ML4800 Fairchild Semiconductor, ML4800 Datasheet - Page 7

• Manufacturer Part Number: ML4800
• Description: The ML4800 is a controller for power factor corrected, switched mode power supplies
• Manufacturer: Fairchild Semiconductor

PRODUCT SPECIFICATION
Functional Description
Power Factor Correction
REV. 1.0.5 9/25/01
PFC Section
Gain Modulator
1.
2.
3.
A current representing the instantaneous input voltage
(amplitude and waveshape) to the PFC. The rectified
AC input sine wave is converted to a proportional
current via a resistor and is then fed into the gain
modulator at I
minimizes ground noise, as is required in high power
switching power conversion environments. The gain
modulator responds linearly to this current.
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
inversely proportional to V
low values of V
over, to limit power dissipation of the circuit
components under heavy brownout conditions). The
relationship between V
illustrated in the Typical Performance Characteristics.
The output of the voltage error amplifier, VEAO. The
gain modulator responds linearly to variations in this
voltage.
AC
RMS
RMS
. Sampling current in this way
. The gain modulator s output is
where special gain contouring takes
RMS
RMS
and gain is called K, and is
2
(except at unusually
ML4800
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