Series-Connected FET Switching Circuit for High-Voltage Control
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Solution Overview
Problem
Existing switching circuits that use mechanical relays for high-voltage switching are slow compared to FETs, making them unsuitable for applications requiring high-speed voltage switching beyond the withstand voltage of FETs.
Innovation Solution
A switching circuit design that includes serially connected switching devices and corresponding control circuits, allowing for synchronized opening and short-circuiting between terminals, using high-voltage and low-voltage side switching circuits with control signals to manage voltage distribution and prevent overvoltage, enabling high-speed switching with devices having a withstand voltage lower than the applied voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If FET is used for switching, then switching speed is improved, but withstand voltage deteriorates
Solution Approach 1:
The patent divides the high-voltage switching task into multiple segments by connecting multiple FETs in series. Each FET handles a portion of the total voltage, allowing the system to achieve high withstand voltage while maintaining fast switching speeds characteristic of FETs. The control circuits independently manage each FET's switching state to coordinate their operation.
Solution Approach 2:
The patent introduces control circuits as intermediary components between the control signal and the FETs. These control circuits generate appropriate control voltages for each FET, enabling synchronized switching operation and ensuring that voltage distribution across the series-connected FETs remains balanced during switching transitions.
2Strength
If mechanical relay is used for switching, then withstand voltage is improved, but switching speed deteriorates
Solution Approach 1:
The patent replaces the mechanical relay system with an electronic switching system using multiple FETs connected in series. This substitution eliminates the mechanical moving parts that limit switching speed, while the series configuration of FETs provides the necessary high withstand voltage capability through proper voltage distribution and control.
3Strength
If multiple switching devices are connected in series, then withstand voltage is improved, but device complexity increases
Solution Approach 1:
The patent designs the control circuits to perform multiple functions: generating control voltages for individual FETs, monitoring voltage distribution across the series connection, and coordinating switching operations. This multi-functionality reduces the need for additional separate components and simplifies the overall system architecture despite using multiple switching devices.
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
Enables high-speed switching of voltages exceeding 2000V using switching devices with a withstand voltage below 1000V, effectively addressing the speed limitations of mechanical relays while maintaining reliability and efficiency.
Implementation Method 1
A switching circuit using such a FET can switch between two terminals, into which a voltage of several hundred volts is injected, at high speed
Data Source
AI summary
A signal output device that outputs an output signal according to an input signal expressing a logical value that includes a high-voltage side switching circuit between a first terminal and a second terminal in accordance with a first control signal. The device includes a low-voltage side switching circuit between a first and second terminal for outputting a low-voltage side reference voltage in accordance with a second control signal and a control section. The high-voltage and low-voltage side switching circuits include a plurality of switching devices serially connected between the first terminal and the second terminal and each of which is opened in accordance with a provided control voltage. The control circuit opens the plurality of switching devices substantially in synchronization with each other, where a voltage inputted to the first terminal is outputted from the second terminal by short-circuiting between the first terminal and the second terminal.