High Frequency Operation and Control of Low Pressure Sodium Lamps by Means of Electronic Ballast

Abstract

This paper describes the results of high frequency operetion and control of a 90 W low pressure sodium lamp by means of an electronic ballast.
The low pressure sodium lamp is operated at about 125 k Hz by means of at electronic ballast of self-commutated constant current push-pull inverter with power MOSFET from fiat DC voltage source. The circuit efficiency and luminous sefficacy are both im proved, and then, the total luminous efficacy increases about 1.3-1.5 times compared with the operation of conventional ballast for commercial 60 Hz frequency.
The effects of ripple, containing in a DC source of the rectified commercial AC voltage, on input power factor and total luminous efficacy are investigated by experiment. Based on the results, a controllable operation circuit considering both input power factor and luminous efficacy is proposed by authors. The experimental results by the circuit show good regulation for the constant voltage control to variation of supply voltage. The stable dimming is possible to 70% of rating light output without muct reduction of total luminous efficacy and input power factor.