Buck-Boost Bootstrap Circuit for Automatic Capacitor Charging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bootstrap devices for buck-boost converters are inefficient in charging bootstrap capacitors, as they require an external control circuit to periodically pull down the voltage at the source terminal of the transistors before charging can commence.
Innovation Solution
The proposed bootstrap device includes a first and second bootstrap circuit that dynamically determine whether to charge based on the voltage differences among switching voltages, source terminal voltages, and bootstrap voltages, eliminating the need for an external control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an external control circuit is used to periodically pull down the voltage at the source terminal of the transistor, then the bootstrap capacitor can be charged by the linear regulator, but the charging efficiency is poor and the device complexity increases
Solution Approach 1:
The bootstrap device enables the bootstrap capacitor to charge itself automatically by utilizing the voltage difference between the input voltage and output voltage. The charging path is automatically established when the voltage conditions are met, eliminating the need for external control circuits to periodically pull down the source terminal voltage.
Solution Approach 2:
The invention extracts and removes the external control circuit from the system by implementing an automatic charging mechanism within the bootstrap device itself. The charging function is separated from the main control circuitry and handled autonomously by the bootstrap capacitor charging path.
2Reliability
If the voltage at the source terminal is clamped to the output voltage level, then the bootstrap voltage is limited, but an external control circuit is required to restore the bootstrap voltage
Solution Approach 1:
The invention prepares the charging path in advance by designing the bootstrap device structure such that the charging path is automatically activated when the voltage conditions are met. The bootstrap capacitor is ready to charge as soon as the input voltage exceeds the output voltage by the capacitor's voltage, without requiring preliminary external control actions.
Solution Approach 2:
The bootstrap voltage is made dynamic and automatically adjustable based on the voltage difference between input and output. The charging mechanism dynamically responds to voltage conditions, allowing the bootstrap voltage to be restored automatically when needed without fixed external control sequences.
3Reliability
If the linear regulator is used to charge the bootstrap capacitor, then the bootstrap voltage can be maintained, but the charging current is insufficient and charging is delayed
Solution Approach 1:
The charging current is made dynamic by utilizing the voltage difference between input and output voltages. When the voltage difference is large, the charging current is automatically larger, enabling fast charging. When the voltage difference is small, the charging current naturally reduces, preventing overcharging. This dynamic charging mechanism significantly improves charging speed compared to fixed current regulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the bootstrap device to efficiently charge bootstrap capacitors without the need for an external control circuit, improving charging efficiency and reducing the likelihood of charging failures.
Implementation Method 1
The bootstrap capacitor Cbs1 has a first terminal for providing the bootstrap voltage Vbst1... The bootstrap capacitor Cbs2 has a first terminal for providing the bootstrap voltage Vbst2
Data Source
AI summary
A bootstrap device used for first and second transistors of a buck-boost converter includes first and second bootstrap circuits. The first bootstrap circuit generates a first bootstrap voltage, and determines, based on a change among a first switching voltage, a voltage level of a source terminal of the first transistor and the first bootstrap voltage, whether to charge according to at least one of a DC input voltage, a DC output voltage, and a second bootstrap voltage. The second bootstrap circuit generates the second bootstrap voltage, and determines, based on a change among a second switching voltage, a voltage level of a source terminal of the second transistor, and the second bootstrap voltage, whether to charge according to at least one of the DC input voltage, the DC output voltage, and the first bootstrap voltage. The bootstrap device improves charging efficiency of bootstrap capacitors.