Current Measurement Circuit with Dynamic Proportionality Switching
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Solution Overview
Problem
Current sense transistor circuits face measurement errors at very low currents due to deviations in the proportionality factor K, leading to transient voltage dropouts and inaccurate current measurement, especially in energy-saving modes.
Innovation Solution
A current measurement circuit with a load transistor and a sense transistor, utilizing an analog-to-digital converter and digital-to-analog converter, along with a control circuit that manages switches to adjust the measuring current and output current, allowing for accurate measurement across varying load currents, including low current values without relying on gate-back regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the proportionality factor K is increased to reduce measuring current for high current measurements, then the measuring current becomes too small at low load currents, but measurement accuracy deteriorates at very low currents
Solution Approach 1:
The patent implements dynamic switching between two different proportionality factors (K1 and K2) based on the operating conditions. The control circuit automatically selects the appropriate proportionality factor according to the load current magnitude, transitioning from a first proportionality factor for high currents to a second proportionality factor for low currents, thereby maintaining measurement accuracy across the entire current range
Solution Approach 2:
The patent changes the proportionality factor parameter from a fixed value to a variable that can take different discrete values (K1 and K2). By adjusting this parameter based on the operating mode (first mode for high currents, second mode for low currents), the system optimizes the measuring current magnitude and maintains measurement precision across varying load conditions
2Measurement precision
If gate-back regulation is used to improve measurement accuracy at low currents, then transient voltage dropouts occur during abrupt current rises
Solution Approach 1:
The patent dynamically adjusts the proportionality factor based on the operating mode rather than using static gate-back regulation. The control circuit detects the operating mode and switches between proportionality factors K1 and K2, allowing the system to maintain measurement accuracy at low currents without the harmful effects of gate-back regulation on voltage stability
Solution Approach 2:
The patent introduces a control circuit as an intermediary that manages the switching between different proportionality factors. This control circuit replaces the gate-back regulation mechanism and provides a different approach to maintaining measurement accuracy that does not interfere with the power transistor's voltage stability and transient response
3Device complexity
If a single proportionality factor is used for all current ranges, then the circuit complexity is reduced, but measurement accuracy deteriorates at very low currents
Solution Approach 1:
The patent implements a dynamic multi-mode operation where the proportionality factor changes based on the operating conditions. The control circuit monitors the load current and automatically switches between proportionality factors K1 and K2, achieving high measurement precision across the entire current range while maintaining a relatively simple circuit structure through automated mode detection and switching
Data Source
AI summary
A circuit may include a load transistor and a current measuring circuit that is coupled to the load transistor. The load transistor has a main current path, which is connected between a first supply node and an output pin for connecting a load. The current measuring circuit has a sense transistor coupled to the load transistor. The current measuring circuit is designed to deliver a measuring current that represents a load current flowing through the load transistor. The circuit may also include an analog-to-digital converter with a current input, and a digital-to-analog converter. The analog-to-digital converter is designed to output a digital signal representing an input current of the analog-to-digital converter. The digital-to-analog converter is designed to output an output current that depends on the digital signal. A control circuit is designed to output the measuring current.