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參數(shù)資料
| 型號： | FAN4800IN |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Low Start-Up Current PFC/PWM Controller Combos |
| 中文描述： | 1 A POWER FACTOR CONTROLLER WITH POST REGULATOR, 250 kHz SWITCHING FREQ-MAX, PDIP16 |
| 封裝： | LEAD FREE, PLASTIC, MS-001, DIP-16 |
| 文件頁數(shù)： | 9/19頁 |
| 文件大?。?/td> | 369K |
| 代理商： | FAN4800IN |
FAN4800
9
Functional Description
The FAN4800 consists of an average current con-
trolled, continuous boost Power Factor Correction
(PFC) front end and a synchronized Pulse Width Mod-
ulator(PWM) back end. The PWM can be used in either
current or voltage mode. In voltage mode, feed forward
from the PFC output bus can be used to improve the
PWM’s line regulation. In either mode, the PWM stage
uses conventional trailing edge duty cycle modulation.
This patented leading/trailing edge modulation tech-
nique results in a higher usable PFC error amplifier
bandwidth, and can significantly reduce the size of the
PFC DC bus capacitor.
The synchronization of the PWM with the PFC simpli-
fies the PWM compensation due to the controlled ripple
on the PFC output capacitor (the PWM input capaci-
tor). The PWM section of the FAN4800 runs at the
same frequency as the PFC.
In addition to power factor correction, a number of pro-
tection features are built into the FAN4800. These
include soft-start, PFC over voltage protection, peak
current limiting, brownout protection, duty cycle limit-
ing, and under voltage lockout (UVLO).
Power Factor Correction
Power Factor Correction treats a nonlinear load like a
resistive load to the AC line. For a resistor, the current
drawn from the line is in phase with and proportional to
the line voltage, so the power factor is unity (one). A
common class of nonlinear load is the input of most
power supplies, which use a bridge rectifier and capac-
itive input filter fed from the line.
The peak charging effect, which occurs on the input fil-
ter capacitor in these supplies, causes brief high ampli-
tude pulses of current to flow from the power line, rather
than a sinusoidal current in phase with the line voltage.
Such supplies present a power factor to the line of less
than one(i.e. they cause significant current harmonics of
the power line frequency to appear at their input). If the
input current drawn by such a supply (or any other non-
linear load) can be made to follow the input voltage in
instantaneous amplitude, it will appear resistive to the
To hold the input current draw of a device drawing pow-
er from the AC line in phase with and proportional to the
input voltage, a way must be found to prevent that de-
vice from loading the line except in proportion to the in-
stantaneous line voltage. The PFC section of the
FAN4800 uses a boost mode DC-DC converter to ac-
complish this. The input to the converter is the full wave
rectified AC line voltage. No bulk filtering is applied fol-
lowing the bridge rectifier, so the input voltage to the
boost converter ranges (at twice line frequency) from
zero volts to the peak value of the AC input and back to
zero. By forcing the boost converter to meet two simul-
taneous conditions, it is possible to ensure that the cur-
rent drawn from the power line is proportional to the
input line voltage.
One of these conditions is that the output voltage of the
boost converter must be set higher than the peak value
of the line voltage. A commonly used value is 385VDC,
to allow for a high line of 270VAC
rms.
The second condi-
tion is that the current drawn from the line at any given
instant must be proportional to the line voltage. Estab-
lishing a suitable voltage control loop for the converter,
which in turn drives a current error amplifier, and switch-
ing output driver satisfies the first of these requirements.
The second requirement is met by using the rectified AC
line voltage to modulate the output of the voltage control
loop. Such modulation causes the current error amplifi-
er to command a power stage current that varies direct-
ly with the input voltage. To prevent ripple, which will
necessarily appear at the output of boost circuit (typical-
ly about 10VAC on a 385VDC level), from introducing
distortion back through the voltage error amplifier, the
bandwidth of the voltage loop is deliberately kept low. A
final refinement is to adjust the overall gain of the PFC
section to be proportional to 1/VIN
2
, which linearizes the
transfer function of the system as the AC input voltage
Since the boost converter topology in the FAN4800
PFC is the current averaging type, no slope compensa-
tion is required.
PFC Section
Gain Modulator
Figure 1
shows a block diagram of the PFC section of
the FAN4800. The gain modulator is the heart of the
PFC, as the circuit block controls the response of the
current loop to line voltage waveform and frequency,
RMS line voltage, and PFC output voltages. There are
three inputs to the gain modulator. These are:
1. A current representing the instantaneous input volt-
age (amplitude and wave shape) to the PFC. The recti-
fied AC input sine wave is converted to a proportional
current via a resistor and is then fed into the gain mod-
ulator at I
AC
. Sampling current in this way minimizes
ground noise, as is required in high power switching
power conversion environments. The gain modulator
responds linearly to this current.
2. A voltage proportional to the long term RMS AC line
voltage, derived from the rectified line voltage after
scaling and filtering. This signal is presented to the
gain modulator at V
RMS
. The output of the gain modu-
lator is inversely proportional to V
RMS
2
(except at
unusually low values of V
RMS
where special gain con-
touring takes over, to limit power dissipation of the cir-
cuit components under heavy brownout conditions).
The relationship between V
RMS
and gain is called K,
and is illustrated in the Figure C of the Typical Perfor-
mance Characteristics.
相關PDF資料 |
PDF描述 |
|---|---|
| FAN4803 | 8-Pin PFC and PWM Controller Combo |
| FAN4810 | Power Factor Correction Controller |
| FAN4810M | Power Factor Correction Controller |
| FAN4810MX | Power Factor Correction Controller |
| FAN4810N | Terminal Block RoHS Compliant: Yes |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| FAN4800IN_G | 功能描述:電流型 PWM 控制器 ANG FG PFC & PWM CONTROLLER ASMC DIE RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| FAN4800IN_SB82230 | 功能描述:電流型 PWM 控制器 ANG FG PFC & PWM CONTROLLER ASMC DIE RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| FAN4801 | 制造商:Fairchild 功能描述:CCM PFC + FORWARD PWM IC |
| FAN4801FNY | 制造商:Fairchild Semiconductor Corporation 功能描述: 制造商:Fairchild Semiconductor Corporation 功能描述:NOTEBOOK COMBO |
| FAN4801FNY_SN00170 | 制造商:Fairchild Semiconductor Corporation 功能描述:NOTEBOOK COMBO |
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