Patent ID: 7675240

Claim:
A light emitting diode (LED) circuit having even current comprising: multiple LED strings being connected to an external power source, and each LED string comprising multiple LEDs connected in series together and having a power terminal connecting to the external power source; and a driving terminal; a current equalizing integrated circuit (IC) comprising a multi-transistor current mirror and having multiple driving pins being connected respectively to the driving terminals of the LED strings; and a bias pin being connected to the external power source through a bias resistor to obtain a bias voltage; and a voltage compensation module being connected between the power terminals of the LED strings and the external power source and having a threshold voltage value corresponding to an active voltage of each transistor in the current equalizing IC; and multiple input terminals being connected respectively to the driving pins of the current equalizing IC to obtain feedback voltages on the driving pins of the current equalizing IC to allow the voltage compensation module raising and sending the voltage obtaining from the external power source to the LED strings when the voltage compensation module determines any of the feedback voltages is lower than the threshold voltage value wherein the voltage compensation further comprises a feedback input unit being connected to the driving pins of the current equalizing IC and the external power source to obtain the feedback voltages and a feedback reference voltage; and a boosting compensation unit being connected to the external power source, the feedback input unit and the power terminals of the LED strings to obtain an input voltage, an operating voltage and the feedback reference voltage, send the voltage obtained from the external power source to the LED strings when the voltage compensation module determines all of the feedback voltages are lower than the threshold voltage value and raise and send the voltage obtaining from the external power source to the LED strings when the voltage compensation module determines any of the feedback voltages is lower than the threshold voltage value; and wherein the feedback input unit further comprises multiple diodes connected respectively to the driving pins of the current equalizing IC, and each diode having a negative terminal being connected respectively to the driving pins; and a positive terminal; a first resistor having a first end being connected to the positive terminals of the diodes; and a second end; and a second resistor having a first end being connected to the external power source to obtain the feedback reference voltage; and a second end being connected to the second end of the first resistor at a node.