High-Side MOSFET Driver Circuitry Against dv/dt Displacement Current
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Solution Overview
Problem
In high-side driver circuitry of high withstand voltage MOSFETs, the displacement current flowing through low-voltage circuit elements during transitions of high-side and low-side MOSFETs can cause malfunctions due to the dv/dt applied to substrate capacitance.
Innovation Solution
The driver circuitry employs a configuration with multiple transistors and inverters, using elements with withstand voltage performance suitable for both high and low voltages, to manage the drive signals and reduce the impact of displacement currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If low-voltage circuit elements are used in high-side driver circuitry to miniaturize the process, then chip size is reduced and lower voltage power supply configurations are enabled, but displacement current flows through the low-voltage elements during MOSFET transitions causing malfunctions
Solution Approach 1:
The driver circuitry is segmented into high-voltage circuit elements (for driving the MOSFET) and low-voltage circuit elements (for control functions), with each segment optimized for its specific voltage requirement. This allows the use of low-voltage elements to reduce chip size while isolating them from harmful displacement currents through proper circuit design.
Solution Approach 2:
A bootstrap capacitor and diode are introduced as intermediary elements between the high-voltage switching node and the low-voltage control circuitry. These intermediaries isolate the low-voltage elements from direct exposure to displacement currents while still enabling proper driving of the high-voltage MOSFET gate.
2Power
If high-voltage process is used for driver circuitry to drive 15V MOSFET, then the MOSFET can be driven at required voltage, but the process size increases and miniaturization becomes difficult
Solution Approach 1:
Different parts of the driver circuitry are designed with different voltage ratings matched to their specific functions. High-voltage circuit elements are used only where required for MOSFET driving, while low-voltage elements are used for control functions, allowing each part to be optimized for its local requirements rather than the entire circuit being designed for high voltage.
Solution Approach 2:
The circuit design transitions from a uniform high-voltage approach to a mixed-voltage approach, changing the voltage parameter locally across different circuit elements. This allows the driver circuitry to operate at high voltage when needed while using low-voltage elements elsewhere to reduce overall process size.
3Volume of moving object
If low-voltage power supply (about 5V) is used for control circuit based on high-side bootstrap voltage, then chip size is minimized, but displacement current from dv/dt applied to substrate capacitance causes malfunction
Solution Approach 1:
The bootstrap capacitor acts as an intermediary energy storage element that decouples the high-voltage switching node from the low-voltage control circuitry. This intermediary absorbs the displacement current effects while maintaining stable low-voltage operation of the control elements.
Solution Approach 2:
The bootstrap diode and capacitor are configured to provide beforehand cushioning against displacement current effects by pre-charging the bootstrap capacitor during the low-side MOSFET on-time, thereby cushioning the low-voltage control elements from voltage spikes and displacement currents during the subsequent high-side switching event.
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 configuration allows for appropriate turning on and off of high withstand voltage elements, reducing the influence of displacement currents and enabling the use of low withstand voltage elements, which can minimize chip size and allow for lower voltage power supply configurations.
Implementation Method 1
an output voltage rises from 0V to the power supply on the positive side, dv/dt is applied to the substrate capacitance in the high-side region, and a displacement current flows
Data Source
AI summary
A driver circuitry includes first-fifth inverters which have lower withstand voltage, and first-sixth transistors which have higher withstand voltage. In the first transistor, a first voltage is applied to a first end, and a second end is connected to the high withstand voltage element. The second transistor is connected to the first transistor. The second inverter is connected to the first inverter and the first transistor. The third inverter is connected to the first inverter. The third transistor is connected to the second inverter. The fourth transistor is connected to the third transistor. The fifth transistor is connected to the third inverter. The sixth transistor is connected to the fifth transistor. The fourth inverter is connected to the sixth transistor and the second transistor. The fifth inverter is connected to the fourth transistor, the fourth inverter, and the fourth inverter.