Bridge Driver Current Sensing Bias Circuit for Stable Amplifier Bias
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing current sensing circuits in bridge driver circuits face challenges in providing efficient biasing for amplifiers, leading to high chip area and power consumption, especially in high-voltage and high-current applications, and result in degraded common mode rejection ratio due to varying internal voltages and the use of high-voltage transistors.
Innovation Solution
A novel amplifier bias circuit that generates stable bias voltages without relying on charge-pumped voltages, using a series connection of current sources and resistors to maintain a constant bias across the amplifier, allowing the use of low-voltage transistors and improving common mode rejection ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If charge-pumped voltages are used to bias the amplifier in high-voltage current sensing circuits, then the amplifier can operate across the full output voltage range, but the chip area and power consumption increase significantly
Solution Approach 1:
The patent changes the biasing voltage parameters from charge-pumped high voltages to regulated lower voltages (e.g., 5V and -5V instead of 40V+). This parameter change allows the amplifier to maintain rail-to-rail operation capability while significantly reducing the chip area required for high-voltage transistor implementation and reducing power consumption.
2Adaptability or versatility
If charge-pumped voltages are used to bias the amplifier, then the amplifier can support rail-to-rail operation, but power consumption increases
Solution Approach 1:
The bias circuit automatically regulates its own operating voltages based on the output voltage of the half-bridge driver, eliminating the need for external charge-pumped power sources. The circuit monitors the output voltage and adjusts bias voltages accordingly, maintaining rail-to-rail operation capability while consuming less power through intelligent voltage regulation rather than continuous charge pumping.
3Adaptability or versatility
If high-voltage transistors are used in the amplifier, then the amplifier can operate across the full voltage range, but the common mode rejection ratio degrades
Solution Approach 1:
The patent changes the operating voltage parameters of the amplifier transistors from high-voltage operation to regulated low-voltage operation. By maintaining the amplifier transistors at stable, lower voltages regardless of the half-bridge output voltage, the circuit achieves both full voltage range coverage and improved common mode rejection ratio, as low-voltage transistors exhibit better CMRR characteristics.
4Adaptability or versatility
If the amplifier bias voltage varies with output voltage, then the amplifier can track the output range, but internal voltage variations degrade common mode rejection ratio
Solution Approach 1:
The patent implements dynamic voltage regulation where the bias circuit continuously adjusts the amplifier bias voltages in response to output voltage changes. The bias circuit monitors the half-bridge output voltage and dynamically regulates the amplifier supply voltages to maintain them at stable levels (e.g., ±5V) regardless of the output voltage swing, thereby maintaining both adaptability and measurement precision.
Data Source
AI summary
A load current sensing circuit includes a sense leg including a sense transistor with a gate coupled to the output of a high-side gate driver, a feedback transistor, and a sense resistor coupled in series between a power supply and ground. An amplifier has differential inputs coupled to the sense leg and to an output, and an output coupled to the feedback transistor gate. A bias circuit has a first transistor coupled between the power supply voltage and the first bias voltage terminal, and a gate receiving, from a first leg, a first differential from the output voltage. A second leg in the amplifier bias circuit generates a gate voltage, for a second transistor coupled between ground and a second bias voltage terminal, that is at a second differential from a voltage at the first bias voltage terminal. The amplifier is biased between the first and second bias voltages.