The circuit board 33 includes a pair of second insertion holes 52 used for connecting to the power supply assembly 34. The pair of second insertion holes 52 is located at a position close to the first peripheral edge 41, corresponding to a position of the power supply assembly 34. The second insertion holes 52 correspond to a second fastening hole. Each of the pair of second insertion holes 52 receives each of a pair of bolts 53 inserted therethrough for connecting the circuit board 33 and the power supply assembly 34. In a case where the pair of second insertion holes 52 needs to be distinguished, one of the pair of second insertion holes 52 located at a position close to the first insertion hole 51A is referred to as a second insertion hole 52A whereas the other of the pair of second insertion holes 52 located at a position close to the first insertion hole 51B is referred to a second insertion hole 52B. Similarly, in a case where the bolts 53 need to be distinguished, one of the bolts 53 that is inserted through the second insertion hole 52A is referred to as a bolt 53A whereas the other of the bolts 53 that is inserted through the second insertion hole 52B is referred to as a bolt 53B. The bolts 53 are used for fixing a pair of busbars 57, which will be described later, to the circuit board 33. The bolts 53 correspond to a second fastener.