Semiconductor Diode for Internal Overtemperature Detection
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Solution Overview
Problem
Existing temperature detection methods for power transistors rely on external sensors that can be inaccurate due to temperature differences between the sensor and the semiconductor component, and are prone to inertia during rapid temperature changes, which can lead to damage or destruction of the transistor and connected loads.
Innovation Solution
Integrating a diode structure into the semiconductor body, which is fed with a current in its forward direction, allowing for internal temperature measurement and overtemperature detection, enabling accurate and reliable protection of both the power transistor and the temperature sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external temperature sensor is attached to the package or semiconductor body, then the sensor can detect temperature externally, but the sensor only detects external temperature which deviates from internal temperature and has inertia during rapid temperature changes
Solution Approach 1:
The patent merges the temperature sensor with the power transistor by integrating both structures into the same semiconductor body. The sensor structure and power transistor are formed in the same semiconductor substrate, ensuring they experience identical thermal conditions. This eliminates the temperature deviation between sensor and component that plagues external sensors, providing accurate internal temperature measurement without inertia during rapid temperature changes.
Solution Approach 2:
The patent introduces a diode structure as an intermediary temperature sensing element within the semiconductor body. This diode is fed with current in forward direction and its voltage drop serves as the temperature indicator. The diode acts as a mediator that directly senses the internal temperature of the semiconductor body without being affected by external thermal conditions, thereby resolving the contradiction between external accessibility and internal measurement accuracy.
2Power
If a diode structure is integrated into the semiconductor body and fed with current in forward direction, then large signal swing is achieved, but the arrangement requires active switching element to short circuit bulk and source
Solution Approach 1:
The patent employs the power transistor's own bulk-source short circuiting capability to serve the temperature sensing function. The switching element located in the evaluating unit utilizes the existing bulk and source terminals of the power transistor to create the short circuit when required. This self-service approach eliminates the need for additional dedicated short circuiting components, reducing device complexity while maintaining the large signal swing advantage of forward-biased diode operation.
3Reliability
If the evaluating unit and power transistor structure are thermally decoupled, then accuracy and reliability of evaluating unit improve, but the influence of ambient temperature must be considered
Solution Approach 1:
The patent implements thermal decoupling between the evaluating unit and power transistor structure, with the evaluating unit mounted on a heat sink or isolated thermally from the power transistor. This feedback isolation prevents heat generated by the power transistor from affecting the evaluating unit's operation, thereby improving its reliability and accuracy. The system compensates for ambient temperature influences by using the diode's voltage-current characteristics which provide a reliable temperature reference independent of ambient conditions.
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 solution provides a reliable and accurate method for overtemperature detection, reducing the risk of damage to power transistors and loads by directly measuring internal temperatures, and is applicable to various switch types, including n-channel LS and p-channel HS switches, while also considering ambient temperature influences.
Implementation Method 1
The voltage drop across the diode structure is dependent on the temperature of the diode structure and thus on the temperature of the transistor structure
Data Source
AI summary
The invention relates to a circuit arrangement for detecting the overtemperature of a semiconductor body. The arrangement comprises at least one field effect transistor, having a parasitic diode, which is integrated in the semiconductor body, wherein the parasitic diode connects a load terminal of the field effect transistor to a bulk terminal of the semiconductor body, and comprising an evaluating unit electrically connected to the parasitic diode via the bulk terminal at the semiconductor body, which is constructed for feeding a current into the parasitic diode and evaluating a temperature-dependent voltage drop across the parasitic diode, the direction of the current fed into the diode being such that it is operated in the forward direction.