Bootstrap Switch Circuit for High-Voltage Low-Current Signals
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Solution Overview
Problem
Systems with switch circuits that handle high voltage, low current signals, such as those from weak charge pumps, face challenges in meeting operational requirements due to insufficient current for power sourcing.
Innovation Solution
A boot-strap architecture with a high-gain, positive-feedback loop is implemented using transistors and diodes to control the passing or blocking of high voltage, low current signals, enabling efficient switching and signal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional switch circuit is used to handle high voltage signals, then the circuit can block or pass the signal, but the circuit cannot source sufficient current to meet operational requirements
Solution Approach 1:
The patent introduces a bootstrap capacitor as an intermediary energy storage element between the high voltage signal source and the switching transistor. This capacitor acts as a mediator that temporarily stores energy and provides the additional current needed during switching transitions, enabling the circuit to meet operational current requirements without modifying the original high voltage signal source
Solution Approach 2:
The bootstrap architecture enables the switch circuit to self-generate the necessary voltage and current conditions for operation. The capacitor charges from the high voltage signal when the switch is off, and then automatically discharges to provide the required current when the switch is on, creating a self-sustaining system that requires no external current sourcing components
2Productivity
If transistors are used for switching control, then the circuit can efficiently pass or block signals, but the gate voltage requirements become difficult to meet with available signal levels
Solution Approach 1:
The patent implements a feedback mechanism where the voltage across the bootstrap capacitor is automatically adjusted based on the switching state. When the switch transistor turns on, the capacitor discharges to maintain the gate-source voltage; when off, the capacitor recharges. This feedback loop ensures the transistor remains properly biased throughout the switching cycle, maintaining high switching efficiency while being controllable with available signal levels
Data Source
AI summary
In examples, an apparatus has input and output terminals, and includes a first transistor having a first gate, source, and drain, wherein the first source is coupled to the input terminal, and the first drain is coupled to the output terminal, a second transistor having a second gate, source, and drain, wherein the second gate is coupled to a ground terminal, and the second source is coupled to the first gate, a third transistor having a third gate, source, and drain, wherein the third gate is coupled to an enable terminal, the third source is coupled to the ground terminal, and the third drain is coupled to the second drain, and a fourth transistor having a fourth gate, source, and drain, wherein the fourth gate is coupled to the second drain, the fourth source is coupled to the second source, and the fourth drain is coupled to the input terminal.