US 11,792,903 B2
LED arrangement and method of controlling the same
Henricus Marius Joseph Maria Kahlman, Dongen (NL); and Theo Gerrit Zijlman, Tilburg (NL)
Assigned to SIGNIFY HOLDING B.V., Eindhoven (NL)
Appl. No. 17/770,380
Filed by SIGNIFY HOLDING B.V., Eindhoven (NL)
PCT Filed Oct. 20, 2020, PCT No. PCT/EP2020/079414
§ 371(c)(1), (2) Date Apr. 20, 2022,
PCT Pub. No. WO2021/078697, PCT Pub. Date Apr. 29, 2021.
Claims priority of application No. 19204518 (EP), filed on Oct. 22, 2019.
Prior Publication US 2022/0394834 A1, Dec. 8, 2022
Int. Cl. H05B 45/59 (2022.01); H05B 45/52 (2020.01)
CPC H05B 45/59 (2022.01) [H05B 45/52 (2020.01)] 14 Claims
OG exemplary drawing
 
1. An LED arrangement for connecting to a voltage source, the LED arrangement comprising:
an LED string comprising one or more LEDs and adapted to receive power from the voltage source;
a controllable current source connected in series with the LED string;
a capacitor connected in parallel with the LED string;
a controllable voltage limiter adapted to selectively limit a voltage across the LED string to be no greater than a first voltage level, wherein the first voltage level is lower than a forward voltage of the LED string; and
a controller adapted to control the controllable current source and the controllable voltage limiter responsive to an indicative signal, indicating at least a change in a desired output brightness level of the LED string, wherein the controller is adapted to:
in response to the indicative signal indicating a desire to switch the brightness level of the LED string from a first brightness level to a second brightness level:
during a first time period, control the controllable current source to limit the voltage across the LED string to be no greater than the first voltage level and control the controllable current source to adjust a charge stored by the capacitor; and
after completion of the first time period, control the controllable voltage limiter to stop limiting the voltage across the LED string to be no greater than the first voltage level and control the controllable current source to draw current, from the voltage source, through the LED string so that a brightness of the LED string is at the second brightness level,
wherein the controllable voltage limiter comprises:
a first impedance arrangement, formed of a series of one or more impedance elements, connected in parallel with the LED string;
a second impedance arrangement connected between the first impedance arrangement and a ground or reference voltage, the first and second impedance arrangements being arranged to form a voltage divider between the voltage source and the ground or reference voltage; and
a switching arrangement arranged to controllably bypass one or more of the impedance elements of the first impedance arrangement responsive to the controller, to thereby control an effective impedance of the first impedance arrangement and thereby a voltage across the LED string.