Patent ID: 8866409

Claim:
A constant-current LED driving circuit comprising an output voltage adjustable circuit and at least one LED load, wherein each LED load comprises one or more LEDs and a current-limiting circuit connected in series with the one or more LEDs, the current-limiting circuit is adapted to limit a maximum current in the one or more LEDs connected with the current-limiting circuit, the LED load is connected with the output voltage adjustable circuit via two terminals, and the LED loads are independent from each other; the output voltage adjustable circuit comprises: a switch conversion main circuit for connecting a power supply and outputting an adjustable voltage to the at least one LED load; an output characteristic parameter sampling circuit for sampling an output characteristic parameter of the switch conversion main circuit and outputting a sampled signal of the output characteristic parameter; and an output voltage controller for adjusting an output voltage of the switch conversion main circuit according to a variation relationship between the sampled signal and the output voltage, wherein adjusting the output voltage of the switch conversion main circuit comprises determining a direction for adjusting the output voltage of the switch conversion main circuit according to a variation in the sampled signal and adjusting the output voltage of the switch conversion main circuit at a preset step, so that finally the output voltage is equal to a voltage of one LED load which has the highest voltage or the output voltage has a difference within a predetermined range as compared to the voltage of the LED load which has the highest voltage.