An LED drive circuit (10, 30, 50, 60, 70, 80, 90, 100, 110) comprising: a variable constant current source having a current output terminal and a current return terminal; a first LED string (11, 51, 91) having a plurality of series-connected LEDs, the first LED string having a first threshold voltage being the sum of the forward voltage drops of the plurality of series-connected LEDs and configured to emit a first color of light; a second LED string (12, 92) having a plurality of series-connected LEDs, the second LED string having a second threshold voltage being the sum of the forward voltage drops of the plurality of series-connected LEDs and configured to emit a second color of light which is different from the first color of light; and the first LED string (11, 51, 91) and the second LED string (12, 92) are connected in parallel with each other to the variable constant current source, the first threshold voltage of the first LED string (11, 51, 91) is larger than the second threshold voltage of the second LED string (12, 92) so that when a voltage between the current output terminal and the current return terminal is higher than the second threshold voltage but smaller than the first threshold voltage only the second LED string (12, 92) emits light, and characterized in that the LED drive circuit comprises: a current limiting circuit (14, 34, 54, 64, 70x, 94, 114, 114') containing a current sensing element (14b, 34b, 54b, 64b, 73, 94b, 114b, 114e-g) configured to detect a current flowing through the first LED string (11, 51, 91) and a current flowing through the second LED string (12, 92), and a switching element (14a, 71, 94a, 114a) connected in series to the second LED string (12, 92), wherein the current limiting circuit (14, 34, 54, 64, 70x, 94, 114, 114') is configured to control the switching element (14a, 71, 94a, 114a) so that the current flowing through the second LED string (12, 92) is limited based on the current flowing through the current sensing element and when the current detected by the current sensing element (14b, 34b, 54b, 64b, 73, 94b, 95b) is larger than a threshold current only the first LED string (11, 51, 1) emits light. a variable constant current source having a current output terminal and a current return terminal; a first LED string (11, 51, 91) having a plurality of series-connected LEDs, the first LED string having a first threshold voltage being the sum of the forward voltage drops of the plurality of series-connected LEDs and configured to emit a first color of light; a second LED string (12, 92) having a plurality of series-connected LEDs, the second LED string having a second threshold voltage being the sum of the forward voltage drops of the plurality of series-connected LEDs and configured to emit a second color of light which is different from the first color of light; and the first LED string (11, 51, 91) and the second LED string (12, 92) are connected in parallel with each other to the variable constant current source, the first threshold voltage of the first LED string (11, 51, 91) is larger than the second threshold voltage of the second LED string (12, 92) so that when a voltage between the current output terminal and the current return terminal is higher than the second threshold voltage but smaller than the first threshold voltage only the second LED string (12, 92) emits light, and characterized in that the LED drive circuit comprises: a current limiting circuit (14, 34, 54, 64, 70x, 94, 114, 114') containing a current sensing element (14b, 34b, 54b, 64b, 73, 94b, 114b, 114e-g) configured to detect a current flowing through the first LED string (11, 51, 91) and a current flowing through the second LED string (12, 92), and a switching element (14a, 71, 94a, 114a) connected in series to the second LED string (12, 92), wherein the current limiting circuit (14, 34, 54, 64, 70x, 94, 114, 114') is configured to control the switching element (14a, 71, 94a, 114a) so that the current flowing through the second LED string (12, 92) is limited based on the current flowing through the current sensing element and when the current detected by the current sensing element (14b, 34b, 54b, 64b, 73, 94b, 95b) is larger than a threshold current only the first LED string (11, 51, 1) emits light.