Brightness-adjustable LED driving circuit

A brightness-adjustable LED driving circuit for driving at least one LED string and adjusting brightness of said at least one LED string, said brightness-adjustable LED driving circuit comprising:

• a brightness-adjustable circuit for receiving an input AC voltage and adjusting the phase of said input AC voltage, thereby generating a brightness adjusting voltage;
• a rectifying and filtering circuit electrically connected to an output terminal of said brightness-adjustable circuit for filtering and rectifying said brightness adjusting voltage into a first DC voltage;
• a power factor correction power conversion circuit electrically connected to said rectifying and filtering circuit and said at least one LED string for generating an output current required for powering said at least one LED string, wherein said power factor correction power conversion circuit comprises a power factor correction controller;
• and
• a detecting and controlling circuit connected to said rectifying and filtering circuit and said power factor correction controller of said power factor correction power conversion circuit for detecting phase data of said brightness adjusting voltage and said output current generated by said power factor correction power conversion circuit, and generating a control signal to said power factor correction controller according to said phase data of said brightness adjusting voltage, so that the magnitude of said output current is changed according to said phase data of said brightness adjusting voltage;
• wherein an input current of said brightness-adjustable LED driving circuit is controlled to have a waveform similar to said brightness adjusting voltage under control of said power factor correction controller of said power factor correction power conversion circuit.