VARIABLE LOAD CIRCUITS FOR USE WITH LIGHTING CONTROL DEVICES

• US 20120139431A1
• Filed: 02/09/2012
• Published: 06/07/2012
• Est. Priority Date: 09/04/2006
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Thompson, Stephen, Booth, Graham, Lopez, Clive
• Granted Patent: US 8,829,805 B2
• Time in Patent Office: Days
• US Class Current: 315/200.R
• CPC Class Codes: H05B 41/3921 with possibility of light intensity variations
• CPC Class Codes: H05B 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers
• CPC Class Codes: H05B 45/397 Current mirror circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A variable load circuit (2) is provided for use with a dimmer (1). A low wattage load such as a LED (3) is provided in series with the dimmer and the variable load circuit is provided in parallel with the LED. The variable load circuit has two different load characteristics: when the applied voltage from the dimmer is below a threshold, the variable load circuit presents a fixed load (24), and when the applied voltage is above a threshold the variable load circuit presents a variable load so as to act as a constant current sink. The variable load is provided by a secondary load portion (25) which may or may not act in combination with the fixed load (24), and the secondary load portion (25) is switched in or out of the variable load circuit by a trigger circuit portion (26).

Claims

1. A variable load circuit for use with a lighting control device, and arranged to operate with two different load characteristics during a half cycle of an applied alternating signal, the variable load circuit comprising:

means responsive to the applied alternating signal for;

allowing current flow in response to voltage applied during one portion of the half cycle of the applied alternating signal, and

allowing the variable load circuit to act as a constant current sink during another portion of the half cycle, and

allowing the variable load circuit to operate independently of any external load that is connected to the variable load circuit.

2. The variable load circuit according to claim 1, wherein during the one portion of the applied alternating signal the variable load circuit acts as a substantially fixed resistive load.

3. The variable load circuit according to claim 1, wherein the variable load circuit is arranged to present different load characteristics during first and third portions of the half cycle of the applied alternating signal than during a second portion of the half cycle of the applied alternating signal.

4. The variable load circuit according to claim 1, further comprising a fixed load circuit portion, which includes at least one resistor arranged to act as a fixed load.

5. The variable load circuit according to claim 1, further comprising a secondary load circuit portion that is arranged to operate during part of the half cycle of the applied alternating signal.

6. The variable load circuit according to claim 5, wherein the secondary load circuit portion comprises a first switch arranged to switch the secondary load circuit in and out of the variable load circuit.

7. The variable load circuit according to claim 5, further comprising a fixed load circuit portion that includes at least one resistor arranged to act as a fixed load, wherein the fixed load circuit portion and secondary load circuit portion together act as a constant current sink during a portion of the half cycle.

8. The variable load circuit according to claim 5, wherein the secondary load circuit portion acts as a constant current sink during a portion of the half cycle.

9. The variable load circuit according to claim 1, further comprising a fixed load circuit portion that comprises a transistor.

11. The variable load circuit according to claim 1, further comprising no more than two terminals for external connections.

12. The variable load circuit according to claim 1 wherein the means responsive to the applied alternating signal are arranged to allow a greater current flow in response to voltage applied during the one portion of the half cycle than in response to voltage applied during the another portion of the half cycle.

13. The variable load circuit according to claim 1, wherein during the one portion of the half cycle, the absolute value of the voltage of the applied alternating signal is below a threshold, and during the another portion of the half cycle, the absolute value of the voltage is above a threshold.

10. The variable load circuit according to claim h further comprising a rectifier for rectifying an AC input to the variable load circuit.

14. A lighting control apparatus comprising:

a variable load circuit; and

a lighting control device connected to the variable load circuit, wherein the lighting control device is arranged to supply an alternating signal to the variable load circuit, and the variable load circuit is arranged to operate with two different load characteristics during a half cycle of the applied alternating signal,

wherein the variable load circuit comprises means responsive to the applied alternating signal for;

permitting current to flow in response to voltage applied during one portion of the half cycle of the applied alternating signal,

allowing the variable load circuit to act as a constant current sink during another portion of the half cycle, and

enabling the variable load circuit to operate independently of any external load that is connected to the variable load circuit.

15. The lighting control apparatus according to claim 14, wherein the lighting control device requires a minimum current to pass for correct operation and the variable load circuit is arranged to pass at least the minimum current during the second portion of the half cycle of the applied alternating signal.

16. The lighting control apparatus according to claim 14, wherein the lighting control device is arranged to charge during a first portion of the half cycle of the applied alternating signal and the variable load circuit is arranged to pass sufficient current during the first portion of the half cycle of the applied alternating signal to allow the lighting control device to charge.

17. The lighting control apparatus according to claim 14, wherein the lighting control device is arranged in series with the variable load circuit.

18. The lighting control apparatus according to claim 14, wherein the lighting control apparatus is connectable to a light for control of the light.

19. The lighting control apparatus according to claim 18, wherein the variable load circuit is arranged in parallel with the light, when the light is connected to the lighting control apparatus.

20. A variable load circuit for use with a lighting control device, the variable load circuit being arranged to:

operate with two different load characteristics during a half cycle of an applied alternating signal,

allow greater current flow in response to voltage applied during a first portion of the half cycle of the applied alternating signal than in response to voltage applied during a second portion of the applied alternating signal,

act as a constant current sink during the second portion of the applied alternating signal, and

operate independently of any external load, connected to the variable load circuit.