Abstract: A charged voltage between the ground and a positive pole of backup capacitor 5 and a ground-casing voltage developed between the ground and a casing of capacitor 5 are determined. When the ground-casing voltage is smaller than a first value, it is judged that capacitor 5 has an opened circuit on its positive pole side; when the ground-casing voltage is larger than a second value, it is judged that capacitor 5 has an opened circuit on its negative pole side. A difference between the ground-casing voltage and the charged voltage is divided by the ground casing voltage so that a coefficient is obtained. When the coefficient is outside a predetermined range of values, it is judged that capacitor 5 is poor in capacitance, which makes it possible to determine, even in operation, whether capacitor 5 functions properly.

Abstract: In the apparatus, a CPU 5 receives through its first and second I/O terminals a pair of voltages proportional to a terminal voltage of an electrolytic capacitor 4 serving as an energy reservoir, and a voltage proportional to an output voltage of a booster circuit 1. When the terminal voltage of the electrolytic capacitor 4 exceeds its breakdown voltage, a transistor 9 conducts, which permits the electrolytic capacitor 4 to discharge, whereby the over-voltage condition of the electrolytic capacitor 4 is resolved.

Abstract: A control system for controlling the vehicle safety devices comprises first means for calculating from an acceleration signal produced by an acceleration sensor a first evaluation value related to vehicle speed change, second means for calculating from the acceleration signal a second evaluation value related to passenger position change, third means for squaring the acceleration signal and calculating from the squared value a third evaluation value related to the collision energy magnitude, operation control means for starting and stopping the calculations in the first to third means in response to the acceleration signal, and decision means for deciding whether or not to activate the vehicle safety devices in response to the first to third evaluation values. The control system can quickly and accurately discriminate and respond to collisions irrespective of type.

Abstract: A vehicle safety system is equipped with a microcomputer for reliably detecting whether or not programs for controlling activation of passenger protection devices are being properly executed and, based on this detection, preventing problems from occurring in the control operations of the programs. According to one aspect of the invention, the system monitors a program executed on an interrupt basis at prescribed regular time intervals, a repeatedly executed program, and the operations of these programs, synchronously with the execution of the programs, and resets the microcomputer if an error is detected in the execution of either program. According to another, at the time of moving to a subroutine a code peculiar to the subroutine is saved at the entry portion and the saved code is compared with the code peculiar to the executed subroutine at the exit portion for detecting occurrence of error and if error is detected the microcomputer is reset.