Title :
Problems with lamp current control using a PWM signal
Author_Institution :
OSRAM GmbH, Munich, Germany
Abstract :
In electronic ballasts for fluorescent lamps, it is common to use a half-bridge inverter. If the half-bridge switches are not gated with a 1:1 ratio, a PWM signal is generated at the output of the half-bridge to drive the lamp. To filter out the DC component of the lamp drive, a coupling capacitor is used. Despite of having no DC component in the lamp current, the darkening of one end of the lamp can be observed. This is caused by a discovered nonlinear electrophoresis effect of the mercury in the lamp. To avoid this effect, a new driving scheme for the half-bridge switches is presented. It can be described as toggled duty cycle (TDC). Some properties of the TDC are discussed.
Keywords :
DC-AC power convertors; PWM invertors; bridge circuits; control system synthesis; driver circuits; electric current control; fluorescent lamps; lamp accessories; lighting control; switching circuits; 1:1 gating ratio; DC component filtering; PWM signal; control design; coupling capacitor; electronic ballasts; fluorescent lamps; half-bridge inverter; half-bridge switches driving scheme; lamp current control; mercury; nonlinear electrophoresis effect; toggled duty cycle; Capacitors; Current control; Electrokinetics; Electronic ballasts; Filters; Fluorescent lamps; Pulse width modulation; Pulse width modulation inverters; Signal generators; Switches;
Conference_Titel :
Industry Applications Conference, 2001. Thirty-Sixth IAS Annual Meeting. Conference Record of the 2001 IEEE
Conference_Location :
Chicago, IL, USA
Print_ISBN :
0-7803-7114-3
DOI :
10.1109/IAS.2001.955466
