Flyback Reference Design For 48-V Car Battery

The design is a 48-V to 12-V power supply for automotive systems, with wide input range, transient protection, and high isolation for EV and HEV use.

The TIDA-01344 is a reference design from Texas Instruments (TI). It is a 24-W front-end power supply for 48-V automotive batteries. It provides a 12-V output at 2 A from a wide input range of 10 to 80 V DC, and can handle transients up to 100 V. The system includes EMI filters to meet CISPR-25 standards and a protection circuit to clamp high-voltage transients. A flyback controller with primary-side regulation eliminates the need for an optocoupler. The flyback transformer is designed and tested to meet AEC-Q200 Grade 1 automotive standards. This design is suitable for various automotive applications, including HEV/EV traction inverters, dry double clutch transmissions, electronic control units, and car battery front-end power systems.

The TIDA-01344 TI Design is a 20-W front-end power supply built for 48-V car batteries in hybrid electric vehicle (HEV) and electric vehicle (EV) traction inverter systems. It uses a flyback converter capable of operating across an ultra-wide input range of 10 to 80 V DC and can withstand transients up to 100 V, meeting the requirements of the LV148 automotive standard. The flyback transformer is AEC-Q200 Grade 1 qualified and provides reinforced isolation up to 3.5 kV between the 48-V and 12-V sides. The design eliminates the need for an optocoupler by regulating output voltage from the primary side, improving system reliability and allowing for a more compact board. An integrated compensator in the controller enhances load regulation and transient performance.

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In typical use, the reference design serves as a redundant power supply for the 12-V battery rail in an inverter-driven motor system. It works in an O-ring configuration alongside an isolated DC-DC converter connected to the 48-V battery and a non-isolated DC-DC converter on the 12-V side. This setup ensures continuous power delivery to downstream loads. The design further includes a buck-boost and a buck converter to complete the 12-V front-end power supply, supporting the overall stability and efficiency of the vehicle’s power architecture.

The LM5022-Q1 is a high-voltage, low-side controller for N-channel MOSFETs, supporting a wide input voltage range from 6 V to 60 V. It includes all necessary features for building single-ended power supply topologies using primary-side regulation. The controller uses current-mode control for output voltage regulation, which simplifies loop compensation design and provides natural input voltage feed-forward for improved performance.

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The electrical transient protection circuit is placed at the system’s supply input to guard against positive electrical transients in line with the LV148 standard, aiming to suppress surges while allowing the downstream circuitry to keep operating.

TI has tested this reference design. It comes with a bill of materials (BOM), schematics, assembly drawing, printed circuit board (PCB) layout, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.