GENERAL DESCRIPTION

The ML4828 is a complete BiCMOS phase modulation control IC suitable for full bridge soft switching converters. Unlike conventional PWM circuits, the phase modulation technique allows for zero voltage switching (ZVS) transitions and square wave drive across the transformer. The IC modulates the phases of the two sides of the bridge to control output power.
The ML4828 can be operated in either voltage or current mode. Both cycle-by- cycle current limit, integrating fault detection, and soft start reset are provided. The under voltage lockout circuit features a 1.5V hysteresis with a low starting current to allow off-line start up with a bleed resistor. A shutdown function powers down the IC, putting it into a low quiescent state.

FEATURES

■ 5V BiCMOS for low power and high frequency (1MHz) operation
■ Full bridge phase modulation zero voltage switching circuit with independent programmable delay times
■ Current or voltage mode operation capability
■ Cycle-by-cycle current limiting with integrating fault detection and restart delay
■ Can be externally synchronized
■ Four 3Ω CMOS output drivers
■ Under-voltage lockout circuit with 1.5V hysteresis