UCC28740

ACTIVE

Constant-voltage, constant-current Flyback controller Using Opto-Coupler Feedback

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Product details

Parameters

Control method Secondary-side regulation Duty cycle (Max) (%) 99 Frequency (Max) (kHz) 100 UVLO thresholds on/off (V) 21/7.75 Features SSR, HV Start-up, DCM Operating temperature range (C) -40 to 125 Rating Catalog open-in-new Find other Flyback controllers

Package | Pins | Size

SOIC (D) 7 29 mm² 4.9 x 6 open-in-new Find other Flyback controllers

Features

  • Less than 10-mW No-Load Power Capability
  • Optocoupled Feedback for CV, and
    Primary-Side Regulation (PSR) for CC
  • Enables ±1% Voltage Regulation and ±5% Current Regulation Across Line and Load
  • 700-V Startup Switch
  • 100-kHz Maximum Switching Frequency Enables High-Power-Density Charger Designs
  • Resonant-Ring Valley-Switching Operation for Highest Overall Efficiency
  • Frequency Dithering to Ease EMI Compliance
  • Clamped Gate-Drive Output for MOSFET
  • Overvoltage, Low-Line, and Overcurrent Protection Functions
  • SOIC-7 Package
  • Create a Custom Design Using the UCC28740 With the WEBENCH® Power Designer

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Description

The UCC28740 isolated-flyback power-supply controller provides Constant-Voltage (CV) using an optical coupler to improve transient response to large-load steps. Constant-Current (CC) regulation is accomplished through Primary-Side Regulation (PSR) techniques. This device processes information from opto-coupled feedback and an auxiliary flyback winding for precise high-performance control of output voltage and current.

An internal 700-V startup switch, dynamically controlled operating states, and a tailored modulation profile support ultra-low standby power without sacrificing startup time or output transient response.

Control algorithms in the UCC28740 allow operating efficiencies to meet or exceed applicable standards. The drive output interfaces to a MOSFET power switch. Discontinuous conduction mode (DCM) with valley-switching reduces switching losses. Modulation of switching frequency and primary current-peak amplitude (FM and AM) keeps the conversion efficiency high across the entire load and line ranges.

The controller has a maximum switching frequency of 100 kHz and always maintains control of the peak-primary current in the transformer. Protection features keep primary and secondary component stresses in check. A minimum switching frequency of 170 Hz facilitates the achievement of less than 10-mW no-load power.

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Technical documentation

Design & development

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Hardware development

EVALUATION BOARDS Download
UCC24630 65W AC/DC Adapter
UCC24630EVM-636
document-generic User guide
$99.00
Description

This is a high efficiency 65W AC/DC design using UCC24630 Synchronous Rectification Controller for a Universal input (85Vac to 265Vac) to 19.5V @3.33A output exceeding CoC-5 Tier2 and DOE Level VI performance requirements for external power supplies.

Features
  • 91.49% @115V AC, 89.81% @230V AC 4-point average efficiency 
  • 83.14% @120V AC, 82.24% @230V AC 10% load efficiency
  • 59mW No load Power consumption at 230V AC
  • Fast turn-on time
  • <80mV output voltage ripple
  • AC line input UVLO protection
EVALUATION BOARDS Download
document-generic User guide
$49.00
Description

The UCC28740EVM-525 evaluation module is a 10W off-line discontinuous mode (DCM) flyback converter that provides constant-voltage (CV) and constant-current (CC) output regulation. It uses optical coupler feedback for tight voltage regulation and improved the transient response to large load steps (...)

Features
  • Universal AC input, 5V/2.1A output
  • <20mW no load power
  • Avg. efficiency > 80%
  • Opto-Coupled Feedback for Constant Voltage Regulation and Fast Dynamic Response
  • Primary Side Control for Tight Constant Current Performance (± 5% Output Current Regulation)
  • Internal 700V Start-Up Switch to Start up the Supply (...)

Design tools & simulation

SIMULATION MODELS Download
SLUM672A.ZIP (122 KB) - SIMPLIS Model
CALCULATION TOOLS Download
SLUC487B.ZIP (317 KB)

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Design files
REFERENCE DESIGNS Download
Universal AC Input 5V/2A USB Adaptor with DCM/Valley-Switching and Opto Feedback Reference Design
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