LED ILLUMINATION DIMMING CIRCUIT AND LED ILLUMINATION DIMMING METHOD

摘要

An LED illumination dimming circuit includes: a capacitor connected to a first output terminal at one end and connected to a second output terminal at the other end; a coil connected to the other end of the capacitor at one end; a switching element connected to the other end of the coil at one end; a resistor connected to the other end of the switching element at one end and connected to a ground terminal at the other end; a diode connected to a power terminal at the cathode thereof and connected to the other end of the coil at the anode thereof; and a control circuit for controlling the operation of the switching element with a switching control signal on the basis of a dimming signal indicating the dimming rate of the LED element. Dimming is performed continuously in five modes: the maximum current mode in which the LED element emits light with the maximum current; a frequency modulation mode in which dimming is performed with the peak current being lowered; an off-width fixed mode in which the off width is fixed and only the on width is shortened; an off-width modulation mode in which the off width is extended and the on width is shortened; and the minimum current mode in which the LED element emits light with the minimum current.