System Modules
signal of the comparator (Comp Out) controls the power switch Q1 through the output buffer, which consists of transistors Q2, Q3, and Q4, resistors R10, R13, R34, R35, R36, and R37, and capacitor C7.
For discontinuous conduction mode the comparator output is disconnected from the Q4 transistor gate. The PWM1 pin is connected to the Q4 transistor gate.
Digital PFC is driven by the MCU. The MC68HC908LB8 peripherals used for PFC are listed below:
•AD converter — channels ADC1 and ADC2
•PWM0 for generating sine wave
•comparator
•IRQ pin for
The PFC control algorithm
•converts the sensed output voltage to a digital value
•provides software PI regulator for a voltage feedback loop
•programs its PWM channel to create the pattern of the input current
•synchronizes operation with the mains frequency using mains
The control algorithm is described in 5.2 Control Algorithm Description.
INPUT EMI FILTER AND BRIDGE RECTIFIER
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| C1 |
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J1 |
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| 10nF 275V X2 |
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2 | 2 | 3 | ||
I6 | 6 |
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| L6 |
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| CMFIL2 | |
I5 |
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NC |
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I3 |
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I1 |
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| C5 |
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| 4n7 250/1000V Y2 |
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1
R11
3K0
2
R14 2K0
PFC Current Sense
C8 
82pF
GND
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| 2.7mH |
| BOOST CONVERTER |
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| L1B |
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| U1 |
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| C2 |
| PFCIND3 |
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| DF1510S |
| 150nF 275V X23 |
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| 5 | D1 |
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4 AC2 | DC+ 1 |
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| DCB | CONN/HDR/2X1 | |||||
1 |
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| MURS160T3 |
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RV1 |
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275V |
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| 10nF 630V TC356 + | 560K |
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| G |
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| 22uF 450V | GND | |
2 |
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| PFC Gate | Q1 |
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AC1 | DC- |
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220K |
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| 15V |
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R5 |
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220K |
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2 |
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| C6 | R8 |
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R7 |
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220K | D15 |
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| R36 0R | R37 0R |
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| BAT48 | C27 |
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| GND | GND |
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| GND | GND |
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| BZV55C5V6 |
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| R10 |
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5V |
| GND | C |
| 2 | B | |
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| BC846B |
| C10 |
| E |
| R13 | PFC Gate | |
| 220nF | ||
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| 1 | 620R | E |
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| B | Q3 |
GND | R12 |
| BC856B |
| 10K |
| C |
| D |
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| G | BUFFER CIRCUIT | |
Comp - | Comp Out | Q4 | ||
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SMMBF0201
COMPARATOR CIRCUIT
GND
GND
Figure 4-3. Dimmable Light Ballast — Input and PFC
Dimmable Light Ballast with Power Factor Correction, Rev. 1
Freescale Semiconductor | 27 |
