6 Summary

When designing a HV-LV redundant flyback power supply, careful consideration is required for selecting high voltage automotive qualified devices, minimizing standby power losses and noise coupling, and ensuring the system meets safety requirements. For high-voltage power device selection, Silicon MOSFETs are typically acceptable for 400-V systems. However, Silicon Carbide MOSFETs are typically used in 800-V systems due to their higher voltage rating (typically 900 V or greater). External or internal start-up circuitry can be used to minimize standby power consumption. A high current sense voltage rating provides additional robustness against false CS pin triggering in a noisy environment. Primary-side regulated feedback does not require an optocoupler which increases system reliability and eliminates a component crossing the isolation barrier.

The evaluation module UCC28c56EVM-066 shows a 40 V to 1 kV input HV to LV redundant power supply solution. The UCC28781EVM-053 50-500 V_in flyback reference design also illustrates a potential solution for this application. Table 7-1 covers the differences between TI’s automotive flyback solutions.