Bootstrap Switch Circuit for Low-Noise High-Voltage Signal Control
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Solution Overview
Problem
Circuits face challenges in meeting competing operational requirements such as high voltage signals, noise sensitivity, and bandwidth limitations, particularly in systems like medical devices where noise can adversely affect operation.
Innovation Solution
A boot-strap architecture is employed to charge switching elements, harvesting signal current for maintaining charge at the control terminal and using diodes and capacitors to manage voltage peaks and frequency ranges, ensuring noise is limited while passing or blocking signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a switch circuit is used to pass or block signals, then signal control capability is improved, but noise generation increases and reliability deteriorates
Solution Approach 1:
The patent introduces a bootstrap capacitor as an intermediary energy storage element between the power supply and the switch control terminal. This capacitor acts as a local energy reservoir that provides the necessary voltage for switch operation without directly connecting the high-voltage signal path to the control logic, thereby isolating noise and preventing it from propagating through the circuit while maintaining full signal control capability.
Solution Approach 2:
The bootstrap circuit is self-sustaining, using a portion of the input signal current to recharge the bootstrap capacitor during the switch's operation cycle. This self-service mechanism eliminates the need for external high-voltage power supplies or additional energy sources, allowing the switch to maintain full signal control capability while the internal bootstrap capacitor continuously suppresses noise generation.
2Adaptability or versatility
If the circuit operates with high voltage signals exceeding supply voltage, then signal handling capability is improved, but device complexity increases
Solution Approach 1:
The bootstrap capacitor serves as a voltage intermediary, accumulating energy from the input signal and delivering it to the switch control terminal. This single capacitor enables the circuit to handle high voltage signals that exceed the main power supply voltage without requiring multiple power supplies, voltage dividers, or complex isolation circuits, thereby maintaining simple circuit topology while achieving superior signal handling capability.
Solution Approach 2:
The bootstrap capacitor dynamically changes its voltage parameter during operation, charging to a voltage level that is the sum of the power supply voltage and the input signal voltage. This dynamic parameter change allows the switch control terminal to achieve the necessary voltage levels for high-voltage signal handling while the rest of the circuit continues to operate at the lower power supply voltage, avoiding the need for complex high-voltage circuitry throughout the entire system.
3Adaptability or versatility
If bandwidth is extended to cover wide frequency ranges, then signal processing capability is improved, but noise sensitivity increases
Solution Approach 1:
The bootstrap capacitor acts as a frequency-independent energy intermediary that maintains stable voltage at the switch control terminal across the entire frequency spectrum from DC to high frequencies. By providing local energy storage and release, it decouples the wide bandwidth signal path from the power supply, preventing noise from entering the signal path while maintaining full signal processing capability across all frequency ranges.
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 enables the passage or blocking of signals with peak-to-peak voltages exceeding supply voltage, supports wide frequency ranges from 0.01 Hz to 25 MHz, and minimizes noise generation, thus enhancing system reliability and performance.
Implementation Method 1
The first capacitor has a first terminal coupled to a voltage terminal, and having a second terminal. The second capacitor has a first terminal coupled to the second terminal of the first capacitor, and having a second terminal coupled to the second terminal of the first transistor
Implementation Method 2
The first diode has a first anode and a first cathode, the first anode is coupled to the second terminal of the first capacitor, and the first cathode is coupled to the input of the shutoff circuit
Data Source
AI summary
In some examples, an apparatus includes a switch circuit, a charge circuit, and a shutoff circuit. The switch circuit is configured to control passage of a data signal having a frequency of less than about 10 kilohertz (kHz) from an input terminal to an output terminal, the switch circuit having a control terminal. The charge circuit is coupled to a voltage supply and the switch circuit, wherein the charge circuit is configured to harvest a portion of current flowing through the switch circuit between the input terminal and the output terminal to maintain a charge at the control terminal greater than a programmed amount in a first state of operation and prevent charge from leaking from the control terminal. The shutoff circuit is coupled to the switch circuit and configured to discharge the charge at the control terminal in a second state of operation.