Power Semiconductor Gate-Voltage Sensing for Fast Temperature Control
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Solution Overview
Problem
Existing temperature monitoring systems for semiconductor switching elements, such as NTC sensors on a carrier plate or heat sink, suffer from thermal inertia and measurement uncertainty, leading to potential dynamic overheating and thermal failure due to delayed reaction times.
Innovation Solution
A circuit arrangement and method that alternates a power semiconductor switch between on and off states, using a current source to inject a DC current through the gate diode and measure voltage between the gate and source/drain terminals to directly determine the absolute temperature of the semiconductor switch, independent of channel current and thermal mass, leveraging the temperature-dependent I-V characteristic of the gate-source junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NTC temperature sensors are arranged on a carrier plate or heat sink, then the temperature monitoring circuit can measure temperature, but the thermal capacity and thermal behavior cause measurement delay and reduce reaction rate
Solution Approach 1:
The invention extracts the temperature sensing function from the carrier plate/heat sink environment and relocates it directly to the semiconductor switching element by utilizing the gate-source junction's inherent temperature-dependent electrical characteristics. This eliminates the thermal mass of the carrier plate from the measurement path, achieving direct temperature sensing at the source of heat generation without thermal lag.
Solution Approach 2:
The gate-source junction voltage serves as an intermediary parameter that directly reflects the temperature of the semiconductor switching element. By measuring the voltage across the gate-source junction at a known gate current, the system obtains a temperature proxy that is immediately correlated with the actual device temperature, bypassing the need for separate thermal sensors and their associated thermal masses.
2Reliability
If temperature sensors are placed on the carrier plate, then temperature monitoring is enabled, but thermal inertia causes dynamic overheating and thermal failure
Solution Approach 1:
The system performs preliminary temperature assessment continuously by monitoring the gate-source voltage at each switching cycle. This allows the control circuit to detect temperature rise trends before they lead to dangerous overheating conditions, enabling preventive action to be taken in advance rather than reacting after thermal failure has occurred.
Solution Approach 2:
The invention implements a feedback mechanism where the measured gate-source voltage (which correlates with temperature) is fed back to the control circuit, which then adjusts the switching duty cycle or frequency to maintain safe operating temperatures. This closed-loop control continuously adapts to changing thermal conditions, ensuring reliable operation even under varying load 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
Enables precise, immediate, and dynamic temperature measurement of the semiconductor switch, allowing for fast and accurate control and preventing overheating, as the measurement is taken directly at the switch rather than at the heat sink or base plate, reducing thermal lag and false values.
Implementation Method 1
The invention uses the temperature dependence of this junction's I-V characteristic.
Data Source
Figure 1~2
AI summary
Circuit arrangement for controlling a power semiconductor switch, the switch comprising a gate terminal, a source terminal and a drain terminal with a conduction channel being formed between the source and drain terminals, the circuit arrangement comprising: - means for generating a control signal by which the semiconductor switch is alternated between a turned-on state and a turned-off state; - a current source for generating a current into the gate terminal; - an evaluation unit arranged to: -- measure the voltage between the gate terminal and one of the source terminal and drain terminal while the semiconductor switch is in the turned-on state, -- determine from the measured voltage and the current from the current source the absolute temperature of the semiconductor switch.