Power Transistor Driver Isolation Circuit for Negative Voltage Clamping
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Solution Overview
Problem
Existing driving circuits for N-type power transistors require high breakdown voltage capabilities, leading to increased fabrication costs due to the need for internal circuits to handle voltage fluctuations between VIN and −100V.
Innovation Solution
Incorporation of a negative voltage isolation circuit with an isolation device that clamps the voltage 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
1Reliability
If the driving circuit is designed to support voltage ranging from input voltage to -100V, then the N-type power transistor can be driven properly, but the breakdown voltage requirement increases fabrication cost
Solution Approach 1:
The circuit is divided into two functional segments: a high-voltage segment (output pin handling -100V) and a low-voltage segment (isolation pin handled by isolation device). The isolation device segregates the voltage ranges, allowing different breakdown voltage requirements for different parts of the circuit.
Solution Approach 2:
The isolation device acts as an intermediary between the high-voltage output pin and the low-voltage internal circuits. It mediates the voltage transition by clamping the isolation pin voltage when the output pin voltage drops below the isolation voltage, preventing the -100V from propagating to voltage-sensitive internal circuits.
2Ease of operation
If the bootstrap capacitor is coupled between output pin and bootstrap pin, then the driving signal can be level shifted, but the voltage at bootstrap pin follows the output pin to -100V increasing breakdown voltage requirement
Solution Approach 1:
The voltage following function is segmented: the bootstrap capacitor maintains coupling for level shifting during normal operation, but the isolation device creates a voltage boundary that segments the -100V excursion from the bootstrap pin, allowing level shifting without exposing the bootstrap pin to dangerous voltages.
Solution Approach 2:
The isolation device performs preliminary voltage clamping action before the -100V can propagate through the bootstrap capacitor to the bootstrap pin. By clamping the isolation pin at a preset voltage when output pin voltage drops, it prevents the harmful voltage excursion from occurring at the bootstrap pin in the first place.
3Adaptability or versatility
If internal circuits are designed to work with voltage from VIN to -100V, then the circuit can handle full voltage range, but the breakdown voltage must be greater than VIN+100V
Solution Approach 1:
The voltage handling requirement is segmented between different pins: the output pin handles the full voltage range including -100V, while the isolation pin and connected internal circuits only need to handle voltages down to the clamped preset voltage. This segmentation allows internal circuits to have lower breakdown voltage specifications.
Solution Approach 2:
The isolation device serves as an intermediary that protects internal circuits from the full voltage range. It allows the output pin to adapt to the full voltage range while mediating the voltage presented to internal circuits, reducing their adaptability requirements and breakdown voltage specifications.
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 allows for the fabrication of driving circuits with lower breakdown voltage requirements, thereby reducing production costs while maintaining circuit functionality.
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.