Single-phase and three-phase compatible conversion circuit and vehicle-mounted charger

1. A single-phase and three-phase compatible conversion circuit, comprising:

an EMC module,

a PFC module,

a switch K 1 , and

a control module,

wherein the EMC module is connected between lines A, B, C and N of a power grid and the PFC module; three lines A 1 , B 1 and C 1 are led out from the EMC module and are connected with the PFC module; the three lines A 1 , B 1 and C 1 are respectively connected to a set virtual midpoint through capacitors CX 1 , CX 2 and CX 3 ; and the virtual midpoint is connected to a bus midpoint of the PFC module through the switch K 1 ; and the control module is used for detecting a power grid input signal and controlling the state of the switch K 1 according to the type of the power grid input signal.

2. The single-phase and three-phase compatible conversion circuit according to claim 1 , wherein the virtual midpoint is grounded through a capacitor CY 1 .

3. The single-phase and three-phase compatible conversion circuit according to claim 1 , wherein when the power grid is connected to three-phase power, the control module controls the switch K 1 to be turned on; and when the power grid is connected to single-phase power, the control module controls the switch K 1 to be turned off.

4. The single-phase and three-phase compatible conversion circuit according to claim 1 , wherein the EMC module comprises an EMC filter and a switching device; the EMC filter is composed of filter units that filter the lines A, B, C, and N respectively; and the switching device is composed of switches arranged among the lines A, B, C, and N and used for switching the state of the EMC filter.

5. The single-phase and three-phase compatible conversion circuit according to claim 4 , wherein when the power grid is connected to three-phase power, the switching device sets the EMC filter to a state of filtering the lines A, B, C, and N of the power grid; and when the power grid is connected to single-phase power, the switching device sets the EMC filter to a two-way filtering state.

6. The single-phase and three-phase compatible conversion circuit according to claim 1 , wherein K 1 is a single-pole double-throw switch; when the power grid is connected to three-phase power, the control module controls the switch K 1 to turn on the virtual midpoint and the bus midpoint of the PFC module; and when the power grid is connected to single-phase power, the line N of the power grid is output through one of the three lines A 1 , B 1 , and C 1 led out from the EMC module, and the control module controls the switch K 1 to turn on the virtual midpoint and the N line output from the EMC module.

7. A single-phase and three-phase compatible conversion circuit, comprising an EMC module, a PFC module, a single-pole double-throw switch K 2 and a control module, wherein the EMC module is connected between lines A, B, C, and N of a power grid and the PFC module; three lines A 1 , B 1 and C 1 are led out from the EMC module and are connected with the PFC module; the three lines A 1 , B 1 and C 1 are respectively connected to a set virtual midpoint through capacitors CX 1 , CX 2 and CX 3 ; and the virtual midpoint is connected to a fixed contact of the single-pole double-throw switch K 2 ; a serial fly-wheeling device is also arranged between buses of the PFC module; a midpoint of the serial free-wheeling device is connected to a line N 1 led out from the EMC module; a first dynamic contact of the single-pole double-throw switch K 2 is connected to a bus midpoint of the PFC module; a second dynamic contact of the single-pole double-throw switch K 2 is connected to the line N 1 led out from the EMC module; and the control module is used for detecting a grid input signal and controlling the state of the single-pole double-throw switch K 2 according to the type of the grid input signal.

8. The single-phase and three-phase compatible conversion circuit according to claim 7 , wherein when the power grid is connected to three-phase power, the control module controls the first dynamic contact of the single-pole double-throw switch K 2 to be turned on; and when the power grid is connected to single-phase power, the control module controls the second dynamic contact of the single-pole double-throw switch K 2 to be turned on.

9. The single-phase and three-phase compatible conversion circuit according to claim 7 , wherein the EMC module comprises an EMC filter and a switching device; the EMC filter is composed of filter units that filter the lines A, B, C, and N respectively; and the switching device is composed of switches arranged among the lines A, B, C, and N and used for switching the form of the EMC filter.

10. The single-phase and three-phase compatible conversion circuit according to claim 7 , wherein when the power grid is connected to three-phase power, the switching device sets the EMC filter to a form of filtering the lines A, B, C, and N of the power grid; and when the power grid is connected to single-phase power, the switching device controls a filter unit on the line A of the filter to be connected to the PFC module alone, or controls the filter unit on the line A of the filter to be connected in parallel with a filter unit on the line B or a filter unit on the line C and then connected to the PFC module, or controls the filter unit on the line A of the filter to be connected in parallel with the filter unit on the line B and the filter unit on the line C and then connected to the PFC module.

11. The single-phase and three-phase compatible conversion circuit according to claim 7 , wherein the serial free-wheeling device comprises at least two diodes connected in series or at least two transistors connected in series.

12. The single-phase and three-phase compatible conversion circuit according to claim 11 , wherein when the power grid is connected to three-phase power, the control module controls the first dynamic contact of the single-pole double-throw switch K 2 to be turned on; and when the power grid is connected to single-phase power, the control module controls the second dynamic contact of the single-pole double-throw switch K 2 to be turned on.

13. The single-phase and three-phase compatible conversion circuit according to claim 11 , wherein the EMC module comprises an EMC filter and a switching device; the EMC filter is composed of filter units that filter the lines A, B, C, and N respectively; and the switching device is composed of switches arranged among the lines A, B, C, and N and used for switching the form of the EMC filter.

14. The single-phase and three-phase compatible conversion circuit according to claim 11 , wherein when the power grid is connected to three-phase power, the switching device sets the EMC filter to a form of filtering the lines A, B, C, and N of the power grid; and when the power grid is connected to single-phase power, the switching device controls a filter unit on the line A of the filter to be connected to the PFC module alone, or controls the filter unit on the line A of the filter to be connected in parallel with a filter unit on the line B or a filter unit on the line C and then connected to the PFC module, or controls the filter unit on the line A of the filter to be connected in parallel with the filter unit on the line B and the filter unit on the line C and then connected to the PFC module.

15. A vehicle-mounted charger, comprising the single-phase and three-phase compatible conversion circuit according to claim 1 .

16. A vehicle-mounted charger, comprising the single-phase and three-phase compatible conversion circuit according to claim 7 .