LED DRIVER WITH HIGH DIMMING COMPATIBILITY WITHOUT THE USE OF BLEEDERS

• US 20150264758A1
• Filed: 03/17/2014
• Published: 09/17/2015
• Est. Priority Date: 03/17/2014
• Status: Active Grant

• Current Assignee: LEDVANCE LLC (MLS Co. Ltd.)
• Original Assignee: TerraLUX Incorporated
• Inventors: McDougle, Anthony N.
• Granted Patent: US 9,277,611 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 5/257 using semiconductor devices only
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/385 using flyback topology

Abstract

A switching converter detects when a dimmer circuit supplying power to the switching converter changes from a conducting state to a nonconducting state or from a nonconducting state to a conducting state; an equivalent input resistance of the switching converter is changed to a first, higher value when the dimmer circuit is in the conducting state and to a second, lower value when the dimmer circuit is in the nonconducting state, thereby drawing a minimum current from the dimmer circuit while the dimmer circuit is in the nonconducting state.

Claims

1. A circuit for controlling a switching converter, the circuit comprising:

an input voltage or phase analyzer for detecting when a dimmer circuit supplying power to the switching converter changes from a conducting state to a nonconducting state or from a nonconducting state to a conducting state; and

a pulse-width-modulating generator for changing an equivalent input resistance of the switching converter to a first, higher value when the dimmer circuit is in the conducting state and to a second, lower value when the dimmer circuit is in the nonconducting state, thereby drawing a minimum current from the dimmer circuit while the dimmer circuit is in the nonconducting state.

2. The circuit of claim 1, further comprising a light-emitting diode that receives an output current generated by the switching converter and is illuminated thereby.

3. The circuit of claim 1, wherein the pulse-width-modulating generator changes the equivalent input resistance by changing a frequency or duty cycle of an output control signal that controls switching characteristics of the switching converter.

4. The circuit of claim 1, wherein a power drawn from the dimming circuit is approximately equal to a power drawn by a switching converter having a constant equivalent resistance.

5. The circuit of claim 1, further comprising a feedback analyzer for detecting a current flowing through a light-emitting diode connected to the switching converter, wherein the pulse-width-modulating generator varies a frequency or duty cycle of an output control signal that controls the switching characteristics of the switching converter based on the current.

6. The circuit of claim 1, wherein the pulse-width-modulating generator changes the equivalent input resistance at a first point in time prior to a second point in time at which the state of the dimmer circuit changes.

7. The circuit of claim 6, wherein the input voltage or phase analyzer detects a current spike in an input current and varies the first point in time to reduce the size of the spike or eliminate the spike.

8. The circuit of claim 1, wherein the switching converter is a flyback converter or a high-power-factor converter.

9. A method for controlling a switching converter, the circuit comprising:

detecting when a dimmer circuit supplying power to the switching converter changes from a conducting state to a nonconducting state or from a nonconducting state to a conducting state; and

changing an equivalent input resistance of the switching converter to a first, higher value when the dimmer circuit is in the conducting state and to a second, lower value when the dimmer circuit is in the nonconducting state, thereby drawing a minimum current from the dimmer circuit while the dimmer circuit is in the nonconducting state.

10. The method of claim 9, further comprising supplying an output current generated by the switching converter to a light-emitting diode.

11. The method of claim 9, further comprising changing the equivalent input resistance by changing a frequency or duty cycle of an output control signal that controls switching characteristics of the switching converter.

12. The method of claim 9, wherein an average power drawn from the dimming circuit is approximately equal to a power drawn by a switching converter having a constant equivalent resistance.

13. The method of claim 9, further comprising detecting a current flowing through a light-emitting diode connected to the switching converter, wherein a frequency or duty cycle of an output control signal that controls the switching characteristics of the switching converter is varied based on the current.

14. The method of claim 9, further comprising changing the equivalent input resistance at a first point in time prior to a second point in time at which the state of the dimmer circuit changes.

15. The method of claim 14, further comprising detecting a current spike in an input current and varying the first point in time to reduce the size of the spike or eliminate the spike.