LED dimming circuit

The invention relates to an LED dimming circuit comprising a current sampling module, an I-V conversion module, a PWM (Pulse Width Modulation) comparer, a power driving module and a power MOS (Metal Oxide Semiconductor) tube which are sequentially connected in series, wherein the input end of the PWM comparer is connected to an external pin and receives a reference voltage signal, and the output end of the PWM comparer feeds back a hystersis control signal to the I-V conversion module. According to the LED dimming circuit disclosed by the invention, analog dimming and PWM dimming are simultaneously realized through the PWM comparer; as for the analog dimming, errors generated by non-infinite operational amplifier gain and process mismatching in the prior art are eliminated because a pin ADJ of an LED illumination driving chip is directly connected with the input end of the PWM comparer so that the analog dimming is more accurate; and as for the PWM dimming, the linearity and the accuracy of the PWM dimming are better because the delay of an operational amplifier does not exist. The invention has the advantages of simplicity, reliability, high accuracy, chip area saving and production cost reduction.