CIRCUIT ARRANGEMENT AND LED LAMP COMPRISING THE SAME

• US 20150319818A1
• Filed: 09/17/2013
• Published: 11/05/2015
• Est. Priority Date: 11/06/2012
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: KURT, Ralph, KAHLMAN, Henricus Marius Joseph Maria
• Granted Patent: US 9,474,122 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: H05B 45/395 Linear regulators

Abstract

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.

Claims

1. Circuit arrangement for operating at least one low-power lighting unit with a phase-cut operating voltage from a power supply, comprising

an input device for connection to said power supply having at least a first and second supply terminal,

a two-port power shaping circuit, with at least

a first and a second input terminal, connected with the respective supply terminals of said input device,

a first 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 global current, drawn during operation from the power supply to a predefined minimum load current, and

a damping circuit, connected to said first and second supply connections at a first and a second connection point to attenuate high frequency oscillations in said operating voltage, and

a 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 low-power lighting unit, said lamp driver unit comprising at least

a lamp current controller, configured to set a lamp current of said at least one low-power lighting unit and

a first feedback circuit, configured to provide a first feedback signal, corresponding to the momentary lamp current of said at least one low-power lighting unit, wherein the lamp current controller is connected with said first feedback circuit to control the lamp current in dependence of said feedback signal, so that the lamp current corresponds to a setpoint current, wherein the controllable bleeder circuit is configured to set the global current to the predefine minimum load current independently of the control of the lamp current.

2. Circuit arrangement according to claim 1, wherein said controllable bleeder circuit is activated when the global current is lower than said predefined minimum load current.

3. Circuit arrangement according to claim 1, further comprising a second feedback circuit, configured to determine a second feedback signal, corresponding to the global current and to provide said second feedback signal to the controllable bleeder circuit.

4. Circuit arrangement according to claim 1, wherein said first and/or second feedback circuit is coupled to a series connection of a first and a second current sensing resistor, said series connection being coupled between said second supply terminal and a reference potential.

5. Circuit arrangement according to claim 4, wherein said first feedback circuit is connected to a current sensing point between said first and second current sensing resistors to determine said first feedback signal.

6. Circuit arrangement according to claim 3, wherein the second feedback circuit is connected with said second supply terminal of said input device to determine said second feedback signal, corresponding to the momentary global current.

7. Circuit arrangement according to claim 4, wherein said second output terminal of said power shaping circuit is connected to said reference potential, said first current sensing resistor is connected in series between said second input terminal and said second output terminal, and said second current sensing resistor is arranged in series between said second supply terminal and said second input terminal.

8. Circuit arrangement according to claim 1, wherein the lamp driver unit is connected between said first output terminal of the power shaping circuit and said reference potential.

9. Circuit arrangement according to claim 1, wherein the input device comprises a full-bridge rectifier, wherein a positive output of said rectifier is connected to said first supply terminal and a negative output of said rectifier is connected to said second supply terminal.

10. Circuit arrangement according to claim 1, wherein said damping circuit is adapted, so that upon detection of a dimmer edge, the global current is controlled to an increased edge current, higher than said predefined minimum load current.

11. Circuit arrangement according to claim 1, wherein at least a current flow restrictor is provided in said first supply connection between said first input terminal and said first connection point, so that current flow from the damping circuit to the bleeder circuit is reduced.

12. Circuit arrangement according to claim 1, further comprising a dim level detector, configured to determine a dim level from said phase-cut operating voltage, said dim level detector being connected with said lamp current controller to set the setpoint current in dependence of the determined dim level.

13. LED lamp comprising a circuit arrangement according to claim 1 and at least one LED unit, connected to said lamp driver unit.

14. Lighting system comprising a LED lamp according to claim 13 and a power supply to provide said LED lamp with a phase-cut operating voltage.

15. Method of operating at least one low-power lighting unit with a circuit arrangement, comprising

receiving by an input device a phase-cut operating voltage from a power supply having at least a first and second supply terminal,

connecting at least a first and a second input terminal of a two-port power shaping circuit with the respective supply terminals of said input device,

connecting a first and second output terminal with said input terminals over first and second supply connections,

connecting a controllable bleeder circuit with said first and second input terminals to provide an alternative current path between said input terminals, and a damping circuit, connected to said first and second supply connections to attenuate high frequency oscillations in said operating voltage, and

connecting a lamp driver unit to at least one of the output terminals of the power shaping circuit and being configured for connection to said at least one low-power lighting unit, wherein

the bleeder circuit sets a global current, drawn during operation from the power supply to a predefined minimum load current and

the lamp driver unit controls a lamp current in dependence of a first feedback signal, so that the lamp current corresponds to a setpoint current, wherein the bleeder circuit is configured to set the global current to the predefined minimum load current independently of the control of the lamp current.