Current bypass for distributed power harvesting systems using DC power sources
A converter circuit providing multiple current bypass routes between the output leads to provide reliability in a series connection of several converters. If the converter malfunctions due to component failure, the current bypass routes provide a path for the current that views the malfunctioning converter as substantially a short. Diodes prevent backflow into the power source connected to the converter. Redundancy is provided in the bypass portions of the converter circuit that provides alternate parallel paths in case a defective component in one of the paths opens the circuit along that path. In one example, the converter is implemented as a buck plus boost converter where either the buck or the boost portion or both are operative responsive to a controller controlling the switches of both portions. Most of the converter circuit may be implemented in an integrated circuit.
1. A distributed power harvesting system comprising:
a plurality of power sources each providing DC power;
a plurality of converters, each converter comprising input terminals receiving input voltage from, and coupled to, a respective power source from the plurality of power sources;
output terminals for providing an output voltage;
circuitry operatively connected to said input terminals and output terminals, wherein said circuitry receives and converts the input voltage to the output voltage; and
at least two bypass paths adapted for bypassing at least part of the circuitry;
wherein the circuitry comprises
a buck portion providing a stepped down output voltage;
a boost portion connected to the output of said buck portion and adapted to receive said stepped down output voltage, wherein said boost portion converts said stepped down output voltage to provide a stepped up output voltage; and a controller engaging the buck portion and the boost portion, wherein the at least two bypass paths circumvent the buck portion and the boost portion.
2. The distributed power harvesting system of claim 1 , wherein at least one of the at least two bypass paths passes through the buck portion.
3. The distributed power harvesting system of claim 1 , wherein at least one of the at least two bypass paths passes through the boost portion.
4. The distributed power harvesting system of claim 1 , wherein at least one of the bypass paths comprises:
a first current path circumventing the buck portion and the boost portion;
a second current path passing through the buck portion; and
a third current path passing through the boost portion.
5. The distributed power harvesting system of claim 4 ,
wherein the buck portion and the boost portion share an inductive coil;
wherein at least one of the first, second and third, current paths passes through the inductive coil; and,
wherein at least one of the first, second and third, current paths circumvents the inductive coil.
6. The distributed power harvesting system of claim 1 ,
wherein the buck portion and boost portion share an inductor; and
wherein the buck portion comprises a buck switching circuitry and a buck switching bypass path; and
wherein the boost portion comprises a boost switching circuitry and a boost switching bypass path.
7. The distributed power harvesting system of claim 6 , wherein:
the buck switching circuitry comprises a plurality of buck switching elements and the buck switching bypass path comprises a plurality of current paths, each bypassing one of the buck switching elements; and
the boost switching circuitry comprises a plurality of boost switching elements and the boost switching bypass path comprises a plurality of current paths, each bypassing one of the boost switching element.
8. The distributed power harvesting system of claim 1 , wherein at least a portion of the converters is implemented in an integrated circuit.
9. A DC-to-DC power converter for converting an input voltage from a DC power source to an output voltage, the DC-to-DC power converter comprising:
a buck portion providing a stepped down output voltage;
a boost portion connected to the output of said buck circuit and adapted to receive said stepped down output voltage, wherein said boost portion converts said stepped down output voltage to provide a stepped up output voltage;
an inductor coupled to the buck portion and the boost portion;
a controller engaging the buck portion or the boost portion; and a boost bypass path providing a current path adapted for bypassing the boost circuit portion through the buck portion.
10. The DC-to-DC power converter of claim 9 , further comprising:
a first switch of the buck circuit;
a parasitic diode connected across said first switch;
a diode coupled in parallel with said first switch of the buck portion circuit,
wherein a current through the diode and a current through said parasitic diode are parallel.
11. The DC-to-DC power converter of claim 9 , further comprising a buck bypass path providing a current path bypassing the buck portion through the boost portion.
12. The DC-to-DC power converter of claim 11 , further comprising:
a first switch of the boost circuit;
a parasitic diode connected across said first switch;
a diode coupled in parallel with said first switch of the boost portion circuit;
wherein a current through the diode and a current through a parasitic diode are parallel.
13. The DC-to-DC power converter of claim 9 , wherein a portion of the DC-to-DC power converter is implemented in an integrated circuit.
14. The distributed power harvesting system of claim 9 , wherein at least one of the power sources comprises a solar panel.
15. The distributed power harvesting system of claim 9 , wherein at least one of the power sources is a fuel cell.
16. The distributed power harvesting system of claim 9 , wherein each of the plurality of converters further comprises a boost bypass path providing a current path bypassing the boost portion through the buck portion.
17. The distributed power harvesting system of claim 9 , wherein each of the plurality of converters further comprises a buck bypass path providing a current path bypassing the buck portion through the boost portion.
18. A method for providing one or more current bypass routes in a series connection of power cells, the method comprising:
coupling each of the power cells to a corresponding converter;
coupling output leads of the converters in series;
providing a plurality of current bypass routes in each of the converters, wherein the current bypass routes provide routes between the output leads of each of the converters from a negative output lead to a positive output lead and prevent current flow from the positive output lead to the negative output lead;
providing a buck portion in each of the converters;
providing a boost portion in each of the converters; and
selectively activating either the buck portion or the boost portion or both using a controller included in each of the converters,
wherein at least one of the current bypass routes is provided in the buck portion and at least one of the current bypass routes is provided in the boost portion.
19. The method of claim 18 , further comprising:
providing overall bypass routes in each of the converters, the overall bypass route passing outside the buck portion and the boost portion.
20. The method of claim 19 , further comprising:
providing redundancy by forming some of the current bypass routes parallel to portions of other current bypass routes.