Incandescent lamp dimmer providing control voltage ies square law

Abstract

A dimmer and regulation circuit connected to an incandescent lamp load for controlling the voltage thereto from an ac source by gating off a portion of each cycle. The circuit used to provide the gating includes a pulse generator controlled by a timer producing a rectangular wave output. The input to the timer is from an operational amplifier, the inputs to which are, in turn, from a variable control voltage setting and from a load sensing network including components for non-linear curve shaping processing, such as in accordance with the IES square law curve. These inputs operate in a closed loop feedback system to provide line and load regulation after the sensed load voltage passes through the square law shaping network. This non-linear network includes a half wave rectifier and a capacitor that is part of two time constant networks, and which accumulates a charge during one-half of a cycle through a first resistance path and which discharges through a second resistance path.