Solenoid valve drive control circuit, solenoid valve drive device, and fuel injection apparatus

A solenoid valve drive control circuit that controls a driver circuit including a switching element that causes a current to flow to a solenoid valve, the solenoid valve drive control circuit comprising:

• a timing generator circuit that generates and outputs a timing signal for causing the switching element to be turned on and off, in accordance with a control signal inputted from outside for instructing the solenoid valve to open and close;
• and
• a valve closing detector circuit that detects a valve closing timing after the timing generator circuit outputs the timing signal for instructing the solenoid valve to close, by monitoring a signal voltage that is determined depending on a voltage in at least one of two terminals included in the solenoid valve for causing the current to flow, the valve closing timing being a timing at which the solenoid valve closes, wherein
• the valve closing detector circuit includes:
• a threshold voltage selector circuit that sequentially selects and outputs a threshold voltage from a plurality of threshold voltages;
• a comparator that compares the threshold voltage sequentially outputted from the threshold voltage selector circuit with the signal voltage;
• and
• a measurement circuit that (i) detects, based on an output from the comparator, each timing of the signal voltage reaching the threshold voltage sequentially outputted from the threshold voltage selector circuit, and (ii) outputs a signal indicating the valve closing timing when a change in a measurement value that is obtained through measurement of a time interval of each timing satisfies a predetermined condition.