ECE 442 Power Electronics 1

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)

ECE 442 Power Electronics 2

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

ECE 442 Power Electronics 3

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

ECE 442 Power Electronics 4

Components and Assembly

ECE 442 Power Electronics 5

CFL Operation

ECE 442 Power Electronics 6

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

ECE 442 Power Electronics 7

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)

ECE 442 Power Electronics 8

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

ECE 442 Power Electronics 10

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

ECE 442 Power Electronics 11

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

ECE 442 Power Electronics 13

IRS2530D Dimming Control Method

ECE 442 Power Electronics 14

Combine AC Lamp Current measurement with a

DC reference voltage at a single node

ECE 442 Power Electronics 15

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

ECE 442 Power Electronics 17

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

ECE 442 Power Electronics 21

Resonant Tank

ECE 442 Power Electronics 22

Lamp-Current Sensing and Feedback

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Three-Way Interface Circuit

ECE 442 Power Electronics 24

Lamp Voltage and Current (Maximum)

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Lamp Voltage and Current (Medium)

ECE 442 Power Electronics 26

Lamp Voltage and Current (Minimum)

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

Minimum: 67kHz, 31mA