Patent ID: 8229656

Claim:
An engine starting device for controlling an engine start of a vehicle by driving a starter relay of the vehicle with a battery of the vehicle as a power supply, the engine starting device comprising: a control processing unit, and a step-up circuit for stepping up the output of the battery and outputting a drive voltage for driving the control processing unit and the starter relay; wherein the control processing unit has a function of performing an engine start control of applying the drive voltage to the starter relay to activate the starter relay in time of the engine start at which an engine starting condition is satisfied; and wherein the control processing unit performs a control function on the step-up circuit to: activate the step-up circuit so that the drive voltage does not become lower than a minimum operation voltage of the starter relay in a predetermined period necessary to start the engine in time of the engine start, and activate the step-up circuit so that the drive voltage does not become lower than a first voltage value higher than a minimum operation voltage of the control processing unit and lower than the minimum operation voltage of the starter relay when not in the predetermined period controlling the step-up circuit of executing a step-up operation for stepping up the output of the battery when the drive voltage becomes smaller than or equal to a step-up start voltage, and stopping the step-up operation when the drive voltage becomes greater than the step-up start voltage; switching the step-up start voltage of the step-up circuit between a first voltage value, which is higher than a minimum operation voltage of the control processing unit and lower than a minimum operation voltage of the starter relay, and a second voltage value which is greater than or equal to the minimum operation of the starter relay; and performing a step-up switching control of having the step-up start voltage as the first voltage value when not in the predetermined period necessary to start the engine in time of the engine start, and switching the step-up start voltage to the second voltage value in the predetermined period.