Fast acting FET test circuit for SIR diagnostics

US5666065A · kind A · utility

Assignee

• DELCO ELECTRONICS CORPORATION · US

Inventors

• Richard J. Ravas · Latrobe, US
• Terrell Anderson · Carmel, US
• Robert K. Constable · Kokomo, US

Key dates

• Filing date: May 22, 1996
• Grant date: Sep 9, 1997
• Expiry date: May 22, 2016

Classification

• Technology area (CPC G): Physics
• CPC primary: G01M17/0078
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

The firing circuit of an inflatable restraint system is tested to verify operation of two FETs in series with a squib which are used to apply current to the squib. For the test the squib is biased to an intermediate voltage and each FET is turned on alone to apply battery or ground voltage to the squib. High and low voltage detectors sense the voltage excursion past respective thresholds to verify FET operation, and a logic circuit immediately turns off the FET to result in a very short FET on time. If a short is present before the FET is commanded on, a detector and the logic circuit prevents FET conduction to avoid firing or degrading the squib.