High intensity discharge lamp ballast
OwnerSimon Richard Greenwood, Stephen Soarinventors
Life of this patent
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Abstract
A means of ballasting for high intensity discharge (HID) lamps, wherein the necessary lamp striking voltage, warm-up current and steady state running current may all be controlled using only two power switching transistors 9,10 operating in two discrete modes. A further feature provides a means of lamp power control over a range of lamp voltages such that the lamp power input remains substantially constant throughout the ageing of the lamp 19. The use of this means of ballasting HID lamps can offer major cost benefits, lower circuit complexity, longer lamp life and colour maintenance and increased flexibility of the wiring installation and lamp position relative to the ballasting and striking means.
Claims38
A high intensity discharge lamp ballast circuit comprising:
- first and second high intensity discharge lamp terminals operable to connect with a lamp;
- a resonant circuit to which the first lamp terminal is connected;
- first switching means operable to connect the resonant circuit to a higher voltage rail of a source of high voltage;
- second switching means operable to connect the resonant circuit to a lower voltage rail of the source of high voltage;
- a first control operable to alternately select the first and second switching means to alternately supply current to the resonant circuit;
- and
- a second control operable to disable the switch which is selected by the first control.
A method of powering a lamp via a lamp ballast circuit, the method comprising the steps of:
- (a) providing a lower frequency turning on and off signal for first and second switches
- (b) providing a higher frequency turning on and off signal for the first and second switches;
- (c) repeatedly tuning off and on the first and second switches in response to the lower and higher frequency signals wherein the response is a function of AND logic;
- and
- (d) operating a high intensity discharge lamp in response to (c).
A high intensity discharge lamp ballast circuit comprising:
- first and second high intensity discharge lamp terminals operable to contact a lamp;
- a resonant circuit connected with the first lamp terminal;
- a first switch connected with the resonant circuit and a higher voltage rail;
- a second switch connected with the resonant circuit and a lower voltage rail;
- an oscillator connected with the first and second switches;
- and
- a comparator connected with the first and second switches;
- wherein the first and second switch are alternatively turned on in response to the oscillator and while turned on in response to the oscillator are operable to be turned off in response to the comparator.
A method of powering a high intensity discharge lamp with a lamp ballast circuit, the method comprising the steps of:
- (a) generating a lower frequency waveform containing a higher frequency ripple;
- and
- (b) operating the high intensity discharge lamp in response to the lower frequency waveform with the higher frequency ripple.
A high intensity discharge lamp ballast circuit comprising:
- an oscillator operable to generate a modulated frequency waveform;
- first and second switches responsive to the modulated frequency waveform;
- a resonant circuit connected with the first and second switches;
- and
- a high intensity discharge lamp connected with the resonant circuit;
- wherein the oscillator is operable in first and second modes, the first mode characterized by the modulated frequency waveform and the second mode characterized by a waveform with a frequency lower than the first mode, wherein the first and second switches are operable to generate a low frequency waveform with a higher frequency ripple in the second mode.
Dependencies are inferred from the claim text.