IP Library › Patent Application 19038289

Patent Application

App. No. 19/038,289

Efficient Operation of a Four-Switch Buck-Boost Converter

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Patent No.: US None
App. No.: 19/038,289

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Abstract

A four-switch buck-boost converter configured to couple to a source battery and a target battery includes an inductor and switches S 1, S 2, S 3, and S 4 connected so as to define (i) a buck mode in which the switch S 3 is always ON, and the switches S 1 and S 2 control charging and discharging of the inductor, (ii) a boost mode in which the switch S 1 is always ON, and the switches S 3 and S 4 control the charging and the discharging of the inductor, and (iii) a buck-boost mode in which all of the switches S 1, S 2, S 3, and S 4 control the charging and the discharging of the inductor. A controller operates the converter in the buck mode, the boost mode, and the buck-boost mode, when it turns the switch S 1 ON at a beginning of a switching cycle, and turns the switch S 4 ON at an end of the switching cycle.

Claims (52)

1 . A system for controlling a charging current while transferring energy from a source battery to a target battery in an electric vehicle (EV), the system comprising:

a four-switch buck-boost converter configured to couple to the source battery and the target battery and including:

an inductor, and

switches S 1 , S 2 , S 3 , and S 4 connected so as to define (i) a buck mode in which the switch S 3 is always ON, and the switches S 1 and S 2 control charging and discharging of the inductor, (ii) a boost mode in which the switch S 1 is always ON, and the switches S 3 and S 4 control the charging and the discharging of the inductor, and (iii) a buck-boost mode in which all of the switches S 1 , S 2 , S 3 , and S 4 control the charging and the discharging of the inductor; and

a controller configured to operate the four-switch buck-boost converter in:

(a) the buck mode when voltage V g across the source battery is higher than voltage V EV across the target battery,

(b) the boost mode when the voltage V g is lower than the voltage V EV , and

(c) the buck-boost mode when the voltages V EV and V g differ less by a predetermined amount, wherein the controller turns the switch S 1 ON at a beginning of a switching cycle, and turns the switch S 4 ON at an end of the switching cycle.

2 . The system of claim 1 , wherein the controller applies, in the buck-boost mode:

(i) trailing edge pulse width modulation (PWM) to operate the switch S 1 , and

(ii) leading edge PWM to operate the switch S 4 .

3 . The system of claim 1 , wherein the switching cycle includes a region in which the switches S 2 and S 4 are ON, and the switches S 1 and S 3 are OFF.

4 . The system of claim 1 , wherein the switching cycle includes:

a first region in which the switches S 1 and S 3 are ON, and the switches S 2 and S 4 are OFF;

a second region in which the switches S 2 and S 3 are ON, and the switches S 1 and S 4 are OFF; and

a third region in which the switches S 2 and S 4 are ON, and the switches S 1 and S 3 are OFF.

5 . The system of claim 4 , wherein the first region has a longer duration than the third region.

6 . The system of claim 4 , wherein a slope of an inductor current in the third region is substantially zero.

7 . The system of claim 4 , wherein a slope of an inductor current in the first region is positive when V g >V EV .

8 . The system of claim 4 , wherein a slope of an inductor current in the first region is negative when V g <V EV .

9 . The system of claim 1 , wherein the predetermined amount by which the voltages V EV and V g differ in the buck-boost mode is between 20V and 30V.

10 . A method for operating a four-switch buck-boost converter configured to transfer energy from a source battery to a target battery in an electric vehicle (EV), the four-switch buck-boost converter including an inductor and switches S 1 , S 2 , S 3 , and S 4 , the method comprising:

operating the four-switch buck-boost converter a buck mode when voltage V g across the source battery is higher than voltage V EV across the target battery, including keeping the switch S 3 ON, and operating the switches S 1 and S 2 to control charging and discharging of the inductor;

operating the four-switch buck-boost converter a boost mode when the voltage V g is lower than the voltage V EV , including keeping the switch S 1 ON, and operating the switches S 3 and S 4 control the charging and the discharging of the inductor; and

operating the four-switch buck-boost converter in a buck-boost mode when the voltages V EV and V g differ less by a predetermined amount, including:

turning the switch S 1 ON at a beginning of a switching cycle, and

turning the switch S 4 ON at an end of the switching cycle.

11 . The method of claim 10 , wherein the operating of the four-switch buck-boost converter in the buck-boost mode includes:

(i) applying trailing edge pulse width modulation (PWM) to the switch S 1 , and

(ii) applying leading edge PWM to the switch S 4 .

12 . The method of claim 10 , wherein the switching cycle includes a region in which the switches S 2 and S 4 are ON, and the switches S 1 and S 3 are OFF.

13 . The method of claim 10 , wherein the switching cycle includes:

a first region in which the switches S 1 and S 3 are ON, and the switches S 2 and S 4 are OFF;

a second region in which the switches S 2 and S 3 are ON, and the switches S 1 and S 4 are OFF; and

a third region in which the switches S 2 and S 4 are ON, and the switches S 1 and S 3 are OFF.

14 . The method of claim 13 , wherein the first region has a longer duration than the third region.

15 . The method of claim 13 , wherein a slope of an inductor current in the third region is substantially zero.

16 . The method of claim 13 , wherein a slope of an inductor current in the first region is positive when V g >V EV .

17 . The method of claim 13 , wherein a slope of an inductor current in the first region is negative when V g <V EV .

18 . The method of claim 10 , wherein the predetermined amount by which the voltages V EV and V g differ in the buck-boost mode is between 20V and 30V.

19 . A charging station comprising:

a source battery;

a four-switch buck-boost converter configured to couple to the source battery and a target battery in an electric vehicle (EV), the converter including: