QR Method Isolated Power Supply Reference Design

The design offers a 20V output with advanced power management, efficient QR operation, and comprehensive safety features, suitable for high-demand devices.

An isolated 90W 20V 4.5A power supply is essential for safely and reliably powering a range of high-performance devices. By isolating the input and output, it ensures electrical safety and protects sensitive equipment from interference, noise, and potential faults. This stability is crucial in applications like industrial control systems, communication equipment, and medical devices, where consistent power delivery and user safety are priorities. Additionally, the isolation helps prevent issues like ground loops, which can introduce noise in audio and communication systems. Overall, such a power supply is valued for delivering clean, stable power across diverse, demanding applications. The evaluation board from ROHM provides an isolated 20V output from an input range of 90 to 264 Vac, with a maximum output current of 4.5 A.

The BM1Q104FJ, a QR controller designed for AC/DC power supplies, ensures an efficient solution for any product that requires a direct connection to an outlet. Applications for this evaluation board include a variety of devices such as printers, AC adapters, copy machines, and other equipment requiring efficient, isolated power conversion.

– Advertisement –

The evaluation board includes a range of advanced features designed for efficient and safe power management. It operates with a Quasi-Resonant (QR) method, optimizing performance and energy efficiency. A built-in 650V starter circuit provides robust starting capability, and low power consumption is maintained even during light load conditions. Additionally, bottom skip control and a transformer sound reduction function help improve both efficiency and user experience.

For safety and protection, the board includes multiple safeguards. The VCC pin is equipped with under-voltage protection, and there is cycle-by-cycle over-current protection to prevent excessive current. High voltage protection is built into the output pin, and a soft-start function helps manage power-up smoothly. Additional protective features include a ZT trigger mask function, ZT over-voltage protection, FB overload protection with auto-restart, and CS pin open protection with auto-restart, all of which contribute to reliable and stable operation.

– Advertisement –

The quasi-resonant AC/DC converter IC designed for products with electrical outlets, offering efficient soft switching that reduces EMI. With external MOSFETs for switching and current detection resistors, it allows for flexible design. Its high-voltage tolerant starter circuit supports low power consumption and rapid startup, while its low standby current and burst operation at light loads minimize standby power use.

The IC adapts its switching cycles to match load demands and includes a sound suppression feature to reduce transformer noise in burst mode. Built-in safety features like soft-start, burst mode, cycle-by-cycle over-current limiting, overload and overvoltage protections, and CS open protection provide reliable and secure operation.

ROHM 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.