Power Switch Junction Temperature Sensing via Gate Resistance
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Solution Overview
Problem
In high-density power converter or inverter applications, determining the instantaneous chip or junction temperature of new power switch technologies like silicon carbide (SiC) or gallium nitride (GaN) is challenging due to size, cost, and measurement propagation delay issues with external temperature sensors.
Innovation Solution
A method and circuit for determining the junction temperature of a power switch by applying currents to its control node while in a steady-state region, measuring the voltage drops across the internal control node resistance, and outputting a continuous temperature measurement signal, using a current source and calibration circuit to calculate the junction temperature based on the voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external temperature sensors are used for temperature measurement, then temperature monitoring capability is provided, but size, cost, and measurement propagation delay increase
Solution Approach 1:
The power switch device measures its own junction temperature using its existing internal gate resistance as the sensing element. The gate resistance naturally varies with temperature, and by applying test currents and measuring voltage drops across this internal resistance, the device performs self-diagnosis without requiring external temperature sensors, thereby eliminating the need for additional components while maintaining measurement capability
Solution Approach 2:
The invention exploits the temperature-dependent parameter change of the internal gate resistance. As temperature varies, the gate resistance value changes predictably. By measuring the voltage drop across this resistance under known test current conditions, the system converts a physical parameter change (resistance with temperature) into a measurable electrical signal that indicates junction temperature
2Measurement precision
If currents are applied to control node for temperature measurement, then continuous temperature measurement is achieved, but voltage drops across control node resistance must be measured accurately
Solution Approach 1:
The system applies test currents to the gate in periodic pulses during steady-state regions of the power switch operation. These periodic current applications allow for discrete measurement opportunities without continuous interference, enabling accurate voltage drop measurements across the gate resistance at specific moments when the switch is in a stable state
Solution Approach 2:
The invention uses the internal gate resistance itself as an intermediary element that converts temperature information into measurable voltage signals. By measuring the voltage drop across this intermediary resistance under controlled test currents, the system indirectly measures temperature without requiring direct thermal contact or additional sensing components
3Measurement precision
If measurement is performed during steady-state region, then measurement accuracy is ensured, but measurement opportunities are limited to specific operating conditions
Solution Approach 1:
The measurement system dynamically adapts to the operating conditions of the power switch by performing measurements during steady-state regions. The system recognizes when the switch is in a stable operating state and schedules measurements accordingly, optimizing the balance between measurement accuracy and measurement frequency based on real-time operational dynamics
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 approach provides accurate and continuous temperature measurement of power switches, ensuring reliable temperature monitoring and fast over-temperature protection without the limitations of external sensors, enhancing measurement accuracy and reducing costs.
Implementation Method 1
the internal gate resistance can be used to determine a chip temperature
Data Source
AI summary
Techniques for determining a temperature measurement of a junction of a power switch are described. A current can be applied to a control node, e.g., gate terminal, of the power switch, such as a field-effect transistor (FET) or an insulated-gate bipolar transistor (IGBT), while the power switch is in a steady-state region in which a gate-to-source voltage (e.g., FET) or a gate-to-emitter voltage (e.g., IGBT) of the power switch is constant. While in the steady-state region, the temperature measurements can be performed, thereby ensuring accuracy of the measurement.