Dimming controlling circuit for led

A dimming controlling circuit for LED, comprising:

• a switch configured to connect a main circuit and a power grid;
• a switch-on duration controlling circuit configured to output a switch-on duration controlling signal according to action times of the switch;
• a switch-off controlling circuit configured to compare a voltage of the switch-on duration controlling signal and a voltage of a signal from a terminal of a switch transistor in the main circuit to obtain a comparison result and to output a switch-off controlling signal according to the comparison result;
• a switch-on controlling circuit configured to generate a switch-on controlling signal after a first preset duration since receiving the switch-off controlling signal;
• and
• a logic unit configured to output a switch transistor controlling signal according to the switch-off controlling signal and the switch-on controlling signal.