Combined Isolator Power Switch Voltage Domain Segmentation
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Solution Overview
Problem
High voltage switches face challenges in preventing hazardous voltages from propagating along the control path, and existing semiconductor devices have limitations in current gain and switching speed due to large gate capacitance and high power dissipation.
Innovation Solution
A combined isolator and power switch is provided in a single chip-scale package, featuring a transformer-based isolator and a bipolar transistor in series with a field effect transistor, where the field effect transistor limits the voltage across the bipolar transistor, allowing for higher gain and reduced gate capacitance, enabling efficient signal processing and immunity to electrical noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor power switch is used in high voltage domains, then reliability and speed are improved, but hazardous voltages can propagate along the control path
Solution Approach 1:
The device is segmented into distinct voltage domains: a low voltage control domain and a high voltage power domain, separated by an isolator. This segmentation allows the control circuitry to operate at safe low voltages while the power switch handles high voltages, preventing hazardous voltage propagation along the control path.
Solution Approach 2:
An isolator acts as an intermediary between the low voltage control domain and the high voltage power domain. The isolator transfers control signals from the low voltage side to the high voltage side while maintaining electrical isolation, thereby preventing hazardous voltages from reaching the control path while still enabling reliable switching.
2Strength
If a bipolar transistor is used for high voltage switching, then breakdown voltage capability is improved, but current gain is limited
Solution Approach 1:
The invention merges a bipolar transistor and a field effect transistor into a single integrated device. The bipolar transistor provides the necessary high breakdown voltage capability, while the field effect transistor contributes high current gain. This combination allows the device to simultaneously achieve both high voltage handling and high current amplification capabilities.
3Strength
If a field effect transistor has large gate capacitance, then voltage blocking capability is improved, but switching speed decreases and power dissipation increases
Solution Approach 1:
The voltage blocking function is segmented between two transistors: the field effect transistor handles the voltage blocking capability, and the bipolar transistor handles the current amplification and switching. This segmentation allows the FET to be optimized for voltage blocking without being penalized by excessive gate capacitance effects on switching speed, as the bipolar transistor compensates for the switching action.
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 enhances the reliability and speed of high voltage switching by reducing gate current and power dissipation, allowing for faster switching and improved immunity to electrical noise, while maintaining high breakdown voltage capabilities.
Implementation Method 1
the isolator is a transformer based isolator, where the coils of the transformer are formed on a substrate
Data Source
AI summary
A combined isolator and power switch is disclosed. Such devices are useful in isolating low voltage components such as control compilers from motors or generators working at high voltages. The combined isolator and power switch includes circuits to transfer internal power from its low voltage side to the switch driver circuits on the high voltage side. The combined isolator and switch is compact and easy to use.