4.7 Average Current Mode Control vs Peak Current Mode Control

Two popular approaches for implementing current loops are Average Current Mode Control (ACMC) and Peak Current Mode Control (PCMC), each offering distinct advantages and some limitations.

ACMC requires simpler peripheral setup and is highly compatible with Droop mode control. Additionally, it provides precise control over PWM edge positions, which provides more flexibility towards achieving maximum efficiency. In well-designed systems, the switch timings of each bridge are synchronized, making ACMC a straightforward approach to control.

PCMC requires less CPU computations resulting in faster control loop execution.

ACMC and PCMC also differ in their management of transformer magnetizing current and current regulation. PCMC achieves transformer volt-second balance after multiple cycles during a transient, whereas ACMC maintains balanced magnetization in the transformer by enforcing equal on-times. PCMC requires precise current sensing due to its reliance on current values, while ACMC is more tolerant to imperfections in current sensing.

In this design, Average Current Mode Control is chosen because of its advantages when compared to Peak Current Mode Control. The dsPIC33CK microcontroller is optimized for Switch-Mode Power Supply (SMPS) applications, making the additional computational demands imposed by ACMC manageable. Since ACMC works well with Droop mode control, it is an excellent choice for this application.