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. <EOS>