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Rohm has released hybrid analogue-digital controlled design for a 24V 4A output mains PSU built around its ML62Q2035 16bit RISC MCU.

The design, called REF67004 and implemented on the LogiCoA003-EVK-001 evaluation board, incorporates a critical conduction mode PFC (power factor correction) stage followed by an isolated quasi-resonant fly-back converter.

“Analog-controlled power supplies are widely used in small to medium-power industrial applications, however, demand for higher reliability and more precise control have made it increasingly difficult for analogue-only configurations to meet market expectations,” said Rohm. “On the other hand, while fully digital power supplies offer fine control and greater flexibility, their adoption in the small to medium power range has been limited due to the high cost and power consumption. To overcome these challenges, Rohm has developed a hybrid approach that integrates the advantages of both analog and digital control.”

Features include a calibration function that compensates for variations in component characteristics, allowing “for reduced design margins, making it possible to select more compact power devices and inductors”, claimed the company, which is providing a power-supply-centric real-time operating system for the microcontrollers (diagram right).

The MCU has built-in non-volatile data flash and can store information including input voltage, output voltage, current, temperature, pre-shutdown system status and cumulative operating time.

This can be retreived through a PC via a UART, which also allows control parameters to be configured.

Find the design on this Rohm web page

The microcontroller used is one of four that Rohm has introduced for power supplies controlled by both analogue and digital loops.

All share the same 16bit 16MHz RISC CPU core from Lapis, and they have 16 or 32kbyte of programme flash plus 2kbyte of ram

Added to this is 4kbyte of data flash eraseable in 128byte blocks – read more about their features here.