Isolated DC/DC converters reduce size of gate driver power supplies
To reduce the size of gate driver power supplies for xEV applications such as electric compressors and PTC heaters in electric vehicles (EVs), Rohm Semiconductor has introduced the BD7Fx05EFJ-C isolated flyback DC/DC converters. The BD7F105EFJ-C and BD7F205EFJ-C are optimised for gate driver power supplies in xEV applications such as electric compressors and PTC heaters.
xEVs such as hybrid and electric vehicles primarily use electricity as the energy source and are equipped with electric compressors for air conditioning and PTC heaters to raise the interior temperature.These applications are driven by high voltages making it necessary to isolate the primary circuit that includes the battery from the secondary circuit comprised of the motor and other systems to ensure safety. Conventional isolated circuit configurations require considerable noise countermeasures for switching frequencies that vary with output current as well as a larger mounting area.
The BD7Fx05EFJ-C isolated flyback DC/DC converters’ circuit configuration achieves stable switching frequency characteristics without requiring a photocoupler, which decreases the application size and also the workload for noise design countermeasure. Rohm’s analogue design technology allows the BD7Fx05EFJ-C to eliminate the need for photocouplers, transformer auxiliary windings, and peripheral components which are conventionally needed to detect secondary side voltage and current. The company has also focused on miniaturisation and has reduced the number of components required for current detection by 10 (equivalent to a board area of 30 per cent) compared to general isolated flyback power supply circuits.
The BD7Fx05EFJ-C is also equipped with an adaptive on-time control function that fixes the switching on time, ensuring a stable frequency of around 350kHz regardless of output power. Compliance with the CISPR25 automotive EMC standard requires noise design in the range of 150kHz to 300kHz, but these converters do not fall within this band, which means that noise countermeasures can be greatly simplified, said Rohm. This, together with a spread spectrum function that minimises radiated noise, contributes to reducing the number of efforts for noise design.
Rohm claimed that the BD7Fx05EFJ-C improves application reliability by incorporating multiple protection circuits along with a function that stabilises the output voltage.
As well as automotive applications, such as electric compressors, PTC heaters and inverters, the devices are suitable for industrial applications, such as power supplies, PLCs (programable logic controllers) and inverters.
