Light emitting diode driving method and driving circuit

A light emitting diode driving circuit, comprising:

• a counting circuit, receiving the first pulse width modulation signal and counting during a frequency cycle of the first pulse width modulation signal to generate a frequency cycle count and a duty cycle count of the first pulse width modulation signal, wherein the first pulse width modulation signal determines brightness of a light emitting diode;
• a calculating circuit, calculating a duty cycle of the first pulse width modulation signal during the frequency cycle, according to the frequency cycle count and the duty cycle count;
• a pulse width modulation signal generating circuit, generating a second pulse width modulation signal by implementing an algorithm according to the frequency cycle count and the duty cycle count;
• a driving current setting circuit, electrically coupled to the calculating circuit and the pulse width modulation signal generating circuit;
• and
• a dimming mode selecting circuit, determining relative relationship of magnitude of the duty cycle of the first pulse width modulation signal and a preset threshold value, and determining whether the second pulse width modulation signal is provided to the driving current setting circuit according to the relative relationship to selectively enable the light emitting diode to work with a pulse width modulation dimming mode with which a duty cycle of a driving current for the light emitting diode is set according to the second pulse width modulation signal, or a direct current dimming mode.

A light emitting diode driving method, comprising steps of:

• obtaining a duty cycle of an initial pulse width modulation signal which determines brightness of the light emitting diode;
• when the duty cycle of the initial pulse width modulation signal is less than a preset threshold value, respectively setting a duty cycle of a driving current for the light emitting diode and a current value of the driving current during the set duty cycle to be D %/T and Iset×T, wherein D % is the value of the duty cycle of the driving current, T is the threshold value, 0<T<1, Iset is a preset maximum gray-scale current of the light emitting diode;
• and
• when the duty cycle of the initial pulse width modulation signal is no less than the preset threshold value, respectively setting the duty cycle of the driving current and the current value of the driving current during the duty cycle of the driving current to be 100% and Iset×D %.