Patent ID: 8183795

Claim:
A LED current-controlling circuit for receiving a pulse width modulation voltage and outputting a first current having a specified DC current level required to power a first LED string of multiple LED strings, said LED current-controlling circuit comprising: a first magnetic amplifier having a terminal connected to an input terminal of said LED current-controlling circuit and the other terminal connected to said first LED string; a first current detecting circuit connected to said first LED string in series for detecting said first current flowing through said first LED string; a first magnetic amplifier controller connected to said first current detecting circuit for controlling on/off statuses of said first magnetic amplifier; and a first diode having a terminal connected to an output terminal of said first magnetic amplifier and said first LED string and the other terminal connected to said first magnetic amplifier controller, wherein said first magnetic amplifier controller controls on/off statuses of said first magnetic amplifier according to the magnitude of said first current, thereby maintaining said first current at said specified DC current level; wherein the magnitude of said first current flowing through said first LED string is equal to the magnitude of the current flowing through at least one of the other LED strings.