EP2526739B1 - Electronic ballast for operating a hybrid luminaire - Google Patents

Description

Technical area

The present invention relates to an electronic ballast for operating a hybrid lamp with at least one discharge lamp and at least one LED. The electronic ballast comprises a preheating device for preheating the at least one discharge lamp, the preheating device comprising a transformer, a first electronic switch having a working electrode, a reference electrode and a control electrode, a first diode and a first ohmic resistor, wherein the series connection of the primary winding of the transformer in that the distance between the working electrode reference electrode of the first electronic switch, the first diode and the first ohmic resistor is coupled between a supply voltage terminal and a reference potential, and a control device with at least one first output for activating the at least one discharge lamp, a second output for activating the at least one an LED, a third output coupled at least to the control electrode of the first electronic switch and an input for measuring the preheat current during preheating of the m at least one discharge lamp is coupled to the first ohmic resistor.

State of the art

Hybrid lights are usually realized with two separate ballasts, one for operating the at least one discharge lamp and one for operating the at least one LED. Each electronic ballast is connected to the supply network via its own power cable and can be activated separately.

If only one electronic ballast is used, then a control signal is to be supplied to the control device to toggle between discharge lamp operation and LED operation. As a control signal, a signal can be used which is either coupled to a Netzpol or open. Such control devices are usually realized as an ASIC or as a microcontroller. Since most control devices in such a circuit environment already have all the pins occupied for other functionalities, it is necessary to use a more expensive control device with more pins. This is reflected in undesirably high additional costs.

Presentation of the invention

The object of the present invention is therefore to develop an aforementioned electronic ballast such that the conditions for switching back and forth between fluorescent lamp operation and LED operation are created in the most cost-effective manner possible.

This object is achieved by an electronic ballast having the features of claim 1.

In the following embodiments, a control device is used by way of example as a control device, which is usually used in a ballast for discharge lamps. This controls the switches of a half-bridge via two outputs, as is usually used to control the discharge lamp. It also has an output with which a driver device for operating the at least one LED can be activated.

The present invention is based on the recognition that no additional input, ie no additional pin, is required at the control device for the control signal when an input channel of the control device is used twice. Upon careful analysis of the signals at the inputs of such a controller, it has been found that an input is used to measure the preheat current during the preheat phase of the discharge lamp. The present invention is now based in particular on the recognition that in the preheating phase no recognition of a control signal for switching back and forth between discharge lamp operation and LED operation is necessary. This is because at the latest 100 ms, typically even 50 ms, is decided after applying the supply voltage to the electronic ballast, whether discharge lamp operation or LED operation is required. Within this 100 ms, the signal is evaluated at the control input and, depending on switched to LED mode or preheating the coils of the at least one discharge lamp initiated to then ignite the at least one discharge lamp. During preheating, there is no evaluation of the signal at the control input. After completion of the preheating can then be switched by a corresponding signal at the control input again between discharge lamp operation and LED operation. This also applies if LED operation was selected at the first switch-on by a corresponding signal at the control input. Then, when the LEDs are also continuously evaluated, the signal at the control input and by a corresponding signal can be switched to discharge lamp operation including preheating.

Accordingly, an electronic ballast according to the invention further comprises a control input for applying a control signal in order to switch between an operation of the at least one fluorescent lamp and an operation of the at least one LED; a second electronic switch having a working electrode, a reference electrode and a control electrode, wherein the control electrode of the second electronic switch is coupled to the third output of the control device, wherein the reference electrode is coupled to the reference potential, wherein the working electrode is coupled to the control input, and a second diode coupled between the working electrode of the second electronic switch and the input of the control device.

These measures allow an evaluation of the control signal for switching back and forth between fluorescent lamp operation and LED operation at the input of the control device, which usually for measuring the preheating current for preheating the filaments of the at least one discharge lamp is used. As a result, no additional input pin is required on the control device. Thus, a control IC used in prior art ballasts for discharge lamps can now also be used in a hybrid ballast. An additional output for driving a driver for the at least one LED is obtained by other measures, which are not the subject of the present application. The second diode is also used to take over the rectification of the signal applied to the control input, which preferably represents a mains AC voltage. The result is a considerable reduction in manufacturing costs.

Preferably, a voltage divider is coupled between the control input and the input of the control device. This serves to divide the control signal, which is at the level of the mains AC voltage, to an order of magnitude that can be evaluated by a control device, which is usually realized as an IC or microcontroller.

Preferably, a low pass is serially coupled to the input of the control device. This serves to averaging the voltage drop across the first ohmic resistance, which is correlated with the preheating current, so that a reliable evaluation by the control device can take place.

The low-pass filter preferably comprises a second ohmic resistor which is serially coupled between the series connection of the first diode and the first ohmic resistor on the one hand and the input of the control device on the other hand. In this way, the second ohmic resistance can also be used for voltage division of the mains AC voltage at the control input.

The second ohmic resistance is preferably between 0.1 and 10 kΩ, in particular 1 kΩ.

It is particularly advantageous if the second diode is coupled to the coupling point of the second ohmic resistor and the input of the control device. This will do that On the one hand, the signal applied to the control input can be reliably applied to the input of the control device; on the other hand, despite the second electronic switch being switched on, a reliable evaluation of the voltage drop across the first ohmic resistor, which is correlated with the preheating current, can be made at the input of the control device.

Preferably, the low pass further comprises the parallel connection of a third ohmic resistor and a capacitor. In this case, the low pass is preferably designed such that it has a cutoff frequency between 1 and 100 kHz, in particular 10 kHz. Thus, the cutoff frequency is well below the preheat frequency, which is usually between 100 kHz and 130 kHz. To determine the heating level, the mean value of the preheating current is therefore evaluated; the evaluation of the control signal, however, takes place via a peak value determination.

According to a preferred embodiment, a first inverter is coupled between the third output of the control device and the control electrode of the first electronic switch. This serves to increase the level at the third output of the control device, which is usually about 3 V, to a value which is sufficient to drive the control electrode of the first electronic switch. This usually requires 15V.

For the same reason, a second inverter is preferably coupled between the third output of the control device and the control electrode of the second electronic switch. According to a preferred embodiment, the electronic ballast further comprises a fourth diode which is coupled in anti-parallel to the series connection of the first diode and the first ohmic resistor. This diode serves as a freewheeling diode for the negative current components through the first electronic switch. This ensures that only positive current components are evaluated during the preheating of the control device and thus a meaningful averaging is only possible.

As already mentioned, the control signal preferably represents a network signal.

Further preferred embodiments emerge from the subclaims.

Short description of the drawing (s)

Fig. 1

eine schematische Darstellung eines ersten Ausführungsbeispiels eines erfindungsgemäßen elektronischen Vorschaltgeräts;

Fig. 2

eine kurze Zusammenfassung zur Funktionsweise des in Fig. 1 dargestellten Ausführungsbeispiels; und

Fig. 3

ein zweites Ausführungsbeispiel eines erfindungsgemäßen elektronischen Vorschaltgeräts.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Show it:

Fig. 1

a schematic representation of a first embodiment of an electronic ballast according to the invention;

Fig. 2

a short summary of how the in Fig. 1 illustrated embodiment; and

Fig. 3

A second embodiment of an electronic ballast according to the invention.

Preferred embodiment of the invention

In the figures, the same reference numerals are used for identical and equivalent components. These are introduced only once for the sake of clarity.

Fig. 1 shows a schematic representation of a first embodiment of an electronic ballast according to the invention. This comprises a control device 10, which comprises two outputs A1a, Alb, in order to control the switches of an inverter whose load circuit is coupled to at least one discharge lamp FL. It also comprises an output A2, which is designed to drive a driver module for operating at least one LED. For preheating the coils, not shown, of the at least one discharge lamp FL, the series connection of a transformer Tr, which has a primary winding L1A and a secondary winding L1B, an electronic switch M1, a diode D1 and an ohmic resistor R1 is provided between a supply voltage V _c and a reference potential is coupled.

The coils of the at least one discharge lamp FL are coupled in a known manner to the secondary winding L1B of the transformer Tr. For driving the switch M1, which is preferably realized as a transistor having a control electrode, working electrode and reference electrode, an output A3 of the control device 10 is provided, wherein in the present case an inverter is coupled between the output A3 and the switch M1.

When the switch M1 is turned on, a current flows from the power supply V _c , through the primary winding L1A of the transformer Tr, the switch M1, the diode D1 and the ohmic resistor R1 proportional to the preheating current through the filaments of the at least one discharge lamp FL is. The voltage drop across the diode D1 and the ohmic resistor R1 is coupled via a low-pass filter TP to the input E1 of the control device 10 in order to determine the preheating current and regulate if necessary. A diode D3, which is connected in antiparallel to the series circuit of the diode D1 and the ohmic resistor R1, serves as a freewheeling diode for negative current components in the preheating, to allow meaningful averaging. The controller 10 may of course have a variety of other inputs and outputs. Also, the output A2 can be used twice by appropriate, but not relevant measures here.

The circuit arrangement described so far is known with the exception of the use of the output A2 of the control device 10. The assembly indicated at 12 now includes the components necessary to enable switching between LED operation and fluorescent lamp operation by evaluating the control signal at input E1 of controller 10 outside the preheat phase of the filaments of the at least one discharge lamp.

The control signal applied to the control input St can in particular represent a network signal. It is connected via a resistor R8 to the working electrode of a second electronic switch M4 whose reference electrode is grounded. The control electrode of the second electronic switch M4, like the control electrode of the first electronic switch M1, is coupled to the output A3 of the control device 10. Between the output A3 of the control device 10 and the control electrode of the switch M4, as well as in the electronic switch M1, an inverter is coupled.

The working electrode of the second electronic switch M4 is coupled to the reference electrode of the first electronic switch M1 via a diode D2.

To explain the operation of the in Fig. 1 schematically illustrated electronic ballast is based on the comments in Fig. 2 Reference: During preheating, the output A3 of the control device 10 is at "logic 0", ie at ground. As a result, both the switch M1 and the switch M4 are turned on. By turning on the switch M4, the control signal at the control input St is short-circuited, that is, at the input E1 of the control device 10, only the falling over the series circuit of the diode D1 and the ohmic resistor R1 signal is evaluated, the preheating by the helices of the at least one discharge lamp FL is proportional. A discharge of this signal via the switch M4 to ground is prevented by the diode D2.

After preheating, the output A3 of the control device 10 is at high potential, that is logic "1". As a result, both the switch M1 and the switch M4 is not turned on. Accordingly, no preheating current flows more and at the input E1 of the control device 10, a signal can be evaluated, which is proportional to the control signal at the control input St of the electronic ballast.

Fig. 3 shows a schematic representation of a second embodiment of an electronic ballast according to the invention. This essentially corresponds to the one in Fig. 1 schematically illustrated embodiment, but some of the in Fig. 1 only schematically illustrated assemblies are shown in more detail. So becomes a first Inverter, which is coupled between the control electrode of the switch M1 and the output A3 of the control device 10, formed by an assembly comprising the ohmic resistors R2, R3, R4 and a further electronic switch M2, the working electrode via the resistor R3 with a Voltage supply V _{1 is} coupled.

In a corresponding manner, the second inverter, coupled between the output A3 and the control electrode of the switch M4, comprises ohmic resistors R5 and R6 and a further electronic switch M3. No additional ohmic resistance then needs to be provided between the working electrode of the switch M3 and the control electrode of the switch M4, if the resistance R _{Dson of} the switch M3 is large enough, for example of the order of 10 Ω.

Between the reference electrode of the electronic switch M1 and the input E1 of the control device 10, a low-pass filter is connected, which comprises the parallel connection of an ohmic resistor R10 and a capacitor C1. A voltage divider is formed by the series connection of the ohmic resistor R8 with a combination comprising a parallel connection of the resistor R10 to a series connection of the resistors R9 and R1.

Claims (12)

1. Electronic ballast for operating a hybrid luminaire comprising at least one discharge lamp (FL) and at least one LED, comprising:

   - a preheating apparatus for preheating the at least one discharge lamp (FL), wherein the preheating apparatus comprises a transformer (Tr), a first electronic switch (M1) with a working electrode, a reference electrode and a control electrode, a first diode (D1) and a first nonreactive resistor (R1), wherein the series circuit comprising the primary winding (L1A) of the transformer (Tr), the working electrode-reference electrode path of the first electronic switch (M1), the first diode (D1) and the first nonreactive resistor (R1) is coupled between a supply voltage connection (V_c) and a reference potential; and

   - a control apparatus (10) comprising at least one first output (A1a, A1b) for driving the at least one discharge lamp (FL); a second output (A2) for driving the at least one LED; a third output (A3), which is coupled at least to the control electrode of the first electronic switch (M1); and an input (E1), which is coupled to the first nonreactive resistor (R1) for measuring the preheating current during the preheating of the at least one discharge lamp (FL);
   characterized in that the electronic ballast further comprises:

   - a control input (St) for applying a control signal for switching over between operation of the at least one discharge lamp and operation of the at least one LED;

   - a second electronic switch (M4) comprising a working electrode, a reference electrode and a control electrode, wherein the control electrode of the second electronic switch (M4) is coupled with the third output (A3) of the control apparatus (10), wherein the reference electrode is coupled to the reference potential, wherein the working electrode is coupled to the control input (St); and

   - a second diode (D2), which is coupled between the working electrode of the second electronic switch (M4) and the input (E1) of the control apparatus (10).
2. Electronic ballast according to Claim 1, characterized in that a voltage divider (R8, R10, R9, R1) is coupled between the control input (St) and the input of the control apparatus (10).
3. Electronic ballast according to either of Claims 1 and 2, characterized in that a low-pass filter (TP) is coupled in series with the input of the control apparatus (10).
4. Electronic ballast according to Claim 3, characterized in that the low-pass filter (TP) comprises a second nonreactive resistor (R9), which is coupled in series between the series circuit comprising the first diode (D1) and the first nonreactive resistor (R1), on one side, and the input (E1) of the control apparatus (10), on the other side.
5. Electronic ballast according to Claim 4, characterized in that the second nonreactive resistor (R9) has a resistance of between 0.1 and 10 kΩ, in particular 1 kΩ.
6. Electronic ballast according to either of Claims 4 and 5, characterized in that the second diode (D2) is coupled to the coupling point between the second nonreactive resistor (R9) and the input (E1) of the control apparatus (10).
7. Electronic ballast according to one of Claims 3 to 6, characterized in that the low-pass filter (TP) furthermore comprises the parallel circuit comprising a third nonreactive resistor (R10) and a capacitor (C1).
8. Electronic ballast according to one of Claims 3 to 7, characterized in that the low-pass filter (TP) has a limit frequency of between 1 and 100 kHz, in particular 10 kHz.
9. Electronic ballast according to one of the preceding claims, characterized in that a first inverter (R4, M2, R3, R2) is coupled between the third output (A3) of the control apparatus (10) and the control electrode of the first electronic switch (M1).
10. Electronic ballast according to one of the preceding claims, characterized in that a second inverter (R6, M3, R5) is coupled between the third output (A3) of the control apparatus (10) and the control electrode of the second electronic switch (M4).
11. Electronic ballast according to one of the preceding claims, characterized in that the electronic ballast furthermore comprises a third diode (D3), which is coupled back-to-back in parallel with the series circuit comprising the first diode (D1) and the first nonreactive resistor (R1).
12. Electronic ballast according to one of the preceding claims, characterized in that the control signal represents a mains signal.

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