Temperature Detection Circuit with Dual Current Paths
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Solution Overview
Problem
Temperature detection circuits face challenges in achieving compact size and low power consumption while maintaining accurate temperature sensing and noise rejection.
Innovation Solution
A temperature detection circuit design featuring two current paths, one with a P-type Field Effect Transistor (PFET) and a diode-configured PNP bipolar transistor, where the second transistor's control terminal is coupled to the first current path, allowing for efficient temperature indication with reduced power consumption and space, utilizing a switching capacitor circuit for sampling a reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature detection circuits are used, then temperature sensing accuracy is maintained, but circuit size and power consumption increase
Solution Approach 1:
The patent combines the temperature sensing function with the bandgap reference circuit by sharing the PNP transistor (Q1) and current mirror structures. The PNP transistor serves dual purposes: generating the bandgap reference voltage and providing temperature sensing through its Vbe characteristics, thereby eliminating the need for separate sensing circuitry and reducing overall power consumption.
Solution Approach 2:
The PNP transistor Q1 performs multiple functions simultaneously: it generates the bandgap reference voltage through its Vbe temperature dependence, provides temperature sensing information, and participates in the current mirror operation. This multi-functionality reduces the total component count and power consumption while maintaining sensing accuracy.
2Measurement precision
If conventional temperature detection circuits are used, then temperature sensing accuracy is maintained, but circuit size increases
Solution Approach 1:
The patent merges the temperature sensing path with the bandgap reference generation path by using the same PNP transistor Q1 and shared current mirrors. The sensing node is derived from the same transistor that generates the reference voltage, eliminating redundant components and reducing the overall circuit footprint while maintaining sensing accuracy.
Solution Approach 2:
The temperature sensing function is nested within the bandgap reference circuit structure. The sensing information is extracted from the internal nodes of the reference circuit itself, particularly from the Vbe voltage of the PNP transistor, rather than requiring external or separate sensing elements.
3Reliability
If noise rejection is improved in temperature detection circuits, then measurement reliability increases, but circuit complexity increases
Solution Approach 1:
The patent employs implicit feedback through the current mirror structure that automatically compensates for variations and noise. The current mirrors (Q2-Q3, Q4-Q5) ensure that currents are precisely replicated, and any noise or variation in one branch is reflected and compensated in the other branches, providing natural noise rejection without requiring additional active feedback control circuits.
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 circuit provides a compact and power-efficient temperature detection solution with improved noise rejection and sharp transition characteristics, capable of detecting temperatures within the range of -30 to 85°C, with adjustable detected temperatures by varying reference voltage, transistor size, and emitter biasing currents.
Implementation Method 1
a temperature sensing device... wherein the second transistor is a PNP bipolar transistor configured in a diode configuration
Data Source
AI summary
A temperature detection circuit includes a first current path and a second current path. The first current path includes a first transistor with a control terminal coupled to receive a reference voltage and includes a temperature sensing device. The second current path includes a second transistor with a control terminal coupled to a node of the first current path. The second current path includes a node that provides an indication of a detected temperature.