Single inductor DC-DC converter with regulated output and energy harvesting system
An energy harvesting circuit receives an input voltage from a transducer and uses a single inductor operating in a DC-DC converter charging mode to generate charging current at a first output coupled to an energy storage device where a supply voltage is stored. The energy harvesting circuit further receives the supply voltage from the energy storage device and uses the same single inductor operating in a DC-DC converter regulating mode to generate load current at a second output where a regulated load voltage is provided. The energy harvesting circuit switches between the charging mode and the regulating mode in accordance with a discontinuous mode (DCM) control process.
1. An energy harvesting circuit, comprising:
an input configured to receive an input voltage from a transducer;
a first output configured to be coupled to an energy storage device;
a second output configured to be coupled to a load circuit; and
a circuit coupled between the input and the first and second outputs, the circuit configured to use a same single inductor element for generating charging current at the first output and generating load current at the second output, wherein said circuit comprises:
a first switch coupled between said input and a first node configured to be coupled to a first terminal of said single inductor element;
a second switch coupled between said first node and a reference node;
a third switch coupled between a second node configured to be coupled to a second terminal of said single inductor element and the reference node;
a fourth switch coupled between the second node and the first output and
a fifth switch coupled between the first node and the second output without being coupled to the second node.
2. The energy harvesting circuit of claim 1 , wherein said circuit is configured for operation in a charging mode to generate said charging current from said input voltage in order to store a supply voltage on said energy storage device.
3. The energy harvesting circuit of claim 2 , wherein said circuit is further configured for operation in a regulating mode to generate said load current from said supply voltage in order to provide a regulated output voltage to said load circuit.
4. The energy harvesting circuit of claim 1 , further comprising a control circuit configured to actuate said first through fifth switches for selective connection of the single inductor element in a buck-boost mode to charge said energy storage device at the first output to a supply voltage in response to the input voltage.
5. The energy harvesting circuit of claim 4 , wherein said control circuit is further configured to actuate said first through fifth switches for selective connection of the single inductor element in a buck mode to regulate voltage at the second output in response to said supply voltage.
6. The energy harvesting circuit of claim 4 , wherein said control circuit is further configured to actuate said first through fifth switches for selective connection of the single inductor element in a buck-boost mode to regulate voltage at the second output in response to said supply voltage.
7. The energy harvesting circuit of claim 1 , wherein said first output comprises a first energy storage output and a second energy storage output, further comprising a set of switches configured to selectively couple one or more of the first and second energy storage outputs to said single inductor element.
8. The energy harvesting circuit of claim 1 , wherein said circuit further comprises a control circuit configured to selectively actuate said first through fifth switches in both a charging mode and in a regulating mode using said single inductor element.
9. The energy harvesting circuit of claim 8 , wherein the control circuit, in the charging mode, operates in a first switching phase to actuate the first and third switches and then operates in a second switching phase to actuate the second and fourth switches.
10. The energy harvesting circuit of claim 9 , wherein the control circuit, in the regulating mode, operates in a first switching phase to actuate the fourth and fifth switches and then operates in a second switching phase to actuate the third and fifth switches.
11. The energy harvesting circuit of claim 9 , wherein the control circuit, in the regulating mode, operates in a first switching phase to actuate the second and fourth switches and then operates in a second switching phase to actuate the third and fifth switches.
12. The energy harvesting circuit of claim 1 , wherein said input comprises a first input and a second input configured to receive an AC input voltage, with said first switch coupled between said first input and the first node and further comprising:
a sixth switch coupled between said second input and the first node;
a seventh switch coupled between the first input and the reference node; and
an eighth switch coupled between the second input and the reference node.
13. The energy harvesting circuit of claim 12 , further comprising a control circuit configured to control actuation of the first, sixth, seventh and eighth switches to rectify the AC input voltage and provide a DC input voltage at said first node.