A dimmable switching mode LED driving circuit without phase angle measurement, including: a dimmer circuit for providing a phase-cut AC voltage; a bridge rectifier providing an input voltage by rectifying the phase-cut AC voltage; an electromagnetic interference filtering and energy storing circuit providing a line voltage according to the input voltage; a switching power converter converting the line voltage to an output current for an LED load under a control of a driving voltage; and a control unit using at least one feedback signal to perform a pulse width modulation operation to determine an on time for the switching voltage; wherein the control unit includes an on-time controller and a timer, the on-time controller determining the on time according to the at least one feedback signal, and the timer setting a maximum limit on the on time.