Protection Circuit Variable Resistance Voltage Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor devices face damage due to high voltages applied to their external terminals when no power-supply voltage is supplied, leading to ineffective protection of circuits like input buffers during operations such as inserting a memory card into a digital camera.
Innovation Solution
A protection circuit is introduced, comprising a control circuit and a voltage limitation circuit with a variable resistance unit that adjusts its resistance value based on generated control voltages, ensuring the voltage at external terminals is limited to prevent damage when power-supply voltage is not available.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional protection circuit is used, then the circuit can protect against high voltage when power-supply voltage is supplied, but the protection circuit does not work effectively when no power-supply voltage is supplied
Solution Approach 1:
The patent applies the dynamics principle by making the resistance value of the protection circuit variable rather than fixed. The resistance value changes dynamically based on the input voltage level and power-supply voltage status. When no power-supply voltage is supplied and high input voltage is detected, the resistance decreases to provide effective protection. When power-supply voltage is supplied, the resistance increases to normal operating levels, allowing normal circuit operation. This dynamic adaptation resolves the contradiction between protection effectiveness and operational versatility.
Solution Approach 2:
The patent applies the parameter changes principle by changing the resistance parameter of the protection circuit based on operating conditions. The control circuit monitors the power-supply voltage and input voltage, and adjusts the resistance value accordingly. When VDD is not supplied and Vin exceeds a threshold, the resistance is reduced to provide protection. This parameter change enables the circuit to adapt to different operational conditions, resolving the contradiction between effective protection and broad adaptability.
2Object-affected harmful factors
If the resistance value is reduced to limit voltage effectively, then voltage protection improves, but current consumption increases during normal operation
Solution Approach 1:
The patent uses the dynamics principle to make the resistance value variable rather than fixed. During normal operation when power-supply voltage is supplied, the resistance is maintained at a higher value to minimize current consumption. When high voltage damage risk is detected (no power-supply voltage and high input voltage), the resistance dynamically decreases to provide effective voltage limitation. This dynamic adjustment resolves the contradiction between voltage protection effectiveness and power consumption.
Solution Approach 2:
The patent applies parameter changes by adjusting the resistance parameter based on the operational state. The control circuit detects whether power-supply voltage is supplied and adjusts the resistance accordingly. When VDD is present, resistance is high to reduce power consumption. When VDD is absent and Vin is high, resistance is reduced to limit voltage and protect the circuit. This parameter adaptation resolves the contradiction between protection effectiveness and energy loss.
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 protection circuit effectively limits voltages at external terminals, preventing damage to semiconductor devices by adjusting resistance values according to input voltages, thus safeguarding against high voltage exposure even without the primary power-supply voltage.
Implementation Method 1
a variable resistance unit having a resistance value that changes according to the control voltage
Data Source
AI summary
A protection circuit includes a control circuit coupled to a first power-supply wire applied with a first power-supply voltage. The control circuit generates a control voltage in accordance with the first power-supply voltage and an input voltage. A voltage limitation circuit is coupled between a first node applied with the input voltage and a second power-supply wire applied with a second power-supply voltage. The voltage limitation circuit includes a variable resistance unit having a resistance value that changes according to the control voltage. When the first power-supply voltage is not supplied to the protection circuit and the input voltage is larger than a first voltage, the control circuit generates the control voltage such that the resistance value of the variable resistance unit is smaller than that in a case where the input voltage is equal to or less than the first voltage.