Active clamp flyback controller is efficient for low no-load power
An integrated active clamp flyback (ACF) controller will reduce the operational and no-load/ standby power consumption of high-efficiency chargers and adapters while driving down component count, bill of materials (BoM) cost and size, says Silanna Semiconductor.
The SZ1131 ACF controller has been added to the family of CO2 Smart Power technologies designed to simplify design, improve performance while addressing environmental sustainability goals through more efficient energy use. The SZ1131 has efficiencies of up to 95 per cent across universal (90 to 265V AC) input voltages and varying loads, with low no-load power of less than 20mW (including USB-PD applications).
Mark Drucker, Silanna Semiconductor’s CEO, said: “Chargers for smartphones and laptops are often left plugged in, even if they are only charging for a few hours at a time.” The AFC is designed to extend efficiency margins against certificate of compliance (CoC), Department of Energy (DoE) and other regulatory requirements and drive down no-load power to optimise efficiency under varying line, load and temperature conditions while minimising so-called ‘vampire’ power or leakage.
The- SZ1131 is targeted at high efficiency and high power density adapters (up to 65W output with universal input and 100W output power with power factor correction (PFC) including single-port and multi-port USB-PD fast chargers. The integrated controller has an adaptive digital PWM controller, a high voltage active clamp FET, active clamp gate driver and start up regulator.
According to Silanna Semiconductor, the ACF controller provides the ease-of-design of a simple flyback controller with the benefits of an ACF design, including recycling the leakage inductance energy of the flyback transformer and limiting the primary FET drain voltage spike during the turn-off events. The SZ1131 uses Silanna Semiconductor’s OptiMode digital control architecture, enabling it to adjust the mode of operation on a cycle-by-cycle basis to maintain high efficiency, low EMI, fast dynamic load regulation, and other power supply parameters in response to varying line voltage and load.
Silanna also offers a 65W USB-PD reference design using the SZ1131 to demonstrate a 30W/inch3 power density (uncased) with around 93 per cent low line (90V AC) and at least 94 per cent high line (230V AC) efficiencies using less expensive components like a conventional RM8 transformer, 100V SR FET, minimal clamp capacitor, and a single common mode choke in the input filter.
Supplied in a 16-pin SOIC package, the SZ1131 offers protection against over-temperature, over-voltage, over-current, over-power and short circuit conditions, and transformer core saturation faults without the need for additional external components.
SZ1131 devices are sampling now with full production scheduled for Q4 2021.
