Mains Synchronized PWM Dimming

摘要

Driver circuits which reduce or remove flicker of solid state lighting SSL devices, notably at relatively low dimming levels are presented. The driver circuit comprises a power converter to transfer energy from an input of the driver circuit to the SSL device. The energy at the input is derived from an AC mains voltage at a mains frequency. A controller determines a dim level for the SSL device. and operates the power converter continuously in a first operation mode for supplying energy to the SSL device at a first energy level, if the dim level is above a pre-determined dim level threshold. The controller operates the power converter in the first operation mode at a time duration of PWM pulses, and operates the power converter in a second operation mode at a time duration in-between the PWM pulses, if the dim level is below the pre-determined dim level threshold.

主权项

1. A controller for a driver circuit of a solid state lighting, referred to as SSL, device, wherein the driver circuit comprises a power converter configured to transfer energy from an input of the driver circuit to the SSL device; wherein the energy at the input is derived from an AC mains voltage at a mains frequency; wherein the controller is configured to
determine a dim level for the SSL device; if the dim level is above a pre-determined dim level threshold, operate the power converter continuously in a first operation mode for supplying energy to the SSL device at a first energy level; and if the dim level is below the pre-determined dim level threshold, operate the power converter in the first operation mode at a time duration of PWM pulses, and operate the power converter in a second operation mode at a time duration in-between the PWM pulses; wherein in the second operation mode the power converter is operated for supplying energy to the SSL device at a second energy level; wherein the second energy level is lower than the first energy level; and wherein the PWM pulses are synchronized with the AC mains voltage.