Series regulator and electronic control unit for automotive vehicle

A capacitor connected to a microcomputer voltage wiring is downsized. A series regulator on an electronic control unit for automotive includes a battery 200 as an in-vehicle power supply, a relay 201, an input side capacitor 203, a series regulator circuit 10, and an output side capacitor 300, and is connected to a microcomputer 900. The series regulator circuit 10 includes an n-channel MOSFET 100, a gate voltage regulator circuit 101 as an output control circuit of an FET, and a gate voltage holding capacitor 102. A capacitor GND voltage (gate voltage) is adjusted by the gate voltage regulator circuit 101 to convert an input side capacitor voltage into an output side capacitor voltage, and supply a microcomputer current to the microcomputer 900.