Electro-magnetic valve driver

An electro-magnetic valve driver comprising:

• an electro-magnetic valve having a coil;
• a downstream switch disposed in series at a position on a downstream side of the coil in an electric current path that supplies an electric current to the coil;
• a first upstream switch disposed in series at a position between (i) an electricity supply line to which an electricity supply voltage is applied and (ii) an upstream side of the coil in the electric current path;
• a capacitor storing an electric energy that is discharged to the coil;
• a charger charging electricity for the capacitor to raise a charge voltage of the capacitor to a target voltage that is higher than the electricity supply voltage;
• a second upstream switch connecting the capacitor to an upstream side of the coil in the electric current path;
• a flowback section flowing the electric current back to the capacitor when the first upstream switch is switched from ON to OFF during a switch ON period of the downstream switch;
• an electricity supply time setting section that sets an electricity supply time for supplying the electricity to the coil;
• an electric current controller switching the downstream switch to ON during the electricity supply time set by the electricity supply time setting section while
• (i) supplying a peak electric current from the capacitor to the coil for a quick operation of the electro-magnetic valve by switching the second upstream switch to ON at a start timing of the electricity supply time,
• (ii) after supplying the peak electric current, supplying a constant electric current that is smaller than the peak electric current to the coil by (a) switching the second upstream switch to OFF and (b) performing a first upstream switch ON-OFF control, and
• (iii) after an end timing of the electricity supply time, ending the first upstream switch ON-OFF control and switching the first upstream switch to OFF;
• a collector section collecting to the capacitor a flyback energy of the coil generated by a switch OFF of the downstream switch and the first upstream switch;
• a failure detector detecting an open failure of the second upstream switch which disables a switch ON of the second upstream switch;
• and
• a delay section delaying a switch OFF timing of the downstream switch from the end timing of the electricity supply time by a preset delay time that is changed in proportion to the charge voltage of the capacitor, when the open failure is detected by the failure detector.