Features Low cost power factor correction Power factor greater than 0.99
Few external parts required Control time boost PWM
·Limited peak current for zero current switching ·Minimum and maximum frequency range ·Startup current less than 1mA
·High current FET drive output ·Under voltage lockout

The UC1852 provides a low-cost solution to active power factor corrector (PFC) systems that would otherwise draw peak current pulse lines from the AC mains. This circuit implements zero-current switching boost conversion, producing a sinusoidal input current with minimal external components, while maintaining peak currents well below that of a fully discontinuous converter. The UC1852 provides time-controlled switching to regulate the output, bulk DC voltage, off-time defined by the boost inductor, and zero-current detection circuit re-switching cycles. Even though the switching frequency varies with load and instantaneous line voltage, it can be kept within a reasonable range to minimize noise generation. While allowing higher peak switching currents such as continuous PFC UC1854, this device has smaller external circuitry and less inductance, not yet better than current PFC with discontinuous performance and easy line noise filtering without sacrifice complexity or cost. The ability to obtain more than a power factor of 0.99 makes the UC1852 the best choice for low cost applications in the 50 to 500 watt power range. Protection features of these devices include under-voltage lockout, output clamping, peak current limiting, and maximum frequency clamping. The UC1852 family is available in 8-pin plastic and ceramic dual in-line packages, in an 8-pin Small Outline Integrated Circuit (SOIC). The UC1852 is specified for operation from -55°C to +125°C, the UC2852 is specified for operation from -40°C to +85°C and the UC3852 is specified for operation from 0°C to +70°C.