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reference designFAN7688

Onsemi FAN7688

Advanced Secondary Side LLC Resonant Advanced Secondary Side LLC Resonant Rectifier Control

Overview

TopologyPower Factor Correction
Input voltage400 V
Switching frequency36-735 kHz
Output 112.5 V / 20 A
IC revision1.3

Description

The FAN7688 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 ControlCharge Current Control for Better Transient Response and Easy Feedback Loop DesignAdaptive Synchronous Rectification Control with Dual Edge TrackingClosed Loop Soft-Start for Monotonic Rising OutputWide 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 ConditionProtection 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 - Over-Temperature Protection (OTP)Programmable Dead Times for Primary Side Switches and Secondary Side Synchronous RectifiersVDD Under-Voltage Lockout (UVLO)Wide Operating Temperature Range -40°C to +125°C

Typical applications

  • Intelligent 100w-power supplies
  • large screen display power
  • Desktop ATX,Desktop-derived server,Blade server
  • Industrial power
  • High Efficiency Associated DC-DC converter

More information

Products

Order Code
Data­sheet
Downloads
Status
Product series
VIN
VOut1(V)
IOut1(A)
Vaux(V)
L(µH)
fswitch(kHz)
n
LS(µH)
ISAT(A)
RDC 1(mΩ)
RDC 2(mΩ)
RDC 3(mΩ)
RDC 4(mΩ)
Size
Mount
Samples
760895731
WE-LLCR Resonant Converter, 360 - 400 V (DC), 12 V
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Status Activei| Production is active. Expected lifetime: >10 years.
Product seriesWE-LLCR Resonant Converter
Input Voltage 360 - 400 V (DC)
Output Voltage 112 V
Output Current 120.8 A
Auxiliary Voltage18 V
Inductance475 µH
Switching Frequency 70 - 120
Turns Ratio35:2:2:3 
Leakage Inductance100 µH
Saturation Current5 A
DC Resistance 1128 mΩ
DC Resistance 24 mΩ
DC Resistance 34 mΩ
DC Resistance 4192 mΩ
SizeETD44 
MountTHT