Flyback DC/DC converters cut board area by 30%

Rohm Semiconductor has introduced the BD7Fx05EFJ-C isolated flyback DC/DC converters that are optimized for gate drive power supplies in xEV applications, including electric compressors and PTC heaters.

Rohm explained that xEVs such as electric and hybrid vehicles have unique applications such as the electric compressors for AC and PTC heaters to raise cabin temperature. And, because they are driven by high voltages, the primary circuit that includes the battery must be isolated from the secondary circuit that includes the motor and other systems. In addition, large mounting area requirements, power consumption and conventional isolated circuitry requires noise countermeasures for switching frequencies that vary with output current.

(Source: Rohm Semiconductor)

Rohm’s new isolated flyback DC/DC converters features a circuit configuration delivering stable switching frequency characteristics without a photocoupler. This configuration minimizes size and the workload necessary when using noise design countermeasures.  Rohm’s analog technology also allows for the elimination of transformer auxiliary windings and peripheral components normally used to detect secondary-side voltage and current. The resulting solution uses 10 fewer components for current detection, which is equivalent to a board area of 30% compared to general isolated flyback power supply circuits.

The BD7Fx05EFJ-C also features an adaptive ON-time control function that enables fast load response and a stable frequency of approximately 350 kHz regardless of output power. The CISPR25 EMC standard typically requires noise design in the frequency range from 150 kHz to 300 kHz. The new converters fall outside of this band, so that noise countermeasures are greatly simplified. A spread spectrum function further minimizes radiated noise. The device also improves application reliability by incorporating multiple protection circuits and output voltage stabilization.

These isolated flyback DC/DC converters also can be used in industrial applications such as power supplies, programmable logic controllers and inverters.

The BD7F105EFJ-CE2 and BD7F205EFJ-CE2 flyback DC/DC converters are currently available, along with two evaluation boards – the BD7F105EFJ-EVK-001 and BD7F205EFJ-EVK-001. They can be purchased through Rohm’s online distributors, including Digi-Key, Mouser and Farnell.