Gate Driver Circuit for Normally-On N-Channel FET Power Loss Control
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Solution Overview
Problem
Existing driver transistors in self-conducting n-channel output stage field effect transistors experience high power dissipation due to voltage oscillations at the source electrode, leading to inefficient power amplification in push-pull circuits, particularly in high-side applications where the voltage across the resistor causes significant power loss.
Innovation Solution
The proposed device includes a driver transistor configuration where the resistor is connected between the first and second nodes, allowing the supply voltage to be present at the control signal output, and utilizing multiple negative voltage sources to control the driver transistors, reducing power loss by determining the voltage drop across the resistor based on the control signal output voltage, and using a normally on field effect transistor with a resistor connected between nodes to minimize power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driver transistor is used in a high-side application to control the output stage transistor, then the output stage transistor can be reliably blocked, but the voltage oscillation at the source electrode causes high power dissipation in the driver transistor
Solution Approach 1:
The driver circuit is segmented into two separate driver transistors: a first driver transistor for controlling the output stage transistor and a second driver transistor for managing the voltage level at the control signal output. This segmentation allows each transistor to operate in an optimized configuration, reducing overall power dissipation while maintaining reliable blocking capability
Solution Approach 2:
A second driver transistor is introduced as an intermediary component between the control signal input and the first driver transistor. This intermediary manages the voltage levels and reduces the power dissipation burden on the first driver transistor by handling the voltage oscillation at the control signal output through a resistor connection
2Reliability
If a resistor is connected between the second node and positive voltage source to control the driver transistor, then the driver transistor can be blocked, but high voltage across the resistor causes significant power dissipation
Solution Approach 1:
The second driver transistor acts as an intermediary that manages the voltage at the control signal output. By connecting the resistor between the first and second nodes rather than between the second node and positive voltage source, the resistor only experiences the voltage difference between nodes, significantly reducing power dissipation while maintaining effective blocking capability through the coordinated action of both driver transistors
Data Source
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AI summary
The invention relates to a device (100) for controlling a self-conducting n-channel output stage field effect transistor (V1), comprising a control signal input (110), a control signal output (120) for connection to a gate electrode (V1G) of the output stage field effect transistor (V1), a first node (N1), which is connected to the control signal output (120), a second node (N2) and first transistor (V4). A source electrode (V4S) of the first transistor (V4) is connected to the first node (N1), a gate electrode (V4G) of the first transistor (V4) is connected to the second node (N2) and a drain electrode (V4D) of the first transistor (V4) is connected either to the source electrode of the output stage field effect transistor (V1) or to a supply voltage (+Vdd). A resistor (R1), with one end thereof, is connected to the second node (N2). The device (100) is characterised in that the resistor (R1), with the other end thereof, is connected to the first node (N1). Use of the first transistor (V4) can thus ensure that the supply voltage (Vdd) is present on the control signal output when a low-level signal is present on the control signal input (110).