ATAVRFBKIT Atmel, ATAVRFBKIT Datasheet - Page 29

• Manufacturer Part Number: ATAVRFBKIT
• Description: KIT DEMO BALLAST FOR AT90PWM2
• Manufacturer: Atmel
• Series: AVR®r

Specifications of ATAVRFBKIT

• Main Purpose: Lighting, Ballast Control
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: AT90PWM2, AT90PWM3
• Primary Attributes: 18 W, Up to 2 Type T8 Lamps, Dimmable, Auto Detect of Swiss or DALI
• Secondary Attributes: Power Factor Corrected (PFC), 90 to 265 VAC, 90 to 370 VDC
• Data Bus Width: 8 bit
• Core Chip: AT90PWM2B
• Topology: Boost
• No. Of Outputs: 1
• Dimming Control Type: Digital
• Kit Contents: Board CD Docs
• Development Tool Type: Hardware / Software - Eval/Demo Board
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

7597B–AVR–10/07
Conclusion
7.3
7-27
Appendix 3: PFC
Basics
In practice, C1 may have to be larger depending on the amount of ripple allowed by C2
and to account for component tolerances, minimum voltage, and current in the regulator
diode. C1 must be a non-polarized type with a voltage rating to withstand the peak line
voltage including transients. A high quality film capacitor is recommended.
The function of the PFC boost regulator is to produce a regulated DC supply voltage
from a full wave rectified AC line voltage while maintaining a unity power factor load.
This means that the current drawn from the line must be sinusoidal and in phase with
the line voltage.
The ballast PFC circuit accomplishes this by means of a boost converter operating (See
Figure 7-3) at critical conduction so that the current waveform is triangular (See Figure
7-4).
Figure 7-3. PFC Boost Regulator
The boost switch ON time is maintained constant over each half cycle of the input volt-
age sinusoid. Therefore the peak current for each switching cycle is proportional to the
line voltage which is nearly constant during Ton. (Ipeak = Vin x Ton/L). Since the aver-
age value of a triangular waveform is half its peak value, the average current drawn is
also proportional to the line voltage.
Figure 7-4. Main voltage supply cutting
Ipeak = Vin x Ton / L
Imean = Ipeak/2
VOLTAGE
Main Supply
DRIVING
POWER
Voltage
PFC
Vin
PFC BOOST REGULATOR
Ion = (Vin x t )/ L
PFC Inductor
ATAVRFBKIT / EVLB001 User Guide
Actual switching frequency
Ioff
is higher than shown
PFC Switch
Vbus