Direct current link circuit
A device for converting power from a floating source of DC power to a dual direct current (DC) output, the device includes: positive and negative input terminals connectible to the floating source of DC power; and positive and negative, and ground output terminals connectible to the dual DC output that may feed an inverter. The inverter may be either a two or three level inverter. A charge storage device may be connected in parallel to, and charged from, the positive and negative input terminals. A resonant circuit may be also connected between the charge storage device and the dual DC output. The resonant circuit may include an inductor connected in series with a capacitor. The charge storage device may discharge through the resonant circuit by switching through to either the negative output terminal or the positive output terminal.
1. A method for converting power from a floating source of direct current (DC) power to a dual direct current (DC) output, wherein the floating source of DC power includes a positive input terminal and a negative input terminal, the dual DC output includes a positive output terminal, a negative output terminal and a ground terminal, the method including:
charging a charge storage device connected in parallel to the positive input terminal and the negative input terminal; and
discharging the charge storage device by first switching the negative input terminal through a resonant circuit to the negative output terminal during a first half of a period of the resonant circuit and second switching the positive input terminal through the resonant circuit to the positive output terminal during a second half of the period of the resonant circuit.
2. The method of claim 1 , wherein said charging is supplied from the floating source of DC power.
3. The method of claim 1 , wherein said resonant circuit includes an inductor connected in series with a capacitor.
4. The method of claim 1 , the method further including:
during said second switching, providing a positive current path from the positive input terminal to the positive output terminal.
5. The method of claim 1 , further including:
during said first switching, providing a negative return current path from the negative output terminal to the negative input terminal.
6. The method of claim 5 , wherein said negative return current path allows only negative current to flow from said negative input terminal to said negative output terminal.
7. The method of claim 4 , further including:
during said discharging, blocking current flow from said positive output terminal to said positive input terminal.
8. The method of claim 4 , further including:
during said charging, blocking current flow from said positive output terminal to said negative input terminal.
9. The method of claim 4 , wherein said positive current path allows only positive current to flow from said positive input terminal to said positive output terminal.
10. A device for converting power from a floating source of DC power to a dual direct current (DC) output, the device including:
a positive input terminal and a negative input terminal connectible to the floating source of DC power;
a positive output terminal, a negative output terminal and a ground terminal connectible to the dual DC output;
a charge storage device connected in parallel to the positive input terminal and the negative input terminal; wherein said charge storage device is charged from the positive input terminal and the negative input terminal; and
a resonant circuit connected between the charge storage device and the dual DC output, wherein said charge storage device is adapted to discharge through said resonant circuit by switching through to selectively either the negative output terminal or the positive output terminal.
11. The device of claim 10 , further including:
a negative return current path from the negative input terminal to the negative output terminal.
12. The device of claim 11 , wherein the negative return current path includes:
a diode including an anode connected to the negative output terminal and a cathode connected to the negative input terminal.
13. The device of claim 10 , further including:
a switch connected between the positive input terminal and the resonant circuit, wherein said switch when closed discharges said charge storage device through said resonant circuit to the negative output terminal, wherein when said switch is open, said charge storage device is charged from said positive input terminal.
14. The device of claim 13 , wherein said charge storage device is charged from the positive input terminal and the negative input terminal and discharged through said resonant circuit by switching said switch.
15. The device of claim 13 , wherein the switch includes:
an integral diode with a cathode connected to the positive input terminal and an anode connected to the resonant circuit.
16. The device of claim 10 , further including:
a second switch connected between the negative input terminal and the resonant circuit, wherein said second switch when closed discharges said charge storage device through said resonant circuit to the positive output terminal, wherein when said second switch is open, said charge storage device is charged from said positive input terminal.
17. The device of claim 16 , wherein said charge storage device is charged from the positive input terminal and the negative input terminal and discharged through said resonant circuit by switching said second switch.
18. The device of claim 16 , wherein the second switch includes:
a second integral diode with an anode connected to the negative input terminal and a cathode connected to the resonant circuit.
19. The device of claim 10 , further including:
a positive current path from the positive input terminal to the positive output terminal.
20. The device of claim 19 , wherein the positive current path includes:
a diode with a cathode connected to the positive output terminal and an anode connected to the positive input terminal.
21. The device of claim 10 , wherein the positive output terminal, the negative output terminal and the ground terminal feed an inverter, wherein said inverter is one of a two level inverter and a three level inverter.
22. The device of claim 10 , wherein said resonant circuit includes:
a first insulated gate bipolar transistor (IGBT) including:
a first collector attached to the positive input terminal;
a first emitter;
a first diode including a first anode and a first cathode, with said first cathode connected to the first collector and said first anode connected to the first emitter;
a first base attached to a first drive circuit;
a second IGBT including:
a second collector attached to the first emitter to provide a third node;
a second emitter connected to the negative input terminal;
a second diode with a second cathode connected to the second collector and a second anode connected to the second emitter;
a second base attached to a second drive circuit;
a DC output positive terminal;
a second capacitor connected between the DC output positive terminal and electrical ground;
a DC output negative terminal;
a third capacitor connected between the DC output negative terminal and electrical ground; and
an inductor connected between the third node and electrical ground.