Southchip Semiconductor Technology(Shanghai)Co.,Ltd. (ASX: 688484) has recently introduced a high-efficiency platform solution designed for medium to high-power AC-DC power supplies. The core of this platform consists of the SC3270 multi-mode PFC and current-mode LLC digital combo controller, along with the SC3530/SC3531 LLC synchronous rectification controllers. This solution addresses a relatively complete main power chain within AC-DC power supplies, where the front-end PFC improves the power factor and handles voltage boosting, the LLC handles high-frequency isolation and energy conversion, and synchronous rectification reduces secondary-side rectification losses. By co-optimizing these three critical stages, the solution can be applied to products such as AI computing terminals, industrial power supplies, communication power supplies, and high-performance adapters.
For AI equipment and industrial power supplies with continuously increasing power demands, power supply design must focus not only on output power but also on conversion efficiency, thermal management, protection capabilities, and future platform reusability. The PFC+LLC+SR platform launched by Southchip is specifically developed to meet these requirements.
SC3270 Integrates PFC and LLC Control, Reducing Peripheral Circuitry
The SC3270 is a digital combo controller that integrates PFC and LLC control functions, allowing for parameter configuration via a UART interface. The chip integrates high-voltage power supply and drive functions internally, which can reduce the number of some peripheral components, supporting highly integrated AC-DC power supply designs. For the PFC stage, the SC3270 employs a peak current control architecture and obtains switching current information through MOSFET current sensing. Compared to traditional methods that sense inductor current, this design reduces losses in the sensing path and helps improve the thermal performance of the sense resistor. To accommodate different input voltages and load conditions, the SC3270 supports multiple operating modes including CCM, QR, and DCM. In essence, the chip can switch to a more suitable control mode based on actual operating conditions, balancing light-load efficiency, full-load ripple, power factor, and system temperature rise. This is particularly important for industrial or communication power supply platforms covering multiple power ranges. Manufacturers can adapt the same controller to different product specifications by adjusting parameters and peripheral configurations, thereby shortening development cycles.
For the LLC control portion, a key feature of the SC3270 is the reduction of the external resonant voltage detection branch. Traditional current-mode LLC solutions typically require an additional resonant voltage sampling network to obtain the resonant voltage information needed for control. The SC3270 can synthesize the resonant voltage internally based on current information, eliminating the need for one external sampling branch. The value of this design lies not only in reducing component count but also in simplifying PCB layout and lowering the design difficulty of high-frequency, high-voltage sampling networks. For high-power-density power supplies, a more streamlined peripheral circuit makes layout, EMI control, and production consistency easier to manage. Furthermore, the SC3270 utilizes the saved pin resources for independent secondary over-voltage and under-voltage protection. This protection can form a redundant monitoring mechanism with the main feedback loop, providing additional safeguards in cases of feedback anomalies, output abnormalities, or control failures, thereby enhancing the overall safety and reliability of the system.
SC3530/SC3531 Reduce Secondary-Side Rectification Losses
In LLC power supplies, the efficiency of secondary-side rectification also directly impacts overall system temperature rise and conversion efficiency. The SC3530 and SC3531 introduced by Southchip are synchronous rectification controllers tailored for medium to high-power LLC power supplies. Traditional rectification schemes often use Schottky diodes, but in high-current output scenarios, the forward voltage drop of diodes leads to significant conduction losses. The SC3530/SC3531 drive low on-resistance MOSFETs for synchronous rectification, which can further reduce this portion of the loss. Both chips support dual-channel driving and nanosecond-level fast turn-off, enabling more precise synchronous rectification control under different loads and reducing the risk of energy backflow. For AI computing equipment, communication power supplies, and industrial power supplies that operate under sustained high loads, this type of design helps lower thermal losses and improves overall system efficiency and long-term operational stability.
Platform Summary and Industry Impact
Through the combination of the SC3270 with the SC3530/SC3531, Southchip has further enhanced its AC-DC front-end power supply product portfolio. Currently, AI computing equipment and industrial power supplies are continuously evolving towards higher efficiency, higher power density, and greater reliability. The PFC+LLC+SR platform launched by Southchip coordinates the configuration of the three key power stages—PFC, LLC, and synchronous rectification—and optimizes aspects such as peripheral simplification, digital configurability, and protection mechanisms. This provides a new solution option for the platform-based design of medium to high-power AC-DC power supplies.
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