Synthesis of dimmer output waveform within the dimmer logic circuit

Claim 1

A lighting control apparatus responsive to an electrical demand signal to control the portion of the voltage cycle during which the voltage is supplied to a lamp load from an A.C. voltage source; said apparatus comprising: a. solid-state switching means adapted to be connected in series with said load across said A.C. voltage source; b. a firing means having an output connected to said solid-state switching means, which firing means renders said solid-state switching means conductive when said firing means is initiated; c. a timing circuit connected to said firing means for initiating said firing means; d. a comparator circuit having first and second inputs and having an output connected to said timing circuit, the signal at said comparator output being effective to adjust said timing circuit in response to the difference between the signals on said inputs of said comparator circuit; e. a shaping circuit having an output connected to said first input of said comparator circuit, said shaping circuit being adapted to receiving said demand signal and to generating an output signal which is a function of said demand signals; and f. an output synthesis circuit having an output connected to said second input of said comparator circuit, said output synthesis circuit having a first input connected to the output of said timing circuit and a second input connected to the A.C. voltage source, said output synthesis circuit including means for generating an output signal which is essentially zero during that portion of the voltage cycle which said timing circuit has not initiated said firing means and which is a function of said A.C. voltage source during that portion of the voltage cycle which said timing circuit has initiated said firing means.