High-Frequency Dimmable Electronic Ballast for HID Lamps

A design methodology for acoustic resonance-free, high-frequency, dimmable electronic ballast for high-pressure sodium-vapour lamps

“…One important feature of frequency dimming scheme is that the lamp power (P lamp ) varies inversely with the driving frequency (f i ) as per equation (10) provided the input voltage (V o ) and the values of the circuit components are held constant 11,28…”

“…Conventionally, the dimming action is accomplished by switching frequency variation of the inverter of an e-ballast. 10–12,18 In spite of these earlier significant contributions in e-ballast design procedures, a few research gaps are identified in these works as mentioned below lack of a systematic and generalized methodology to determine AR-free driving frequencies of e-ballast for a wide dimming range; a single lamp wattage is taken into consideration; an ‘equivalent resistance’ of the HF inverter stage is considered instead of actual arc impedance of the lamp. Because of this approximation, complex equations need to be solved to estimate the ballast circuit parameters. …”

“…Although the LFSW topology is well accepted among ballast designers, it possesses some limitations -(i) sizes of inductor and capacitors are bigger due to low-frequency operation, (ii) separate power stage for lamp power control requires additional circuit components which affect the overall circuit efficiency and (iii) design and fabrication of the control circuit is complex. The aforesaid limitations can be addressed by highfrequency (HF) e-ballast with the following attributes [9][10][11][12] (i) smaller inductors and capacitors due to HF operation; (ii) fewer power stages and circuit components; (iii) simpler control circuitry; (iv) improved system efficacy and (v) enhanced life expectancy of the operated lamp due to disappearance of reignition and extinction peaks of lamp voltage waveform.…”

“…Conventionally, the dimming action is accomplished by switching frequency variation of the inverter of an e-ballast. [10][11][12]18 In spite of these earlier significant contributions in e-ballast design procedures, a few research gaps are identified in these works as mentioned below (i) lack of a systematic and generalized methodology to determine AR-free driving frequencies of e-ballast for a wide dimming range; (ii) a single lamp wattage is taken into consideration;…”