DESCRIPTION
Integrated totem-pole output circuits enable these ICs to drive the gate of a power MOSFET directly. These ICs can operate synchronously with external pulse, a feature that makes them ideal for power supplies that use a primary-control AC/DC converter to convert commercial AC power to DC, then use one or more DC/DC converters on the secondary side to obtain multiple DC outputs. Synchronization is with the falling edge of the ‘sync’ pulse, which can be the secondary output pulse from a flyback transformer. Synchronization eliminates the beat interference that can arise from different operating frequencies of the AC/DC and DC/DC converters, and reduces harmonic noise. Synchronization with an AC/DC converter using a forward transformer is also possible, by inverting the ‘sync’ pulse. Overcurrent protection features include a pulse-by-pulse current limiter that can reduce the width of individual PWM pulses, and an intermittent operating mode controlled by an on-off timer. Unlik...
Hitachi
