FR2542152A1 - Electrical supply and control methods and devices applicable in particular to discharge lamps - Google Patents

Abstract

The invention relates to supply and control circuits using high-voltage transistors. These circuits are applicable in particular to discharge lamps for the purpose of saving energy, improving the quality of lighting, easing starting, increasing the lifetime of the tubes and producing more lightweight and easily positioned equipment.

Description

 Discharge lamps are traditionally supplied from the low voltage network by electromagnetic devices called ballasts.

 The application of switching techniques by power transistors gives a new possibility for the supply and control of these lamps. One of the objectives is to save energy by improving overall efficiency. In addition, the use of medium frequencies makes it possible to solve with greater safety the problems of starting and to prolong the life of the lamps, to improve the quality of the lighting and to realize lighter and more easily posable equipments .

 The object of the present invention is the production of devices making it possible to achieve the desired goals industrially.

 The first device describes in the context of the invention the possibility of modifying the form of the voltage and current signals applied to the lamp to increase its luminous efficiency. The behavior of a medium frequency discharge lamp is indeed very different from its behavior in industrial frequency. The answer is that of a complex impedance, but slightly weakly out of phase and the non-linearity is much less marked than in industrial frequency.

 In the description of the invention, the expression “medium frequency” generally designates the frequency bands significantly higher than the industrial frequency, ranging from a few hundred herts to a few tens of kilohert @, therefore from the upper part of the low frequencies to the lower part of the medium frequencies, that is for example from 800 hertz to 150 kilchertz.

The application of signals conventionally cataloged, and usually delivered by power supplies, such as triangular, exponential sinusoidal signals, lead to a decrease in light output.

 According to the invention, the light output of a medium frequency lamp is increased by the application of a voltage or current signal of square form or of neighboring form called pseudo-square.

 Figure I shows by way of nonlimiting example the fin of such signals.

 However, the application of such a signal in time does not allow stable speeds to be obtained, the lamp @ behaving in the medium term as a negative imped @ nce.

 According to the invention, a current of spoude-square @ is obtained @ u by supposing on the fundamental current a smiling in opposition, of odd harmonics of the fundamental current.

 Figure 2 explains the prostitute. Curve 2a represents the applied fundamental current which is a ps @ udo if @@ - soîde.

 Curve 2b represents the current of odd harmonics. Curve 2c represents the current applied to the lamp.

By varying the level of harmonics, the current applied can take, for example, the forms 2d or 2e.

 By adjusting this rate experimentally, the efficiency of the assembly is optimized.

 According to the invention, an electrical circuit generating harmonic currents permitting to obtain by superposition on the fundamental current a pse @ do-square signal is produced by self-inductors and capacitors arranged in series and whose values are adjusted for that there occurs a phenomenon of resonance generating the current sought.

 FIG. 3 gives by way of example a diagram allowing the implementation of such a resonant circuit. @ is a trapezoidal signal generator supplying the primary of the T transoformer. The secondairo has two windings.

The first feeds the self-inductance LI supplying the lamp L with the fundamental signal p @ eudo-sinusofdal. The resonant circuit consists of the self-inductance L2 and the capacitor C supplied by the second secondary in opposition to the first.

 Trapezofdux signal generators are conventionally constituted using an assembly using a transformer, the primary of which has a midpoint connected to the power supply and its ends connected to the switching transistors, assembly known as push-pull.

 It is known that this arrangement generates elevated ions applied to the collector of the transistor in the blocking phase.

 According to the invention, the power supply to the trapezoidal signal generator comprises two symmetrical voltage sources.

 The transformer primary has only one winding, one end of which is connected to the midpoint of the sources and the other end to the switching transistors. The maximum voltage applied to the transistor in their blocking phase is limited to a value equal to the sum of the source voltages.

 FIG. 4 gives the title of example a diagram making a generator of pseudo-trapezoidal signals.

the source is constituted by a @ phase of the sector distributed between the neutral N and the phase conductor PH. The diodes
D1 and D2 charge capacitors C1 and C2.

 The transformer consists of a primary T1, two low voltage secondary T2 and T3 supplying the circuits a. control 31 and 2 of the transistors EI and E2, and of a high voltage secondary S supplying the lamp circuit.

 Capacitor C3 assists in switching the transistor.

 In the sch @ ma according to FIG. 4, the supply is ensured in a conventional manner by diodes supplying capacitors. This known arrangement has the drawback of creating large peaks of current which can disturb the sector.

These peaks can be attenuated in a known manner by placing a self-inductance in series in the sector, but this self-inductance must be of relatively high value. It then affects the efficiency and creates an inductive phase shift, without eliminating the current distortion. This arrangement therefore generates mains harmonics, a fault already criticized for traditional electromagnetic equipment.

According to an embodiment according to the invention the supply is carried out from the sector without generating harmonics from the sector, by taking from the scctor a sinusofdal current and in phase. The @@ océdé consists, in connecting for a short space of time a self inductance on the sector source. The current established in the self-inductance during this space of time is proportional to the space of time and to the @ imstantan @@ @@ the tomsion sector at this m @@ @ (1 @@@@ p @@
@@ tomps being @ é @@@@@ abl @ dovant the period @ @@@ t @ ur).

In the next phase, the solf-inductanse is con @@@ t @@
@@ a capacitor.

The potent orgy accumulated in the self-inductan @@ p @ nduring the first phase is recovered in the capacitor,
Since the operation is repeated at constant cycle, the average intonity sampled @ during a cycle is proportional to the instantaneous mains voltage. On the time scale of the sector period, the current is therefore at each instant proportional to the voltage.

 The @@ urant fonda @ ental taken from the sector is therefore sinusofdal and @n phase with the sectour tension.

 FIG. 5 shows in 5a the voltage signal U and in 5b the current I in the choke. For the graphical possibility, the time ratio is not respected. In 5c, on an expanded time scale, the current variation in the inductor is shown.

 For carrying out the method, the diagram in FIG. 6 shows, by way of example, the production of a device within the framework of the invention.

 The PD diode bridge is connected to the mains so as to have a single polarity across the terminals of the assembly.

 The inductance L is connected to this unipolar source by the transistor T controlled by the control circuit E fixing the duration of the recurrence cycle and the conductian time. During the blocking phase, the diode D allows the discharge of the energy from the inductance inductor into the capacitors C1 and C2 connected in series. The polss more or less of the power supply are marked on the assembly. Aireuit R is a known switching aid circuit.

 The milisu point, reference 0, can constitute the midpoint of a symmetrical two-pole power supply.

 By way of example, the three pisnts @, 0 and - p @ uvent @@@ set up the supply of the @ é @ erator according to claim four @@ deleting the soft diedes D1 and D2 of FIG. 4 and in @@@ @@@ both the points pertaining to the same landmarks.

 The assembly according to the invention has several advantages. It is possible using known means, and by means of signals S1 and S2 of voltage or current established by known means, to independently or simul tly modify the recurrence period or the time of conduction.

 These modifications affect the average energy per cycle and therefore define the power delivered by the power supply.

 These modifications can be carried out voluntarily, locally or at dictation by known means, it is possible to adjust characteristic quantities, such as voltage and / or current at given valours or according to given laws.

 FIG. 7 shows by way of example a diagram carrying out advantage @ uses operations described above.

 The elements PD, T. L, D, C @ and C2 have the same references as coux in FIG. 6.

 Auxiliary power supply AA. the relator xati @ n OS, the UH univibrator and the command C. explain the sub assembly of co @@@ ande B of Figure 6.

 The transistor M acts on the conduction time.

 By the pot @ ntiometer @M, it is possible to manually adjust the power of the power supply.

 The RV circuit made up of Zenner diodes regulates the power supply to a given value, in a @ domain of fluctuations of the load or the voltage @ @ tor.

 The device described generates in the output medium frequency current signals corresponding to the resistor frequency and its harmonics.

 These signals can in certain cases be considered as disturbing, it is possible to eliminate them or to attenuate them strongly by a device putting in covers two symmetrical assemblies, whose function is offset by a half @ y @ le of reourrance. By judiciously adjusting the mounting parameters, the current signals from the two m @ ntges enter at any point for the result of addition a @@ urant equal to the value of @ rète de @hague @ourant @@ nstituent. The residual of the operation being more than @@ t @@ frequen @@ can be @@@ stunned @@@@@@ men p @ rturbateur or be easily eliminated by a reduced filter eirouit @ t.

 Figure 8 shows the principle of cot @ so nation. @a and 8b are the currents of each circuit and 8c the resulting current.

 FIG. 9 represents by way of example the diagram of a device carrying out the operation described above.

 The OS oscillator symmetrically attacks the circuits @@ A and UNB driving the circuits COA and COB ot the transistors A and B respectively.

 In the example embodiment, the line voltage is rectified by point 1. The transistor 3 is controlled at medium frequency by a recurrent square signal with constant time ratio. The energy is recovered in the capacitors 6 and 7 through the diode 5. The circuit est is a switching assistance circuit. The transofrmator 9 and the pilot devices 10 and 12 of the transistors 11 and 13 constitute a trapescidal generator. The @@ oc @ daire of the transofrmator feeds the lump 14 through the main self 15 and the auxiliary self 16 granted to the cond @@ sator 17.

Claims (7)

1 - Method for increasing the light output of a discharge tube  characterized in that it comprises the use, for @ 'feeding the tube,  a square or pseudo-square signal (Figure 1). 2- A method according to claim 1, characterized in that it comprises the super  position, for the tube supply, of a fundamental current and currents  harmonics (Figure 2, 2a and 2b).  (figure 3).  current an oscillating circuit consisting of a choke and a capacitor  characterized in that it comprises in addition to the self inductance limiting the  3-Device for implementing the method according to claims 1 and 2,  constant recurrence (Figure 5).  tation characterized in that it involves the use of an inductance inductor connected to the mains source for a short conduction time with cycle of  discharge tube, a sinusot-dal current and in phase with the dialimen voltage 4 Method for withdrawing from the sector, for example to supply a 5 - device for implementing the method according to claim 4 characterized  in that it uses a transistor T electronic circuit, Eiloté by a circuit of  recurrent pulse control, a self inductance L, a diode D and  capacitors C1 C2 (Figure 6). 6 -Device for implementing the method according to claim 4 characterized  in that it uses two electronic circuits with transistors A and 8 controlled by  an OS recurrent pulse control circuit, two inductors  LA and Le, two diodes and capacitors C1 and C2. (figure 9).  1, 2, 3, 4, 5 and 6.  individually or in combination the methods and devices according to claims  7-Device for supplying a discharge tube, characterized in that it uses