| 摘要 |
PROBLEM TO BE SOLVED: To prevent a display from being housed in a dashboard when an accessory power supply is cut off at the start-up of an engine. SOLUTION: A voltage divider circuit 27 divides the voltage of battery power supply +B and outputs it to an analog-to-digital conversion input port A/D of a microcomputer 25. A voltage divider circuit 28 divides the voltage of accessory power supply Vacc supplied from an on-vehicle battery 3 through a fuse 5b and outputs it to an input port PI of the microcomputer 25. The microcomputer 25 outputs an emission signal of a display 20 when the input level of the input port PI becomes high, and measures the voltage inputted to the input port A/D five times every other second to compute the average value Vx. When the input level of the input port PI becomes low, voltage Vn inputted to the input port A/D is measured ten times every other 0.1 second and compared with the average value Vx, and when Vn<Vx is five times or less, an acceptance signal of the display 20 is outputted. When Vn<Vx exceeds five times, the acceptance signal is not outputted.
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