鈥?/div>
Complete 8-pin Power
Factor Solution
Reduced External
Components
RMS Line Voltage
Compensation
Precision
Multiplier/Squarer/Divider
Internal 75kHz
Synchronizable Oscillator
Average Current Mode
PWM Control
Overvoltage Protection
Comparator
High Current, Clamped
Gate Driver
PRELIMINARY
DESCRIPTION
The UC3853 provides simple, yet high performance active power factor correction.
Using the same control technique as the UC1854, this 8-pin device exploits a sim-
plified architecture and an internal oscillator to minimize external component count.
The UC3853 incorporates a precision multiplier/squarer/divider circuit, voltage and
current loop error amplifiers, and a precision voltage reference to implement aver-
age current mode control with RMS line voltage compensation. This control tech-
nique maintains constant loop gain with changes in input voltage, which minimizes
input line current distortion over the worldwide input voltage range.
The internal 75kHz oscillator includes an external clock input, allowing synchroniza-
tion to downstream converters. Additionally, the device features an overvoltage pro-
tection comparator, a clamped MOSFET gate driver which self-biases low during
undervoltage lockout, and low startup and supply current.
These devices are available in 8-pin plastic and ceramic dual in-line (DIP) pack-
ages, and 8-lead small outline (SOIC) packages. The UC1853 is specified for oper-
ation from
鈭?5擄C
to
+125擄C,
the UC2853 is specified for operation from
鈭?0擄C
to
+85擄C,
and the UC3853 is specified for operation from 0擄C to
+70擄C.
BLOCK DIAGRAM
UDG-94120-1
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