Semiconductor Overvoltage Protection Circuit with Temperature-Dependent Gate Discharge
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Solution Overview
Problem
Existing overvoltage protection circuits in semiconductor devices fail to effectively manage voltage surges caused by back electromotive forces from inductance loads, leading to potential transistor breakdown and thermal stress due to delayed turn-off times.
Innovation Solution
A semiconductor device with a voltage control circuit and discharge switches that control the gate-source voltage of an output transistor, using zener diodes and transistors to limit voltage and facilitate fast discharge, thereby preventing transistor breakdown and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional overvoltage protection circuit is used, then voltage surges are limited, but the output transistor turn-off time is delayed causing thermal stress
Solution Approach 1:
The gate discharge circuit dynamically adjusts the turn-off timing based on temperature conditions. When the output transistor temperature exceeds a predetermined threshold, the discharge circuit activates to accelerate gate discharge and enable faster turn-off, preventing thermal stress while maintaining normal operation timing under standard conditions
Solution Approach 2:
The temperature sensor circuit continuously monitors the output transistor temperature and provides feedback to the gate discharge circuit. This feedback mechanism enables the system to detect thermal conditions and automatically adjust the gate discharge timing to prevent both thermal stress and voltage breakdown
2Loss of time
If the gate discharge is accelerated to prevent thermal stress, then turn-off time is reduced, but voltage surges may cause transistor breakdown
Solution Approach 1:
The gate discharge circuit operates in two dynamic modes: normal mode for standard operation and accelerated discharge mode for thermal protection. The circuit transitions between these modes based on temperature feedback, accelerating discharge only when thermal stress is detected rather than continuously, thus preventing breakdown while reducing turn-off time when needed
Solution Approach 2:
The temperature sensor circuit continuously monitors transistor temperature in advance to detect thermal stress conditions before they cause damage. This preliminary detection allows the gate discharge circuit to prepare and execute accelerated discharge at the optimal moment, preventing both thermal stress and voltage breakdown
3Reliability
If voltage control circuit is activated to limit voltage surges, then transistor breakdown is prevented, but circuit complexity increases
Solution Approach 1:
The gate discharge circuit serves multiple functions: it enables fast turn-off to prevent thermal stress, limits voltage surges to prevent breakdown, and operates automatically based on temperature feedback. By combining these protection functions into a single multi-functional circuit rather than separate circuits, the overall device complexity is reduced while maintaining comprehensive protection
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 effectively limits voltage surges and enables fast turn-off of the output transistor, preventing breakdown and reducing thermal stress, even under load anomalies.
Implementation Method 1
The voltage control circuit SB has a first zener diode Z1, a second zener diode Z2, a diode D1, and a second transistor T2. The first zener diode Z1 and second zener diode Z2 are series-connected to each other. The two zener diodes Z1 and Z2 are connected in a reverse direction between the drain and the gate of the first transistor T1.
Implementation Method 2
A gate discharge circuit SC has a third transistor T3. A source of the third transistor T3 is connected to the second power supply GND through the second terminal K2. A drain of the third transistor T3 is connected to the gate of the first transistor T1.
Data Source
AI summary
A semiconductor device includes an output transistor which controls a power supply to a load according to a control voltage applied to a gate thereof, a voltage control circuit coupled between the gate and a drain of the output transistor, the voltage control circuit having a conduction state controlled according to a potential difference between a source and the drain of the output transistor, and a voltage control detection circuit which outputs a voltage control detection signal on a basis of the conduction state of the voltage control circuit. A first discharge switch is connected between the gate and the source of the output transistor, an on-off state of the first discharge switch being controlled according to the voltage control detection signal, a second discharge switch is series-connected to the first discharge switch between the gate and the source of the output transistor, an on-off state of the second discharge switch being controlled according to a temperature condition of the output transistor, and a third discharge switch is connected in parallel with the first and second discharge switches.