Geneva, June 26, 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.
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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.
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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.
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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.
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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.
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The STCH03 is in production now, in the familiar SO-8 package, priced from $0.54 for orders of 1000 pieces.
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For further information please go to www.st.com/stch03
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