The reference design for a BUCK converter features analogue-digital fusion control technology for efficient power supply management.
The control of switching power supply circuits using digital controllers such as DSP (Digital Signal Processor) has been in practical use for over twenty years. However, it has remained confined mainly to fields requiring “switching power supplies with large power and high functionality” and “DC/DC converters needing high-speed response.” In contrast, most commercially available switching power supplies in the 300W range (small to medium power) are still controlled by analogue controllers. This preference is because high-speed, high-performance processors like DSPs consume a lot of power and are expensive, leading to inefficiency and increased costs in low-power applications. To address these issues, ROHM proposes using analogue-digital hybrid control (LogiCoA Controls) in switching power supply designs, which combines the strengths of analogue and digital control while mitigating their respective disadvantages.
LogiCoA001-EVK-001 is a reference design for a BUCK converter that leverages ROHM’s LogiCoA analogue-digital fusion control technology. The design includes the ML62Q2035 microcontroller, optimized for LogiCoA, a 100V gate driver, LDOs, an operational amplifier, and a shunt resistor. The reference design comes with comprehensive design data, sample software, an operating system for power supply control, and a reference board. We invite you to explore the capabilities of the LogiCoA analogue-digital fusion control technology and consider its application in your future power supply device development projects.
The MCU ML62Q2035 is mounted as a power supply controller in this design. The MCU’s VDD voltage is supplied from the control block power supply Vcc5V. Once the supplied voltage exceeds the 4.10V threshold voltage of the Power-On Reset (POR), the microcontroller initiates its startup sequence, and the RMOS begins its operation.
The design features a pulse-by-pulse Over Current Protection (OCP) function. The drain current of the low-side FET is monitored by an analogue comparator in the drain current detection block. When the current exceeds the 6.0A detection threshold, the protection mechanism activates, turning off the FET. After detection, the DC-DC converter automatically restarts from protection mode. However, the OCP will be detected again if the overload condition persists.
The LogiCoA MCU features operational timers with 10 outputs, can control up to 10 power devices, and is optimized for generating gate drive signals. It includes three analogue comparator channels for PWM signal generation, overcurrent protection circuits, and two D/A converter channels that can be used as reference voltage signals. The operational timer is designed for flexible configurations, allowing settings for “inter-timer coordination operation,” “timer-comparator coordination operation,” “timer-external inter-signal coordination operation,” and “phase tracking operation.” This flexibility enables the control of various power supply circuit topologies, including Buck, Boost, Buck-Boost, forward, bridges, PWM flyback, quasi-resonant flyback, boundary current mode PFC, and interleaved PFC.
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.
