General Description
The ML4818 is a complete phase modulation control IC suitable for full bridge soft switching converters. Unlike conventional PWM circuits, the phase modulation technique allows for zero-voltage switching 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 ML4818 can be operated in current mode. The delay times for the outputs are externally programmable to allow the zero-voltage switching transitions to take place.
Pulse-by-pulse current limit, integrating fault detection, and soft start reset are provided. The under-voltage lockout circuit features a 6V hysteresis with a low starting current to allow off-line start up with a low power bleed resistor. A shutdown function powers down the IC, putting it into a low quiescent state.

FEATUREs
• Full bridge phase modulation zero voltage switching circuit with programmable ZV transition times
• Constant frequency operation to 500kHz
• Current mode operation
• Cycle-by-cycle current limiting with integrating fault detection and restart delay
• Precision buffered 5V reference (+1%)
• Four 1.5A peak current totem-pole output drivers
• Under-voltage lockout circuit with 6V hysteresis
• Power DIP package