TRANSFORMERLESS ON-BOARD BATTERY CHARGING SYSTEM FOR AN ELECTRIC VEHICLE

1 . A transformerless on-board battery charging system for a vehicle, the system comprising:

a rechargeable battery;

a charging circuit, the charging circuit electrically coupled to the rechargeable battery, the charging circuit including a first switch configured to receive a pulse width modulated (PWM) signal and a second switch;

a first sensor assembly configured to measure a voltage of the rechargeable battery;

a second sensor assembly configured to measure a voltage of an input power line supplying power to the charging circuit from a power supply external to the vehicle;

a third sensor assembly configured to measure a current of the charging circuit; and

a controller including an electronic processor configured to:

receive a measurement of the voltage of the rechargeable battery from the first sensor assembly;

receive a measurement of the voltage of the input power line from a second sensor assembly;

compare the measurement of the voltage of the rechargeable battery to the measurement of the voltage of the input power line; and

in response to the measurement of the voltage of the input power line being greater than or approaching the measurement of the voltage of the rechargeable battery:

turn off the PWM signal to the first switch, and

with the PWM signal to the first switch turned off, receive a

measurement of the current of the charging circuit from the third sensor assembly

and, in response to the measurement of the current of the charging circuit being

approximately 0 Amps, open the second switch.

2 . The system of claim 1 , wherein the electronic processor is further configured to, with the second switch open and in response to the measurement of the voltage of the rechargeable electric vehicle battery being greater than or exceeding the measurement of the voltage of the input power line by a predetermined amount:

close the second switch; and

with the second switch closed and in response to the measurement of the current

of the charging circuit being greater than 0 Amps, turn on the PWM signal to the first

switch.

3 . The system of claim 1 , wherein the charging circuit includes a third switch and wherein the electronic processor is configured to, in response to the measurement of the voltage of the input power line being greater than or approaching the measurement of the voltage of the rechargeable battery, turn off the PWM signal to the first switch and the third switch.

4 . The system of claim 3 , wherein the PWM signal received by the third switch is approximately 180 degrees out of phase from the PWM signal received by the first switch.

5 . The system of claim 1 , wherein the third sensor assembly includes a current sensor.

6 . The system of claim 1 , where the electronic processor is configured to turn off the PWM signal to the first switch in response to the measurement of the voltage of the input power line being greater than or approaching the measurement of the voltage of the rechargeable battery by:

comparing the measurement of the voltage of the input power line to a predetermined threshold value, and

turning off the PWM signal to the first switch in response to the measurement of the voltage of the input power line being greater than the predetermined threshold value.

7 . The system of claim 6 , wherein the electronic processor is configured to set the predetermined threshold based on the voltage of the rechargeable electric vehicle battery.

8 . The system of claim 7 , wherein the electronic processor is configured to set the predetermined threshold to a value a predetermined number of volts below the voltage of the rechargeable electric vehicle battery.

9 . The system of claim 8 , wherein the predetermined number of volts is 25 Volts.

10 . A method of charging an on-board battery for an electric vehicle with a transformerless on-board battery charging system, the method comprising:

receiving, from a first sensor assembly, a measurement of a voltage of a rechargeable electric vehicle battery;

receiving, from a second sensor assembly, a measurement of a voltage of an input power line;

comparing, with an electronic processor, the measurement of the voltage of the rechargeable electric vehicle battery to the measurement the voltage of the input power line; and

in response to the measurement of the voltage of the input power line being greater than or approaching the measurement of the voltage of the rechargeable battery:

turning off the PWM signal to the first switch, and

with the PWM signal to the first switch turned off, receiving a measurement of

the current of the charging circuit from the third sensor assembly and, in response to the

measurement of the current of the charging circuit being approximately 0 Amps, opening

the second switch.

11 . The method of claim 10 , wherein the charging circuit includes a third switch and wherein turning off the PWM signal to the first switch in response to the measurement of the voltage of the input power line being greater than or approaching the predetermined threshold value includes turning off the PWM signal to the first switch and the second switch, wherein the PWM signal received by the third switch is approximately 180 degrees out of phase from the PWM signal received by the first switch.

12 . The method of claim 10 , wherein the first sensor assembly includes a current sense transformer.

13 . The method of claim 10 , wherein the maximum voltage of the rechargeable electric vehicle battery is approximately 400 Volts.

14 . The method of claim 10 , wherein the input power line is a sine wave of between approximately-200 Volts and 200 Volts.

15 . A transformerless on-board battery charging system for an electric vehicle, the system comprising:

a charging circuit including a first switch configured to receive a PWM signal and a second switch;

a controller including an electronic processor configured to:

receive a measurement of the voltage of a battery;

receive a measurement of a voltage of an input power line; and

compare the measurement of the voltage of the rechargeable electric vehicle battery to a predetermined threshold value;

compare the measurement of the voltage of the input power line to the predetermined threshold value; and

in response to the measurement of the voltage of the input power line being

greater than or approaching the predetermined threshold value:

turn off the PWM signal to the first switch, and

with the PWM signal to the first switch turned off, receive a

measurement of the current of the charging circuit and, in response to the

measurement of the current of the charging circuit being

approximately 0 Amps, open the second switch.

16 . The system of claim 15 , wherein the charging circuit includes a third switch and wherein the electronic processor is configured to, in response to the measurement of the voltage of the input power line being greater than or approaching the predetermined threshold value, turn off the PWM signal to the first switch ad the third switch.

17 . The system of claim 16 , wherein the PWM signal received by the third switch is approximately 180 degrees out of phase from the PWM signal received by the first switch.

18 . The system of claim 15 , wherein the second sensor assembly includes a current sensor.

19 . The system of claim 15 , wherein the maximum voltage of the battery is approximately 400 Volts.

20 . The system of claim 15 , wherein the input power line is a sine wave of between approximately-200 Volts and 200 Volts.