Trigger circuit monitoring method for safety device in vehicle e.g. airbag, belt tightener, measuring charge-time for RC trigger circuit, computing and comparing its voltages to ensure readiness to operate in crash situation

摘要

The method uses an RC trigger unit where the capacitor is charged by current Im. A control circuit is connected at point Z1. The charge time is measured so that the second of two trigger circuit voltages meets a fixed predetermined value.