Bootstrap Circuit Faster Charging High-Voltage Transistor
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Solution Overview
Problem
Existing bootstrap circuits for charging bootstrap capacitors in voltage converters are inefficient in charging time and require larger chip areas for high-voltage transistors, leading to increased costs and size.
Innovation Solution
A bootstrap circuit and method utilizing a charging voltage source, high-voltage transistor, logic control circuit, high-voltage control transistor, cut-off resistor, and control capacitor, where a field-effect transistor replaces the diode to create a higher overdrive voltage charging path, allowing faster charging of the bootstrap capacitor and reducing the size of the high-voltage transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional high-voltage transistor is used to charge the bootstrap capacitor, then the charging path can be formed, but the charging time is long and the transistor size must be large to achieve fast charging
Solution Approach 1:
The patent segments the charging function into two parts: a first high-voltage transistor for fast charging and a second high-voltage transistor for maintaining charge. This segmentation allows the first transistor to be optimized for speed with smaller size, while the second transistor handles the maintenance function, resolving the contradiction between fast charging speed and chip area.
Solution Approach 2:
The patent implements dynamic control by using a control circuit to selectively activate the first high-voltage transistor only during the charging phase, and the second high-voltage transistor during the maintaining phase. This dynamic switching optimizes performance by using the appropriate transistor for each operational phase, achieving fast charging without requiring a continuously large transistor.
2Productivity
If the overdrive voltage of the high-voltage transistor is increased to reduce impedance and fasten charging, then the charging speed improves, but the transistor requires larger voltage headroom and may increase in size
Solution Approach 1:
The patent divides the charging function between two transistors, allowing the first transistor to be optimized for high overdrive voltage and fast charging during the charging phase, while the second transistor handles the maintaining phase. This segmentation enables the first transistor to have higher productivity without permanently increasing overall transistor area.
Solution Approach 2:
The control circuit implements periodic activation of the first high-voltage transistor, turning it on only during the charging phase when high current is needed, and turning it off during the maintaining phase. This periodic action allows the transistor to operate at high efficiency during charging while reducing average power consumption and effective size requirements.
3Speed
If the high-voltage transistor is always on to maintain fast charging capability, then charging speed is maintained, but power consumption increases and charging control becomes imprecise
Solution Approach 1:
The patent uses dynamic control to switch between the first and second high-voltage transistors based on operational phase. The first transistor is activated only during charging when fast speed is needed, and the second transistor takes over for maintaining charge. This dynamic switching maintains charging speed capability while significantly reducing power consumption during the maintaining phase.
Solution Approach 2:
The control circuit implements periodic switching, turning the first high-voltage transistor on during charging phases and off during maintaining phases. This periodic action ensures fast charging speed when needed while minimizing power consumption by keeping the high-current path disconnected during maintenance, preventing continuous energy dissipation.
4Device complexity
If a single high-voltage transistor is used for both charging and maintaining, then the circuit is simpler, but the charging control precision and efficiency decrease
Solution Approach 1:
The patent segments the functions into two specialized transistors: the first for charging and the second for maintaining. This segmentation improves charging efficiency by allowing each transistor to be optimized for its specific function, with the first transistor dedicated to fast charging and the second to stable maintaining, achieving higher productivity despite increased circuit complexity.
Solution Approach 2:
The control circuit acts as an intermediary that manages the switching between the first and second high-voltage transistors. It receives charging commands, activates the appropriate transistor based on operational phase, and ensures precise control of the charging process. This intermediary enables efficient function segmentation while maintaining coordinated operation between the two transistors.
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
The solution achieves faster charging of the bootstrap capacitor with a higher overdrive voltage, reducing the chip area needed for the high-voltage transistor and lowering costs while maintaining charging efficiency.
Implementation Method 1
A bootstrap circuit and method utilizing a charging voltage source, high-voltage transistor, logic control circuit, high-voltage control transistor, cut-off resistor, and control capacitor, where a field-effect transistor replaces the diode to create a higher overdrive voltage charging path
Data Source
AI summary
A bootstrap circuit includes: a charging voltage source; a charging diode, having an anode coupled to the charging voltage source; a high-voltage transistor, having a control terminal defined as a first connecting node and a channel coupled between a cathode of the charging diode and a bootstrap capacitor; a logic control circuit, having a first and a second logic outputs, and a logic input for receiving a charging command; a high-voltage control transistor, having a control terminal defined as a second connecting node and a channel coupled between charging voltage source and the first connecting node; a cut-off resistor, coupled between the first and the second connecting nodes; a charging control transistor, having a channel coupled between the second connecting node and a ground terminal, and a control terminal coupled to the second logic output; a control capacitor, coupled between the first connecting node and the first logic output.