A power supply device comprising: a power converter having a primary side circuit and a secondary side circuit, the primary side circuit having a bridge rectifier circuit and an input capacitor that is coupled between an output of the bridge rectifier circuit and ground; and a power monitor configured to monitor the power converter, the power monitor comprising: a detecting circuit configured to detect an input voltage (W1, P1~P7) of the primary side circuit of the power converter, the input voltage being a DC voltage which is at the output of the bridge rectifier circuit of the primary side circuit; a processing circuit configured to compare a condition of the input voltage (W1, P1~P7) and a predetermined parameter, wherein if the condition of the input voltage (W1, P1~P7) and the predetermined parameter are different, the processing circuit outputs an abnormal signal; and a warning circuit configured to output a warning signal according to the abnormal signal, wherein the processing circuit is configured to determine whether a wave motion difference value of the input voltage is larger than a predetermined voltage difference value, wherein the wave motion difference value of the input voltage represents a peak to peak value of the input voltage, and, if the wave motion difference value of the input voltage is larger than the predetermined voltage difference value, the processing circuit is configured to output the abnormal signal, or the processing circuit is configured to determine whether a waveform unit time variation rate of the input voltage is larger than a predetermined unit time variation rate, wherein if the waveform unit time variation rate of the input voltage is larger than the predetermined unit time variation rate, the processing circuit outputs the abnormal signal. a power converter having a primary side circuit and a secondary side circuit, the primary side circuit having a bridge rectifier circuit and an input capacitor that is coupled between an output of the bridge rectifier circuit and ground; and a power monitor configured to monitor the power converter, the power monitor comprising: a detecting circuit configured to detect an input voltage (W1, P1~P7) of the primary side circuit of the power converter, the input voltage being a DC voltage which is at the output of the bridge rectifier circuit of the primary side circuit; a processing circuit configured to compare a condition of the input voltage (W1, P1~P7) and a predetermined parameter, wherein if the condition of the input voltage (W1, P1~P7) and the predetermined parameter are different, the processing circuit outputs an abnormal signal; and a warning circuit configured to output a warning signal according to the abnormal signal, wherein the processing circuit is configured to determine whether a wave motion difference value of the input voltage is larger than a predetermined voltage difference value, wherein the wave motion difference value of the input voltage represents a peak to peak value of the input voltage, and, if the wave motion difference value of the input voltage is larger than the predetermined voltage difference value, the processing circuit is configured to output the abnormal signal, or the processing circuit is configured to determine whether a waveform unit time variation rate of the input voltage is larger than a predetermined unit time variation rate, wherein if the waveform unit time variation rate of the input voltage is larger than the predetermined unit time variation rate, the processing circuit outputs the abnormal signal. a detecting circuit configured to detect an input voltage (W1, P1~P7) of the primary side circuit of the power converter, the input voltage being a DC voltage which is at the output of the bridge rectifier circuit of the primary side circuit; a processing circuit configured to compare a condition of the input voltage (W1, P1~P7) and a predetermined parameter, wherein if the condition of the input voltage (W1, P1~P7) and the predetermined parameter are different, the processing circuit outputs an abnormal signal; and a warning circuit configured to output a warning signal according to the abnormal signal, wherein the processing circuit is configured to determine whether a wave motion difference value of the input voltage is larger than a predetermined voltage difference value, wherein the wave motion difference value of the input voltage represents a peak to peak value of the input voltage, and, if the wave motion difference value of the input voltage is larger than the predetermined voltage difference value, the processing circuit is configured to output the abnormal signal, or the processing circuit is configured to determine whether a waveform unit time variation rate of the input voltage is larger than a predetermined unit time variation rate, wherein if the waveform unit time variation rate of the input voltage is larger than the predetermined unit time variation rate, the processing circuit outputs the abnormal signal.