Power Transistor Integrated Temperature Sensor Diode
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Solution Overview
Problem
Current power transistors lack an effective method to detect temperature while switched on, particularly in low-side configurations, due to insufficient voltage difference between drain and source potentials, which limits temperature measurement to off-state cooling periods.
Innovation Solution
Incorporating a temperature sensor diode with a pn-junction between an n-doped cathode and p-doped anode zones within the power transistor, allowing for temperature measurement via a voltage drop across the pn-junction, either in a reverse-biased or forward-biased configuration, enabling temperature detection during both on and off states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power transistor is used in low-side configuration with load path connected between negative supply potential and load, then the transistor can switch loads effectively, but the voltage difference between drain and source potentials amounts to only some 100 mV which is not sufficient for reasonably evaluating the temperature signal
Solution Approach 1:
The patent introduces a dedicated temperature sensor diode with pn-junction as an intermediary element for temperature measurement. This separate sensor structure provides a sufficient voltage signal (typically 0.6-0.7V forward voltage) that is independent of the low voltage drop across the power transistor in low-side configuration, enabling accurate temperature evaluation without being constrained by the transistor's operating voltage.
Solution Approach 2:
The patent separates the temperature sensing function from the power switching function by implementing a distinct temperature sensor diode with its own pn-junction. This segmentation allows the temperature measurement circuit to operate independently with adequate signal levels, while the power transistor handles the load switching without compromising temperature detection accuracy.
2Productivity
If the power transistor is switched on to actively switch loads, then the transistor performs its primary function, but temperature measurement cannot be performed because the transistor is heating up and the voltage difference is insufficient
Solution Approach 1:
The dedicated temperature sensor diode acts as an intermediary that can continuously monitor temperature regardless of the power transistor's state. The sensor diode's separate electrical path allows it to provide measurable temperature signals even when the power transistor is fully on and switching loads, eliminating the need to switch off the transistor for temperature measurement.
Solution Approach 2:
The patent enables continuous temperature monitoring throughout the entire operating cycle of the power transistor. The temperature sensor diode provides uninterrupted temperature data during both on-state and off-state, allowing for real-time thermal management without interrupting the load switching operation.
3Device complexity
If the drain-body-diode is used as the temperature sensor element with cathode connected to drain, then the structure is simple, but in low-side configuration the temperature measurement is only available when the power transistor is switched off
Solution Approach 1:
The patent segments the temperature sensing function from the power transistor's main current path by implementing a separate temperature sensor diode. This separate structure with its own pn-junction provides independent temperature measurement capability that is not dependent on the power transistor being off, while maintaining relatively simple device structure.
Solution Approach 2:
The dedicated temperature sensor diode serves as an intermediary element that bridges the gap between the power transistor's operation and temperature measurement requirements. It provides a reliable temperature signal that can be measured independently of the transistor's switching state, overcoming the limitation of using the drain-body-diode in low-side configurations.
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
Enables continuous temperature monitoring of power transistors, preventing damage from excessive heat by allowing for real-time temperature assessment even when the transistor is actively switching loads.
Implementation Method 1
the temperature dependent voltage drop across the pn-junction (18) is detected
Data Source
AI summary
A power transistor has a semiconductor body with a bottom side and top side spaced distant from the bottom side in a vertical direction. The semiconductor body includes a plurality of transistor cells, a source zone of a first conduction type, a body zone of a second conduction type, a drift zone of the first conduction type, a drain zone, and a temperature sensor diode having a pn-junction between an n-doped cathode zone and a p-doped anode zone. The power transistor also has a drain contact terminal on the top side, a source contact terminal on the bottom side, a gate contact terminal, and a temperature sense contact terminal on the top side. Depending on the first and second conduction types the anode or cathode zone is electrically connected to the source contact terminal and the other diode zone is electrically connected to the temperature sense contact terminal.