Buck-Boost Regulator Bypass Control for Ringing-Free Mode Switching

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Solution Overview

Problem

Conventional buck-boost switching regulators experience excessive ringing when switching from buck-boost mode to bypass mode, leading to component stress and erroneous mode transitions, which can be mitigated by reducing switching loss and adapting the bypass mode operation.

Innovation Solution

A buck-boost switching regulator with a bypass mode is designed to reduce ringing by controlling the bypass switching circuit based on the conversion voltage difference and inductor current, switching to bypass mode only when the inductor current reaches the output current and the conversion voltage difference is less than a reference voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the conventional buck-boost switching regulator switches from buck-boost mode to bypass mode, then the mode transition is achieved, but the inductor current variation becomes very large causing excessive ringing

Engineering Contradiction:

Improvemode transition stabilityVSAvoidringing amplitude

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by checking whether the inductor current reaches the output current before enabling the bypass mode. This pre-condition check ensures that the switching transition occurs at the optimal moment, preventing large current variations and excessive ringing that would otherwise occur during mode transition.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the control parameter from solely voltage-based threshold comparison to a combined parameter that includes both voltage difference and inductor current status. By monitoring both the conversion voltage difference and the inductor current reaching output current, the system achieves smoother transitions with reduced ringing.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the second threshold is increased to the third threshold to prevent false exiting from bypass mode, then the false exiting issue is resolved, but the power conversion efficiency deteriorates

Engineering Contradiction:

Improvebypass mode stabilityVSAvoidpower conversion efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent implements feedback by continuously monitoring the inductor current status and using it to control the bypass mode entry and exit conditions. This feedback mechanism allows the system to make informed decisions about mode transitions, preventing both false exits and unnecessary mode switches that would reduce efficiency.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces dynamic control by making the bypass mode transition dependent on real-time inductor current conditions rather than fixed voltage thresholds alone. This dynamic approach allows the system to adapt to changing load conditions, maintaining stability while optimizing power conversion efficiency.

Inventive Principle:

Principle #15Dynamics

3Object-affected harmful factors

If a low on-resistance bypass switch is used to reduce ringing, then the ringing amplitude is reduced, but the die size and area increase

Engineering Contradiction:

Improveringing amplitudeVSAvoiddie size

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The patent converts the potentially harmful large current variation during mode transition into a beneficial control signal. By monitoring when the inductor current reaches the output current, the system uses this current status as a trigger to optimally switch to bypass mode, thereby reducing ringing without requiring additional hardware components.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent enables the system to self-regulate the bypass mode transition using its existing current sensing capability. The inductor current monitoring that already exists in the buck-boost converter is repurposed to control the bypass mode entry, eliminating the need for additional low on-resistance switches or extra sensing circuits.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12294304B2Buck-boost switching regulator capable of damping out the ringing and control method thereof

Publication Date: 2025.05.06 RICHTEK TECH

AI summary

A buck-boost switching regulator includes: a power switch circuit including an input switch unit and an output switch unit; a bypass control circuit configured to operably generate a bypass control signal according to a conversion voltage difference between an input voltage of an input power and an output voltage of an output power and according to whether an inductor current flowing through an inductor reaches an output current of the output power; and a bypass switch circuit, wherein when the conversion voltage difference is below a reference voltage and when the inductor current flowing through the inductor reaches the output current, the bypass control signal controls the bypass switch circuit to electrically connect the input power with the output power, so that the buck-boost switching regulator operates in a bypass mode.