Buck-Boost Regulator Bypass Mode Reduces Switching Loss
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Solution Overview
Problem
Conventional single input multiple output buck-boost switching regulators experience high switching loss and low power conversion efficiency when the input voltage is close to the low dropout voltage, leading to inefficient operation.
Innovation Solution
A buck-boost switching regulator with a bypass mode is introduced, where a bypass control circuit generates a bypass control signal based on the conversion voltage difference between the input voltage and the low dropout voltage, allowing the input voltage to be directly connected to the low dropout node when the difference is below a reference voltage, thereby reducing switching loss and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional buck-boost switching regulator operation is used when input voltage is close to low dropout voltage, then the regulator can maintain voltage conversion capability, but switching loss increases and power conversion efficiency decreases
Solution Approach 1:
The regulator dynamically switches between buck-boost mode and bypass mode based on the voltage difference between input voltage and low dropout voltage. When the voltage difference is small (below threshold), the system transitions to bypass mode to eliminate switching loss. When the voltage difference is large, the system operates in buck-boost mode to maintain voltage conversion capability. This dynamic operation resolves the contradiction by adapting the operating mode to real-time voltage conditions.
Solution Approach 2:
The invention extracts the voltage conversion function from the buck-boost switching regulator when the input voltage is close to the low dropout voltage. By removing the switching conversion path and directly connecting the input voltage to the low dropout regulator through the bypass switch, the harmful switching loss is eliminated while the voltage regulation function is maintained through the low dropout regulator alone.
2Productivity
If bypass mode is activated to reduce switching loss, then energy efficiency improves, but the voltage conversion capability for large voltage differences is reduced
Solution Approach 1:
The system dynamically adjusts its operating mode based on voltage conditions. The control circuit continuously monitors the voltage difference between VIN and VLDO, and automatically switches between bypass mode (for small voltage differences) and buck-boost mode (for large voltage differences). This dynamic adaptation ensures both high efficiency and full voltage conversion capability are maintained as needed.
Solution Approach 2:
The regulator is designed with multi-functionality to operate in three distinct modes: bypass mode for direct voltage passage, buck mode for voltage step-down, and boost mode for voltage step-up. The bypass switch and buck-boost circuit work together to provide universal voltage conversion capability across different operating conditions, resolving the contradiction between efficiency and adaptability.
3Loss of energy
If bypass switch is added to enable direct connection, then switching loss is reduced and efficiency is improved, but device complexity increases
Solution Approach 1:
The bypass switch is integrated with the existing low dropout regulator and buck-boost circuit components. The control circuit merges the bypass mode control with the existing buck-boost mode control logic, using the same voltage sensing and control mechanisms. This merging approach minimizes the increase in device complexity while achieving the goal of reducing switching loss.
Data Source
AI summary
A buck-boost switching regulator includes: a power switch circuit including an input switch unit and an output switch unit which switch a first terminal and a second terminal of an inductor for buck-boost conversion; at least one low dropout regulator correspondingly coupled to at least one output high side switch in the output switch unit to correspondingly convert at least one low dropout voltage into at least one output voltage; and a bypass control circuit configured to operably generate a bypass control signal according to a conversion voltage difference between the input voltage and the corresponding low dropout voltage; wherein when the corresponding conversion voltage difference is lower than a reference voltage, the bypass control signal controls a corresponding bypass switch to electrically connect the input voltage with the corresponding low dropout node.