GB2283586A

GB2283586A - A battery and lamp economising circuit for hazard warning devices

Info

Publication number: GB2283586A
Application number: GB9322057A
Authority: GB
Inventors: Brenda Olliver
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-10-26
Filing date: 1993-10-26
Publication date: 1995-05-10
Also published as: GB9322057D0; GB2288890A; GB9414477D0; GB9421334D0; GB2286065A

Abstract

An application specific integrated circuit controls lamp current by pulse width high speed digital switching, with a mode selling facility to configure the circuit for individual applications. Electric current feedback information ensures ideal running conditions for the lamp and the same time conserves energy. Lamp current sensor circuit G provides a control signal to pulse width modulator F, and also flashes an LED alarm through a circuit D if a broken lamp is detected. Circuit D also responds to low battery voltage detection circuit C. A photo-sensitive switch A responds to ambient light. <IMAGE>

Description

A battery and lamp economising circuit for hazard warning devices Hazard warning devices, particularly those as used on roadwork use incandescent filament lamps as the light source and dry cell (non re-chargeable) energy sources. In order to obtain the requisite light output throughout the life of the energy source, the filament lamp is chosen so that it is over run when a new energy source is fitted, thus shortening the life of the lamp and wasting valuable energy.

The circuits at present in use are primitive in design and therefore the performance many-times falls outside of the standard specifications.There are four basic modes under which hazard warning devices operate, they are: a) A manually switched on device that burns continually.

b) A photo-sensitive switched device that responds to falling light levels then burns continually c) A photo-sensitive switched device that responds to falling light levels and then flashes the lamp d) A manually switched on device that flashes the lamp This invention is intended to address the above shortfalls in performance. From this point forward an abbreviation will be used: A.S.1.C. which will mean Application Specific integrated Circuit.

This invention is based on the design of circuitry that will be contained within an A.S.i.C.-and it's applications.The power to the lamp or high brightness L.E.D. will be controlled by high. speed digital switching, which will be pulse width proportioned so tat the lamp only receives the exact averaged current required for optimum perfo"rmance. During the switched off time of the lamp the circuit will apportion enough power to keep the filament in quiescent state in readiness for the next fully switched on interval, this facility reduces the transient current required by the filament when switched on from cold which in turn conserves the energy source further, it also reduces fatigue of the lamp mechanical-ly through the reduction of expansion and contraction.!n the case of a permanently glowing lamp that is switched on by a photo-sensitive device the quiescent state will not be cperable during off times, however there will be a gradual lead in of current at initial switch on.

All of the modes of operation and lamp electrical currents required of hazard warning devices will be integrated into the A.S.I.C. and selectable by way of user programable options, which can be achieved in several ways: i) simply by cutting or destroying wire links ii) by the use of electronic memory devices iii) by tactile resetable switches iiii) by mask programming at the fabrication stages of the A.S..C.

The A.S.I.C. will be engineered to operate from a wide range of power supply voltages typically being 3.4 volts to 14.0 volts, when switched on the A.S.I.C. will automatically detect the supply voltage and store the voltage value, the power supply voltage will be constantly monitored in order to d tect a spent energy source which is determined by the lamp being nable t give enough light output for compliance with the relat e standards in force. The detection of a spent energy source will trigger a drive circuit to flash a L.E.D. if the lamp is in flashing mode operation at the time of detecting spent energy source the L.E.D. will flash during the off period of the lamp in order to signal same to the operator of the device.The lamp current feedback information will also be used to detect a broken lamp, this will also flash the L.E.D. at a different rate to that of a spent energy source signal. As the electrical current to the lamp is under high speed control it will be possible to use the A.S.I.C. to power a low voltage lamp or very high brightness L.E.D. from a higher voltage source, thus extending the time from fully charged energy source to spent condition. The cost of construction of an A.S.I.C. for filll scale production is much lower than discrete assembly of piec arts.

A drawing is supplied which is in bloc symbol format. the bloc symbols are indicated by capital letters, the signals between blocks are indicated by lower case letters.

Legend: A '.Photo-sensitive switch B Logic control and memory unit C Voltage comparator D......Low battery indicator driver E Master oscillator and sub divider F Pulse width modulator G Lamp current sensing and control system H Lamp current driver array a.....Signal to logic from photo-sensitive switch b Bi-directional signals for voltage comparator c Signal from voltage comparator to L.E.D. driver d Logic signal to oscillator divider for mode in use e Logic signal to P.W.M. for mode in use f Flashing drive signal to L.E.D. driver g High speed pulses to P.W.M.

h Voltage signal to P.,.

1 Pulse width modulated signal te lamp driver J Current feedback signal to current sensor k Current derived signal to control P.W.M.

l lamp current signal to L.E.D. driver m Logic signal to L.E.D. driver mode in use n rflode select inputs Abbreviations used: P.W.M.......pulse width modulator L.E.D light emitting diode A.S.I.C application specific integrated circuit

Claims

Claims 1) A application specific integrated circuit for the control of incandescent filament lamps that will proportionally control the average electrical current flowing to tt-e lamp for optimum performance of that lamp under various supply voltages and conditions by way of pulse width controlled high speed digital switching of the energy source.

2) A application specific integrated circuit that will control a light emitting diode of high brightness all as in 1) 3) A application specific integrated circuit as in 1) that will allow custom external adjustments for various modes of operation in the control of light sources.

4) A application specific integrated circuit as in 1) that will automatically detect and signal a spent energy source.

5) A application specific integrated circuit as in 1) that will detect automatically, a open circuit lamp or light emitting diode and signal this status.

6) A application specific integrated circuit as in 1) that will operate on a wide voltage range and c: '.rol a lamp or light emitting diode ofi differing operational voltage at their optimum operating conditions.

7) A application specific integrated circuit as in 1) that will conserve energy by way of high speed digital proportional switching of an energy source.

8) A application specific integrated circuit as in l)that will conserve lamp, and energy source life by maintaining a quiescent current to the lamp during short lamp switched off periods.

9) A application specific integrated circuit as in 1) that will be more cost effective to produce than conventional circuitry.