A power supply circuit, comprising: a primary rectifier unit, configured to perform rectification on input alternating current to output a first voltage having a periodically changing voltage value; a modulation unit, configured to directly modulate the first voltage having the periodically changing voltage value after the primary rectification to generate a second voltage; a transformer, configured to generate a third voltage based on the second voltage; a secondary rectifier and filtering unit, configured to perform rectification and filtering on the third voltage to generate a first current, wherein the secondary rectifier and filtering unit comprises a secondary rectifier unit and a secondary filtering unit, wherein the secondary filtering unit comprises one or more solid capacitors, wherein the first current has a first waveform with a current value periodically changing, wherein the first waveform has peaks and valleys and is not a complete pulsating waveform, wherein neither peaks nor valleys of the first waveform reach peaks and valleys of the pulsating waveform, wherein the valleys do not reach zero points and the peaks do not reach the peaks of the pulsating waveform; and a control unit, configured to adjust the first current to generate an output current of the power supply circuit, the output current having a second waveform with a current value periodically changing, and each period of the second waveform containing a duration in which the current value is 0, wherein the duration in which the current value is 0 is a part or all of the duration in which the first waveform is at the valley. a primary rectifier unit, configured to perform rectification on input alternating current to output a first voltage having a periodically changing voltage value; a modulation unit, configured to directly modulate the first voltage having the periodically changing voltage value after the primary rectification to generate a second voltage; a transformer, configured to generate a third voltage based on the second voltage; a secondary rectifier and filtering unit, configured to perform rectification and filtering on the third voltage to generate a first current, wherein the secondary rectifier and filtering unit comprises a secondary rectifier unit and a secondary filtering unit, wherein the secondary filtering unit comprises one or more solid capacitors, wherein the first current has a first waveform with a current value periodically changing, wherein the first waveform has peaks and valleys and is not a complete pulsating waveform, wherein neither peaks nor valleys of the first waveform reach peaks and valleys of the pulsating waveform, wherein the valleys do not reach zero points and the peaks do not reach the peaks of the pulsating waveform; and a control unit, configured to adjust the first current to generate an output current of the power supply circuit, the output current having a second waveform with a current value periodically changing, and each period of the second waveform containing a duration in which the current value is 0, wherein the duration in which the current value is 0 is a part or all of the duration in which the first waveform is at the valley.