High Power-Factor Preregulator
●DESCRIPTION
●The UC1852 provides a low-cost solution to active power-factor correction (PFC) for systems that would otherwise draw high peak current pulses from AC power lines. This circuit implements zero-current switched boost conversion, producing sinusoidal input currents with a minimum of external components, while keeping peak current substantially below that of fully-discontinuous converters.
●The UC1852 provides controlled switch on-time to regulate the output bulk DC voltage, an off-time defined by the boost inductor, and a zero-current sensing circuit to reactivate the switch cycle. Even though switching frequency varies with both load and instantaneous line voltage, it can be maintained within a reasonable range to minimize noise generation.
●FEATURES
●• Low-Cost Power Factor Correction
●• Power Factor Greater Than 0.99
●• Few External Parts Required
●• Controlled On-Time Boost PWM
●• Zero-Current Switching
●• Limited Peak Current
●• Min and Max Frequency Limits
●• Starting Current Less Than 1mA
●• High-Current FET Drive Output
●• Under-Voltage Lockout
