Method and system for controlling an isolated HV circuit

1. A method of controlling an isolated high voltage circuit of a vehicle comprising the high voltage circuit and a low voltage circuit wherein the high voltage circuit is isolated from the low voltage circuit, the method comprising:

detecting a change in an isolation resistance of the high voltage circuit from the low voltage circuit;

performing one of determining a speed of the vehicle and detecting a driver input indicative of a desired speed of the vehicle; and

disabling the high voltage circuit before operating the high voltage circuit in dependence on the change in the isolation resistance and the speed of the vehicle or the driver input indicative of a desired speed of the vehicle, wherein operating the high voltage circuit comprises re-enabling the high voltage circuit.

2. A method according to claim 1 , wherein operating the high voltage circuit in dependence on the change in the isolation resistance and the speed of the vehicle, comprises disabling the high voltage circuit.

3. A method according to claim 1 , wherein disabling the high voltage circuit in dependence on the speed of the vehicle comprises comparing the speed of the vehicle to a threshold speed, below which the isolated high voltage circuit is disabled in dependence on the change in the isolation resistance.

4. A method according to claim 1 , wherein the disabling of the high voltage circuit comprises isolating a high voltage battery from the high voltage circuit.

5. A method according to claim 1 , comprising:

controlling the vehicle using the low voltage circuit when the high voltage circuit is disabled.

6. A method according to claim 5 , comprising determining a status of a low voltage battery, wherein the high voltage circuit is operated in dependence on the status of the low voltage battery.

7. A method according to claim 1 , comprising detecting a further change in the isolation resistance of the high voltage circuit and operating the high voltage circuit in dependence on the further change.

8. A system for controlling an isolated high voltage circuit of a vehicle comprising a high voltage circuit and a low voltage circuit wherein the high voltage circuit is isolated from the low voltage circuit, the system comprising:

a detector arranged to detect a change in an isolation resistance of the high voltage circuit from the low voltage circuit;

a speed sensor arranged to determine a speed of the vehicle; and

a controller arranged to disable the high voltage circuit in dependence on the change in isolation resistance and the speed of the vehicle and re-enable the high voltage circuit in dependence on the speed of the vehicle increasing above a threshold speed.

9. A system according to claim 8 , wherein the isolated high voltage circuit comprises a high voltage battery and contactors having an open and closed state for respectively disconnecting and connecting the high voltage battery in the isolated high voltage circuit, the contactors being controllable by the controller, wherein the controller is arranged to disable the high voltage circuit by opening the contactors.

10. A system according to claim 8 , comprising:

a vehicle status sensor arranged to determine a status of the vehicle, wherein the controller is arranged to operate the high voltage circuit in dependence on the status of the vehicle.

11. A system according to claim 8 , comprising:

a low voltage battery status sensor arranged to determine a status of a low voltage battery as part of the low voltage circuit being arranged to control the vehicle,

wherein the controller is arranged to operate the high voltage circuit in dependence on the status of the low voltage battery.

12. A system for controlling a human machine interface (HMI) apparatus of a vehicle having a low voltage circuit and an isolated high voltage circuit being isolated from the low voltage circuit, the system comprising:

a detector arranged to detect a change in an isolation resistance of the high voltage circuit from the low voltage circuit;

a speed sensor arranged to determine a speed of the vehicle; and a controller arranged to operate the HMI apparatus in dependence on the change in the isolation resistance and the speed of the vehicle.

13. A system according to claim 12 , comprising:

a vehicle status sensor arranged to detect a status of the vehicle, wherein the controller is arranged to operate the HMI apparatus in dependence on the status of the vehicle.

14. A system according to claim 12 , comprising:

a low voltage battery status sensor arranged to determine a status of a low voltage battery as part of the low voltage circuit being arranged to control the vehicle, wherein the controller is arranged to operate the HMI apparatus in dependence on the status of the low voltage battery.

15. A vehicle comprising a system as claimed in claim 12 .

16. A method of controlling an isolated high voltage (HV) circuit of a vehicle comprising the high voltage circuit and a low voltage circuit wherein the high voltage circuit is isolated from the low voltage circuit, the method comprising:

upon vehicle power-up detecting a power-down status of HV circuit isolation; if the power-down status of the HV circuit isolation was in a first condition, enabling the HV circuit;

if the power-down status of the HV circuit isolation was in a second, different condition, waiting for a driver input indicative that the driver intends for the vehicle to increase its speed above a threshold value, and subsequently performing an isolation check to determine a current status of the HV circuit isolation.

17. The method of claim 16 , wherein said driver input comprises one of:

an increase in pressure applied to an accelerator pedal;

a decrease in pressure applied to a brake pedal; and

deactivating a parking brake.

18. A method of controlling an isolated high voltage circuit of a vehicle comprising the high voltage circuit and a low voltage circuit wherein the high voltage circuit is isolated from the low voltage circuit, the method comprising:

detecting a change in an isolation resistance of the high voltage circuit from the low voltage circuit;

detecting presence or absence of a driver input indicative that the driver intends for the vehicle to increase its speed above a threshold value; and

operating the high voltage circuit in dependence on the change in the isolation resistance and the presence or absence of the driver input.

19. The method of claim 18 , comprising disabling the high voltage circuit before operating the high voltage circuit in dependence on the change in the isolation resistance and the presence or absence of the driver input, wherein operating the high voltage circuit comprises re-enabling the high voltage circuit.