Chopped Current Mirror Sensing for High-Power Driver Accuracy
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Solution Overview
Problem
High power current drivers face challenges in precise current measurement due to limitations in sensing resistor impedance, leading to restricted maximum deliverable load current, increased system cost and size, and lack of easy gain adjustment, while existing solutions like chopping and offset cancellation techniques do not fully address these issues.
Innovation Solution
A system utilizing a low power transistor as a scaled replica of a high power transistor, with a regulation amplifier, multiplexer, current mirror, and voltage detector, including an ADC and averaging circuit, to measure high power currents by compensating for amplifier regulator errors through a chopping technique, allowing for precise current estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensing resistor is used for current measurement in high power drivers, then current sensing is achieved, but the maximum deliverable load current is restricted due to limited sensing resistor impedance
Solution Approach 1:
The patent creates a scaled replica (copy) of the high power transistor using low power transistors. The replica transistor has identical geometry and is biased at the same voltage, causing it to mirror the drain current of the high power transistor. This allows current measurement without placing a sensing resistor in the high power current path, thus resolving the contradiction between measurement accuracy and maximum deliverable current.
2Measurement precision
If a sensing resistor with higher impedance is used to improve current measurement precision, then measurement accuracy improves, but system cost and size increase
Solution Approach 1:
Instead of using a high impedance sensing resistor that would increase system size and cost, the patent uses a scaled replica transistor that mirrors the high power current. The replica transistor operates at low power levels, allowing the use of small, low-cost components for current measurement while maintaining accuracy.
Solution Approach 2:
The patent replaces the traditional sensing resistor approach (mechanical/electrical component) with an active transistor-based current mirroring system. This substitution allows for more flexible and compact implementation of current measurement functionality.
3Adaptability or versatility
If conventional current sensing methods are used, then current measurement is achieved, but gain adjustment is not easy and measurement precision is limited
Solution Approach 1:
The patent implements dynamic gain adjustment capability by using multiple low power transistors that can be selectively activated. The scaling factor between the replica and high power transistor can be dynamically changed by selecting different transistor combinations, allowing easy gain adjustment while maintaining measurement precision through the current mirroring mechanism.
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 system enables precise control of high power currents by reducing voltage offset errors and allowing for flexible current handling, improving dynamic range and reducing system size and cost by using a low power transistor to mirror high power current, thus enhancing measurement accuracy and adjustability.
Implementation Method 1
A system utilizing a low power transistor as a scaled replica of a high power transistor of a high power driver, with a regulation amplifier, multiplexer, current mirror, and voltage detector, including an ADC and averaging circuit, to measure high power currents by compensating for amplifier regulator errors through a chopping technique
Implementation Method 2
A system utilizing a low power transistor as a scaled replica of a high power transistor of a high power driver, with a regulation amplifier, multiplexer, current mirror, and voltage detector
Implementation Method 3
including an ADC and averaging circuit, to measure high power currents by compensating for amplifier regulator errors through a chopping technique
Data Source
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AI summary
A system for measuring high power currents, including: a low power transistor that is a scaled replica of a high power transistor of a high power driver; a regulator connected to the low power transistor, wherein the regulator is configured to regulate the current flowing through the low power transistor based upon a voltage sensed across the high power transistor and a chop signal; a current mirror with an input connected to the regulator and an output; a current detector having in input configured to receive the chop signal, wherein the current detector is connected to the output of the current mirror and wherein the current detector is configured to measure the current at the output of the current mirror to produce an estimate of the current flowing through the high power transistor.