DE4232438A1 - Ballast circuit for fluorescent lamp - uses two transformers with filament heating windings in phase opposition and time switch for ignition winding - Google Patents

Abstract

The ballast uses a transformer (2) connected to the power supply (1) with three secondary windings in series, there being a condenser (C1) between the middle winding (2.2) and one end winding (4.2). The middle winding gives the ignition voltage, the end windings give the filament heating voltage. These two end windings are connected to the secondary windings of a second transformer (4) so as to have a different phase relationship from that in the first transformer. A time switch (3) connects the primary winding of the second transformer (3.4) to the middle secondary of the first transformer. The impedance of the primary winding of the second transformer is much smaller than that of the middle winding of the first transformer. ADVANTAGE - Higher reliability and lamp efficiency with longer lamp life.

Description

The invention relates to a ballast for fluorescent lamps, which is also especially for the Suitable for use in vehicles.

Electronic ballasts are known for Fluorescent lamps, which are switched by externally controlled Flyback converters or free-swinging Transducers and their stray field transformers one for Adequate ignition voltage is available for fluorescent lamps set, the ballast the lamp voltage limited to a certain value (DE 37 42 921).

The known versions of ballasts are disadvantageous for fluorescent lamps that the operational reliability the same especially with frequent Switching cycles is increasingly less. Also the total burning time of fluorescent lamps in this system because of the constantly above the required level Filament preheating voltage very limited and that too System efficiency is for the same reasons relatively low.  

Furthermore, the known ballasts for different types of fluorescent lamps of fluorescent lamps with regard to their preheating voltage conditions adjust only relatively complex.

The problem is a ballast for To create fluorescent lamps, which in the system ballast Fluorescent lamps the total burning time extended, operational reliability improved and increases efficiency.

According to the invention the problem is solved in that a rectangular pulse power supply, preferably in the form of a transducer, such as a tactile Power supply, a transistor inverter or one other electronic ballast, the winding (primary) is connected downstream of a transformer. This winding is three or more in series switched windings (secondary) assigned, of which one of them is provided with a capacitor. This first transmitter is another, second Subordinate transformer, whose winding (primary) over a timer with that belonging to the capacitor Winding interconnected in the first transformer is, these two windings being different Have impedance.  

The winding (primary) of the second transformer are assigned two windings. Each of them is with one of the remaining windings (secondary) of the first Transformer and a filament of a fluorescent lamp connected in series, with the windings (secondary) the first transformer has a different phase position than have the windings of the second transformer.

The advantages of the invention are that the operational reliability of the ballast system- Fluorescent lamp compared to the known systems significantly improved and a very high number of switching cycles is achieved. By minimizing the filament preheating voltage of the fluorescent lamp their total burning time is extended and reduced the preheating efficiency increases. The ballast for fluorescent lamps according to the invention can with regard to preheating voltage conditions the different types of fluorescent lamps easily adjust.

The invention will be explained in more detail below using an example explained.

The drawing represents a circuit diagram of the ballast in connection with a fluorescent lamp represents.  

The winding (primary) W1.2 of a transformer 2 is connected to the converter 1 . The winding (secondary) W2.2 of the transformer 2 induces the ignition voltage for the fluorescent lamp 5 . The windings (secondary) W3.2 and W4.2 induce the filament preheating voltage of the fluorescent lamp 5 . They are connected to the filaments of the fluorescent lamp 5 via the windings W1.4 and W2.4 connected in series. The timer 3 is connected in series with the winding (primary) W3.4 and the winding (secondary) W2.2 and with the capacitor C1. It is closed for the duration of the filament preheating and opens after a predetermined time in which the filaments of the fluorescent lamp 5 have been sufficiently preheated.

When the ballast and thus the fluorescent lamp 5 are switched on , the contact of the timer 3 is closed, as a result of which a current flows through the winding (secondary) W2.2 of the transformer 2 , the capacitor C1, the winding (primary) W3.4 of the transformer 4 and the timer 3 flows.

The different phase position of the winding W2.2 of the transformer 2 to the winding W3.4 of the transformer 4 enables control of the transformer 4 . When the winding W3.4 of the transformer 4 is actuated, the impedance of the windings W1.4 and W2.4 of the transformer 4 becomes almost zero ohms, that is to say almost the entire voltage between the terminals 1 and 2 or the terminals 3 and 4 of the transformer 2 to the filament of the fluorescent lamp 5 . As a result, a sufficient filament preheating voltage is available in the preheating phase after switching on the ballast on the fluorescent lamp 5 .

Due to the current flow through the winding W3.4 of the transformer 4 and the timer 3 and the lower impedance of the windings W3.4 of the transformer 4 compared to the impedance of the winding W2.2 of the transformer 2 , the voltage breaks across the winding W2.2 of the transformer 2 is generated, almost completely via winding W3.4 of the transformer 4 and the timer 3 together. There is therefore no ignition voltage at the filaments of the fluorescent lamp 5 . At the end of the switch-on phase with a correspondingly long duration of preheating the filaments of the fluorescent lamp 5 , the timer 3 opens. The voltage (ignition voltage) induced by the winding W2.2 of the transformer 2 is therefore available between the terminals 2 and 3 at the filaments of the fluorescent lamp 5 , and the fluorescent lamp 5 is ignited. At the same time, the winding W3.4 of the transformer 4 is de-energized, and the transformer 4 with its windings W2.4 and W1.4 has a current-limiting effect with respect to the heating of the filaments.

This is due to the different phase position of the winding W3.2 of the transformer 2 to the winding W1.4 of the transformer 4 or the winding W4.2 of the transformer 2 to the winding W2.4 of the transformer 4 . The voltage has now dropped sufficiently over the windings W2.4 and W1.4.

The filaments of the fluorescent lamp 5 now have a sufficiently low heating voltage, which means that the operating state of the ballast and the fluorescent lamp is reached.

List of the reference symbols used

1 converter (supplying rectangular pulses)
2 transmitters (first transmitter)
3 timers
4 transformers (second transformer)
5 fluorescent lamp
W1.2 winding (primary)
W2.2 winding (secondary)
W3.2 winding (secondary)
W4.2 winding (secondary)
K1 terminal point
K2 clamping point
K3 terminal point
K4 terminal point
C1 capacitor
W1.4 winding
W2.4 winding
W3.4 winding (primary)

Claims (2)

1. Ballast for fluorescent lamps, characterized in that a power supply in the form of a converter ( 1 ), a transformer ( 2 ) with a winding (primary) (W1.2) and with three or more series-connected windings (secondary) (W2. 2, W3.2, W4.2), one of the windings (secondary) (W2.2) is provided with a capacitor (C1) and each winding (secondary) (W2.2, W3.2, W4. 2) via a further downstream transformer ( 4 ) with its windings (W1.4, W2.4) in a different phase position than the windings (secondary) (W3.2, W4.2), with the filaments of a fluorescent lamp ( 5 ) , wherein a timer ( 3 ) with a winding (primary) (W3.4) lower impedance than that of the winding (secondary) (W2.2) with the capacitor (C1) over the same with this winding (secondary) (W2.2 ) is connected in series. 2. Ballast according to claim 1, characterized in that the converter ( 1 ) is a rectangular pulse-supplying power supply in the form of a keyed power supply, a transistor inverter or another electronic ballast.