Matched-Diode Overvoltage Clamp Circuit for Accurate Protection
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Solution Overview
Problem
Existing protection circuits suffer from low operation accuracy due to process variation and temperature characteristics, particularly when external components are used, leading to increased costs and a compromised dynamic range for the to-be-protected circuit, and require a power supply voltage higher than the protection voltage.
Innovation Solution
A protection circuit design that includes a current path unit, a reference voltage generation unit, and an amplifier circuit, where the reference voltage is generated based on the operating characteristics of the current path unit elements, allowing for a protection voltage set higher than the power supply voltage and adjustable, with components selected to minimize process and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a protection circuit is configured by external components, then the protection voltage can be set, but the external components have process variation different from that of elements forming the protection circuit and thus the temperature characteristics are not stable, and the operation accuracy is significantly lowered
Solution Approach 1:
The patent uses diode elements that are formed in the same semiconductor substrate as the amplifier circuit, ensuring they have identical process characteristics and temperature dependencies. This homogeneity eliminates the mismatch between external components and integrated elements, maintaining stable temperature characteristics and high operation accuracy while enabling protection voltage setting through the number of diode stages.
2Adaptability or versatility
If the clamp circuit sets the positive and negative clamp voltages by using the string configuration in which the diode elements are simply connected in series, then the clamp voltages can be set, but the clamp voltages tend to depend on process variation and temperature characteristics of the diode elements, and therefore, the operation accuracy is insufficient
Solution Approach 1:
The patent introduces a feedback mechanism where the voltage across the diode string is fed back to the amplifier circuit, which adjusts the current through the diodes to maintain a precise reference voltage. This feedback loop compensates for process variation and temperature drift, achieving high operation accuracy while maintaining the ability to set clamp voltages by adjusting the number of diode stages.
3Reliability
If operation accuracy of a protection circuit is low due to influence of process variation and temperature characteristics, then it is necessary to set a level of protection voltage in such a way as to compensate for this, but there is a problem that a dynamic range of a to-be-protected circuit is sacrificed
Solution Approach 1:
The patent achieves high accuracy protection by changing the parameter of using matched diode elements with identical process and temperature characteristics, rather than compensating for variations. This allows setting the protection voltage precisely at the required level without needing to add excessive margin, thereby preserving the full dynamic range of the to-be-protected circuit while ensuring reliable protection.
4Ease of operation
If the clamp circuit requires a power supply voltage equal to or higher than the protection voltage in its operation, then the circuit can operate, but the protection voltage cannot be set higher than the power supply voltage
Solution Approach 1:
The patent uses a current mirror circuit as an intermediary to generate the required current for the diode string based on a reference current. This current mirror mechanism allows the protection circuit to achieve the necessary voltage levels without requiring the power supply voltage to be equal to or higher than the protection voltage, enabling flexible setting of protection voltages beyond the power supply constraint.
Data Source
AI summary
There is provided a to-be-protection circuit that is high in operation accuracy and that prevents overvoltage on a protected circuit. A protection circuit is configured to protect a to-be-protected circuit from overvoltage. The to-be-protected circuit is connected to an external output terminal. The protection circuit includes: a current path unit connected to the external output terminal and including at least one first element; a reference voltage generation unit which generates and outputs a reference voltage; and an amplifier circuit outputs a target voltage based on a difference between a first input voltage and a second input voltage. The amplifier circuit operates using the reference voltage as the first input voltage and using a feedback voltage based on the target voltage as the second input voltage, and outputs the target voltage to the current path unit. The reference voltage generation unit includes at least one second element having an operating characteristic corresponding to an operating characteristic of the at least one first element of the current path unit, and generates the reference voltage based on a voltage drop caused by the at least one second element.