The converters operate with variable frequency, which is a function of the load and the instantaneous input / output voltages. The switching frequency is limited between 18kHz and 600kHz. The Pulse Width Modulators (PWM) implement voltage-mode control with input voltage feedforward. When configured for PFC applications, the slow voltage regulation loop results in constant on-time operation within a line cycle. This PWM method, combined with the BCM operation of the boost converters, provides automatic power factor correction. The controllers offers bias UVLO (10V / 7.5V for FAN9611 and 12.5V / 7.5V for FAN9612), input brownout, input over-voltage, over-current, openfeedback, output over-voltage, and redundant latching over-voltage protections. Furthermore, the converters' output power is limited independently of the input RMS voltage. Synchronization between the power stages is maintained under all operating conditions.