Led power supply with small dimming ratio control and control method thereof

An LED driving control circuit for controlling a LED power supply, the control circuit comprising:

• a feedback circuit coupled to the LED power supply, the feedback circuit configured to generate a feedback signal indicative of an output voltage of the LED power supply;
• an enabling circuit coupled to the feedback circuit, the enabling circuit configured to generate an enable signal according to the feedback signal, a first reference signal and a PWM dimming signal;
• and
• a feedback loop control circuit coupled to the feedback circuit, the feedback loop control circuit configured to generate a control signal for controlling ON and OFF of a power switch of the LED power supply according to the feedback signal and the enable signal;
• when the feedback signal is higher than the first reference signal, the enable signal synchronizing with the PWM dimming signal, and when the feedback signal is lower than the first reference signal, the duty cycle of the enable signal being higher than the duty cycle of the PWM dimming signal.

A LED driving method comprising:

• generating a feedback signal indicative of an output voltage of a LED power supply;
• generating an enable signal based on the feedback signal, a first reference signal and a PWM dimming signal, wherein when the feedback signal is higher than the first reference signal, the enable signal synchronizes with the PWM dimming signal, and when the feedback signal is lower than the first reference signal, the duty cycle of the enable signal is larger than the duty cycle of the PWM dimming signal;
• and
• generating a control signal according to the feedback signal only when the enable signal is in an effective state, the control signal controlling a power switch of the LED power supply.