Current Mirror Monitor for Wide-Band Envelope Tracking Control
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Solution Overview
Problem
Current monitors for controlling switching stages of modulator systems face challenges in accurately measuring AC- and DC-currents with high potential differences across a wide frequency bandwidth, as existing solutions either rely heavily on potential differences or have limited frequency bandwidth.
Innovation Solution
A current monitor comprising a resistive sensing element and a current mirror circuit with a constant current source, where the current in the second branch is independent of potential differences, allowing for a voltage signal independent of these differences, and using semiconductor devices like PNP transistors to achieve a wide frequency bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a simple current mirror is used for current sensing, then the frequency bandwidth is wide, but the output signal strongly depends on the potential difference between the current measuring point and ground
Solution Approach 1:
The current sensing function is divided into two independent branches: the first branch senses the current and generates the output signal, while the second branch with constant current source compensates for potential difference effects. This segmentation allows each branch to perform its specific function optimally without interference from potential difference variations.
Solution Approach 2:
The constant current source in the second branch acts as an intermediary that compensates for the effects of potential difference variations. By maintaining a stable current in the second branch, it serves as a reference that counteracts the potential difference dependency in the first branch, enabling accurate current sensing independent of voltage variations.
2Measurement precision
If a Wilson current mirror is used for current sensing, then the output signal is independent from potential difference, but the frequency bandwidth is low
Solution Approach 1:
The Wilson current mirror structure is segmented into two separate branches with distinct functions. The first branch is optimized for wide bandwidth current sensing, while the second branch with constant current source provides potential difference compensation. This segmentation allows the system to achieve both wide bandwidth and potential difference independence simultaneously.
Solution Approach 2:
The invention merges the advantages of simple current mirrors (wide bandwidth) with the advantages of Wilson current mirrors (potential difference independence) by combining them into a unified two-branch structure. The first branch provides wide bandwidth response while the second branch provides stability against potential difference variations, achieving both goals together.
3Speed
If a current monitor with wide frequency bandwidth is used for AC- and DC-current measurement, then high frequency components can be measured, but the measurement becomes dependent on potential difference
Solution Approach 1:
The constant current source serves as an intermediary element that stabilizes the measurement against potential difference variations. By maintaining a fixed current in the second branch, it compensates for voltage fluctuations that would otherwise affect the accuracy of AC- and DC-current measurements in the first branch, ensuring reliable measurements across wide frequency ranges.
Solution Approach 2:
The invention changes the operating parameters of the current monitor by introducing a constant current source that fixes the current in the second branch independent of voltage variations. This parameter stabilization allows the system to maintain accurate measurements of both AC and DC components across wide frequency bandwidths without being affected by potential difference changes.
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 provides a simple, cost-effective method for controlling switching stages by ensuring the output voltage signal is independent of potential differences and maintaining a wide frequency bandwidth, suitable for high-frequency AC-component measurement and high current applications.
Implementation Method 1
a current mirror circuit comprising a first semiconductor device and a second semiconductor device, both semiconductor devices electrically interconnected with each other for copying the current in the second semiconductor device to the first semiconductor device
Implementation Method 2
a resistive sensing element in a section of said current path
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a current monitor (10) for sensing the current in a current path (12), said current monitor (10) comprising a resistive sensing element (24) in a section (26) of said current path (12) and a current mirror circuit (28) comprising a first semiconductor device (30) and a second semiconductor device (32), both semiconductor devices (30, 32) electrically interconnected with each other for copying the current in the second semiconductor device (32) to the first semiconductor device (30), wherein the first semiconductor device (30) is electrically connected to an electric reference potential and to a current input side of the section (26) via a resistive equivalence element (38) in a first current branch (34) and wherein the second semiconductor device (32) is electrically connected to the electric reference potential and to a current output side of the section (26) in a second current branch (36). The current monitor (10) further comprises a constant current source (44) for keeping the current in the second current branch (36) independent from the potential difference between the potential of the current output side of the section (26) and the reference potential. The invention further relates to a corresponding control device for being integrated in a modulator in large bandwidth applications.