Offline Pulse-Width Modulation Controller from STMicroelectronics Boosts Efficiency, Economy, and Stability of Ultra-Low Standby Power SuppliesGeneva / 26 Jun 2018
STMicroelectronics’ STCH03 offline Pulse-Width Modulation (PWM) controller combines high integration with accurate constant-current output using primary-side regulation enabling economical mobile chargers, power adapters, or auxiliary supplies to meet stringent eco-design limits for average efficiency and standby power.
At heavier loads, the STCH03 maximizes efficiency by operating in quasi-resonant mode with zero-voltage switching (ZVS) controlled by detecting transformer demagnetization. The detection circuitry also provides for line-voltage feed-forward control, which ensures accurate constant-current regulation. Maintaining operation at the boundary of continuous (CCM) and discontinuous (DCM) transformer current, the STCH03 limits the converter’s maximum operating frequency to 167kHz depending on line/load conditions, and implements valley-skipping for best efficiency as the load reduces.
Energy-saving features including zero-power high-voltage startup circuitry, as well as low quiescent current and burst-mode switching when the load is very low or disconnected, keep standby power below 10mW to help chargers and adapters meet tough legislation such as the incoming CoC Tier 2 power supply efficiency specifications. Low peak current eliminates audible noise at light load or no load, and the STCH03 features an innovative adaptive under-voltage lockout (UVLO) to ensure consistent operation at low values of transformer auxiliary bias voltage.
With the advantage of accurate primary-side constant-current regulation, the STCH03 eliminates output-current sensing components, thereby reducing the charger bill of materials (BOM). The integrated startup circuitry, which consumes zero power when inactive, also saves external components.
The STCH03 contains many more features to help save external components and BOM cost, including over-temperature and over-voltage protection (OTP, OVP) with auto-restart or optional latching operation in the STCH03L variant. In addition, soft-start prevents high peak currents at startup, and output under-voltage protection lets the device operate safely in case of an output short-circuit or low output voltage under constant-current control.
The STCH03 is in production now, in the familiar SO-8 package, priced from $0.54 for orders of 1000 pieces.
For further information please go to www.st.com/stch03
The STM32L5 is based on Arm® Cortex-M33 and TrustZone® technology combined with STMicroelectronics security implementation. On your STM32L562E-DK discovery board, TrustZone is disabled (factory setting) and you can develop as on any other STM32 device. This video shows how to enable TrustZone on STM32L562E-DK discovery using STM32CubeProgrammer and create, compile and debug or run a new project with STM32CubeIDE. It also shows how to open an example project delivered in STM32CubeL5 MCU Package, modify, compile and debug or run it. For further information, you can refer to AN5394 and AN5424 application notes.
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