L4985/L4986 CCM PFC Controllers

STMicroelectronics' L4985A/B and L4986A/B four device family are peak current-mode PFC controllers for boost converters with a proprietary multiplier emulator, which, in addition to the innovative THD optimizers, guarantee very low total harmonic distortion (THD) performance in all operating conditions. The devices offer a high-performance low-component count solution for CCM-operated boost PFC pre-regulators in EN61000-3-2 and JEIDA-MITI compliant applications in a power range that spans from a few hundred W to some kW. Thanks to a proprietary off-time modulator, the devices operate in quasi-fixed frequency in all operating conditions. They are available in a 65 kHz option for A and 130 kHz for B.

The 800 V high voltage start-up block includes the circuitry to discharge the X-capacitors of the EMI filter to a safe level. This allows the units to meet safety regulations such as IEC 61010-1 or IEC 62368-1 without using the traditional discharge resistor in parallel to the X-capacitors. The devices feature low consumption and disable functions, allowing usage in applications that must comply with the latest energy saving requirements issued by Energy Star [a joint program of the Environmental Protection Agency (EPA) and the Department of Energy (DoE) in the United States], the European Code of Conduct, the European Union’s Ecodesign Directive, and other guidelines. The L4985A/B come in SO8 package, while the L4986A/B come in SSOP10.

In addition to overvoltage protection that keeps the output voltage under control during transient conditions, the IC also protects against feedback loop failures or incorrect settings and boosts inductor saturation. The brownout protection function allows the design of medical equipment according to the latest regulations driven by IEC 60601-1-2, which requires the output regulation in case of mains dips lasting up to 500 msec. Soft-start limits the peak current. For the L4986A/B only, the PG_IN is an adjustable input comparator suitable for monitoring the PFC output voltage and driving a logic signal exiting from PG_OUT pin accordingly.