Integrated circuit for lamp heating and dimming control
First Claim
1. An electronic ballast system, comprising:
- a variable voltage source generating a first signal indicative of a desired dim value for a hot cathode fluorescent lamp, and a second signal indicative of the average power of said variable voltage source;
a ballast controller comprising;
lamp filament current control circuitry comprising preheat filament current control circuitry generating a preheat filament current to the filaments of said lamp for a predetermined time period and steady state filament current control circuitry generating a steady state filament heating current in reverse proportion to said desired dim value during times after said predetermined period of time;
dimming circuitry comprising a burst PWM (pulse width modulated) signal generator receiving said first signal and generating a PWM dimming signal proportional to a desired dim value;
current feedback circuitry receiving a signal indicative of the current supplied to said lamp and comparing said signal indicative of the current supplied to said lamp and said PWM dimming signal to generate a variable power control signal;
inverter circuitry receiving said variable power control signal and generating an AC signal proportional to said power control signal by inverting said second signal; and
output circuitry coupled to said inverter circuitry comprising a resonant tank circuit receiving said AC signal to deliver striking and steady state sinusoidal power to said lamp.
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Accused Products
Abstract
An electronic ballast for lamps or tubes is provided. In one embodiment the present invention includes a ballast controller that includes filament heating circuitry and dimming circuitry. The filament heating circuitry may include preheat dimming circuits which preheat the filaments for a predetermined time period prior to striking the lamp, and steady-state heating circuitry that continually heats the filaments during steady state operation of the lamp. The steady state heating circuitry may be adapted to heat the filaments inversely proportional to the dim desired value of the lamp. The dimming circuitry may include conventional analog dimming and/or burst mode dimming to define a wide range of dimming characteristics for the lamp.
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Citations
2 Claims
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1. An electronic ballast system, comprising:
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a variable voltage source generating a first signal indicative of a desired dim value for a hot cathode fluorescent lamp, and a second signal indicative of the average power of said variable voltage source;
a ballast controller comprising;
lamp filament current control circuitry comprising preheat filament current control circuitry generating a preheat filament current to the filaments of said lamp for a predetermined time period and steady state filament current control circuitry generating a steady state filament heating current in reverse proportion to said desired dim value during times after said predetermined period of time;
dimming circuitry comprising a burst PWM (pulse width modulated) signal generator receiving said first signal and generating a PWM dimming signal proportional to a desired dim value;
current feedback circuitry receiving a signal indicative of the current supplied to said lamp and comparing said signal indicative of the current supplied to said lamp and said PWM dimming signal to generate a variable power control signal;
inverter circuitry receiving said variable power control signal and generating an AC signal proportional to said power control signal by inverting said second signal; and
output circuitry coupled to said inverter circuitry comprising a resonant tank circuit receiving said AC signal to deliver striking and steady state sinusoidal power to said lamp.
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2. An electronic ballast, comprising:
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a variable voltage source generating a first signal indicative of a desired dim value for a hot cathode fluorescent lamp, and a second signal indicative of the average power of said variable voltage source;
a ballast controller comprising;
lamp filament current control circuitry comprising preheat filament current control circuitry generating a preheat filament current to the filaments of said lamp for a predetermined time period and a steady state filament current control circuit generating a steady state filament heating current during times after said predetermined period of time;
dimming circuitry to vary the power delivered to said lamp as a function of the value of said first signal; and
a full bridge inverter circuit generating an AC signal from said second signal based on said dimming circuitry; and
output circuitry coupled to the output of said full bridge inverter comprising a resonant tank circuit receiving said AC signal and generating a sinusoidal signal to deliver striking and steady state power to said lamp.
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Specification