Ground loss detection circuit
A ground loss detection circuit identifies a faulty ground connection in a vehicle electrical system including a pair of redundant ground lines connected between a vehicle battery/chassis ground and an electronic control unit (ECU). In particular, a first ground line is connected between the battery/chassis ground and a first ECU ground connection, while a second ground line is connected between the battery/chassis ground location and a second ECU ground connection. The ECU includes a common ground associated with selected electronic components included in the ECU. A first shunt component is connected between the first ECU ground connection and the common ground, and a second shunt component is connected between the second ECU ground connection and the common ground. The currents through the first and second shunt components are monitored to identify a current imbalance to detect a faulty ground connection in one of the first and second ground lines.
1. A ground loss detection circuit for a vehicle having a battery connected to an electronic control unit (ECU), the battery having a negative terminal connected to a chassis ground, the circuit comprising:
a first ground line connected between the negative terminal or chassis ground and a first ECU ground connection;
a second ground line connected between the negative terminal or chassis ground and a second ECU ground connection;
a common ground associated with selected electronic components included in the ECU;
a first shunt component connected between the first ECU ground connection and the common ground;
a second shunt component connected between the second ECU ground connection and the common ground; and
a monitoring circuit for sensing a current through each of the first and second shunt components to identify a faulty ground connection in either or both of the first and second ground lines.
2. The ground loss detection circuit of claim 1 wherein the first and second shunt components are resistors.
3. The ground loss detection circuit of claim 2 wherein the resistors are trace resistors located an ECU circuit board.
4. The ground loss detection circuit of claim 1 which includes a first differential amplifier coupler to monitor the current through the first shunt component by sensing the voltage across the first shunt component, and a second differential amplifier coupled to monitor the current through the second shunt component by sensing the voltage across the second shunt component.
5. The ground loss detection circuit of claim 1 wherein the ECU is a component of a vehicle safety system.
6. A method for detecting a ground loss in a vehicle electrical system having a battery connected to an electronic control unit (ECU), the battery having a negative terminal connected to a chassis ground, the vehicle electric system comprising:
a common ground associated with selected electronic components included in the ECU;
a first ground line connected between the negative terminal or the chassis ground and the common ground; and
a second ground line connected between the negative terminal or the chassis ground and the common ground;
and wherein the method comprises the steps of:
(a) monitoring a current in the first ground line;
(b) monitoring a current in the second ground line; and
(c) identifying a faulty ground connection in response to the currents monitored in steps (a) and (b).
7. The method according to claim 6 wherein the current in step (a) is monitored at a location along the first ground line proximate the common ground.
8. The method according to claim 6 wherein step (c) identifies a faulty ground connection when the current in either the first or second ground line is below a predetermined level.
9. The method according to claim 6 wherein step (c) identifies a faulty ground connection in response to a difference in current levels in the first and second ground lines.
10. The method according to claim 6 wherein step (c) identifies a faulty ground connection in response to a ratio in current levels in the first and second ground lines.