The NCP4390 is an advanced Pulse Frequency Modulated (PFM)

controller for LLC resonant converters with Synchronous

Rectification (SR) that offers best in class efficiency for isolated

DC/DC converters. It employs a current mode control technique based

on a charge control, where the triangular waveform from the oscillator

is combined with the integrated switch current information to

determine the switching frequency. This provides a better

control−to−output transfer function of the power stage simplifying the

feedback loop design while allowing true input power limit capability.

Closed−loop soft−start prevents saturation of the error amplifier and

allows monotonic rising of the output voltage regardless of load

condition. A dual edge tracking adaptive dead time control minimizes

the body diode conduction time thus maximizing efficiency.

Features

• Secondary Side PFM Controller for LLC Resonant Converter with

Synchronous Rectifier Control

• Charge Current Control for Better Transient Response and Easy

Feedback Loop Design

• Adaptive Synchronous Rectification Control with Dual Edge

Tracking

• Closed Loop Soft−Start for Monotonic Rising Output

• Wide Operating Frequency (39 kHz ~ 690 kHz)

• Green Functions to Improve Light−Load Efficiency

♦ Symmetric PWM Control at Light−Load to Limit the Switching

Frequency while Reducing Switching Losses

♦ Disabling SR at Light−Load Condition

• Protection Functions with Auto−Restart

♦ Over−Current Protection (OCP)

♦ Output Short Protection (OSP)

♦ NON Zero−Voltage Switching Prevention (NZS) by

Compensation Cutback (Frequency Shift)

♦ Power Limit by Compensation Cutback (Frequency Shift)

♦ Overload Protection (OLP) with Programmable Shutdown Delay Time

• Programmable Dead Times for Primary Side Switches and Secondary

Side Synchronous Rectifiers

• VDD Under−Voltage Lockout (UVLO)

• Wide Operating Temperature Range −40°C to +125°C

• This Device is Pb−Free, Halogen Free/BFR Free and is RoHS Compliant

Applications

• Automotive On Board Charger

• Intelligent 100 W−2 kW+ Off−Line & Industrial Power Supplies