AU2008200904B2 - Rapid start of lighting devices - Google Patents

Abstract

The invention provides a method for rapid start of lighting devices having a capacitor which is charged to enable the lighting device to be used when the lights are being used and wherein, when the lights are switched off any current discharge path from the capacitor is disconnected to thereby-maintain the charge of the capacitor. The invention also provides an electrical circuit for rapid starting of lighting devices, the circuit consisting of: a. a power supply circuit, for the supply of a DC voltage and current b. afirst current controlling device, the input of which is connected to the output of the power supply circuit c. a storage capacitor, one side of which is connected to the output side of the first current controlling device d. a second current controlling device, the input of which is connected to one side of the storage capacitor e. a load, the input of which is connected to the output of the second current controlling device Y:SPEC\SoILu Rapid Start of Lighting Devices 260208.wpd February 26, 2008 C') F- -li (00

Description

Regulation 3.2 -l AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT APPLICANT: Solux Pty. Limited NUMBER: FILING DATE: Invention Title: RAPID START OF LIGHTING DEVICES The following statement is a full description of this invention, including the best method of performing it known to me: -2 RAPID START OF LIGHTING DEVICES This invention relates to the rapid start of lighting devices. Background to the Invention There are many devices which require a DC supply: for example, LED based traffic signal lights and in such applications as traffic signal lights it is necessary for these 10 to switch to their 'on' state rapidly as lights are used in sequence and only one light is illuminated at any particular time and there should be no or only a very short delay as the various lights switch. . Generally the DC supply will include a storage capacitor and these capacitors are 15 normally arranged to discharge whenever the light is powered down. There are two general reasons for this: the first being that the circuit design which incorporates the capacitor can be such that it is desirable that the capacitor be permitted to discharge, as this enables a relatively cheap circuit to be used; the other is that if the capacitor is of substantial capacity and it is left charged for any period then it 20 can present a danger to servicemen or others who have access to the equipment in which the capacitor is located. Generally, a permanently connected discharge path exists across the capacitor, due to loading from the light circuit and/or any feedback control monitoring the DC 25 voltage. These act as a discharge path even when the light associated therewith is not being used. With such designs, when the DC supply is powered up, time is taken to charge the capacitors to the required voltage level before the light can operate normally. This 30 can result in a delay in the start-up time of the light. It also results in higher YASPEC\Solux Rapid Stan of Lighting Devices 260208.wpd February 26, 2008 -3 electrical stresses on the storage capacitors and input power supply circuit due to the in-rush currents that occur during the charging process. In an application where the light is powered on and off on a regular basis, these in-rush currents can cause premature ageing of the storage capacitors, thus reducing the service life of the 5 light. Outline of the Invention The object of the present invention is to provide a method for rapid start of lighting 10 devices in which the storage capacitor is retained in a charged condition when the lights associated therewith are turned off. The invention includes a method for rapid start of lighting devices having a capacitor which is charged to enable the lighting device to be used and wherein, 15 when the lights are switched off any current discharge path from the capacitor is disconnected to thereby maintain the charge of the capacitor. In a preferred form, the system controlling the operation is an electrical circuit consisting of: 20 a. a power supply circuit, for the supply of a DC voltage and current b. a first current controlling device, the input of which is connected to the output of the power supply circuit c. a storage capacitor, one side of which is connected to the output side of the first current controlling device 25 d. a second current controlling device, the input of which is connected to one side of the storage capacitor e. a load, the input of which is connected to the output of the second current controlling device. 30 Y:\SPEC\Solux Rapid Start of Lighting Devices 260208.wpd February 26, 2008 -4 In this way, any impedance across the capacitor is changed to a high impedance state when the lights are switched off so that the capacitor retains its normal operating voltage, or a voltage close to this, during any quiescent period. 5 When power is reapplied to cause the lights to ignite, the capacitor is again placed in the circuit and because it is already charged, or substantially so, the time to initiate the lighting of the lights is minimised. 10 Description of an Embodiment of the Invention In order that the invention can be more readily understood and how it may be carried into effect, reference shall now be made, by way of example only, to the accompanying drawing, in which: 15 FIGURE 1 shows an embodiment of the present invention. Figure 1 shows an AC energy source (6), connected to the input of a power supply circuit (1). The output of the power supply circuit (1) connects to a 20 switch or current limiting device (2), which in turn connects to the storage capacitor (4). The output of the storage capacitor (4) is connected to the load (5) via a second switch or current limiting device (3). A feedback circuit (7) is employed to monitor the output of the power supply (1) and make any adjustments to ensure the correct output. 25 In initial operation, energy is first supplied to the input of the power supply circuit (1) from the AC energy source (6). Switch (2) is then closed and current then begins to flow into the storage capacitor (4), causing the voltage across it to increase. The rate at which this occurs will be dependent upon the total 30 capacitance of the storage capacitor, the maximum current the output of the power supply circuit can provide and the value of any series impedance between the output of the power supply circuit and the storage capacitor. Y:\SPEC\Sobx Rapid Start of Lighting Devices 260208.wpd February 26, 2008 -5 When the voltage across the storage capacitor has reached the desired level, switch (3) is closed and the energy stored in the capacitor (4) is applied across the load (5). The load may consist of any number of LEDs, or some other form of light emitting device, such as an incandescent or quartz-halogen bulb, s without departing from the scope of the invention. To power down the load, switch (3) is opened and the output of the storage capacitor is then disconnected from the load (5) and current flow ceases. Switch (2) is then opened; isolating the storage capacitor (4) from the output of 10 the power supply, thus ensuring any charge within the storage capacitor will remain even when the AC energy source (6) is powered down. If required and to ensure that the capacitor (4) is fully charged, the switch (2) can be opened after switch (3) so there is a period during which current can flow to the capacitor. 15 This completes one switching cycle of load powered up, load powered down. At the start of the subsequent switching cycles, the storage capacitor is at or very nearly at full charge, so that when switch (2) is closed, only a small amount 20 of charge current flows from the output of the power supply circuit (1), ensuring the in-rush currents into the storage capacitor are negligible. It is preferred that the capacitor used has an operating voltage which is not sufficient to be considered hazardous, so the fact that the capacitor retains its 25 charge does not cause any risk to servicemen or others who have access to the circuit that might otherwise be the case if high voltage capacitors were used. In the device of the invention, it is ensured, by the use of switches or other current limiting devices that any load or feed-back circuits loading the capacitor, 30 and which could permit discharging of the capacitor when power is disconnected, are isolated from the capacitor. Y:\SPEC\Solux Rapid Star of Lighting Devices 260208.wpd Febmary 26, 2008 -6 Specifically, on the power supply side of the circuitry to the capacitor, there is a circuit which prevents reverse flow current, which in turn prevents the discharge of the capacitor. 5 This would normally be achieved by providing an input circuit which is a single or bridge diode arrangement so that the reverse flow is prevented. Similarly, on the load side of the capacitor, we have a circuit which disconnects 10 any load, in turn preventing discharge of the capacitor. The circuits which prevent current flow from the capacitor can be physical switches, such as relays but are preferably electronic switches such as power transformers or switching circuits in the form of ICS. Both switches can be part 15 of the same component which is in series with the capacitor so that the capacitor is switched out of circuit and thus is disconnected from the power supply and any loads.. The system is particularly suitable for traffic signalling and flashing signage 20 applications where lighting products are cycled on and off on a regular basis. It is a desiderata of such systems that one light switches off as one switches on and there should be no delay between the switching operations but, at the same time, two lights should not be illuminated at the same time. The invention improves this start functionality of the lights of the system. 25 Another advantage of the invention is, because the capacitor is always substantially or fully charged, the in-rush current from the power supply, which can occur in normal applications when capacitors are discharged and charged on a regular basis, is significantly reduced. 30 Y:\SPEC\Solux Rapid Start of Lighting Devices 260208.wpd February 26, 2008 -7 Whilst there has been described herein a particular form of the invention, it is to be understood that various modifications can be made in this without departing from the spirit and scope thereof. Y:\SPEC\Solux Rapid Start of Lighting Devices 260208.wpd Februry 26, 2008

Claims (5)

1. A method for facilitating rapid start of lighting devices comprising: connecting a capacitor to a power source such that the capacitor receives charge from said power supply to place the capacitor in a charged state; upon receiving a signal to activate said lighting devices, connecting said capacitor to said lighting devices such that the charge stored in said capacitor is supplied to operate said lighting devices; upon receiving a signal to de-activate the lighting devices, disconnecting the capacitor from the lighting devices to cease flow of charge from said capacitor to said lighting devices whilst maintaining connection between said capacitor and said power source to maintain capacitor in said charged state; and whilst said lighting devices remain de-activated, isolating said capacitor from said power source and any other current discharge path to maintain the capacitor in said charged state such that upon receiving a signal to activate the lighting devices said charge stored in the capacitor is directly supplied to the lighting devices to facilitate rapid start of said lighting devices.

2. The method as claimed in claim 1 wherein the capacitor is selectively connected to the power supply to enable charging thereof and is isolated therefrom when the charge state of the capacitor is fully charged and/or wherein the lighting devices are de-activated.

3. The method as claimed in claim 2 wherein when the lighting devices are de-activated, the capacitor is isolated from the lighting device.

4. The method as claimed in claim 2 or claim 3 wherein the capacitor is isolated from the power supply and the lighting devices by way of switches.

5. The method as claimed in claim 2 or claim 3 wherein the capacitor is isolated from the power supply and the lighting devices by way of one or more current limiting means having an impedance such as to prevent current flow from the capacitor.