Abstract: A light-emitting diode (LED) driving circuit is configured for driving at least one group of LEDs. The LED driving circuit includes a constant current source, a pulse width modulation (PWM) element, and at least one pulse frequency modulation (PFM) element. The constant current source is configured for generating a current signal with a constant current value; the PWM element is electrically connected to the constant current source and configured for modulating the current signal to generate a PWM signal corresponding to the current signal; the PFM element is electrically connected between the PWM element and the LED and configured for modulating a frequency width of the PWM signal to generate at least one PFM signal for driving the LED.

Abstract: A package structure and methods for forming the package structure are provided. The package structure includes a lead frame having a chip bonding area and a shell surrounding a portion of the lead frame. The shell has an inner surface and an outer surface opposite to the inner surface. A cavity is recessed from the inner surface, and the chip bonding area is exposed from the cavity. The structure further includes a light emitting diode chip disposed over the chip bonding area and a first glue layer disposed in the cavity to cover the light emitting diode chip. A separation film is disposed on the first glue layer in the cavity and a second glue layer disposed on the separation film in the cavity. The second glue layer contains a wavelength conversion material and the first glue layer does not contain any wavelength conversion material.

Abstract: A light-emitting diode (LED) driving circuit is configured for driving at least one group of LEDs. The LED driving circuit includes a constant current source, a pulse width modulation (PWM) element, and at least one pulse frequency modulation (PFM) element. The constant current source is configured for generating a current signal with a constant current value; the PWM element is electrically connected to the constant current source and configured for modulating the current signal to generate a PWM signal corresponding to the current signal; the PFM element is electrically connected between the PWM element and the LED and configured for modulating a frequency width of the PWM signal to generate at least one PFM signal for driving the LED.