Abstract: A light dimmer control system for controlling the current supplied from a DC power source to high power illuminating lamps. The current fed to the lamp is controlled by manually setting the width of the pulsed output of a pulse width modulator by means of a potentiometer or the like appropriately connected to the pulse width modulator. The output of the pulse width modulator drives an output driver circuit which is connected in series with the current path to the lamp. The lamp power is provided from a DC source which is controlled by the output driver circuit in series with the lamp. The power for the semiconductor components of the DC controller, which includes the pulse width modulator, is provided from the same DC source and stepped down by a DC-DC converter. A logical control circuit is employed which enables the energization of the system only when both the polarity of the DC input supply is correct and the low voltage DC is on, thereby minimizing the possibility of damaging system components.

Abstract: A ballast circuit for driving a sodium vapor lamp includes a ballast transformer having a primary winding connected to a constant current power source. A secondary winding of the transformer is connected across the lamp. A high voltage oscillator responsive to the voltage across the lamp superimposes high voltage pulses across the lamp when the voltage across the lamp is above a predetermined level. A time delay circuit, triggered by the initial voltage across the primary winding when the power from the power source is turned on, opens a normally closed switch connected across the primary winding a predetermined time interval after the time delay circuit is triggered.