Bi-directional DC power conversion system
First Claim
1. A bi-directional DC-to-DC power converter comprising:
- a circuit comprising a first power node, a second power node, and an internal node;
first energy storage means coupled between the first power node and ground;
second energy storage means coupled between the second power node and ground;
a first switch coupled between the first power node and the internal node, wherein the first switch permits current flow between the first node and the internal node when in a closed position;
a second switch coupled between the internal node and ground, wherein the second switch permits current flow between the internal node and ground when in a closed position;
inductive means coupled between the second power node and the internal node;
a duty-cycle controller coupled to the first and second switches and to first and second control signals, said controller comprising;
first sensing means for sensing a first voltage, the first sensing means comprising a first voltage-sensing input coupled to the first power node;
second sensing means for sensing a second voltage, the second sensing means comprising a second voltage-sensing input coupled to the second power node;
sense-selection means for alternately selecting the first and second voltage sensing inputs;
a pulse generator which controls the first and second switches; and
feedback means for controlling the pulse generator in response to input received from the one of the first and second voltage-sensing inputs that is selected by the sense-selection means.
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Abstract
A bi-directional DC-to-DC power converter is provided. The power converter has three modes of operation: (1) a step-down mode, in which the power converter converts power in a first direction (such as from a high-voltage power bus to a low-voltage power bus), and (2) a step-up mode, in which the power converter converts power in the opposite direction (such as from the low-voltage power bus to the high-voltage power bus), and (3) an off mode, in which no power is transferred. A single power converter may therefore be used to replace both a conventional step-down converter and a conventional step-up converter. The power converter may provide a battery charge-control functionality, and may be used to charge a battery that may, for example, provide a source of power to a component of an electrical device.
62 Citations
11 Claims
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1. A bi-directional DC-to-DC power converter comprising:
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a circuit comprising a first power node, a second power node, and an internal node;
first energy storage means coupled between the first power node and ground;
second energy storage means coupled between the second power node and ground;
a first switch coupled between the first power node and the internal node, wherein the first switch permits current flow between the first node and the internal node when in a closed position;
a second switch coupled between the internal node and ground, wherein the second switch permits current flow between the internal node and ground when in a closed position;
inductive means coupled between the second power node and the internal node;
a duty-cycle controller coupled to the first and second switches and to first and second control signals, said controller comprising;
first sensing means for sensing a first voltage, the first sensing means comprising a first voltage-sensing input coupled to the first power node;
second sensing means for sensing a second voltage, the second sensing means comprising a second voltage-sensing input coupled to the second power node;
sense-selection means for alternately selecting the first and second voltage sensing inputs;
a pulse generator which controls the first and second switches; and
feedback means for controlling the pulse generator in response to input received from the one of the first and second voltage-sensing inputs that is selected by the sense-selection means. - View Dependent Claims (2, 3, 5, 6, 7, 8, 9, 10, 11)
a sense resistor having a first end coupled to the second power bus and a second end;
a battery coupled between ground and the second end of the sense resistor, thereby forming a junction;
a current-sense input coupled to the junction formed by the battery and the current sense resistor;
first and second connections where the second voltage-sense input and the current-sense input, respectively, connect to the sense resistor such that the voltage between the second voltage-sense input and the current-sense input corresponds to the current through the sense resistor;
current sense means coupled between the second voltage-sense input and the current-sense input for sensing a current through the sense resistor and producing as an output a proxy for the current;
a battery charge controller for determining the amount of current to flow into the battery;
and wherein the feedback means comprises an expanded selection means comprising an input selectable among;
(1) the first voltage;
(2) the second voltage; and
(3) the output of the current sense means.
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3. The power converter of claim 1, wherein the battery comprises an integral safety circuit for automatically disconnecting the battery in response to a signal from the battery charge controller.
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5. A method for use by the power converter of claim 2, wherein the power converter has both step-up and step-down modes of operation, the method comprising steps of:
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(A) selecting one of the step-up and step-down modes of operation;
(B) when the step-down mode of operation is selected, performing a step of determining whether the battery is to be charged in a constant-current mode;
(C) if it is determined in step (B) that the battery is to be charged in the constant-current mode, performing steps of;
(C)(1) selecting the current sense means;
(C)(2) converting power from the first power node to the second power node by maintaining a first feedback loop that varies the duty cycle of the pulse generator to maintain the sensed current at a first constant level and to deliver power to the battery through the sense resistor;
(D) when the step-up mode of operation is selected, performing steps of;
(D)(1) selecting the first voltage; and
(D)(2) converting battery power from the second power node to the first power node by maintaining a second feedback loop that varies the duty cycle of the pulse generator to maintain the first voltage at a second constant level.
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6. The method of claim 5, wherein the step (B) further comprises a step of determining whether the battery is not to be charged, and wherein the method further comprises a step of:
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(E) if it is determined in step (B) that the battery is not to be charged, performing steps of;
(E)(1) selecting the current sense means; and
(E)(2) converting power from the first power node to the second power node by maintaining a third feedback loop that varies the duty cycle of the pulse generator to maintain the sensed current at zero and without delivering power to the battery.
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7. The method of claim 5, wherein the step (B) further comprises a step of determining whether the battery is not to be charged, and wherein the method further comprises a step of:
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(E) if it is determined in step (B) that the battery is not to be charged, performing steps of;
(E)(1) selecting the second voltage sense means;
(E)(2) maintaining the battery in a disconnected state; and
(E)(3) converting power from the first power node to the second power node by maintaining a third feedback loop that varies the duty cycle of the pulse generator to maintain the second voltage at a third constant level.
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8. The method of claim 5, wherein the step (B) further comprises a step of determining whether the battery is to be charged in a constant voltage mode, and wherein the method further comprises a step of:
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(E) if it is determined in step (B) that the battery is to be charged in the constant voltage mode, performing steps of;
(E)(1) selecting the second sensing means; and
(E)(2) converting power from the first power node to the second power node by maintaining a second feedback loop that varies the duty cycle of the pulse generator to maintain the second voltage at a constant charging voltage.
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9. A method for use by the power converter of claim 2, wherein the power converter has both step-up and step-down modes of operation, the method comprising steps of:
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(A) selecting one of the step-up and step-down modes of operation;
(B) when the step-down mode of operation is selected, performing a step of determining whether the battery is to be charged in a constant voltage mode;
(C) if it is determined in step (B) that the battery is to be charged in the constant voltage mode, performing steps of;
(C)(1) selecting the second sensing means; and
(C)(2) converting power from the first power node to the second power node by maintaining a first feedback loop that varies the duty cycle of the pulse generator to maintain the second voltage at a constant charging voltage;
(D) when the step-up mode of operation is selected, performing steps of;
(D)(1) selecting the first voltage; and
(D)(2) converting battery power from the second power node to the first power node by maintaining a second feedback loop that varies the duty cycle of the pulse generator to maintain the first voltage at a first constant level.
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10. The method of claim 9, wherein the step (B) further comprises a step of determining whether the battery is not to be charged, and wherein the method further comprises a step of:
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(E) if it is determined in step (B) that the battery is not to be charged, performing steps of;
(E)(1) selecting the current sense means; and
(E)(2) converting power from the first power node to the second power node by maintaining a third feedback loop that varies the duty cycle of the pulse generator to maintain the sensed current at zero and without delivering power to the battery.
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11. The method of claim 9, wherein the step (B) further comprises a step of determining whether the battery is not to be charged, and wherein the method further comprises a step of:
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(E) if it is determined in step (B) that the battery is not to be charged, performing steps of;
(E)(1) selecting the second voltage sense means;
(E)(2) maintaining the battery in a disconnected state; and
(E)(3) converting power from the first power node to the second power node by maintaining a third feedback loop that varies the duty cycle of the pulse generator to maintain the second voltage at a second constant level.
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4. A method for use by a bi-directional DC-to-DC power converter having both step-down and step-up modes of operation, the power converter comprising a first power node, a second power node, first sensing means for sensing a first voltage at the first power node, second sensing means for sensing a second voltage at the second power node, and a pulse generator having a duty cycle, the method comprising steps of:
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(A) selecting one of the step-up and step-down modes of operation;
(B) when the step-down mode is selected, performing steps of;
(B)(1) selecting the second voltage; and
(B)(2) converting power from the first power node to the second power node by maintaining a first feedback loop that varies the duty cycle of the pulse generator to maintain the second voltage at a first constant level;
(C) when the step-up mode is selected, performing steps of;
(C)(1) selecting the first voltage; and
(C)(2) converting power from the second power node to the first power node by maintaining a second feedback loop that varies the duty cycle of the pulse generator to maintain the first voltage at a second constant level.
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Specification