Amplifier Thermal Shutdown Circuit Using a Self-Biased Sensor Transistor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing thermal protection circuitries for thermally stressed components like power amplifiers require complex sensor calibration, which is burdensome for manufacturers and users, and often involve complicated circuitry that is not optimized for thermal performance, especially during high power and high temperature operations.
Innovation Solution
An integrated circuit amplifier with a power transistor and thermal protection circuitry that includes a sensor transistor with a sensor bias circuit generating a temperature set point where the sensor output voltage drops by at least 50% above that point, triggering shutdown circuitry to reduce the bias signal to the power transistor, thus preventing thermal damage without the need for sensor calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complicated sensor calibration circuitry is used for thermal protection, then thermal protection accuracy is improved, but device complexity and manufacturing burden increase
Solution Approach 1:
The sensor transistor automatically generates a temperature-dependent output voltage that inherently indicates thermal conditions without requiring external calibration circuitry. The sensor bias circuitry uses the transistor's natural Vbe temperature characteristics to provide self-calibrating thermal protection, eliminating the need for complicated calibration mechanisms.
Solution Approach 2:
The patent exploits the temperature-dependent change in the sensor transistor's output voltage parameter. As temperature increases, the Vbe voltage of the sensor transistor changes predictably, and this parameter change is directly utilized to trigger thermal protection shutdown without requiring additional calibration components or procedures.
2Measurement precision
If sensor calibration procedures are implemented, then thermal protection precision is improved, but ease of operation and manufacturing burden worsen
Solution Approach 1:
The sensor transistor inherently provides temperature-proportional output voltage that requires no manual calibration. The circuit automatically adapts to temperature changes through the transistor's natural electrical characteristics, eliminating calibration procedures for both manufacturers and end users while maintaining precise temperature detection.
Solution Approach 2:
The sensor transistor effectively creates an electrical copy of the thermal condition through its Vbe voltage, which naturally mirrors temperature changes. This electrical representation can be directly used for thermal protection decisions without requiring calibration against physical temperature references.
3Productivity
If high power operation is enabled, then productivity and output power are improved, but thermal damage risk increases
Solution Approach 1:
The thermal protection circuitry continuously monitors the sensor transistor's output voltage, which reflects real-time temperature conditions. When the voltage indicates excessive temperature during high power operation, the shutdown circuitry automatically reduces the bias signal to the power transistor, providing negative feedback that prevents thermal damage while allowing sustained high power operation within safe limits.
Solution Approach 2:
The thermal protection circuitry is pre-configured with shutdown thresholds based on the sensor transistor's temperature-voltage characteristics. Before thermal damage can occur, the circuit automatically triggers shutdown at predetermined safe temperature margins, cushioning against potential harm from high power operation.
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 solution provides effective thermal protection for power amplifiers by minimizing current consumption and eliminating the need for sensor calibration, ensuring reliable operation across varying temperature ranges with minimal overhead, while maintaining simplicity in circuit design.
Implementation Method 1
the sensor bias circuitry is configured to generate a temperature set point at which a sensor output voltage at the sensor output terminal drops at least 50% when the temperature of the sensor transistor is above the temperature set point
Data Source
AI summary
Disclosed is an integrated circuit amplifier having a power transistor with a signal/bias input terminal, a first high current terminal, and a second high current terminal, and thermal protection circuitry with a sensor transistor having a sensor control terminal, a sensor output terminal, and a sensor current terminal coupled to a fixed voltage node. Sensor bias circuitry includes a sensor bias terminal coupled to the sensor control terminal, wherein the sensor bias circuitry is configured to generate a temperature set point at which a sensor output voltage at the sensor output terminal drops at least 50% when the temperature of the sensor transistor is above the temperature set point. Shutdown circuitry coupled between the sensor output terminal and the signal/bias input terminal is configured to reduce a bias signal at the signal/bias terminal in response to the at least 50% drop in sensor output voltage.