on the determiners 25 b, 27 a, 26 b, 28 b, 28 d. The configuration for determining the status of the main path 1 m, 2 m, the switching path 3, 4, the power supply 210, 220, and the switching circuit 310, 320 is not limited to the following. For example, the status of the main path 1 m, 2 mand the switching path 3, 4represents disconnection or a MOSFET failure.The first power supply determiner 25 ais configured to determine the voltage drop of the first power supply 210. The first power supply determiner 25 aoutputs the result of the comparison between the voltage of the first power supply 210 and the voltage threshold (VREF). The control circuit section 21, 22 determines whether or not the voltage of the first power supply 210 is low based on the output value of the first power supply determiner 25 a.The second power supply determiner 25 bis configured to determine the voltage drop of the second power supply 220. The second power supply determiner 25 boutputs the result of the comparison between the voltage of the second power supply 220 and the voltage threshold (VREF). The control circuit section 23, 24 determines whether or not the voltage of the second power supply 220 is low based on the output value of the second power supply determiner 25 b.The first two-end voltage determiner 26 ais configured to determine the difference between the two end voltages (two end voltages) of the first main switching section. The first both-end voltage determiner 26 aoutputs the result of the comparison between the upstream voltage and the downstream voltage of the first main switching portion. The upstream side is adjacent to the first power supply 210 and the downstream side is adjacent to the first switching circuit 310.The control circuit section 21, 22, 23 determines the voltage difference between both ends of the first main switching section based on the output value of the first both-end voltage determiner 26 a. The control circuit section 21, 22 then determines a failure (open-circuit failure) of either the first MOSFET 11 or the second MOSFET 12 based on the voltage difference between the two ends. The control circuit section 21, 22 contemplates that either the first MOSFET 11 or the second MOSFET 12 has an open-circuit failure when the voltage difference between two ends is greater than a predetermined value.The second both-end voltage determiner 26 bis configured to determine the voltage difference between the two ends of the second main switching portion. The second both-end voltage determiner 26 boutputs the result of the comparison between the upstream voltage and the downstream voltage of the second main switching portion. The upstream side is adjacent to the second power supply 220 and the downstream side is adjacent to the second switching circuit 320.The control circuit section 22, 23, 24 determines the voltage difference at both ends of the second main switching section based on the output value of the second both-end voltage determiner 26 b. The control circuit section 23, 24 then determines an open-circuit failure of either the seventh MOSFET 17 or the eighth MOSFET 18 based on the voltage difference between the two ends. The control circuit section 23, 24 contemplates that either the seventh MOSFET 17 or the eighth MOSFET 18 has an open-circuit failure when the voltage difference between two ends is greater than a predetermined value. Here, the predetermined value may also be referred to as an idle failure determination value.The voltage difference determiner 27 ais configured to determine a magnitude relationship between the voltage of the first power supply 210 and the voltage of the second power supply 220. The voltage difference determiner 27 aoutputs the result of the comparison between the voltage of the first power supply 210 and the voltage of the second power supply 220. The control circuit section 21 to 24 determines the relationship between the voltage of the first power supply 210 and the voltage of the second power supply 220 based on the output value of the voltage difference determiner 27 a.The first overcurrent determiner 28 ais configured to determine the overcurrent in the first main path 1 m. The first overcurrent determiner 28 aoutputs the voltage at both ends of a current detection resistor disposed in the first main wiring 31 m. The control circuit section 21, 22 calculates the current value of the first main path 1 mbased on the resistance and both end voltages of the current detection resistance. The control circuit section 21, 22 determines that an overcurrent flows when the current value is above the current threshold. When the current value is above the current threshold value, the control circuit section 21, 22 determines that an overcurrent flows in the first circuit 310 due to a short circuit in the first circuit 310.The second overcurrent determiner 28 bis configured to determine the overcurrent in the second main path 2 m. The second overcurrent determiner 28 boutputs the voltage at both ends of a current detection resistor in the second main wiring 32 m. The control circuit section 23, 24 calculates the current value of the second main path 2 mbased on the resistance and both end voltages of the current detection resistance. The control circuit section 23, 24 determines that an overcurrent flows when the current value is above the current threshold. When the current value is above the current threshold value, the control circuit section 23, 24 determines that an overcurrent flows in the second circuit 320 due to a short circuit in the second circuit 320.The third overcurrent determiner 28 cis configured to determine the overcurrent in the first sub-path 1 sand the first switching path 3. The third overcurrent determiner 28 coutputs the voltage at both ends of a current detection resistor in the first sub wiring 31 s. The control circuit section 21, 22 calculates the current value of the first sub-path 1 sbased on the resistance and both end voltages of the current detection resistance. The control circuit section 21, 22 determines that an overcurrent flows when the current value is above the current threshold. When the current value is above the current threshold value, the control circuit section 21, 22 determines that an overcurrent flows in the first circuit 310 due to a short circuit in the first circuit 310.The fourth overcurrent determiner 28 dis configured to determine the overcurrent in the second sub-path 2 sand the second switching path 4. The fourth overcurrent determiner 28 doutputs the voltage at both ends of a current detection resistor in the second sub wiring 32 s. The control circuit section 23, 24 calculates the current value of the second sub-path 2 sbased on the resistance and both end voltages of the current detection resistance. The control circuit section 23, 24 determines that an overcurrent flows when the current value is above the current threshold. When the current value is above the current threshold value, the control circuit section 23, 24 determines that an overcurrent flows in the second circuit 320 due to a short circuit in the second circuit 320.Each of the control circuit sections 21 to 24 may be made of an ideal diode controller. The power switching circuit 101 can be easily designed using the ideal diode controller as the control circuit sections 21 to 24.The operation of the power switching circuit 101 is explained in Figs. 5 to 10. As shown in FIG. 7, when power is supplied, the control circuit 20 operates under normal conditions. In other words, the first control circuit portion 21 turns on the first main path 1 mby turning on the first MOSFET 11 and the second MOSFET 12. The fourth control circuit portion 24 turns on the second main path 2 mby turning on the seventh MOSFET 17 and the eighth MOSFET 18.In FIG. 7, the PS 1 abnormal condition indicates that only the first power supply 210 is abnormal. The PS 2 anormal condition indicates that only the second power supply 220 is abnormal. The PS 1 abnormal condition represents a voltage drop and a power cut of the first power supply 210. Similarly, the PS 2 anormal condition represents a voltage drop and a power cut of the second power supply 220. The CKT1 short-circuit condition indicates that only the first switching circuit 310 has a short-circuit fault. The CKT2 short-circuit condition indicates that only the second switching circuit 320 has a short-circuit fault.The control circuit 20 starts the flowchart shown in FIGS. 5 and 6 at a predetermined timing for supplying power. The predetermined time is, for example, when the vehicle ignition switch is turned on, when a predetermined cycle occurs, or when an interrupt is received. The control circuit 20 starts the flowchart in FIG. 5 and the flowchart in FIG. 6 at different timings.First, the flowchart of FIG. 5 will be described. At step S1, initial shift control is executed. In the situation of step S 1, all of the MOSFETs 11- 18 are turned off. From this state, the control circuit 20 turns on the first main path 1m and the second main path 2m. In other words, the first control circuit portion 21 turns on the first MOSFET 11 and the second MOSFET 12. Further, the fourth control circuit section 24 turns on the seventh MOSFET 17 and the eighth MOSFET 18.In step S 2, it is determined whether an overcurrent flows in the first switching circuit 310. The control circuit section 21, 22 determines whether or not an overcurrent flows in the first switching circuit 310 using the output result of the first overcurrent determiner 28 a. When it is determined that an overcurrent flows, the control circuit section 21, 22 assumes that the first circuit 310 is short-circuited, and proceeds to step S 3. When it is determined that no overcurrent flows, the control circuit section 21, 22 assumes that the first circuit 310 is not short-circuited, and proceeds to step S 10. The control circuit 20 may use the output result of the third overcurrent determiner 28 cto determine whether or not an overcurrent flows in the first circuit 310.In step S 3, the first main path 1 mis turned off and the first switching path 3 is turned off. As shown in FIG. 10, the first control circuit portion 21 turns off the first main path 1 mby turning off the first MOSFET 11 and the second MOSFET 12. The second control circuit portion 22 also turns off the first switching path 3 by turning off the fifth MOSFET 15 and the fourth MOSFET 14. This allows the power switching circuit 101 to restrict current from continuing to flow in the first switching circuit 310.Step S 10 is first switching processing. The first switching processing includes steps S 11 to S 17.In step S 11, it is determined whether the first power supply 210 is less than or equal to the voltage threshold. The control circuit section 21, 22 determines whether the voltage of the first power supply 210 is less than or equal to the voltage threshold value using the output result of the first power supply determiner 25 a. When it is determined that the voltage is below the voltage threshold, the control circuit section 21, 22 proceeds to step S 14. When it is determined that the voltage is not below the voltage threshold, the control circuit section 21, 22 proceeds to step S 12.In step S 14, it is determined whether the voltage of the second power supply 220 is equal to or higher than the voltage of the first power supply 210. The control circuit section 21, 22 determines whether the voltage of the second power supply 220 is equal to or higher than the voltage of the first power supply 210 using the output result of the voltage difference determiner 27 a. When it is determined that the voltage of the second power supply 220 is equal to or higher than the voltage of the first power supply 210, the control circuit section 21, 22 assumes that the first power supply 210 is abnormal and proceeds to step S 15. When it is determined that the voltage of the second power supply 220 is not greater than or equal to the voltage of the first power supply 210, the control circuit section 21, 22 assumes that the first power supply 210 is normal and proceeds to step S 12.In step S 12, the first switching path 3 is turned off. The second control circuit portion 22 turns off the first switching path 3 by turning off the fifth MOSFET 15 and the fourth MOSFET 14. At step S 13, the first main path 1 mis turned on. The first control circuit portion 21 turns on the first main path 1 mby turning on the first MOSFET 11 and the second MOSFET 12. Thus, when the control circuit 20 does not regard the first power supply 210 as abnormal, the control circuit 20 turns off the first switching path 3 and turns on the first main path 1 m.Note that turning on the path is the same as turning on the MOSFETs 11 to 18 included in the path. Similarly, turning off the path is synonymous with turning off the MOSFETs 11, 18 included in the path.At step S 15, the first main path 1 mis turned off. The first control circuit portion 21 turns off the first main path 1 mby turning off the first MOSFET 11 and the second MOSFET 12.In step S 16, the second switching path 4 is switched off. The third control circuit portion 23 turns off the second switching path 4 by turning off the third MOSFET 13 and the sixth MOSFET 16.In step S 17, the first switching path 3 is turned on. The second control circuit portion 22 turns on the first switching path 3 by turning on the fifth MOSFET 15 and the fourth MOSFET 14. As shown in FIG. 9, the control circuit 20 turns off the first main path 1 m, and turns on the first switching path 3 when the first power supply 210 is deemed to be abnormal.Thus, the control circuit 20 turns off the other before turning on one of the first switching path 3 and the second switching path 4. This point will be explained using a situation where the voltage of the first power supply 210 is 12 volts, the voltage of the second power supply 220 is 8 volts, and then the voltage of the first power supply 210 falls to 7 volts.Before the voltage of the first power supply 210 falls, the first main path 1 mand the second switching path 4 are ON, and the second main path 2 mand the first switching path 3 are OFF. Then, when the voltage of the first power supply 210 falls to 7 volts, the voltage of the first power supply 210 is lower than that of the second power supply 220.If the voltage of the first power supply 210 falls to 7 volts and the second switching path 4 remains ON, the first power supply 210 will receive a large current from the second power supply 220. In other words, the current flows through the body diode of the fifth MOSF 15 in the off state and the third MOSFET 13 in the on state to the first power supply 210. Thus, the body diode of the fifth MOSFET 15 may consume more energy than its rated energy and fail. Thus, the control circuit 20 always turns off the other switching path before one path is turned on.In step S 4, it is determined whether an overcurrent flows in the second switching circuit 320. The control circuit section 23, 24 determines whether or not an overcurrent flows in the second circuit 320 using the output result of the second overcurrent determiner 28 b. When the control circuit portion 23, 24 determines that an overcurrent flows, the second circuit 320 is assumed to be short-circuited, and proceeds to step S 5. When the control circuit portion 23, 24 determines that no overcurrent flows, the second circuit 320 is assumed not to be short-circuited, and proceeds to step S 20. After switching the path, the control circuit 20 may determine whether or not an overcurrent flows in the second circuit 320 using the output result of the fourth overcurrent determiner 28 d.In step S 5, the second main path 2 mis turned off and the second switching path 4 is turned off. The fourth control circuit portion 24 turns off the second main path 2 mby turning off the seventh MOSFET 17 and the eighth MOSFET 18. The third control circuit portion 23 also turns off the second switching path 4 by turning off the third MOSFET 13 and the sixth MOSFET 16. This allows the power switching circuit 101 to restrict current from continuing to flow in the second switching circuit 320.Step S 20 is a second switching processing. The second switching processing includes steps S 21 to S 27.In step S 21, it is determined whether the second power supply 220 is below the voltage threshold. The control circuit section 23, 24 determines whether the voltage of the second power supply 220 is below the voltage threshold value using the output result of the second power supply determiner 25 b. When the control circuit section 23, 24 determines that the voltage is below the voltage threshold, it proceeds to step S 24. When it is determined that the voltage is not below the voltage threshold, the control circuit section 21, 22 proceeds to step S 22.In step S 24, it is determined whether the voltage of the first power supply 210 is equal to or higher than that of the second power supply 220. The control circuit section 23, 24 determines whether the voltage of the first power supply 210 is equal to or higher than the voltage of the second power supply 220 using the output result of the voltage difference determiner 27 a. When the control circuit section 23, 24 determines that the voltage of the first power supply 210 is equal to or higher than the voltage of the second power supply 220, the second power supply 220 is assumed to be abnormal, and proceeds to step S 25. When the control circuit section 23, 24 determines that the voltage of the first power supply 210 is not greater than or equal to the voltage of the second power supply 220, the second power supply 220 is not assumed to be abnormal, and proceeds to step S 22.In step S 22, the second switching path 4 is turned off. The third control circuit portion 23 turns off the second switching path 4 by turning off the third MOSFET 13 and the sixth MOSFET 16. At step S23, the second main path 2m is turned on. The fourth control circuit portion 24 turns on the second main path 2 mby turning on the seventh MOSFET 17 and the eighth MOSFET 18. Thus, the control circuit 20 turns off the second switching path 4 and turns on the second main path 2 mwhen the second power supply 220 is not considered abnormal.At step S 25, the second main path 2 mis turned off. The fourth control circuit portion 24 turns off the second main path 2 mby turning off the seventh MOSFET 17 and the eighth MOSFET 18.In step S 26, the first switching path 3 is turned off. The second control circuit portion 22 turns off the first switching path 3 by turning off the fourth MOSFET 14 and the fifth MOSFET 15. At step S 26, the first switching path 3 is turned off for the same reason as at step S 16.At step S27, the second switching path 4 is turned on. The third control circuit portion 23 turns on the second switching path 4 by turning on the third MOSFET 13 and the sixth MOSFET 16. When the control circuit 20 regards the second power supply 220 as faulty, the second main path 2 mis turned off and the second switching path 4 is turned on.The control circuit 20 forms a power supply path that does not impair the operation of the second circuit 320 even when a short-circuit fault occurs in the first circuit 310. Similarly, the control circuit 20 forms a power supply path that does not impair the operation of the first circuit 310 even if a short-circuit fault occurs in the second circuit 320.In other words, the power switching circuit 101 forms a power supply path so that power is supplied to the other circuit in the event of a short-circuit fault in one of the first circuit 310 and the second circuit 320. Thus, the power switching circuit 101 may maintain the operation of any of the first circuit 310 and the second circuit 320 that have not experienced a short-circuit fault.Further, the power switching circuit 101 can supply power to the circuit 310, 320 from the normal power supply even when one of the power supplies 210 and 220 is faulty. For example, when the first power supply 210 is faulty, the second power supply 220 may supply power to the first circuit 310 and the second circuit 320.A power switching circuit may include a MOSFET through which current flows from both circuits 310, 320 to supply power from a power source to both circuits 310, 320. The MOSFET must have a power stability margin in order to be able to carry the current of both circuits 310, 320.However, each of the MOSFETs 11 to 18 conducts current only to one of the first switching circuit 310 and the second switching circuit 320. Therefore, the power switching circuit 101 does not need to have a margin in the performance of each MOSFET 11 to 18 to cope with abnormal conditions. In other words, the power switching circuit 101 can be used without requiring each MOSFET 11- 18 to have a margin of power capability. Thus, the cost and size of each MOSFET 11 to 18 can be reduced.At step S6, it is determined whether all the switches are off. The control circuit section 21 to 24 terminates the flowchart in FIG. 5 when it determines that the respective MOSFETs 11 to 18 are off, and returns to step S 2 when it determines that the respective MOSFETs 11 to 18 are not off. The state in which all switches are off is either when the voltage of the power supply 210, 220 falls below a voltage at which all the MOSFETs 11 to 18 cannot be turned on, or when both of the power supply 210 and the power supply 220 are disconnected.Next, the flowchart of FIG. 6 will be described. In FIG. 6, "a" is assigned to the number of steps similar to FIG. 5.The control circuit 20 executes step S 1 as in the above flowchart. Steps S 10 aand S 20 aare then executed.Step S 10 ais first failure determination processing for determining an open circuit failure in the MOSFETs 11 and 12 in the first main path 1 m, and switches the path based on the result of the determination.At step S 11 a, it is determined whether the SW both-end voltage difference is larger than a predetermined value. The control circuit section 21, 22 determines whether the voltage difference between the two ends of the first main switching section is larger than a predetermined value based on the output value of the first both-end voltage determiner 26 a. When the control circuit section 21, 22 determines that the voltage difference is larger than a predetermined value, it is assumed that either the first MOSFET 11 or the second MOSFET 12 has an open-circuit failure, and proceeds to step S 14 a. When the control circuit portion 21, 22 determines that the voltage difference is not greater than the predetermined value, it is assumed that the first MOSFET 11 and the second MOSFET 12 do not have an open-circuit failure, and proceeds to step S 13 a.In step S 14 a, it is determined whether the voltage of the first power supply 210 is equal to or higher than that of the second power supply 220. The control circuit section 21, 22 makes a determination using the output result of the voltage difference determiner 27 a, as in step S 14. When the control circuit section 21, 22 determines that the voltage of the first power supply 210 is equal to or higher than the voltage of the second power supply 220, it proceeds to step S 17 a. When the control circuit section 21, 22 determines that the voltage of the first power supply 210 is not greater than or equal to the voltage of the second power supply 220, it proceeds to step S 16 a.At step S13a, the first main route 1m is selected. The first control circuit section 21 selects the first main path 1 mas the path to be turned on instead of turning it on.In step S 16 a, the first switching path 3 is selected. The second control circuit section 22 selects the first switching path 3 as the path to be turned on instead of turning it on.At step S17a, the first subroute 1s is selected. The second control circuit section 22 and the third control circuit section 23 select the first sub path 1 s. At this time, the second control circuit portion 22 selects the fourth MOSFET 14 in the first sub-path 1 s. The third control circuit section 23 selects the third MOSFET 13 in the first sub-path 1 sin response to instructions from the second control circuit section 22. The second control circuit portion 22 selects the fourth MOSFET 14 as the switch to be turned on instead of turning it on. The third control circuit portion 23 selects the third MOSFET 13 as the switch to be turned on instead of turning it on.Step S 20 ais second failure determination processing for determining an open circuit failure in the MOSFETs 17 and 18 in the second main path 2 m, and switching the path based on the result of the determination.At step S21a, it is determined whether the SW both-ends voltage difference is larger than a predetermined value. The control circuit section 23, 24 determines whether the voltage difference at both ends of the second main switching section is larger than a predetermined value based on the output value of the second both-end voltage determiner 26 b. When the control circuit section 23, 24 determines that the voltage difference is larger than a predetermined value, it is assumed that either the seventh MOSFET 17 or the eighth MOSFET 18 has an open-circuit failure, and it proceeds to step S 24 a. When the control circuit portion 23, 24 determines that the voltage difference is not greater than the predetermined value, it is assumed that the seventh MOSFET 17 and the eighth MOSFET 18 do not have open-circuit failures, and proceeds to step S 23 a.In step S 24 a, it is determined whether the voltage of the first power supply 210 is equal to or higher than that of the second power supply 220. The control circuit section 23, 24 makes a determination using the output result of the voltage difference determiner 27 a, as in step S 24. When the control circuit section 23, 24 determines that the voltage of the first power supply 210 is equal to or higher than the voltage of the second power supply 220, it proceeds to step S 27 a. When the control circuit section 23, 24 determines that the voltage of the first power supply 210 is not greater than or equal to the voltage of the second power supply 220, it proceeds to step S 26 a.At step S23a, the second main route 2m is selected. The fourth control circuit section 24 selects the second main path 2 mas the path to be turned on instead of turning it on.At step S26a, the second subroute 2s is selected. The second control circuit section 22 and the third control circuit section 23 select the second sub-path 2 s. At this time, the third control circuit portion 23 selects the sixth MOSFET 16 in the second sub-path 2 s. The second control circuit section 22 selects the fifth MOSFET 15 in the second sub-path 2 sin response to instructions from the third control circuit section 23. The third control circuit portion 23 selects the sixth MOSFET 16 as the switch to be turned on instead of turning it on. The second control circuit portion 22 selects the fifth MOSFET 15 as the switch to be turned on instead of turning it on.At step S 27 a, the second switching path 4 is selected. The third control circuit section 23 selects the second switching path 4 as the path to be turned on instead of turning it on.At step S6a, the non-selection switch is turned off. Each control circuit section 21 to 24 turns off switches that are not selected as switches to be turned on (non-selection switches) to prevent current from flowing back to the power supply 210, 220.At step S6b, the selector switch is turned on. Each control circuit section 21 to 24 turns on the selected switch as described above.As shown in FIG. 8, when the second MOSFET 12 has an open-circuit failure, the first sub-path 1 sis turned on when a YES decision is made at step S 14 a. If the second MOSFET 12 has an open-circuit failure, the first switching path 3 is turned on when a NO decision is made at step S 14 a.If the eighth MOSFET 18 has an open-circuit failure, the second switching path 4 is turned on when a YES decision is made at step S24a. If the eighth MOSFET 18 has an open-circuit failure, the first sub-path 1s is turned on when a NO decision is made at step S24a.Thus, the control circuit 20 forms the power supply path so that power is supplied to the first circuit 310 even when an open circuit fault occurs in the first main path 1 m. Similarly, the control circuit 20 forms the power supply path so that power is supplied to the second circuit 320 even when an open circuit fault occurs in the second main path 2 m. Thus, the control circuit 20 can maintain the operation of the circuits 310 and 320 even if an open circuit failure occurs in the main path 1 m, 2 m.(First Modification)A first modification will be described with reference to FIGS. 11 and 12. The first modification is different from the above embodiment in the operation of the control circuit 20.The control circuit 20 executes step S 1 as in the above embodiment. Steps S 10 band S 20 bare then executed.Step S 10 bis a variant of the first shift processing. Step S 10 bincludes step S 13 bin place of steps S 12 and S 13. Step S 10 bincludes step S 16 bin place of steps S 15 and S 16.The first control circuit section 21 executes step S 13 bif a NO decision is made at S 11. Step S 13 bis the same as step S 13 a.The second control circuit section 22 executes step S 16 bif a YES decision is made at step S 14. Step S 16 bis the same as step S 16 a.Step S 20 bis a variant of the second shift processing. Step S 20 bincludes step S 23 bin place of steps S 22 and S 23. Step S 10 bincludes step S 26 bin place of steps S 25 and S 26.The fourth control circuit section 24 executes step S 23 bif a NO decision is made at step S 21. Step S 23 bis similar to step S 13 a.The third control circuit section 23 executes step S 26 bif a YES decision is made at step S 24. Step S 26 bis similar to step S 27 a.The control circuit 20 executes step S 7 after step S 20 bis completed. At step S7, it is determined whether or not a path change is determined. In the first switching processing S 10 band the second switching processing S 20 b, the control circuit 20 proceeds to step S 8 when the path is changed, or proceeds to step S 6 awhen the path is not changed. In other words, when there are no changes in the power supply path, the control circuit 20 does not enter the low consumption mode and continues to operate as it is.At step S8, a low consumption mode operation is executed. The control circuit 20 instructs the first circuit 310 and the second circuit 320 to operate in a low consumption mode. In other words, the control circuit 20 temporarily sets the first circuit 310 and the second circuit 320 in a low load state. The operation in the low consumption mode may also be referred to as a low load operation. The low consumption mode includes, for example, an operation stop and an intermittent operation.When the control circuit 20 selects the first switching path 3, only the first switching circuit 310 may be in a low load state. Similarly, the control circuit 20 may only put the second switching circuit 320 in a low load state when the second switching path 4 is selected.Steps S 6 aand S 6 bare the same as above. In other words, after turning off the non-selection switch, the control circuit 20 turns on the selection switch, with the first circuit 310 and the second circuit 320 operating in the low consumption mode. For example, as shown in FIG. 12, the power switching circuit 101 turns off the first main path 1 mand turns on the first switching path 3, and the first switching circuit 310 operates in the low consumption mode when the first power supply 210 is abnormal.Thus, when the power supply path is switched from the first main path 1 mto the first switching path 3, the control circuit 20 turns on the first switching path 3 with the first switching circuit 310 operating in the low consumption mode. When the power supply path is switched from the second main path 2 mto the second switching path 4, the control circuit 20 turns on the second switching path 4 with the second switching circuit 320 operating in the low consumption mode. Thus, the power switching circuit 101 can suppress voltage fluctuations when paths are switched. The first modification may execute the above steps S 2 to S 5.(Second Modification)A second modification will be described with reference to FIGS. 13, 14, and 15. The second modification is different from the above embodiment in the operation of the control circuit 20. the control circuit 20 changes the switching processing depending on whether the power supplies 210 and 220 are available for charging. In Figs. 13 to 15, the same step numbers are assigned to the same steps as in Fig. 5.The control circuit 20 executes step S 1 as in the above embodiment. Step S 51 is then executed.In step S 51, it is determined whether or not the first power supply 210 is chargeable. The first control circuit section 21 and the second control circuit section 22 determine whether the first power supply 210 is a rechargeable secondary battery or a primary battery that is not rechargeable. For example, the first control circuit section 21 and the second control circuit section 22 are configured to acquire power supply information indicating whether or not the first power supply 210 is chargeable. The first control circuit section 21 and the second control circuit section 22 determine whether the first power supply 210 is chargeable based on the power supply information. When the first control circuit section 21 and the second control circuit section 22 determine that charging is possible, the process proceeds to step S 30. When the first control circuit section 21 and the second control circuit section 22 determine that charging is not possible, the process proceeds to step S 10.Step S30 executes steps S11 and S14 as in step S10 as shown in Fig. 14. If a NO decision is made at step S11, step S13 is executed and step S12 is executed. If a YES decision is made at S 14, step S 16, step S 17, and step S 15 are executed in this order. The control circuit 20 turns off the other switching path before one switching path is turned on.In step S 52, it is determined whether or not the second power supply 220 is chargeable. The third control circuit section 23 and the fourth control circuit section 24 determine whether the second power supply 220 is a rechargeable secondary battery or a primary battery that is not rechargeable, similar to the first power supply 210. When the third control circuit section 23 and the fourth control circuit section 24 determine that charging is possible, the process proceeds to step S 40. When the third control circuit section 23 and the fourth control circuit section 24 determine that charging is not possible, the process proceeds to step S 20.Step S40 is similar to step S20 as shown in FIG. 15, and steps S21 and S24 are executed. When a NO decision is made at step S21, step S22 is executed and step S23 is executed. If a YES decision is made at S24, step S26, step S27 and step S25 are executed in this order. The control circuit 20 turns off the other switching path before one switching path is turned on. The control circuit 20 may process steps S 51, S 10, and S 30 in parallel with steps S 52, S 20, and S 40. Steps S 51 and S 52 may be executed by any one of the control circuit portions 21 to 24. In this case, the control circuit section sends the determination results of steps S 51 and S 52 to the other control circuit section. Alternatively, the control circuit section may store the determination results of steps S 51 and S 52 in a storage device so that the other control circuit section may refer to the determination results.When switching from the first main path 1 mto the first switching path 3, the control circuit 20 forms the power supply path such that the first power supply 210 and the second power supply 220 are temporarily connected to the first switching circuit 310 when the first power supply 210 is chargeable. Similarly, when switching from the second main path 2 mto the second switching path 4, the control circuit 20 forms the power supply path such that the first power supply 210 and the second power supply 330 are temporarily connected to the second switching circuit 320 when the second power supply 220 is chargeable. Thus, the power switching circuit 101 can suppress voltage fluctuations during switching when the power supplies 210 and 220 are chargeable.When switching from the first main path 1 mto the first switching path 3, the control circuit 20 forms the power supply path such that the first power supply 210 and the second power supply 220 are not connected to the first switching circuit 310 when the first power supply 210 is not available for charging. Similarly, when switching from the second main path 2 mto the second switching path 4, the control circuit 20 forms the power supply path such that the first power supply 210 and the second power supply 220 are not connected to the second switching circuit 320 when the second power supply 220 is not available for charging. Thus, the power switching circuit 101 can prevent the current from flowing backward and from affecting or damaging the power supplies 210, 220 when the power supplies 210, 220 are not chargeable.The power switching circuit 101 of the second modification can achieve the same effects as the above embodiment. The power switching circuit 101 in the second modification can be used regardless of whether the power supplies 210 and 220 are rechargeable or not. In other words, in the second modification, the power switching circuit 101 can perform power switching in a general manner. The power switching circuit 101 in the second modification may execute steps S 2 to S 5. In this case, the power switching circuit 101 of the second modification can switch power supplies in a general manner and maintain an operation of the first circuit 310 and the second circuit 320 that have not suffered a short-circuit fault. The power switching circuit 101 may be configured to execute only one of the first and third switching processes and one of the second and fourth switching processes depending on whether the power supplies 210, 220 are chargeable.As described above, the embodiment and the modifications of the present disclosure are described. However, the present disclosure is not limited to any way from the embodiment, and modifications may be made without departing from the spirit of the present disclosure. Hereinafter, the second to fourth embodiments will be described as other modes of the present disclosure. The embodiments may be implemented independently of each other or in combination as needed. The present disclosure is not limited to the combinations shown in the embodiments, but may be implemented by various combinations.(Second Embodiment)FIG. 16 is used to describe the power switching circuit 102 of the second embodiment. The power switching circuit 102 is different from the power switching circuit 101 in the power supply path to the control circuit 20. In FIG. 16, the gate wiring 40 is not illustrated.As shown in FIG. 16, the power switching circuit 102 has a first operation power path 34 and a second operation power path 35. the first operation power path 34 includes a first diode 36. the second operation power path 35 includes a second diode 37. the control circuit 20 is connected to the first power supply 210 via the first operation power path 34 and to the second power supply 220 via the second operation power path 35. Thus, the control circuit 20 is configured to be powered by both the first power supply 210 and the second power supply 220. It can also be said that the power switching circuit 102 is configured by OR (parallel) connecting the power supplies 210 and 220 to the control circuit 20.The power switching circuit 102 can achieve the same effect as the power switching circuit 101. The power switching circuit 102 can also execute the switching processing by the control circuit 20 when a power failure occurs in one of the power supplies 210 and 220.(Third Embodiment)FIG. 17 is used to describe the power switching circuit 103 of the third embodiment. The power switching circuit 103 is different from the power switching circuit 101 in the power supply path to the control circuit 20. In FIG. 17, the gate wiring 40 is not illustrated.As shown in FIG. 17, the power switching circuit 103 has an operation power path 38. the operation power path 38 connects the switching wiring 33 to the control circuit 20. It can also be said that the power switching circuit 103 is configured by OR (parallel) connecting the power supplies 210 and 220 to the control circuit 20.The power switching circuit 103 can achieve the same effect as the power switching circuit 101. The power switching circuit 103 may also execute the switching processing by the control circuit 20 when a power failure occurs in one of the power supplies 210 and 220.(Fourth Embodiment)A power switching circuit 104 according to a fourth embodiment will be described with reference to FIGS. 18 to 20. The power switching circuit 104 is different from the power switching circuit 101 in that it includes mechanical switches 11 a, 13 ato 17 ain place of the MOSFETs 11 to 18. In FIG. 18, wiring for turning on and off the mechanical switches 11 a, 13 ato 17 ais omitted in the illustration.The power switching circuit 104 includes a first mechanical switch 11 a, a third mechanical switch 13 a, a fourth mechanical switch 14 a, a fifth mechanical switch 15 a, a sixth mechanical switch 16 a, and a seventh mechanical switch 17 a.The first main path 1 mincludes the first mechanical switch 11 aand the first main wiring 31 m. The first mechanical switch 11 ais an alternative to the first semiconductor switching device. The first sub-path 1 sincludes the third mechanical switch 13 a, the fourth mechanical switch 14 a, and the first sub-wiring 31 s.The second main path 2 mincludes the seventh mechanical switch 17 aand the second main wiring 32 m. The seventh mechanical switch 17 ais an alternative to the second semiconductor switching device. The second sub-path 2 sincludes the fifth mechanical switch 15 a, the sixth mechanical switch 16 a, and the second sub-wiring 32 s.The first switching path 3 includes the fifth mechanical switch 15 a, the fourth mechanical switch 14 a, a part of the second sub wiring 32 s, a part of the first sub wiring 31 s, and the switching wiring 33.The second switching path 4 includes the third mechanical switch 13 a, the sixth mechanical switch 16 am, a part of the first sub wiring 31 s, a part of the second sub wiring 32 s, and the switching wiring 33.As shown in FIG. 19, the control circuit 20 controls on and off the mechanical switch 11 a, the third mechanical switch 13 a, the fourth mechanical switch 14 a, the fifth mechanical switch 15 a, the sixth mechanical switch 16 a, and the seventh mechanical switch 17 a. As in the above embodiment, the control circuit 20 also determines short-circuit and open-circuit failures and performs processing operations when a failure is determined. As shown in FIG. 20, the power switching circuit 104 may be configured on the board 30 without the use of vias or other components.The power switching circuit 104 can achieve the same effect as the power switching circuit 101. Further, the mechanical switches 11 a, 17 a, etc. can shut off power in both directions when they are turned off. Therefore, the power switching circuit 104 can set the main path 1 m, 2 mto have a single switch.Although the present disclosure has been described according to the embodiments, it is to be understood that the present disclosure is not limited to such embodiments or structures. The present disclosure encompasses various modifications and variations within the scope of equivalents. Moreover, while various combinations and modes are described in the present disclosure, other combinations and modes including only one element, more elements, or fewer elements are also within the scope and spirit of the present disclosure.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2001-513318 A

[0002]

Claims

A power switching circuit connected to a first power supply (210), a second power supply (220), a first circuit (310), and a second circuit (320), the power switching circuit comprising: a first main path (1m) for supplying power from the first power supply to the first circuit; a second main path (2m) for supplying power from the second power supply to the second circuit; a first switching path (3) for switching a power supply source of the first circuit from the first power supply to the second power supply when the first power supply is faulty; a second switching path (4) for switching a power supply source of the second circuit from the second power supply to the first power supply when the second power supply is faulty; and a control circuit (20) for forming a power supply path by controlling each of the first main path, the second main path, the first switching path, and the second switching path into either a conductive or non-conductive state, wherein the control circuit forms the power supply path when a fault is generated in one of the first circuit and the second circuit that does not affect an operation of the other of the first circuit and the second circuit.The power switching circuit according to claim 1, wherein the first main path, the second main path, the first switching path, and the second switching path are formed on a same plane of a board.The power switching circuit according to claim 1 or 2, wherein the first main path has two first semiconductor switching devices (11, 12) connected by body diode cathodes, one end being connected to the first power supply and the other end being connected to the first circuit, the second main path has two second semiconductor switching devices (17, 18) connected by body diode cathodes, one end being connected to the second power supply and the other end being connected to the second circuit, the first switching path has two third semiconductor switching elements (14, 15) connected to each other by a switching wiring (33), one end being connected to the second power supply and the other end being connected to the first circuit, and the second switching path has two fourth semiconductor switching elements (13, 16), which are connected to each other with body diode cathodes via the switching wiring, one end is connected to the first power supply and the other end is connected to the second circuit.The power switching circuit according to claim 3, wherein the control circuit includes a first control section (21) that controls the first semiconductor switching device, a second control section (24) that controls the second semiconductor switching device, a third control section (22) that controls the third semiconductor switching device, and a fourth control section (23) that controls the fourth semiconductor switching device.The power switching circuit according to claim 4, wherein each of the first control section, the second control section, the third control section and the fourth control section is individually supplied with operation power.The power switching circuit according to claim 4, wherein the control circuit is to be powered by one of the first power supply and the second power supply.The power switching circuit according to any one of claims 3 to 6, wherein the control circuit is an ideal diode controller.The power switching circuit according to any one of claims 1 to 7, wherein if the control circuit switches from the first main path to the first switching path when the first power supply is chargeable, the control circuit forms the power supply path such that the first power supply and the second power supply are temporarily connected to the first switching circuit, and if the control circuit switches from the second main path to the second switching path when the second power supply is chargeable, the control circuit forms the power supply path such that the first power supply and the second power supply are temporarily connected to the second switching circuit.The power switching circuit according to any one of claims 1 to 7, wherein if the control circuit switches from the first main path to the first switching path when the first power supply is non-chargeable, the control circuit forms the power supply path such that the first power supply and the second power supply are not connected to the first switching circuit, and if the control circuit switches from the second main path to the second switching path when the second power supply is non-chargeable, the control circuit forms the power supply path such that the first power supply and the second power supply are not connected to the second switching circuit.The power switching circuit according to any one of claims 1 to 9, wherein a wiring connecting the first switching path and the first switching circuit is connected to a first capacitor (61), and a second wiring connecting the second switching path and the second switching circuit is connected to a second capacitor (62).The power switching circuit according to any one of claims 1 to 10, wherein when the power supply path is switched from the first main path to the first switching path, the control circuit sets the first switching path to the conductive state after setting the first switching circuit to a low load state, and when the power supply path is switched from the second main path to the second switching path, the control circuit sets the second switching path to the conductive state after setting the second switching circuit to a low load state.The power switching circuit according to any one of claims 3 to 6, wherein the control circuit forms the power supply path so that power is supplied to the first circuit and the second circuit when a fault is generated in the first main path or the second main path.The power switching circuit according to any one of claims 1 to 12, wherein the control circuit puts one of the first switching path and the second switching path into the non-conductive state before the control circuit puts the other of the first switching path and the second switching path into the conductive state.

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