Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Impedance or current regulator in the supply circuit
Patent
1989-01-19
1991-01-08
Laroche, Eugene R.
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Impedance or current regulator in the supply circuit
315307, 315DIG7, H05B 3702, H05B 3904, H05B 4136
Patent
active
049838873
ABSTRACT:
A self-oscillating half-bridge inverter is powered from a DC voltage source and has a series-turned high-Q LC circuit connected across its output. A pair of fluorescent lamps is normally series-connected across the tank capacitor of the LC circuit. Whenever the lamp load is not so connected, the magnitude of the high-frequency current flowing through the LC circuit would tend to increase to destructively high levels. To prevent this from taking place, a negative feedback control circuit manifestly limits the magnitude of the high frequency current by reducing the forward conduction duty-cycle of each of the two bridge transistors whenever the peak current magnitude exceeds a pre-determined level. In particular, during normally loaded operation, each of the inverter's two transistors operate with a nearly 50% forward conduction duty-cycle. However, whenever the magnitude of the high frequency current exceeds a pre-determined level, the control circuit acts to shorten the forward conduction duty-cycle. As a result, with an unloaded high-Q series-tuned LC circuit connected across the inverter's output, the current through the LC circuit builds up to a certain level and remains there, thereby to provide a substantially fixed-magnitude output voltage suitable for properly starting the fluorescent lamps when they are connected. As soon as the lamps ignite, the resulting loading reduces the output voltage, thereby effectively removing the control circuit from operational involvement.
REFERENCES:
patent: 4307353 (1981-12-01), Nilssen
patent: 4554487 (1985-11-01), Nilssen
patent: 4581562 (1986-04-01), Nilssen
patent: 4677345 (1987-06-01), Nilssen
patent: 4692667 (1987-09-01), Nilssen
patent: 4722040 (1988-01-01), Ball
patent: 4763239 (1988-08-01), Ball
patent: 4819146 (1989-04-01), Nilssen
LaRoche Eugene R.
Yoo Do Hyum
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