Patent ID: 9643570
Date: 2017-05-09
CPC Classifications: B60R,F02D,F02N,G07C,H04L

Claim:
1. A system for detecting an operating state of a vehicle engine, the system comprising: an input configured to couple in a signal from a power line of a vehicle engine; a low-pass filter configured to filter the signal received from the power line to remove transient noise components of the signal which exceed 1 kHz, the transient noise components being induced on the power line by signalling activity on a control area network of the vehicle; a first detector configured to receive the filtered signal and detect when transient noise in the filtered signal rises above a first voltage threshold, the first voltage threshold being set at a voltage level that is lower than the voltage level of transient noise associated with operation of a high current electrical ignition system for starting the vehicle engine, and generate a first detection signal in response thereto; a second detector configured to receive the filtered signal and detect when the transient noise in the filtered signal falls below a second voltage threshold, which is lower than the first voltage threshold and indicates that the engine has been switched off, and generate a second detection signal in response thereto; and a circuit configured to generate a first output signal in response to the first detection signal and a second output signal in response to the second detection signal.