Solid-state light-emitting element drive device, lighting system and lighting fixture

摘要

In a conventional example, even if a duty cycle of the burst dimming is changed during an OFF-period of a switching element, current flowing to an LED is maintained constant. On the other hand, in the present embodiment, an accumulated value of ON-periods of a switching element is increased or decreased so as to be linked to a minimum variation width for a duty cycle (a dimming level) of a dimming signal, regardless of a timing of when the duty cycle is changed. Therefore, a lighting system (an LED drive device) according to the present embodiment can change smoothly a light output of a solid-state light-emitting element (a light source) with respect to a change in a duty cycle of the burst dimming while preventing the switching frequency from increasing.

主权项

1. A solid-state light-emitting element drive device, comprising:
a switching source circuit in which a solid-state light-emitting element is connected between output terminals of the switching source circuit, the switching source circuit comprising a switching element; and a control circuit configured to control switching operation of the switching element of the switching source circuit, wherein the switching source circuit further comprises an inductor and a regenerative element, the switching element and the inductor constituting a series circuit, the regenerative element configured to make a regenerative current flow from the inductor, when the switching element is turned off, wherein the control circuit comprises a microcomputer, the control circuit configured to turn on the switching element in response to an ON-period of a drive signal outputted from the microcomputer, the control circuit configured to turn off the switching element in response to an OFF-period of the drive signal, the control circuit configured to interrupt periodically output of the switching source circuit to adjust an average value of current flowing to the solid-state light-emitting element to a value corresponding to a dimming level instructed from outside, and wherein the control circuit is configured to perform the switching operation of the switching element during a conducting period, the control circuit being configured to stop the switching operation of the switching element during a stop period following the conducting period, the control circuit being configured to alternately repeat the conducting period and the stop period, while increasing or decreasing the conducting period and the stop period in response to the dimming level, the control circuit being configured to adjust an accumulated value of ON-periods of the drive signal within the conducting period, in response to the dimming level, and to set a minimum variation width for the conducting period to be shorter than the ON-period.