The present invention provides a single-segment linear constant-power LED (light-emitting
diode)
driving circuit and a method. The circuit includes a
voltage input module, an LED load, a
power switching tube, a sampling
resistor, an
overvoltage control module which is used for detecting the drain-end
voltage of the
power switching tube, a current control module which is used for limiting the
peak current of the LED load, and a comparison module. According to the single-segment linear constant-power LED (light-emitting
diode)
driving circuit and the method, when input
voltage is larger than the conduction voltage of the LED load, the current control module limits the
peak current, so that a current average value in different input voltage periods can be constant; when the input voltage is larger than a set value, current flowing through the LED load is turned off, and therefore,
power consumption can be decreased; and when the input voltage is smaller than the conduction voltage of the LED load, the LED load is turned off. According to the single-segment linear constant-power LED (light-emitting
diode)
driving circuit and the method of the invention, the control of
average current in
alternating current periods is realized by using a compensation
capacitor, the
peak current is limited, and therefore,
constant power output in a wide input
voltage range is realized; and the turn-off voltage and turn-off slope of the LED are adjusted through an
external resistor, and therefore, the high efficiency of the
system can be realized, and the
electromagnetic interference performance of the
system can be optimized.