Power supply circuit

A power supply circuit, comprising:

• a power supplying module, configured to provide a first direct current (DC) voltage, comprising:
• a first rectifying unit, configured to rectify a mains voltage;
• and a first filtering unit, connected to the first rectifying unit and configured to filter a rectified voltage;
• a transformer module, comprising a primary side first winding connected to the power supplying module and a secondary side winding coupled to the primary side first winding;
• a switch module having one end connected to the primary side first winding and the other end connected to a grounding terminal;
• a control module, connected to the switch module, wherein the control module is configured to control the switch module to have different switching frequencies and/or different turning-off times, to enable first pulse voltages with different duty cycles to be formed on the primary side first winding, and second pulse voltages with different duty cycles to be subsequently generated on the secondary side winding;
• and
• a voltage conversion module having an input terminal connected to the secondary side winding and an output terminal connected to a voltage output terminal of the power supply circuit, wherein the voltage conversion module is configured to convert the second pulse voltages with different duty cycles on the secondary side winding into respective DC voltages, and the voltage conversion module comprises a second rectifying unit, configured to rectify a voltage on the secondary side winding;
• and a second filtering unit, connected to the second rectifying unit and configured to filter a rectified voltage;
• an additional filter circuit, constituted by an inductor and a first capacitor, configured to lower a voltage ripper of a second DC voltage output from the voltage output terminal.