UCC38501DWTR ,BiCMOS PFC/PWM Combination Controllermaximum ratings” may cause permanent damage to the device. These are stress ratings only, andfuncti ..
UCC38501N ,BiCMOS PFC/PWM Combination Controllerelectrical characteristics T = 0°C to 70°C for the UCC3850X, –40°C to 85°C for the UCC2850X,AT = T ..
UCC38501N ,BiCMOS PFC/PWM Combination Controllerfeatures current limiting, a controlled soft-start, presetThe UCC2850x family provides all of the c ..
UCC38502DW ,BiCMOS PFC/PWM Combination Controllerelectrical characteristics T = 0°C to 70°C for the UCC3850X, –40°C to 85°C for the UCC2850X,AT = T ..
UCC38502DW ,BiCMOS PFC/PWM Combination Controllermaximum ratings” may cause permanent damage to the device. These are stress ratings only, andfuncti ..
UCC38502DW ,BiCMOS PFC/PWM Combination Controllermaximum ratings over operating free-air temperature (unless otherwise noted)Supply Voltage VCC . . ..
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UCC38501DW-UCC38501DWTR-UCC38501N
BiCMOS PFC/PWM Combination Controller
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FEATURES Combines PFC and Downstream Converter
Controls Controls Boost Preregulator to Near-Unity
Power Factor Accurate Power Limiting Improved Feedforward Line Regulation Peak Current-Mode Control in Second Stage Programmable Oscillator Leading-Edge/Trailing-Edge Modulation for
Reduced Output Ripple Low Start-up Supply Current Synchronized Second Stage Start-Up, with
Programmable Soft-start Programmable Second Stage Shutdown
DESCRIPTIONThe UCC2850x family provides all of the control
functions necessary for an active power-factor-
corrected preregulator and a second-stage dc-to- dc
converter. The controller achieves near-unity power
factor by shaping the ac input line current waveform to
correspond to the ac input-line voltage using average
current-mode control. The dc-to-dc converter uses
peak current-mode control to perform the step-down
power conversion.
The PFC stage is leading-edge modulated while the
second stage is trailing-edge synchronized to allow for
minimum overlap between the boost and PWM
switches. This reduces ripple current in the bulk-output
capacitor.In order to operate with over three-to-one
range of input-line voltages, a line feedforward (VFF) is
used to keep input power constant with varying input
voltage. Generation of VFF is accomplished using IAC in
conjunction with an external single-pole filter. This not
only reduces external parts count, but also avoids the
use of high-voltage components, offering a lower-cost
solution. The multiplier then divides the line current by
the square of VFF.
The UCC2850x PFC section incorporates a low
offset-voltage amplifier with 7.5-V reference, a
highly-linear multiplier capable of a wide current range,
a high-bandwidth, low offset-current amplifier, with a
novel noise-attenuation configuration, PWM
comparator and latch, and a high-current output driver.
Additional PFC features include over-voltage
protection, zero-power detection to turn off the output
when VAOUT is below 0.33 V and peak current and
power limiting.
The dc-to-dc section relies on an error signal generated
on the secondary-side and processes it by performing
peak current mode control. The dc-to-dc section also
features current limiting, a controlled soft-start, preset
operating range with selectable options, and 50%
maximum duty cycle.
The UCC28500 and UCC28502 have a wide UVLO
threshold (16.5 V/10 V) for bootstrap bias supply
operation. The UCC28501 and UCC28503 are
designed with a narrow UVLO range (10.5 V/10 V) more
suitable for fixed bias operation. The UCC28500 and
UCC28501 have a narrow UVLO threshold for PWM
stage (to allow operation down to 75% of nominal bulk
voltage), while the UCC28502 and UCC38503 are
configured for a much wider operation range for the
PWM stage (down to 50% of bulk nominal voltage).
Available in 20-pin N and DW packages.
