Circuit arrangement and led lamp comprising the same

摘要

A circuit arrangement for operating at least one low-power lighting unit with a phase-cut operating voltage from a power supply is disclosed, which circuit arrangement comprises a serial setup of an input device (6), a two-port power shaping circuit (7, 7′, 7″) and a lamp driver unit (8, 8′, 8″). The power shaping circuit (7, 7′, 7″) comprises at least a bleeder (13) and a damping circuit (14). While the bleeder circuit (13) provides an alternative current path to set a global current, drawn during operation from the power supply to a predefined minimum load current, the damping circuit (14) serves to attenuate high frequency oscillations in said operating voltage. To enhance dimmer compatibility and simultaneously provide a cost-efficient circuit setup, a first and a second feedback circuit (18, 25) is provided, allowing to control the bleeder circuit (13) and the lamp driver unit (8, 8′, 8″) according to a two-point control.

主权项

1. An apparatus configured to supply a lamp current to at least one lighting unit, the apparatus comprising:
an input device for connection to a power supply to receive a phase-cut operating voltage from the power supply, the input device having at least a first supply terminal and a second supply terminal a two-port power shaping circuit, including:
a first input terminal and a second input terminal, connected with the respective supply terminals of said input device,a first output terminal and second output terminal, connected with said input terminals over first and second supply connections,a controllable bleeder circuit, connected with said first and second input terminals to provide an alternative current path between said input terminals and being configured to set a level of a total current drawn from the power supply during operation to be at least a predetermined minimum load current, anda damping circuit, connected to said first and second supply connections at a first connection point and a second connection point to attenuate high frequency oscillations in the phase-cut operating voltage; anda lamp driver unit, connected to at least one of the output terminals of the power shaping circuit and being configured for connection to said at least one lighting unit, said lamp driver unit comprising:a lamp current controller, configured to set the lamp current of said at least one lighting unit, anda first feedback circuit, configured to provide a first feedback signal, corresponding to the momentary lamp current of said at least one lighting unit, wherein the lamp current controller is connected with said first feedback circuit to control the lamp current in dependence of said first feedback signal, so that the lamp current corresponds to a predetermined setpoint current, and wherein the controllable bleeder circuit is configured to set the level of the total current drawn from the power supply during operation to be at least the predetermined minimum load current independently of the control of the lamp current.