UCC28742

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High-Efficiency Flyback controller With Optocoupler Feedback

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Product details

Parameters

Control method Secondary-side regulation Duty cycle (Max) (%) 99 Frequency (Max) (kHz) 105 UVLO thresholds on/off (V) 22/7.7 Features SSR, DCM Operating temperature range (C) -40 to 125 Rating Catalog open-in-new Find other Flyback controllers

Package | Pins | Size

SOT-23 (DBV) 6 5 mm² 2.9 x 1.6 open-in-new Find other Flyback controllers

Features

  • Opto-Coupled Feedback Enables up to 1% Regulation
  • Accurate Current Limit with Overload Timeout Protection and Delayed Hiccup Response
  • Resonant-Ring Valley-Switching Operation for Highest Overall Efficiency
  • 80-kHz Maximum Switching Frequency
  • Frequency Dithering to Ease EMI Compliance
  • Clamped Gate-Drive Output for MOSFET
  • Ultra-Low Start-Up Current and Large VDD Hysteresis
    • High Value Start-Up Resistor
    • Low Bias Capacitance
  • Fault Protections
    • Input Low Line
    • Output Over-Voltage
    • Over-Current
    • Short-Circuit
  • SOT23-6 Package
  • Create a Custom Design Using the UCC28742 with the WEBENCH® Power Designer

All trademarks are the property of their respective owners.

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Description

The UCC28742 off-line flyback controller is a highly integrated, 6-pin secondary-side regulated PWM controller for efficient AC-to-DC power supplies. It is an isolated-flyback power-supply controller that provides Constant-Voltage (CV) using an optical coupler to improve transient response to large-load steps. This device processes information from opto-coupled feedback and an auxiliary flyback winding for high-performance control of output voltage and current.

The UCC28742 employs advanced control algorithms to achieve high operating efficiency and performance. 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 80 kHz and always maintains control of the peak-primary current in the transformer. A minimum switching frequency of 200 Hz facilitates the achievement of low no-load input power.

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Technical documentation

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Type Title Date
* Datasheet UCC28742 High-Efficiency Flyback Controller with Optocoupler Feedback datasheet (Rev. A) May 08, 2018
Application notes Minimize Standby Consumption for UCC287XX Family Aug. 01, 2019
Technical articles Choosing the right flyback controller for your design Aug. 24, 2018
Application notes Selecting Electrolitic Bus Capacitor for Universal Input Jul. 17, 2018
User guides Using the UCC28742EVM-001 (Rev. B) Jun. 06, 2018

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Hardware development

EVALUATION BOARDS Download
document-generic User guide
$99.00
Description

The UCC28742EVM-001 is a 10-W evaluation module for evaluating an off-line adapter for USB applications. The EVM meets CoC tier 2 and DoE Level 6 efficiency and standby power requirements. It is intended for evaluation purposes and is not intended to be an end product. The UCC28742EVM-001 converts (...)

Features
  • Opto-coupled feedback for constant output voltage operation
  • Brick-wall current limit, with +/- 5% accuracy, and timeout delay hiccup, over current protection.
  • Enables +/- 1% output voltage regulation
  • Resonant valley switching for reduced switching losses and high effiency
  • Frequency dithering to reduce (...)

Design tools & simulation

SIMULATION MODELS Download
SLUJ001A.ZIP (840 KB) - SIMPLIS Model
CALCULATION TOOLS Download
SLUC652B.ZIP (301 KB)

Reference designs

REFERENCE DESIGNS Download
12-Watt magnetically resistant quasi-resonant flyback reference design
PMP21462 — This reference design is a quasi-resonant flyback developed to be resistant to large magnetic fields near the transformer. It has a regulated 4 Volt output that can handle up to 2 A of current and secondary 10 V output that can handle 0.4 A.
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
150-VDC - 430-VDC input, multiple output valley-switching flyback reference design
PMP30825 — This 10-W non-isolated flyback reference design uses the UCC28742 controller to generate four outputs (5 V at 150 mA, 12 V at 690 mA, 15 V at 80 mA, 18 V at 20 mA). The controller provides constant-voltage and constant-current regulation. Transistors are used in place of an optocoupler feedback (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
15-W, wide-input flyback reference design
PMP22144 — This reference design uses a UCC28742 flyback controller and an ATL432LI shunt reference to produce an isolated 24-V output capable of 0.625 A from an 85-V to 480-Vac input. All components are placed on one side of the board to reduce complexity and cost. The design can achieve 80% efficiency across (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
60-W, Ultra-wide range power supply reference design
PMP21783 — This reference design provides a 12-Vdc, 5-Vdc, and 3.3-Vdc output from an ultra-wide range of both AC and DC inputs. A universal 85 to 265-Vac input can be applied to the input of the quasi-resonant flyback. For DC inputs ranging from 24 to 150-Vdc, a boost creates a 150-V bus voltage that is fed (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
5-V/2-A, 12-V/2.5-A Dual-output flyback reference design with <50-mW standby power
TIDA-010058 — This reference design is a dual-output flyback converter using secondary-side regulation based on the UCC28742. A 5-V rail is regulated within ±1% precision and a cross regulation of a 12-V rail is within -8% to +14% at 25% to 100% load. The design utilizes a single-layer PCB for cost (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
AC input, 5-V/2-A and 12-V/2.5-A dual-output flyback converter reference design
PMP40508 — This reference design is a 40-W dual-output offline converter using UCC28742, a secondary side regulator. A 5-V rail is regulated to within ±1% precision and cross regulation of 12-V rail is within -8%~+14% at 25% to 100% load. The design adopts a single-layer PCB for cost optimization. The (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
AC Input, 5-V/1-A and 5-V/1-A dual-output flyback reference design
PMP40487 — This design is auxiliary power supply with 5-V/1-A and 5-V/1-A dual output. The line and load regulation of the power supply is designed to be within 1% using the secondary side regulator, UCC28742. The system's reliability is improved through input UVLO and output OVP, OCP, SCP. The four point's (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
AC Input,12-V/5-A and 50-V/1-A dual-output flyback reference design
PMP40467 — This reference design is a 12-V/5-A and 50-V/1-A isolated dual-output auxiliary power supply. Secondary-side regulation improves the line and load regulation using UCC28742. DCM valley-switching operation enable higher efficiency at light load. All components height below 20 mm enable slim TV (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
90-VAC - 265-VAC input, non-isolated flyback reference design with multiple output
PMP30545 — This offline flyback reference design uses the UCC28742 controller to generate a non-isolated output (15 V at 130 mA) and an isolated output (24 V at 830 mA) from an AC input (90 VAC - 265 VAC). The UCC28742 provides a cost effective and precise constant-voltage and constant-current regulation. The (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
25/50 Watt flyback reference design for audio applications
PMP21513 — The quasi-resonant flyback design is a dual output converter with a 24 Volt output and a 6 Volt output. The voltages that are supplied are important for supplying power in audio applications. The design is very low noise for sensitive audio signals with less than 2.5 % voltage ripple on the 24 V (...)
document-generic Schematic document-generic User guide
REFERENCE DESIGNS Download
6-Watt Magnetically Resistant Quasi-Resonant Flyback Reference Design
PMP21458 — This reference design is a quasi-resonant flyback developed to be resistant to large magnetic fields near the transformer. It has a regulated 3.6 Volt output that can handle up to 1 A of current and secondary 12 V output that can handle 0.2 A.
document-generic Schematic document-generic User guide

CAD/CAE symbols

Package Pins Download
SOT-23 (DBV) 6 View options

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