Post on 24-Jan-2016
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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)
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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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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