Controller

Abstract

A controller is disclosed for controlling the optical output of at least one light emitting diode. The controller comprises a control unit and a power supply unit for supplying power to the at least one light emitting diode. The control unit is arranged to receive as input, first and second signals which are representative of the operating characteristics of the at least one light emitting diode, and which is further arranged to control the power output from the power supply unit to the at least one light emitting diode in dependence of the first and second signals. The first signal is representative of the current within the at least one light emitting diode and the second signal is representative of the temperature of the at least one light emitting diode so that the optical output from the at least one LED can be varied in accordance with the operating characteristics of the at least one light emitting diode.

1 . A controller for controlling the optical output of at least one light emitting diode, the controller comprising a control unit and a power supply unit for supplying a pulse width modulated signal to the at least one light emitting diode,
 the control unit being arranged to receive as input, first and second signals which are representative of the operating characteristics of the at least one light emitting diode, and which is further arranged to control a duty cycle of the pulse width modulated signal supplied from the power supply unit to the at least one light emitting diode in dependence of the first and second signals, wherein   the first signal is representative of the current within the at least one light emitting diode and the second signal is representative of the temperature of the at least one light emitting diode.   
     
     
         2 . A controller according to  claim 1 , wherein the control unit further receives as input a third signal which is representative of the time and a fourth signal which is representative of ambient lighting conditions. 
     
     
         3 . A controller according to  claim 2 , wherein the third signal is generated by a clock which is arranged to monitor the time. 
     
     
         4 . A controller according to  claim 3 , wherein the fourth signal is generated by a sensor which senses ambient lighting conditions. 
     
     
         5 . A controller according to  claim 4 , wherein the controller is arranged to control the optical output of a plurality of light emitting diodes. 
     
     
         6 . A controller  claim 5 , wherein the controller is powered by an alternating current mains supply. 
     
     
         7 . A controller according  claim 6 , wherein the power unit receives as input a rectified direct current supply which is obtained from the alternating current mains supply. 
     
     
         8 - 25 . (canceled) 
     
     
         26 . A method of controlling the optical output of at least one light emitting diode, the method comprising the steps of:
 providing a pulse width modulated signal to the at least one light emitting diode to cause the light emitting diode to produce an optical output;   generating a first signal which is representative of the current passing through the at least one light emitting diode;   generating a second signal which is representative of the temperature of the at least one light emitting diode;   adjusting a duty cycle of the pulse width modulated signal supplied to the at least one light emitting diode in dependence of the first and second signals.   
     
     
         27 . A lighting system comprising an array of light emitting diodes and at least one controller according to  claim 1 .