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(11) | EP 0 327 404 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Electronic ballast and starter circuit |
| (57) An electronic ballast (2) for a low pressure discharge lamp (1) has a stabilizer
load (3) for series connection with said lamp and an electronic starter circuit (7)
for parallel connection with the said lamp and for series connection with the heater
electrodes (8, 9) of said lamp. The starter circuit (7) has three parallel elements,
the first of said parallel elements comprising a triac (10), the second (11) of said
parallel elements comprising a twin branch voltage divider with a resistive element
(12) in the first of said branches and a capacitive element (13) in the second of
said branches, the third of said parallel elements comprising a series connection
of a diode element (15) and a resistive element (14). The capacitive element (13)
of said second branch is connected across the gate (16) of the said triac (10) by
means of a diode or diac (17). |
[0001] This invention relates to a ballast and electronic starting circuit for a low pressure discharge lamp such as a fluorescent lamp.
[0002] Previous starting circuits have been overly complex and thus are expensive to manufacture and consume excess power in relation to the amount of light delivered by the lamp.
[0003] It is an object of the invention to provide a simplified electronic starter circuit by which a low pressure discharge lamp such as a fluorescent lamp is started quickly and reliably in which the starting of the lamp causes reliable prevention of further starting attempts. It is a further object that the current drawn by the starter should be low and the starting voltage high so that the stabilizing load may be minimized thereby providing a low power loss, less heat, less magnetic field effect and relatively more available power for light output.
[0004] Accordingly it is an object of the present invention to provide a new and improved low pressure discharge tube ballast and electronic starter circuit.
[0005] The present invention provides an electronic ballast for a low pressure discharge lamp such as a fluorescent lamp comprising a stabilizer load for series connection with said lamp and an electronic starter circuit for parallel connection with the said lamp and for series connection with the heater electrodes of said lamp, said starter circuit comprising 3 parallel elements, the first of said parallel elements comprising a triac, the second of said parallel elements comprising a twin branch voltage divider with a resistive element in the first of said branches and a capacitive element in the second of said branches, the third of said parallel elements comprising a series connection of a diode element and a resistive element, wherein said capacitive element of said second branch is connected across the gate of the said triac by means of a diode or diac.
[0006] Preferably the stabilizer load may comprise an inductive element in series with a capacitive element bridged by a resistive element.
[0007] Also the electronic ballast of the invention may include a variable resistive element in the second of said parallel elements which acts as a dimmer.
[0008] The invention also provides an electronic starter circuit for parallel connection with a low pressure discharge lamp such as a fluorescent lamp and for series connection with the heater electrodes of said lamp, said starter circuit comprising three parallel elements, the first of said parallel elements comprising a triac, the second of said parallel elements comprising a twin branch voltage divider with a resistive element in the first of said branches and a capacitive element in the second of said branches, the third of said parallel elements comprising a series connection of a diode element and a resistive element, wherein said capacitive element of said second branch is connected across the gate of the said triac by means of a diode or diac.
[0009] By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawing, which is a schematic diagram of an embodiment of electronic ballast and starter circuit in accordance with the present invention.
[0010] Referring to the drawing, the Figure shows a low pressure discharge lamp such as a fluorescent lamp 1 in place with the ballast and starter circuit of the invention generally designated 2.
[0011] Stabilizing load 3 is connected in series between the mains voltage 18 (which may include a switch, not shown) and the lamp 1. Stabilizing load 3 consists of an inductive portion 4 and a capacitive portion 5 which latter portion is bridged by resistive element 6.
[0012] Electronic starter circuit 7 is connected in parallel with the lamp 1 and in series with the heater electrodes designated 8 and 9 respectively. Starter circuit 7 consists of 3 parallel elements:
1) firstly, triac 10, and
2) secondly, voltage divider 11 comprising resistive element 12 and capacitor 13, and
3) thirdly, resistor 14 and diode 15.
[0014] One example of a circuit as shown in Figure 1 for operation on 120 volts a.c. at 60 hertz with a 4 foot 60 watt fluorescent lamp has the following components:
| inductors | 1 | 0.27 henry |
| capacitors | 5 | 6 micro f |
| 13 | 333 micro f | |
| resistors | 6 | 750 k ohms |
| 12 | 750 k ohms | |
| 14 | 47 k ohms | |
| triac | 10 | |
| diac | 17 | |
| diode | 15 | In4004 |
[0015] In an alternative arrangement, the above-mentioneed components have the following values:
| inductors | 1 | 0.27 henry |
| capacitors | 5 | 5 micro f |
| 13 | 0.033 micro f | |
| resistors | 6 | 750 k ohms |
| 12 | 680 k ohms | |
| 14 | 47 k ohms | |
| triac | 10 | 1 amp 600V piv |
| diac | 17 | st-2 |
| diode | 15 | In4004 |
1. An electronic ballast (2) for a low pressure discharge lamp (1) comprising a stabilizer
load (3) for series connection with said lamp and an electronic starter circuit (7)
for parallel connection with the said lamp and for series connection with the heater
electrodes (8, 9) of said lamp, said starter circuit (7) comprising three parallel
elements, the first of said parallel elements comprising a triac (10),the second (11)
of said parallel elements comprising a twin branch voltage divider with a resistive
element (12) in the first of said branches and a capacitive element (13) in the second
of said branches, the third of said parallel elements comprising a series connection
of a diode element (15) and a resistive element (14), wherein said capacitive element
(13) of said second branch is connected across the gate (16) of the said triac (10)
by means of a diode or diac (17).
2. An electronic ballast as claimed in claim 1, wherein the stabilizer load (3) comprises
an inductive element (4) in series with a capacitive element (5) bridged by a resistive
element (6).
3. An electronic ballast as claimed in claim 1 or claim 2, wherein the resistive element
(12) in the second of said parallel elements (11) is a variable resistive element.
4. An electronic starter circuit (7) for parallel connection with a low pressure discharge
lamp (1) and for series connection with the heater electrodes (8, 9) of said lamp,
said starter circuit (7) comprising three parallel elements, the first of said parallel
elements comprising a triac (10), the second (11) of said parallel elements comprising
a twin branch voltage divider with a resistive element (12) in the first of said branches
and a capacitive element (13) in the second of said branches, the third of said parallel
elements comprising a series connection of a diode element (15) and a resistive element
(14), wherein said capacitive element (13) of said second branch is connected across
the gate (16) of the said triac (10) by means of a diode or diac (17).
5. An electronic starter circuit as claimed in claim 4, wherein the resistive element
(12) in the second of said three parallel elements (11) is a variable resistive element.