WO2014000182A1

WO2014000182A1 - Bi-level dimmer system for discharge lamps with electronics ballasts

Info

Publication number: WO2014000182A1
Application number: PCT/CN2012/077633
Authority: WO
Inventors: Chenghua Zhu; Hongbin WEI
Original assignee: General Electric Company
Priority date: 2012-06-27
Filing date: 2012-06-27
Publication date: 2014-01-03

Abstract

A discharge lamp system with a bi-level or multi-level dimming circuit includes a first discharge lamp bank, a second discharge lamp bank and a dimmer control circuit electrically coupled to the first discharge lamp bank. The dimmer control circuit includes a switching device, a capacitive device electrically connected in series with the switching device, the switching device and capacitive device connected in series between a source of electrical power and the first discharge lamp bank, and a current limiting device electrically coupled in parallel with the switching device and capacitive device and configured to limit a flow of current through the first discharge lamp bank when the switching device is in an open state.

Description

BI-LEVEL DIMMER SYSTEM FOR DISCHARGE LAMPS WITH ELECTRONICS

BALLASTS

BACKGROUND

[0001] The present disclosure generally relates to dimming circuits, and more particularly to a dimming circuit for a gas discharge lamp.

[0002] A gas-discharge lamp belongs to a family of lighting devices that generate light by passing electric current through a gas or vapor within the lamp. Atoms in the vapor absorb energy from the electric current and then release the absorbed energy as light. One of the best known types of gas discharge lamps is the fluorescent lamp. Fluorescent lamps generally contain mercury vapor whose atoms emit light in the non-visible low wavelength ultraviolet region. The ultraviolet radiation then causes a phosphor disposed on the interior of the lamp tube to luminesce or fluoresce, producing visible light.

[0002] In practice, fluorescent lamps are nearly always driven with alternating current

(AC), which allows the lamp current to be controlled using an inductor or other type of reactive module that limits the flow of alternating current without dissipating energy. These current controlling modules are generally referred to as ballast modules or "ballasts". In practice, the term ballast is commonly used to refer to the entire fluorescent lamp drive module, not just the current limiting portion.

[0003] An electronic dimming ballast is often used to control the lighting for a gas discharge lamp. Typically, conventional dimming circuits for gas discharge lamps include a control integrated circuit (IC) or a complex circuit of multiple inverters to control different power outputs. However, this type of circuitry for conventional electronic gas discharge lamp dimming tends to be expensive and complex. It is also difficult to miniaturize these types of circuits.

[0004] Accordingly, it would be desirable to a dimming circuit topology for a gas discharge that addresses at least some of the problems identified above.

BRIEF SUMMARY OF THE INVENTION

[0005] As described herein, the exemplary embodiments overcome one or more of the above or other disadvantages known in the art.

[0006] One aspect of the exemplary embodiment relates to a discharge lamp system with a multi-level dimming circuit. In one embodiment, the system includes a first discharge lamp bank, a second discharge lamp bank and a dimmer control circuit electrically coupled to the first discharge lamp bank. The dimmer control circuit includes a switching device, a capacitive device electrically connected in series with the switching device, the switching device and capacitive device connected in series between a source of electrical power and the first discharge lamp bank, and a current limiting device electrically coupled in parallel with the switching device and capacitive device and configured to limit a flow of current through the first discharge lamp bank when the switching device is in an open state.

[0007] Another aspect of the disclosed embodiments is directed to a discharge lamp dimming control circuit for a lamp group. In one embodiment, the control circuit includes switch, a first leg of the switch configured to be electrically connected to a source of AC power for the lamp group; a capacitance electrically connected in series to a second leg of the switch; and a current limiting device electrically coupled in parallel with the switch and the capacitance, a first leg of the current limiting device being configured to be coupled to the source of AC power and a second leg of the current limiting device being configured to be electrically coupled to the lamp group.

[0008] A further aspect of the disclosed embodiments is directed to a method of providing controlled dimming to a discharge lamp. In one embodiment, the method includes applying a source of AC power to a first group of discharge lamps and a second group of discharge lamps, inserting a control circuit between the source of AC power and the first group of discharge lamps, and opening a switch in the control circuit to limit a flow of current to the first group of discharge lamps to extinguish the first group of discharge lamps.

[0009] These and other aspects and advantages of the exemplary embodiments will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. Additional aspects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the aspects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings:

[0011] Fig. 1 illustrates an exemplary embodiment of a dimming circuit topology incorporating aspects of the present disclosure. [0012] Fig. 2 illustrates another embodiment of a dimming circuit topology incorporating aspects of the present disclosure.

[0013] Fig. 3 illustrates a further embodiment of a dimming circuit topology incorporating aspects of the present disclosure.

DETAILED DESCRIPTION

[0014] The aspects of the disclosed embodiments provide a multi-level dimming circuit for a discharge lamp, such as gas discharge lamp. For purposes of the description herein, the multi-level dimming circuit will be referred to as a bi-level dimming circuit, the term "bi-level" meaning that there are two groups of lamps. The aspects of the disclosed embodiments can be applied to a single lamp or a bank of lamps. The gas discharge lamps can include fluorescent lamps, such as compact fluorescent lamps. The dimming circuit achieves a bi-level or multilevel dimming function by limiting the electrical current flow to one or more groups of lamps to reduce light output or shut down those groups. The bi-level dimming circuit of the disclosed embodiments provides an economical gas discharge lamp dimming solution that is simple to implement and can be applied in current fed and voltage-fed gas discharge lamp topologies.

[0015] Fig. 1 illustrates one embodiment of a gas discharge lamp dimming circuit 100 incorporating aspects of the present disclosure. The lamp dimming circuit 100 includes a first group or bank 10 of lamps 11, 12 to In, and a second group or bank 20 of lamps 21, 22 to 2n, the term "n" representing any desired number of lamps 1 1 and 12. The lamps 11 , 12 and In in group 10 are electrically connected in parallel. The lamps 21, 22, 2n in group 20 are also electrically connected in parallel. In this embodiment, a dimming control circuit 2 is coupled into the first group 10 of lamps and is configured to control the flow of electrical power to the group 10 of lamps. The dimming control circuit 2 may be coupled to the positive or negative AC power terminal, AC+, AC-, of a high frequency AC voltage bus or other such power supply. In the example of Fig. 1, the dimming control circuit 2 is coupled to the negative AC power terminal AC-. The dimming control circuit 2 is configured to provide bi-level dimming control of the gas discharge lamps.

[0016] The term bi-level, as is used herein, means that there are two groups 10, 20 of lamps 11, 12. In one embodiment, both groups 10, 20 of lamps 11, 12 can be independently controlled to operate at full light output or at a predetermined reduced light output. In another embodiment, one of the groups 10, 20 of lamps 11, 12 can operate at full light output, while the other group operates at a reduced light output or shuts down, according to user's requirement. In a multi-level configuration, there are two or more groups of lamps, where each group of lamps can be independently controlled to operate either at full light output or predetermined reduced light output (include zero output). In a multi-level configuration, there are multiple levels of light output can be controlled according to the user's requirements.

[0017] In the embodiment shown in Fig. 1, the control circuit 2 includes a switch Ml and a capacitor CI . The control circuit 2 is generally configured to control the flow of AC power provided to the group 10 of lamps 11, 12 to In. Suitable AC power is delivered over an AC power bus, generally indicated by power lines or inputs AC+ and AC-. In the embodiment shown in Fig. 1, AC+ and AC- are high frequency voltage bus input terminals (or, alternating current power lines).

[0018] In one embodiment, the switch Ml is a Field Effect Transistor (FET) or MOSFET type device. In alternate embodiments, the switch Ml can comprise any suitable electronic switching device, such as for example, a bipolar junction transistor. As shown in the embodiment of Fig. 1, the switch Ml and the capacitor CI are connected in series. The capacitor CI can be used to current limit the switch Ml . One leg 3 of the switch Ml is coupled to the AC power and the other leg 5 of the switch Ml is coupled to the capacitor CI . The capacitor CI is connected in series between the leg 5 of the switch Ml and the group 10 of lamps 11, 12, In.

[0019] In the embodiment shown in Fig. 1, a current limiting component 4 is coupled in parallel with the switch Ml and capacitor CI, between one leg of the AC power and the group 10 of lamps 11, 12, In. In this example, the current limiting component 4 is coupled to the AC- power terminal. The current limiting component 4 is used to limit the flow of current through the lamps 11, 12 and In and can comprise any suitable current limiting device. Examples of these components or devices can include, but are not limited to, discrete or passive electronic components, such as a resistor, a Positive Temperature Coefficient (PTC) thermistor, a capacitor, or such other suitable device that can limit the current flow through the lamps 11, 12 to In. When the current limiting device 4 is a resistor, the resistance of the resistor is much larger than the equivalent resistance of the lamps 11, 12, In.

[0020] In the embodiment shown in Fig. 1, the control circuit 2 is preferably implemented as an impedance element CI in series with a switch Ml . When state of the switch Ml is OFF, also known as an open state, the current limiting device 4, which is connected in series with the group 10 of lamps 11, 12 to In, limits the flow of current through the group 10 of lamps 11, 12, In. The current limiting will cause the lamps 11, 12, In to operate at a predetermined reduced light output level or shut down. In one embodiment, when the reactance of the current limiting device 4 is large enough, the current limiting device 4 limits the current through the lamps 11, 12 to be close to zero, in which case the lamps 11, 12 go out or are extinguished. [0021] When the state of the switch Ml is ON, or in a conducting state, the current limiting component 4 is electrically shorted by the capacitor CI that is connected in series with the switch Ml . Cl l and C21 are lamp capacitors to limit the current through the lamps as generally required. The value of the capacitance CI is much larger than the values of the lamp capacitors Cl l, C12, Cln. In one embodiment, exemplary values for the capacitor CI is approximately 0.1 microfarad (μΡ) for CI, while exemplary values for lamp capacitors CI 1,C12...Cln usually are several nanofarad (nF). Capacitor C3 is a capacitor which is used to limit current through the lamp bank 20. When the current limiting device 4 is electrically shorted, the voltage from the power lines AC+ and AC- is applied to the lamps 11, 12, In, causing the lamps to ignite. The lamps 11, 12... In operate at full light output, in a manner that is generally understood.

[0022] The control line 7 provides an electrical signal to control the switch Ml on and off. In one embodiment, the control line 7 is coupled to the user interface. For example, the control signal on the control line 7 can be generated from an electrical switch, a voice controlled switching device or an optically controlled switching device and processed by a signal processing circuit. The output of the signal processing circuit is a high level or low level voltage signal on the control line 7 and is used to control the switching or activation of the switch Ml ON or OFF. When the control signal on control line 7 is a high level voltage signal, Ml is on and the lamps 11, 12... In operate at full light output. When the control signal on control line 7 is a low level voltage signal, Ml is off and the lamps 11, 12... In operate at a reduced light output or are extinguished .

[0023] In the embodiment of Fig. 1, the control circuit 2 is shown coupled to a single group 10 of lamps. In alternate embodiments, the control circuit 2 can be applied to multiple groups of lamps to provide multi-level control, with each group of lamps having a control circuit 2. When the control circuit 2 is applied to only one group of lamps, the group of lamps are controlled to operate at full light output or a predetermined reduced light output (such as zero output). When applied to multiple banks, the control circuits 2 can be configured to control one or more banks to operate at a reduced light output (such as zero output or shut down), while others remain on.

[0024] Fig. 2 illustrates another embodiment of a gas discharge lamp circuit 200 incorporating aspects of the present disclosure. In this embodiment, the control circuit 2 is shown coupled to the positive AC power terminal, AC+. The leg 3 of the switch Ml in this example is electrically coupled in series to the group 10 of lamps 11, 12, In. The leg 5 of the switch Ml is electrically coupled in series to the capacitor CI. The capacitor CI is electrically coupled in series between the positive AC power terminal AC+ and the switch Ml . The current limiting component 4 is electrically coupled in series between the positive AC power terminal AC+ and the group 10 of lamps 11, 12, In, and in parallel with the capacitor CI and switch Ml . In the embodiment shown in Fig. 1, the control circuit 2 is electrically coupled to the capacitors Cl l, C12 and Cln, which are electrically coupled in series between the control circuit 2 and the respective lamps 11, 12, In of group or bank 10. A capacitor C4 is electrically coupled in series between each lamp 11, 12, In and the negative AC power terminal AC- to limit current through the corresponding lamp bank, similar to capacitor C3 described with respect to Fig. 1. An exemplary value for C4 is approximately 0.1 μΡ. In alternate embodiments, any suitable value may be used.

[0025] Fig. 3 illustrates another embodiment of a gas discharge lamp dimming control circuit 300 incorporating aspects of the disclosed embodiments. The operational principle of the circuit 300 shown in Fig. 3 is similar to the operational principle illustrated with respect the circuits shown in Figs. 1 and 2. In the example of Fig. 3, the lamps 11 and In of lamp group or bank 30 are electrically connected in series. The lamps 21 and 2n of lamp group or bank 40 are also electrically connected in series. Although only two lamps are shown in each group 30, 40, the groups 30, 40 can include any suitable number of lamps.

[0026] In the embodiment shown in Fig. 3, an inductor coil LI is electrically coupled in series between the positive alternating current power terminal AC+ and the discharge lamp group 30. An inductor coil L2 is electrically coupled in series between the positive alternating current power terminal AC+ and the lamp group 40. The inductors LI and L2 are the resonant inductors in the corresponding resonant tanks and are generally configured to oppose rapid changes in the current flow to the lamp group 30, 40. The dimmer control circuit 2 in this example of Fig. 3 is electrically connected in series between the lamp group 30 and the negative AC power terminal AC-. In alternate embodiments, the dimmer control circuit 2 could be coupled to the positive AC power terminal AC+. C31 and C32 are resonant capacitors in the respective resonant tanks. The function of C33 function is similar to C3 described with respect to Fig. 1.

[0027] The aspects of the disclosed embodiments are directed to dimming ballasted lamps. A dimming control circuit includes a switch and a capacitor connected in series with the switch. The switch and capacitor are connected in series between a source of electrical power and a group of discharge lamps, and a current limiting device electrically coupled in parallel with the switch and capacitor and configured to limit a flow of current through the group of lamps to a predetermined light output level. When the lamp current is limited to be low enough, the group of lamps will shut down. When the switch is controlled to be in an ON state, the group of lamps may operate at full light output in a manner of generally understood. When the switch is controlled to be in an OFF state, the group of lamps operates at a predetermined reduced light output due to the additional reactance inserted and the lamp will shut down when the lamp current is low enough. By appropriate selection of the current limiting device, the desired light output level can be achieved.

[0028] Thus, while there have been shown, described and pointed out, fundamental novel features of the invention as applied to the exemplary embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the invention. Moreover, it is expressly intended that all combinations of those elements, which perform substantially the same function in substantially the same way to achieve the same results, are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

CLAIMS What is claimed is:

1. A discharge lamp system for bi-level dimming circuit, comprising:

a first discharge lamp bank;

a second discharge lamp bank; and

a dimmer control circuit electrically coupled to the first discharge lamp bank, the dimmer control circuit comprising:

a switching device;

a capacitive device electrically connected in series with the switching device, the switching device and capacitive device connected in series between a source of electrical power and the first discharge lamp bank; and

a current limiting device electrically coupled in parallel with the switching device and capacitive device and configured to limit a flow of current through the first discharge lamp bank when the switching device is in an open state.

2. The discharge lamp system of claim 1, wherein the first discharge lamp bank and the second discharge lamp bank each comprise a plurality of discharge lamps electrically connected in parallel.

3. The discharge lamp system of claim 1, wherein the first discharge lamp bank and the second discharge lamp bank each comprise a plurality of discharge lamps electrically connected in series.

4. The discharge lamp system of claim 1, wherein the switching device comprises a transistor.

5. The discharge lamp system of claim 1, wherein the current limiting device comprise a resistor, a capacitor, or a Positive Temperature Coefficient (PTC) thermistor.

6. The discharge lamp system of claim 1, comprising an AC power bus to provide AC power to each of the first discharge lamp bank and the second discharge lamp bank, wherein the dimmer control circuit is electrically connected between the AC power bus and the first discharge lamp bank.

7. The discharge lamp system of claim 6, wherein one side of the dimming control circuit is electrically connected to a positive AC power terminal of the AC power bus and an other side of the dimming control circuit is electrically coupled to the first lamp bank.

8. The discharge lamp system of claim 6, wherein one side of the dimming control circuit is electrically connected to a negative AC power terminal of the AC power bus and an other side of the dimming control circuit is electrically coupled to the first lamp bank.

9. The discharge lamp system of claim 1, wherein the second discharge lamp bank is electrically coupled between a positive and positive terminal of the AC power bus.

10. A discharge lamp dimming control circuit for a lamp group, comprising:

a switch, a first leg of the switch configured to be electrically connected to a source of

AC power for the lamp group;

a capacitance electrically connected in series to a second leg of the switch; and a current limiting device electrically coupled in parallel with the switch and the capacitance, a first leg of the current limiting device being configured to be coupled to the source of AC power and a second leg of the current limiting device being configured to be electrically coupled to the lamp group.

11. The control circuit of claim 10, wherein the switch comprises a transistor.

12. The control circuit of claim 10, wherein the current limiting device comprise a resistor, a capacitor, or a Positive Temperature Coefficient (PTC) thermistor.

13. The control circuit of claim 10, wherein the current limiting device is configured to limit a flow of current from the AC power source when a state of the switch is open.

14. The control circuit of claim 10, wherein the current limiting device is electrically shorted when a state of the switch is closed.

15. A method of providing controlled dimming to a discharge lamp, comprising: applying a source of AC power to a first group of discharge lamps and a second group of discharge lamps; inserting a control circuit between the source of AC power and the first group of discharge lamps; and

opening a switch in the control circuit to limit a flow of current to the first group of discharge lamps to extinguish the first group of discharge lamps.

16. The method of claim 15, comprising providing a current limiting device in parallel with the switch to extinguish the first group of discharge lamps.

17. The method of claim 15, comprising closing the switch to ignite the first group of lamps.

18. The method of claim 17, wherein closing the switch electrically short circuits a current limiting device electrically coupled in parallel with the switch.