Ballast/Line Detection Circuit for Fluorescent Replacement Lamps

• US 20100181925A1
• Filed: 01/19/2010
• Published: 07/22/2010
• Est. Priority Date: 01/21/2009
• Status: Active Grant

• Current Assignee: Ilumisys Incorporated (Altair Engineering Incorporated)
• Original Assignee: Altair Engineering Incorporated
• Inventors: Palazzolo, Francis, Ivey, John
• Granted Patent: US 8,664,880 B2
• Time in Patent Office: Days
• US Class Current: 315/224
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/37 Converter circuits

Abstract

Disclosed herein is a replacement light for a fluorescent tube usable in a fluorescent fixture connected to a power source and containing at least one LED, the improvement including a detection circuit for connection to the power source, the detection circuit configured to identify the power source.

Claims

1. In a replacement light for a fluorescent tube usable in a fluorescent fixture connected to a power source and containing at least one LED, the improvement comprising:

a detection circuit for connection to the power source, the detection circuit configured to identify the power source.

2. The improvement of claim 1, wherein the power source includes one of an AC line with a ballast and an AC line without the ballast.

3. The improvement of claim 1, wherein the detection circuit is configured to detect a high-voltage condition based on a voltage from the power source.

4. The improvement of claim 1, wherein the detection circuit is further configured to limit a maximum voltage applied to the replacement light.

5. The improvement of claim 1, wherein the detection circuit further comprises:

a Zener diode having a Zener voltage setting sufficiently high to not conduct when a voltage input from an AC line is connected to the detection circuit, and sufficiently low to conduct when a voltage input from the ballast is connected to the detection circuit.

6. The improvement of claim 5, wherein the detection circuit is configured to detect Zener conduction by detecting a current flowing through the Zener diode.

7. The improvement of claim 1, wherein the detection circuit comprises:

a full-wave rectifier electrically coupled to the power source and configured to produce a rectified voltage output;

a smoothing filter electrically coupled to the full wave rectifier and configured to produce a smoothed rectified voltage output;

a Zener diode and a resistor electrically coupled in parallel to the smoothing filter; and

a comparator, wherein one input of the comparator is electrically coupled to a point between the Zener diode the resistor and another input of the comparator is electrically coupled to a reference voltage.

8. The improvement of claim 7, wherein the detection circuit further comprises:

a D flip-flop configured to receive an output of the comparator and to output a signal identifying the power source.

9. The improvement of claim 8, wherein the detection circuit further comprises:

a control circuit configured to receive the output signal and configured to generate a pulse width modulated (PWM) ON/OFF control signal based on the output signal.

10. The improvement of claim 9, wherein the detection circuit further comprises:

a power converter including at least one switching element, wherein the control circuit is electrically coupled to a gate of the switching element, the switching element configured to deliver current to the at least one LED in response to the PWM ON/OFF control signal.

11. In a fluorescent replacement lamp, the improvement of a detection circuit comprising:

a pair of input terminals adapted to receive a voltage source input;

a rectifier connected to the pair of input terminals;

a Zener diode and resistor connected to the filter, such that if the voltage source is an AC line, the Zener diode does not conduct, and if the voltage source is a ballast, a rectified voltage will rise until the Zener diode conducts; and

means for generating a ballast detected signal based on the conduction of the Zener diode.

12. The fluorescent replacement lamp of claim 11, further comprising:

a control circuit configured to operate as a normal line-powered switcher when the Zener diode does not conduct, and the control circuit configured to operate in a ballast mode when a current conducted through the Zener diode is sufficiently high, and voltage across the resistor is above a reference voltage.

13. The improvement of claim 11, wherein the means for generating a ballast detect signal include:

a D flip-flop connected between the Zener diode and the control circuit to be set when current conducted through the Zener diode is sufficiently high, and voltage across the resistor is above a reference voltage, causing the control circuit to operate in a ballast mode in which increasing current drawn from the voltage source decreases power drawn from the voltage source, and vice versa.

14. In a process for supplying a power source for a fluorescent replacement lamp, the improvement comprising:

connecting a detection circuit between the power source and the fluorescent replacement lamp, the detection circuit for identifying a type of power source between an AC line and a ballast, and for limiting a maximum voltage applied to the fluorescent replacement lamp.

15. The improvement of claim 14 further comprising:

detecting a high-voltage condition on a rectified input voltage from the power source with the detection circuit.

16. The improvement of claim 14 further comprising:

preventing excessive voltages input from the power source from damaging other components.

17. The improvement of claim 14 further comprising:

preventing conduction through a Zener diode having a Zener voltage setting sufficiently high, when voltage from the AC line is connected to the input;

allowing conduction through the Zener diode having the Zener voltage setting sufficiently low, when voltage from the ballast is connected to the input, wherein the Zener voltage setting is sufficiently low so that any voltage-sensitive components are not damaged; and

detecting a current flowing through the Zener diode to identify the type of power source.

18. The improvement of claim 14 further comprising:

latching a signal from the power source; and

detecting a difference in incremental change to determine the type of power source, since a normal operating point of the fluorescent replacement lamp is very similar for both AC line and ballast operation.

19. The improvement of claim 14 further comprising:

engaging a control system based on the power source identification, wherein the control system is selected from a group consisting of a control algorithm and control circuit;

if a ballast is wrongly identified as an AC line, triggering the control system to be switched to a ballast mode of operation based on rising voltage and Zener diode conduction.

20. The improvement of claim 14 further comprising:

if a Zener diode energy and power capacity is sufficiently high, delaying a start of a control system without damaging other components thereby providing a protective action.