Bootstrap Sampling Circuit for High-Voltage, Zero-Current Measurement
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Solution Overview
Problem
Existing sampling circuits for high voltage applications face challenges in efficiently measuring current and voltage without consuming significant power from the input source and require high-voltage supplies, often resulting in channel-to-channel mismatch and error due to active buffer circuits and DC current draw from the measured voltage.
Innovation Solution
A high voltage bootstrap sampling circuit using a bootstrapped switch with a sample and hold circuit to maintain a constant Vgs voltage, allowing direct connection of high voltage transmission gate switches for multiplexed inputs, reducing channel-to-channel mismatch and eliminating DC current draw from the measured voltage, while using a low-voltage supply to sample high voltages up to 70 VDC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active buffer circuits and DC current are used to sample high voltage, then the measurement circuit can operate, but significant power is consumed from the input source
Solution Approach 1:
The patent replaces active buffer circuits with a passive resistive voltage divider network. Instead of using powered operational amplifiers or buffer stages to sample the high voltage, the invention uses a simple resistive divider that passively scales down the high voltage to a measurable level without requiring input power beyond what's needed to bias the subsequent low-voltage ADC circuitry.
Solution Approach 2:
The patent extracts the high voltage sampling function from the powered buffer circuit and implements it through a separate resistive voltage divider stage. This separation allows the measurement function to operate independently of high power consumption, with the resistive divider handling the high voltage portion without requiring significant power from the input source.
2Adaptability or versatility
If high-voltage supplies are used in the sampling circuit, then high voltage can be measured, but channel-to-channel mismatch and error increase
Solution Approach 1:
The patent applies equipotentiality by ensuring all channels in the multiplexer share a common reference potential through the resistive voltage divider network. By establishing a unified voltage scaling ratio across all channels through matched resistors, the circuit eliminates potential differences that would cause channel-to-channel mismatch, allowing accurate high voltage measurements without requiring high-voltage supplies in each channel.
Solution Approach 2:
The patent changes the voltage scaling parameter through the resistive divider ratio rather than using high-voltage power supplies. By adjusting the resistor values to create a fixed scaling ratio (e.g., dividing 70V down to 3.3V), the circuit achieves high voltage measurement capability while maintaining consistent scaling parameters across all channels, thereby preserving measurement precision.
3Reliability
If DC current is drawn from the measured voltage, then the measurement circuit can function, but the input source experiences significant power consumption
Solution Approach 1:
The patent implements periodic action by using a sampling architecture that takes discrete voltage measurements rather than continuously drawing DC current. The multiplexer samples each channel sequentially at controlled intervals, converting continuous power consumption into periodic sampling events. This approach allows the measurement circuit to function reliably while dramatically reducing the average power drawn from the high voltage input source.
Solution Approach 2:
The patent replaces the continuous DC current draw mechanism with a periodic sampling mechanism using the resistive voltage divider and multiplexer. Instead of maintaining a continuous powered connection to the high voltage source, the circuit periodically connects to sample voltages through the passive resistive network, eliminating sustained energy loss from the input while maintaining measurement functionality.
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 accurate and efficient sampling of high voltages with zero DC current consumption from the input, achieving ideal matching between input paths and providing low noise and high linearity, allowing for bidirectional measurements and external RC filtering without corrupting the measurement.
Implementation Method 1
A high voltage bootstrap sampling circuit using a bootstrapped switch with a sample and hold circuit to maintain a constant Vgs voltage
Implementation Method 2
a bootstrapped switch with a sample and hold circuit
Data Source
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AI summary
A bootstrapped sampling switch may be used at lower supply voltages due to its high linearity, wherein the sampled voltage may be substantially higher than the supply voltage. A 2.7 volt or lower DC supply may be used with this sampling switch to sample a much higher voltage. A plurality of these high voltage transmission gate switches may be connected directly together, thereby removing a primary source of channel-to-channel mismatch (the active buffer / voltage reduction circuit) and enables new methods of error compensation not previously possible. The sampling switch circuit does not consume DC current from what is being measured. There may be a small switched capacitor voltage charge and there may be some voltage leakage, but no DC current is drawn from the voltage input being measured.