Buck-Boost Regulator Bypass Control for Smooth Voltage Transition
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Solution Overview
Problem
Buck-boost switching power converters experience inefficiencies and potential component damage due to switching losses and sudden current changes during transitions into and out of bypass mode, particularly when there is a significant voltage difference between input and output voltages.
Innovation Solution
A buck-boost switching power circuit that smoothly transitions into and out of bypass mode by controlling the output voltage through feedback regulation, using the input and output high-side switches to connect the input and output power sources, and employing a bypass control circuit to manage transitions via first and second transition phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the bypass control circuit directly short-circuits the input and output when transitioning into bypass mode, then the conversion efficiency is improved, but the output voltage experiences excessive fluctuation and ringing that can damage components
Solution Approach 1:
The bypass control circuit performs preliminary actions by gradually adjusting the output voltage toward the input voltage before establishing the direct bypass connection. This preparatory voltage adjustment prevents sudden current surges and output voltage fluctuations that would otherwise occur when directly short-circuiting input and output, thereby protecting components while maintaining energy efficiency.
Solution Approach 2:
The patent implements dynamic control of the bypass transition process. Instead of a static direct connection, the output voltage is dynamically adjusted in stages: first gradually changing toward the input voltage, then establishing the bypass connection when the voltage difference is sufficiently small. This dynamic approach eliminates ringing and excessive fluctuations while achieving low-loss bypass operation.
2Loss of energy
If an additional switch is added to enable bypass mode, then the conversion efficiency is improved, but the device complexity increases
Solution Approach 1:
The existing power switches in the buck-boost converter are made multi-functional. The same switches that perform buck-boost conversion also enable the bypass function by adjusting their switching states. The bypass control circuit utilizes the existing switch network to create a direct input-output connection when needed, eliminating the requirement for additional dedicated bypass switches while maintaining energy efficiency.
Solution Approach 2:
The bypass function is merged with the existing power conversion circuitry. The bypass control circuit combines the bypass operation with the existing switch network, using the same transistors and control infrastructure already present in the buck-boost converter. This integration achieves low-loss bypass mode without adding extra switching components.
3Reliability
If the overvoltage protection threshold is increased to prevent erroneous triggering, then the component safety is improved, but the risk of overvoltage damage increases
Solution Approach 1:
The bypass control circuit performs preliminary voltage adjustment before bypass connection is established. By gradually changing the output voltage toward the input voltage and only connecting the bypass when the voltage difference is small, the circuit prevents the output voltage from exceeding safe thresholds. This eliminates the need to raise protection thresholds, maintaining accurate overvoltage protection while enabling safe bypass operation.
Data Source
AI summary
A buck-boost switching power circuit comprises a bypass control circuit which configured to determine whether the buck-boost switching power circuit operates in a bypass mode according to a bypass enable signal. When the conversion voltage difference between the input voltage and the output voltage is less than a reference voltage, the bypass control circuit controls to electrically connect the input power source with the output power source, and operates the buck-boost switching power circuit in the bypass phase of the bypass mode. Before and/or after the bypass phase, the bypass control circuit respectively controls the buck-boost switching power circuit to operate in a first transition phase and/or a second transition phase. During the first transition phase or the second transition phase, the bypass control circuit controls the output voltage to gradually change towards the input voltage or target voltage, until the conversion voltage difference is less than the first reference voltage or the output voltage equals the target voltage.