Power supply and method for electric lighting device

Abstract

Disclosed herein are a power control system ( 110 ) and method for a light emitting diode (LED) lighting device. The system includes a rectifier ( 125 ) to rectify an input voltage, a squaring module ( 145 ) for squaring the rectified input voltage to produce a squared input voltage value; a filter ( 155 ) to filter said squared input voltage; a first function generator ( 160 ) for applying a first function to determine a light control signal ( 165 ); a second function generator ( 170 ) for applying a second function to determine a conductance factor ( 175 ), wherein said first function and said second function are independent functions of the root mean square (RMS) value of said input voltage; a multiplier ( 180 ) for multiplying said first multiplier signal with said rectified input signal to determine a current control signal ( 185 ); and a power supply ( 190 ) for determining an input light power to said LED lighting device and an input load power to a dissipative load ( 120 ), dependent upon said light control signal ( 165 ), said current control signal ( 185 ) and said rectified input voltage ( 140 ).

1 . A power supply system for controlling supply of power to an electric lighting device, said system comprising:
 a first function generator for generating a light control signal, dependent upon a first mathematical function of a root mean square (RMS) value of a received input voltage;   a second function generator for generating a current control signal, dependent upon a second mathematical function establishing a ratio of instantaneous input voltage to instantaneous input current as a mathematical function of the RMS value of said received input voltage, wherein said first function and second function are independent of one another; and   a power supply for presenting a light power signal to said electric lighting device and for presenting a load power to a dissipative load, dependent upon said light control signal, said current control signal, and said received input voltage.   
     
     
         2 . The power supply according to  claim 1 , wherein said ratio of instantaneous input voltage to instantaneous input current is substantially constant. 
     
     
         3 . The power supply according to  claim 1 , wherein said ratio of instantaneous input voltage to instantaneous input current of said second mathematical function is a scalar multiple of a mathematical function relating a ratio of the instantaneous voltage and an instantaneous current to the RMS input voltage of tungsten filament incandescent lamp. 
     
     
         4 . The power supply according to  claim 1 , wherein said second mathematical function relating the ratio of the instantaneous voltage and the instantaneous current to the RMS input voltage is a power function in which the ratio of the instantaneous voltage and the instantaneous current is proportional to the RMS value of the received input voltage raised to a power in the range of −1.0 to 1.0. 
     
     
         5 . The power supply according to  claim 4 , wherein said power is about 0.4. 
     
     
         6 . The power supply according to  claim 1 , wherein said first function utilises a break-point function, such that said light power signal presented to said electric lighting device is:
 0, for input RMS voltages below a first predetermined threshold V 1 ;   50% of nominal power, for input RMS voltages between a first predetermined threshold V 1  and a second predetermined threshold V 2 ;   an amount of power between 50% and 100% of nominal power, for input RMS voltages between said second predetermined threshold V 2  and a third predetermined threshold V 3 ; and   100% of nominal power, for input RMS voltages above said third predetermined threshold.   
     
     
         7 . A power control system for a light emitting diode (LED) lighting device, said system comprising:
 a first function generator for utilising a first function to generate a light control signal dependent upon a received input voltage;   a second function generator for utilising a second function to generate a conductance factor dependent upon said received input voltage, wherein said first function and said second function are independent functions of the root mean square (RMS) value of said input voltage;   a multiplier for determining a current control signal dependent upon said first multiplier signal and said received input voltage; and   a power supply for generating an input light power to present to said electric lighting device and an input load power to present to a dissipative load, dependent upon said light control signal, said current control signal, and said received input voltage.   
     
     
         8 . A method for controlling power supplied to a light emitting diode (LED) lighting device, said method comprising the steps of:
 determining a light control signal dependent upon a received input voltage and a first function, wherein said first function is a function of the root mean square (RMS) value of said received input voltage;   determining a conductance factor dependent upon said received input voltage and a second function, wherein said second function is a function of the RMS value of said received input voltage, said first and second functions being independent of one another;   determining a current control signal dependent upon said conductance factor and said received input voltage; and   generating an input light power to present to said lighting device and an input load power to present to a dissipative load, dependent upon said light control signal, said current control signal, and said received input voltage.   
     
     
         9 . The method according to  claim 8 , wherein said dissipative load is selected from the group consisting of: a resistor; an active dissipative device; and a Zener diode. 
     
     
         10 . The method according to  claim 8 , wherein said received input voltage is derived from a mains power supply. 
     
     
         11 . The method according to  claim 8 , wherein at least one of said first function and said second function is a break-point function. 
     
     
         12 . The method according to  claim 8 , wherein said LED lighting device is selected from the group of lighting devices consisting of: a road traffic control lantern; a railway signal lantern; and operating theatre lighting. 
     
     
         13 . The method according to  claim 8 , comprising the further steps of:
 rectifying said received input voltage to produce a direct current input voltage;   squaring said direct current input voltage to determine a squared voltage proportional to the square of the received input voltage; and   filtering said squared voltage to produce a steady state signal for use in determining said light control signal, wherein said steady state signal is proportional to an average of the square of the received input voltage.   
     
     
         14 . The method according to  claim 13 , wherein said squaring includes the steps of:
 sampling instantaneous values of said direct current input voltage; and   squaring those instantaneous values.   
     
     
         15 . The method according to  claim 8 , wherein said second function is a transfer function that produces a power function of the RMS value of the received input voltage. 
     
     
         16 . A power control system for a light emitting diode (LED) lighting device, said system comprising:
 a rectifier for rectifying a received input voltage;   a squaring module for squaring said rectified input voltage to determine a squared voltage value proportional to the square of the received input voltage;   a filter to filter said squared input voltage and produce a steady state signal;   a first function generator for applying a first function to the steady state signal to determine a light control signal;   a second function generator for applying a second function to the steady state signal to determine a conductance factor, wherein said first function and said second function are independent functions of the root mean square (RMS) value of said input voltage;   a multiplier for multiplying said conductance factor with said rectified input signal to determine a current control signal; and   a power supply for producing an input light power to said LED lighting device and an input load power to a dissipative load, dependent upon each of said light control signal, said current control signal, and said rectified input voltage.   
     
     
         17 . The power control system according to  claim 16 , wherein said system is adapted for use in at least one of a traffic signal lantern, a railway signal lantern, and an operating theatre light. 
     
     
         18 . A method for controlling power supplied to a light emitting diode (LED) lighting device, said method comprising the steps of:
 rectifying a received input voltage waveform;   squaring said rectified input voltage waveform to determine a squared voltage value proportional to the square of the received input voltage;   filtering said squared input voltage to produce a steady state signal;   applying a first function to the steady state signal to determine a light control signal, dependent upon said received input voltage;   applying a second function to the steady state signal to determine a conductance factor, dependent upon said received input voltage, wherein said first function and said second function are independent functions of the root mean square (RMS) value of said input voltage;   multiplying said conductance factor and said rectified input voltage waveform to determine a current control signal; and   generating an input light power for presenting to said LED lighting device and an input load power for presenting to a dissipative load, dependent upon said light control signal, said current control signal, and said rectified input voltage.