Coulomb Counter Using Oxide Semiconductor for Charge Accuracy
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Solution Overview
Problem
Existing semiconductor devices for determining the amount of electric charge, such as coulomb counters, face challenges in accuracy and error reduction due to fluctuations in voltage during the holding operation, which affects the determination of electric charge in batteries.
Innovation Solution
A semiconductor device incorporating a coulomb counter with a cumulative addition circuit that includes a transistor and capacitor to sample and hold current, using an oxide semiconductor with low leakage current to minimize errors, and a hysteresis comparator for noise immunity, allowing precise determination of electric charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional transistors are used in the cumulative addition circuit, then the device complexity is reduced, but the measurement precision of electric charge deteriorates due to leakage current
Solution Approach 1:
The patent changes the material parameter of the transistor from conventional semiconductor to oxide semiconductor, which fundamentally alters the electrical characteristics. This material substitution reduces leakage current by several orders of magnitude, directly improving measurement precision without requiring additional circuit complexity
Solution Approach 2:
The patent employs a hybrid circuit architecture combining oxide semiconductor transistors for the cumulative addition circuit with conventional semiconductor transistors for other functions. This composite approach isolates the precision-critical section to where low leakage is essential, while maintaining overall device simplicity in non-critical areas
2Reliability
If the holding operation is performed without low leakage current components, then the device complexity is reduced, but the reliability of electric charge determination deteriorates due to voltage fluctuations
Solution Approach 1:
The patent changes the key parameter of transistor leakage current from conventional levels (nA range) to ultra-low levels (fA range) by using oxide semiconductor material. This parameter change stabilizes the held voltage throughout the holding operation, preventing drift and ensuring reliable electric charge determination
Solution Approach 2:
The oxide semiconductor transistor acts as an intermediary component between the capacitor and the rest of the circuit. It mediates the charge transfer process with minimal leakage, ensuring that the capacitor holds its charge accurately without requiring complex voltage stabilization circuits
3Measurement precision
If conventional transistors with higher leakage current are used, then the ease of manufacture is improved, but the measurement precision of electric charge deteriorates
Solution Approach 1:
The patent changes the material composition parameter of the transistor channel from conventional silicon-based semiconductor to oxide semiconductor. This material parameter change inherently provides ultra-low leakage current characteristics, improving measurement precision while the manufacturing process has been adapted to incorporate oxide semiconductor layers through established thin-film deposition techniques
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 semiconductor device achieves high accuracy in determining electric charge with reduced errors by using an oxide semiconductor with low leakage current and noise-immune signal generation, enhancing the reliability of power management systems.
Implementation Method 1
both the sixth transistor and the seventh transistor are transistors whose channel is formed in an oxide semiconductor film
Implementation Method 2
a first capacitor that has a first terminal to which the second current is input
Implementation Method 3
a hysteresis comparator for noise immunity
Data Source
AI summary
A coulomb counter is provided. In the coulomb counter, a current generated on charge or discharge of a secondary battery is converted into a voltage by a resistor, and the voltage is amplified by an amplifier circuit. The voltage amplified by the amplifier circuit is converted into a current by a voltage-current converter circuit, and the current is input to a cumulative addition circuit. The cumulative addition circuit charges a capacitor with the current input from the voltage-current converter circuit and generates a signal corresponding to a voltage generated across the capacitor. One terminal of the capacitor is connected to an output of the voltage-current converter circuit through a switch, and the other terminal of the capacitor is supplied with a constant potential. By on/off of the switch, supply of electric charge to the capacitor and storage of the electric charge can be controlled.