Current Mode-Controlled DC-DC Regulators (Part 1): A Review Of Small-Signal Behavior

Focus:

With simple operation and dynamics, current-mode control (CMC) requires two loops: a wide- bandwidth inner current loop and an outer voltage regulation loop. Common forms of CMC include peak, valley, average, hysteretic, constant on-time, constant off-time and emulated. Each offers certain advantages and tradeoffs depending on design requirements. This part one of a multipart series represents an update to a previous series the author wrote in 2014 with more focus on the inner current loop. Recent works by Basso and Feucht are cited along with those of Sheehan and Ridley in analyzing loop operation. It begins with an overview of the small-signal behavior in fixed-frequency, naturally sampled, peak current-mode, pulse-width modulated (PWM) dc-dc regulators. This part one lays the groundwork for implementation of a CC-CV circuit with two loops using a shared network for compensation.

What you’ll learn:

• How to understand the advantages and disadvantages of the different forms of current-mode control
• How to understand operation of peak and valley current mode architectures
• How to understand small-signal behavior of current-mode-controlled regulator through analysis of the two control loops

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Author & Publication:

Timothy Hegarty, Texas Instruments, Phoenix, Ariz., How2Power Today, Nov 15 2024

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