Inductive Load Driver Gate Boost for MOSFET Clamp Resistance
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Solution Overview
Problem
Conventional semiconductor devices for driving inductive loads face challenges in managing back electromotive force and energy handling due to variations in threshold voltages of minute MOSFETs, leading to reduced clamp resistance and potential element destruction.
Innovation Solution
A semiconductor device with a voltage detection circuit and a drive circuit that apply specific threshold voltages to the output-stage switch to ensure all minute MOSFETs are turned on, increasing clamp resistance and reliable energy handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional drive circuit is used to control the output-stage switch, then the device structure remains simple, but the clamp resistance decreases and element destruction may occur due to threshold voltage variations in minute MOSFETs
Solution Approach 1:
The drive circuit applies a preliminary high-voltage signal to the gate of the output-stage switch before the main switching operation. This preliminary action ensures that all minute MOSFETs are fully turned on, compensating for threshold voltage variations and preventing clamp resistance degradation, thereby resolving the reliability issue without requiring complex external circuitry
Solution Approach 2:
The drive circuit incorporates a feedback mechanism that monitors the switching state of the output-stage switch and dynamically adjusts the gate voltage. When threshold voltage variations cause incomplete turn-on of MOSFETs, the feedback loop detects this condition and applies additional voltage to ensure full conduction, maintaining high clamp resistance while keeping the circuit structure relatively simple
2Reliability
If the gate voltage is kept at a standard level, then the drive circuit remains simple, but energy handling capability deteriorates during overvoltage conditions due to incomplete MOSFET conduction
Solution Approach 1:
The gate voltage is made dynamic rather than static. The drive circuit automatically adjusts the gate voltage level based on real-time operating conditions, particularly during overvoltage events. When back electromotive force exceeds the clamp voltage, the circuit dynamically increases gate voltage to ensure complete MOSFET turn-on, maximizing energy handling capability while maintaining a relatively simple overall structure through adaptive control
3Volume of moving object
If minute MOSFETs are used to reduce device size, then miniaturization is achieved, but threshold voltage variations increase leading to reduced clamp resistance
Solution Approach 1:
The invention changes the voltage parameter applied to the gate of the output-stage switch. By applying a higher than standard gate voltage, the system compensates for threshold voltage variations inherent in miniaturized MOSFETs. This parameter change ensures that despite size reduction and associated manufacturing variations, all MOSFETs remain fully conductive, maintaining high clamp resistance while achieving device miniaturization
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 increases clamp resistance and ensures reliable energy handling by forcing a higher threshold voltage during overvoltage conditions, preventing element destruction and improving operational efficiency.
Implementation Method 1
back electromotive force generated in the inductive load at a turn-off time that follows a turn-on of the output-stage switch
Implementation Method 2
a drive circuit that applies a drive signal having a first threshold voltage to a gate of the output-stage switch to turn on the output-stage switch
Implementation Method 3
a voltage application circuit that applies a voltage signal having a second threshold voltage higher than the first threshold voltage to the gate of the output-stage switch, responsive to the overvoltage being higher than or equal to the clamp voltage
Data Source
AI summary
A semiconductor device for driving an inductive load. The semiconductor device includes an output-stage switch connected to the inductive load for operating the inductive load; a voltage detection circuit configured to output a detection signal responsive to an overvoltage being higher than or equal to a clamp voltage; a drive circuit configured to apply a drive signal having a first threshold voltage to a gate of the output-stage switch, responsive to the overvoltage being lower than the clamp voltage, to turn on the output-stage switch; and a voltage application circuit configured to apply a voltage signal having a second threshold voltage higher than the first threshold voltage to the gate of the output-stage switch, responsive to the overvoltage being higher than or equal to the clamp voltage and upon receiving the detection signal from the voltage detection circuit, to turn on the output-stage switch.