Bidirectional DC-DC converter and power supply apparatus with the same
A bidirectional DC-DC converter 10 has smoothing capacitors Cs 1 and Cs 2 , a smoothing reactor Ls, resonant reactors Lr 1 and Lr 2 , and a resonant capacitor Cr, as well as insulated gate bipolar transistors (IGBTs) Q 1 , Q 2 , and Q 3 to which buffer capacitors C 1 , C 2 , and C 3 are connected in parallel and diodes D 1 , D 2 , and D 3 are connected in a back-to-back configuration. After part of the energy stored in the smoothing reactor Ls and/or resonant reactors Lr 1 and Lr 2 draws charges in the buffer capacitor C 3 and is stored in the resonant capacitor Cr, the energy is stored in the resonant reactors Lr 1 and Lr 2 . The energy is used to draw charges in the buffer capacitors C 1 and C 2 , achieving soft switching of IGBTs Q 1 , Q 2 , and Q 3.
1. A bidirectional DC-DC converter including a first smoothing capacitor connected in parallel to a first power supply, a second smoothing capacitor connected in parallel to a second power supply, a first switching device, a second switching device, a smoothing reactor, and a control means for repeatedly storing energy in and releasing energy from the smoothing reactor and turning on and off the first and second switching devices so that electric power is transferred and received between the first and second smoothing capacitors, the bidirectional DC-DC converter comprising:
a resonant reactor;
a storage circuit for storing part of the energy released from the smoothing reactor and/or the resonant reactor in a period in which the smoothing reactor releases the energy it stored; and
a third switching device by which part of the energy stored in the storage circuit is released into the resonant reactor;
wherein the control means operates to turn the third switching device on and off complementarily to the first switching device when the electric power is supplied to the second power supply from the first power supply, and operates to turn the third switching device on and off complementarily to the second switching device when the electric power is supplied to the first power supply from the second power supply so that an output capacitance of the first and second switching device and/or charges stored in a buffer capacitor connected in parallel to the first and second switching device are drawn immediately before the first and second switching device is turned on using the energy stored in the resonant reactor.
2. The bidirectional DC-DC converter according to claim 1 , wherein:
the resonant reactor stores energy by using current for storing energy in and/or discharging energy from the smoothing reactor;
the energy stored in the resonant reactor and/or the energy of the smoothing reactor is transferred to a resonant capacitor in the storage circuit; and
the energy stored in the resonant capacitor is stored in the resonant reactor through the third switching device.
3. The bidirectional DC-DC converter according to claim 1 , wherein the polarity of voltage applied to the resonant reactor in the period in which the smoothing reactor releases the energy it stored is unchanged, regardless of the direction of the power transfer between the first and second power supplies.
4. The bidirectional DC-DC converter according to claim 2 , wherein the resonant capacitor in the storage circuit is connected in series to the third switching device.
5. The bidirectional DC-DC converter according to claim 1 , wherein a diode and/or a parasitic diode is connected in parallel to each of the first to third switching devices in a back-to-back configuration.
6. The bidirectional DC-DC converter according to claim 5 , wherein the control means supplies a turn-on signal to the first to third switching devices connected in parallel to the diode and/or the parasitic diode while the diode and/or the parasitic diode is turned on.
7. The bidirectional DC-DC converter according to claim 1 , wherein the buffer capacitor is connected in parallel to the first, second, and/or third switching device.
8. The bidirectional DC-DC converter according to claim 1 , wherein a first resonant reactor and a second resonant reactor are provided as the resonant reactor, which are respectively connected in series to the first switching device and the second switching device.
9. The bidirectional DC-DC converter according to claim 1 , wherein a first resonant reactor and a second resonant reactor are provided as the resonant reactor, which are respectively connected in series to the first switching device and the second switching device and magnetically coupled with each other.
10. A bidirectional DC-DC converter including a vertical arm formed by interconnecting a terminal of a first switching device and a terminal of a second switching device, a smoothing reactor, one end of which is connected to a connection point between the first and second switching devices, a first smoothing capacitor connected between the other end of the smoothing reactor and the other end of the first switching device and also connected in parallel to a first power supply, a second smoothing capacitor connected between the other end of the smoothing reactor and the other end of the second switching device or between both ends of the vertical arm and also connected in parallel to a second power supply, the bidirectional DC-DC converter comprising:
a resonant reactor connected in series to at least either of the first and second switching devices;
a series connection body including a third switching device and a resonant capacitor;
a resonant circuit formed by including the resonant reactor and the resonant capacitor through the third switching device, and
a current sensor for detecting a direction of a current flowing in the smoothing reactor,
wherein the control means operates to turn the third switching device on and off complementarily to the first switching device when the direction of the current flowing in the smoothing reactor is in one direction so that the electric power is supplied to the second power supply from the first power supply, and operates to turn the third switching device on and off complementarily to the second switching device when the direction of the current flowing in the smoothing reactor is in a direction opposite to said one direction so that the electric power is supplied to the first power supply from the second power supply.
11. A bidirectional DC-DC converter including a vertical arm formed by interconnecting a terminal of a first switching device and a terminal of a second switching device, a smoothing reactor, one end of which is connected to a connection point between the first and second switching devices, and a first smoothing reactor connected between the other end of the smoothing reactor and the other end of the first switching device and also connected in parallel to a first power supply, and a second smoothing reactor connected between both ends of the vertical arm and also connected in parallel to a second power supply, wherein the voltage of the second power supply is higher than a voltage of the first power supply, the bidirectional DC-DC converter comprising:
a resonant reactor connected in series to at least either of the first and second switching devices;
a series connection body including a third switching device and a resonant capacitor;
a resonant circuit formed by including the resonant reactor and the resonant capacitor through the third switching device, and
a current sensor for detecting a direction of a current flowing in the smoothing reactor,
wherein the control means operates to turn the third switching device on and off complementarily to the first switching device when the direction of the current flowing in the smoothing reactor is in one direction so that the electric power is supplied to the second power supply from the first power supply, and operates to turn the third switching device on and off complementarily to the second switching device when the direction of the current flowing in the smoothing reactor is in a direction opposite to said one direction so that the electric power is supplied to the first power supply from the second power supply.
12. A bidirectional DC-DC converter including a vertical arm formed by interconnecting terminal of a first switching device and a terminal of a second switching device, a smoothing reactor, one end of which is connected to a connection point between the first and second switching devices, a first smoothing capacitor connected between the other end of the smoothing reactor and the other end of the first switching device and also connected in parallel to a first power supply, a second smoothing capacitor connected between the other end of the smoothing reactor and the other end of the second switching device and also connected in parallel to a second power supply, the bidirectional DC-DC converter comprising:
a resonant reactor connected in series to at least either of the first and second switching devices;
a series connection body including a third switching device and a resonant capacitor;
a resonant circuit formed by including the resonant reactor and the resonant capacitor through the third switching device, and
a current sensor for detecting a direction of a current flowing in the smoothing reactor,
wherein the control means operates to turn the third switching device on and off complementarily to the first switching device when the direction of the current flowing in the smoothing reactor is in one direction so that the electric power is supplied to the second power supply from the first power supply, and operates to turn the third switching device on and off complementarily to the second switching device when the direction of the current flowing in the smoothing reactor is in a direction opposite to said one direction so that the electric power is supplied to the first power supply from the second power supply.
13. The bidirectional DC-DC converter according to claim 10 , wherein the resonant circuit includes the first and/or second smoothing reactors.
14. The bidirectional DC-DC converter according to claim 10 , wherein a first resonant reactor and a second resonant reactor are provided as the resonant reactor, which are respectively connected in series to the first switching device and the second switching device.
15. The bidirectional DC-DC converter according to claim 10 , wherein a diode and/or a parasitic diode is connected in parallel to each of the first to third switching devices in a back-to-back configuration.
16. The bidirectional DC-DC converter according to claim 10 , wherein a buffer capacitor is connected in parallel to the first, second, or third switching device.
17. The bidirectional DC-DC converter according to claim 15 , wherein the control means supplies a turn-on signal to the first to third switching devices connected in parallel to the diode and/or the parasitic diode while the diode and/or the parasitic diode is turned on.
18. The bidirectional DC-DC converter according to claim 10 , wherein the control means provides a period in which both the first and third switching devices or both the second and third switching devices are turned off together and turning them on and off complementarily.
19. The bidirectional DC-DC converter according to claim 10 , wherein a first resonant reactor and a second resonant reactor are provided as the resonant reactor, which are respectively connected in series to the first switching device and the second switching device and magnetically coupled with each other.
20. The bidirectional DC-DC converter according to claim 10 , further comprising a control means having a current sensor that detects a direction of a current flowing in the smoothing reactor, the control means providing a period in which both the third switching device and the first or second switching device are turned off together and complementarily turning on and off them, either of the first and second switching devices being selected according to the flow direction of the current.