Negative Voltage Isolation Circuit for Low-Breakdown Gate Drivers
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Solution Overview
Problem
The high breakdown voltage requirement in driving circuits for N-type power transistors increases fabrication costs due to the need for internal circuits to support voltages ranging from the input voltage to negative 100V.
Innovation Solution
A negative voltage isolation circuit is introduced between the isolation pin and the output pin, where the voltage at the isolation pin is clamped at a preset value between -2V and -0.2V when the output pin voltage is less than the isolation voltage, reducing the breakdown voltage requirement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the driving circuit is designed to handle voltage fluctuations between VIN and −100V, then the circuit can drive the N-type power transistor, but the breakdown voltage requirement increases to greater than VIN+100V
Solution Approach 1:
The patent divides the voltage handling function into two separate parts: the output pin handles the full voltage swing from VIN to −100V, while the bootstrap pin voltage is segmented and limited to a smaller range through the negative voltage isolation circuit. This segmentation allows different parts of the circuit to have different breakdown voltage requirements, with internal circuits only needing to withstand VIN rather than VIN+100V.
Solution Approach 2:
The negative voltage isolation circuit acts as an intermediary between the output pin and the bootstrap pin. It isolates the bootstrap pin from the full voltage swing at the output pin, allowing the bootstrap pin to follow only the positive voltage portion while blocking the negative voltage swing. This intermediary structure protects internal circuits from high breakdown voltage requirements.
2Ease of operation
If the bootstrap capacitor is coupled between the output pin and bootstrap pin to level shift the driving signal, then the driving signal is properly generated, but the voltage at the bootstrap pin follows the output pin voltage to −100V
Solution Approach 1:
The patent extracts the negative voltage component from the bootstrap pin voltage by introducing the negative voltage isolation circuit. The bootstrap capacitor maintains its level-shifting function, but the bootstrap pin voltage is taken out from following the full output pin swing and is instead limited to a safer voltage range, separating the voltage following function from the negative voltage swing.
3Reliability
If internal circuits are designed with breakdown voltage greater than VIN+100V, then the circuit can handle voltage fluctuations, but the fabrication cost increases
Solution Approach 1:
The patent introduces a dedicated negative voltage isolation circuit component that absorbs the stress of high voltage fluctuations. This specialized component protects the more expensive internal circuits from needing high breakdown voltage ratings, effectively using a simpler/isolated component to protect the core circuitry, thereby reducing overall fabrication costs.
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 solution allows for the fabrication of driving circuits with lower breakdown voltage requirements, thereby reducing the overall cost and maintaining reliable operation.
Implementation Method 1
when the voltage at the output pin is less than the isolation voltage, the voltage at the isolation pin is clamped at a preset voltage value, the preset voltage value is in a range from −2V to −0.2V
Data Source
AI summary
A driving circuit for a power transistor. The driving circuit has a control pin to receive a control signal, a driving pin to provide a driving signal to control the power transistor, the driving signal is generated based on the control signal. The driving circuit also has a negative voltage isolation circuit connected between an isolation pin and an output pin, when the voltage at the output pin is greater than an isolation voltage, the voltage at the isolation pin is equal to the voltage at the output pin, and when the voltage at the output pin is less than the isolation voltage, the voltage at the isolation pin is clamped at a preset voltage value, the preset voltage value is in a range from −2V to −0.2V.