FI63314B - ELEKTRONISKT FOERKOPPLINGSDON FOER GASURLADDNINGSLAMPA - Google Patents

Description

1 63314

Electronic mains connection device for gas discharge lamp.

Electronic lighting for gas discharge lamps.

The invention relates to an electronic mains connection device for a gas discharge lamp, which acts as a stabilizing current limiting element and comprises an inverter circuit which converts the mains power from the rectified mains or other direct current to such a high frequency that the impedance of the discharge lamp is of normal resistance.

The invention thus relates to a reversing connection implemented in a semiconductor, which is applied in the mains connection device of gas discharge lamps to supply current to the lamp.

In this context, gas discharge lamp means those lamps generally used for lighting, the internal impedance of which in normal 50 or 60 Hz AC operation has a negative resistance in nature and which thus require a current limiting element to stabilize the gas discharge. Such lamps are mainly fluorescent lamps, high pressure and low pressure sodium lamps, mercury vapor lamps and halogen lamps.

Several different electronic circuit solutions with semiconductors and passive components are already known, which are suitable as ballasts for gas discharge lamps. These solutions are based on the conversion of direct current generated in one way or another into alternating current with a frequency substantially 50 Hz higher. At this higher frequency, the lamp is supplied with the electrical energy required for its gas discharge. The achievable advantages are an improvement in the light efficiency of the lamp due to the higher operating frequency, a reduction in the mechanical size of the required electromagnetic components and thus a reduction in the ballast's own dissipation power, as well as a reduction in the ballast weight. A clear advantage is also that it is usually easy to combine the light level control of the lamp with an electronically implemented ballast solution. In most electronic ballast circuit solutions, sufficient voltage is easily generated to ignite the discharge lamp without a separate igniter. In addition, no electronic interference is generated from the electronic ballast 2 63314 if the operating frequency is selected above the hearing range. Disturbing flicker, or flicker, can be removed from the light emitted by the lamp. The electronic ballast can also be implemented in such a way that the curve shape of the current drawn by the device from the AC mains is almost sinusoidal and the power factor cos f * 1, in which case no separate components are needed to compensate the mains current.

Previously known electronic ballast implementation solutions usually include some impedance to limit the lamp current? a choke, a capacitor, a resistor or a combination thereof with a lamp and a supply voltage source connected in series (e.g. DE-A-2 550 550).

It is physically known that the impedance of a discharge lamp changes from a negative resistance to a normal resistance when the lamp is operated at an alternating voltage with a frequency in the range of about 1 kHz to 150 kHz. Partly based on this phenomenon, it is known to use the so-called blocking oscillator coupling in one form or another (e.g., U.S. Patent Nos. 3,629,648, 3,906,302, and 4,168,453). In such a connection, the lamp is connected directly to the supply voltage for the half period in which the switching element (e.g. a transistor) conducts, and the voltage at the lamp terminals is reversed for that part of the period in which the switching element is in a non-conducting state. This opposite voltage is generated by the excitation energy charged to the inductance connected in parallel with the lamp, which is discharged through the lamp when the switching element opens.

The present invention is also based on a circuit solution for operating discharge lamps at the aforementioned relatively high frequencies at which the discharge lamp behaves like a normal resistance. However, unlike the previously known circuit solutions, the circuit solution according to the invention does not need any inductive or capacitive means for stabilizing the gas discharge of the lamp.

In the tests performed, it has been found that the discharge lamp can be operated by connecting it directly to the supply voltage source by means of reversing switches, changing the polarity of the lamp in each half cycle. The switching frequency must then be so high that the discharge lamp behaves like a resistor.

However, the mode of operation described above is not stable, and the lamp tends to have a "robbing phenomenon" substantially slower than the length of the operating frequency period, as a result of which the current tends to increase while the voltage remains constant. To avoid this phenomenon, the invention involves preventing such a current ripple phenomenon by measuring the value of the current flowing through the lamp and using a feedback control to keep this current value at the desired value. In the feedback, the filtering time constant of the measured variable can be used, which can be about 0.2 ms, for example, at an operating frequency of 40 kHz.

The features of the invention are set out in the appended claims.

The solution according to the invention achieves the following advantages: 1. No winding components or capacitors dimensioned for the main current are required.

2. Capacitors with specified operating temperature limits are not required, making the ballast suitable for use at a higher operating temperature, eg when placed directly in connection with a lamp.

3. The ballast is inexpensive because the expensive components mentioned above are omitted.

4. The above-mentioned components are also the largest of the known ballasts, so without them the ballast can be built smaller and used in smaller spaces.

5. The main circuit of the ballast can be implemented entirely on semiconductors.

In the following, some embodiments of the invention will be described in more detail with reference to the accompanying drawings, in which Fig. 1 shows a schematic diagram of a network connection device according to the invention.

Figure 2 shows in principle a diagram of another embodiment of the invention.

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Figures 3 and 4 show, in a manner similar to Figure 1, further modifications of the invention.

Figure 5 shows a circuit diagram of a network interface device according to an embodiment of the invention, in which only the most essential components are shown.

In Fig. 1, the gas discharge lamp 1 is connected to a direct current source by means of four electronic switches 3-6 so that these switches form an inverting circuit by means of which the polarity of the supply voltage at the terminals of the lamp 1 is changed at a high frequency in the range of about 1 kHz ...

150 kHz. This change of polarity takes place in such a way that, when the switches 3 and 4 are closed, the switches 5 and 6 are open and when the latter switches are closed, the former are opened. In addition, there may be an adjustable length of time between closing and opening the switches, with all switches open. This can be used to adjust the light level of the lamp. As already stated, the circuit solution of the ballast according to the invention does not include any additional current-limiting impedance element, but only the own resistance-like impedance of the lamp 1 in question is used to limit the current. at a high switching frequency. However, without the additional arrangement according to the invention, this would not be possible, because the current of the lamp 1 would tend to be robbed for a substantially longer period of time than the switching circuit. In order to eliminate this robbery phenomenon, the invention provides a feedback control in which the current of the lamp 1 is sensed by a current transformer 7 or other current measuring method such as a resistor, and on the basis of this current value

The connection shown in Fig. 2 corresponds in other respects to that shown in Fig. 1, but the lamp 1 is connected to an inverter connection and a direct current source via a saving transformer 9 which raises the supply voltage of the lamp 1 relative to the voltage of the power supply. In addition, the saving transformer 9 can be used to anneal the cathodes of the lamp 1 to improve the flammability sensitivity of the lamp. In addition, the saving sounder 9 can act to ignite the lamp 1 to generate a sufficient ignition voltage peak.

The embodiment of Figure 3 differs from that shown in Figure 1 in that switches 6 and 4 are replaced by capacitors 10, whereby the circuit is simplified. This can be used in those applications where the temperature limit set by the capacitors is not relevant.

In the embodiment of Fig. 4, the switches 3 and 6 of the circuit solution of Fig. 1 have been replaced by a saving transformer 11, to the central output of which the other terminal of the power supply is connected. The magnetization inductance of the saving transformer 11 can be used in a manner known per se to generate an ignition voltage peak for the lamp 1. A resistor 16 measures the current flowing through the lamp in another direction, which measurement method replaces the current transformer in other embodiments.

Fig. 5 shows a further developed embodiment corresponding to Fig. 3, in which the lamp 1 has an inductance 13 providing an ignition voltage peak and a surge protection device 14 in parallel. The current transformer 7 senses the current flowing through the lamp 1, which current value is passed through the rectifier and filter circuit 15 8. On the basis of this current value, the control unit 8 gives control pulses to the control electrodes of the transistors acting as switches 3 and 5, the duration and / or operating frequency of which change as necessary to keep the current through the lamp 1 constant. In order to set this constant current to different values for controlling the illumination provided by the lamp 1, the control unit 8 includes a control device 12 with which the opening times of the switching transistors 3 and 5 or their switching frequency can be influenced.

Claims (7)

1. An electronic gas discharge lamp mains connection device, which acts as a stabilizing current limiting element and to which an inverter connection, which terminates. the driving voltage of the lamp from rectified mains voltage or other DC voltage to high frequency, that the impedance of the discharge lamp is of the nature of normal resistance, characterized in that the connection device does not contain current limiting impedances, but has limited the current limit by means of the lamp's own resistance-like impedance for both half-periods, whereby the current limitation for a longer period than the period of the inverter operation is realized with the feedback control (7, 8) of the lamp current, which control controls the openness times and / or the operating frequency of the inverter head (3). , 6). 2. A power supply device according to claim 1, characterized in that the lamp (1) is connected to the inverter connection by means of a saving transformer (9), so that the voltage of the lamp is greater than the voltage of the current source (Fig. 2). 3. The mains connection device according to claim 1 or 2, characterized in that the two connections of the inverter connection between the one pole of the lamp and the poles of the power source have been replaced by capacitors (10) (Figs. 3 and 5). 4. A power supply device according to claim 1, characterized in that the two connections of the inverter connection between the one pole of the lamp and the poles of the power source have been replaced with a saving transformer, to which the center outlet of the power supply's one-pole is connected (Fig. 4). 5. A network connection device according to any one of the preceding claims, characterized in that, during iterating, the filtering time constant for the measuring quantity of the current passing through the lamp is used.