Led driver, led lighting system and operating method thereof

An LED lighting system, comprising:

• an LED light source;
• and
• an LED driver, driving the LED light source, and comprising:
• a strobe circuit, configured to generate a low-frequency modulation signal;
• and
• a DC-DC converter, coupled to the strobe circuit and the LED light source, and configured to provide an adjustable operating current to the LED light source according to a DC signal and the low-frequency modulation signal, wherein the operating current comprises a DC current signal and a low-frequency AC current signal corresponding to the DC signal and the low-frequency modulation signal respectively,
• wherein a frequency of the low-frequency AC current signal is between 25 Hz and 100 Hz, and a current ripple factor, equaling a difference of a maximum value and a minimum value of the operating current divided by a sum of the maximum value and the minimum value, is less than 8%.

An operating method of an LED (light-emitting diode) driver for driving an LED light source, comprising:

• generating a low-frequency modulation signal with a strobe circuit of the LED driver;
• and
• providing an adjustable operating current to the LED light source according to a DC signal and the low-frequency modulation signal with a DC-DC converter of the LED driver coupled to the strobe circuit;
• wherein the operating current comprises a DC current signal and a low-frequency AC current signal corresponding to the DC signal and the low-frequency modulation signal respectively;
• a frequency of the low-frequency AC current signal is between 25 Hz and 100 Hz;
• and a current ripple factor, equaling a difference of a maximum value and a minimum value of the operating current divided by a sum of the maximum value and the minimum value, is less than 8%.