GB2204191A - Lighting adaptor - Google Patents

Abstract

A lighting device (1) is convertible to a mains lamp socket to drive a low voltage lamp and has a dimmer mounted on it. The device comprises a body (2), a socket (3) for receiving a low voltage lamp (4) and a screw or bayonet fitting (5). The body (2) houses voltage reducing means and special function means (7) - e.g. a photosensitive switch or proximity switch - may be connected to the electronics housed within the body (2). A dimmer control (9) is provided intermediate the fitting (5) and the body (2) and is operable from outside the body. <IMAGE>

Description

LIGHTING ADAPTOR THIS INVENTION relates to a lighting device, for example for connecting lamps to power sources of incompatible voltages.

Embodiments of this invention provide a convenient lighting device for use in connecting lamps to power sources of incompatible voltages.

In accordance with this invention there is provided a lighting device comprising a body having connection means for a low voltage lamp and voltage reducing means connected to provide power to the lamp connection means and to receive power from a /plug formation plug formation on the body, which is adapted to be connected to a mains outlet, the voltage reducing means including a light dimmer adjustable from outside the body.

In embodiments of the invention, the voltage reducing means includes an electronic transformer, preferably of a high frequency, for driving a filament lamp of a lower voltage than the mains.

In embodiments of the invention the plug formation is of an Edison screw or bayonet type fitting. In embodiments of the invention the body has a heat insulated connection between the lamp socket body part and the body part housing the voltage reducing means, and the connection is in the form of a ring or disc of insulating material held spaced away from each body part by spacers. around the periphery of the insulator.

In embodiments of the invention the body includes, or is connectible to, additional function means. Such additional function means may, for example, include sound and/or light sensitive /switch apparatus, switch apparatus, a proximity detector switch for switching when detecting a person in an area or approaching the lamp, and/or backup battery power supply means chargeable by the mains supply.

In embodiments of the invention, the voltage reducing means is a lamp driver circuit comprising a high frequency oscillator arranged to be powered off an alternating current mains supply and to drive a step-down transformer for driving a low voltage filament lamp load, the oscillator having a control circuit arranged to trigger it over a variable angle of mains supply frequency.

Preferably the control circuit includes a capacitor connected to be charged through a variable load and a switching device connected to trigger the oscillator by allowing a predetermined voltage on the capacitor to bias a transistor of the oscillator on, there being a discharge path for the capacitor after oscillation commences in use, until the capacitor voltage drops below the trigger voltage.

/Further the Preferably the variable load is a variable resistor, the switch is a diac, and the oscillator output is full wave rectified.

Embodiments of the circuit include high voltage spike protection and further include, alternatively or additionally, high temperature protection which will shut the circuit down in the event of excessive temperatures.

Preferably the . two facilities are combined in one circuit.

Further preferably, this one circuit is a voltage dividing circuit connected across the positive and negative rails of the lamp driver circuit, operable to activate a transistor when the divided voltage reaches a predetermined limit, with the transistor connected to earth the switching part of the lamp driver circuit when activated and thereby disable it.

Embodiments of the invention are described below by way of example only, and with reference to the accompanying drawings, in which: /Figure 1 is Figure 1 is a side view of an embodiment of lighting device according to the invention, and; Figure 2 is a circuit diagram of an embodiment of lamp driver circuit according to the invention.

Referring to Figure 1, a lighting device (1) has a central cylindrical metal material body part (2), with a lamp housing and socket part (3) for a low voltage lamp (4) at one end, and at the other end a screw type fitting (5) projecting concentrically therefrom. The body part (2) houses electronic transformer means (not shown) encapsulated therein and connected to the screw fitting (5) to be powered from a mains supply lamp outlet with an Edison screw socket. The electronic transformer reduces the mains supply voltage to an acceptable voltage for the lamp (4) and provides the power to the connections for the lamp (4) as well as the required electrical isolation.

Two socket openings (6) are provided in the body for receiving pins on the housing (7) of a special function means to be connected to the electronics contained in the body (2). The special function means may provide a proximity switch sensor for the lamp (4), or, in this /instance, for instance, for a light sensor switch with a light sensor (8) located thereon, for switching the lamp on and off when it is correspondingly dark or light around the lamp. The sensor (8) is mounted on the housing (7) which contains the required electronic circuitry to switch the pin connections plugged into the socket (6) and make or break the circuit to the lamp.

A dimming control (9) is included in a neck portion of the body, between the screw fitting and bulb (4), and takes the form of a potentiometer which is screw adjustable through an opening in the body.

A variety of different function means can be provided for optional use with the device.

Referring to Figure 2, a lamp driver circuit (10) is supplied with power from an alternating current mains source (12) which feeds directly to.. a full wave rectifier bridge (13), having the full wave rectified output on positive line (14) and returning along line (15).

/An oscillator An oscillator indicated generally by numeral (16) comprises two NPN transistors (17) connected in cascade across the positive and negative lines (14) and (15), driving a mid point output along line (18), and having their base to emitter connections taken through a current transformer indicated generally by numeral (19), in saturated transformer current feedback configuration, which is known in the art per se.

The output along line (18) is fed back to the rails through two balancing capacitors (20), and passes through a step-down transformer (21) which has its output winding driving a low voltage direct current lamp (22).

The oscillator is connected to be triggered through a voltage applied from a resistor (23) to the base of the lower transistor (17) in the cascade. Should the voltage at the base provide a switch on voltage for the base emitter junction, and the resistor (23) is connected to a diac (24) which is connected to be fed from one resistance (25) of two parallel resistances (25) and (26), both of which are fed from the positive line through a variable resistance (27). Resistance /(25) is (25) is connected from the diac junction through a capacitor (29) to line (5). The feed from the same position as the diac connection is taken to the output through a diode (28).

In use, the full wave rectified supply is applied across the circuit, and the voltage divider provided by the resistor (25), (26) and (27) vary the rate of charging of the capacitor (29), until the trigger voltage for the diac is built up, which then causes a trigger voltage.to be passed through resistor (23) to the transistor (17), thus commencing oscillation of the oscillator circuit (16). Once this happens, the circuit will oscillate at a high frequency, preferably say 25 kHz, within the envelope of the rectified mains frequency supply.

The oscillator however will only oscillate and thus pass the envelope through to the load at or higher than the trigger voltage; Thus each half wave of mains supply will be delayed by a certain degree depending on the setting of the voltage for switching on the oscillator, and this setting will be adjusted by the variable resistor (27), which will vary the charge rate /to the to the capacitor (29). On switch on of the oscillator, the capacitor (29) can discharge through the diode (28) into the output.

Both the transformers (19) and (21) are toroids, and can thus be made together with the rest of the circuit to be relatively small, so that they can be located within the same housing as the lamp and plug arrangement for connecting the lamp to a mains supply.

An additional feature may be provided for the circuit, and is indicated generally at (31) demarcated in dotted lines. The circuit (31) comprises a voltage divider of resistor (32) and (33) between the positive and negative rails, with the voltage dividing point (34) feeding into the base of a transistor (35). The collector of the transistor is connected to the drive line (18) and to the lamp and switching circuit, in a manner that will cause the circuit to shut down if the transistor is on, since the emitter of the transistor is connected to the negative rail (15).

Thus in use, when the positive rail voltage increases in a transient spike, the transistor (35) will earth /the switching the switching part of the drive circuit, and shut it down to protect it. Clearly as soon as the stable operating conditions are resumed, the transistor will switch off and the switching circuit will be restored.

In the event of an excessive temperature build-up, the temperature changes the operating limits of the transistor, causing it to switch on, as well as leak, at lower voltages than otherwise would be the case, and it has been found in practice that this leads to the same shutdown action under excessive temperature.

It is considered that the illustrated embodiment provides a convenient lighting device for use in many situations, in one mechanical package.

Variations may be made to the described embodiment without departing from the scope of the invention. In particular, a wide variety of different functions may be provided in the function means, and the function means need not necessarily be removable from the device, but can be integral therewith.

/CLAIMS

Claims (1)

1. CLAIMS 1. A lighting . device comprising a body having a connection means for a low voltage lamp and voltage reducing means connected to provide power to the lamp connection means and to receive power from a plug formation on the body, which is adapted to be connected to a mains outlet, the voltage reducing means including a light dimmer adjustable from outside the body.

   2. A. device as claimed in Claim l,in which the voltage reducing means includes an electronic transformer for driving a filament lamp of a different voltage from the mains.

   A A device as claimed in Claim 1 or Claim 2, in which the transformer operates on a frequency of approximately 25kHz.

   /4. An device A A device as claimed in any one of the preceding claims, in which the plug formation is of a screw or bayonet type fitting.

   5. A device as claimed in any one of the preceding claims, in which the body has a heat insulated connection between the lamp socket body part and the body part housing the voltage reducing means.

   6. A device as claimed in Claim 5, in which the connection is in the form of a ring or disc of insulating material held spaced away from each body part by spacers around the periphery of the invention.

   7. A device as claimed in any one of the preceding claims, in which the body includes or is connectible to, additional function means, being at least one of sound sensitive switch apparatus, light sensitive switch apparatus, proximity detector switch apparatus for switching when detecting a person is near the lamp, and, backup battery power supply means rechargeable by the mains supply.

   /8. An device 8. A device as claimed in any one of the preceding claims, in which the voltage reducing means is a lamp driver circuit comprising a high frequency oscillator arranged to be powered off an alternating current mains supply and to drive a step-down transformer for driving a low voltage lamp load, the oscillator having a rectified output and ,a control circuit arranged to trigger it over a variable angle of mains supply frequency.

   9. A device as claimed in Claim 8, in which the control circuit includes a capacitor connected to be charged through a variable load and a switching device connected to trigger the oscillator by allowing a predetermined voltage on the capacitor, to bias a transistor of the oscillator on, there being a discharge path for the capacitor after oscillation commences in use, until the capacitor voltage drops below the trigger voltage.

   10. A device as claimed in Claim 9 in which the variable load is a variable resistor, and the switch is a diac.

   /11. A device 11. A device as claimed in any one of the preceding claims in which the circuit includes high voltage spike protection.

   12. A device according to any one of the preceding claims, in which the circuit includes high temperature protection which will shut the circuit down in the event of excessive temperatures.

   13. A device as claimed in Claim 11 or Claim 12, in which the high voltage and temperature protection are in one circuit, which is connected across the positive and negative rails of the lamp driver circuit, and which is operable to activate a transistor connected to earth the switching part of the lamp driver circuit when activated and thereby disable it.

   14. A device substantially as hereinbefore described with reference to, and as illustrated in, either of the accompanying drawings.

   15. Any and all novel features and combinations and subcombinations thereof substantially as hereinbefore described.