Temperature Detection Circuit with Correlated Current Sources
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Solution Overview
Problem
Existing temperature detection circuits face challenges in accurately adjusting detection temperatures due to manufacturing fluctuations, requiring complex adjustments considering threshold voltages and temperature characteristics of components.
Innovation Solution
A temperature detection circuit incorporating a constant current circuit, a voltage-controlled current circuit, and a current comparator, where the temperature characteristics of both circuits are correlated to minimize manufacturing fluctuations and allow easy adjustment of detection temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a variable resistor is used to adjust detection temperature, then detection temperature can be adjusted, but manufacturing fluctuations cause inaccuracies and complex adjustments are required
Solution Approach 1:
The patent changes the adjustment parameter from resistance value (variable resistor) to transistor threshold voltage (Vth). By controlling Vth through circuit design, the detection temperature can be adjusted without dealing with the complex temperature characteristics of resistors and current sources, thereby improving accuracy while simplifying the adjustment process
Solution Approach 2:
The patent extracts the temperature-dependent parameters (current source temperature characteristics and resistor temperature characteristics) from the adjustment equation. By using a current mirror configuration, these parameters cancel out, leaving only Vth as the determining factor for detection temperature, thus simplifying the adjustment process
2Reliability
If traditional temperature detection circuit is used, then temperature detection function is achieved, but manufacturing fluctuations cause large variations in detection temperature
Solution Approach 1:
The patent implements a current mirror feedback mechanism where the first current source and second current source are coupled through transistors. This feedback structure ensures that temperature characteristics and manufacturing variations in one branch are compensated by the corresponding branch, reducing detection temperature variations
Solution Approach 2:
The patent changes the controlling parameter from multiple factors (current value, resistance, threshold voltage) to primarily threshold voltage Vth. This parameter change reduces the impact of manufacturing fluctuations in current sources and resistors, improving detection temperature consistency
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
This configuration reduces manufacturing-induced variations in detection temperatures, enabling precise and easy adjustment of detection temperatures while providing stable temperature detection with reduced fluctuations.
Implementation Method 1
a voltage generated across the diode 102 decreases, and the absolute value of a threshold voltage (Vth) of the P-channel transistor 111 decreases
Implementation Method 2
temperature characteristics of the constant current circuit and temperature characteristics of the voltage-controlled current circuit have a correlation with each other
Data Source
AI summary
Provided is a temperature detection circuit having less manufacturing fluctuations in detection temperature and capable of easily adjusting the manufacturing fluctuations in detection temperature. The temperature detection circuit includes: a constant current circuit configured to output a constant current; a voltage-controlled current circuit, which is controlled by a voltage output from a heat sensitive element and is configured to output a current corresponding to temperature; and a current comparator configured to compare the constant current and the current corresponding to temperature, and output a detection signal indicating that a predetermined temperature is detected. Temperature characteristics of the constant current circuit and temperature characteristics of the voltage-controlled current circuit have a correlation with each other. The temperature detection circuit is configured to detect temperature based on a result of comparing the output current of the constant current circuit and the output current of the voltage-controlled current circuit.