STABILIZATION CIRCUIT FOR LOW-VOLTAGE LIGHTING

• US 20140333205A1
• Filed: 05/13/2014
• Published: 11/13/2014
• Est. Priority Date: 05/13/2013
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Kost, Michael A., King, Eric J., Melanson, John L., Zanbaghi, Ramin, Wang, Kan
• Granted Patent: US 9,385,621 B2
• Time in Patent Office: Days
• US Class Current: 315/127
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output

Abstract

An electronic transformer stabilization circuit includes a detection circuit and a reactive load. The detection circuit may be configured to receive a transformer output or a transformer signal derived from the transformer output. The detection circuit may determine whether the transformer that generated the transformer output is an electronic transformer. The determination may be made based on the presence of absence of high frequency components in the transformer output. Responsive to determining that an electronic transformer generated the transformer output, the stabilization circuit may operate a switch to connect the reactive load across an output of the transformer. The reactive load may include an inductor and may be configured to draw a stabilization current from the transformer. The stabilization current may ensure that the total current drawn from the transformer exceeds an oscillation current required to maintain reliable operation of the electronic transformer.

Claims

1. A stabilization apparatus, comprising:

a reactive load configured to draw a stabilization current from a transformer output;

a detection circuit configured to;

monitor a transformer signal indicative of the transformer output for a predetermined condition; and

couple the reactive load to the transformer output responsive to detecting the predetermined condition.

2. The stabilization apparatus of claim 1, further comprising:

a bridge rectifier configured to generate a rectified signal from the transformer output;

wherein the transformer signal is selected from a group consisting of;

the transformer output; and

the rectified signal.

3. The stabilization apparatus of claim 2, further comprising:

a driver configured to receive the rectified signal and produce a direct current load signal; and

a load circuit configured to receive the load signal from the driver.

4. The stabilization apparatus of claim 2, wherein the load circuit comprises a light producing load circuit.

5. The stabilization apparatus of claim 4, wherein the light producing load circuit includes a light emitting diode configured to receive the load signal.

6. The stabilization apparatus of claim 1, wherein the predetermined condition is indicative of whether an electronic transformer provided the transformer output.

7. The stabilization apparatus of claim 1, wherein the predetermined condition is indicative of whether the transformer output includes a component selected from the group consisting of:

a component having a frequency exceeding a specified threshold frequency; and

a component having a frequency within a specified frequency band.

8. The stabilization apparatus of claim 1, wherein the reactive load includes:

an inductor; and

a semiconductor switch configured to provide a current path for inductor current.

9. The stabilization apparatus of claim 8, wherein the switch comprises an opto-coupled triac.

10. A circuit stabilization method, comprising:

monitoring a transformer for a characteristic indicative of an electronic transformer;

responsive to detecting the characteristic, coupling a reactive load to the transformer; and

responsive to not detecting the characteristic, decoupling the reactive load from the transformer.

11. The circuit stabilization method of claim 10, wherein monitoring the transformer comprises monitoring a transformer signal indicative of a transformer output generated by the transformer.

16. The circuit stabilization method of claim 10, wherein the reactive load comprises an inductor configured to draw a minimum peak current from the transformer.

17. The circuit stabilization method of claim 16, wherein:

the inductor comprises an inductor of a low voltage lamp including a light emitting load including a light emitting diode;

the monitoring comprising monitoring, by the low voltage lamp; and

the coupling of the reactive load comprises coupling the inductor in parallel with an output of the transformer.

12. The circuit stabilization method of 11, wherein the characteristic comprises a component of the transformer signal having a frequency exceeding a predetermined minimum.

13. The circuit stabilization method of claim 12, further comprising:

rectifying the transformer output with a bridge rectifier to produce a rectified signal.

14. The circuit stabilization method of 13, wherein the transformer signal comprises the rectified signal.

15. The circuit stabilization method of 13, wherein the transformer signal comprises the transformer output.

18. An apparatus, comprising:

an inductor;

a switch configured to respond to a detection signal by connecting the inductor to an output of a transformer;

a bridge rectifier configured to generate a rectified signal in accordance with a transformer output of the transformer; and

a detection circuit configured to generate the detection signal responsive to detecting, in a transformer signal, a frequency component having a frequency exceeding a threshold frequency.

19. The apparatus of claim 18, wherein the transformer signal comprises the transformer output.

20. The apparatus of claim 18, wherein the transformer signal comprises the rectified signal.

21. The apparatus of claim 18, further comprising:

a light emitting load; and

a driver configured to receive the rectified signal and drive the light emitting load.

22. The apparatus of claim 21, wherein the light emitting load comprises light emitting diode.