DC-to-DC converter and configurable output magnitude and polarity
A DC-to-DC converter includes an input configured to receive a DC input voltage, an output having a positive rail and a negative rail, wherein the negative rail is configured for connection to a negative terminal of the DC input voltage source, a bypass capacitor having first end connected to a first node and a second end connected to a second node and two coupled inductors, the two coupled inductors including a first inductor that has a first end connected to the input and a second end connected to the first end of the bypass capacitor at the first node, the two coupled inductors also including a second inductor that has a first end connected to the second end of the bypass capacitor at the second node and a second end connected to a third node. The converter includes switches that allow control of the polarity and magnitude of the output.
1 . A DC-to-DC converter, the converter comprising:
an input configured to receive a DC input voltage from a DC voltage source;
an output having a positive rail and a negative rail, wherein the negative rail is configured for connection to a negative terminal of the DC input voltage source;
a bypass capacitor having first end connected to a first node and a second end connected to a second node;
two coupled inductors, the two coupled inductors including a first inductor that has a first end connected to the input and a second end connected to the first end of the bypass capacitor at the first node, the two coupled inductors also including a second inductor that has a first end connected to the second end of the bypass capacitor at the second node and a second end connected to a third node;
a first switch connected between the first node and the negative rail;
a second switch connected between the second node and the positive rail;
a third switch connected between the second node and the negative rail;
a fourth switch connected between the third node and the negative rail;
a fifth switch connected between the third node and the positive rail; and
a controller that is configured to selectively operate the first, second, third, fourth and fifth switches based on a desired magnitude and polarity of a voltage at the output;
wherein the controller is configured to operate in an inverting mode at a switching frequency having a period,
wherein in the inverting mode, the second and fourth switches are open, the fifth switch is closed and the first and third switches operate in a complementary manner during the period.
2 . The converter of claim 1 , wherein a portion of the period where the first switch is closed defines a duty cycle D.
3 . The converter of claim 2 , wherein when D is less than 0.5 a voltage at the input is stepped-down to a lower voltage at the output and when D is greater than 0.5 the voltage at the input is stepped-up to a higher voltage at the output.
4 . The converter of claim 3 , wherein a relationship between the DC input voltage (V in ) and the output voltage (V out ) is:
V
out
=
-
V
in
D
1
-
D
.
5 . A method of operating a power converter as recited in claim 1 , the method comprising:
determining the power converter is to operate in the inverting mode; and
operating the power converter at the switching frequency.
6 . The method of claim 5 , wherein in the inverting mode, the second and fourth switches are open and the fifth switch is closed and the first and third switches operate in a complementary manner during the period.
7 . The method of claim 6 , wherein a portion of the period where the first switch is closed defines a duty cycle D and wherein when D is less than 0.5 a voltage at the input is stepped-down to a lower voltage at the output and when D is greater than 0.5 the voltage at the input is stepped-up to a higher voltage at the output.
8 . The method of claim 7 , wherein the relation between the DC input voltage (V in ) and the output voltage (V out ) is:
V
out
=
-
V
in
D
1
-
D
.
9 . The method of claim 5 , wherein after determining, then determining that the power converter is to operate in a non-inverting mode, wherein in the non-inverting mode, the third and fifth switches are open and the fourth switch is closed and the first and second switches operate in a complementary manner during the period.
10 . The method of claim 9 , wherein a portion of the period where the first switch is closed defines a duty cycle D and wherein when D is less than 0.5 a voltage at the input is stepped-down to a lower voltage at the output and when D is greater than 0.5 the voltage at the input is stepped-up to a higher voltage at the output.
11 . The method of claim 10 , wherein a relationship between the DC input voltage (V in ) and the output voltage (V out ) is:
V
out
=
V
in
D
1
-
D
.
12 . A DC-to-DC converter, the converter comprising:
an input configured to receive a DC input voltage from a DC voltage source;
an output having a positive rail and a negative rail, wherein the negative rail is configured for connection to a negative terminal of the DC input voltage source;
a bypass capacitor having first end connected to a first node and a second end connected to a second node;
two coupled inductors, the two coupled inductors including a first inductor that has a first end connected to the input and a second end connected to the first end of the bypass capacitor at the first node, the two coupled inductors also including a second inductor that has a first end connected to the second end of the bypass capacitor at the second node and a second end connected to a third node;
a first switch connected between the first node and the negative rail;
a second switch connected between the second node and the positive rail;
a third switch connected between the second node and the negative rail;
a fourth switch connected between the third node and the negative rail;
a fifth switch connected between the third node and the positive rail; and
a controller that is configured to selectively operate the first, second, third, fourth and fifth switches based on a desired magnitude and polarity of a voltage at the output;
wherein the controller is configured to operate in a non-inverting mode at a switching frequency having a period;
wherein in the non-inverting mode, the third and fifth switches are open, the fourth switch is closed and the first and second switches operate in a complementary manner during the period.
13 . The converter of claim 12 , wherein a portion of the period where the first switch is closed defines a duty cycle D.
14 . The converter of claim 13 , wherein when D is less than 0.5 a voltage at the input is stepped-down to a lower voltage at the output and when D is greater than 0.5 the voltage at the input is stepped-up to a higher voltage at the output.
15 . The converter of claim 14 , wherein a relationship between the DC input voltage (V in ) and the output voltage (V out ) is:
V
out
=
V
in
D
1
-
D
.