Abstract: A three-phase power supply conversion circuit includes rectifier, energy storage, direct-current load, and control modules. The rectifier module includes a three-phase rectifier bridge including three bridge arms connected in parallel to each other, and a bidirectional switch assembly including three bidirectional switches. One ends of the three bidirectional switches are connected to midpoints of the three bridge arms, respectively. The energy storage module is connected to a direct-current output end of the rectifier module and includes first and second capacitors connected in series to each other. Other ends of the three bidirectional switches are connected between the first and second capacitors. The control module is connected to the bidirectional switch assembly and configured to control the bidirectional switches according to phase voltages of a three-phase alternating-current power supply, to maintain a voltage between two ends of the first or second capacitor at a target voltage.

Abstract: An electronic circuit includes a rectifier module and an energy storage module. The rectifier module includes a three-phase rectifier bridge including first, second, and third bridge arms connected in parallel to each other, and a bidirectional switch assembly including first, second, and third bidirectional switches. One ends of the first, second, and third bidirectional switches are connected to midpoints of the first, second, and third bridge arms, respectively. The energy storage module is connected to a direct-current output end of the rectifier module and includes two capacitors connected in series to each other. One of the two capacitors is connected in parallel to a direct-current load. Other ends of the first, second, and third bidirectional switches are connected between the two capacitors.

Abstract: An electric control assembly for an air conditioner is provided. The assembly has an electric control board, a fan driving circuit and a compressor driving circuit. A ground end of the fan driving circuit and a ground end of the compressor driving circuit are connected with two reference grounds of the electric control board in one-to-one correspondence. The assembly also has a switch isolation driving circuit, a first input end of which is connected with a control end of the compressor driving circuit. A first output end of the switch isolation driving circuit is connected with a controlled end of the fan driving circuit. A second input end of the switch isolation driving circuit is connected with a control end of the fan driving circuit. A second output end of the switch isolation driving circuit is connected with a feedback end of the compressor driving circuit.

Abstract: Provided is a multi-level inverter, which includes a first bus capacitor, a second bus capacitor, a third bus capacitor, a fourth bus capacitor, a seventh switch unit, an eighth switch unit, an inverter circuit and a filtering circuit. The first bus capacitor, the second bus capacitor, the third bus capacitor and the fourth bus capacitor are connected between a positive direct current bus and a negative direct current bus in series, and a series point between the second bus capacitor and the third bus capacitor is grounded. The switch transistor of the anti-parallel diode having small on-state resistance is used in the multi-level inverter, thereby reducing power loss of the switch unit in the multi-level inverter and reducing power consumption of the circuit.

Abstract: Provided is a multi-level inverter, which includes a first bus capacitor, a second bus capacitor, a third bus capacitor, a fourth bus capacitor, a seventh switch unit, an eighth switch unit, an inverter circuit and a filtering circuit. The first bus capacitor, the second bus capacitor, the third bus capacitor and the fourth bus capacitor are connected between a positive direct current bus and a negative direct current bus in series, and a series point between the second bus capacitor and the third bus capacitor is grounded. The switch transistor of the anti-parallel diode having small on-state resistance is used in the multi-level inverter, thereby reducing power loss of the switch unit in the multi-level inverter and reducing power consumption of the circuit.

Abstract: An inverter may include an inversion unit for converting a direct current bus voltage into an alternating current voltage, a first snubber unit, and a second snubber unit. The inversion unit may include a first external switch, a first internal switch, a second internal switch, and a second external switch which are connected in series in order between a direct current bus positive voltage terminal and a direct current bus negative voltage terminal. The first snubber unit may be connected between the direct current bus negative voltage terminal and the first internal switch for suppressing voltage stress of the first internal switch. The second snubber unit may be connected between the direct current bus positive voltage terminal and the second internal switch for suppressing voltage stress of the second internal switch.

Abstract: An inverter may include an inversion unit for converting a direct current bus voltage into an alternating current voltage, a first snubber unit, and a second snubber unit. The inversion unit may include a first external switch, a first internal switch, a second internal switch, and a second external switch which are connected in series in order between a direct current bus positive voltage terminal and a direct current bus negative voltage terminal. The first snubber unit may be connected between the direct current bus negative voltage terminal and the first internal switch for suppressing voltage stress of the first internal switch. The second snubber unit may be connected between the direct current bus positive voltage terminal and the second internal switch for suppressing voltage stress of the second internal switch.

Abstract: An optical fiber connector (3) includes an insert body (31), a door (33), a housing (35), a spring member (36) an optical element (37) and a spacer (39). The door includes a protuberance (332) and defines a through hole (331) for receiving a shaft (34). The shaft is held between the insert body and the housing. The door can rotate inwardly into an inserting hole (351) defined by the housing when a fiber plug (4) is inserted the inserting hole. When the fiber plug is pulled out from the housing, the door is rotated to cover the inlet side of the inserting hole due to a spring force applied by the spring member against the door.

Abstract: An optical fiber connector (3) includes an insert body (31), a door (33), a housing (35), a spring member (36) an optical element (37) and a spacer (39). The door includes a protuberance (332) and defines a through hole (331) for receiving a shaft (34). The shaft is held between the insert body and the housing. The door can rotate inwardly into an inserting hole (351) defined by the housing when a fiber plug (4) is inserted the inserting hole. When the fiber plug is pulled out from the housing, the door is rotated to cover the inlet side of the inserting hole due to a spring force applied by the spring member against the door.