An electronic device includes a power supply unit and a main body unit. The power supply unit converts electric power supplied from an external power supply to a DC voltage of a first voltage value to output the voltage to the main body unit and changes, in a case where power supply from the external power supply has been cut off, a value of the DC voltage that it outputs to a second voltage value that is different from the first voltage value. The main body unit executes predetermined termination processing in a case where the value of the DC voltage output by the power supply unit has changed to the second voltage value.

Provided are a power supply circuit, a power supply device and a control method. The power supply circuit includes a primary rectifier unit, a modulation unit, a transformer, a secondary rectifier and filtering unit, a current feedback unit, and a control unit. The power supply circuit removes a liquid electrolytic capacitor at a primary side. Moreover, the control unit may determine a type of a voltage of input alternating current, and set a current limit value in the current feedback unit according to the type of the voltage of the alternating current.

Provided are a power supply circuit, a power supply device and a control method. The power supply circuit includes a primary rectifier unit, a modulation unit, a transformer, a secondary rectifier and filtering unit, a current feedback unit, and a control unit. The power supply circuit removes a liquid electrolytic capacitor at a primary side. Moreover, the control unit may determine a type of a voltage of input alternating current, and set a current limit value in the current feedback unit according to the type of the voltage of the alternating current.

A system for providing power from an AC power supply to an external load. The system includes a current limiter circuit, connected to an input of a switched-mode power supply. The system includes the switched-mode power supply that provides a first voltage signal and a second voltage signal. The system includes a supervisor circuit that is connected to the first output of the switched-mode power supply and coupled to a relay control circuit. The supervisor circuit monitors the first voltage signal and enables the relay control circuit. The relay control circuit provides a first voltage corresponding to the first voltage signal to a first voltage rail and provides a second voltage corresponding to the second voltage signal to a second voltage rail. A relay powered by a connection to the first voltage rail or the second voltage rail connects the AC power supply to an external load.

A modular multilevel converter includes a plurality of submodules, each having at least two electronic switching elements, an electric energy store, two submodule connections, a bypass switch bridging the submodule, and a communication element communicating with a communication apparatus. A method for operating the modular multilevel converter includes ascertaining that the submodules have a defective submodule so that the communication element in the defective submodule does not communicate with the communication apparatus, determining whether a present arm current resulting from an operating point of the modular multilevel converter is below a predetermined threshold value, and generating or amplifying a converter-internal circular current with the defective submodule if the arm current resulting from the operating point is below the predetermined threshold value. A modular multilevel converter is also provided.

An inverter, an inverter system, and a method. The inverter includes an inverter circuit and a controller. When at least one of the following conditions is met, the controller adjusts at least one of parameters including an operating frequency, operating voltage, and operating current of the inverter, to increase a loss of the inverter, where the at least one condition is as follows: an output power of the inverter circuit is lower than a preset power, output current of the inverter circuit is lower than a preset current, operating temperature of the inverter is lower than a preset temperature, or operating humidity of the inverter is higher than a preset humidity. When any one of the foregoing conditions is met, the inverter may increase the operating temperature of the inverter or reduce the operating humidity of the inverter by increasing the loss of the inverter, thereby ensuring inverter operation.

An inverter, an inverter system, and a method. The inverter includes an inverter circuit and a controller. When at least one of the following conditions is met, the controller adjusts at least one of parameters including an operating frequency, operating voltage, and operating current of the inverter, to increase a loss of the inverter, where the at least one condition is as follows: an output power of the inverter circuit is lower than a preset power, output current of the inverter circuit is lower than a preset current, operating temperature of the inverter is lower than a preset temperature, or operating humidity of the inverter is higher than a preset humidity. When any one of the foregoing conditions is met, the inverter may increase the operating temperature of the inverter or reduce the operating humidity of the inverter by increasing the loss of the inverter, thereby ensuring inverter operation.

Fault-protection is provided in electrical devices by redundancy in diodes on diode legs of the bridge rectifier and a fault-protection circuit. The fault-protection circuit is configured: (i) for electrical coupling between a return of input DC power to a step-down switching DC-DC converter and a return rail of rectified DC voltage of the output DC power generated by the bridge rectifier, and is configured to perform opening the switch based on sensing a current fault or voltage fault, or (ii) to sense current from a step-down switching DC-DC converter, a first voltage from the step-down switching DC-DC converter, and/or a second voltage at an output of the step-down switching DC-DC converter, and open the circuit on a fault.

Fault-protection is provided in electrical devices by redundancy in diodes on diode legs of the bridge rectifier and a fault-protection circuit. The fault-protection circuit is configured: (i) for electrical coupling between a return of input DC power to a step-down switching DC-DC converter and a return rail of rectified DC voltage of the output DC power generated by the bridge rectifier, and is configured to perform opening the switch based on sensing a current fault or voltage fault, or (ii) to sense current from a step-down switching DC-DC converter, a first voltage from the step-down switching DC-DC converter, and/or a second voltage at an output of the step-down switching DC-DC converter, and open the circuit on a fault.

A power conversion system includes: a first power converter to perform power conversion between a first AC system and a DC circuit; and a second power converter to perform power conversion between a second AC system and the DC circuit. Each of the first power converter and the second power converter includes a plurality of submodules connected in series. Each of the plurality of submodules includes a plurality of switching elements and a capacitor. A first fundamental frequency of the first AC system is greater than a second fundamental frequency of the second AC system. A first average voltage value of a capacitor in a first submodule included in the first power converter is larger than a second average voltage value of a capacitor in a second submodule included in the second power converter.