FIELD OF THE INVENTION

The invention relates to the field of LED lamps, in particular the field of manufacturing LED lamps.

BACKGROUND OF THE INVENTION

It is known that there is currently a tendency from incandescent lamps to more efficient light sources which is enforced by domestic and international regulation.

One of the more efficient light sources is the compact fluorescent lamp commonly abbreviated as CFL. A CFL is a type of fluorescent lamp which fits into most existing light fixtures used for incandescent lamps. CFLs can be divided into non-integrated CFLs in which the gas-filled tube of the lamp is releasably fitted in or onto a lamp housing and can be replaced independent of their corresponding driver, and integrated CFLs (commonly designated CFLi) in which the gas-filled tube is permanently mounted in or onto a lamp housing. In case of failure of the gas-filled tube of the CFLi, the entire product needs to be replaced. The abbreviation CFL thus refers to both types of lamps and no difference is made between integrated and non-integrated CFLs unless specifically stated.

CFLs are used to a large extend nowadays and might gain market size with the ban of incandescent lamps. However, with the rise of LED lamps, more and more CFLs may be replaced by higher efficient LED lamps.

As a consequence, CFLs will be exchanged by LED lamps in the near future while the CFLs are still expected to be functioning properly.

A high number of CFLs will then be returned from the market to the waste collectors.

However, from an environmental perspective it is important that the CFLs are returned for recycling instead of being deposited as waste. OBJECT OF THE INVENTION

It would be desirable to deal with the return of CFLs that still work properly in an

environmental friendly manner.

SUMMARY OF THE INVENTION

To address one or more of these concerns, a method for manufacturing a LED lamp is provided, comprising the following steps:

a. providing a lamp housing;

b. providing at least one LED;

c. retrieving a CFL driver from a CFL;

d. assembling the at least one LED, the CFL driver and the lamp housing, thereby electrically connecting the at least one LED to the CFL driver.

An advantage of the method according to the invention is that upon return of the CFL, the CFL driver is retrieved and used again, i.e. is re-used, as a driver for the LED lamp. In this way, not only the materials of the CFL driver are recycled, but also the functionality of the components. As a result, the environment is less affected by the return of the CFLs and the manufacturing costs of the LED lamps can be reduced.

In an embodiment, the lamp housing has electrical contacts to electrically connect the LED lamp to a mains power supply. The lamp housing may be provided as a separate component so that step d) may include electrically connecting the CFL driver to the electrical contacts of the lamp housing. Alternatively, a portion of the lamp housing, or the entire lamp housing, may also be retrieved from the CFL. In this case, the electrical connections between the CFL driver and the lamp housing may still be intact and the corresponding assembling step of connecting the CFL driver to the electrical contacts of the lamp housing may not be required.

Also an embodiment is envisaged in which a portion of the lamp housing is retrieved from the CFL - said portion being referred to as the CFL lamp housing - wherein said CFL lamp housing comprises electrical contacts originally arranged to connect the CFL to the mains power supply. The remaining portion of the lamp housing is then separately provided and referred to as the LED lamp housing, wherein said LED lamp housing is provided with electrical contacts to connect the LED lamp to the mains power supply. Step d) then preferably includes interconnecting at least some of the electrical contacts of the CFL lamp housing with the electrical contacts of the LED lamp housing to be able to power the CFL driver. Interconnecting the electrical contacts may be automatically done when mounting the CFL lamp housing into or onto the LED lamp housing.

The above can for instance be implemented by adapting a LED lamp fitting so that a smaller CFL lamp fitting can be inserted into the LED lamp fitting, e.g. by screwing as is usual for lamp fittings and the electrical connection between the LED lamp fitting and CFL lamp fitting can automatically be made. As the CFL driver does not have to be separated from the CFL lamp housing, i.e. fitting, and the CFL lamp housing can easily be mounted into the LED lamp housing, the method can be performed at a higher speed.

It is also envisaged that connection of the LED lamp to the mains power supply is provided in a different way, i.e. not via the lamp housing, e.g. using wireless power supply or electrical contacts which are not arranged on the lamp housing. In an embodiment, the CFL driver is retrieved from an integrated CFL, i.e. a CFLi. A CFLi is especially suitable to retrieve both the CFL and at least a portion of the lamp housing from.

An advantage of retrieving at least a portion of the lamp housing from the CFL is that more components are recycled and less assembly steps may be required, e.g. due to already existing electrical and/or mechanical connections between the retrieved lamp housing and CFL driver.

In an embodiment, the method includes the step of providing an electrical circuit configured to adjust an output of the CFL driver into a suitable driving signal for the at least one LED, and wherein step d) comprises the step of electrically connecting the at least one LED to the CFL driver via the electrical circuit. Usually a CFL driver is configured to operate at a voltage and current especially designed for the fluorescent tube and might even require certain properties, e.g. impedances, of the tube for proper operation. The desired operation characteristics of the at least one LED may be different from the operation characteristics of the tube. By providing the electrical circuit, the output signal of the CFL can be adjusted into a suitable driving signal for the at least one LED. Adjusting the output signal of the CFL driver using an electrical circuit may also be done for other reasons, such as electrical isolation of the at least one LED, reducing current ripple, dimming possibility, etc. To electrically isolate the CFL driver from the at least one LED and/or adjust the voltage level, the electrical circuit may be connected to the CFL driver via a transformer. Said transformer may also be part of the electrical circuit and may even be based on components that are already present in the CFL driver but may have been used there for different purposes. The retrieved CFL driver usually comprises a CFL output originally intended to be connected to a gas-filled tube of the CFL and also usually a ballast inductor electrically connected in series to the CFL output. The ballast inductor may be a discrete inductor component with two electrical connection pins, but may also be realized in the form of an intended or parasitic inductive behaviour of a more complex inductive component, such as an inductor with an electrical tap, or a transformer with multiple windings.

In an embodiment, the transformer which is arranged between the CFL driver and the electrical circuit as described above may be connected to the CFL output of the retrieved CFL driver. In another embodiment, the original ballast inductor of the retrieved CFL driver is removed and replaced by the transformer. In that case, the CFL output is preferably short-cut to keep the circuit closed if necessary. The original ballast inductor may also be used in forming the transformer, e.g. the ballast inductor is used as a primary winding of the transformer, and a secondary winding of the transformer is wound around the ballast inductor. Alternatively, the transformer is electrically connected in series to the ballast inductor and the CFL output is short-cut if necessary. The CFL output of the CFL driver may be provided with a parallel electrical circuit. Said parallel electrical circuit may be configured such that the CFL output not necessarily has to be short-cut in the abovementioned embodiments.

In an embodiment, the at least one LED and at least part of the electrical circuit are mounted on a LED carrier board.

In an embodiment, step d) comprises the following sub-steps:

dl) mounting the CFL driver into or onto the lamp housing;

d2) electrically connecting the CFL driver to electrical contacts of the lamp housing;

d3) mounting the LED carrier board into or onto said lamp housing;

d4) electrically connecting the electrical circuit on the LED carrier board to the CFL driver. Preferably, step d2) is automatically performed during step dl). Also preferably, step d4) is automatically performed during step d3).

In an embodiment, step d) comprises modifying the CFL driver. Modifying may include replacement of components with different valued but similar components, replacement of components by components of the same value, e.g. due to deteriorated performance as a result of aging, wear, etc, adding components, removing components, and changing the route of the electrical wiring.

The retrieved CFL driver may comprise a temperature dependent resistor, e.g. a positive temperature coefficient (PTC) resistor, electrically connected in parallel to the CFL output. The PTC resistor is usually used to short the CFL output and control the preheat phase of the CFL. The self heating of the PTC determines the preheat time of the CFL output in normal CFL operation. In an embodiment, the temperature dependent resistor is brought into thermal contact with the at least one LED during step d) of the method to provide a passive thermal protection of the at least one LED, e.g. via the LED carrier board. LEDs suffer in performance and lifetime when used at too high temperatures. The

temperature dependent resistor can be used to reduce the input power to the LEDs when the LEDs are running too hot. The temperature dependent resistor therefore needs to be in thermal contact with the LEDs in order to 'sense' the temperature of the LEDs. This thermal contact may be provided by a heat slug, e.g. a bend aluminium part) or via direct contact to the LEDs.

The retrieved CFL driver may comprise a start-up circuit to initiate electrical oscillation of the CFL driver. Normally, a CFL driver is a self-oscillating circuit once it is running, but it needs a kind of trigger signal to start the oscillation. The start-up circuit of the CFL driver is designed to provide that kind of trigger signal.

In an embodiment, the CFL driver is modified during step d) of the method such that the startup circuit can be used to control the amount of energy delivered to the at least one LED. This allows the LED lamp to be dimmable, but can also be used for temperature protection mentioned above. The embodiment is based on the insight that the start-up circuit can also be used to stop the oscillation which for instance allows PWM modulation of the power signal to the at least one LED.

To modify the CFL driver, a timer, a remote control device or a power line communication receiver may be provided, preferably on the LED carrier board. The on-off switching of the CFL driver for PWM modulation has to be done quite fast to avoid optical artefacts, preferably at frequencies above 400Hz.

The CFL driver may be based on an IC (integrated circuit) alternatively referred to as a processor. This IC may be used as well to control the amount of energy delivered to the at least one LED. A separate temperature sensor may be arranged to provide temperature information to the IC. When a dimming function is required, a dimming signal may be provided to the IC.

The invention also relates to a LED lamp comprising at least one LED and a CFL driver to drive the at least one LED, said CFL driver being retrieved from a CFL, preferably an integrated CFL.

The invention further relates to the use of a CFL driver from a CFL in a LED lamp.

Preferably, the CFL driver is from an integrated CFL.

These and other aspects of the invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 depicts a LED lamp according to an embodiment of the invention; Fig. 2 depicts an electrical diagram of a CFL driver before retrieval;

Fig. 3 depicts the electrical circuit of Fig. 2 after being modified and

assembled into the LED lamp.

DETAILED DESCRIPTION OF EXAMPLES

Figure 1 depicts schematically a LED lamp 1 according to an embodiment of the invention. The LED lamp 1 comprises a lamp housing 3 which has a light bulb portion 5 and a socket portion 7. The socket portion 7 comprises electrical contacts 9,11 to electrically connect the LED lamp 1 to a mains power supply (not shown). The socket portion 7 also comprises a thread to mechanically connect the LED lamp 1 to an armature and thereby electrically connect the electrical contacts of the socket portion to electrical contacts in the armature which in turn are electrically connected or connectable to the mains power supply. The light bulb portion 5 is a transparent shell made preferably of glass or plastic which shields the interior of the lamp housing and through which light is emitted when the LED lamp is in an on-state. Fig. 1 is adapted to also partially show the interior of the LED lamp 1. The socket portion 7 of the lamp housing 3 is provided with an internal thread in which a CFL socket 13 of an integrated CFL lamp can be inserted. The CFL socket 13 may alternatively be referred to as CFL lamp housing, and the lamp housing 3 may alternatively be referred to as LED lamp housing.

The CFL socket 13 is a former part of a lamp housing of a CFL and carries a CFL driver 15. The CFL socket 13 has electrical contacts which electrically connect to the electrical contacts 9,11 upon insertion of the CFL socket 13 into the socket portion 7. The electrical contacts of the CFL socket are electrically connected to the CFL driver 15, so that the CFL driver 15 is connectable to the mains power supply via the electrical contacts of the CFL socket 13 and the electrical contacts 9,11 of the socket portion 7.

When the CFL socket 13 is inserted into the lamp housing 3, the CFL driver 15 is also brought into thermal contact with a heat sink 17 surrounding the CFL driver 15. Alternatively or additionally, cooling openings may be provided in the lamp housing 3 to allow an air flow to the CFL socket 13 and CFL driver 15.

On top of the CFL driver 15, a LED carrier board 19 is mounted. Said LED carrier board 19 carries in this case four LEDs 21 and provides for an electrical connection between the LEDs 21 and the CFL driver 15 as schematically depicted by connections 23,25. Prior to mounting the LED carrier board on top of the CFL driver, the CFL driver may be modified to be suitable to drive the LEDs.

An advantage of the LED lamp according to the invention is that the CFL driver 15 and the CFL socket 13 carrying the CFL can be retrieved from manufactured CFLs which still function properly. This is environmental friendly as not only the materials, but also the functionalities of the components are re-used. By using the CFL socket 13, assembling the CFL driver 15 into the lamp housing 3 is much easier. Further, safety precautions taken in the CFL to protect the CFL driver from abnormal operation conditions caused by the mains power supply are also re-used in the LED lamp. The safety precautions may comprise a fusible resistor or other component positioned between the CFL socket and the CFL driver.

Due to the change from CFL to LED, the cooling requirement may have changed, which is solved in this embodiment by providing the heat sink 17 in the form of a larger lamp housing 3 and thermally connect the heat sink to the CFL driver and possibly to the LEDs.

Figure 2 depicts an electrical diagram of a typical CFL driver before modification. The diagram includes the connection with a mains power supply PS and the connection to a gas- filled tube T in which light is generated. The CFL driving circuit comprises a rectifier portion composed of diodes D1,D2,D3,D4, resistor R7 and capacitor CI which smoothes the output of the rectifier portion. After the rectifier portion, an EMI filter portion is provided to minimize the disturbance towards the mains power supply PS. The EMI filter portion is composed of inductor LI, and capacitor C2. The EMI filter portion in turn is connected to a half bridge inverter comprising transistors Q1,Q2, transformer components Tl_a,Tl_b,Tl_c, resistors R1,R2,R4,R5, ballast inductor L2, and capacitor C7. The half bridge converter provides a high frequency switching voltage.

Oscillation of the half bridge converter is triggered by a start-up circuit composed of resistors R3,R6, capacitor C5, zener diode D6 and normal diode D5. When the driver is switched on, the C5 capacitor of the start-up circuit is charged via resistors R3 and R6. At some point in time, the capacitor C5 reaches a voltage level such that zener diode D6 breaks down thereby triggering transistor Q2. This starts the oscillation of the half bridge inverter. In steady-state operation, diode D5 repetitively discharges capacitor C5 to prevent the start-up circuit from triggering transistor Q2 again. The CFL output of the CFL is electrically connected to the gas-filled tube T. Parallel to the tube T are connected capacitor C7 and a PTC resistor, in which PTC stands for Positive Temperature Coefficient. The capacitor C7 forms a resonance circuit with inductor L2 so that capacitor C7 can reach such a high voltage that the lamp can be ignited. After ignition, the resonance circuit is bypassed by the tube T. The PTC resistor determines the preheat time of the contacts EC1,EC2 of the tube T by self heating of the PTC. Capacitor C4 blocks DC current through the tube T.

Figure 3 depicts the electrical diagram of the LED lamp including partially the CFL driver of Fig. 2. In principle, the diagram portion to the left of transformer portion Tl a is similar to the CFL driver and thus the components have identical reference symbols. However, components may be replaced by similar component possibly having other component values. For instance, capacitor C2 is known to have lost part of its capacity and to be increased in impedance and leakage due to current and temperature stress during operation in the original CFL and aging (limited shelf life). To solve the reduced capacity and increased impedance, one could replace the capacitor by a new one. Alternatively, an additional capacitor could be connected in parallel to capacitor C2. The new or additional capacitor may be mounted onto the CFL driver, but could also be a part of a LED carrier board. Although a connection to LEDs LE1,LE2,LE3, could have been made at the CFL output (EC1,EC2, see Fig. 2), this embodiment has short cut these contacts EC1,EC2 thereby bypassing the PTC and the capacitor C7 of Fig. 2. Between the LEDs LE1,LE2,LE3 an electrical circuit E is provided which is connected to the CFL driver via a transformer composed of inductors L2, L3, L4. This may be done by winding inductors L3, L4 around inductor L2 being present on the CFL driver, or the inductor L2 is replaced by a transformer which may be partially or entirely placed on an LED carrier board also carrying the LEDs and the electrical circuit. Further, the transformer may also be connected to the CFL driver between inductor L2 and transformer portion Tl a.

Usage of a transformer allows to electrically isolate the LEDs from the mains voltage. In this isolation is not required (e.g. because the electrical isolation is provided in the LED carrier board, between this LED carrier board and the lamp housing 3, or in the lamp housing 3, simpler arrangements to adapt the CFL driver to LED operation can be used. For instance a tapped inductor, i.e. an autotransformer without galvanic isolation, could be used. In the simplest version, the forward voltage of the LEDs is selected such that no adaptation of the voltage is required. However, the CFL driver may still need to be modified or expanded with rectification, resistors, z-diodes, inductors, capacitors, etc., to match the dynamic

characteristics of the LEDs with the CFL driver.

The electrical circuit E rectifies the output of the transformer using diodes D7 and D8 and smoothing the output of the diodes using capacitor C6.

The start-up circuit of the CFL driver can be used to dim the LEDs. By connecting the base of transistor Q2 to ground the oscillation of the CFL driver is stopped and no power is supplied to the LEDs. By applying a new trigger pulse, the driver will start again. If this is done at a high enough frequency, PWM modulation can be used to dim the LEDs. Parts of the original CFL start-up circuit may be used for this dimming function, but additional components may be necessary to start and stop the oscillation.

Above, an example is given for a self-oscillating driver, where the power level is influenced by pulse width modulation, i.e. the alternating activation and deactivation of the driver.

However, some CFL drivers are based on other topologies, e.g. based on driver IC's. These driver IC's may offer similar possibilities, e.g. via a shutdown input, and under- voltage-lookout-detection, or a power monitoring pin, such that by manipulation, e.g. shorting to ground, applying a static or pulse shaped voltage or current, of a signal of the CFL driver, the power delivery to the LEDs can also be adjusted.

In an alternative embodiment, the PTC resistor is not bypassed, but kept in the circuit and thermally connected to the LEDs so that it can be used as a passive thermal protection of the LEDs. The PTC resistor is described as possibly being used as a temperature sensor, but other temperature sensor types may also be used to measure the temperature of the drive, the LEDs or any other relevant temperature of the lamp. As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms "a" or "an", as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically.

A single processor or other unit may fulfill the functions of several items recited in the claims.

The terms program, software application, and the like as used herein, are defined as a sequence of instructions designed for execution on a computer system. A program, computer program, or software application may include a subroutine, a function, a procedure, an object method, an object implementation, an executable application, an applet, a servlet, a source code, an object code, a shared library/dynamic load library and/or other sequence of instructions designed for execution on a computer system. A computer program may be stored and/or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.