Oxide Semiconductor Protection Circuit for Overvoltage Control
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Solution Overview
Problem
Semiconductor devices capable of wireless communication often receive overvoltages when the communication distance is shorter than expected, leading to potential damage to elements.
Innovation Solution
Incorporating a protection circuit with a control signal generation circuit and a voltage control circuit using a transistor with an oxide semiconductor layer, which adjusts the voltage to prevent damage by controlling the current flow based on the input voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless communication is used to supply power to semiconductor devices, then the devices can be fed at a distance without external power connections, but overvoltage may be input when communication distance is shorter than expected, causing element damage
Solution Approach 1:
The protection circuit is activated in advance to detect voltage levels before they reach dangerous thresholds. The circuit monitors the power supply voltage continuously and prepares to respond by controlling current flow through the transistor, preventing overvoltage damage before it occurs
Solution Approach 2:
The protection circuit uses feedback mechanisms to monitor the power supply voltage and adjust the transistor's gate voltage accordingly. When overvoltage is detected, the feedback loop modifies the gate voltage to control the transistor's conductivity, thereby regulating current flow and protecting the element from voltage spikes
2Reliability
If a protection circuit is added to prevent overvoltage damage, then element reliability is improved, but device complexity increases
Solution Approach 1:
The transistor serves multiple functions: it acts as a switch for current control, a voltage regulator, and a protection mechanism against overvoltage. By making the transistor multi-functional, the circuit achieves protection capabilities without adding numerous separate components, thereby limiting the increase in device complexity
Solution Approach 2:
The gate voltage serves as an intermediary control mechanism between the power supply and the element. By controlling the gate voltage, the circuit indirectly regulates the current flow through the source-drain path, providing a simple and elegant solution that avoids direct complex circuitry between the power supply and protected element
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 effectively prevents element damage by regulating the voltage within a safe range, even when high voltages are input, thereby enhancing the reliability and longevity of semiconductor devices.
Implementation Method 1
In a transistor 122a included in the voltage control circuit 122, a channel formation layer is formed using an oxide semiconductor. The band gap of the oxide semiconductor layer is equal to or more than 2 eV
Data Source
AI summary
To prevent damage on an element even when a voltage high enough to break the element is input. A semiconductor device of the invention operates with a first voltage and includes a protection circuit which changes the value of the first voltage when the absolute value of the first voltage is higher than a reference value. The protection circuit includes: a control signal generation circuit generating a second voltage based on the first voltage and outputting the generated second voltage; and a voltage control circuit. The voltage control circuit includes a transistor which has a source, a drain, and a gate, and which is turned on or off depending on the second voltage input to the gate and thus controls whether the value of the first voltage is changed based on the amount of current flowing between the source and the drain. The transistor also includes an oxide semiconductor layer.