ISOLATED DRIVER FOR LIGHTING MEANS

Abstract

The invention relates to an isolated driver (100) for lighting means (109), comprising: a primary circuit (100a), a secondary circuit (100b), an isolation barrier (106) separating the primary circuit (100a) and the secondary circuit (100b), wherein a ground potential of the primary circuit (100a) and a ground potential of the secondary circuit (100b) are connected via a capacitor (107), and a control circuit (111) on the secondary side (100b), monitoring a current to/from the capacitor (107) to the ground potential of the secondary circuit (100b) and issuing a mains (101) failure signal in case the current does not meet predefined conditions, preferably in case no such current is detected.

Claims

1. An isolated driver (100) for lighting means (109), comprising: a primary circuit (100a); a secondary circuit (100b); an isolation barrier (106) separating the primary circuit (100a) and the secondary circuit (100b), wherein a ground potential of the primary circuit (100a) and a ground potential of the secondary circuit (100b) are connected via a capacitor (107); and a control circuit (111) on the secondary side (100b), monitoring a current to/from the capacitor (107) to the ground potential of the secondary circuit (100b) and issuing a mains (101) failure signal in case the current does not meet predefined conditions, preferably in case no such current or a certain change in such current is detected.

2. The isolated driver (100) of claim 1, wherein the mains failure signal causes the activation of an emergency lighting operation stage supplying an emergency lighting means.

3. The isolated driver (100) of claim 1, wherein a shunt resistor (113) is connected in series between the capacitor (107) and the ground potential of the secondary circuit (100b).

4. The isolated driver (100) of claim 1, wherein the mains voltage (101) is connected to an electromagnetic interference, EMI, filter (102) on the primary side circuit (100a).

5. The isolated driver (100) of claim 4, wherein the capacitor (107) forms a part of the EMI filter (102).

6. The isolated driver (100) of claim 4, wherein the EMI filter (102) is connected to a full- or half-bridge 103, wherein the full- or half-bridge is connected to the ground potential of the primary side circuit 100a.

7. The isolated driver (100) of claim 6, wherein the full- or half-bridge (103) is connected to a primary side switching circuit (104) and wherein the primary side switching circuit (104) is connected to the capacitor (107).

8. The isolated driver (100) of claim 1, wherein the isolation barrier (106) is a safety extra-low-voltage, SELV, barrier.

9. The isolated driver (100) of claim 1, wherein the capacitor (107) is a class Y capacitor.

10. The isolated driver (100) of claim 1, wherein the control circuit (111) is further configured to measure an amplitude of the mains voltage (101).

11. The isolated driver (100) of claim 1, wherein the control circuit (111) is further configured to derive a timing signal with regard to a frequency of the mains voltage (101).

12. A method (200) for operating an isolated driver (100) for lighting means (109), comprising: separating (201) a primary circuit (100a) and a secondary circuit (100b), wherein a ground potential of the primary circuit (100a) and a ground potential of the secondary circuit (100b) are connected via a capacitor (107); monitoring (202) a current to/from the capacitor (107) to the ground potential of the secondary circuit (100b); and issuing (203) a mains (101) failure signal in case the current does not meet predefined conditions, preferably in case no such current or a certain change in such current is detected.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention will be explained in the followings together with the figures.

[0029] FIG. 1 shows an isolated driver for lighting means according to an embodiment; and

[0030] FIG. 2 shows a method for operating an isolated driver for lighting means according to an embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Aspects of the present invention are described herein in the context of an isolated driver for lighting means.

[0032] The present invention is described more fully hereinafter with reference to the accompanying drawings, in which various aspects of the present invention are shown. This invention however may be embodied in many different forms and should not be construed as limited to the various aspects of the present invention presented through this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. The various aspects of the present invention illustrated in the drawings may not be drawn to scale. Rather, the dimensions of the various features may be expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus.

[0033] Various aspects of an isolated driver for lighting means will be presented. However, as those skilled in the art will readily appreciate, these aspects may be extended to aspects of an isolated drivers for lighting means without departing from the invention.

[0034] The term “LED luminaire” shall mean a luminaire with a light source comprising one or more LEDs. LEDs are well-known in the art, and therefore, will only briefly be discussed to provide a complete description of the invention.

[0035] It is further understood that the aspect of the present invention might contain integrated circuits that are readily manufacturable using conventional semiconductor technologies, such as complementary metal-oxide semiconductor technology, short “CMOS”. In addition, the aspects of the present invention may be implemented with other manufacturing processes for making optical as well as electrical devices. Reference will now be made in detail to implementations of the exemplary aspects as illustrated in the accompanying drawings. The same references signs will be used throughout the drawings and the following detailed descriptions to refer to the same or like parts.

[0036] Now referring to FIG. 1, an isolated driver 100 for lighting means 109 is shown according to an embodiment. The isolated driver 100 may be formed by an isolated primary side switched driver or an isolated secondary side switched driver or a combination of both. The driver may implement e.g. a flyback, resonant halfbridge or boost topology.

[0037] The isolated driver 100 for lighting means 109 comprises a primary circuit 100a preferably having at least one actively controlled switch in series to a primary side winding, a secondary circuit 100b, an isolation barrier 106 having said primary side winding and a secondary side winding, and separating the primary circuit 100a and the secondary circuit 100b. A ground potential of the primary circuit 100a and a ground potential of the secondary circuit 100b are connected via a capacitor 107.

[0038] Moreover, the driver 100 comprises a control circuit 111 on the secondary side 100b, monitoring a current to/from the capacitor 107 to the ground potential of the secondary circuit or side 100b and issuing a mains failure signal in case the current does not meet predefined conditions, preferably in case no such current is detected.

[0039] The mains failure signal may e.g. cause starting the operation of the lighting means off the battery power.

[0040] The switch on the primary side is preferably controlled by a primary-side control circuit which may perform a feedback-control of a secondary side current or voltage, using a feedback signal obtained at the primary side or the secondary side.

[0041] The control circuit 111 may control e.g. a converter for driving the LEDs off the battery power.

[0042] The control circuit 111 may be connected to a wired or wireless dimming interface and may receive dimming information.

[0043] This provides the advantage that instead of using extra discrete circuitry specifically for this purpose, the same result can be achieved almost instantly by the use of an existing capacitor 107, for example a class Y capacitor, connected across the SELV barrier 106 together with a resistor or bead used for EMI purposes.

[0044] Furthermore, the primary side 100a comprises an EMI filter 102 supplied by the mains 101 voltage, a bridge 103, the primary side switching circuit 104 and preferably a primary side controller 105. The primary side controller 105 can be configured to control the primary side switching circuit 104. The bridge 103 can be a half- or full-bridge.

[0045] The secondary side 100b comprises a secondary LED driver 108 configured to drive the LED load 109. Moreover, a battery 112 can be provided which is charged by a secondary side battery charger 110 and which is configured to supply the LED load 109 in case of a mains 101 failure.

[0046] The control circuit 111 may also control the primary side switching circuit 104, for example by a control path crossing the isolation barrier, for instance via an transformer or optocoupler. In such case the control circuit 111 may take over functions from the primary side controller 105.

[0047] Embodiments of this invention make use of existing EMI improvement techniques such as class Y capacitors and series resistor/bead between primary 100a and secondary circuits 100b) to, then, measure a voltage on the secondary side 100b due to the residual current flow through the class Y capacitor. The AC current can be rectified and filtered, if necessary, to provide a DC voltage to the secondary side control circuit 111, e.g. formed by a microcontroller for example. This current only flows when the mains 101 is present and stops flowing when the mains 101 fails. The amount of current is directly proportional to the mains voltage level.

[0048] This provides the advantage that use is made of existing circuitries, in particular capacitor 107, to provide a second function directly without the need for a separate circuit. Moreover, physical space is used efficiently and costs are reduced. For instance the capacitor 107 may form a part of the EMI filter 102.

[0049] Moreover, embodiments of the present invention allow for a very fast mains detection (both mains presence and mains loss). Moreover, advantageously, components are saved since the same components are used for doing multiple things. Furthermore, cost are minimised and the very fast detection of mains present and mains loss allows to provide lighting in emergency devices in a very fast and efficient way.

[0050] Moreover, embodiments of the invention allow for a fast and reliable mains detection without the need for specific circuitry. It can use existing circuitry that is present on SELV rated emergency drivers and only simple signal processing circuitry may be needed to allow secondary control.

[0051] Thus, in case mains voltage is present at the primary side 100a, an AC current will flow through the class Y capacitor 107 across the SELV-isolation barrier 106. Therefore, when arranging a resistor or bead 113 on the secondary side 100b, through which this AC current is directed to flow, the voltage drop across this resistor or bead 113 can be used in order to analyze the mains voltage (indirectly) with regard to at least one of the following aspects: [0052] presence or non-presence of AC voltage at the primary side 100a (especially important for emergency drivers); [0053] presence or non-presence of DC voltage at the primary side 100a (especially important for emergency drivers), [0054] presence or non-presence of a rectified AC voltage at the primary side 100a (especially important for emergency drivers), [0055] measuring the amplitude of the mains voltage, as the AC current is proportional to the amplitude of the AC mains voltage level, and/or deriving a timing signal with regard to the frequency of the mains voltage. [0056] Therefore, in embodiments of the present invention, no dedicated (primary side 100a) mains detection circuitry is required, but rather the presence of the already present class Y capacitor 107 across the SELV-isolation barrier 106 can be used for the mains voltage detection.

[0057] FIG. 2 shows a method 200 for operating an isolated driver for lighting means 100 according to an embodiment.

[0058] The method 200 comprises the steps of: [0059] separating 201 a primary circuit 100a and a secondary circuit 100b, wherein a ground potential of the primary circuit 100a and a ground potential of the secondary circuit 100b are connected via a capacitor 107; [0060] monitoring 202 a current to/from the capacitor 107 to the ground potential of the secondary circuit 100b; and [0061] issuing 203 a mains failure signal in case the current does not meet predefined conditions, preferably in case no such current or a certain change in such current is detected.

[0062] All features of all embodiments described, shown and/or claimed herein can be combined with each other.

[0063] 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 of 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 equivalence.

[0064] Although the invention has been illustrated and described with respect to one or more implementations, equivalent alternations and modifications will occur to those skilled in the art upon the reading of the understanding of the specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only of the several implementations, such features may be combined with one or more other features of the other implementations as may be desired and advantage for any given or particular application.