DIMMABLE SCREW-IN COMPACT FLUORESCENT LAMP HAVING INTEGRAL ELECTRONIC BALLAST CIRCUIT

摘要

A dimmable ballast circuit for a compact fluorescent lamp controls the intensity of a lamp tube in response to a phase-control voltage received from a dimmer switch. The ballast circuit generates a lamp current through the lamp tube having a substantially constant envelope such that flicker in the lamp tube and electromagnetic interference (EMI) noise on an AC voltage supply are minimized. The dimmable ballast circuit comprises a high speed control circuit characterized by a cutoff frequency much greater than a frequency of a voltage ripple on a bus voltage of the ballast circuit. The dimmable ballast circuit may also comprise a non-linear amplifier circuit amplifying a lamp-current-feedback signal representative of the magnitude of the lamp current through the lamp.

主权项

1. A circuit for controlling a lighting load, the circuit comprising:
a bus-voltage-generating circuit configured to receive an input from an AC voltage supply and produce a DC bus voltage characterized by a low-frequency voltage ripple; a load regulation circuit comprising an inverter circuit and an output filter circuit, said inverter circuit configured to receive said DC bus voltage and generate a high-frequency inverter output signal, said output filter circuit configured to generate a load current conducted through said lighting load in response to said high-frequency inverter output signal, said inverter circuit configured to receive a drive control signal and to control the high-frequency inverter output signal to adjust the magnitude of said load current conducted through said lighting load in response to the drive control signal; a control circuit configured to produce said drive control signal for said inverter circuit to control said high-frequency inverter output signal to adjust the magnitude of said load current conducted through said lighting load, said control circuit configured to receive a first signal related to a target intensity level of said lighting load and a second signal related to an actual intensity level of said lighting load, said control circuit comprising an error amplifier circuit configured to compare said first and second signals to produce said drive control signal to cause said inverter circuit to control the high-frequency inverter output signal to illuminate said lighting load at said target intensity level; and a non-linear amplifier circuit configured to amplify said second signal by a first amount when the magnitude of said load current is below a current threshold, and by a second, smaller amount when the magnitude of said load current is above said current threshold, thereby increasing responsiveness of said error amplifier circuit to changes in magnitude of said load current at low magnitudes; wherein said bus-voltage-generating circuit is configured to produce said DC bus voltage to define an envelope for said load current, said error amplifier circuit configured to operate in a frequency range and configured to be responsive to said second signal at the frequency of said second signal thereby to cause said inverter circuit to control said high-frequency inverter output signal to reduce variation in said envelope of said load current.