Fluorescent lamp dimmer with multi-function integrated circuit
In one embodiment, a fluorescent lamp dimming circuit includes power factor correction control, dimming control, and switching devices. The power factor correction control may be connected to power factor correction circuitry that produces a regulated DC buss. The dimming control circuit may be connected to the input of the fluorescent lamp dimming circuit for producing a driver signal whose frequency varies depending on the input voltage waveform perhaps as modified by a dimmer. The control circuit may produce a drive signal with a duty cycle profile to drive switching devices. The switching devices invert the DC buss voltage to an AC voltage waveform for driving a resonant tank circuit. The resonant tank circuit may include an inductance, a capacitance, and the impedance of a fluorescent lamp. The AC voltage waveform when applied to the resonant tank circuit may cause the fluorescent lamp to dim based on the dimmer setting.
1. A fluorescent lamp dimming circuit comprising:
a full-wave rectifier operatively connected to an input to the fluorescent lamp dimming circuit for rectifying an input AC voltage into a rectified DC voltage;
a power factor correction circuit operatively connected to the full-wave rectifier, the power factor correction circuit configured to produce a regulated DC buss voltage;
a multi-function integrated circuit operatively connected to the power factor correction circuit comprising:
a power factor control circuit for controlling the power factor correction circuit to produce the regulated DC buss voltage at a substantially constant voltage regardless of characteristics of the input AC voltage;
a dimming control circuit configured to receive the regulated DC buss voltage and the input AC voltage and produce a dimmer driver signal, where a set of parameters of the dimmer driver signal vary depending on the input AC voltage, the input AC voltage being modified by a dimmer; and
one or more switching devices operatively connected to the dimming control circuit, the one or more switching devices driven by the dimmer driver signal and inverting the regulated DC buss voltage to a primary voltage, wherein the one or more switching devices are configured to turn on simultaneously and to turn off simultaneously at increasing intervals, the intervals being a fraction of a duty cycle, until the duty cycle is reached; and
a resonant tank circuit comprising a transformer and a capacitor, the resonant tank configured to receive the primary voltage.
2. The fluorescent lamp dimming circuit of claim 1 where the set of parameters include one or more of a frequency and a duty cycle of the dimmer driver signal.
3. The fluorescent lamp dimming circuit of claim 1 where the dimming control circuit is configured to communicate to the power factor control circuit a regulation voltage for the regulated DC buss voltage, the regulation voltage varying depending on the input AC voltage.
4. The fluorescent lamp dimming circuit of claim 1 where the dimmer is one of a forward phase control dimmer, a reverse phase control dimmer, and an amplitude variation control dimmer.
5. The fluorescent lamp dimming circuit of claim 1 where the one or more switching devices are one of metal oxide semiconductor field effect transistors, bipolar junction transistors, and insulated gate bipolar transistors.
6. A dimmable compact fluorescent light bulb comprising:
a connector end for operatively connecting the dimmable compact fluorescent light bulb to an electrical socket; and
an electronic ballast circuit operatively connected to the connector end, the electronic ballast circuit comprising:
an AC to DC converter for converting an AC voltage from the electrical socket to a DC voltage;
a power factor correction circuit operatively connected to the AC to DC converter for correcting power factor and establishing a regulated DC buss voltage;
a multi-function integrated circuit operatively connected to the power factor correction circuit comprising,
a power factor control circuit for controlling the power factor correction circuit in response to a sensed condition of the regulated DC buss voltage and the AC voltage from the electrical socket;
a dimming control circuit for controlling dimming of the dimmable compact fluorescent light bulb by varying the frequency of a drive signal based on the AC voltage from the electrical socket; and
one or more switching devices operatively connected to the dimming control circuit and driven by the drive signal for converting the regulated DC buss voltage to a primary AC voltage waveform, wherein the one or more switching devices are configured to turn on simultaneously and to turn off simultaneously at increasing intervals, the intervals being a fraction of a duty cycle, until the duty cycle is reached; and
a resonance circuit comprising a transformer and a capacitor, the resonance circuit including a compact fluorescent lamp, the resonance circuit operatively connected to the integrated circuit, the primary AC voltage waveform being applied to the resonance circuit to power the compact fluorescent lamp.
7. The dimmable compact fluorescent light bulb of claim 6 where the dimming control circuit communicates with the power factor control circuit to vary the regulated DC buss voltage based on the AC voltage from the electrical socket.
8. The dimmable compact fluorescent light bulb of claim 6 where the connector end is one of a bayonet end and an Edison screw base end.