Features

• Internally synchronized leading-edge PFC and trailingedge PWM in one IC

• TriFault Detect™ for UL1950 compliance and enhanced safety

• Slew rate enhanced transconductance error amplifier for ultra-fast PFC response

• Low power: 200μA startup current, 5.5mA operating current

• Low total harmonic distortion, high PF

• Reduced ripple current in storage capacitor between PFC and PWM sections

• Average current, continuous boost leading edge PFC

• PWM configurable for current-mode or voltage mode operation

• Current fed gain modulator for improved noise immunity

• Overvoltage and brown-out protection, UVLO, and soft start

General Description

The ML4800 is a controller for power factor corrected, switched mode power supplies. Power Factor Correction (PFC) allows the use of smaller, lower cost bulk capacitors, reduces power line loading and stress on the switching FETs, and results in a power supply that fully complies with IEC1000-3-2 specification. Intended as a BiCMOS version of the industry-standard ML4824, the ML4800 includes circuits for the implementation of leading edge, average current, “boost” type power factor correction and a trailing edge, pulse width modulator (PWM). It also includes a TriFault Detect™ function to help ensure that no unsafe conditions will result from single component failure in the PFC. Gate-drivers with 1A capabilities minimize the need for external driver circuits. Low power requirements improve efficiency and reduce component costs.

An over-voltage comparator shuts down the PFC section in the event of a sudden decrease in load. The PFC section also includes peak current limiting and input voltage brownout protection. The PWM section can be operated in current or voltage mode, at up to 250kHz, and includes an accurate 50% duty cycle limit to prevent transformer saturation.