A calculation circuit, comprising: an output current detection circuit, coupled to a power conversion circuit to detect an output current of the power conversion circuit; an output voltage detection circuit, coupled to the power conversion circuit to detect an output capacitor voltage (V Co) of an output capacitor of the power conversion circuit; a processor, coupled to the output current detection circuit and the output voltage detection circuit, calculating output power (Po) of the power conversion circuit by using the output current and the output capacitor voltage (V Co), wherein the processor calculates a current output capacitor value (C out) of the power conversion circuit by using the output capacitor voltage (V Co), the output power (Po), and first time information, and triggers a notification based on the current output capacitor value (C out); an input voltage detection circuit, coupled to the processor and coupling to the power conversion circuit to detect an input capacitor voltage (V Cin) of an input capacitor of the power conversion circuit, wherein, when the input voltage detection circuit detects that the input capacitor voltage (V Cin) steps down, it is determined that a power-off occurs; characterized in further comprising an input current detection circuit, coupled to the processor and coupling to the power conversion circuit to detect an input current (I IN) flowing through a power switch of the power conversion circuit to the input capacitor of the power conversion circuit, wherein, when the input current detection circuit detects that the input current (I IN) turns to 0, due to the power switch being turned off, it is determined that a power-off occurs. an output current detection circuit, coupled to a power conversion circuit to detect an output current of the power conversion circuit; an output voltage detection circuit, coupled to the power conversion circuit to detect an output capacitor voltage (V Co) of an output capacitor of the power conversion circuit; a processor, coupled to the output current detection circuit and the output voltage detection circuit, calculating output power (Po) of the power conversion circuit by using the output current and the output capacitor voltage (V Co), wherein the processor calculates a current output capacitor value (C out) of the power conversion circuit by using the output capacitor voltage (V Co), the output power (Po), and first time information, and triggers a notification based on the current output capacitor value (C out); an input voltage detection circuit, coupled to the processor and coupling to the power conversion circuit to detect an input capacitor voltage (V Cin) of an input capacitor of the power conversion circuit, wherein, when the input voltage detection circuit detects that the input capacitor voltage (V Cin) steps down, it is determined that a power-off occurs; characterized in further comprising an input current detection circuit, coupled to the processor and coupling to the power conversion circuit to detect an input current (I IN) flowing through a power switch of the power conversion circuit to the input capacitor of the power conversion circuit, wherein, when the input current detection circuit detects that the input current (I IN) turns to 0, due to the power switch being turned off, it is determined that a power-off occurs.