Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Reexamination Certificate
2000-06-14
2001-10-30
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
C315S307000, C315S360000, C315S362000, C315S2090SC, C315S244000, C315S224000
Reexamination Certificate
active
06310447
ABSTRACT:
TECHNICAL FIELD
The invention relates to a method for operating at least one fluorescent lamp with the aid of an electronic ballast.
I. PRIOR ART
EP-B-0 801 881 discloses such a method for operating at least one fluorescent lamp with the aid of an electronic ballast which has a half-bridge circuit coupled to a rectifier circuit and having two power transistors which are in series with one another and are activated alternatively. A load circuit is connected to the common junction point of said power transistors, which forms the output of the half-bridge arrangement, which load circuit contains the at least one fluorescent lamp and the load current of which load circuit is monitored. To that end, a control and regulating circuit is provided in the form of an integrated circuit. This circuit is equipped with a monitoring circuit for continuously monitoring the load current and with a drive circuit, which is regulated in a high-frequency manner derived therefrom, for the power transistors. In the case of the known ballast, a timer is started in a defined manner each time the lamp is started and each time a disturbance occurs during lit operation, which timer generates a time base for subsequent control and regulation operations. On account of this time base, respectively predetermined, different reference levels for the load current to be detected are set in the monitoring circuit or automatic disconnection of the electronic ballast for a predetermined, limited period of time is prepared. The monitoring circuit compares the instantaneous value of the load current with the respectively activated reference level and emits a respective output pulse once this reference level has been reached. These output pulses identify normal or alternatively faulty states in the load circuit as a function of their occurrence or failure to occur during predetermined periods of time defined by the timer. By means of these output pulses, the lamp current is regulated as a function of time via the regulated drive circuit in the event of an undisturbed operating state, or an already prepared automatic disconnection of the electronic ballast is triggered in the case of a fault.
Fully electronic ballasts of the type mentioned are universal devices which can be used advantageously for conventional AC power supply voltages in a relatively broad tolerance range, a broad range of permissible power supply frequencies and, finally, are even suitable for DC voltage supply. However, one of the essential problems having to do with the application of electronic ballasts is that use is made of different lamp types in circuits which also vary in some instances, e.g. including a plurality of fluorescent lamps, which brings about a corresponding type diversity of the ballasts which are specifically adapted to these applications. It is no easy matter, therefore, to comply with this type diversity by means of as far as possible a single large scale integrated circuit in which the drive and regulating circuit of the ballast is combined. As a compromise, with an intrinsically desirable high integration level partly being obviated, corresponding control inputs of the integrated circuit are adapted by externally connected components.
Thus, by way of an example, in the case of the electronic ballast described above, the magnitude of the ignition voltage is not freely adjustable, since this is determined by a fixed threshold value defined internally in the integrated circuit. In the case of the known electronic ballast, too, the adaptation of the ignition and/or preheating voltage that is permissible within the scope of a tolerance range that is still manifested, which adaptation is necessary for different applications can at best be achieved by corresponding external circuitry of the integrated circuit and, for that reason, then only with a corresponding outlay.
II. SUMMARY OF THE INVENTION
Therefore, one sub-object underlying the present invention is, in a development of the method for operating at least one fluorescent lamp as mentioned in the introduction, to specify a further embodiment which, in addition to reliable regulation of the load current, even in the case of aged fluorescent lamps, in particular opens up the possibility of reliably controlling even those applications in which lamp types having a critical ignition behavior are intended to be used.
A further sub-object underlying the present invention is to develop the electronic ballast of the type acknowledged above in such a way that, despite a corresponding integration level of its drive and regulating circuit and thus reduced outlay for the external circuitry, it can be used to a broad extent reliably in a wide variety of applications merely by simple adaptation.
The solutions according to the invention enable a simple measure to be employed to extend the tolerance range of the electronic ballast with regard to the monitoring of the load current. This property is advantageous particularly when the load circuit comprises a lamp circuit having a plurality of fluorescent lamps. In the case of such lamp circuits, and also in the case of fluorescent lamps having a critical ignition behavior, it is difficult to reliably control the tolerance range by means of a given integrated circuit. In the integrated circuit, tolerance ranges cannot readily be predetermined with sufficient breadth, because any critical operating states, such as e.g. reluctance to ignite and/or ignition failures in the case of aged fluorescent lamps, are then no longer detected in an entirely satisfactory manner. Another possibility, mainly that of equipping the electronic ballast with a predetermined integrated control and regulating circuit and nevertheless operating even such critical lamp circuits therewith, would consist in adapting, with a degree of effort, the external circuitry of the integrated circuit to the respective application. In view of the fact that electronic ballasts are nowadays products which, under high cost pressure, largely have to be produced in an automated fashion, such a solution is uneconomical.
According to the invention, this problem is solved in an elegant manner by means of a relatively simple circuit measure. The load current signal that is to be monitored in the control and regulating circuit has superposed on it a DC signal from an additional DC source, the level of which DC signal is adjustable in a manner dependent on the lamp circuit respectively used. Since the preheating voltage and in particular the ignition voltage are critical in these applications that are difficult to control, it suffices to provide this superposition merely for the ignition period which begins at the end of the preheating period.
As specified in subclaims, the level adaptation of the additional DC source can be achieved using simple means and reliably by virtue of the fact that the level to be set is derived internally from the current flow through the adaptation resistor, which, as an external resistor, is assigned to the oscillator which is controlled in a current-dependent manner, and the blanking interval of the half-bridge circuit is defined by the dimensioning of said resistor. A circuit adaptation to different lamp circuits in the load circuit can thus be performed by the corresponding dimensioning of a single non-reactive resistor.
In a development of the solution according to the invention, it is particularly advantageous if the load current regulation that is absolutely necessary for individual operating states of the electronic ballast is deactivated occasionally and insofar as the current limiting is canceled during the ignition period. To that end, a further threshold is provided in the monitoring circuit, the level of which further threshold lies between those for the preheating threshold and the ignition threshold. The further output pulses that are emitted by the monitoring circuit during the evaluation of the load current signal with regard to said further threshold set an inhibiting switch, which is cyclically reset and, in the activated state, in each case interr
Bessone Carlo S.
Patent Treuhand-Gesellschaft fuer elektrische Gluelampen mbH
Philogene Haissa
LandOfFree
Method for operating at least one fluorescent lamp, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for operating at least one fluorescent lamp, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for operating at least one fluorescent lamp, and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2574216