EP1276355A2 - Circuit arrangement to determine the pre-heating power - Google Patents

Abstract

The circuit arrangement has a half bridge arrangement whose output signal is fed to a load circuit (LK) for connection to a fluorescent lamp (LA) with helical electrodes, a preheating device for the electrodes and a preheating power determination device. The power flowing in the load circuit during preheating is determined by the power determination device. AN Independent claim is also included for the following: a method of operating a fluorescent lamp.

Description

Technical field

The present invention relates to a circuit arrangement for operation a fluorescent lamp comprising a half-bridge arrangement, the output signal can be fed to a load circuit, with a to the load circuit Fluorescent lamp with filament electrodes can be connected, a preheater for preheating the filament electrodes of the fluorescent lamp and a power determining device for determining a preheating power value, which is a measure of the performance during preheating is implemented in the spiral electrodes. It also concerns a corresponding one Method of operating a fluorescent lamp.

State of the art

The present invention deals with the problem that fluorescent lamps are produced which have different electrical data with the same dimensions or the same sockets. For example, one type is optimized for the electrical power converted and thus for the luminous flux emitted by the lamp, while another type is designed for high efficiency and thereby converts significantly less electrical power. Since the dimensions of corresponding lamp types in a given luminaire can be interchanged, control gear has been developed that automatically recognizes the type of lamp used and sets the correct operating parameters. Such a circuit arrangement for the automatic detection of the lamp type used is known from the company Energy Savings; of which the essential part is shown in Fig. 1. Here, a half-bridge arrangement, which comprises the two switches S1 and S2, is driven by an intermediate circuit voltage, which is usually a direct voltage of the order of 400 V. The center of the half-bridge arrangement is connected to a lamp inductor L _S , which serves to limit the current after the lamp LA has been ignited. Two capacitors C _K1 , C _K2 serve as coupling capacitors. In addition to the lamp choke L _S already mentioned, a load circuit includes a resonance capacitor C _R. They are used to generate the voltage required to ignite the lamp.

The lamp LA comprises two filament electrodes W1, W2, which are preheated as follows: The lamp inductor L _S forms a transformer together with an inductor L1 of a preheating circuit VK. As long as the lamp LA has not yet ignited, the preheating circuit VK can be supplied with energy via the lamp choke in this way. A switch S3 is also arranged in the preheating circuit VK and is closed for the purpose of switching on the preheating. When switch S3 is closed and lamp LA is not ignited, a current is driven through preheating circuit VK by inductance L1. This flows through an inductor L2, which forms a transformer as the primary inductor with two further inductors L21, L22. As soon as current flows through the inductor L2, current also flows through the inductors L21 and L22, as a result of which a current flow is generated through the coil electrodes W1 and W2, which results in the coil electrodes W1, W2 being heated, ie preheating them. The magnitude of the currents I ₂₁ , I ₂₂ depends on the impedance of the spiral electrodes W1, W2. The currents I ₂₁ , I ₂₂ are in a fixed ratio to the current I _{1 of} the preheating circuit VK. By measuring the voltage drop U _R1 across a measuring resistor R ₁ , the current I ₁ can be determined and thus it can be determined which type of lamp is used in the circuit arrangement. For the automatic control of the half-bridge arrangement, the voltage U _R1 dropping across the resistor R _{1 is} fed to a processor which adjusts the operating parameters in accordance with the determined lamp type. After preheating the lamp LA, the lamp is increased so much by driving the switches S1, S2 of the half-bridge arrangement with a suitable frequency that the voltage applied to the lamp as a result of the resonance circuit formed by the lamp inductor L _S and the resonance capacitor C _{R is} such that it becomes Ignition of the lamp LA comes. After the lamp LA has been ignited, the switches S1, S2 of the half-bridge arrangement are operated at a frequency which corresponds to the normal operation of the lamp. As is obvious to a person skilled in the art, the circuit arrangement shown in FIG. 1 uses an actively switched preheating circuit VK.

Presentation of the invention

The object of the present invention is a circuit arrangement of the type mentioned in such a way that an automatic Detection of the lamp type used in the circuit arrangement also for circuit arrangements with a preheating circuit that is not activated is made possible. Furthermore, a corresponding method for Operating a fluorescent lamp can be provided.

These tasks are solved by a generic circuit arrangement, in which with a power determination device during of the preheating power flowing into the load circuit can be determined.

The procedural object is achieved by a method in which first a fluorescent lamp with the supply of energy from a Half-bridge arrangement is preheated in a load circuit, the Fluorescent lamp, which has filament electrodes, connected to a load circuit is. A preheating power value is determined, which is a measure of represents the power flowing into the load circuit during preheating. In Depending on the determined preheating power value, one of at least selected two processes for operating the circuit arrangement.

The solutions according to the invention are based on the knowledge that at Circuit arrangements with the preheating circuit not activated which are in the Load circuit flowing power is correlated with that in the circuit arrangement used lamp type as long as the lamp is not ignited. In particular the shares implemented in the load circuit can be calculated, since the values of the components are known and constant. In this respect it hangs in the power flowing in the load circuit essentially depends on the impedance of the Spiral electrodes, so that in the conclusion due to the load circuit flowing power can be concluded which type of lamp is used has been. Depending on the type of lamp found, you can then the appropriate operating parameters are set. In contrast to the Known circuit arrangement shown in Fig. 1, the preheating in circuit arrangements according to the invention except with preheating inductors also with preheating resistors or by forming a Resonance circuit. In this respect, the range of possibilities of preheating significantly expanded. In the circuit arrangement according to the invention the lamp is preheated, ignited and operated normally one and the same circuit arrangement, only by varying the frequency, with which the switches of the half-bridge arrangement are opened and closed become. Advantageously, the power determination device the current flowing in a half-bridge branch is evaluated. For example, using a measuring resistor or an inductor this allows the load circuit to be connected in a particularly simple manner determine flowing performance.

The circuit arrangement preferably further comprises a sequence control, which depending on the preheating power value one of at least selects two processes for operating the circuit arrangement. By this measure can ensure that the circuit arrangement automatic, i.e. without operator interaction, with operating parameters is operated that correspond to the determined lamp type.

The at least two processes for operating the circuit arrangement can Operating modes of the circuit arrangement for preheating and / or ignition and / or normal operation of the fluorescent lamp or measures include defective or unused fluorescent lamp.

This ensures, on the one hand, that when the fluorescent lamp type is detected the lamp is suitably preheated, ignited or normal is operated, i.e. without the circuitry or the fluorescent lamp Takes damage. It can also be used to detect whether the lamp filaments are intact or whether a fluorescent lamp at all is used. In contrast, in the prior art, turn detection is relative time and cost consuming, so that in the circuit arrangement according to the invention, in which the active power is recorded in the load circuit anyway, one noticeable material savings and an electrically more economical configuration of the load circuit is possible.

A particularly preferred embodiment of the circuit arrangement according to the invention further comprises a control or regulating device, with the power determination device also in normal operation the fluorescent lamp the power flowing into the load circuit can be determined, and the control or regulating device is designed depending from this determined power parameters for normal operation of the circuit arrangement to change. A control or regulation in the load circuit flowing power in normal operation is necessary because the fluorescent lamp operated at different operating points depending on the temperature will, i.e. that especially shortly after turning on the working point has different current and voltage values than at operating temperature. In this respect, the lamp is not a constant load Existing service entry can also be used for a suitable design Solution to the problem according to the invention can be used. The control or control device can be designed, the determined preheating power value against a setpoint to compare the parameters for the Change normal operation depending on the result of this comparison.

The sequence control particularly preferably comprises a bistable stage, in order to One of two operating modes depending on the determined preheating power value to select the circuit arrangement. This variant is special Suitable for circuit arrangements in which only two types of lamps can be used, which correspond in terms of their dimensions. In this In this case, this simple solution is sufficient to automatically insert the one used Recognize the lamp type and set the associated operating parameters.

Further advantageous developments of the invention are in the subclaims Are defined.

Description of the drawings

Fig. 1

einen Teil einer aus dem Stand der Technik bekannten Schaltungsanordnung mit aktiv geschaltetem Vorheizkreis;

Fig. 2

eine erste Ausführungsform einer erfindungsgemäßen Schaltungsanordnung und

Fig.3

in schematischer Blockschaltbilddarstellung ein Betriebsgerät zum Betreiben einer erfindungsgemäßen Schaltungsanordnung.

Exemplary embodiments of the invention are described in more detail below with reference to the accompanying drawings. They represent:

Fig. 1

part of a circuit arrangement known from the prior art with an actively switched preheating circuit;

Fig. 2

a first embodiment of a circuit arrangement according to the invention and

Figure 3

in a schematic block diagram representation of an operating device for operating a circuit arrangement according to the invention.

FIG. 2 shows a circuit arrangement according to the invention, elements and sizes which correspond to those of FIG. 1 being designated with the same reference symbols. The circuit arrangement shown in FIG. 2 also comprises a half-bridge arrangement with two switches S1, S2, which are fed by a voltage Uz. The center point of the half-bridge arrangement is connected to a lamp inductor Ls, the other end of which is connected to a first filament electrode W1 of the lamp LA. The lamp choke Ls forms a resonance circuit for igniting the lamp LA with a resonance capacitor C _R , which is connected between the coil electrode W1 and a second coil electrode W2. Two capacitors C _K1 , C _K2 in turn serve as coupling capacitors. The power flowing into the load circuit LK is correlated with a current I _RM which flows through a measuring resistor R _M arranged in a half-bridge branch of the half-bridge arrangement. The voltage U _RM dropping across the measuring resistor R _M is preferably evaluated to determine the power flowing into the load circuit LK.

In the circuit arrangement shown in Fig. 2, no actively switched Preheating circuit for preheating the spiral electrodes W1, W2 Fluorescent lamp LA used. Rather, the operating states of the Fluorescent lamp LA such as preheating, ignition and normal operation by suitable Setting the frequency with which the switches S1, S2 causes Half-bridge arrangement can be opened and closed.

FIG. 3 shows a block diagram of an operating device on which a preferred embodiment of a circuit arrangement according to the invention is shown. The operating device shown in FIG. 3 is used in particular for setting suitable operating parameters of a first and a second lamp type. A power P1 is assigned to the first lamp type during preheating, while a power P2 is assigned to the second lamp type during preheating. The operating device shown in FIG. 3 has an input E for connecting a mains voltage U _N to a component 10. Component 10 comprises an RF filter, a rectifier and a circuit for limiting the mains current harmonics. The output signal of component 10 is typically a stabilized DC voltage of approximately 400 V, the so-called intermediate circuit voltage, which feeds a half-bridge arrangement 12. The intermediate circuit voltage U _Z is converted by the half-bridge arrangement 12 into a square-wave voltage signal U _R , the frequency of which can be determined by an oscillator 14. The square-wave voltage U _R is passed to a load circuit 16, which comprises a resonance circuit for igniting a lamp LA connected to it. The load circuit 16 also serves to limit the lamp current during normal operation of the lamp LA. The oscillator 14 is controlled by a sequence control 18, by means of which the frequencies and / or duty cycles of the square-wave voltage U _R required for preheating, ignition and normal operation of the lamp LA can be set. Sequence control 18, oscillator 14 and half-bridge arrangement 12 are not necessarily separate circuits, but can form a unit like in a freely oscillating inverter. The voltage U _RM falling across a measuring resistor R _M, not shown _, which is arranged in a half-bridge branch of the half-bridge arrangement, is supplied to a power determination device 20. The power P ist flowing into the load circuit _can be determined from the voltage U _RM and with knowledge of the components of the load circuit 16. The power P _{ist is} compared by a threshold value _switch 22 with a threshold value P _threshold , which is selected such that the power P _ist when the first lamp type _is connected is certainly less than P _threshold during the entire preheating _phase , while the connection of a second lamp type leads to that the threshold value P threshold is _exceeded at least temporarily during the preheating. If the threshold value P _{threshold is} not exceeded, the output of the threshold value _switch remains in the L state, otherwise the output of the threshold value switch 22 at least temporarily changes to the H state. The sequence controller 18 generates a signal only during the preheating phase, as a result of which the electrical switch 24 is closed. As a result, the output signal of the threshold switch 22 is passed to a bistable stage 26 and accepted. The bistable stage 26 provides a signal at its output in the idle state which corresponds to the state L of the threshold switch 22. If this output signal is provided at the output of the bistable stage 26, a switch 28 switches to the position shown in FIG. 3, so that a control variable which corresponds to a power P1 is fed to a control amplifier 30. The power P _is supplied to the control amplifier 30 as the variable to be controlled.

In the event that the threshold switch 22 has a signal at its output provides that corresponds to the H state, causes the bistable stage 26, that the switch 28 switches over and transmits a signal to the control amplifier 30, that is correlated with the power P2. A brief appearance of the H state at the output of the threshold switch 22 is sufficient to to put the switch 28 in the P2 position. Stuck in state P2 the switch 28 until the operating device is switched off.

In the operating device shown in Fig. 3, the lamp LA during of the preheating power regulated. In a simpler embodiment the lamp LA is supplied during preheating Power controlled according to a target power.

With regard to the type of lamp determined, the sequence controller 18 provides suitable signals for operating the lamp not only during the preheating phase, but also for ignition and in normal operation, in particular by varying the amplitude, frequency and duty cycle of the voltage U _R.

As will be apparent to those skilled in the art, instead of using a bistable level other methods can also be used to determine appropriate control of the lamp type used Ensure lamp.

Of course, in an embodiment, not shown, how known from Fig. 1, the preheating of the spiral electrodes by means of preheating inductors be realized.

Claims (9)

Circuit arrangement for operating a fluorescent lamp (LA) comprising a half-bridge arrangement (12), the output signal of which can be fed to a load circuit (LK; 16), a fluorescent lamp (LA) with filament electrodes (W1, W2) being connectable to the load circuit (LK; 16), a preheating device (L21, L22, C _R ) for preheating the filament electrodes (W1, W2) of the fluorescent lamp (LA) and a power determining device (20) for determining a preheating power value, which is a measure of the power that is converted during the preheating in the coil electrodes (W1, W2), characterized in that the power determining device (20) can be used to determine the power flowing into the load circuit (LK; 16) during preheating. Circuit arrangement according to Claim 1, characterized in that the current (I _RM ) flowing in a half-bridge branch can be evaluated by the power determination device (20). Circuit arrangement according to claim 1 or 2, characterized in that it further comprises a sequence control (18) which, depending on the preheating power value (P _ist ), selects one of at least two sequences (P1, P2) for operating the circuit arrangement. Circuit arrangement according to claim 3, characterized in that the at least two processes (P1, P2) for operating the circuit arrangement modes of operation of the circuit arrangement for preheating and / or ignition and / or normal operation of the fluorescent lamp (LA) or measures in the case of defective or not used fluorescent lamp (LA ) include. Circuit arrangement according to claim 1, characterized in that it further comprises a control or regulating device (22, 26, 28, 30), with the power determining device (20) also in normal operation of the fluorescent lamp (LA) the power flowing into the load circuit can be determined , and the control or regulating device (22, 26, 28, 30) is designed to change parameters for the normal operation of the circuit arrangement as a function of this determined power (P _ist ). Circuit arrangement according to claim 5, characterized in that the control and regulating device (22, 26, 28, 30) is designed to compare the determined preheating power value against a desired value (P _threshold ) in order to determine the parameters for normal operation as a function of the result to change this comparison. Circuit arrangement according to one of claims 3 to 6, characterized in that the sequence control (18) comprises a bistable stage (26) in order to select one of two operating modes (P1, P2) of the circuit arrangement as a function of the determined preheating power value (P _ist ). Method for operating a fluorescent lamp (LA), comprising the following steps: a) preheating a fluorescent lamp (LA) while supplying energy from a half-bridge arrangement (12) into a load circuit (16; LK) to which the fluorescent lamp (LA), which has filament electrodes (W1, W2), is connected; b) determining a preheating power value (P _ist ), which is a measure of the power flowing into the load circuit (16; LK) during preheating; c) Depending on the determined preheating power value (P _ist ), selecting one of at least two processes (P1, P2) for operating the circuit arrangement. A method according to claim 8, characterized in that in step b) for determining the preheating power value (P _ist ), the current I _RM flowing through the half-bridge arrangement (12) during preheating is determined.

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