Automotive ultra low standby, flyback controller with integrated HV startup and optocoupler feedback


Product details


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, Low Power, Light Load Efficiency, Error Amplifier, Current Limiting, Green Mode, Input Line Monitor, Leading Edge Blanking Operating temperature range (C) -40 to 125 Rating Automotive TI functional safety category Functional Safety-Capable 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


  • Qualified for automotive applications
  • AEC-Q100 qualified with the following results:
    • Device temperature grade 1: -40.C to +125.C
    • Device HBM classification level 2: ±2 kV
    • Device CDM classification level C4B: ±750 V
  • Funcitonal Safety-Capable
  • Less than 10-mW no-load power capability
  • 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 over current protection functions
  • Create a custom design using the UCC28740-Q1 with the WEBENCH Power Designer

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The UCC28740-Q1 isolated-flyback power-supply controller regulates the output using an optical coupler to provide fast transient response to large-load steps.

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-Q1 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

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Type Title Date
* Datasheet UCC28740-Q1 Ultra Low Standby, Flyback Controller for Automotive, with Integrated HV Startup and Optocoupler Feedback datasheet (Rev. C) Dec. 08, 2020
Application note UCC28740-Q1 Functional Safety, FIT Rate, Failure Mode Distribution and Pin FMA Nov. 11, 2020
Application note Increase Traction Inverter System Robustness With a HV to LV Backup Supply (Rev. B) Oct. 09, 2019
Application note Minimize Standby Consumption for UCC287XX Family Aug. 01, 2019
Application note Agency requirements for stand-by power consumption w/ offline and PoL converters Jan. 26, 2016

Design & development

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

Hardware development


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 (...)

  • 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

SLUM672A.ZIP (122 KB) - SIMPLIS Model
SLUC487B.ZIP (317 KB)

Reference designs

SAE J1772-compliant electric vehicle service equipment reference design for level 1 and 2 EV charger
TIDA-010071 — This reference design highlights an ultra-low standby isolated AC/DC auxiliary power stage followed by converters and linear regulators, a comparator-based control pilot interface to meet the SAE J1772 standard, an  efficient relay and contactor drive and isolated line voltage sensing across (...)
document-generic Schematic

CAD/CAE symbols

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SOIC (D) 7 View options

Ordering & quality

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  • Qualification summary
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