FI63146B - FOERFARANDE FOER REGLERING AV EN URLADDNINGSLAMPAS LJUSNIVAO OCH EN ELEKTRONISK NAETANSLUTNINGSANORDNING FOER FOERVERKLIGANDE AV FOERFARANDET - Google Patents

Description

1 63146

A method for adjusting the light level of a discharge lamp and an electronic mains connection device for carrying out the method. - For the purpose of regenerating the power supply lamp, the power supply and electronic power supply for the 5-day operation of the power supply.

The invention relates to a method for adjusting the light level of a discharge lamp by means of an electronic mains connection device which limits the current of the discharge lamp. The invention also relates to an electronic network connection device for carrying out the method, two alternative embodiments of which appear from the preamble of the appended claims 2 and 4. Alternative embodiments of the method are set out in the appended claims 1 and 3.

15

An electronic mains connection device for limiting the current of a discharge lamp is known from the applicant's previous Finnish patent applications Nos. 812930 and 813297. The general theoretical background of this type of electronic mains connection device is presented in more detail in the applicant's Finnish patent application No. 811774.

The problem to be solved by the invention is to provide a control of the light level of the lamp in connection with a mains connection device based on a high-frequency resonant circuit 25.

The problem is solved on the basis of the features of the invention set out in the appended claims.

In the following, two alternative embodiments of the invention will be described in more detail with reference to the accompanying drawings, in which Fig. 1 shows a reduced circuit diagram of a first embodiment of the invention and Fig. 2 shows a reduced circuit diagram of a second embodiment of the invention.

2 63146

To simplify the presentation, only the most essential components are shown in Figures 1 and 2.

The embodiment of Figure 1 has a high-frequency oscillator formed between the + and - terminals of the direct current and the terminals of the lamp 8, comprising two transistors 1 and 2 connected in series, which are arranged in phase operation as will be described later. Diodes 12 and 13 are connected in series with transistors 1 and 2. The second terminal of the primary winding 4 of the base control transformer 3 of transistors 1 and 2 is connected between transistors 1 and 2 and the other terminal is connected via induction winding (choke) 7 to the second terminal of lamp 8. The second terminal 15 of the lamp 8 is connected to the opposite terminals of the power supply by resonant capacitors 10 and 11 and adjacent voltage limiting diodes 23 and 24. There is an electrolytic capacitor EC between the + and - terminals of the power supply. In addition, in parallel with the lamp 8, a capacitor 9 is connected between the opposite poles of the filaments 20 of its electrodes, which determines the operating frequency and voltage during ignition. Instead, during operation, the capacitors 10 and 11 generate the main resonant capacitances in the free-oscillating series resonant circuit, which also includes the inductances formed by the windings 4 and 7.

The secondary windings 5 and 6 of the base control transformer 3 are connected to the bases of the transistors 1 and 2 so that they receive control phases in opposite phases. Then, when the second transistor 30 is conductive, the second transistor is non-conductive and vice versa. The significance of the diodes 12 and 13 is that their output voltage contributes to the simultaneous conduction of the transistors 1 and 2. The protection diodes 14 and 15 provide a path for the current of the inductance 7 when both transistors 1 and 2 are in a non-conductive state.

In order to adjust the light level of the lamp 8, an additional secondary winding 17 is arranged on the core 16 of the base control transformer 3 in accordance with the invention, in parallel with which a series connection of a thyristor 19 and a diode 18 is connected. The control electrode of the thyristor 19 is connected to a control device 20-22 for bringing the thyristor 19 to a conductive state for short-circuiting the winding 17 every desired phase of the second half cycle. The operation of the control unit is as follows. Through the diode 18 and the control potentiometer 20, the capacitor 21 is charged every other half cycle at a rate whose time constant depends on the control value of the potentiometer 20. When the capacitor 21 is sufficiently charged, the bipolar transistor 22 is guided to conduct so as to obtain a control voltage to trigger the thyristor 19 to a conductive state. As the secondary winding 17 closes oi, the base control voltage of the windings 5 and 6 decreases, respectively. the base current of the transistor 1 or 2 which was conducting in the half-cycle becomes momentarily in the opposite direction, because the collector current can flow better through the base than through the emitter due to the above-mentioned low base voltage. In this case, the the transistor is quickly driven to a non-conductive state. This shortening of the base current duration of the second tran-20 resistor slightly increases the operating frequency of the resonant circuit. The increase in frequency means that the inductance 7 is more resistant to the flow of current. As the frequency increases, the current of the capacitor 9 also increases. Em. due to the reasons, the current of the fluorescent lamp 8 pie-25 increases and the light dims, while the annealing power of the electrodes of the lamp increases, which prevents the lamp from turning off at low light level control values.

In this embodiment, the current is also limited in the second half of the period 30 due to the saturation of the core 16 of the base control transformer, which is caused by the current of the coil 17 moving to the other saturation edge of the curve.

35 The disadvantage of the control principle described above is the reduction in efficiency when the light level is reduced. This switching principle has also not been able to completely eliminate the problem with fluorescent tubes that with low light level control values, darker and brighter areas appear in the fluorescent tubes. "Balls". This phenomenon does not interfere with the actual lighting, but with visible fluorescent tubes, its complete elimination would be desirable. What causes this problem of ball formation is not known in more detail and so far it has been considered impossible to adjust the so-called thin fluorescent tubes so that said phenomenon does not occur. Surprisingly, however, it has been found that with the control principle of Figure 2 described below, this formation of "spheres" has been substantially reduced while achieving better efficiency in reducing the light level compared to the embodiment of Figure 1.

The embodiment of Figure 2 differs from the embodiment of Figure 1 only in the base control transformer 3. In other respects, the same reference numerals are used as in Fig. 1 and reference is made to the description of the embodiment of Fig. 1.

Both transistors 1 and 2 have their own separate base control transformers 3a and 3b, the primary windings 4a and 4b of which are connected in series as part of said series resonant circuit. The secondary winding 5 of the transformer 3a controls the transistor 1 and the secondary winding 6 of the transformer 3b controls the transistor 2. The additional secondary winding 17 to be short-circuited by the control circuit 25 19-22 is arranged only on the core 16a of the transformer 3a. Transistor 2, which is not regulated, receives a sufficient base current because, due to the resonant circuit, the value of the current at the moment of disconnection is small. The base current of the adjustable transistor at the moment of disconnection is strongly negative, significantly reducing disconnection losses. In this case, the losses of the transistor are also reduced compared to those operating with one base control transformer. In the embodiment of Figure 2, the operating frequency also increases less, as a result of which the switch losses decrease.

The advantage of both embodiments described above is that the control circuit is galvanically isolated from the electronic ballast.

35

Claims (5)

A method for controlling the level of light of a discharge lamp with a current limiting electronic current connection device of a discharge lamp, which includes a high frequency oscillator consisting of two series-connected transistors (1, 2), a base control transformer (3) coupled between them. ), a primary winding (4) connected in series (7) and a capacitor (10, 11) located in the latter series circuit, located between the lamp (8) and the current source, characterized in that in the series resonant circuit, consisting of the primary winding of the base control transformer (4), the throttle (7) and the capacitor (10, 11), the current in the transistor couplings (1,2) is controlled by short-circuiting the secondary winding (17) of the base control transformer (3), the second half period the current is limited to the base by overloading the core control transformer core (16). 2. An electronic power supply device for a discharge lamp for limiting and controlling the current by a method according to claim 1, to which the connecting device comprises a high frequency oscillator consisting of two in series switched transistors (1, 2), coupled between them. a base control transformer (3), a throttle (7) connected in series with the primary winding (4) of the transformer and a capacitor (10, 11) located in the latter series circuit, located between the lamp (8) and the power source, noticeable therefrom, that between the base control transformer 30 (3) the secondary winding (17) poles are coupled to an electronic coupling (19), to whose control electrode a control device (20, 22) is provided to bring the coupling (19) to the conductive state in the desired phase of every two half periods. 35 3. A method for controlling the light level of a discharge lamp with a current limiting electronic power switching device, including a high frequency oscillator, 63146, consisting of two in series connected transistors (1, 2), between these coupled base control transformers (3a, 3b) , a series-coupled choke (7) of the transformer winding (4a, 4b) and a capacitor (10, 11) located in the latter series circuit 5, located between the lamp (8) and the current source, characterized in that in the series resonant circuit constituted of the primary winding transformers (4a, 4b), the throttle (7) and the capacitor (10, 11), the current in one of the transistor couplings (1) is controlled by short-circuiting the secondary winding (17a) of its base control transformers (3), correspondingly transistor coupling has been conductive for the desired time, and that the base control transformer (3b) of the other transistor coupling (2) allows it to pass through the corresponding transistor coupling (2). the resonant pulse oscillates according to normal function until the end. An electronic power supply device for a discharge circuit for limiting and controlling the current by a method according to claim 3, to which the connecting device comprises a high frequency oscillator consisting of two in series switched transistors (1, 2), between these coupled base control transformers. (3a, 3b), a throttle (7) connected to the primary windings (4a, 4b) of the transformers 25 and a capacitor (10, 11) located in the latter series circuit, located between the lamp (8) and the current source, characterized in that , that between the poles of the secondary winding (17a) of one of the base control transformers (3a) is connected an electronic coupling (19), to whose control electrode a control device (20, 22) is used to bring the coupling (19) into a conducting state in the desired phase of each other half period. 35 5. A network connection device according to Claim 2 or 4, characterized in that said electronic connection is a thyristor (19) and said control device.