Compact Fluorescent Lamps (CFLs)

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Compact Fluorescent Lamps (CFLs)

• Advantages over incandescent lamps– Energy savings– Longer lifetime

• Disadvantages over incandescent lamps– Higher initial cost– Not as easy to have 3-way control (dimming)

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Fluorescent vs. Incandescent

• Convert UV light to visible light

• Two-stage conversion– Electrons collide with

mercury atoms, causing photons of uv light to be released

– UV light converts to visible as it passes through the phosphor coating inside the glass tube

• Convert heat to light– Burn a filament (wire)

at very high temperature

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Fluorescent vs. Incandescent (cont.)

• More efficient– 25% of energy

consumed generates light

– Lower lamp temperature

– Longer life

• Less efficient– 5% of energy

consumed generates light

– High filament temperature (350°F)

– 2,000 hour lifetime

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Components and Assembly

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CFL Operation

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Electronic Ballast Block DiagramBlocks circuit-generated noise

AC-to-DC Conversion

DC-to-AC Conversion

Ignite and Run the Lamp

Feedback circuit to control lamp current

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Lamp Requirements

• Current to pre-heat the filaments– Low-Frequency AC to DC Conversion (input)

• High Voltage for Ignition

• High-Frequency AC current during running– High-Frequency DC to AC conversion (output)

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AC-toDC Conversion

Generate High-Frequency 50% duty-cycle AC Square Wave

Resonant tank circuit filters square wave to a sinusoid and drives lamp

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At turn-on

• During pre-ignition, the resonant tank is a series LC circuit with a high Q factor

• Control IC sweeps the half-bridge frequency from maximum down towards the resonant frequency of the LC circuit

• Lamp filaments are pre-heated as the frequency decreases and the lamp voltage and load current increase

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Lower the frequency until the lamp ignites

Filaments are pre-heating

To dim the lamp, increase the frequency

of the half-bridge

The gain of the resonant tank

decreases and the lamp current increases

The feedback circuit adjusts the half-bridge operating frequency

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ECE 442 Power Electronics 12

IRS2530D Dimming Control IC

Supply Voltage

Power and signal ground

Dimming reference and AC lamp current feedback input

VCO input

High-side gate driver supply

Half-bridge high-side gate driver output

High voltage supply return and half-bridge sensing input

Half-bridge low-side gate driver output

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IRS2530D Dimming Control Method

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Combine AC Lamp Current measurement with a

DC reference voltage at a single node

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3-Way Incandescent Lamp Dimming

Filament #1

Filament #2

Common

4-Position Switch

0 – OFF,

1 – Filament #1 –LOW,

2 – Filament #2 – MED,

3 – Filaments in Parallel -- HIGH

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3-Way Dimming for CFL

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3-Way Socket

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EMI Filter

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Rectifier and Voltage Doubler

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Control Circuit and Half-Bridge Inverter

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Resonant Tank

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Lamp-Current Sensing and Feedback

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Three-Way Interface Circuit

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Lamp Voltage and Current (Maximum)

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Lamp Voltage and Current (Medium)

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Lamp Voltage and Current (Minimum)

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Maximum: 43kHz, 240mA Medium: 62kHz, 94mA

Minimum: 67kHz, 31mA