Frequency controlled half-bridge inverter for variable loads

Details Frequency controlled half-bridge inverter for variable loads Frequency controlled half-bridge inverter for variable loads

2000-06-30

2001-12-11

Vu, David (Department: 2821)

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Silicon controlled rectifier ignition

C315S219000, C315S224000, C315SDIG007

Reexamination Certificate

active

06329761

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high frequency switchmode power inverters and specifically to high frequency electronic ballasts for gas discharge devices. More specifically, the present invention relates to a high frequency electronic ballast for high intensity discharge (HID) lamps.
2. Prior Art
The prior art is replete with many known circuits providing high frequency ballast for gas discharge lamps, especially for high intensity (HID) lamps. For instance, high efficient electronic ballasts which can be used with HID (HPS) lamps are U.S. Pat. No. 5,097,183, entitled “Master-Slave Half-Bridge DC-to-AC Switchmode Power Inverter” and U.S. Pat. No. 5,229,927, entitled “Self-Symmetrizing and Self-Oscillating Half-Bridge Power Inverter”, assigned to the assignee of the present invention.
An important application of switchmode power inverters is supplying gas discharge devices, especially high intensity discharge (HID) lamps in the range of 35W to 400W. In this case, the load impedance of the inverter is a HID lamp connected in series with an inductor. In the case of a high frequency powering of the HID lamp, the interaction between the high frequency ballast and the lamp is stronger than that of a conventional low frequency (50/60 Hz) ballast. The high frequency ballast can be significantly better than a conventional low frequency (50/60 Hz) ballast due to its lessened weight and essentially high efficiency. Additionally, the high frequency ballast, utilized with an HID lamp would have a simple, reliable dimming capability and an essentially more reliable light switch (day and night switch) than the conventional low frequency ballasts.
Therefore, the critical design targets for high frequency ballasts supplying HID lamps would be the following:
a) very high efficiency, >94% (energy saving and low temperature rise of the critical components);
b) fully controlled lamp power eliminating the effects of input voltage fluctuation and the lamp aging;
c) dimming capability, from 100% to 50% (35%);
d) automatic light switching (day and night time switch);
e) over temperature protection;
f) automatic switch off in the case of lamp failure;
g) instant re-ignition of the warmed up lamp; and
h) isolated interface circuit providing the connection of several ballasts and therefore implementing fully controlled lighting system.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a high frequency switchmode half-bridge square wave inverter which has a substantially increased efficiency in a wide frequency and temperature range.
A second object of the present invention to provide an electronic ballast for gas discharge devices having substantially increased efficiency, stability and reliability.
A further object of the present invention to provide an electronic ballast for high intensity discharge lamps implementing the ideal ballast curve.
Another object of the present invention to provide a high frequency and high voltage ignition circuit for a reliable ignition of HID lamps, especially the instant re-ignition of warmed-up lamps, in a very wide temperature range.
A further object of the present invention to provide an electronic ballast for high intensity discharge lamps with built-in dimming capability.
Another object of the present invention to provide an electronic ballast for high intensity discharge lamps with built-in light switch controlled externally by a simple photoresistor.
These and other objects, features and advantages of the present invention will be more readily apparent from the following detailed description, wherein reference is made to the drawings.


REFERENCES:
patent: 5097183 (1992-03-01), Vila-Masot et al.
patent: 5229927 (1993-07-01), Vila-Masot et al.
patent: 5932976 (1999-08-01), Maheshwari et al.

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