Over-current Detection Circuit Using Temperature Compensation
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Solution Overview
Problem
Conventional over-current protection circuits for switching elements, such as IGBTs, require operational amplifiers, increasing costs and space requirements due to their use of detection voltage and reference voltage comparisons.
Innovation Solution
An over-current detecting apparatus that eliminates the operational amplifier by using a comparator circuit, a current converting element, and resistors to convert temperature voltage into current, allowing for temperature characteristic revision without the need for an operational amplifier, thereby reducing costs and space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an operational amplifier is used for accurate over-current detection, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the essential function of the operational amplifier (voltage comparison) and implements it using simpler components: a comparator circuit, current converting element, and resistors. This removes the complex operational amplifier while maintaining the core detection functionality through a simplified circuit architecture.
Solution Approach 2:
The patent replaces the expensive operational amplifier with cheaper components (comparator, current converting element, resistors) that can achieve the same detection function. This substitution reduces overall device cost while maintaining detection accuracy through proper circuit design.
2Measurement precision
If an operational amplifier is used for over-current detection, then measurement precision is improved, but the area occupied increases
Solution Approach 1:
The patent removes the operational amplifier component and its associated support circuitry, replacing it with a more compact arrangement of simpler components. This extraction reduces the physical footprint while maintaining the essential detection capability through the comparator-based circuit.
3Measurement precision
If an operational amplifier is used for over-current detection, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent substitutes the expensive operational amplifier with cheaper alternative components (comparator, current converting element, resistors) that can be manufactured at lower cost. This component substitution directly reduces manufacturing expenses while achieving equivalent detection performance through proper circuit design.
4Device complexity
If temperature characteristics are not compensated, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent introduces a temperature detecting element and current converting element as intermediary components that measure temperature and convert it to a compensating current. This mediator circuit adjusts the reference voltage based on temperature variations, thereby compensating for temperature effects and maintaining detection accuracy without requiring a complex operational amplifier.
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 results in a more cost-effective and compact over-current detecting apparatus that is independent of temperature, effectively detecting over-current conditions without relying on operational amplifiers, thus reducing overall costs and space requirements.
Implementation Method 1
The current converting element converts a voltage of a temperature detecting element that detects a temperature of the switching element into a current corresponding to the voltage of the temperature detecting element
Implementation Method 2
using a resistor to convert the current into a voltage. In other words, the current converting element is used to convert a voltage value of a temperature detecting element having a temperature characteristic into a corresponding current value
Data Source
AI summary
An over-current detecting apparatus for a switching element includes a reference power source, a comparator circuit, a current converting element, a first resistor, and a second resistor. The comparator circuit includes a first input terminal that receives a voltage corresponding to a current flowing in the switching element and a second input terminal that receives a reference voltage supplied from the reference power source. The current converting element converts a voltage of a temperature detecting element (4) that detects a temperature of the switching element into a current corresponding to the voltage of the temperature detecting element. The first resistor is connected in series to a reference power supply side of the second input terminal of the comparator circuit. The second resistor is connected in series to a ground side of the second input terminal of the comparator circuit.