Constant-current LED driver circuit and output voltage adjustable circuit and method thereof

摘要

A constant-current Light Emitting Diode (LED) driver circuit is provided, and the circuit includes: an output voltage adjustable circuit and at least one path of LED load, wherein the output voltage adjustable circuit comprises: a switch converting main circuit, an output characteristic parameter sampling circuit, and an output voltage controller. The output voltage controller is used to adjust the output voltage of the switch converting main circuit according to the variation relationship between the sampling signal output by the output characteristic parameter sampling circuit and the output voltage, determine the adjustive direction of the output voltage magnitude of the switch converting main circuit according to the change of the sampling signal, adjust the magnitude of the output voltage of the switch converting main circuit according to the preset step, and finally make the output voltage equal to the voltage of one path of LED load with the highest voltage or the difference between the output voltage and the voltage of one path of LED load voltage with the highest voltage within the predetermined range. The present solution implements reducing the connection complexity and power dissipation on the base of controlling the multi-path constant-current LED.

主权项

1. 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.