GB2537692A

GB2537692A - Detection circuit for detecting a supply voltage

Info

Publication number: GB2537692A
Application number: GB1507956.9A
Authority: GB
Inventors: Frankland James; Wilson Ian; John Wood Anthony
Original assignee: Tridonic GmbH and Co KG
Current assignee: Tridonic GmbH and Co KG
Priority date: 2015-04-23
Filing date: 2015-04-23
Publication date: 2016-10-26
Anticipated expiration: 2035-04-23
Also published as: GB201507956D0; GB2537692B

Abstract

A ballast having a detection circuit for detecting characteristics of at least two different voltages supplied to independent input terminals of the ballast, wherein the detection circuit comprises a rectifying unit 1 that comprises a first input terminal for applying a first externally supplied voltage (VAC1) and a second externally supplied voltage (VAC2), wherein the first voltage (VAC1) is a switched AC and the second voltage (VAC2) is an AC voltage. The detection circuit further comprises an evaluating unit (2), which is configured to provide a detection signal that indicates whether the first voltage (VAC1) is present; and whether the second voltage (VAC2) is present or replaced by a DC voltage. The rectifying unit 1 may comprise a single full wave rectifier for rectifying both the first voltage (VAC1) and the second voltage (VAC2). The first voltage may be fully rectified by means of the full wave rectifying unit 12 and the second voltage may be half rectified by a sub section of the full wave rectifier 11.

Description

Detection circuit for detecting a supply voltage

FIELD OF THE INVENTION

The invention relates to a detection circuit for detecting one or more characteristics of a supply voltage for a ballast of a lighting means. The invention further relates to a ballast for emergency lighting means.

The invention preferably finds application in the area of emergency lighting systems, wherein the state of a supply voltage has to be evaluated in order to decide whether an emergency case is present or not. The lighting means are controlled by a control unit of the ballast.

BACKGROUND OF THE INVENTION ^ ..

* * * *** * * * O. * * * 0000 * * * In case of an emergency it is necessary to illuminate the emergency exits in buildings. An emergency might be a fire alert or a mains voltage loss or something similar. There is a security requirement for lighting systems in buildings forcing a lighting means to illuminate in case of an emergency regardless the switching element is activated or deactivated. Thus, it is necessary to detect, whether a voltage supply is present or not.

Nowadays ballasts for lighting means therefore comprise two independent detecting circuits in case two different supplied mains voltages are to be monitored, wherein the first mains voltage is a switched AC voltage, wherein the switching can be done by an interface such as a switch, a dimmer or etc. The second AC voltage may be a regular AC voltage the state of which is monitored by the ballast in order to decide on an emergency case, e.g. when the AC voltage is off or replaced by a DC voltage.

In such applications both of these mains voltages are fed independently to independent terminals of a ballast for lighting means, which processes the switching of the switched AC voltage as control commands (e.g. for setting an operation parameter such as e.g. a dimming value).

In such a case, a first detecting circuit is used to detect the state of the switched AC voltage. In case the switching element, such as a wall switch in a room, is activated, a supply voltage is applied to the lighting means in order to activate the lighting means.

Additionally, a second detecting circuit is needed to monitor the state of the regular AC voltage in order to decide on an emergency state, in which the lighting means has to be activated regardless the state of the first voltage. ^ 1,0

* * * 04.8 * * * 00 * * . *4100 * * * * * Thus, two independent detecting circuits are required, which duplicates components and leads to greater printed circuit board areas used and thus to higher manufacturing 25 costs.

It is an objective to provide a detection circuit which reduces components and which is manufactured in a cost-efficient manner. The detection circuit should be of 30 reduced size.

SUMMARY OF THE INVENTION

The above-identified objective is solved with the features of the independent patent claims. Advantageous embodiments 5 are solved with the features of the respective dependent patent claims.

The objective is especially solved by a ballast having a detection circuit for detecting characteristics of at least two different voltages supplied to independent input terminals of the ballast, wherein the detection circuit comprises a rectifying unit. The rectifying unit comprises a first input terminal for applying a first externally supplied voltage, wherein the first voltage is a switched AC voltage. The rectifying unit comprises a second input terminal for applying a second externally supplied voltage, wherein the second voltage is an AC voltage. The detection circuit further comprises an evaluating unit, which is configured to provide a detection signal, wherein the detection signal indicates whether the first voltage * ** is switched to the ballast; and whether the second voltage * * * * is applied to the ballast or the second voltage is *** * * * replaced by a DC voltage.

* * . 0000 * 25 The inventive concept allows voltage detection with a single detection circuit, which fulfills the security requirements for emergency lighting means in buildings. Thus, no additional detection circuit is required and the number of components for such voltage detection is * * * 30 reduced. Using a rectifying unit and an evaluation unit according to the inventive concept, the detection circuit obtains the direct indication whether the first voltage or the second AC voltage is present or absent or whether the second voltage has been replaced by a DC voltage. Thus, * only one detection circuit is necessary to operate the lighting means in case of an emergency.

The first voltage and the second voltage are alternating current voltages, hereinafter referred to as AC voltages. To detect in a subsequent control unit, whether the first voltage or the second voltage is present, a direct current detection signal needs to be generated.

Preferably, the frequency of the switched AC voltage is equal to the frequency of the second AC voltage.

In a preferred embodiment, the rectifying unit comprises a single full-wave rectifier for rectifying the first voltage and for rectifying the second voltage. Thus, the same components of a rectifying unit can be used to rectify both the switched AC voltage and the second AC voltage. Thus, the number cf components in the detection circuit is reduced and the manufacturing costs are decreased.

* . . 00.0 * In a preferred embodiment, the switched AC voltage is fully rectified by means of the full-wave rectifying unit. Thus, the frequency of the rectified switched AC voltage at the output of the rectifying unit is as double as high as the frequency of the switched AC voltage.

In a preferred embodiment, the second AC voltage is half-rectified by means of the full-wave rectifying unit. This is achieved by directly supplying the second AC voltage to one of the two half-wave rectifiers of the full-wave rectifying unit. Thus, the frequency of the rectified second AC voltage at the output of the rectifying unit is the same as the frequency of the second AC voltage. * 00

* * * 10060 * * * * * O0.41 * O000 ^ * * * Additionally or alternatively, the second AC voltage has been replaced by an emergency DC voltage in case of an emergency. Thus, the second input terminal of the detection unit obtains a DC voltage instead of the second AC voltage. The DC voltage will pass the rectifying unit without any further signal characteristic changes, thus the detection signal indicates the presence of the DC voltage. The evaluation unit evaluates the missing frequency or the higher/lower effective voltage value to 10 subsequent units in order to switch on the lighting means.

Using the full-wave rectifying unit to rectify the switched AC voltage and the second AC voltage, the same diodes can be used for both the first voltage and the second voltage. This leads to a reduction of components in the detection circuit and taus leads to less manufacturing costs. * * *

* * * ** * * * * * * Ike * * * 0000 * * * * The evaluating unit is used to prepare the rectified signals for evaluation the presence /absence of the switched AC voltage and/or the second AC voltage. If the frequency of the switched AC voltage is equal to the frequency of the second AC voltage, the absence of the second AC voltage is easily detected by observing the frequencies of the rectified voltages. As long as a frequency value is evaluated which is as double as high as the frequency value of the switched AC voltage frequency value, the second AC voltage is applied to the second input terminal. Thus, either the mains voltage is still available in the lighting system or no emergency situation is occurred. If a frequency value of the rectified voltage is evaluated which is equal to the frequency value of the switched AC voltage frequency value, the second AC voltage is not applied to the second input terminal. Thus, the mains voltage is not available to the lighting system and the lighting means should be permanently switched on.

Alternatively, if a frequency value of the rectified voltage is evaluated which is zero Hertz, the second AC voltage has been replaced by an emergency DC voltage, which is applied to the second input terminal. Thus, the mains voltage is not available to the lighting system and the lighting means should be permanently switched on. 10 Alternatively, a metering unit is used to determine whether the switched AC voltage or the second AC voltage is present. The metering unit evaluates a mean rectified voltage or a different height of the voltage value or a different frequency of the supplied voltages. In an alternative embodiment, the frequency of the switched AC voltage is different to the frequency of the second voltage and the difference in the frequencies is evaluated by the metering unit.

* * In a preferred embodiment, the switched AC voltage is the * * * output signal of a switching element. For instance, a ** * * * * switching element might be a wall switch or an alternative control means to activate or deactivate the lighting * * * * * * ** * * * * * * 25 means. Then, the switched AC voltage is switched to the * first input terminal. Thus, the switched AC voltage ** ** represents the user's behavior and his intention to switch-on/switch-off a specific lighting means. In case the switched AC voltage is switched-on by the switching element and the second AC voltage is present at the detection circuit, the detection circuit indicates that the switched AC voltage and the second AC voltage are present and the lighting means should be activated due to the user's choice. *

In a preferred embodiment, the second AC voltage is replaced by a DC voltage in case of an emergency or a mains voltage failure. The DC voltage is directly provided to the detection circuit in order to indicate whether an s emergency is present and the lighting means needs to be switched-on regardless the state of the switched AC voltage. * * * *

* * * * * * a 41.0 * * * * * * * * *** Oeme The second AC voltage is preferably a permanent mains voltage and directly provided to the detection circuit in order to indicate whether the mains voltage is present in the lighting system or whether a mains voltage break-down or mains voltage failure occurred. The permanent mains voltage is directly connected to the second input terminal of the detection circuit without further additional components. In case the second AC voltage is detected, the lighting means is switched in dependence on the state of the switched AC voltage. Such a scenario represents the user's choice of the switching state of the lighting means. In contrast, in case the second AC voltage is absent or has been replaced by a DC voltage, the lighting means is switched-on independent from the state of the switched AC voltage. Thus, the user's choice for switching the lighting means is overruled in the absence of the second AC voltage or on detection of a DC voltage at the second input terminal.

This overruling is the fulfillment of the security requirement for lighting means in a building in case the mains voltage breaks down or in case of an emergency. Thus, the detection circuit indicates the presence or absence of the second AC voltage, wherein in absence of the second AC voltage, the lighting means is permanently switched-on independent on the state of the switched AC voltage. In case the second AC voltage is present, a ballast switched-on the lighting means in dependence on the presence of the switched AC voltage.

In contrast in case the second AC voltage is absent, the ballast permanently switches-on the lighting means. To switch-on the lighting means on absence of the mains voltage, the ballast is equipped as emergency lighting ballast. Thus, the ballast comprises an auxiliary voltage supply means, such as an energy storage means, for instance a battery, to provide voltage to the lighting means in case the mains voltage is absent.

In a preferred embodiment an isolating unit is arranged between the rectifying unit and the evaluating unit for galvanically isolating the first input terminal and the second input terminal from the output terminal. The isolating unit might comprise an optocoupler. The optocoupler, also referred to as photocoupler, or optical isolator, is a component that transfers electrical signals between two isolated circuits by using light. Optoisolators prevent high voltages from affecting the system receiving the signal. A common type of optocoupler consists of an LED and a phototransistor in the same opaque package. Other types of source-sensor combinations include LED-photodiode, LED-LASER, and lamp-photoresistor pairs. The opto-coupler transfers the rectified voltage from the rectifying unit to the evaluating unit.

Alternatively, the isolating unit is a pulse transformer.

Both, the opto-coupler and the pulse transformer galvanically separate the rectifying unit and the evaluating unit. This is a further security requirement * * * * * * ** * * * * * * * * * ** * * * * * * * * **** for lighting means, operating with supply voltages above a certain threshold value. Drawbacks of such isolating units are the high costs and the complex installation requirements. According to the invention, the detection circuit is a single detection circuit for detecting the presence of a first voltage and a second voltage. Thus, only one isolating unit is needed in order to galvanically separate the first input terminal and the second input terminal from the output terminal. Thus, an expensive 10 second isolating unit for the second voltage can be avoided and the security requirement is still fulfilled.

In a preferred embodiment a noise reduction unit is arranged between the rectifying unit and the evaluating unit. Such a noise reduction unit increases the accuracy of the rectified voltage from the rectifying unit. Thus, the indication of the presence of the first voltage or the second voltage is provided in a more precise manner. * **

* . . *** * * * * ** * * * **** * *** * **** **** In a preferred embodiment, a threshold detection unit is arranged between the rectifying unit and the evaluating unit. The threshold detection unit is used to reduce the analog nature of the rectified voltage. Thus, a digitized rectified signal is applied to the evaluating unit, which is handled easier.

In a preferred embodiment, the detection signal is pulled-up by a pull-up resistance element. The rectified signal is supplied to the evaluating unit in order to indicate the presence/absence of the switched AC voltage or the second AC voltage or a DC voltage. The evaluating unit can be combined with a microcontroller unit or an Application Specific Integrated Circuit, short ASIC. The microcontroller or ASIC inputs need a defined state of the signals provided at their input terminals. Thus, the pull-up resistance elements are used to obtain logical levels of the rectified signals. * .. * * *

O041 * * * * * 0O * * * 0.100 * * * * * 0204.

In a preferred embodiment the switched AC voltage and the second AC voltage comprise a common third terminal, wherein the common terminal incorporates a resistance element. The switched AC voltage and the second AC voltage might be voltages with values above 40 Volts, preferably above 100 Volts. Such a high voltage value consumes power at all resistive elements in the detection circuit, wherein the consumed power is at least partly converted into heat. Thus, it is necessary to provide a detection circuit which is designed in that the converted heat does not destroy an element or a component of the detection circuit. To avoid such destructions, the detection circuit needs to have signal lines and components with profiles or sizes that are able to consume such high voltages. Thus, the detection circuit needs to have a minimum size. If the first voltage and the second voltage would have been detected in separate detection circuits, the appropriate printed circuit boards would be very large. Using the resistance element at the common terminal leads to a reduction of size, since the switched voltage and the second AC voltage use the same resistance element and thus the power is dissipated. Thus, the number of components and the number of size of the detection circuit can be reduced.

The above-identified objective is further solved by a ballast for a lighting means, preferably an emergency lighting means which comprises the above described detection circuit. The ballast further comprises a control unit which is configured to control the lighting means, wherein the control unit obtains the detection signal of the detecting circuit as an input signal.

By applying the detection signal to the control unit, the control unit is able to evaluate whether the switched AC voltage or the second AC voltage or a DC voltage are present or absent. Thus, a control of the lighting means is possible in dependence on the presence of the switched AC voltage and/or the second AC voltage and/or a DC voltage.

In a preferred embodiment, the lighting means is permanently switched on in case the second AC voltage is absent or a DC voltage is supplied to the ballast.

In a preferred embodiment, the lighting means is switched on in dependence on the state of the switched AC voltage and a present second AC voltage.

In a preferred embodiment, the first voltage is switched by means of a switching element.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following exemplary embodiments of the invention are described with reference to drawings. Those exemplary embodiments do not limit the scope of the invention. The same reference signs in different drawings indicate the same elements or at least the same functions unless otherwise stated. *

* * * 41410 * * * * * NIO * * * iliO0111 * * * * 000O Fig. 1 shows a first detection circuit according to the

prior art,

Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 * ** * * * *** * * * * ** * * * Fig. 9 **** * *** * shows a second detection circuit according to the prior art, shows a first exemplary embodiment of a detection circuit according to the invention, shows a second exemplary embodiment of a detection circuit according to the invention, shows a third exemplary embodiment of a detection circuit according to the invention, shows a fourth exemplary embodiment of a detection circuit according to the invention, shows simplified voltage diagrams of a detection circuit according to the invention in a non-emergency state, shows simplified voltage diagrams of a detection circuit according to the invention in an emergency state if second AC voltage is absent, shows simplified voltage diagrams of a detection circuit according to the invention in an emergency state if second AC voltage is replaced by DC voltage. *

* ** *

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 shows a first detection circuit according to the prior art. The detection circuit comprises a half-wave rectifier 11 and an evaluation unit 2. The half-wave rectifier 11 is used to rectify a single-phase AC voltage VAC1. In the half-wave rectification 11 even the positive or the negative half of the AC wave is passed while the other half is blocked. Because only one half of the input wave form reaches the output of the half-wave rectifier 11, the means voltage is reduced. The half-wave rectifier 11 uses a first rectifying diode DA and a second rectifying diode DB. A dissipation resistance RA is used to provide the first input voltage VAC1 to the diodes DA and DB. A load resistance RB is further used to provide the to rectified first voltage VDc1 to the evaluating unit 2. An output terminal at the evaluating unit 2 provides a detection signal Vdetect which indicates the presence of the first supply voltage VACl* In Fig. 2, a second detection circuit according to the prior art is shown. Herein the detection circuit comprises a full-wave rectifier 12 which comprises four rectifying diodes DA, DB, Dc and DD. The full-wave rectifier 12 is used to rectify a single-phase AC voltage VAC2. The full-wave rectifier 12 converts the voltage VAc2 to a constant * * * polarity, e.g. a positive or a negative polarity. The * * * * * * * * full-wave rectification 12 converts both polarities of the * * input wave form to a positive direct current and yields a * * * * * * higher means voltage compared to the half-wave rectifier * * * * * 25 according to Fig. 1. * * * *

** * * * ** * * To detect the state of two separate voltages, it is usual to use two separate detector circuits, for instance the detector circuits according to Fig. 1 or Fig. 2. In the field of ballasts for lighting means two separate detectors are used wherein the first detector is built according to Fig. 1 and the second detector circuit is built according to Fig. 2.

Referring to Fig. 3 a first exemplary embodiment of the invention is provided. Therein two detection circuits are combined so that the state of the switched AC voltage VAC1 or the presence of the second voltage VAC2 is indicated to subsequent circuit parts, e.g. a ballast for a lighting means. A combined rectified voltage V. is provided to the evaluating unit 2 in order to obtain the detecting signal Vdetect * * * * ** * . * Thus, in Fig. 3 the rectifying unit 1 comprises a first input terminal to apply a first externally supplied switched AC voltage Vim and a second input terminal to apply a second externally supplied AC voltage VAC2. A common terminal connected to a reference potential is also shown in Fig. 3. The output of the rectifying unit 1 is provided to an evaluating unit 2. The evaluating unit 2 comprises an output terminal to provide the detection signal Vdetect that indicates the state of the switched AC voltage VAci or the presence/absence of the second AC voltage VAo2 or a replacement of the second AC voltage VAC2 by a DC voltage.

The switched AC voltage VAci. provides a voltage in dependence on an activation or a deactivation of a switching element (not shown) such as a manual wall switch or a control switch to activate or deactivate a lighting means in a room on a user's choice. The second AC voltage VAC2 is provided to the detection circuit in order to monitor the state of the mains supply voltage independent of the user's behavior. The permanent mains voltage VAC2 is connected directly to the detection circuit without any devices in between. So, the detection circuit obtains direct information whether the mains voltage is available or a voltage break-down or an emergency occurred.

** * * * ** * * * * * . * * * * * * ** * . * *I*** * V * * * *** * * * * * * Furthermore, in case of an emergency, the second voltage VAC2 might be replaced by a DC voltage in order to indicate, that an emergency has occurred and the lighting means should illuminate regardless the state of the switched AC voltage VACl* According to the inventive concept shown in Fig. 3 it is now possible to combine two independent detection circuits into one single detection circuit thereby reducing the number of components and thereby reducing circuit boards space and manufacturing costs. The detection circuit combines the first rectified voltage V001 and the second rectified voltage V02 to a combined rectified voltage V,..

In case of non-emergency, the input terminal for the second AC voltage VAC2 will be supplied with an AC voltage. In case an external switching element (not shown) switches-on the switched mains voltage VAcir the respective first input terminal of the rectifying unit 1 is applied with the switched AC voltage VAc1. In case the external switching element (not shown) switches-off the switched AC voltage VAC1r the respective first input terminal of the rectifying unit 1 is not applied with the switched AC voltage Vmn. The switched AC voltage VAci can be a switched live line in a lighting system, wherein the switched AC voltage \limn is the mains voltage, switched on the user's choice.

Thus, using the detection circuit in a lighting means application, the lighting means is switchable in dependence of the switched AC voltage Vic in case the second voltage VAC2 is present. * **

* * ** * * * * * ** * ** * **^*** * *** * * **** el* * In case of an emergency state, the second AC voltage VAC2 will not be applied to the second input terminal of the detection circuit. In such an emergency case, the lighting means has to be switched-on/activated regardless of the state of the switched AC voltage VIvn in order to provide an emergency illumination to allow the evacuation of the building. To allow the emergency illumination, the ballast might comprise an auxiliary voltage supply, such as an energy storage means, for instance a battery, in order to 10 provide emergency voltage to the lighting means.

Alternatively, in case of an emergency state, the second AC voltage VAC2 will be replaced by a DC voltage. In such an emergency case, the lighting means has to be switched-on/activated regardless of the state of the switched AC voltage VAC]. in order to provide an emergency illumination to allow the evacuation of the building. To allow the emergency illumination, the ballast might use the DC voltage to provide emergency voltage to the lighting means.

To provide such functionality for lighting means, the detection circuit needs to detect the state of both the switched AC voltage VA01 and the second AC voltage VAC2 or the presence of a DC voltage, which substitutes the second AC voltage VAC2 in case of an emergency. The switched AC voltage VA01 is applied to a half-wave rectifier 11 while the second AC voltage VAC2 is applied to a full-wave rectifier 12 of the rectifying unit 1. Since the full-wave rectifier 12 obtains two half-wave rectifiers 11, the same components for the half-wave rectification of the switched mains voltage VAci can be used. * **

* * * *** . * The combined signal Vcon, of the rectifier unit 1 is then provided to the evaluating circuit 2. The frequency of the combined signal Vcom can be evaluated in the evaluating unit 2 or in the subsequent control unit 6. The frequencies of the switched AC voltage VAC1 and the second AC voltage VAc2 are identical. In case the frequency of the output terminal detection signal Vdetect is as double as high as the frequency of the switched AC voltage VAC1 or the second AC voltage VAC2 -assuming that the frequency values of the switched AC voltage VAC1 and the second AC voltage VAC2 are identical -, the full-wave rectifier 12 in the rectifier unit 1 has been used and thus, the second AC voltage VAC2 is applied to the second input terminal of the rectifier unit 1. In case the frequency of the output terminal detection signal Vaetect is as high as the frequency of the switched AC voltage VAci or the second AC voltage VAC2 -still assuming that the frequency values of the switched AC voltage VAci and the second AC voltage VAC2 are identical -, the half-wave rectifier 11 in the rectifier unit 1 has been used and thus, the second AC voltage VAC2 is not applied to the rectifier unit 1. Thus, the evaluating unit provides a detection signal Vdetect which indicates whether the switched AC voltage VAC1 is switched to the ballast; and whether the second AC voltage VAC2 is applied to the ballast or the second AC voltage VAC2 * ** * * * **** * *** * **** is replaced/substituted by a DC voltage. The detection of the frequency value of the detection signal Vdetect can also be obtained in the control unit 6 by means of a counting element. Preferably, the evaluating unit 2 obtains means * 30 for detecting the frequency of the combined rectified voltage Vam and provides the respective detection signal Vdetect to the control unit 6. **** * *** *

Alternatively or additionally, the evaluating unit 2 comprises means to detect a mean voltage value, preferably an effective voltage value or a root-mean square voltage value or a peak voltage value etc. from the combined rectified voltage Vcom to indicate the state of the switched AC voltage VAcl or the second AC voltage VAC2 or a DC voltage.

Alternatively or additionally, the evaluating unit 2 comprises means to detect the slew rate of the combined rectified voltage Vcom in order to detect the presence of the substituting DC voltage.

Alternatively or additionally, the evaluating unit 2 comprises means to detect the number of defined threshold values, which the combined rectified voltage Vcom exceeds or undershoots in a predefined time period.

Alternatively or additionally, the evaluating unit 2 * * * . 20 comprises means to detect the frequency of the combined rectified voltage Vcom -assuming that the frequency values of the switched AC voltage 'Sipa1 and the second AC voltage * * . . ** * * * 00 VAC2 are different -in order to detect the state of the * * * * * * * * switched AC voltage VAn, the second AC voltage VAC2 or the * * * presence of the substituting DC voltage. 0O0O *000

In Fig. 4, a second exemplary embodiment of the invention is shown. In-between the rectifying unit 1 and the evaluating unit 2 an isolating unit 3 is arranged. The isolating unit 3 incorporates an opto-isolator. The optoisolator is necessary to galvanically separate the switched AC voltage VAC' and the second AC voltage VAc2 from the detection signal Vdetect. Such a separation is necessary in case the voltage values for the switched AC voltage VAC1 and the second AC voltage VAC2 excess a certain amount of voltage values. In case high voltage values are used, such a separation of the potentials is necessary to fulfill security requirements. * O0

* * * *00 * * * * * * * * . * * * * * * * * * Additionally, a noise reduction filter 4 is used to obtain a higher accuracy of the detection signal. Additionally, a threshold detection unit 5 is arranged in between the rectifying unit 1 and the evaluating unit 2 in order to obtain a proper detection signal and to convert the rectified voltage Vcorn to a digital signal.

In Fig. 5, a first detailed exemplary of the rectifying unit 1 according to the invention is shown. Therein the switched AC voltage VAC1 is applied to a first input terminal of the rectifying unit 1. A second AC voltage VAC2 is applied to a second input terminal of the rectifying unit 1. The rectifying unit 1 further comprises resistance elements RA1, RA2, Ft, on the input side in order to dissipate the input power. The common resistance element RC is used to dissipate the power of the switched AC voltage VAC1 and the second AC voltage VAC2.

A full-wave rectifier 12 is used to rectify the second AC voltage VAC2. The full-wave rectifier 12 can be obtained by two diodes DA, DH and a center tapped transformer (not shown) or four rectifying diodes DA, DH, Dc and DD and a bridge configuration, such as a so called Graetz bridge rectifier as shown in Fig. 5. Single semiconductor diodes, double diodes with common cathode or common anode and four-diode bridges manufactured as single components might be used to obtain the rectifying diodes DA, Da, Dc and DD.

The full-wave rectifier 12 comprises two half-wave rectifier 11. To reduce components, the invention suggests to combine the rectifier of the switched AC voltage VAc2 and the second AC voltage VAC2. Thus, the switched AC voltage VAC1 is applied to one of the half-wave rectifier 11 of the full-wave rectifier 12 of the single rectifying unit.

Thus, the diodes DA, DH, Dc and DD provide a full-wave rectifier 12 for the second AC voltage VAC2 and the diodes Dc and DD thereof provide an additional half-wave rectifier 11 for the switched AC voltage VAci. The combined rectified voltage Vcom is provided to the evaluating unit 2 in order to evaluate the frequency, a voltage value, or a certain other characteristics of the rectified voltage Vcom. In case the second AC voltage VAC2 is present, the frequency of the rectified voltage Vcon, is as double as high as the frequency of the second AC voltage VAC2. In case the second AC voltage VAC2 is absent, the frequency of the rectified voltage Vccm is as high as the frequency of * * * * * . * * * * the second AC voltage VAC2. *

* * * The evaluating unit 2 uses the combined rectified voltage * * * ** * * V"," to indicate whether the switched AC voltage VAC2 is * .* * switched to the ballast and whether the second AC voltage * * * * * * * * * * * * * Alternatively, a voltage value, such as a mean voltage value or peak voltage value or threshold value, is detected in the evaluating unit 2 or the control unit 6 in order to detect whether the first voltage VAci or the second voltage VAC2 are present/absent.

VAC2 or a DC voltage as replacement of the second voltage VAC2 are applied to the ballast.

In Fig. 6 a fourth exemplary embodiment of a detecting circuit is shown. Therein the isolating unit 3, the noise reduction unit 4 and the evaluation unit 2 are shown in greater details. The isolating unit 3 is built with an opto-isolator. The output of the opto-isolator is provided to a noise reduction unit 4 which consists of a capacitance CA. Subsequently, the evaluating unit 2 comprises a voltage divider built by the resistance elements RE and Rpunup. This voltage divider provides the detection signal Vdetect to the control unit 6. The evaluation unit 2 in this scenario prepares the combined rectified signal V.* to a detection signal Vdetect with a logic high level +VDD in case no switched AC voltage VAC' or second AC voltage VAC2 is applied to the detection circuit. The detection signal Vdetect is applied to the control unit 6 of the ballast for lighting means. Since the output of the evaluation unit 2 is of digital nature, it can directly be applied to an ASIC or a microcontroller for further evaluation, such as frequency determination, mean-voltage determination and so on. * **

* * * *** * * * In Fig. 7 six simplified voltage diagrams of a detection * ** circuit according to the invention in a non-emergency * * **** state are shown. The switched AC voltage VAC1 and the *:* second AC voltage VAC2 are shown as a two periods sine AC **** voltage with identical frequencies, such as 50 Hertz or 60 **** *** Hertz, which is a common mains voltage frequency, * generated by power plants. Different frequency values might be used instead. The switched AC voltage VAC' is 30 applied to a full-wave rectifier 12 and the first rectified voltage VDC1 is obtained as shown in Fig. 7. The second AC voltage VAC2 is applied to a half-wave rectifier 11 and the second rectified voltage VDC2 is obtained as shown in Fig. 7. The frequency of the first rectified voltage VDc1 is as double as high as the frequency of the switched AC voltage VAC1. The frequency of the second rectified voltage Vcc2 is as high as the frequency of the second AC voltage VAC2. Since the frequency values of the switched AC voltage VAC1 and the second AC voltage VAC2 are the same, an easy detection of the presence/absence is achieved by evaluation of the frequencies of the rectified voltages VDcl and VDc2.

According to Fig. 7, both the switched AC voltage VAC1 and the second AC voltage VAC2 are applied to the ballast. Thus, the combined voltage Vcom is the result of the full-wave rectifier 12. A threshold voltage value Vmmeshoid might be applied with the threshold unit 5, to either digitize the combined voltage Vcc"m or to avoid low voltage distortions to be detected. Thus, the detection signal Vdetect is a binary voltage signal with a logical high level of +VDD and a logical low level of Ground potential. The frequency of the detection signal is as double as high as the frequency value of VAC1 or VAC2. Thus, the second AC * . lighting means can thus be switched based on the state of * ** the switched AC voltage VAC1.

* * **** * * * * In Fig. 8 six simplified voltage diagrams of a detection circuit according to the invention in a non-emergency state are shown in which the second AC voltage VAC2 is absent. Due to the absence, the full-wave rectifier 12 is not used and the combined voltage Vcom is a half-wave rectified signal with a frequency value identical to the frequency of the switched AC voltage VAC1. A threshold voltage value VThreshold might be applied with the threshold unit 5, to either digitize the combined voltage Vcom or to avoid low voltage distortions to be detected. Thus, the * .. * * *

*** . voltage VAC2 is present and no emergency is detected. The ** * * * ** * * * * ** * detection signal Vdetectis a binary voltage signal with a logical high level of +VDD and a logical low level of Ground potential. The frequency of the detection signal is as high as the frequency of the switched AC voltage VAC1.

Thus, the second AC voltage VA02 is not detected and an emergency case is detected. Thus, the lighting means is switched-on permanently independent on the state of the switched AC voltage VAC1. In case the ballast is an emergency ballast, supply voltage for supplying the lighting means might be derived from a auxiliary voltage source, connected to the ballast.

In Fig. 9 six simplified voltage diagrams of a detection circuit according to the invention in a non-emergency state are shown in which the second AC voltage VAC2 is replaced by a DC voltage DC Emergency-The DC voltage is applied in case the mains voltage is lost or the emergency light should be switched on, since an emergency case occurred. The DC voltage might be applied to each ballast of a building by a central supply unit of the building. * * * * * *

* * * * * * * Due to the DC voltage character at the second input * .. terminal of the rectifying unit, either the diode DA or * * * the diode DB of the full-wave rectifier 12 is permanently 25 conducting and applies the DC voltage to the evaluating unit 2. Thus, the combined voltage V. is a permanent DC ** voltage with a frequency value of zero Hertz. A threshold * voltage value VThreshold might be applied with the threshold unit 5, to either digitize the combined voltage V. or to 30 avoid low voltage distortions to be detected. Thus, the detection signal Vdetectis a permanent DC voltage with a logical high level of +VDD. The frequency of the detection signal Vdetect is zero Hertz, the slew rate is zero. Thus, the DC voltage is identified and an emergency case is detected. Thus, the lighting means is switched-on permanently independent on the state of the switched AC voltage VAci.

All embodiments described herein, shown and or claimed herein can be combined with each other.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents. * .. * * *

*** * with respect to one or more implementations, equivalent * * * alterations and modifications will occur to others skilled * in the art upon the reading and understanding of this * * * specification and the annexed drawings. In addition, while 25 a particular feature of the invention may have been disclosed with respect to only one of several * *** implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular 30 application.

Although the invention has been illustrated and described Reference signs 1 Rectifying unit 11 Half-wave rectifier 12 Full-wave rectifier 2 Evaluation unit 21 Output voltage 3 Isolation unit 4 Noise Reduction filter 5 Threshold detection circuit 6 Control circuit for ballast DA Rectifying Diode DH Rectifying Diode De Rectifying Diode DD Rectifying Diode VAC1 VAC2 VDC1 VDC2 Vcom First voltage, Control voltage Second voltage, Emergency voltage First rectified voltage Second rectified voltage Combined rectified voltage * * * VDetect Detection Signal Rpun-up Pull-up resistance * . * ** * * * * * * *40 25 RA RB Input Resistance Load Resistance Common Resistance * * * Re ** * * * *** ** * * * **** * * ** *

Claims

PATENT CLAIMS1. A ballast having a detection circuit for detecting characteristics of at least two different voltages supplied to independent input terminals of the ballast, wherein the detection circuit comprises: - a rectifying unit (1), wherein the rectifying unit (1) comprises: to -a first input terminal for applying a first externally supplied voltage (VAci), wherein the first voltage (Vim) is a switched AC voltage; - a second input terminal for applying a second externally supplied voltage (VAC2), wherein the second voltage (VAC2) is an AC voltage; - an evaluating unit (2), which is configured to provide a detection signal (Vdetect), wherein the detection signal indicates: - whether the first voltage (VA(n) is switched to the ballast; and * 4.. * . .*** * -whether the second voltage (VAC2) is applied to the * * * ballast or the second voltage (VAC2) is replaced by a * ** DC voltage. * * *
2. The detection circuit according to claim 1, ** * wherein the rectifying unit (1) comprises a single full-wave rectifier for rectifying the first voltage (VAci) and the second voltage (VAC2).

* 30
3. The detection circuit according to claim 2, 0000 wherein the first voltage (VAC1) is fully rectified by means of the full wave rectifying unit (1). * * * ** *
4. The detection circuit according to claim 2 or 3, wherein the second voltage (VAC2) is half-rectified by means of the full wave rectifying unit (1).
5. The detection circuit according to one of the preceding claims, wherein the detection signal (Vdetect) indicates the frequency of the rectified signal.
6. The detection circuit according to one of the preceding claims, wherein the detection signal (Vdetect) indicates an effective voltage value or a peak voltage value of the rectified signal.
7. The detection circuit according to one of the preceding claims, wherein an isolating unit (3) is arranged between the rectifying unit (1) and the evaluating unit (2) for galvanically isolating the first input terminal and the second input terminal from the output terminal.
8. The detection circuit according to one of the preceding claims, wherein a noise reduction unit (4) is arranged between the rectifying unit (1) and the evaluating unit (2).
9. The detection circuit according to one of the preceding claims, wherein a threshold detection unit (5) is arranged between the rectifying unit (1) and the evaluating unit (2).
10. The detection circuit according to one of the preceding claims, * .00 * * * ilea. * * * * 00* * * 0100411 * * * * * * * * * * ** * * * *** . * * . * *** * * * * **** * *** * **** **** * *** * wherein the detection signal is pulled up by a pull-up resistance element (Rpuii-up).
11. The detection circuit according to one of the 5 preceding claims, wherein the first voltage (VAci) and the second voltage (VAA:2) comprises a common terminal, wherein the common terminal incorporates a resistance element (Re).
12. A ballast for a lighting means, preferably an emergency lighting means, comprising a detection circuit according to one of the preceding claims, wherein the ballast further comprises a control unit (6) configured to control the lighting means, wherein the control unit (6) obtains the detection signal (V detect) * detect) Of the detecting circuit as an input signal.
13. The ballast according to claim 12, wherein the lighting means is permanently switched-on in 20 case the second voltage (VAc2) is absent or the second voltage (VAc2) is replaced by a DC voltage.
14. The ballast according to one of the claims 12 or 13, wherein the lighting means is switched-on in dependence on 25 the presence of the first voltage (VAci) in case the second voltage (Vm2) is present.
15. The ballast according to one of the claims 12 to 14, wherein the first voltage (VAci) is switched by means of a 30 switching element.