A light-emitting diode (LED) driving circuit and a secondary side controller for controlling the same control an output voltage of the LED driving circuit at a first driving voltage or a second driving voltage. When the output voltage is controlled at the first driving voltage, an LED module driven by the LED driving circuit is in a stably lighting state; and when the output voltage is controlled at the second driving voltage, the output voltage is approximately a threshold voltage of the LED module but higher than zero volt, so that the LED module is close to not emitting light. Therefore, in a dimming operation, the variation of voltage applied across the LED module is smaller than that in the conventional LED driving circuits to thereby protect the LED module against an excessive voltage stress and avoid the problem of inaccurate dimming.