Differential Voltage Amplifier Circuit for High-Side Short-Window Sensing
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Solution Overview
Problem
Sensing a voltage signal within a short window of time is challenging, especially in high side sensing on high voltage switching regulators, where duty cycles can be very short, and there is a need for an amplifier with high bandwidth and limited input bias current to sense differential voltages in the presence of common mode voltages.
Innovation Solution
A differential amplification circuit coupled with a resistor and an operative coupling that passes the differential voltage signal component while isolating the common mode voltage component, utilizing capacitors and switches to alternate between integration and transfer phases, maintaining signal fidelity and reducing bias current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional amplifier is used to sense differential voltages in high voltage switching regulators, then the amplifier can handle common mode voltages, but the input bias current is high and bandwidth is limited
Solution Approach 1:
The voltage sensing function is segmented into two independent paths: one for differential voltage sensing with low bias current, and another for common mode voltage sensing. The differential path uses a buffer amplifier with virtual ground that draws minimal bias current from the sensing resistor, while the common mode path separately measures the common mode voltage. This segmentation allows each path to be optimized independently, achieving high measurement precision with reduced power consumption.
Solution Approach 2:
A buffer amplifier with virtual ground is introduced as an intermediary between the sensing resistor and the differential amplifier. This buffer acts as a mediator that provides a low-impedance virtual ground reference, allowing the differential amplifier to accurately sense differential voltages without drawing significant bias current from the sensing resistor. The buffer isolates the high-precision sensing function from the power consumption issues of the amplification function.
2Volume of moving object
If the switching frequency is increased to reduce LC component sizes, then the circuit size is reduced, but the duty cycle window for sensing becomes shorter
Solution Approach 1:
The differential voltage sensing is made continuous rather than periodic. The buffer amplifier with virtual ground continuously tracks the differential voltage across the sensing resistor throughout the entire switching cycle, including during both the ON and OFF states of the switching transistor. This continuous sensing approach maintains full measurement capability even as the duty cycle window narrows with increased switching frequency, eliminating the need to wait for specific phases of the switching cycle.
3Device complexity
If a single-ended amplifier configuration is used, then the circuit is simpler, but it cannot effectively isolate differential signal from common mode voltage
Solution Approach 1:
The voltage sensing function is segmented into two independent paths: one for differential voltage sensing with low bias current, and another for common mode voltage sensing. The differential path uses a buffer amplifier with virtual ground that draws minimal bias current from the sensing resistor, while the common mode path separately measures the common mode voltage. This segmentation allows each path to be optimized independently, achieving high measurement precision with reduced power consumption.
Solution Approach 2:
A buffer amplifier with virtual ground is introduced as an intermediary between the sensing resistor and the differential amplifier. This buffer acts as a mediator that provides a low-impedance virtual ground reference, allowing the differential amplifier to accurately sense differential voltages without drawing significant bias current from the sensing resistor. The buffer isolates the high-precision sensing function from the power consumption issues of the amplification function.
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
Enables effective amplification of differential voltage signals with reduced bias current and high bandwidth, allowing for accurate sensing of differential voltages even in the presence of common mode voltages, suitable for direct current sensing applications.
Implementation Method 1
providing the differential voltage signal component to inputs of a differential amplification circuit by alternately integrating and transferring the differential voltage signal component
Implementation Method 2
An operative coupling between the resistor and the differential amplification circuit to pass a differential voltage signal component of a voltage across the resistor and isolate a common mode voltage signal component of the voltage across the resistor
Implementation Method 3
a differential amplification circuit operatively coupled with the resistor to amplify a differential voltage signal component of a voltage across the resistor
Data Source
AI summary
One or more examples relate to an apparatus to amplify differential voltage signal components of voltage across a resistor. Such an apparatus may include a resistor; a differential amplification circuit operatively coupled with the resistor to amplify a differential voltage signal component of a voltage across the resistor; and an operative coupling between the resistor and the differential amplification circuit to pass the differential voltage signal component and isolate a common mode voltage signal component of the voltage across the resistor.