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參數(shù)資料
| 型號(hào)： | UCC18503 |
| 廠商： | Texas Instruments, Inc. |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | BiCMOS PFC/PWM Combination Controller |
| 中文描述： | 的BiCMOS PFC / PWM組合控制器 |
| 文件頁(yè)數(shù)： | 6/8頁(yè) |
| 文件大?。?/td> | 91K |
| 代理商： | UCC18503 |
6
UCC18500/1/2/3
UCC28500/1/2/3
UCC38500/1/2/3
The UCC38500 is designed to incorporate all the control
functions required for a power factor correction circuit
and a second stage dc-dc converter. The PFC function
is implemented as a full feature, average current mode
controller Integrated Circuit for excellent performance. In
addition, the input voltage feedforward function is imple-
mented in a simplified manner. Current from IAC is mir-
rored over to the V
FF
pin. By simply adding a resistor
and capacitor (to attenuate 120Hz ripple) a voltage is de-
veloped which is proportional to line voltage. This elimi-
nates several components normally connected to the
line.
The UCC38500 uses leading edge modulation for the
PFC stage and trailing edge modulation for the dc-dc
stage. This reduces ripple current in the output capacitor
by reducing the overlap in conduction time of the PFC
and dc-dc switches. In addition to the reduced ripple cur-
rent, noise immunity is improved through the current er-
ror amplifier implementation.
The UCC38500 is optimized to control a boost PFC
stage operating in continuous conduction mode, followed
by a dc-dc converter (typically a forward topology). It is
usual that the dc-dc converter is transformer isolated and
therefore its error amplifier will be located on the second-
ary side. The UCC38500 is configured without an inter-
nal error amplifier. The externally generated error signal
is fed into the VERR pin.
The UCC38500 can be configured for voltage mode or
current mode control of the second stage. The applica-
tion figure shows a typical current mode configuration.
For voltage mode control the ramp generated by CT is
simply fed into the ISENSE2 pin.
One of the main system challenges in designing systems
with a PFC front end is coordinating the turn-on and
turn-off on the dc-dc converter. If the dc-dc converter is
allowed to turn on before the boost converter is opera-
tional, it must operate at a much-reduced voltage and
therefore can represent a large current draw to the boost
converter. This start-up sequencing is handled internally
by the UCC38500. The UCC38500 monitors the output
voltage of the PFC converter and holds the dc-dc con-
verter off until the output is within 10% of its regulation
point. Once the trip point is reached the dc-dc section
goes through a soft start sequence for a controlled, low
stress start-up.
Similarly if the output voltage drops too
low (2 voltage options are available) the dc-dc converter
shuts down thereby preventing overstress of the con-
verter.
Design details of the PFC section can be found in several
references shown below.
UCC3817 data sheet
High Power Factor Preregulator for Off-Line Power
Supplies, SEM-800
Optimizing the Design of a High Power Factor
Switching Regulator, SEM-800
A design example for a 2 switch forward converter can be
found in:
250W Off-Line Forward Converter Design Review,
SEM-500
APPLICATION INFORMATION
R
VFF
IAC
VFF
MAX
MAX
2
=
2
0 9
VSENSE:
(voltage amplifier inverting input) This is nor-
mally connected to a compensation network and to the
boost converter output through a divider network.
VREF:
(voltage reference output) VREF is the output of
an accurate 7.5V voltage reference. This output is capa-
ble of delivering 10mA to peripheral circuitry and is inter-
nally short circuit current limited. VREF is disabled and
will remain at 0V when VCC is below the UVLO thresh-
old. Bypass VREF to GND with a 0.1
μ
F or larger ceramic
capacitor for best stability.
PIN DESCRIPTIONS
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| UCC28502 | BiCMOS PFC/PWM Combination Controller |
| UCC1858 | High Efficiency, High Power Factor Preregulator |
| UCC1884 | Frequency Foldback Current Mode PWM Controller |
| UCC2884 | Frequency Foldback Current Mode PWM Controller |
| UCC1888 | Off-line Power Supply Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| UCC1857 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Isolated Boost PFC Preregulator Controller |
| UCC1858 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:High Efficiency, High Power Factor Preregulator |
| UCC1858DW | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Power Factor Controller |
| UCC1858DWTR | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Power Factor Controller |
| UCC1858J | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Power Factor Controller |
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